Recently developed substrateless continuous SiC filament was shown in the previous report to have strength properties equivalent to those of SiC filaments produced by chemical vapor deposition. As the next step to apply this filament to fiber reinforced metals, its reactivities with nine pure metals and five alloys were studied by powder metallurgy technique. The reactivities of the filament were mostly similar to those of chemical-vapor-deposited SiC filaments. Specifically an activation energy for reaction zone growth in titanium matrix was determined to be 49.4 kcal/mol which agreed with reported values. The filaments were successfully incorporated into aluminum matrix by the developed powder slurry-liquid phase pressing technique. Tensile strength of the composites agreed well with the rule-of-mixture strength for the filament volume fraction up to about 20%.

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The interlaminar shear strength and the flexural strength are usually determined by means of the three-points flexural test because of its simplicity. These strengths are defined as the maximum stress values predicted by elementary beam theory based on Euler-Bernoulli hypotheses. However, in the three-points flexural test on composite materials, especially with high anisotropy, the stress distribution in the vicinity of central loading point is not so simple as that given by the elementary beam theory. In the present paper, the multi-axial stress distributions in the three-points flexural test and the influences of various factors such as span/depth ratio and shape of load distribution on beam are analysed in order to discuss the validity of these fracture strengths and to propose a reasonable testing method. Consequently, it is found that the local stresses at the maximum bending moment region are very high, and that, in the case of small span/depth ratio, the stress distribution differs extremely from that based on the elementary beam theory. The validity of these analytical results is confirmed by using the finite element method analysis. The initial failure behaviors can be explained by these analytical results.

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This paper presents the results of the experimental investgation of the static and dynamic mechanical properties of laminated carbon fiber reinforced plastics (CFRP). The composites consist of denatured epoxy resin MRX-3501, # 241, # 3130 and reinforced high strength type carbon fiber, PYROFIL-XAS made by Mitsubishi Rayon Co., CARBOLON Z-3 by Nippon Carbon Co., and TORAYCA T-300 by Toray Co. These Laminated CFRP plates were fabricated with 24 plies of [0°, 45°, -45°, 90°] sym. laminates; symmetry of plies is about the laminate midplane. Flexural fatigue test results on normal test pieces and on hydrated test pieces soaked in water for two weeks were compared. The results of flexural fatigue tests showed the ratio of the flexural fatigue strength at 10⁷ cycle to the static flexural strength to be 0.27-0.43. The fatigue strengths of normal test pieces not differ from that of hydrated test pieces in XAS/MRX-3501 and Z-3/# 241; however, they slightly differ in T-300/# 3130.

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In considering a failure process of inhomogeneous laminates with cutouts, differences between failure modes of individual layers should be taken into consideration because of its complexity in comparison to that of smooth laminates. In our research, a characteristic failure process of laminates with circular holes was simulated step by step by pursuiting decrease in rigidity caused by stress redistributions due to local failures in individual layers based on a finite element method. In order to clarify the effect of laminate constitutions on failure process of FRP laminates with circular holes, finite element failure process simulations were carried out on cross-plied and angle-plied laminates with circular holes under tension and in-plane shear. The simulated results were shown to be in good accordance with observed ones of FRP laminates. They were also helpful to explain the change of strain distributions around a circular hole due to proceeding of failures and to discuss the effect of laminate constitutions on decrease in apparent strength due to circular holes. In considering a failure process of inhomogeneous laminates with cutouts, differences between failure modes of individual layers should be taken into consideration because of its complexity in comparison to that of smooth laminates. In our research, a characteristic failure process of laminates with circular holes was simulated step by step by pursuiting decrease in rigidity caused by stress redistributions due to local failures in individual layers based on a finite element method. In order to clarify the effect of laminate constitutions on failure process of FRP laminates with circular holes, finite element failure process simulations were carried out on cross-plied and angle-plied laminates with circular holes under tension and in-plane shear. The simulated results were shown to be in good accordance with observed ones of FRP laminates. They were also helpful to explain the change of strain distributions around a circular hole due to proceeding of failures and to discuss the effect of laminate constitutions on decrease in apparent strength due to circular holes.

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