記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

Eddy current sensor signals induced by out-of-plane waviness in carbon fiber composites were investigated. Cross-ply laminates with artificial out-of-plane waviness were fabricated. The samples were scanned using an eddy current probe to measure the in-phase and quadrature phase components of the pickup coil voltage with respect to the excitation. A two-dimensional map of the pickup coil voltage amplitude indicated that it was difficult to distinguish signal changes in the waviness zone from signal changes caused by inhomogeneous electrical properties. By selecting the optimum image phase and probe rotation angle, the signal-to-noise ratio was improved greatly and the waviness was visualized without being masked by signal changes in the non-defective zone. Finite element analysis of eddy current testing was performed for various waviness amplitudes and wavelengths to obtain the relationship between the waviness dimension and the pickup coil voltage. The finite element analysis validated the enhanced sensitivity to waviness observed experimentally.

DOI： 10.1016/j.compositesa.2022.107173

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記述言語：英語   掲載種別：論文集(書籍)内論文  

The high-velocity impact of foreign objects such as small stones will produce complex damage in composite laminates, which will severely degrade residual strength. This chapter first describes high-velocity impact tests for CFRP laminates and then observes damage states caused by near-perforation impacts. Extensive delamination and fibre breaks as well as matrix cracks appeared regardless of the stacking sequence. This study also quantitatively evaluates the influence of the stacking sequence and the material system (i.e. the presence or absence of toughened interlayers) on the damage area. Finally, the mechanisms of high-velocity impact damage in CFRP laminates are discussed based on the observations.

DOI： 10.1016/B978-0-12-823979-7.00007-7

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SAGE Publications  

In industrial processes, piercing and trimming are essential because composite structures are usually manufactured in a near-net shape to reduce machining operations. Punching and shear cutting using out-of-plane shear loading are expected to increase productivity. Nevertheless, little is known about the effects of such operations on polymer-matrix composites. This study presents on the characterization of piercing damage in typical carbon fiber reinforced plastic (CFRP) cross-ply laminates [0°₂/90°₂]_s after punching using quasi-static (QS) and drop-weight impact (DWI) loadings. During QS punching, the upper and lower ply interfaces delaminate due to the high shear stress to cut fibers and gradual shear deformation in the middle ply; however, during DWI punching at a low impact velocity, delamination of the lower ply interface can be reduced due to the localization of shear deformation, as compared to that in QS punching. Finally, the damage accumulation process during DWI punching is discussed.

DOI： 10.1177/00219983211031627

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その他リンク： http://journals.sagepub.com/doi/full-xml/10.1177/00219983211031627

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

Elastic metamaterials with inertial amplification mechanisms reinforced by continuous carbon fibers were proposed to achieve lightweight structures with a wide band gap in the low frequency range (< 1 kHz). Finite-element method analysis was performed to investigate the effect of continuous fibers on the specific stiffness and band gap width. The specific stiffness and band gap width can be improved by an appropriate placement of continuous carbon fibers. The dimensions of the proposed structure were optimized to maximize the band gap width. A gap–mid-gap ratio greater than 100% was achieved by optimization. Analytical modeling was performed to predict the lower and upper bound frequencies of the band gap, and its accuracy was verified by a comparison with the finite-element analysis. The optimized structure was fabricated by a three-dimensional printer that can print composites with curvilinear continuous fibers. The frequency-dependent vibration transmissibility of the printed metamaterial structure was measured and compared with frequency response functions obtained from finite-element analysis. The measured attenuation performance of the manufactured structure agreed well with the numerical analysis results.

DOI： 10.1016/j.jsv.2021.116412

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

An eddy-current array-probe method was proposed to visualize delamination occurring within multidirectional carbon fiber-reinforced plastics. First, samples with a near-surface delamination were scanned by a coil array probe comprising a single driver coil and multiple pickup coils, and the detectability of the delamination was evaluated by the signal-to-noise ratio. An appropriate selection of the image phase and the distance between the driver and pickup coils enabled detection of the delamination suppressing the signal variation in the non-defective region. Furthermore, the experimental results suggested that the distance between the driver coil and the most sensitive pickup coil correlated with the delamination size. Second, the array-probe technique was used to detect a delamination located at various depths. The detectability of the delamination was found to be strongly affected by the rotation angle of the array probe. The optimum probe rotation angle depended on the depth of the delamination, indicating that a delamination occurring in deeper regions can be visualized by setting an appropriate probe rotation angle.

DOI： 10.1016/j.compstruct.2021.114537

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

Ceramic balls made of silicon nitride (Si3N4) exhibited excellent mechanical properties are used in high-end components operating at ultra-high speeds, and high and low temperatures. Previously, studies have involved the cyclic mechanical and thermal fatigue tests of ceramic balls under a constant temperature. However, the thermal fatigue characteristics of brittle materials have not been theoretically or experimentally investigated under variable thermal shock loadings to date. Herein, cyclic thermal shock fatigue (CTSF) life characteristics of Si3N4 ceramic balls subjected to single- and two-stage cyclic thermal shock loadings were theoretically and experimentally investigated using a probabilistic model based on slow crack growth concept in conjunction with Weibull distribution. Consequently, the fracture criterion derived from the probabilistic model was related to the linear cumulative damage law (Miner's rule). Thereafter, the predicted CTSF life of the ceramic balls was compared with the experimental results to validate the proposed probabilistic model. Therefore, the proposed model accurately reproduced the experimental results to a certain extent.

DOI： 10.1016/j.engfracmech.2021.107924

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

This paper quantitatively clarifies the effect of the fiber cut angle on the shearing strength of carbon-fiber-reinforced thermoplastic laminates. First, the shearing strength of the unidirectional and cross-ply laminates was measured at various cut angles. Next, two mechanics models, a rule-of-mixture-based model and a failure criterion model, were established to predict the shearing strength of the unidirectional and cross-ply laminates. The rule-of-mixture model explains the effect of the cut angle on the shearing strength of the unidirectional laminate. The failure criterion model predicts the dependence of the cut angle on the shearing strength for both laminates. Finally, finite element analysis was performed to semi-quantitatively evaluate the assistance effect of bending stress. It was revealed that the effective bending stress is almost equivalent to the stress averaged over approximately the one-layer thickness from the surface.

DOI： 10.1016/j.compositesb.2021.108869

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Informa UK Limited  

This study presents an ultrasonic guided wave technique for real-time monitoring of the viscoelastic properties of curing carbon fiber-reinforced plastics (CFRPs) with toughened interlaminar layers. The guided wave propagating in a unidirectional CFRP prepreg was measured. The energy velocity and attenuation of the guided wave were acquired by the Hilbert transform and continuous wavelet transform. The micromechanics of fiber composite and rule of mixtures for a slab model were used to express the material properties of the CFRP as functions of only the complex Young’s modulus of the resin. A transfer matrix method was performed to obtain the relationship between the energy velocity and the resin complex modulus and that between the attenuation and the resin complex modulus. The development of the Young’s modulus during curing was estimated from the measurement results using the relationship obtained in the transfer matrix method. The estimated complex modulus was compared with that measured by a dynamic mechanical analyzer to verify the validity of the proposed method.

DOI： 10.1080/09243046.2020.1812801

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

Eddy current testing methods to estimate the anisotropic electrical conductivity of multidirectional carbon fiber reinforced plastics are proposed in this work. Finite element analysis was performed to investigate the contributions of the three-directional conductivities to the coil impedance. The coil impedance variation was expressed as an approximate function with respect to the anisotropic conductivity using the response surface methodology. Three proposed methods were applied to estimate the conductivity from the measured coil impedance and the estimated conductivities were then compared with the conductivities measured using a four-probe method. Use of the response surface enabled prediction of the lower and upper limits of the conductivity while taking the scatter of the electrical properties in the tested material into consideration. The conductivity range was predicted correctly using the proposed methods. There was a trade-off relationship between the accuracy and the simplicity of these estimation methods.

DOI： 10.1016/j.compositesa.2021.106274

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

A new eddy current testing method for non-contact strain monitoring of continuous carbon fiber-reinforced plastics (CFRPs) was developed. The strain of a CFRP was estimated from a slight change of the fiber orientation measured by eddy current testing. A bidirectional CFRP laminate under off-axis tensile load was scanned by an eddy current probe to obtain the signal change caused by material inhomogeneity. Two-dimensional Fourier transform was applied to the probe signal distribution to identify the fiber orientation of the tested CFRP. The relationship between the fiber orientation and strain was analytically derived using a simple deformation analysis and the classical lamination theory of fiber composites. The strain development predicted by the eddy current method agreed well with that measured by a strain gauge. This method enables non-contact strain monitoring without surface treatment to the tested sample.

DOI： 10.1016/j.measurement.2020.108589

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2020 The Authors On the basis of lamination theory, a quasi-isotropic fiber metal laminate (FML) with a near-zero coefficient of thermal expansion (CTE) and high specific modulus was designed, using pitch-based carbon fiber reinforced plastic (CFRP) prepreg and stainless steel (SST). The SST to CFRP thickness ratio was determined so that the laminates had an exact-zero CTE at room temperature (25 °C). The CTE of a fabricated FML was accurately measured using embedded fiber Bragg grating (FBG) sensors, to verify that the CTE had a near-zero value around room temperature. The temperature dependence of the FML CTE from 20 to 120 °C was investigated via finite element analysis (FEA) taking the temperature-dependent material properties into account. It was demonstrated from the experiment and FEA that the present FML had a near-zero CTE around room temperature (20–45 °C) and a higher Young's modulus and specific modulus compared with other relevant materials.

DOI： 10.1016/j.ijlmm.2020.08.001

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

This study presents locally resonant acoustic metamaterials made of continuous carbon-fiber-reinforced plastics for vibration attenuation. Unit cells were designed such that the attenuation of low-frequency vibration was compatible with high stiffness. The effect of the path and content of carbon fibers on the band gap was numerically investigated through band-structure analysis for periodic cells. We found that the band gap can be widened by an appropriate placement of carbon fibers in the unit cell. Furthermore, the band gap of the carbon-fiber reinforced metastructures was wider than that of the structures without fibers. Metamaterial samples composed of the designed unit cells were fabricated by 3D printing technique of fiber composites. The vibration transmissibility of the samples was measured and compared with the frequency response function computed by finite-element analysis. The frequency ranges with strong attenuation were in good agreement with those observed in the numerical analysis.

DOI： 10.1016/j.compstruct.2020.112949

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Academic Press  

The authors regret that a typographical error was found in Eq. (2). The correct form of the equation is as follows: [Formula presented] The authors would like to apologise for any inconvenience caused.

DOI： 10.1016/j.jsv.2021.116609

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：学校法人 金沢工業大学 材料システム研究所  

This paper presents the seamless monitoring of internal strains, consisting of process-induced strain and machining-induced strain, in a carbon fiber-reinforced plastic (CFRP) cross-ply laminate. The strains during processing and drilling were calculated from the Bragg wavelength shift and the temperature change measured using an embedded FBG (Fiber Bragg Grating) sensor and a thermocouple, respectively. The absolute internal strain was consistently monitored through processing (curing) to machining (drilling) by defining the strain at the gel point to zero. As a result, the drilling-induced strain is separated from the process-induced strain. The exact location of the FBG sensor and the delamination size around a drilled hole were identified using soft X-ray radiography. It was found that the internal strain detected by the FBG sensor was correlated with not only damage size, or a delamination factor, but also its relative position.

DOI： 10.34401/materialssystem.37.0_79

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

© CCM 2020 - 18th European Conference on Composite Materials. All rights reserved. This paper presents in-process monitoring of cure and thermal shrinkage in unidirectional (UD) CF/Epoxy laminates with interlayers. The transverse strain during a cure-process was in-situ measured using an FBG sensor embedded in UD laminates with interlayers (IL) and without interlayers (NIL). From the strain during a hold (high-temperature) stage, the coefficient of cure shrinkage (CCS) in the transverse direction was estimated for both laminates. On the other hand, the coefficient of thermal expansion (CTE) in the transverse direction was calculated from the change in the strain during a cooling stage. The CTEs of both laminates were also measured by thermomechanical analysis for cured samples. The CCS of the IL laminate is lower than that of the NIL laminate while the transverse CTE of the IL laminate is higher than that of the NIL laminate. The CTE of both laminates decreases as the temperature decreases. This temperature dependence of CTE is more prominent in the thickness direction. The above difference of CCS and CTE in both laminates is approximately explained using micromechanical models. However, some discrepancy could be attributed to softening of thermoplastic particles and temperature dependent Young's modulus with large error in the interlayer.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

© Published under licence by IOP Publishing Ltd. This study aims to investigate the effect of impactor on the behaviour of CFRP with toughened interlayers when subjected to low-velocity impact. CFRP with toughened interlayers is different from a conventional CFRP laminate since it enhanced the toughness of CFRP laminate. In this study, CFRP with toughened interlayers laminate was subjected to low velocity impact by using a drop weight testing apparatus developed in the laboratory. Four sizes of impactor head diameter were used with three different masses. The impactor was suspended at a specified height and released for a free fall drop. The impact event was then reproduced numerically. Based on the results, it was observed that the degree of damage was increased as the mass of impactor increased. However, smaller head diameter of impactor produced greater damage. Hence, smaller contact area produces greater local deformation as opposed to larger contact area that generates global deformation. Numerical analysis is also capable to reproduce the impact event.

DOI： 10.1088/1742-6596/1349/1/012095

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

This study presents a simple approach to model unidirectionally arrayed chopped strand (UACS) laminates via the extended finite-element method to represent slits (i.e., fiber cutting lines). This enables the introduction of slits independent of the finite-element mesh and reduces the effort to represent a complex discontinuity pattern when compared to standard modeling using double nodes. The laminated structure was represented by stacking two-dimensional layers, and cohesive elements were inserted into the layer interfaces to predict the extension of delamination. Damage progress in CFRP quasi-isotropic laminates with diagonal continuous slits were analyzed via the present approach, and the effect of the angle between the slit line and fiber direction on the tensile strength was investigated. The predicted strength was in agreement with the reported experiment results within the examined slit angle range. A numerical study revealed that the strength of the UACS laminates was enhanced by a low inclined slit angle.

DOI： 10.1016/j.compstruct.2019.111457

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

An ultrasonic guided wave-based cure monitoring technique is developed to estimate cure-dependent anisotropic viscoelastic properties of carbon fiber reinforced plastics (CFRPs). The guided wave propagating in the transverse direction of a CFRP was measured during a cure process and the energy velocity and attenuation were obtained by signal processing. A micromechanics model and transfer matrix method were used to express the energy velocity and attenuation as functions of only the complex Young's modulus of the resin. The complex Young's modulus of the resin was estimated from the measurement results using response surfaces of the relationship between the energy velocity, attenuation and the resin complex modulus. It was verified that the estimated storage modulus and loss modulus showed reasonable values and behavior. The development of the anisotropic viscoelastic property of CFRPs can be fully determined in real time using this technique.

DOI： 10.1016/j.ultras.2019.105952

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

A numerical modeling of ultrasonic testing (UT) for a carbon fiber reinforced plastic (CFRP) material is presented. Due to the heterogeneity caused by the several unidirectional lamina stacked at different angle, the CFRP shows unique mechanical properties and leads to ultrasonic wave skewing and scattering. In this paper, we present a large-scale finite element (FE) simulation based on the image-based modeling approach. We model the mesoscopic heterogeneity of the CFRP in the numerical discretization by using the voxel of the same size. The determination of the anisotropic elastic stiffness of each lamina is essential to the FE simulation. Here, we estimated the parameters via an inversion method using wavefield visualization data. The parameters were fed into the 3D wave propagation simulations in the laminated CFRPs. The simulation and experimental results showed good agreement with respect to the wave velocity and the spread of the ultrasonic waves. It was found that the mesoscopic modeling and parameterization of the elastic stiffness of the lamina were important for the UT simulation.

DOI： 10.1016/j.compositesb.2019.107018

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

An eddy current testing method is proposed to improve the sensitivity to delamination in carbon fiber reinforced plastics (CFRPs). The distributions of the eddy current density and magnetic field are investigated using finite element method analyses to identify the effect of delamination on the electromagnetic field. The change of the magnetic field induced by delamination is calculated and it is found that a distinct improvement of the sensitivity to delamination can be achieved by optimizing the distance between the tangential driver and pickup coils. Experiments performed for cross-ply CFRP samples verify that the sensitivity of the eddy current sensor can be improved such that the signal change caused by delamination is not masked by the signal changes caused by the electrical conductivity variation in CFRP. Embedded delamination with a length and width of 10 mm are clearly visualized using the proposed eddy current method.

DOI： 10.1016/j.compstruct.2019.111227

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2019 Elsevier B.V. Fast machining is essential for mass production of composite structures, and out-of-plane shearing, also known as die cutting, is appropriate for trimming. Nevertheless, little is known about shearing of polymer-matrix composites. This study was done to investigate the damaging impact of shearing conditions on carbon fiber reinforced plastic (CFRP) laminates. The clearance and temperature affected the damage progress, while the cutting speed in the tested range had negligible effect. In cross-ply laminates, delamination and matrix cracks first appeared in a narrow shearing zone, and with further loading longitudinal plies broke at the dies’ edges. Although delamination occurred only in a narrow shear-stress concentrated zone in the case of a small clearance, it was significant for a large clearance, owing to the local bending deformation. A temperature slightly lower than the glass transition temperature narrowed the delamination area, owing to the increase in the interlaminar fracture toughness as well as insignificant strength degradation of the matrix.

DOI： 10.1016/j.jmatprotec.2019.04.025

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2019 Elsevier B.V. A pulsed laser illuminates a target zone that causes rapid thermoelastic expansion, generating broadband high-frequency ultrasonic wave (photoacoustic wave, PA wave). We developed a PA microscopy (PAM) with a confocal area of laser and ultrasonic wave for applications in nondestructive testing (NDT). The synthetic aperture focusing technique (SAFT) is applied in the PAM for the three-dimensional (3D) imaging of interior flaws. Here, we report proof-of-concept experiments for the NDT of a subsurface flaw in a thin laminar material. Graphical abstract (a) shows a specimen of carbon-fiber-reinforced plastic (CFRP) with an artificial delamination. Here, it should be noted that the group velocity varies directionally due to the strong anisotropy of the CFRP specimen (see Graphical abstract (b)). By considering the group velocity distribution in the SAFT, the shape and location of the subsurface delamination were accurately estimated as shown in Graphical abstract (c). Coating the surface of the CFRP specimen with a light-absorbent material improved the amplitude of the PA wave. This finding showed that the signal-to-noise ratio of the waves scattered from the flaws can be improved.

DOI： 10.1016/j.ultras.2019.05.006

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2019 Wiley Periodicals, Inc. Ultrasonic wave generated by interaction of the material with pulsed lasers is known as photoacoustic (PA) wave. In this study, the PA imaging is applied to the nondestructive testing for carbon fiber reinforced plastic (CFRP). When subsurface flaws are in CFRP, the detection of the flaws is sometimes challenging because the trailing signal from the surface interferes with the scattered signal from the flaws. Here, we developed a PA microscopy (PAM) to reconstruct the location and shape of the subsurface flaws. The PAM employs a confocal arrangement of optical and acoustic lens to maximize the intensity of generated PA waves. To enhance the lateral resolution of the image, we introduced the synthetic aperture focusing technique (SAFT). In the SAFT, it is necessary to consider direction-dependent group velocities due to the strong anisotropy in CFRP. The performance of the PA imaging combined with the SAFT was checked with artificial delaminations in a cross-ply CFRP specimen. It was shown that the PA wave had a wide frequency band and our method offered a high spatial resolution image.

DOI： 10.1002/ecj.12164

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/mej.18-00284

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Formability, as well as strength and stiffness, is important to utilize carbon-fiber-reinforced plastics (CFRPs) in automobiles for weight saving, because their components have complex geometries. However, the microstructure of composites with discontinuous fibers cannot be controlled when using conventional molding compounds, and therefore, enhancing all the properties is difficult. The unidirectionally arrayed chopped strands (UACS), in which a prepreg sheet with unidirectional and continuous reinforcing fibers is cut in a regular manner, are promising to overcome the difficulty. Although a UACS layer is an assembly of many small sheets, the high structural regularity leads to high mechanical properties. Analytical evaluation of UACS laminates is essential to optimize fiber-cutting (slit) pattern and to achieve better performance, but building a complex mesh near the slits is a severe obstacle. This study therefore proposes a simple approach to model the microstructure of UACS laminates and to predict their damage extension. UACS laminates have two key microstructures, namely the stacked layers and the slit pattern, and the layer-wise modeling and the extended finite-element method (XFEM) are adopted for the laminated structure and the discontinuities owing to slits, respectively. Static tensile strength of quasi-isotropic UACS laminates with diagonal continuous slits was predicted and compared with the reported experiment results. The predicted strength agreed well with the experiments, and the tensile strength of the UACS laminates increased with decreasing the inclined slit angle, owing to the less probability of delamination extension from the slits.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

© 2019 The Institute of Electrical Engineers of Japan. Ultrasonic wave generated by interaction of the material with pulsed lasers is known to photoacoustic (PA) wave. In this study, the PA imaging is applied to the nondestructive testing for carbon fiber reinforced plastic (CFRP). When subsurface flaws are in CFRP, the detection of the flaws is sometimes challenging because the trailing signal from the surface interferes with the scattered signal from the flaws. Here we developed a PA microscopy (PAM) to reconstruct the location and the shape of the subsurface flaws. The PAM employs a confocal arrangement of optical and acoustic lens to maximize the intensity of generated PA waves. To enhance the lateral resolution of the image, we introduced the synthetic aperture focusing technique (SAFT). In the SAFT, it is necessary to consider direction-dependent group velocities due to the strong anisotropy in CFRP. The performance of the PA imaging combined with the SAFT was checked with artificial delaminations in a cross-ply CFRP specimen. It was shown that the PA wave had a wide frequency band and our method offered a high spatial resolution image.

DOI： 10.1541/ieejeiss.139.142

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担当区分：筆頭著者,　責任著者   記述言語：日本語  

J-GLOBAL

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語  

© The Authors. The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.

DOI： 10.1117/1.JATIS.4.2.021402

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

© 2018 Author(s). Photoacoustic imaging comprises an optical excitation within a target zone and the detection of the ultrasonic wave so created. A pulsed laser illuminates the target zone, and this illumination causes rapid thermoelastic expansion that generates a broadband high-frequency ultrasonic wave (photoacoustic wave, PA). In this paper, we report proof-of-concept experiments for nondestructive testing of laminar materials using a PA microscope. A specimen containing carbon-fiber-reinforced plastic (CFRP) was used in this experiment and involved an artificial delamination. A 532-nm-wavelength laser irradiates the top surface of the specimen, and the resulting ultrasonic waves are received by a point-focusing immersion transducer on the same side. Our system estimated the depth and dimension of the subsurface delamination accurately. By coating a light-absorbing material on the surface, the amplitude of the PA wave increased. This finding shows that the signal-noise (S/N) ratio of the scattered wave from delaminations can be improved with the surface coatings.

DOI： 10.1063/1.5031633

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2017 Japan Society for Composite Materials, Korean Society for Composite Materials and Informa UK Limited, trading as Taylor & Francis Group. Fiber waviness is a process-induced defect that greatly decreases the compressive strength of carbon fiber composites. In this study, we developed eddy current techniques that enable non-contact visualization of waviness distribution. To visualize in-plane waviness in a carbon fiber composite, we visualized the path of eddy current flowing along the carbon fiber by measuring the magnetic field. Finite element analyses show that the shape of the in-plane waviness can be visualized in the distribution of the magnetic field from the eddy current. However, with increasing distance between the surface of the tested material and measurement plane, the visualization increasingly underestimates the in-plane waviness angle. To avoid this underestimation, we propose a magnetic imaging method that can reconstruct the magnetic field at the surface. The surface magnetic field was reconstructed by using the magnetic field data measured away from the surface. Experiments were performed on a cross-ply laminate with artificially induced in-plane waviness. The distribution of in-plane waviness can be successfully visualized from the measured magnetic field. Using this magnetic field imaging method to enable non-contact measurements, the angle of waviness can be measured with an error of only 1°.

DOI： 10.1080/09243046.2017.1344917

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2017, © The Author(s) 2017. The effects of machined circular holes on the mechanical properties and failure characteristics of a unidirectional CFRP were investigated. Our approach was to change the location and the number of holes: (i) a two-set hole was machined with different modes: (A) parallel, (B) 45°and (C) a direction perpendicular to the loading direction; and (ii) multiple holes from n = 0 to 5 were made in the sample parallel to the loading direction. The higher tensile and higher fatigue strengths were obtained for the CFRP sample produced by mode A, compared to modes B and C. This was attributed to the different extend of the maximum stress and stress distribution, caused by the geometrical effects on the sample. The ultimate tensile strength (σUTS) of the sample was well predicted by the geometrical criterion. If the number of holes was increased from n = 0 to n = 2, the tensile strength decreased dramatically. However, the tensile strength did not strongly decrease further for samples with multiple holes from n = 2 to 5. The tensile strength is correlated with the maximum stress adjacent to the hole(s). Those stress values were verified by a 2D digital image correlation and a finite element analysis. Material failure of the CFRP during tensile loading was revealed by nondestructive testing using a piezoelectric ceramic, and debonding of the fibers occurred even at a low applied stress of approximately 35% σUTS.

DOI： 10.1177/0021998317709331

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2017 Elsevier Ltd An ultrasonic guided wave-based method for cure monitoring and estimation of anisotropic viscoelastic properties of carbon fiber reinforced plastics is developed. A guided wave propagating in the transverse direction of a unidirectional carbon fiber reinforced plastic in vacuum bag molding is measured, and its energy velocity and attenuation are obtained after gelation. The transfer matrix method and micromechanical modeling are used to calculate the energy velocity and attenuation in a stratified plate as a function of the complex modulus of the resin. The development of the complex modulus during cure is estimated by comparison of the experimental data with the numerical analysis, and the storage modulus and loss modulus are expressed as functions of the degree of cure using differential scanning calorimetry. The method developed in this study enables non-invasive in-process measurements of the cure state and viscoelastic properties of the carbon fiber reinforced plastic during the cure cycle.

DOI： 10.1016/j.polymertesting.2017.12.032

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© 2018 The Authors. We present x-ray characteristics of the Hard X-ray Telescopes (HXTs) on board the Hitomi (ASTRO-H) satellite. Measurements were conducted at the SPring-8 BL20B2 beamline and the ISAS/JAXA 27-m beamline. The angular resolution defined by a half-power diameter was 1.9′ (HXT-1) and 2.1′ (HXT-2) at 8 keV, 1.9′ at 30 keV, and 1.8′ at 50 keV. The effective area was found to be 620cm2 at 8 keV, 178cm2 at 30 keV, and 82cm2 at 50 keV per mirror module. Although the angular resolutions were slightly worse than the requirement (1.7′), the effective areas sufficiently exceeded the requirements of 150cm2 at 30 keV and 55cm2 at 50 keV. The off-axis measurements of the effective areas resulted in the field of view being 6.1′ at 50 keV, 7.7′ at 30 keV, and 9.7′ at 8 keV in diameter. We confirmed that the main component of the stray x-ray light was significantly reduced by mounting the precollimator as designed. Detailed analysis of the data revealed that the angular resolution was degraded mainly by figure errors of mirror foils, and the angular resolution is completely explained by the figure errors, positioning errors of the foils, and conical approximation of the foil shape. We found that the effective areas were ∼80% of the designed values below 40 keV, whereas they steeply decline above 40 keV and become only ∼50%. We investigated this abrupt decline and found that neither the error of the multilayer design nor the errors of the incident angles induced by the positioning errors of the foils can be the cause. The reflection profile of each foil pair from the defocused image strongly suggests that the figure errors of the foils probably bring about the reduction in the effective areas at higher energies.

DOI： 10.1117/1.JATIS.4.1.011210

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2019 Trans Tech Publications, Switzerland. The purpose of this research is to determine the state inside the material using finite-element analysis and to improve the performance of a rotary-draw bending forming by clarifying the mechanism of wrinkle generation. An analytical model of rotational drawing was made by using the general-purpose nonlinear finite-element analysis software MSC Marc, and the analytical results were compared with experimental results to verify the validity of the model. Furthermore, the mechanism of wrinkle generation was investigated. With the progress of processing, wrinkles occur not in the R part but in the original tube-side straight-tube part. The coefficient of friction between the tube material and the R portion of the bending mold promotes the occurrence of wrinkles and the growth of the generated wrinkles. Because wrinkles occur even if the friction coefficient between the tube material and bending mold R part is ignored, the generation condition of wrinkles also depends on parameters other than the friction coefficient.

DOI： 10.4028/www.scientific.net/MSF.943.43

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2019 Trans Tech Publications, Switzerland. This study focus on the diameter-enlarged ratio, which is an important parameter for evaluating the workability of a partial diameter-enlarged process. Moreover, the study attempts to explain the influence of the fillet radius of the die end on the fatigue characteristic of the test piece after forming and the limit of the diameter-enlarged ratio without fatigue damage in the forming process. Three types of dies with different fillet deformations were used, and tensile tests were carried out after the processing was performed on three types of carbon steel. The fatigue properties of the test specimens after forming and the limit of the diameter-enlarged ratio at which no fatigue damage occurred were investigated. The results obtained are as follows: increasing the fillet radius of the die helped to ease the stress concentration at the root of the diameter-enlarged part, and shaft diameter-enlarged processing could be done without fatigue damage. Using a die having a radius equal to or larger than the appropriate fillet radius helped to increase fatigue strength, without causing fatigue damage, even if the diameter-enlarged ratio increased; notch sensitivity increased with an increase in the diameter-enlarged ratio, but the apparent notch sensitivity coefficient decreased with an increase in fillet radius in all the test pieces. A large limit for the diameter-enlarged ratio without fatigue damage may be obtained by using a die with an appropriate fillet radius.

DOI： 10.4028/www.scientific.net/MSF.943.34

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2019 Trans Tech Publications, Switzerland. The hardness test, Charpy impact test, and axial expansion experiment were performed on a medium carbon steel S35C specimen typically used for shaft materials after first subjecting it to quenching and tempering heat treatment under different heating temperatures/time conditions. The effect of the tempering conditions on the mechanical properties of the specimen and the limit of the diameter-enlarged ratio used for evaluating the workability of the partial diameter-enlarged were investigated. The summary of the results are as follows: after quenching at 880 °C, a fine troostite or sorbite structure was obtained under all heat treatment conditions at heating temperatures of 550 °C to 675 °C, and heating times of 0.5 h to 1.5 h. An improvement was shown in the limit of the diameter-enlarged ratio because the quenching and tempering heat treatment led to an increase in the Charpy impact value/ductility as well as a reduction in the hardness, tensile strength, and yield strength; the partial diameter-enlarged process could be performed on the heat treated material at almost the same deformation speed as a cold-drawn material with a much lower axial pressure; it was possible to estimate the diameter-enlarged deformation behavior using the tempering parameter M. We confirmed that the quenching tempering heat treatment performed in this study facilitates the improvement of the workability of the diameter-enlarged.

DOI： 10.4028/www.scientific.net/MSF.943.26

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本複合材料学会  

DOI： 10.6089/jscm.43.90

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

J-GLOBAL

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：金沢工業大学材料システム研究所  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：金沢工業大学材料システム研究所  

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2017 Author(s). The use of fiber reinforced plastics (FRPs) as structural components has significantly increased in recent years. FRPs are made of stacks of plies, each of which is reinforced by fibers. When modeling ultrasonic wave propagation in FRPs, it is important to introduce three-dimensional mesoscopic and microscopic structures to account for the anisotropy and heterogeneity caused by fiber orientation and the lay-up of laminates. In this study, a finite element method using an image-based modeling is applied to simulation of ultrasonic wave propagation in a carbon FRP (CFRP). Here, the elastic stiffness of a single ply is determined using a homogenization method, where a CFRP microstructure is incorporated on the basis of a two-scale asymptotic expansion. The wave propagation in a CFRP specimen composed of unidirectionally aligned fibers is calculated, and the simulation results are compared to visualization results obtained for ultrasonic wave propagation using a laser scanning device.

DOI： 10.1063/1.4974729

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記述言語：日本語   出版者・発行元：公益社団法人 土木学会  

炭素繊維補強樹脂(CFRP)の品質や安全性を担保するために，超音波検査技術の高度化が望まれている．CFRPは炭素繊維を織り込んだ薄いシートを任意の角度で積層して成形されるため，用途や要求性能に合わせて専用設計が必要となる．このとき，材料異方性が発現することになり，超音波の伝搬速度が方向によって異なるため，事前にこの特性を把握することが肝要である．超音波探傷におけるCFRPの数理モデルと波動伝搬解析技術の構築を見据えて，その際の基本的なパラメータである弾性スティフネスを精度良く求める技術を開発することが本研究の目的である．ここでは，レーザー超音波法を用いて超音波伝搬時の面外変位を各点で計測し，その全波形を時空間フーリエ変換することで位相速度を抽出する．位相速度と弾性スティフネスはChristoffel方程式を用いて陽な形で表すことができる．ここでは，複数の方向の位相速度から一方向強化CFRPの5つの独立な弾性スティフネスを求める最適化問題を構築し，最小二乗法によってこれを求める．得られた弾性スティフネスを圧縮試験で得られた結果と比較する．また，この弾性ティフネスをもとに数理モデルを作り，時間領域の有限要素解析を実行する．数値的に得られた群速度と可視化から得られた群速度とを比較し，本手法によって求めた弾性スティフネスの妥当性について示す．

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/mej.16-00151

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記述言語：日本語   出版者・発行元：日本複合材料学会  

Resistance variation and Joule heating of carbon fiber reinforced plastic after applying a large electric current pulse are investigated. The current has a pulse width of several microseconds and the typical peak value is 2 kA. A double-digit decrease in resistance of a cross-ply laminate is observed after applying the kA current pulse. The decrease in resistance of the cross-ply laminate can be controlled by varying the charge voltage in the pulse generator circuit. In the case of DC current Joule heating, the direction of heat conduction at the surface is parallel to the fiber direction of the cross-ply laminate. However, the kA current pulse locally heats in the vicinity of the electrode and the thermal profile is different from the DC current.

DOI： 10.6089/jscm.42.228

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記述言語：英語  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本複合材料学会  

This paper presents machining quality and characteristics of circular piercing hole produced by punch press in thermosetting CFRP laminates. First, a hole was produced by using a punch with flat surface at room and elevated temperatures. After the piercing process, damages and burrs on the surfaces and the cutting planes around the hole were microscopically observed. Internal damage such as delamination was then observed using radiography. Second, the quality of the hole was examined through roundness measurement using three coordinate measuring machine. Finally, piercing process mechanism was discussed from antiplane load and displacement diagrams and cutting planes observations of the specimen during the piercing process. It was proved from X-ray radiography and quality evaluation of the hole after the piercing process at elevated temperature that the least amount of delamination was generated although the roundness was low. It was presumed from the piercing process mechanism that the roundness becomes low because the face parallel to fiber direction in the middle layers was preferentially cut.

DOI： 10.6089/jscm.42.13

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. We fabricated x-ray mirrors from carbon-fiber-reinforced plastic with a tightly nested design for x-ray satellites, using a replication method for the surfaces. We studied the effects of print-through on the mirror surface as a function of curing temperature. With room temperature curing, the root-mean-square value of the surface error was 0.8 nm. The reflectivity was measured using 8-keV x-rays, and the roughness was calculated as 0.5 nm by model fitting - comparable to that of the ASTRO-H/HXT mirror. We verified the long-term stability of the mirror surface over 6 months. We fabricated Wolter type-I quadrant-shell mirrors with a diameter of 200 mm and performed x-ray measurements at BL20B2 in the SPring-8 synchrotron radiation facility. We obtained reflection images of the mirrors using a 20-keV x-ray spot beam with a slit size of 10 x 1 mm in the radial and circumferential directions, respectively. The averaged half-power diameter (HPD) of the images in one mirror was 1.2 arc min in the circumferential center of the mirror and 3.0 arc min at the edge. In the spot images with a smaller slit size of 10 x 0.2 mm, we achieved an HPD of 0.38 arc min in the best case.

DOI： 10.1117/1.JATIS.2.1.014002

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2016 SPIE. A ray-trace simulation code for the Hard X-ray Telescope (HXT) on board the Hitomi (ASTRO-H) satellite is being developed. The half power diameter and effective area simulated based on the code are consistent with ground measurements within 10%. The HXT observed the pulsar wind nebula G21.5-0.9 for 105 ksec. We confirmed that the encircled energy function and the half power diameter obtained from the data are consistent with the ground measurements.

DOI： 10.1117/12.2232135

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2016 SPIE. We are developing an X-ray mirror using the CFRP as substrate in order to improve the angular resolution of tightlynested type X-ray telescope on board future X-ray satellites. We have fabricated Wolter-I designed monolithic CFRP mirrors and made improvements in the fabrication process. In the updated CFRP mirror, the half-power width of the reflection image by optical measurement was 0.8 arc-minutes on average. The measurement of the characterization of the updated CFRP mirrors at ISAS X-ray beam-line was performed in December 2015, and confirmed that the imaging quality of the CFRP mirror changed with increasing duration in vacuum chamber. We also present a current status of development of more intricate-structure CFRP substrate such as four-stage X-ray optics.

DOI： 10.1117/12.2232650

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2016 SPIE. The Japanese X-ray Astronomy Satellite, Hitomi (ASTRO-H) carries hard X-ray imaging system, covering the energy band from 5 keV to 80 keV. The hard X-ray imaging system consists of two hard X-ray telescopes (HXT) and the focal plane detectors (HXI). The HXT employs tightly-nested, conically-approximated thin foil Wolter-I optics. The mirror surfaces of HXT were coated with Pt/C depth-graded multilayers. We carried out ground calibrations of HXTs at the synchrotron radiation facility SPring-8/BL20B2 Japan, and found that total effective area of two HXTs was about 350 cm2 at 30 keV, and the half power diameter of HXT was about 1.'9. After the launch of Hitomi, Hitomi observed several targets during the initial functional verification of the onboard instruments. The Hitomi software and calibration team (SCT) provided the Hitomi's data of G21.5-0.9, a pulsar wind nebula, to the hardware team for the purpose of the instrument calibration. Through the analysis of the in-flight data, we have confirmed that the X-ray performance of HXTs in orbit was consistent with that obtained by the ground calibrations.

DOI： 10.1117/12.2231258

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記述言語：日本語   出版者・発行元：一般社団法人 日本物理学会  

<p>X線天文衛星「ひとみ」には、軟X線望遠鏡(Soft X-ray Telescope: SXT)が二台搭載された。米国のGSFC/NASAが主体で開発されている。SXT-S、SXT-Iと呼ばれ、それぞれの焦点面検出器はX線カロリメーター検出器 SXS、X線CCDカメラ SXI に対応する。どちらの検出器にも天体の像が結ばれていることが確認できた。また、スペクトル中には地上のキャリブレーションで予想していた反射鏡表面に金のMやLの吸収端が見えていた。当講演では、機上で得られた性能及び、地上との予測の比較を報告する。</p>

DOI： 10.11316/jpsgaiyo.71.2.0_369

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記述言語：英語   出版者・発行元：SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS  

DOI： 10.1117/1.JATIS.1.3.039801

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

© 2015 International Committee on Composite Materials. All rights reserved. This study experimentally and numerically characterizes the high-velocity impact damage in CFRP laminates to clarify the damage extension mechanisms. To this end, we focus on impact damage near perforation. High-velocity impact tests were conducted for two types of cross-ply laminates. At a relatively low velocity less than 200 m/s, a crater with fiber breaks, oblique matrix cracks, and delamination were observed just beneath the impact point. Delamination had a fan shape, which was similar to that observed in low-velocity impact tests. Catastrophic ply-failure zone, which included extensive fiber breaks, matrix cracking, matrix crushing, and delamination, appeared in the middle of the laminate at an impact velocity over 300 m/s. The extension of high-velocity impact damage in composite laminate was then predicted by smoothed particle hydrodynamics (SPH). A crater was formed by matrix failure and fiber breaks generated in the top 0° ply near the impact point. Ply interfaces were then delaminated, and a matrix cracking and crushing zone appeared in the middle plies. This damage pattern, including the delamination shape, agreed with the observation. Delamination mainly extended at a ply-interface along the matrix crack in the lower ply regardless of the stacking sequence. Based on the experiments and the analyses, the mechanisms of high-velocity impact damage in CFRP laminates will be discussed.

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© (2015) Trans Tech Publications, Switzerland. Metal pipes have a long history as fluid conduits, and are commonly joined with components such as elbows to form bent transport paths. However, with the increasing demands for economy and energy saving, pipes with reduced joints and thinner walls are desired. The number of joints can be reduced by a drawing and bending process that forms a bend section at any position in the pipe. However, this approach incurs problems such as wrinkling and flattening, especially under conditions of large bending angle, decreased bending radius, and thin pipe walls. In this research, applying vibrations to the mandrel was trialed as an approach for controlling the wrinkle depth and flattening. First, processing experiments were performed on thin walled pipes (wall thickness = 0.5 mm; outer diameter = 14 mm). The change of flattening and the number and depths of wrinkles were investigated in the presence and absence of vibrations. Next, simulations were performed using the commercial nonlinear finite element software. Through these simulations, the flatness and appearance of wrinkles were analyzed by modeling the behavior and distribution of stresses and strains in the processing process. The application of vibration to the mandrel appears to be a promising approach for controlling the wrinkling and flattening problems during pipe processing.

DOI： 10.4028/www.scientific.net/KEM.656-657.600

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© (2015) Trans Tech Publications, Switzerland. This paper presents shear cutting behaviors in thermosetting and thermoplastic CFRP laminates. Cross-ply laminates were fabricated from unidirectional thermosetting and thermoplastic CFRP prepregs for shear cutting tests. The tests were conducted by using three upper blades (Blades A, B and C) with different clearance and shearing angles at room and elevated temperatures up to around the glass transition temperature Tg. The cross-sections near the cutting surfaces were observed to quantitatively measure the length of burrs and removal part. In addition, double cantilever beam (DCB) tests were performed to measure mode I interlaminar fracture toughness of the thermosetting CFRP at various temperatures. It was found that the optimum cutting for the thermosetting CFRP is achieved by using Blade C at a temperature of 70°C, which is slightly lower than Tg. However, optimum cutting conditions are not proposed for the thermoplastic CFRP yet since the dominant parameters are not always identified under the conditions within the present study.

DOI： 10.4028/www.scientific.net/KEM.656-657.347

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© (2015) Trans Tech Publications, Switzerland. We have proposed a new cold processing method to enlarge the diameter of a short section of a metal shaft using a combination of a cyclic bending load and an axial compressive load that is lower than the yield stress of the sample material. We call this cold processing method the diameter-enlargement working method, and refer to the enlarged section of the processed shaft as the diameter-enlargement section. The processing method produces large plastic deformation, and its Key features are as follows: the diameter-enlargement deformation progresses easily under a low axial compressive load at room temperature and the processed part exhibits little temperature increase. However, a crack is generated in the notch near the diameter-enlargement section during processing, and the cause is not yet clearly understood. Therefore, we conducted processing experiments to clarify the crack generation conditions, and simulated the working process using the finite element method to investigate the behaviors of stress and strain during processing. Furthermore, we calculated the low-cycle fatigue damage in the processed shaft using the Manson-Coffin expression. Based on the experiments and analyses, we determined that a fatigue crack is generated because of cyclic axial normal stress in the notch root at the axial-compressive loading side. The experimental and analytical fatigue strength was well described by the Coffin-Manson expression.

DOI： 10.4028/www.scientific.net/KEM.656-657.473

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© (2015) Trans Tech Publications, Switzerland. This paper presents experimental examples of machining damages resulting from a piercing process in CFRP laminates. A circular perforation was formed in CFRP cross-ply specimen with a punch jig using different blade angles and two distinct dimensional conditions. Surface, cross-sectional, and internal changes to the CFRP specimens after the hole-punching were observed using optical microscopy and X-ray analysis to quantitatively evaluate damage, including delamination, around the perforation area. Results indicate that the optimum piercing is achieved when the blades are parallel to fiber direction at an elevated temperature with blade angles essentially irrelevant.

DOI： 10.4028/www.scientific.net/KEM.656-657.185

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

© The Authors. We study a lightweight x-ray mirror with a carbon fiber reinforced plastic (CFRP) substrate for next-generation x-ray satellites. For tightly nested x-ray mirrors, such as those on the Suzaku and ASTRO-H telescopes, CFRP is the suitable substrate material because it has a higher strength-to-weight ratio and forming flexibility than those of metals. In flat CFRP substrate fabrication, the surface waviness has a root mean square (RMS) of ∼1 μm in the best products. The RMS approximately reaches a value consistent with the RMS of the mold used for the forming. We study the effect of moisture absorption using accelerated aging tests in three environments. The diffusivity of the CFRP substrate at 60°C and at relative humidity of 100% is ∼9.7×10-4 mm2·h-1, and the acceleration rate to the laboratory environment was 180 times higher. We also develop co-curing functional sheets with low water-vapor transmissivity on the CFRP substrate. Co-curing the sheets successfully reduced the moisture absorption rate by 440 times compared to the un-co-cured substrate. Details of the CFRP substrate fabrication and moisture absorption tests are also reported.

DOI： 10.1117/1.JATIS.1.3.034003

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

© 2015 International Committee on Composite Materials. All rights reserved. The purpose of the present study is to optimize the shear cutting conditions of CFRP laminates. First, specimens of thermosetting (epoxy) and thermoplastic (polyamide 6) CFRP cross-ply laminates 1.2 mm thick were cut by shearing using lower and upper blades. The shear cutting tests were performed at various temperatures ranging from a room temperature (RT) to temperatures higher than the glass transition temperature Tg. The effect of clearance between the upper and lower blades was investigated only for thermosetting CFRP specimens. Next, cross-sectional and internal damages adjacent to the cutting planes were observed using optical microscopy together with soft X-ray analysis to quantitatively measure the size of burrs, removal parts (lost from the workpiece due to cracking) and delamination area. Finally, double cantilever beam (DCB) and end-notched flexural (ENF) tests were performed to measure the modes I and II interlaminar fracture toughness of the thermosetting CFRP at various temperatures. It was proved from the experiment that the best machining quality, namely, the least delamination area, length of burrs and removal parts, was obtained at a temperature of 70oC and 45oC for the thermosetting and thermoplastic CFRP laminates, respectively. These optimum temperatures are lower than Tg, where the interlaminar fracture toughness becomes higher than that at RT while the rigidity is lower than that at RT. The optimum clearance was found to be around 0.05 mm for the thermosetting CFRP laminate. In addition, the maximum shear stress becomes almost constant when the clearance exceeds the optimum one.

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掲載種別：研究論文（学術雑誌）  

© 2014 Optical Society of America. The new Japanese x-ray astronomy satellite, ASTRO-H, will carry two identical hard x-ray telescopes (HXTs), which cover the energy range of 5 to 80 keV. The HXT mirrors employ tightly nested, conically approximated thin-foil Wolter-I optics, and the mirror surfaces are coated with Pt/C depth-graded multilayers to enhance the hard x-ray effective area by means of Bragg reflection. The HXT comprises foils 120-450 mm in diameter and 200 mm in length, with a focal length of 12 m. To obtain a large effective area, 213 aluminum foils 0.2 mm in thickness are tightly nested confocally. The requirements for HXT are a total effective area of >300 cm2 at 30 keV and an angular resolution of <1.70 in halfpower diameter (HPD). Fabrication of two HXTs has been completed, and the x-ray performance of each HXT was measured at a synchrotron radiation facility, SPring-8 BL20B2 in Japan. Angular resolutions (HPD) of 1.9′ and 1.8′ at 30 keV were obtained for the full telescopes of HXT-1 and HXT-2, respectively. The total effective area of the two HXTs at 30 keV is 349 cm2.

DOI： 10.1364/AO.53.007664

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

This paper presents monitoring the strain in carbon fiber reinforced plastic (CFRP) laminates and CFRP/concrete structures by means of pizeoresistance properties of CFRP. First, the piezoresistance behavior in a CFRP unidirectional laminate under mechanical loading was characterized. A two-dimensional model was proposed using a DC circuit equivalent to an electric resistance network in the CFRP laminate to predict the resistance change due to tensile loading. The surface resistivity and the initial gage factor are expressed as a function of the off-axis angle in the model. Secondly, the strain in the concrete/CFRP structures was monitored using the piezoresistance behavior of the CFRP in order to verify the validity of the electric strain monitoring method. The resistance change together with the mechanical strain was measured in the CFRP laminate adhesively bonded to concrete under three-point flexural loading.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

This paper proposes a new near-net-shape working method to partially enlarge and control shaft's cross section through a metal mold. This study investigates the changes in the sectional area of shafts during the processing under various processing conditions, and evaluates the changes with a filling ratio. We introduce the processing method and the processing conditions, and then we report the results of processing experiments. Lastly, we clarify that processing conditions influence on the geometry of the processed part. © (2014) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/AMM.473.35

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

This study experimentally and numerically investigated the damage extension of a brittle monolithic silicon carbide plate in response to the high speed impact of a projectile. An out-of-plane impact of a silicon nitride sphere with a velocity of 50 to 600 m/s induced multiple ring cracks on the contact surface. A crater, a cone crack, and a median crack were observed in the cross section under the contact point. The generation and extension of the damage were numerically studied based on linear fracture mechanics. A dynamic stress analysis using the finite element method demonstrated that the distribution of the principal axis corresponding to the maximum principal stress aligned radically from the contact point to induce a circular crack on the surface. (C) 2014 Published by Elsevier Ltd.

DOI： 10.1016/j.mspro.2014.06.017

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

High-velocity impact damage in CFRP laminates was studied experimentally and numerically. Part I of this study observed and evaluated near-perforation damage in the laminates and characterized the damage pattern experimentally. Part II predicts the extension of high-velocity impact damage based on smoothed particle hydrodynamics (SPH), which facilitates the analysis of large deformations, contact, and separation of objects. A cross-ply laminate was divided into 0 and 90 layers, and virtual interlayer particles were inserted to express delamination. The damage patterns predicted on the surfaces and cross-sections agreed well with the experiments. The analyzed delamination shape was similar to that resulting from a low-velocity impact, consisting of pairs of fan-shaped delaminations symmetric about the impact point. Finally, the mechanisms of high-velocity impact damage in CFRP laminates are discussed based on the observations and numerical analyses. © 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compositesa.2013.04.012

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2014 SPIE. The new Japanese X-ray Astronomy satellite, ASTRO-H will carry two identical hard X-ray telescopes (HXTs), which cover 5 to 80 keV, in order to provide new insights into frontier of X-ray astronomy. The HXT mirror surfaces are coated with Pt/C depth-graded multilayers to enhance hard X-ray effective area by means of Bragg reflection, and 213 mirror reflectors with a thickness of 0.22 mm are tightly nested confocally in a telescope. The production of FM HXT-1 and HXT-2 were completed in 2012 and 2013, respectively. The X-ray performance of HXTs were measured at the synchrotron radiation facility SPring-8/ BL20B2 Japan. The total effective area of two HXTs is about 350 cm2 at 30 keV and the angular resolution of HXT is about 1.'9 in half power diameter at 30 keV. The HXTs are in the clean room at ISAS for waiting the final integration test.

DOI： 10.1117/12.2054633

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2014 SPIE. We study lightweight X-ray mirror with Carbon Fiber Reinforced Plastic (CFRP) substrate for next generation X-ray satellites. CFRP is suitable material as substrate for tightly nested X-ray mirrors like telescope of Suzaku, ASTRO-H because it has properties of higher strength-to-weight ratio and flexibility of forming than that of metals. In the current year we performed fabrication of flat panels for baseline study and monolithic Wolter-I shell substrates by multi-plies pre-pregs. We also performed reflector replication based on technique for the ASTRO-H/HXT mirror fabrication. In this paper the development of the study of CFRP substrate fabrication and reflector replication will be reported.

DOI： 10.1117/12.2054837

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掲載種別：研究論文（国際会議プロシーディングス）  

This study experimentally and numerically investigates mechanism of shear-cutting for CFRP cross-ply laminates. Cross-ply laminates were cut in a wide range of clearance, which was the distance between the upper tool and the lower tool. Shearing zone was observed during cutting; the cut specimens were also observed by the soft X-ray radiography to evaluate delamination extension. Multiple transverse cracks and delamination first appeared in the shearing zone, and the top and the bottom 0° plies then broke at the contact edges by further indentation of the upper cutting tool. Shear-cutting process was then predicted by smoothed particle hydrodynamics (SPH). A unidirectional lamina was considered as a homogeneous orthotropic material, and nonlinear shear behavior of a unidirectional lamina was considered in order to take plastic deformation into account. Generation of fiber failure, matrix failure and delamination was predicted by stress-based criteria, and the stiffness and the stress corresponding to each failure mode were degraded. The predicted damage states as well as the failure-patterns agreed well with the observations. We compared the cutting process between the experiments and analysis, and discussed mechanisms of shear cutting, i.e., generation and evolution of damage, and influence of cutting parameters on damage states. The numerical simulation revealed that the damage pattern was governed not only by the shear stress but by the local bending stress. A large clearance enlarged the size of damage due to the considerable local bending, but provided little difference of the damage extension process, because the great shear stress generated between the two tool edges was the key factor of most of the damage.

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

We proposed a new cold processing method to partially enlarge the diameter of a shaft with a combination of a cyclic bending load and an axial compressive load that is lower than the yield stress of sample material. We call this cold processing method a diameter-enlargement working method, and call this processed part a diameter-enlargement part. Key features of the processing method are chiefly as follows: the diameter enlargement deformation progresses easily under a low axial compressive load at room temperature; the processed part has little temperature increase, although the processing causes large plastic deformation. We have tested the influence of the processing conditions and the mechanical properties of the sample materials in terms of diameter enlargement deformation behavior. However, little is known about the fatigue damage condition in a diameter enlargement part. Therefore, we carried out processing experiments to clarify crack generation conditions, and simulated working processing using finite element method in order to investigate behaviors of stress and strain during the processing. Furthermore, we evaluated low cycle fatigue damage in the processed part by using the Manson-Coffin expression. This paper clarified the mechanism of crack generation during the processing and evaluates the fatigue strength of the processed part. (C) 2014 Elsevier Ltd.

DOI： 10.1016/j.mspro.2014.06.242

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：ELSEVIER SCIENCE BV  

We proposed a new cold processing method to partially enlarge the diameter of a shaft with a combination of a cyclic bending load and an axial compressive load that is lower than the yield stress of sample material. We call this cold processing method a diameter-enlargement working method, and call this processed part a diameter-enlargement part. Key features of the processing method are chiefly as follows: the diameter enlargement deformation progresses easily under a low axial compressive load at room temperature; the processed part has little temperature increase, although the processing causes large plastic deformation. We have tested the influence of the processing conditions and the mechanical properties of the sample materials in terms of diameter enlargement deformation behavior. However, little is known about the fatigue damage condition in a diameter enlargement part. Therefore, we carried out processing experiments to clarify crack generation conditions, and simulated working processing using finite element method in order to investigate behaviors of stress and strain during the processing. Furthermore, we evaluated low cycle fatigue damage in the processed part by using the Manson-Coffin expression. This paper clarified the mechanism of crack generation during the processing and evaluates the fatigue strength of the processed part. (C) 2014 Elsevier Ltd.

DOI： 10.1016/j.mspro.2014.06.242

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2014 SPIE. The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of ΔE ≤ 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts.

DOI： 10.1117/12.2055681

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

We have proposed a new cold processing method to form a partial diameter-enlargement part in a hollow shaft. Using the processing method, the diameter-enlargement part with a large deformation is formed easily by applying compressive stress at yield stress level and cyclic torsional stress on two ends of specimen. In the present paper, processing experiments were conducted using the processing machine developed originally based on the processing principle, and deformation behaviors on the diameter-enlargement part were measured. In addition, the simulation analysis method in the processing was developed by the finite element method (FEM), the behaviors of stress and strain on processed part were analyzed, and deformation mechanism was investigated. It is clarified that the processing conditions affect the deformation behaviors base on the experiments and analysis. © (2014) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/AMM.473.30

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掲載種別：研究論文（国際会議プロシーディングス）  

© 2014 SPIE. The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions developed by the Institute of Space and Astronautical Science (ISAS), with a planned launch in 2015. The ASTRO-H mission is equipped with a suite of sensitive instruments with the highest energy resolution ever achieved at E > 3 keV and a wide energy range spanning four decades in energy from soft X-rays to gamma-rays. The simultaneous broad band pass, coupled with the high spectral resolution of ΔE ≤ 7 eV of the micro-calorimeter, will enable a wide variety of important science themes to be pursued. ASTRO-H is expected to provide breakthrough results in scientific areas as diverse as the large-scale structure of the Universe and its evolution, the behavior of matter in the gravitational strong field regime, the physical conditions in sites of cosmic-ray acceleration, and the distribution of dark matter in galaxy clusters at different redshifts.

DOI： 10.1117/12.2055681

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掲載種別：研究論文（学術雑誌）  

This article presents a stochastic approach to predict fatigue crack propagation (FCP) diagrams of continuous crack growth (CCG) and discontinuous crack growth (DCG) in polycarbonate (PC) under cyclic loading. First, it is assumed that the macroscopic fatigue crack propagates stochastically. The transition probability is then expressed in conjunction with the craze fibril breakdown model for CCG. Second, the stochastic process is applied to DCG assuming that DCG occurs because of an unstable crack growth in the craze zone. A fracture criterion using a stress intensity factor is introduced for the unstable crack growth. As a result, we obtain an FCP diagram where the rate in CCG is lower than that in DCG. The stress intensity factor range for the DCG-CCG transition can be theoretically determined. Finally, to verify the present approach, the experimental data of DCG and CCG of PC are fitted to the Paris equation. In addition, the relationship between the DCG band size and the number of cycles required for DCG is predicted in order to compare it with the experiment data. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers Copyright © 2013 Society of Plastics Engineers.

DOI： 10.1002/pen.23457

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Society of Materials Science, Japan  

This paper presents time-temperature parameter (TTP) methods for predicting the slow crack growth (SCG)-type creep rupture life in ceramics. First, a probabilistic delayed-fracture (PDF) model was proposed on the basis of the Arrhenius-type SCG concept in conjunction with the two-parameter Weibull distribution. Larson-Miller parameter (LMP) and Orr-Sherby-Dorn parameter (OSDP) were then derived from the PDF model, respectively. As a result, it was theoretically demonstrated that LMP could not be then related with the SCG concept , but OSDP could be related with that. Therefore, OSDP has more clear physical meaning than LMP for ceramics. Second, the material parameters associated with the PDF model were determined using the experimental creep data for silicon nitride. The validity of the model was confirmed through the comparison of LMP plots and OSDP plots using the experimental creep data and the material parameters. In addition, it was found that SCG mechanism changes at a transition temperature where the crack propagation index drastically drops.

DOI： 10.2472/jsms.62.569

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study investigated mechanisms of the extension of high-velocity impact damage in CFRP laminates. To this end, damage states due to near-perforation impact were studied in detail. This study consists of two parts. Part I presents the experiment results of high-velocity impact tests for CFRPs with specified stacking sequences. A crater and splits were observed on the impacted surface, while multiple splits with fiber breaks extended on the back surface. The cross-section beneath the impact point included catastrophic ply failure with extensive fiber breaks. Impacted specimens also exhibited a particular delamination pattern consisting of pairs of symmetric fan-shaped delaminations emanating from to the impact point and elongated delamination along the cracks in the bottom ply. These damage patterns were common to all of the stacking sequences. Part II of this study presents a numerical analysis of high-velocity impact based on smoothed-particle hydrodynamics and discusses damage extension mechanisms. © 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compositesa.2012.12.015

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, the impact damage and the tension after impact (TAI) strength of a carbon-fiber-reinforced sheet molding compound (CF-SMC) are analyzed. First, low-velocity impact damage is introduced to several CF-SMC coupon specimens for a variety of impact energies. Next, the impact damage is observed by ultrasonic inspection and optical microscopy to determine the damage state and quantify the damage area and depth. Then, the TAI strength is measured and correlated with such parameters as maximum impact load, impact energy, and damage area and depth. Finally, a simple fracture-mechanics model for predicting the TAI strength is proposed. It is proved that the TAI strength depends on the impact damage depth. © 2013 Japan Society for Composite Materials, Korean Society for Composite Materials and Taylor & Francis.

DOI： 10.1080/09243046.2013.764779

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

An examination has been made of the mechanical and failure properties of a recycled short carbon fiber reinforced plastic (rCFRP). The rCFRP samples were fabricated by the following process: the CFRP, consisting of epoxy resin with carbon fiber, is ground before mixing with acrylonitrile butadiene styrene resin with different weight fractions of CFRP. The tensile strength (σUTS) increased with increasing CFRP content, but dropped considerably for the sample with higher fiber content. From in situ measurement of localized failure in rCFRP, it appeared that material failure occurs even if a low tensile stress of 30% σUTS is applied. The localized damage was related to the pull-out (or debonding) of the fibers from the matrix. The fatigue strength increased with increasing the content of the recycled carbon fiber even for the samples with low tensile strength. This was attributed to the low crack driving force arising from severe crack closure. Details of the crack growth behavior were discussed using various crack growth models proposed in previous studies. © 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijfatigue.2013.07.005

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記述言語：日本語   掲載種別：研究論文（国際会議プロシーディングス）  

This paper presents residual strength properties of monolithic ceramics after static loading. First, a residual strength prediction model is proposed on the basis of the slow crack growth (SCG) concept. Second, the residual strengths in soda glass and alumina ceramics (Al2O3) after static loading were measured. The fracture surfaces were then observed. Third, the experimental results were compared with the predictions using the model. As a result, the experimental data for soda glass was in good agreement with the prediction. In contrast, the agreement was worse for Al2O 3. The residual strength in Al2O3 was larger than the fracture strength and increased with increasing loading time. © 2013 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaia.79.749

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/kikaia.79.749

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本材料学会  

This paper presents the Paris law for discontinuous crack growth (DCG) and continuous crack growth (CCG) in polycarbonate under cyclic loading. First, the length and height of the craze zone near the crack tip were expressed on the basis of fracture mechanics. Next, the craze fibril breakdown model for CCG was applied to DCG and correlated with the Paris law. In CCG, the microscopic crack propagation rate d<i>â</i>/d<i>N</i>equals to macroscopic one d<i>a</i>/d<i>N</i>. In contrast, d<i>â</i>/d<i>N</i> is not equal to d<i>a</i>/d<i>N</i> in DCG because the macroscopic crack does not propagate until the craze fibrils break after some number of cycles. Therefore, a failure criterion for unstable crack growth in the craze zone was introduced. As a result, it was concluded that the crack propagation exponent for DCG is the same as that for CCG, while the coefficient in the Paris law for DCG is larger than that for CCG. Finally, the experiment data for DCG and CCG in polycarbonate were fitted to the Paris law to verify the reasonability of the above conclusions. In addition, the number of cycles required for DCG predicted using the model was compared with the experiment result.

DOI： 10.2472/jsms.61.719

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掲載種別：研究論文（学術雑誌）  

This study investigates characteristics of foreign-object damage in plain-woven SiC/SiC composites after thermal loading. High-speed impact tests were conducted on virgin specimens, thermally exposed specimens, and thermally shocked specimens, in which the maximum temperature during thermal loading was 600°C or 1000°C. An oxide layer was generated on the specimen surface by thermal loading at 1000°C. Damaged areas on the front and back surfaces induced by particle impact were independent of thermal loading. However, in specimens thermally loaded at 1000°C, brittle failure, i.e. cone cracking without fiber pull-out, occurred due to oxidation of the fiber/matrix interfaces, and the ballistic limit velocity significantly decreased. Finally, the ballistic limit is predicted using static strength properties, and the effect of thermal loading on impact resistance is discussed. © 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compositesb.2011.11.021

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

This paper experimentally and analytically investigates the fatigue strength and of mechanical damage of the processed shafts. First, we carry out rotary bending fatigue tests and investigate the fatigue stgate strain hardening near the processed part. Finally, we simulate stress and strain distributions of the shaft during the processing using finite element method (FEM) and calculate the stress concentration rate at the notch root of the processed part. Based on the processing experiments and the finite element analyses (FEA), we clarify that the plastic work mechanically does not reduce the fatigue strength of shafts in the processing range. © (2012) Trans Tech Publications, Switzerland.

DOI： 10.4028/www.scientific.net/AMM.217-219.2346

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掲載種別：研究論文（国際会議プロシーディングス）  

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the highenergy universe via a suite of four instruments, covering a very wide energy range, from 0.3 keV to 600 keV. These instruments include a high-resolution, high-Throughput spectrometer sensitive over 0.3-12 keV with high spectral resolution of ?E 5 7 eV, enabled by a micro-calorimeter array located in the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers covering 5-80 keV, located in the focal plane of multilayer-coated, focusing hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12 keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the 40-600 keV band. The simultaneous broad bandpass, coupled with high spectral resolution, will enable the pursuit of a wide variety of important science themes. © 2012 SPIE.

DOI： 10.1117/12.926190

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掲載種別：研究論文（国際会議プロシーディングス）  

ASTRO-H is an international X-ray mission of ISAS/JAXA, which will be launched in 2014. One of the main characteristics of ASTRO-H is imaging spectroscopy in the hard X-ray band above 10 keV. ASTRO-H will carry two identical Hard X-ray telescopes (HXTs), whose mirror surfaces are coated with Pt/C depth-graded multilayers to enhance hard X-ray effective area up to 80 keV. HXT was designed based on the telescope on board the SUMIT balloon borne experiment. After feasibility study of the HXT design, the FM design has been deteremined. Mass production of the mirror shells at Nagoya University has been going on since August 2010, and production of mirror shells for HXT-1 was completed in March 2012. After the integation of X-ray mirrors for HXT-1, we measured hard X-ray performance of selected mirror shells for HXT-1 at a synchrotron radiation facility, SPring-8 beamline BL20B2. We will perform environment tests and ground calibarations at SPring-8 for HXT-1. In HXT-2, foil production is going on. © 2012 SPIE.

DOI： 10.1117/12.926753

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掲載種別：研究論文（国際会議プロシーディングス）  

ASTRO-H is a next version of Japanese X-ray astronomy satellite for lunch in 2014. The hard X-ray telescope (HXT) on board the satellite has a cylindrical mirror housing which contains reflection circular mirror foils. In the present paper, vibration properties of the mirror foils installed in the HXT on-board a satellite were investigated. Vibration tests and FEM analysis of mirror foils installed in the part model of HXT were conducted. From the experimental results, it appeared that the mirror had resonant frequencies at 64, 73 and 118Hz. The modal shapes of 64 and 73Hz peaks showed that the maximum amplitude appeared at edges of the foil. On the other hand, vibration amplitude became maximum at the center in the modal shape of 118Hz peak. In addition, it appeared that the first peak of the edge mode decreased with increasing acceleration while the second peak had weak dependency on acceleration. These vibration behaviors are thought to be governed degree of constraint of the connections between the foil and alignment bars. © 2012 SPIE.

DOI： 10.1117/12.925864

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

This paper presents a probabilistic model for predicting the constant fatigue life (CFL) diagrams for ceramics. First, a unified probabilistic delayed-fracture (PDF) model was proposed on the basis of the slow crack growth (SCG) concept in conjunction with the two-parameter Weibull distribution. Second, probabilistic CFL diagrams for effective volume V eff , effective loading time t effN f, fracture probability F and stress ratio R were obtained using the PDF model. The probabilistic CFL diagram was then related with the modified Goodman's diagram. Third, the unified strength parameters associated with the PDF model were determined using the experiment data of Si 3N 4 subjected to rotating bending. The stress amplitude - the number of cycles to failure curves were then predicted for R = -1 and 0 and various values of F. Moreover, the probabilistic CFL diagrams for various values of V eff and t effN f at F were depicted using the unified strength parameters. The validity of the present model was confirmed through the comparison of the predicted CFL diagrams with the experiment data. © 2012 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaia.78.912

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：公益社団法人 日本材料学会  

The effects of thermal loading conditions on the mechanical properties of S45C/Cu/Si_{<font size="-1">3</font>}N_{<font size="-1">4</font>} composites with brazing filler metals of AgCu and AgCuTi are described. Thermal loading tests were conducted on test samples under various heat conditions, after which the joint parts of the samples were observed with a focus on the Cu interlayers using an optical microscope. Four-point bending tests were conducted on the samples to evaluate the residual strength and stress strain characteristics of the samples. In addition, fracture surfaces and the origins of the fractures were observed using an optical microscope. The results showed that thermal loading of the S45C/Cu/Si_{<font size="-1">3</font>}N_{<font size="-1">4</font>} composites caused fatigue damage to the Cu interlayers and its amount increased with increases in the cycle number and temperature range of thermal loading. In the case of relatively-mild thermal loading conditions, fracture initiation regions were observed at the Cu/Si_{<font size="-1">3</font>}N_{<font size="-1">4</font>} boundary. In contrast, fracture initiation regions were observed in the Cu interlayer for the samples subjected to relatively-extreme thermal loading conditions. The increases in the cycle number and temperature range of thermal loading promoted reductions of residual strength, resilient modulus and residual fracture ductility for the samples. The reductions of the mechanical properties of the S45C/Cu/Si_{<font size="-1">3</font>}N_{<font size="-1">4</font>} composites were affected by the fatigue damage of the Cu interlayers. It was concluded that continuous operation (no start-stop system) is suitable for long-term use of ceramic/metal composites including interlayers in order to minimize reduction of their mechanical strength.

DOI： 10.2472/jsms.61.292

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担当区分：筆頭著者,　責任著者   記述言語：日本語   出版者・発行元：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

This paper presents electrical resistance change due to moisture in a CFRP cross-ply laminate with and without matrix cracking. First, the electrical resistance change was measured for wet unidirectional and cross-ply laminates at room temperature and below the freezing point. Next, an equivalent circuit model was proposed for the cross-ply laminate, taking the resistance change ascribed to matrix cracking into account. It was found that resistance characteristics of the intact cross-ply laminate were similar to those of the longitudinal ply. Resistance properties of the wet cross-ply laminate with matrix cracking were dominated by those of the longitudinal ply, while the resistance change of the dry cracked cross-ply laminate was affected by the matrix crack resistance. The resistance of the dry cracked laminate decreases below the freezing point. Contrarily, the resistance of the wet cracked laminate increases below the freezing point.

DOI： 10.6089/jscm.37.226

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents empirical models for predicting matrix crack density in a carbon fiber reinforced plastic (CFRP) cross-ply laminate under static-fatigue and cyclic-fatigue loadings. First, a modified slow crack growth (SCG) law, that covers the whole range of stress ratio R of tension-tension fatigue (0 ≤ R a;circ 1), was proposed. The modified SCG law and three conventional SCG laws were then combined with Weibull's probabilistic failure concept for predicting fatigue matrix crack density in a cross-ply laminate. Matrix crack density was expressed as a function of R, the maximum stress in the transverse ply and the number of cycles. Next, fatigue tests were performed for R of 0, 0.2, 0.4, 0.6, and 1 to determine the applicability of these four models. Finally, constant fatigue life (CFL) diagrams were investigated based on the modified model. © 2011 Society of Plastics Engineers.

DOI： 10.1002/pc.21192

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents the temperature dependence of predicting the flexural strength of a carbon fiber-reinforced sheet molding compound (CF-SMC). First, three-point flexural tests were performed to measure strength and elastic modulus at a variety of temperatures for CF-SMC specimens. Next, simple equations for predicting flexural strength were derived based on the fracture mechanics approach. The predicted flexural strength was in reasonably good agreement with the experiment results. The scatter of flexural strength was ascribed to the variation of location and size of the initial damage. In addition, the effect of temperature on flexural strength and delamination behavior was explained in association with the temperature dependence of the elastic modulus and fracture toughness. © 2010 Springer Science+Business Media B.V.

DOI： 10.1007/s10443-010-9171-x

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents a probabilistic approach for predicting fatigue life of glass subjected to near-ΔTC(critical temperature difference) thermal shock which exhibits little subcritical crack extension. First, thermal shock fatigue life Nf was derived as a function of temperature difference ΔT, fracture probability F and Biot's modulus β from the slow crack growth concept in conjunction with the Weibull distribution model. Next, thermal shock fatigue tests as well as flexural tests were performed for borosilicate glass to measure ΔTC and Nf versus ΔT. The parameters associated with slow crack growth were then determined from the experimental results while the heat transfer coefficient h or β was obtained with the aid of finite element analysis. Thirdly, the thermal shock fatigue diagram (ΔT-Nf curves) was depicted for various values of β. Finally, crack length was simulated on the basis of the present approach. © 2011 Blackwell Publishing Ltd.

DOI： 10.1111/j.1460-2695.2011.01556.x

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Society of Materials Science, Japan  

This paper presents a theoretical approach for estimating the fracture strength of brittle materials under variable loads. First, a model was established on the basis of the slow crack growth concept in conjunction with two-parameter Weibull distribution for a brittle material subjected to variable loads. Assuming fracture of a brittle material under constant load, a fracture criterion obtained from the model was related with the empirical life law. Next, four-point bending test was carried out for soda glass under two step crosshead speeds. The experiment result was compared with the predictions to verify the validity of the model.

DOI： 10.2472/jsms.60.477

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2472/jsms.60.418

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：金沢工業大学材料システム研究所  

CiNii Books

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Japan Society of Mechanical Engineers  

This paper presents models for predicting residual tensile strength after fatigue in unidirectional brittle fiber-reinforced ceramic composites. First, the subcritical crack growth law was employed to predict residual strength of fiber. Next, two models were proposed for residual strength of a composite. The first model, Model I, is established based on Curtin's probabilistic model that describes the relationship between strengths of the fiber and the composite. In the second model, Model II, the composite strength is directly derived from the survival probability of fiber. Thirdly, the relationship between lives of the fiber and the composite was investigated. Finally, a case study was conducted for a ceramic matrix composite (CMC) to obtain the residual strength of the CMC after static fatigue loading. It was proven that the life and the initial strength of the fiber and the composite depend on the shape parameter of fiber strength and the fiber/matrix interfacial shear stress. In contrast, the residual strength ratio of the composite was found to be almost independent of these two parameters.

DOI： 10.1299/jmmp.5.64

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

This paper aims at quantitative evaluation of residual strength after thermal shock in ceramics. First, a model predicting the residual strength from Young's modulus or crack density after thermal shock was established using a fracture mechanics approach. Next, thermal shock tests were carried out for porous SiC and soda glass. The residual strength and Young's modulus of both materials after thermal shock were measured. Then, the crack density of soda glass also was estimated by observing residual cracks on the surface. The experimental results were compared with the predictions to verify the validity of the model. The model exhibits good agreement with the experimental results. © 2011 The Japan Society of Mechanical Engineers.

DOI： 10.1299/kikaia.77.126

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記述言語：日本語  

DOI： 10.1299/kikaia.77.126

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

A simple model for predicting tensile strength of a sheet molding compound (SMC) composite was proposed. The tensile strength associated with two failure modes, delamination and splitting, was derived based on fracture mechanics. The predicted strength was compared with experimental results. It was proved that the both failure modes provide the critical strength in the present SMC composite. The dependence of specimen width was explained by the theoretical strength for the splitting mode. In addition, it is suggested that smaller size of strands that determine the size of initial damages gives larger tensile strength.

DOI： 10.6089/jscm.36.198

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00357045389?from=CiNii

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

The purpose of the present study is to obtain the fatigue limit diagram (FLD) and S-N diagram (SND) for transverse cracking in fiber reinforced plastic laminates under fatigue loading on the basis of the probabilistic slow crack growth (SCG) model. First, the deterministic and probabilistic FLD and SND were discussed for formulation. Next, the transverse crack density ρ was measured against number of cycles for various stress ratios <i>R</i> at a constant maximum stress to experimentally determine the parameters associated with the probabilistic SCG model. Finally, the FLD and SND were derived from the relationship among, ρ, <i>R</i> and fatigue life using the above parameters.

DOI： 10.6089/jscm.36.129

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00354605241?from=CiNii

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents a fracture criterion for predicting the strength of a CFRP unidirectional laminate with a hole. We formulated the point stress criterion (PSC) for notched composites with the characteristic distance at which the Tsai-Hill criterion for orthotropic materials was satisfied. The strengths of CFRP off-axis unidirectional laminates with a hole predicted by the PSC agreed well with the measured strengths, and the validity of the characteristic distance determined by the Tsai-Hill criterion was confirmed. Moreover, we observed the fractured surfaces of the holed specimens with small off-axis angles and found that the fracture mode within the characteristic distance (fiber breakage mode) was different from that away from the hole (shear fracture mode). These observations of the fractured surfaces suggested that the characteristic distance represented the size of the initially damaged area at the notch tip. © Koninklijke Brill NV, Leiden, 2010.

DOI： 10.1163/092430409X12605406698318

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Effects of loading rate on damage behavior in a pig liver loaded in compression were experimentally investigated. First, we developed a macroscopic damage model of liver cells or hepatocytes. Next, microscopic damage mechanism at the cell level was discussed through in-situ observation. Yield stress and strain were decreased with increasing strain rate. This behavior was ascribed to difference in pressure among individual liver components. The stress in a liver specimen subjected to a constant strain completely disappears after a certain period of time. For low strain rate, all the cells can endure high yield stress and strain because there is enough time for the individual cells to equilibrate the pressure. In contrast, for high strain rate, the yield stress and strain became lower since the cells cannot equilibrate the pressure due to limited intercellular blood flow during a short time. An interlobular connective tissue (Glisson's sheath) of a hepatic lobule was not easily damaged in the compressive field as it is stronger than the internal tissue. Consequently, the first failure occurred in the weakest central vein.

DOI： 10.1299/kikaia.76.625

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記述言語：日本語   出版者・発行元：The Japan Society for Technology of Plasticity  

We have recently developed a novel processing method for enlarging the diameter of a hollow shaft locally through the combination of cyclic torsional load with axial compressive load. First, experiments were conducted under various processing conditions to measure the deformation in the part with an enlarged diameter. Next, numerical simulation was performed using the finite element method to investigate the distributions of stress and strain in the processed part. The effects of axial-compressive load and twist angle on deformation behavior in the enlarged part were characterized through the above experiment and analysis. In addition, the cracking mechanism in the processed part was also investigated.

DOI： 10.9773/sosei.51.331

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper discusses high-speed impact damage in a three-dimensionally woven SiC/SiC composite (3D-CMC). The impact damage was introduced by a steel ball projectile in 3D-CMC plates with and without thermal exposure. The surface and internal damages were observed by optical microscopy and X-ray CT. A crater was observed on the collision surface. The X-ray CT measurement revealed that multiple pyramid-shaped cone cracks were generated beneath the crater when the impact speed was relatively low. At an impact speed exceeding the critical speed, a spall fragment was ejected from the back surface, while no internal damage was observed in the fragment. The spall fracture mode differed between the virgin and the thermally-exposed specimens. This difference is the result of embrittlement of the fiber/matrix interface due to oxidation of the carbon coating layer in the thermally-exposed specimen. In addition, it is found that z-yarns improve impact resistance by constraining delamination. © 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compositesa.2009.12.005

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents a theoretical approach for predicting transverse cracking behavior in a cross-ply laminate with a thick transverse ply under variable amplitude loads for which the cracks grow instantaneously, or very quickly, across the specimen width. The transverse crack density was derived on the basis of the slow crack growth (SCG) concept using the Paris law in conjunction with the Weibull distribution for a brittle material subjected to multi-stage cyclic loading. A fracture criterion obtained was related with the empirical rules by Miner and Broutman & Sahu. Next, the probabilistic SCG model was applied to transverse cracking in a cross-ply laminate under multi-stage cyclic loading. The two-stage fatigue tests with various loading sequences and amplitudes were conducted for carbon fibre reinforced plastic (CFRP) cross-ply laminates in addition to single-stage fatigue tests for various maximum stresses. The experiment results were compared with the predictions to verify the validity of the model. © 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compositesa.2009.11.005

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents a probabilistic fatigue model for transverse cracking in CFRP cross-ply laminates. First, a delayed fracture model for a crack in a brittle material subjected to cyclic loading was established on the basis of the slow crack growth (SCG) concept in conjunction with the Weibull's probabilistic failure model. Second, the above probabilistic delayed fracture model was applied to transverse cracking in cross-ply laminates during cyclic loading. The stress distribution and the length of the unit element were calculated with the aid of a shear lag analysis. The transverse crack density was expressed as a function of maximum stress, stress ratio and number of cycles using the parameters associated with the Paris equation and the Weibull distribution in addition to the mechanical properties. Unknown parameters were determined from experiment data for three kinds of cross-ply laminates to reproduce the transverse crack density against the number of cycles. The parametric studies using the obtained parameters revealed the effects of the Weibull modulus, crack propagation exponent and stress ratio on evolution of transverse cracking under fatigue loading. © 2010 VSP.

DOI： 10.1163/156855109X434784

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Japan Society for Technology of Plasticity  

Most shafts have a hexagonal shape, gears and multi steps on their largest diameter. Here, we studied a method of deforming a partial diameter into the near-net outer shape required for practical machine parts. The method was clarified experimentally to be actualized by controlling the final outer shape of a partial enlarging diameter using a metal mold with a hole of final outer shape, which was fixed on the rotating-side holder and rotated together with a shaft of work. The diameter enlarging behavior was investigated experimentally by measuring the changes in the distance between holders. On the basis of the mathematical modeling of their deformation behavior, the effects of processing conditions on the enlarging shape were researched and an estimating equation for clarifying the engineering optimization of processing conditions was obtained by mathematical model analysis.

DOI： 10.9773/sosei.51.455

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00351090286?from=CiNii

掲載種別：研究論文（国際会議プロシーディングス）  

This paper investigates fatigue strength and existence of mechanical damage experimentally and analytically. In particular, first, we carry out rotary bending fatigue tests and investigate fatigue strength for smooth specimens and specimen processed using the working method. Secondly, we measure Vickers hardness value to investigate strain hardening, and observe microstructure to investigate microstructure change in the diameter-enlargement part. Finally, we simulate stress and strain distribution in the processed part during the processing, using finite element method (FEM), and calculate stress concentration rate and plastic strain. And we predict the existence of mechanical damage in the processed part during the processing experimentally and numerical-analytically. The results of the experiments and analyses indicate that the fatigue damage is not generated in the processed part during the processing in the discussed range of the diameter-enlargement rate D/D 0<1.8, through comparing with the smooth specimens. © 2010 SPIE.

DOI： 10.1117/12.851963

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掲載種別：研究論文（国際会議プロシーディングス）  

The thin film technology called "depth-graded multi-layer" is used to manufacture reflector foils, which are inserted in a hard X-ray telescope. When the temperature of the foil changes from the temperature at which the foil was produced; thermal deformation is induced due to difference of linear coefficient of expansion of its constituents. The deformation causes performance of X-ray image formation to deteriorate. Therefore, it is absolutely imperative to estimate the amount of deformation quantitatively and to establish a method of temperature control for the foil under the thermal environment on orbit. We used the hard X-ray telescope, which is part of the currently-projected the ASTRO-H X-ray satellite, as an example for investigation. The effective method of the HXT thermal control was examined with the thermal analytical software, "Thermal Desktop". The deformation of the foil when the temperature was changed by 1 degree C was predicted by a finite element analysis (FEA). The thermal desktop analysis shows that the overall foil temperature in orbit can be close to the temperature at which the foils were produced (∼22degree C) by the newly developed thermal control method. The FEM analysis shows that the prediction of the foil deformation due to a temperature change of 1 degree C is about 8 μm. © 2010 SPIE.

DOI： 10.1117/12.856581

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掲載種別：研究論文（国際会議プロシーディングス）  

ASTRO-H is the new Japanese X-ray astronomy satellite for launch in 2013. HXT on board the satellite has a mirror housing which is a cylindrical case and contains reflection mirror foils, which are constrained by alignment bars. In order to investigate vibration properties of HXT on board the satellite, vibration tests and FEM analyses were conducted. From the results of x-vibration test, it was found that there were no resonant frequencies at frequency less than 120 Hz. It also appeared that foils move along grooves of alignment bars when the housing was vibrated because kinetic connection between foils and alignment bars is only friction force. From the simulated results, this loose connection used in the actual HXT housing is useful to suppress a strong resonance at 51Hz predicted by supposing tight connections such as adhesiveness. As for z-vibration properties, vibration property of the housing was complicated since foils leap when zacceleration becomes larger than 1G. However it could be confirmed that the distinct resonant peaks did not appear at frequency less than 200 Hz. From these results, it was found that HXT housing had not any resonant frequencies less than 120 Hz, which is the maximum frequency of sinusoidal vibrations applied when launched. © 2010 SPIE.

DOI： 10.1117/12.856846

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掲載種別：研究論文（国際会議プロシーディングス）  

The new Japanese X-ray Astronomy satellite, ASTRO-H will carry two identical hard X-ray telescopes (HXTs), which cover 5 to 80 keV. The HXT mirrors employ tightly-nested, conically-approximated thin-foil Wolter-I optics, and the mirror surfaces are coated with Pt/C depth-graded multilayers to enhance hard X-ray effective area by means of Bragg reflection. The HXT comprises foils 450 mm in diamter and 200 mm in length, with a focal length of 12 m. To obtain a large effective area, 213 aluminum foils 0.2 mm in thickness are tightly nested confocally. The effective area is expected to be ∼ 310 cm2 at 30 keV and the image quality to be ∼1.7′ in half-power diameter. © 2010 SPIE.

DOI： 10.1117/12.856892

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（国際会議プロシーディングス）  

This paper aims at characterizing the high-speed impact damage behavior in CFRP unidirectional (UD) and cross-ply (CP) laminates. First, high-speed (~ 400 m/s) impact damage was introduced by collision of a flying steel sphere (projectile) to CFRP plates with the use of an electric heat gun. The surface and internal damages of the CFRP specimens were observed by using optical microscopy together with radiography. The damage process model was then established on the basis of the experimental result. Next, the dynamic finite element analysis was performed to simulate the damage process. Cohesive elements were introduced in the analysis to express the initiation and propagation of delamination while the maximum stress fracture criteria were employed to express another type of damage such as tensile, compressive and shear failure of the elements. Finally, the simulation was compared with the experimental results to understand the damage evolution mechanism.

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（国際会議プロシーディングス）  

This paper aims at characterizing the effect of impact velocity on high-speed impact damage behavior in carbon fiber reinforced plastic (CFRP) unidirectional (UD) and cross-ply (CP) laminates. First, The surface and internal damages of CFRP plates impacted at a velocity ranging from 150 to 500 m/s were observed by using optical microscopy together with radiography. Next, dynamic finite element analysis was performed to simulate the damage process. Cohesive elements were introduced to express the delamination and splitting cracks while the maximum stress fracture criteria were employed to express the intralaminar failure. Finally, the simulation was compared with the experiment results to understand the damage evolution for two impact velocities. The damage process in both laminates was as follows: 1. A crater accompanied by splitting cracks is generated at the impact point on the front surface while splitting cracks due to bending are observed on the back surface. 2. Cone-shaped matrix cracking is observed in the UD laminate while few matrix cracking is generated in the CP laminate. 3. The shape of the delamination in the UD and CP laminate is a diamond and a spiral, respectively. Although these damage processes were not greatly affected by impact velocity, the degree of damage strongly depended on impact velocity in both laminates. In addition, it was found that a critical impact velocity for perforation in the CP laminate is slightly larger than that in the UD laminate.

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掲載種別：研究論文（国際会議プロシーディングス）  

The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly successful X-ray missions initiated by the Institute of Space and Astronautical Science (ISAS). ASTRO-H will investigate the physics of the high-energy universe by performing high-resolution, high-throughput spectroscopy with moderate angular resolution. ASTRO-H covers very wide energy range from 0.3 keV to 600 keV. ASTRO-H allows a combination of wide band X-ray spectroscopy (5-80 keV) provided by multilayer coating, focusing hard X-ray mirrors and hard X-ray imaging detectors, and high energy-resolution soft X-ray spectroscopy (0.3-12 keV) provided by thin-foil X-ray optics and a micro-calorimeter array. The mission will also carry an X-ray CCD camera as a focal plane detector for a soft X-ray telescope (0.4-12 keV) and a non-focusing soft gamma-ray detector (40-600 keV). The micro-calorimeter system is developed by an international collaboration led by ISAS/JAXA and NASA. The simultaneous broad bandpass, coupled with high spectral resolution of ΔE ~7 eV provided by the micro-calorimeter will enable a wide variety of important science themes to be pursued.

DOI： 10.1117/12.857875

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Japan Society for Technology of Plasticity  

A connecting work method of tightly fixing a shaft in the central hole of a circle plate was developed for application of axial-diameter-enlarging processing. This method was successfully used in tightly connecting two pieces of different material parts such as a circle plate and a shaft. Because it is performed at room temperature without either heating or cooling such as in a traditional shrinkage fitting, this work method was clarified to exhibit high performance for industrial use.

DOI： 10.9773/sosei.51.460

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00351090293?from=CiNii

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.6089/jscm.35.212

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

This study qualitatively investigates the effects of initially cut fibers (slits) on fracture behavior in carbon fiber reinforced plastic (CFRP) cross-ply laminates, which had alternate or identical slit angle ±θ in the 0° plies. Damage progress during tensile tests was observed for several geometries of cutting. We also numerically evaluated fracture behavior in laminates with slits by a layer-wise finite-element model with cohesive elements. The simulated damage patterns included matrix cracks along the slits, splits in the 0° layer from the slit tips, and transverse cracks in the 90° layer. Delamination was also generated at the crossing point of ply cracks due to the large shear stress, and then extended to form the triangular region bounded by the slits and splits. The predicted damage extension to the final failure agreed with the observations. A numerical study demonstrated that the damage near the slits produced a stress field similar to that of a penetrating notch. © 2009 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compositesa.2009.04.023

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2472/jsms.58.338

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents a delayed-fracture model for transverse cracking in CFRP cross-ply laminates under static fatigue loading. First, a delayed-fracture model for a crack in a brittle material was established on the basis of the slow crack growth (SCG) concept in conjunction with a probabilistic fracture model using the three-parameter Weibull distribution. Second, the above probabilistic SCG model was applied to transverse cracking in cross-ply laminates under static fatigue loading. The stress and the length of the unit element in the transverse layers were calculated with the aid of a shear-lag analysis, taking the residual stress into account. The transverse crack density was expressed as a function of applied stress and time with the parameters in the Paris law and the Weibull distribution function specified, in addition to the mechanical and geometrical properties. Unknown parameters were determined from experiment data gathered in static tensile and static fatigue tests. The reproduced transverse crack density at various applied loads agreed well with the experiment results. © 2008 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compscitech.2008.11.023

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：金沢工業大学材料システム研究所  

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（国際会議プロシーディングス）  

The high speed impact damage in CFRP laminates was experimentally and numerically investigated. The impact damages were observed using optical and X-Ray CT microscopy. The dynamic finite element analysis was performed to simulate the damage process introducing cohesive elements. The simulation shows good correlation with the experimental results.

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掲載種別：研究論文（国際会議プロシーディングス）  

The strength reliability of the ceramics/metal joints in the vacuum interrupters was studied focusing on the thermal stress around the ceramics/metal joints due to mismatch of thermal expansion coefficients between ceramics and metal. It was found from the experiment results that the residual strength of the joint depends on the amount of metal brazing alloy used as a jointing material. Firstly, in the present work, the thermal stress around the ceramics/metal joints was calculated using finite element analysis. Next, the effect of the amount of metal brazing alloy on the residual strength of the joint was investigated on the basis of a fracture mechanical approach. Finally, the amount of metal brazing alloy minimizing the strength reduction of the joint is determined using the results of the numerical analysis.

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掲載種別：研究論文（国際会議プロシーディングス）  

Astro-H mission is the new Japanese X-ray mission following Suzaku. One of the unique features of the mission is an imaging spectroscopy in a unprecedentedly wide energy region from 0.3 to 60 keV. The X-Ray Telescope (XRT) system covers the energy region by means of grazing incidence reflective optics. In the current baseline specification, the XRT system consists of two hard X-ray telescopes (HXTs) which cover 5 to 60 keV, and two soft X-ray telescopes (SXT-S and SXT-I) which cover 0.3 to about 10 keV. Both of HXT and SXT-S mirrors employ tightly-nested, conicallyapproximated thin-foil Wolter-I optics. The HXTs employ Pt/C depth-graded multilayers (supermirrors), while the SXTS employ a single layer of gold. We measured test reflectors for Astro-H HXT at SPring-8, and obtained the roughness of the test reflectors of < 4 Ȧ and the image blur after two reflections of 0.8'-1.1'. International collaboration has been formed for the project, and basic and design studies have been carried out. Based on the basic study, detailed studies of the flight design are in progress, and production facilities for the Astro-H XRT system are close to complete.© 2009 SPIE.

DOI： 10.1117/12.826004

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掲載種別：研究論文（国際会議プロシーディングス）  

This paper proposes a numerical model that simulates the high velocity impact damage in the CFRP. Fiber failure, ply cracks, and delamination are modelled by stress criterion, continuum damage mechanics, and cohesive zone model. Experimental and simulation results demonstrate the proposed model successfully simulates damage process in the CFRP.

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

Shear loading tests were executed to ceramics/metal joints used for an electronic device in various temperatures and loading rates. Fracture origin of the joints is formed from ceramics of interfacial neighborhood. According to FEM analysis, it is clarified that the driving force for the failure is not a shear stress but a tensile stress. The tensile stress dramatically decreases from just beneath the surface to interior portion. Slow crack growth behavior in nominal shear stress was estimated using fracture mechanics in the different conditions of loading rates.

DOI： 10.1299/jsmemecjo.2009.6.0_47

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人日本機械学会  

In the present study, quench tests were carried out to characterize the fracture behavior of advanced pore free SiC with damage tolerance during thermal shock. The residual strength of specimens after the quench tests was also measured. It is found that the critical temperature difference and the decrease in residual strength of this material are larger than those of conventional SiC. This is because the fracture is dominated only by flaw size since the wake zone is not generated during thermal shock with high strain rate. The critical temperature difference as well as the crack propagation is calculated with the aid of the unified theory of thermal shock.

DOI： 10.1299/kikaia.74.1156

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Society of Materials Science, Japan  

This paper discusses the fracture criteria for predicting the strength of unidirectional discontinuous glass fiber reinforced composites with side-notches. The point stress criterion (PSC) for notched composites was employed so that the Tsai-Hill criterion for orthotropic materials is satisfied. The fracture criterion proposed on the basis of linear notch mechanics (LNM) proposed by Hyakutake et al. was also discussed in association with the above two criteria. Strength of intact and notched unidirectional composites was experimentally obtained for various kinds of off-axis angle and notch depth. The stress concentration factor in the vicinity of a notch was calculated with the use of finite element analysis. It was found that the notched to intact strength ratio is almost independent of off-axis angle though it slightly depends on notch depth. The characteristic length for the PSC estimated through the above experimental and analytical results increases with increasing off-axis angle and notch depth. The critical maximum stress of the LNM-based criterion was shown to be a function of fiber orientation angle, but almost independent of notch depth. The LNM criterion was proved to be equivalent to the PSC that satisfies the Tsai-Hill criterion.

DOI： 10.2472/jsms.57.725

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper describes a model for predicting the resistance and piezoresistance behavior in a carbon fibre reinforced plastics (CFRP) unidirectional laminate under the mechanical loading at various temperatures. A two-dimensional model including temperature effect is established to predict the change in the resistance due to both tensile loading and temperature change. The initial gage factor (IGF) and the temperature coefficient as functions of the off-axis angle are obtained from the model. In addition, macroscopic parameters regarding resistance and piezoresistance are related with microscopic ones on the basis of an equivalent circuit model. It is observed that the IGF shows temperature dependence at all the off-axis angles and becomes the maximum at an off-axis angle of 12° at all the temperatures. The temperature dependence of IGF is mainly attributed to temperature-dependent piezoresistivities and compliances. The temperature coefficient is negative at all the off-axis angles and shows the minimum at 17°. The negative temperature coefficient of the laminate is found to be ascribed to the temperature dependence of resistance of carbon fibre as well as contact resistance between fibres. © 2007 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compscitech.2007.06.012

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掲載種別：研究論文（国際会議プロシーディングス）  

The connecting work method to fix tightly a shaft in the central hole of a circle-plate was developed for application of axial enlarging processing. This method was successfully applied for connecting tightly two pieces of different material parts such as a circle-plate and a shaft. Because of performing at room temperature without either heating or cooling, this work method was clarified to be in high performance from point view of industrial uses.

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掲載種別：研究論文（学術雑誌）  

We present a study on housing design for the X-ray telescopes (XRT) onboard the New Exploration X-ray Telescope (NeXT). The NeXT XRTs are larger than previous thin-foil XRTs. The XRT is required to have a sufficient stiffness in order to keep the high performance of the XRT in orbit. We performed a structure analysis of the virtual model of the NeXT XRT housing using the FEA software Marc. A virtual model of the NeXT XRT was designed based on the XRT of the SUMIT balloon experiment. From the structure analysis of the virtual model by Marc, we found that the displacement of the XRT housing is small. The maximum displacement is a few Âμm, which is satisfied with our goal of 10 Âμm. On the other hand, the alignment bars show a large displacement up to about 90 Âμm. This is caused because the alignment bars become longer, and the total weight of the thin foils increases due to the larger effective area. This analysis indicates that we have to use stiff alignment bars without reducing the effective area. This result is useful to design a proto-model of the XRT housing. We will examine the result of this FEA analysis by measuring the displacement of the proto-model.

DOI： 10.1117/12.788788

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（国際会議プロシーディングス）  

This paper presents experimental characterization of foreign object damage in three-dimensionally woven SiC/SiC composite (3D-CMC) plates with and without thermal shock. Thermal shock tests were performed using a micro-gas turbine engine which can give a sudden change in the temperature of combustion gas with the aid of an afterburner. Ballistic impact damage was introduced by collision of a flying sphere to 3D-CMC plates. A steel sphere with a diameter of 1.5 to 4.0 mm collided against target materials at the impact speed ranging from 200 to 1100 m/s. The damages on the surface of the specimen were observed by using optical microscopy. The damage consisting of a crater and breakage of fiber bundles was observed on the front (collision) surface. The surface damage area increases with increasing impact energy. The surface damage of thermally-shocked specimens was larger than that of virgin specimens. A spall fragment was ejected from the back surface at the impact energy larger than critical one (12 to 20 J) in both specimens while the fragment was broken into pieces only in the thermally-shocked specimens. The critical impact energy for spall depends on mass of a projectile and is not affected by thermal shock. Copyright © 2008 by JSCM.

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（国際会議プロシーディングス）  

This paper describes a delayed fracture model for transverse cracking in CFRP cross-ply laminates under creep loading on the basis of the slow crack growth (SCG) concept. First, an SCG-based fracture model for a crack in a brittle material was established in conjunction with a probabilistic fracture model using the three-parameter Weibull distribution. Secondly, the above probabilistic SCG model was applied to transverse cracking in cross-ply laminates under creep loading. The shear lag analysis was employed to consider the stress and the length of the unit element in the transverse layers. The transverse crack density was expressed as a function of applied stress and time when the parameters in the Paris law and the Weibull distribution were given in addition to mechanical properties. Unknown parameters were determined from experimental data of the static tensile and static fatigue tests. Reproduced transverse crack density at various applied loads agreed well with the experimental results.

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掲載種別：研究論文（国際会議プロシーディングス）  

This study investigates the damage progress in CFRP cross-ply laminates with initial fiber cracks, introduced in the fabrication process of composite structures by the use of chopped strands or cutting preforms. The fiber cracks will induce complex damage process and also become the source of the final fracture. Tensile tests were conducted for the coupon specimens with fiber cracks, and the damage progress in these specimens was observed by the soft X-ray radiography. We then evaluated the damage process in the laminate with fiber cracks by the layer-wise finite-element model with cohesive elements. The simulated damage patterns included the matrix cracks along the initial fiber cracks, splits in the 0° layer extending from the tips of the fiber cracks, and transverse cracks in the 90° layer. Delamination was also generated at the crossing point of ply cracks due to the large shear stress, and then extended in the triangular region bounded by the fiber cracks and splits. Furthermore, the damage state at the final failure was obtained in the damage analysis by applying a conventional damage criterion to the fiber breakages. The predicted damage extension to the final failure agreed with the observations. The numerical results also demonstrated that the damage near the initial fiber cracks produced a similar stress field to a penetrating notch.

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

In the present study, 4-point bending test was carried out by using porous ceramics to investigate statistical properties of damage-tolerant ceramics. Distribution of the bending strengths plotted on a Weibull probability paper was nonlinear and was very similar to superposed distribution. Consequently, the bending strength distribution was analyzed by cluster fracture probabilistic model with the basis of Markov process assuming the LLS rule. It is found that the probabilistic model agreed well than the 2-parameter Weibull distribution. Therefore this indicates that the bending strength distribution controls cluster size.

DOI： 10.1299/jsmemecjo.2008.1.0_291

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents the mechanical properties of a composite consisting of acrylonitrile-butadiene-styrene (ABS) resin mixed with carbon fiber reinforced plastics (CFRP) pieces (CFRP/ABS). CFRP pieces made by crushing CFRP wastes were utilized in this material. Nine kinds of CFRP/ABS compounds with different weight fraction and size of CFRP pieces were prepared. Firstly, tensile and flexural tests were performed for the specimens with various CFRP content. Next, fracture surfaces of the specimens were microscopically observed to investigate fracture behavior and fiber/resin interface. Finally, the tensile modulus and strength were discussed based on the macromechanical model. It is found that the elastic modulus increases linearly with increasing CFRP content while the strength changes nonlinearly. Microscopic observation revealed that most carbon fibers are separated individually and dispersed homogeneously in ABS resin. Epoxy resin particles originally from CFRP are dispersed in ABS resin and seem to be in good contact with surrounding resin. The modulus and strength can be expressed using a macromechanical model taking account of fiber orientation, length and interfacial bonding in short fiber composites. © 2007 VSP.

DOI： 10.1163/156855107780918982

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：金沢工業大学材料システム研究所  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

This paper describes effect of temperature on the resistance and piezoresistance behavior in a carbon fiber reinforced plastics (CFRP) unidirectional (UD) laminate under tensile loading. Resistance change of on- and off-axis specimens was examined during tensile loading at various temperatures. It was observed that the initial gage factor (IGF) shows temperature dependence for all the off-axis angles with the maximum at the angle of 12 degrees for all temperatures. Tempera-ture dependence of IGF was mainly attributed to temperature-dependent piezoresistivity and compliance. The resistivity decreased with increasing temperature for all the off-axis angles. This negative temperature coefficient of the UD laminate is ascribed to the temperature dependence of resistance of carbon fiber and the contact resistance between fibers.

DOI： 10.6089/jscm.33.14

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00289625949?from=CiNii

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

This paper describes the piezoresistance behavior in CFRP cross-ply laminates with transverse cracking loaded in tension. The resistance change due to transverse cracking and the gage factor (the rate of resistance change per mechanical strain) for each transverse crack density were experimentally measured during loading/unloading cycles. The resistance change-strain curves in the unloading/ reloading processes show the bilinear behavior where two gage factors are defined as the slopes of the bilinear curve. The residual resistance change after full unloading increases almost linearly with the mechanical strain while the gage factors do not always increase with the strain. The residual resistance change and gage factors are associated with transverse crack density on the basis of an equivalent resistance circuit.

DOI： 10.4028/0-87849-427-8.961

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Composite materials consisting of crushed carbon fiber reinforced plastics (CFRP) pieces and acrylonitrile-butadiene-styrene (ABS) resin were prepared by an injection mold method to solve the problem of recycling of CFRP. The electrical properties, such as electrical resistivity, alternating current impedance and electromagnetic interference (EMI) shielding effect, were measured for the composites. The electrical resistivity of the composites showed a percolation type of conduction behavior and no difference between parallel and perpendicular to the injection direction was observed for CFRP content higher than the critical value. Measurement of alternating current impedance revealed that the conduction mechanism is attributed to the direct conductive paths generated by distributed carbon fibers; however, strong frequency dependence of the impedance was observed for the CFRP content near the critical one. The frequency dependence of the impedance is caused by the inter-fiber connection and can be expressed as a simple equivalent circuit. The absorption component of shielding effect (SE) was smaller than the expected value estimated from its resistivity. The decline of SE is thought to be caused by the decrease in effective thickness due to fiber orientation.

DOI： 10.1163/156855107779755282

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：愛媛大学  

This paper presents electrical and mechanical properties of compound consisting of thermoplastic resin mixed with carbon fiber reinforced plastic (CFRP) pieces. CFRP pieces made by crushing CFRP wastes are utilized in this material. Nine kinds of compounds with different weight fraction and size of CFRP pieces are prepared. Firstly, electrical impedance of the compounds was measured as a function of frequency. Electromagnetic shield effect of the compounds was also investigated and compared with that of a CFRP laminate. Secondly, mechanical properties such as tensile and flexural strength were measured. Finally, the polished surface and fracture surfaces of the specimens were microscopically observed to investigate the effect of orientation and distribution of CF and CFRP pieces on mechanical and electrical properties. The compound has a variety of conductivity depending on content of CFRP pieces. Mechanical properties also increase with increasing CFRP content.

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その他リンク： http://iyokan.lib.ehime-u.ac.jp/dspace/handle/iyokan/1474

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：The Japan Society of Mechanical Engineers  

An electromechanical model is proposed for predicting the resistance change in CFRP cross-ply laminates with transverse cracking loaded in tension. A one-dimensional equivalent circuit model was established for describing the relation between the resistance change and mechanical strain at a given transverse crack density. A shear lag model was employed for obtaining the mechanical strain distribution. The relative resistance change-strain curve was measured for various transverse crack density and the slope and secant of the curve were defined as the gage factor and residual resistance change, respectively. Unknown functions in the model were determined using the measured residual resistance changes. The model can predict the bilinear behavior in the relative resistance change-strain curves during loading/unloading. It is found that the second residual resistance change can be the parameter for predicting transverse crack density because it increases monotonically with transverse crack density compared with the gage factors.

DOI： 10.1299/jmmp.1.975

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

Advanced Pore-Free SiC (APF-SiC) with super-high strength is expected to be used as engineering structural materials since it has damage tolerance ability by preceding failure of metallic silicon particles In the present study, thermal shock tests of this material were carried out to characterize the fracture behavior. The residual strength after thermal shock was also measured. It is found that the critical temperature difference ΔT_c of this material is larger than that of conventional SiC due to smaller size of pre-existing flaws. As the result, the validity of the Griffith's theory was experimentally confirmed. In addition, the damage tolerance behavior in thermal-shocked materials is not observed because the metallic silicon particles may he failed by thermal shock.

DOI： 10.1299/jsmemecjo.2007.1.0_647

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（国際会議プロシーディングス）  

This paper presents characterization of fracture behavior of laminates with initial cracks in fibers. Initial fiber cracks were introduced in prepreg sheets and cross-ply laminates using the cracked prepregs were fabricated. Tensile tests were conducted to obtain the strength and the damage propagation on the top and edge surfaces of the laminate was observed microscopically. Effect of crack geometry on strength and fracture behavior was discussed. The strength of the cracked laminate is proportional to the intact width and independent of crack geometry. Splitting from the initial crack tip, as well as transverse cracking and delamination occurred progressively while fiber breakage takes place just before final failure of the specimen.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

The impact damage in a silicon carbide plate caused by a collision of a silicon nitride sphere was characterized through microscopic observations as well as an analysis based on the Hertz's contact theory. The experimental results in the impact tests were compared with those in the quasi-static indentation tests. It was proved that the minimum and maximum radii of multiple ring cracks increased with increasing speed or maximum collision load, and that the corn crack growth also had the collision speed-dependency. The maximum radius of the ring crack agreed well with a theoretical one which was derived based on the Hertz's theory while the minimum radius of the ring crack becomes smaller than theoretical one at high collision speeds where the sphere was broken into pieces due to impact load. It was presumed from the analysis that a ring crack with a minimum radius was generated when the collision load reached 40% of the maximum one.

DOI： 10.1299/kikaia.72.2045

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents effect of temperature and after-cure on fatigue fracture behavior in a glass fibre reinforced phenolic resin composite. Firstly, monotonic tensile tests were conducted to measure the stress-strain curves and acoustic emission (AE) behavior. Secondly, fatigue tests at room temperature were performed for the virgin and two kinds of after-cured specimens. Thirdly, S-N curves are measured for the specimens with and without a hole at various temperatures. Fourthly, fatigue crack propagation (FCP) tests and in situ microscopic observation under tensile loading were conducted using notched specimens to investigate crack propagation behavior. Finally, fracture surfaces after the tests were observed by means of scanning electron microscopy (SEM). It is found that final failure abruptly takes place for the monotonic and fatigue tests without showing visible damage on the surface of the specimens while permanent strain and cumulative AE events increase just before fracture. The short-term after-cure process increases fatigue strength as well as static strength while the long-term after-cure process degrades the static strength and fatigue life. Fatigue strength decreases with increasing temperature for the virgin specimens without a hole. Fatigue life of open-holed specimens slightly decreases with increasing ambient temperature up to 200 °C. The FCP tests and in situ observation under loading revealed that fracture takes place in a brittle manner although stable crack propagation is observed in a few specimens. The SEM fractography indicates that pull-out of fibres was observed in all the specimens and that small resin particles were generated on the fibre surfaces of the specimens after the fatigue tests. © 2006 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.ijfatigue.2006.02.026

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

This paper presents impedance response to alternating current in a CFRP unidirectional (UD) laminate. Firstly, impedance and its phase angle for frequency ranging from 1 kHz to 1 MHz were measured for the specimens with various off-axis angles. Secondly, change in impedance during tensile loading was measured for the above specimens. Finally, a simple model was proposed to express impedance properties of a UD laminate using an equivalent electric circuit. The norm of impedance is almost independent of frequency for all off-axis angles. The phase angle is kept to be constant for the off-axis angle below 45°while it becomes negative at high frequency for the off-axis angle larger than 60°. This behavior is expressed by an equivalent circuit model introducing a capacitance element. Impedance response to mechanical strain is almost linear for all the off-axis angles. Piezoresistance behavior at low strain was characterized on the basis of the above model.

DOI： 10.6089/jscm.32.61

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記述言語：日本語   出版者・発行元：日本材料強度学会  

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（国際会議プロシーディングス）  

This paper describes temperature dependence of the resistance in a carbon fiber reinforced plastic (CFRP) unidirectional laminate and short carbon fiber reinforced plastics together with that in carbon fiber. Firstly, the resistivity of unidirectional laminates of a carbon fiber reinforced epoxy was measured at various off-axis angles at several temperatures ranging from 25 to 110°C. Secondly, the temperature dependence of short carbon fiber reinforced polyethersulphone (PES) resin composites fabricated by an injection molding process was measured at temperatures up to a load-deflection temperature of PES resin. Finally, the change in the resistance of carbon fiber was measured at temperatures up to 200°C. It is observed that the resistivity decreases with increasing temperature for all the off-axis angles of the unidirectional laminate. Similar resistance decrease with temperature was observed in the short fiber composites. These negative temperature coefficients of the two composites are presumed to be ascribed to intrinsic properties of constituent carbon fiber and contact resistance between fibers.

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

In this research, we did thermal cycle test, four point bend test, and the simulation analysis by finite element method (FEM) to DBC and AMC semiconductor substrate. We examined influence of thermal-residual stress on the life reliability of the substrates, and did the basic research for establishing a profitable strength evaluation method through the comparison with the two kinds of joint methods. It is clarified that the AMC substrate is more excellent than the DBC substrate from the viewpoint of strength and the longevity reliability of the semiconductor substrate.

DOI： 10.1299/jsmemecjo.2006.6.0_221

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本材料強度学会  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents strength in concrete reinforced with recycled and crushed carbon fiber reinforced plastic (CFRP) pieces. Mechanical properties such as compressive and flexural strength of CFRP reinforced concrete (CFRPRC) were evaluated and its fracture behavior was characterized. First, compressive and flexural tests of CFRPRC were conducted to investigate the effect of size and content of CFRP pieces on compressive and flexural strength and work of fracture in the flexural tests. Secondly, pull-out and peel tests were performed to estimate the adhesion strength at the interface. Finally, fracture surfaces were observed with an optical microscope and an electron probe micro analyzer to characterize fracture behavior and adhesion at the interface between CFRP and cement. Flexural strength increases and compressive strength increases slightly with increasing CFRP content. In the load-displacement curves in the flexural tests of CFRPRC specimens, large displacement is observed after maximum load. As a result, work of fracture of reinforced specimens is much higher than that of blank specimens. Good bonding at the interface due to anchoring effect was confirmed through the microscopic observation and the pull-out and peel tests. It is concluded that addition of CFRP pieces with appropriate size to concrete improves the flexural strength and work of fracture due to bridging effect. © 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compositesa.2004.12.009

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：一般社団法人日本機械学会  

This paper presents a shear lag analysis which enables us to calculate stress distribution in short fiber reinforced composites with soft resin coating at the end of fibers or fiber bundles. Stress distributions are obtained for the following two cases; the fiber is bonded (Case A) and debonded (Case B) with matrix resin at the fiber ends. Finite element analysis is employed to verify the validity of the present analysis. It is confirmed that shear stress at the fiber/matrix interface is relaxed by the soft coating resin while the axial stress in the fiber decreases in both cases. Width and shear modulus of coating resin have larger influence on relaxation of stress concentration than its length. Shear stress distribution predicted using the shear lag analysis is in fairly good agreement with the finite element calculation.

DOI： 10.1299/kikaia.71.543

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：金沢工業大学材料システム研究所  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper aims at characterizing the piezoresistance behavior in a carbon fiber reinforced plastics (CFRP) unidirectional laminate under mechanical loading. A two-dimensional model is proposed using a DC circuit equivalent to an electric resistance network in the laminate to predict the resistance change due to tensile loading. The surface resistivity and the initial gage factor are expressed as a function of the off-axis angle in the model. The piezoresistance behavior in the fiber and transverse directions is predicted based on the resistance model associated with the probabilistic failure of conduction paths parallel and perpendicular to the fiber direction. The measured resistance in these directions increases linearly within the small tensile strain, while it increases nonlinearly at large strains. The measured resistance in the off-axis directions exhibits remarkable nonlinearity except the first linear region. The predicted initial gage factor becomes the maximum at an off-axis angle of 12° and is in reasonably good agreement with the experimental results. © 2004 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compscitech.2004.07.005

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1299/kikaia.71.353

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

DOI： 10.1299/jsmebs.2004.17.0_409

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

DOI： 10.1299/jsmebs.2004.17.0_405

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

DOI： 10.1299/jsmebs.2004.17.0_407

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本材料強度学会  

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担当区分：筆頭著者,　責任著者   掲載種別：論文集(書籍)内論文  

This paper presents monitoring the strain in carbon fiber reinforced plastic (CFRP) laminates and CFRP/concrete structures by means of pizeoresistance properties of CFRP. First, the piezoresistance behavior in a CFRP unidirectional laminate under mechanical loading was characterized. A two-dimensional model was proposed using a DC circuit equivalent to an electric resistance network in the CFRP laminate to predict the resistance change due to tensile loading. The surface resistivity and the initial gage factor are expressed as a function of the off-axis angle in the model. Secondly, the strain in the concrete/CFRP structures was monitored using the piezoresistance behavior of the CFRP in order to verify the validity of the electric strain monitoring method. The resistance change together with the mechanical strain was measured in the CFRP laminate adhesively bonded to concrete under three-point flexural loading.

DOI： 10.1016/B978-1-85573-831-7.50154-1

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：愛媛大学  

The effects of environments of kerosene and water on the fatigue crack initiation and fatigue life in polycarbonate were investigated. The fatigue tests were carried out on circularly notched specimens under axial loading conditions. The environment of kerosene significantly affected the fatigue crack initiation, propagation and fatigue life. Namely, the fatigue crack initiation was promoted by kerosene, but the fatigue crack propagation was markedly restrained under kerosene, which resulted in longer fatigue life than that in air. The appearances of the specimen surface and the fracture surface suggest that the mechanisms of the fatigue crack initiation and propagation under kerosene are different from those in air. On the other hand, the fatigue crack initiation and fatigue life were not appreciably affected by the environment of water, which may be due to the low capacity for absorbing water in this material.

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

The effect of loading history on the electric resistance in CFRP unidirectional composites was experimentally investigated. First, monotonic tensile tests were conducted for on-axis and off-axis unidirectional specimens to measure the change in the electric resistance together with strain up to failure. The initial gage factor was theoretically derived from piezoresistivity as a function of the off-axis angle and was compared with the experimental results. Next, loading/unloading tensile tests as well as fatigue tests at low load levels were performed to measure the change in the electric resistance due to loading history. It was found that the electric resistance-strain curves for monotonic tensile loading exhibit nonlinear behavior after the linear region, and that the gage factor becomes negative at high strains for some off-axis directions. The initial gage factor becomes the maximum at the angle of 12 degrees according to the present model, and the predicted gage factors are in reasonably good agreement with the experimental ones. The permanent change in the electric resistance, which is not always ascribed to damage, was observed in all the directions after the loading/unloading as well as the fatigue loading.

DOI： 10.6089/jscm.29.217

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00234186877?from=CiNii

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本材料強度学会  

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人日本材料学会  

Fracture behavior under monotonic and cyclic loading in a glass fiber reinforced phenolic resin composite was experimentally characterized. First, monotonic tensile tests were conducted to measure stress-strain curves and acoustic emission (AE) behavior. Next, fatigue tests were performed to measure S-N curves for the virgin and after-cured specimens. Finally, fracture surfaces after both tests were observed by means of scanning electron microscopy (SEM). It is found that final failure abruptly takes place for both tests without showing visible damage on the surface of the specimens while permanent strain and cumulative AE events increase just before fracture. The after-cure process increases fatigue strength as well as monotonic tensile strength. Pull-out of fibers was observed on the fracture surfaces, however, it is difficult to determine the origin of fracture in both tests. The SEM fractography reveals that small resin particles are generated on the fiber surfaces in the case of a high cycle fatigue test.

DOI： 10.2472/jsms.52.407

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：金沢工業大学材料システム研究所  

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

Fracture and crack propagation behavior under cyclic loading in a glass fiber reinforced phenolic resin composite was experimentally characterized. Fatigue crack propagation (FCP) tests and in-situ microscopic observation under tensile loading were conducted using notched specimens. Pull-out of fibers was observed on the fracture surfaces, however, it is difficult to determine the origin of fracture in both tests. The FCP tests revealed that the crack propagating from the notch tip is longer in the specimen with higher fiber weight fraction, which shows damage tolerance of this material. The SEM fractography shows that small resin particles are generated on the fiber surfaces after the fatigue test.

DOI： 10.1299/jsmemecjo.2003.1.0_365

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents the influence of thermal history on transverse cracking in carbon fiber reinforced epoxy (carbon/epoxy) composites. At first, measurement of micro-Vickers hardness and Fourier transform-infrared spectrum (FT-IR) analysis of resin are conducted to investigate the effect of thermal history on resin. Secondly, shrinkage strain and transverse strength are measured for carbon/epoxy unidirectional laminates. Thirdly, the effect of temperature and duration of thermal history on transverse cracking in cross-ply laminates is experimentally investigated. The change in the residual stress due to post-cure is also estimated for the cross-ply laminates. Transverse cracking in the cross-ply specimens after thermal history initiates at lower stresses than the critical stresses in virgin specimens. It is found that thermal history increases the hardness of resin; however, it does not change the chemical structures in resin. The decrease in the strength is mainly caused by degradation of the fiber/matrix interface.

DOI： 10.1163/156855102762506308

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

Electrical properties of a carbon/epoxy composite are investigated. First, the electrical resistance such as contact resistance at electrodes and the conductivity of the specimens are measured for unidirectional and cross-ply laminates at temperatures ranging from 25 to 200°C. Secondly, the temperature rise due to Joule heat is measured for those laminates. Thirdly, the change in the electrical resistance during the heat treatment is investigated to monitor the post-cure of the composite. Finally, it is confirmed that the transverse cracking in a cross-ply laminate at -100°C is constrained by Joule heat.

DOI： 10.6089/jscm.28.228

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00161448543?from=CiNii

記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本材料強度学会  

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人日本材料学会  

This paper presents the effect of post-cure on mechanical properties of CF/Epoxy composites. At first, the shrinkage strain and the mechanical properties such as Vickers hardness of resin, transverse modulus and strength are measured for carbon/epoxy unidirectional laminates after four-hour thermal treatment (post-cure process) at temperatures ranging from 70℃ to 200℃. Then, the effect of post-cure temperature on transverse cracking behavior in a cross-ply laminate is experimentally investigated. The change in the residual stress due to post-cure is also estimated for the cross-ply laminate. Finally, the fracture surfaces of transverse cracks are observed using the scanning electron microcopy (SEM) to reveal the effect of post-cure on fracture behavior. It is found that the unidirectional laminate shrinks in only the transverse direction after the post-cure process. The hardness of the resin increases with increasing post-cure temperature below 150℃ while transverse modulus and strength are independent of post-cure temperature below 150℃. Transverse cracking in post-cured cross-ply specimens initiates at lower stresses than the critical stresses in virgin specimens. The transverse crack density is predicted by a Weibull&#039;s probabilistic failure model. It is deduced from SEM observation of fracture surfaces that the fiber/resin interface is weakened by thermal treatment that may lead to reduction in the transverse strength at 200℃.

DOI： 10.2472/jsms.51.518

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Transverse cracking behaviour in a quasi-isotropic glass/epoxy (GFRP) laminate loaded in flexure is studied experimentally and theoretically. A theory developed for cross-ply laminates is applied to a [0°/90°/-45°/45°]S quasi-isotropic laminate. An equivalent laminate is introduced to derive the Young's modulus of a cracked transverse ply on the basis of a shear lag analysis. The model predicts the flexural stiffness, the neutral axis position and the residual curvature as a function of the transverse crack density and the in-situ ply stress at first ply failure. Experimental results are obtained with the use of the applied moment - strain data in four-point flexural tests and compared with predictions. Time-dependent behaviour of the residual curvature is also investigated. The theoretical predictions are in reasonably good agreement with the experimental results. It is found that the decrease in the residual curvature after unloading is mainly ascribed to viscoelasticity of the material.

DOI： 10.1023/A:1013861917143

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

DOI： 10.1299/jsmezairiki.2002.0_113

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：愛媛大学工学部  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：日本材料強度学会  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

A model is developed to predict the transverse crack density and strain response in a cross-ply laminate under monotonic, bilinear and constant loading. First, the strain response of the cross-ply laminate due to transverse cracking is presented based on the viscoelasticity theory and shear lag analysis. The transverse crack density is given as a function of both time and stress using a probabilistic failure concept. Secondly, monotonic tensile tests, bilinear tensile tests and constant load tests of cross-ply laminates are carried out to measure the strains and transverse crack density. A few parameters necessary for the probabilistic function are determined from the monotonic tensile tests at various stress rates. Finally, good agreement of strains and crack density in bilinear and constant load cases between experimental results and predictions verifies the validity of the present model.

DOI： 10.1163/15685510152546358

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

An analytical model is proposed for predicting creep and recovery behavior of a quasi-isotropic laminate having transverse cracks in transverse layers. The analysis is established on the basis of a shear lag analysis in conjunction with a viscoelasticity theory. The strain is obtained in the Laplace transformed space and its original function is calculated by means of a numerical inverse Laplace transform technique. Creep and recovery tests are conducted for a quasi-isotropic glass/epoxy (GFRP) laminate with and without transverse cracking at a room temperature. The predicted strain response is in reasonably good agreement with experimental results. © VSP 2002.

DOI： 10.1163/156855102753613318

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）  

The effects of hygrothermal conditions on damage development in quasi-isotropic carbon-fiber/epoxy laminates are described. First, monotonic and loading/unloading tensile tests were conducted on dry and wet specimens at ambient and high temperatures to compare the stress/strain response and damage development. The changes in the Young's modulus and Poisson's ratio were obtained experimentally from the monotonic tensile tests. The critical stresses for transverse cracking and delamination for the above three conditions are compared. The delamination area is measured by using scanning acoustic microscopy (SAM) at various loads to discuss the effects of delamination on the nonlinear stress/strain behavior. Next, the stress distributions under tensile load including hygrothermal residual stresses are computed by a finite-element code and their effects on damage initiation are discussed. Finally, a simple model for the prediction of the Young's modulus of a delaminated specimen is proposed. It is found that moisture increases the critical stresses for transverse cracking and delamination by reducing the residual stresses while high temperature decreases the critical stresses in spite of relaxation of the residual stresses. The results of the finite-element analysis provide some explanations for the onset of transverse cracking and delamination. The Young's modulus predicted by the present model agrees with experimental results better than that predicted by conventional models. © 1999 Elsevier Science Ltd.

DOI： 10.1016/S0266-3538(99)00088-3

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

A creep model is established for a cross-ply laminate in which the transverse crack density is increasing. Viscoelasticity theory and shear lag analysis are employed for this creep model and the transverse crack density is expressed as a function of both time and stress, based on aprobabilistic failure model. The creep compliance of the cross-ply laminate is determined from creep tests of [90°8] specimens. The creep strain and transverse crack density of [0/90°3]s cross-ply laminates are measured during the creep tests and predictedcreep strains using the present model agree well with the experimental ones. © 1999 Taylor & Francis Group, LLC.

DOI： 10.1163/156855199X00191

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

The evolution of transverse cracking in a cross-ply laminate which deforms viscoelastically is investigated. A model predicting the strain under creep loading is established by a combination of the viscoelasticity theory, shear lag analysis and delayed failure concept. The creep strain and transverse crack density of the cross-ply laminates are measured during creep tests. Two stages of time for transverse cracking are observed in the creep tests. Predicted creep strains using the present model agree well with the experimental ones.

DOI： 10.1177/073168449901801305

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：九州大学応用力学研究所  

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：九州大学応用力学研究所  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Quasi-isotropic Carbon/Epoxy laminates under tensile loading are investigated to understand the effects of temperature on stress-strain response and damage progress including the interlaminar delamination growth behavior. The material system used is T800H/3631 and the stacking sequence is quasi-isotropic [0°/45°/-45°/90°]s. The transverse crack behavior is microscopically observed and its density is quantitatively measured by using an optical microscope under various loads at different temperatures, i.e., low (-100°), room (25°) and high (150°) temperatures. The interlaminar delamination growth behavior is non-destructively examined by a scanning acoustic microscope (SAM). It is found that nonlinearity observed in the stress-strain response is caused by the large scale interlaminar delamination throughout the length of the specimen. The transverse crack propagation and interlaminar delamination growth behavior are obviously affected by the temperature environments. Characteristic transverse crack formation at the edge of -45° layer under -100°C is pointed out and its mechanism is discussed with the use of shear coupling of an off-axis lamina.

DOI： 10.2472/jsms.47.599

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担当区分：責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人日本材料学会  

Fracture mechanisms in randomly oriented discontinuous carbon fiber reinforced borosilicate glass matrix composites are experimentally characterized. Two types of composite specimens with identical constituents but different microstructure were produced. The first type shows the three-stage behavior in the tensile stress-strain curve. In the second type which has the initial cracks, the stress-strain response is almost linear, but the initial Young's modulus is lower than that of the first type. Monotonic and static cyclic tensile and four point bend tests are conducted on those two specimens to measure the microcrack density, Young's modulus and Poisson's ratio as a function of applied strain. The experimentally determined crack density is used to estimate the interfacial shear stress. In the bend tests, evolution of microcracking on the tensile surface and through the thickness has been studied. Acoustic emission (AE) during the tests is monitored to understand the fracture mechanisms. It is proved that the difference in fracture mode between the two specimens is due to the difference in microstructure and the presence of initial defects. The AE behavior shows good correlation with the evolution of microcracking and can explain the fracture processes. Young's modulus can be a damage parameter to estimate the microcrack density. Microcracking during the flexural tests begins on the tensile surface and the cracks progress gradually towards the neutral axis.

DOI： 10.2472/jsms.47.406

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：JAPAN SOCIETY FOR COMPOSITE MATERIALS  

Effects of moisture on the stress-strain response and damage progress of quasi-isotropic CF/ Epoxy laminates ([0°/45°/-45°/90°]s) are presented. Tensile tests are conducted for both dry and wet specimens to compare the stress-strain behavior and the damage processes between them. The transverse cracking and delamination are microscopically observed and quantitatively measured at various loads. Macroscopic residual hygrothermal stresses are calculated by using the classical lamination theory to discuss those effects on damage initiation. The Young's modulus and Poisson's ratio of specimens with edge delamination are predicted on the basis of a modified delamination model and compared with experimental results. From the above experiments and calculations, it is proved that nonlinearity observed in the stress-strain response is attributed to the large scale edge delamination throughout the length of the specimen. The moisture increases the critical stresses for transverse cracking and delamination by reducing the residual stresses, while it decreases the stress of the transverse extension of edge delamination along the width. The modified delamination model gives better agreement with experimental results than the conventional one.

DOI： 10.6089/jscm.24.20

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その他リンク： https://jlc.jst.go.jp/DN/JALC/00054413665?from=CiNii

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents recent non-destructive testing results obtained from the inspection of delaminated quasi-isotropic carbon fibre reinforced plastic materials. Inspections were carried out using three different non-destructive testing methods; eddy current, ultrasonic C-scan and scanning acoustic microscopy. The results achieved for each method, in terms of delamination detectability, ease of inspection and signal interpretation, are described and their advantages and limitations discussed. Although a correlation of the information gathered with the three methods can be observed, it appears that both eddy current testing and ultrasonic C-scan provide a more complete assessment of the structural integrity of the component than scanning acoustic microscopy.

DOI： 10.1177/073168449801700502

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記述言語：日本語   掲載種別：研究論文（大学，研究機関等紀要）   出版者・発行元：九州大学応用力学研究所  

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents the effect of strain rates on nonlinear deformation behavior of CFRP composites. An elastic-plastic constitutive model is developed on the basis of both a complementary elastic energy function and a plastic potential, assuming that linear elastic deformation occursin the fiber direction and that nonlinear strain in the shear direction is decomposed into nonlinear elastic strain and plastic strain. A one-parameter and a two-parameter plastic potential are employed to describe post-yielding behavior of composite laminae. Nonlinear elastic shear strainis measured by means of loading/unloading tensile tests of [±45°]s specimens. Off-axis tensile tests are performed to obtain the universal effective stress-effective plastic strain relation under monotonic loading. It is shown that rate-dependence of effective stress-effective plasticstrain relation can be explained by determining anisotropy parameters of the plastic potential as functions of initial effective plastic strain rate. © 1997 VSP.

DOI： 10.1163/156855197X00067

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

Fracture mechanisms of discontinuous carbon-fibre-reinforced glass matrix composites were experimentally studied for specimens with initial damage induced by thermal shock. First, matrix cracking due to thermal shock was observed using both optical microscopy and scanning acoustic microscopy (SAM) to reveal the damage state. Secondly, tensile stress-strain behaviour and acoustic emission during tensile tests were measured for specimens with and without thermal shock. The progress of microscopic damage during tensile loading was also investigated using both replica and in-situ SAM techniques. Finally, macroscopic transient thermal stresses during thermal shock were calculated using finite-element analysis. It is proved that the fracture process of the composite specimen with thermal-shock-induced cracks is different from that of the virgin specimen. This difference in fracture processes is attributed to the difference in the evolution of matrix cracking, which is affected by pre-existing microcracks in the matrix.

DOI： 10.1023/A:1018612421976

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

This paper presents the effects of moisture content on nonlinear stress-strain behavior of CFRP composites. First, a plane-stress elastic-plastic constitutive model is newly developed based on a fourth-order complementary elastic energy function and a one-parameter plastic potential in which an anisotropy parameter changes with plastic deformation. Secondly, elastic constants, the anisotropy parameter and the effective stress-effective plastic strain relation are determined at various moisture contents for both the present model and the conventional model where the anisotropy parameter is constant. Finally, the above results are utilized to predict the off-axis stress-strain response. The transverse and shear elastic moduli decrease with increasing moisture content, and the anisotropy parameter and the effective stress-effective plastic strain relation also vary with moisture content. Off-axis stress-strain curves predicted by the present model agree with experimental results better than those predicted by the conventional model.

DOI： 10.1177/002199839703100601

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担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：社団法人日本材料学会  

This paper presents the effect of temperature on the nonlinear tensile stress-strain behavior of carbon fiber reinforced epoxy composites(CF/Epoxy). A two-dimensional elastic-plastic constitutive equation is developed using both a fourth-order complimentary energy function and a second-order one-parameter plastic potential, assuming that linear elastic deformation occurs in the fiber direction and anisotropy parameters change with plastic deformation. Monotonic and loading/unloading tensile tests on the on-axis and off-axis specimens at various temperatures are carried out to determine the elastic constants and plastic parameters of the effective stress-effective plastic strain relation. It is proved that nonlinearity in the transverse direction and the transverse-shear coupling is due to plastic deformation, while nonlinearity in the shear direction is ascribed not only to plasticity but also to nonlinear elasticity. The elastic constants in the transverse and shear directions and the plastic parameters are significantly affected by temperature. The off-axis tensile stress-strain curves predicted by using the present model show better agreement with the experimental results than those predicted by using Sun and Chen&#039;s model.

DOI： 10.2472/jsms.45.478

Scopus

J-GLOBAL

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

Fracture mechanisms of discontinuous carbon fiber reinforced glass-matrix composites were experimentally studied for specimens with and without thermal shock induced damage. Matrix cracking due to thermal shock was observed using both optical and scanning acoustic microscopes (SAM). Tensile stress-strain behavior and acoustic emission (AE) properties during tensile tests were measured for specimens with and without thermal shock. Matrix cracking during tensile tests was microscopically observed using both replica and in-situ SAM technique to reveal the damage progress. Difference in fracture process between virgin ad thermally-shocked specimens was identified, based on AE measurements, replica technique and in-situ SAM observation.

Scopus

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）  

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記述言語：日本語   出版者・発行元：一般社団法人日本機械学会  

CiNii Books

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：日本複合材料学会  

CiNii Books

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掲載種別：書評論文，書評，文献紹介等   出版者・発行元：The Society of Materials Science, Japan  

DOI： 10.2472/jsms.60.S12

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記述言語：日本語   掲載種別：研究発表ペーパー・要旨（国際会議）   出版者・発行元：日本複合材料学会  

CiNii Books

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記述言語：日本語   出版者・発行元：強化プラスチック協会  

CiNii Books

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記述言語：日本語   掲載種別：会議報告等   出版者・発行元：日本複合材料学会  

CiNii Books

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記述言語：日本語   出版者・発行元：社団法人日本材料学会  

CiNii Books

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