Journal of the Japan Society for Composite Materials
Online ISSN : 1884-8559
Print ISSN : 0385-2563
ISSN-L : 0385-2563
Volume 33, Issue 6
Displaying 1-6 of 6 articles from this issue
  • Tomonaga OKABE, Kensuke ISHII, Masaaki NISHIKAWA, Nobuo TAKEDA
    2007 Volume 33 Issue 6 Pages 205-212
    Published: November 15, 2007
    Released on J-STAGE: August 11, 2009
    JOURNAL FREE ACCESS
    Tensile strength of unidirectional CFRP composites was predicted by the numerical simulation plus size scaling technique. The fiber strength distribution used in the numerical simulation was determined from the fragmentation process in a single fiber composite. Since the experimental data was obviously not fitted with the normal Weibull distribution, we fitted them with the Weibull of Weibull (WOW) model considering the statistical distribution of scale parameters of fiber strength in normal Weibull model. Moreover, the constitutive law of the matrix was derived from the stress-strain curves of the angle ply laminates utilizing the micromechanics approach proposed by Tohgo et al. Based on these parameters, we simulated the tensile fracture of unidirectional CFRP composites with the spring element model. The predicted tensile strength by the numerical simulation plus size scaling has a good agreement with the experimental data.
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  • Hiroshi SUEMASU
    2007 Volume 33 Issue 6 Pages 213-218
    Published: November 15, 2007
    Released on J-STAGE: August 11, 2009
    JOURNAL FREE ACCESS
    A damage growth mechanism in a hoop layer of a cylindrical portion of a composite pressure vessel was analytically studied. The cylindrical portion was produced by winding finite width prepreg tape, and made of two layers which consist of a circumferentially wound hoop layer and an almost axially reinforced base angle-ply layer. The fibers of the hoop layer were slightly inclined from the circumferential direction for the tape to be wound without gap and overlapping each other. So, the hoop layer forms a very low angle-ply laminate. High tensile strains generated in both axial and hoop directions due to the high internal pressure may produce matrix cracks in the full depth of the hoop layer, because the surface unevenness of the damage due to the different fiber angle is very small as the crack just initiates. However, the damage growth is not simple in this case because the unevenness increases with the crack growth without fiber breakages. The growth of uneven damage was examined through a fracture mechanical study based on the channeling crack assumption, but found to be difficult. It is concluded that the crack growth must accompany some fiber breakages or fiber peel-off from the cracked surface.
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  • Tomohiro YOKOZEKI, Toshio OGASAWARA
    2007 Volume 33 Issue 6 Pages 219-226
    Published: November 15, 2007
    Released on J-STAGE: August 11, 2009
    JOURNAL FREE ACCESS
    The energy release rate associated with crack growth in adhesive double cantilever beam (DCB) specimens, including the effect of residual stresses, was formulated using a beam theory. Because of the rotation of the unsymmetric arms in the adhesive DCB specimens due to temperature change, it is necessary to modify the evaluated fracture toughness of DCB specimens, particularly in the case of the large temperature change. In this study, it was shown that the difference between the apparent toughness and the true toughness due to the residual stresses can be calculated for the given specimen geometry and the thermo-mechanical properties, such as the coefficient of thermal expansion. The calculated difference of the energy release rates based on the present modification method is compared with that from FEM to verify the method. The residual stress effects on the evaluation of the adhesive fracture toughness are discussed.
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  • Tsuneo IMAI
    2007 Volume 33 Issue 6 Pages 227-231
    Published: November 15, 2007
    Released on J-STAGE: August 11, 2009
    JOURNAL FREE ACCESS
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  • Hajime KISHI
    2007 Volume 33 Issue 6 Pages 232-237
    Published: November 15, 2007
    Released on J-STAGE: August 11, 2009
    JOURNAL FREE ACCESS
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  • Tsuneo IMAI
    2007 Volume 33 Issue 6 Pages 238-242
    Published: November 15, 2007
    Released on J-STAGE: August 11, 2009
    JOURNAL FREE ACCESS
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