Materials System
Online ISSN : 2435-3159
Print ISSN : 2435-1520
ISSN-L : 2435-1520
Current issue
Displaying 1-7 of 7 articles from this issue
  • MOTOTSUGU TANAKA
    2025 Volume 42 Pages 1
    Published: March 12, 2025
    Released on J-STAGE: March 27, 2025
    JOURNAL FREE ACCESS
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  • Daichi HARUYAMA, Yoshiaki KAWAGOE, Tomonaga OKABE
    2025 Volume 42 Pages 3-20
    Published: March 12, 2025
    Released on J-STAGE: March 27, 2025
    JOURNAL FREE ACCESS
    The application of high-temperature and high-strength ceramic matrix composites (CMCs) to engine components, which is necessary for improving the fuel economy of aircraft, necessitates the enhancement of material properties and accurate predictions of structural strength. A comprehensive understanding of the mechanisms underlying fractures is crucial for accurate strength predictions. This study builds on a static tensile model for unidirectional CMCs, accounting for matrix cracks and fiber breakage, and on energy-based matrix and transverse crack growth models for cross-ply CMCs. Here, a novel periodic crack growth model that represents variations in the matrix and transverse crack growth was devised. In addition, a fiber breakage model was developed to account for the local effects in the vicinity of broken fibers and initial fiber damage. The stress–strain relationships and crack-density growth processes of unidirectional and cross-ply CMCs were compared through experimentation and analysis using the two aforementioned models. The local load-sharing model, which considers the local effects of broken fibers, could accurately represent stress–strain relationship in unidirectional CMCs, and the stress–strain relationship in cross-ply CMCs was accurately represented by adjusting the fiber breakage probability associated with matrix cracks rather than the initial fiber damage. The proposed models could quantitatively express the matrix crack density–strain relationship, and they accurately represent the trends of the transverse crack density–strain relationship.
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  • Yuki TSUJII, Natsuha IKETA, Keisuke IIZUKA, Satoru YONEYAMA
    2025 Volume 42 Pages 21-26
    Published: March 12, 2025
    Released on J-STAGE: March 27, 2025
    JOURNAL FREE ACCESS
    A method for measuring strain near the interface of dissimilar materials is proposed by combining finite element and global digital image correlation, which takes into account the finite element equation as well as image information. Using this method, the strains of a specimen with a dissimilar material interface are measured and its effectiveness is demonstrated. Unlike conventional local digital image correlation, this method can evaluate the strains near the interface of materials with different properties without averaging the strain within the strain window. Even in the vicinity of a delaminated interface between dissimilar materials, strain measurement is possible by using a model that allows separation of the elements of the interface without sharing nodes between the elements on both sides of the interface. Therefore, this method is expected to be applied, for example, to the evaluation of strains at the fiber-resin interface in CFRP cross sections using microscopic images, and to strength evaluation of various dissimilar materials.
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  • Masayuki NAKADA, Yasushi MIYANO, Yoko MORISAWA, Takumi MOTOHASHI, Koda ...
    2025 Volume 42 Pages 27-33
    Published: March 12, 2025
    Released on J-STAGE: March 27, 2025
    JOURNAL FREE ACCESS
    Our role in the Center of Innovation (COI) project of the Kanazawa Institute of Technology (KIT) was to evaluate the long-term durability of carbon fiber reinforced thermoplastic (CFRTP) structures developed for the project. Komatsu Matere Co., Ltd. has developed a CFRTP tension rod using pultrusion molding method, with a thermoplastic epoxy resin (TPEP) developed at Innovative Composite Center (ICC) of KIT. The results have already been put to practical use in various fields. As a specific target, a TPEP-impregnated carbon fiber strand (CF/TPEP strand), which is the basic unit of this CFRTP tension rod, was used for durability evaluation. Specifically, annealing effects on statistical creep life during the operating process for the CF/TPEP strand was evaluated statistically using the accelerated testing methodology (ATM) we have developed over many years. Results clarified that the strand’s statistical creep life is altered drastically by the change of viscoelasticity of matrix resin during operation when subjected to loads.
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  • Evaluation of Inhomogeneity and Applicability
    Sogo AOKI, Yasuo HIROSE, Keishiro YOSHIDA
    2025 Volume 42 Pages 35-40
    Published: March 12, 2025
    Released on J-STAGE: March 27, 2025
    JOURNAL FREE ACCESS
    Recycled carbon fibers (rCF) are gaining attention as a promising means of reusing waste from carbon fiber-reinforced plastics (CFRP). However, one of the challenges is the variability in fiber surface and mechanical properties caused by the pyrolysis process conditions during the recycling process. In particular, the influence of these inhomogeneities on the mechanical properties and failure behavior of materials made by rCF has not been fully understood. In this study, the surface condition of rCF controlled by pyrolysis conditions was observed and its mechanical properties when molded into an in-plane isotropic material with an epoxy resin matrix evaluated. Additionally, the possibility that interlaminar crack suppression behavior, caused when localized high-rigidity regions exist at the fiber bundle interfaces, which might resemble the mechanisms of crack arresters in CFRP laminates was explored. As a result, these investigations turned out the applicability of rCF as a crack arrester and provided design guidelines, as well as identify challenges related to expanding the use of rCF.
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  • Asuka OSHIMA, Sogo YASUDA, Tadashi SAKUMA, Keishiro YOSHIDA, Yasuo HIR ...
    2025 Volume 42 Pages 41-47
    Published: March 12, 2025
    Released on J-STAGE: March 27, 2025
    JOURNAL FREE ACCESS
    Sandwich composites are widely used in load-carrying structures and there is a need for a testing method that will allow for qualitative and quantitative assessment of the bond between the face-sheets and the core. The sandwich single cantilever beam (SCB) test has attracted attention as one of the best candidates for evaluating the debond fracture toughness between face-sheet and core in sandwich panels under mode I type loading. In the sandwich SCB test, when the bending stiffness of the face sheet is low and the debond fracture toughness between the face-sheet and the core is high, the deflection of the face-sheet may become large to a degree that the assumption of small deformation does not hold. Regarding the theoretical analysis of sandwich SCB test, a beam on elastic foundation model has been proposed. However, the incorporation of large deformation effect into the theoretical analysis model has not yet been thoroughly investigated. In this study, sandwich SCB test by using specimens with thin face-sheets is conducted and the nonlinear load-deflection behavior which is possibly caused by the effect of large deflection of loaded upper face-sheet is confirmed. The finite element analysis (FEA) including geometric nonlinear effect is conducted and it is confirmed that the nonlinear behavior predicted by the numerical analysis generally agrees with the test result. Furthermore, to theoretically analyze the sandwich SCB test specimen including the large deflection effect, an analysis method which incorporates the ‘elastica’ solution into the beam on elastic foundation model is used. The result of the theoretical analysis agrees well with that of FEA. It is suggested that the theoretical analysis employed in this study has the potential for both qualitative and quantitative evaluation of the sandwich SCB test which includes the effect of large deflection of loaded upper face-sheet.
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  • M. J. Mohammad FIKRY, Masaru IRITA, Shinji OGIHARA, Masahiro ARAI
    2025 Volume 42 Pages 49-59
    Published: March 12, 2025
    Released on J-STAGE: March 27, 2025
    JOURNAL FREE ACCESS
    This study investigates two aspects of discontinuous carbon fiber-reinforced thermoplastic (CFRTP) manufactured using long fiber thermoplastic-direct (LFT-D) method: the fiber volume fraction and orientation, and the material’s damage behavior during tensile loading. Fiber content and orientation were quantified using cross-sectional images processed through binarization and ellipse fitting. Fiber bundles, with random size and position, were observed in areas of high fiber content, reflecting the inherent challenges of controlling parameters in the LFT-D process. Orientation analysis revealed a predominance of in-plane fiber alignment, indicating superior tensile performance in the in-plane direction but reduced strength out-of-plane. These findings provide insights into the material’s structural characteristics, while a separate evaluation focuses on its damage behavior under mechanical loading. In-situ tensile testing and scanning electron microscope observation revealed that cracks initiated at resin-rich regions and notch tips, propagated through resin-rich areas, and followed fiber bundle orientations, ultimately leading to failure. Observations of fiber pullout and interfacial debonding emphasized the importance of improving fiber-resin adhesion to enhance mechanical performance. These findings highlight the critical influence of fiber distribution and interfacial bonding on the mechanical behavior of CFRTP materials.
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