Effects of the crystallinity of polypropyrene (PP) and the surface treatment of glass beads (GB) on the elastic moduli of PP resins or GB/PP composites were investigated. High crystallinity type PP and general purpose type PP were used for the matrix resin. For the surface treatment of GB, n-hexadecyltrimethoxysilane was used as the coupling agent. The crystallinity of PP in PP or GB/PP specimens was controlled by the cooling condition after heat press molding. And the storage moduli of the specimens were measured by the dynamic viscoelasticity measurement. Results are summarized as follows. 1) Elastic moduli of PP and GB/PP specimens increase with the increase of the crystallinity of PP resin. 2) The surface treatment of GB hardly affects on the storage moduli of GB/PP specimens. 3) The elastic moduli of PP and GB/PP specimens can be predicted by the spherical particle filled model, taking into account the presence of the crystal parts which have no contribution to increase the elastic modulus.

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Measurement of the strength for composite strucures is very difficult, because these failure processes imply various failure modes till critical failure, for example, interlaminar delamination, matrixdestruction, interfacial fracture between fiber and matrix and fiber breaking. In this study, three-point bending simulations of four types quasi-isotropic composite laminates were carried out using a quasi-three-dimensional model. This proposed model is constructed of shell and beam elements which represented fiber and matrix, respectively. On the other hand, flexural experiments by AE measurement were carried out in order to evaluate the appropriateness of our analytical procedure. Comparing analytical and experimental results, the accuracy of the analysis is satisfactory. Moreover this model could simulate appearances of transverse crack and interlaminar delamination separately.

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This paper presents a lateral compressive analytial method of CFRP cylinders using the quasi-three-dimensional model. This numerical model is constructed by shell and beam elements which represent fiber and resin respectively. Namely the heterogeneity of composites is considered in the concept of this model. Using the quasi-three-dimensional model, the behaviors of [θ/-θ] _sym (θ=15, 30, 45, 60) CFRP cylinder subjected to the lateral compressive load are simulated, and compared with experimental results. On the other hand, these damage propagation process was investigated till the critical failure. Moreover a critical strength law is proposed. Therefore this model is effective for the estimation of the lateral compressive stiffness. For the damage propagation, the transverse crack and interlaminar delamination are simulated independently. Furthermore comparing the experimental critical strength, we confirm that the proposed strength law in this model is precise.

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Fiber-reinforced composite materials often exhibit nonlinear stress-strain behavior under the combined tension-compression and shear with respect to the transverse direction to the fiber. This paper focuses on the mechanical description of the nonlinear inelastic behavior of CFRP. In order to obtain fundamental data to elucidate the inelastic behaviors of the composite, quasi-static failure tests were firstly performed on unidirectional and symmetric angle-ply laminate tubes with different fiber orientations. Then, the flow rules proposed by Chow et al. were modified and developed to describe the non-linear mechanical behavior of symmetric angle-ply laminates under multi-axial loading. Comparison between the experimental data and the theoretical predictions showed that the proposed theory can appropriately describe the inelastic behavior of CFRP.

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