EFFECT OF MATRIX TEXTURE ON TENSILE-STRENGTH AND OXIDATION BEHAVIOR OF CARBON-FIBER-REINFORCED CARBON COMPOSITES

Unidirectional carbon fiber reinforced carbon composites (C-C composit es) with different matrix textures were prepared from six matrix precu rsors. Two composites with an optically isotropic matrix showed tensil e strength and modulus values that increased on heat treatment of the samples at a high temperature. Composites with an anisotropic matrix, having preferred orientation parallel to fiber surface, were deformed due to shrinkage as the graphitic structure developed on heat treatmen t. This caused the fibers to be exfoliated from the anisotropic matrix , as a result of residual stresses generated by restriction of matrix shrinkage. The strengths of the composites with an anisotropic matrix were reduced after graphitization. On oxidation in a wet atmosphere, t he composites with an anisotropic matrix showed higher durability than those with isotropic matrices. The oxidation of the former composites was localized at the fiber-matrix interphase, but this effect was not observed with isotropic matrix composites.