Thermal shock resistance of SiC compositionally graded C/C composites

Thermal shock resistance of SIC compositionally graded carbon fiber reinforced carbon composite (CFC) materials that are composed of a CVD SiC layer, a SiC/C graded layer and a CFC substrate was studied by thermal shock tests in air. Two types of CFCs were used: 1-D continuous fiber reinforced and 2-D felt reinforced composites. It was found that the SIC/C graded layer was to some extent effective to increase the resistance and that its effectiveness was larger when a difference in thermal expansion coefficient (CTE) between a substrate and beta-SiC was smaller. The degree of an improvement of the thermal shock resistance for CFC substrates was lower than that for isotropic graphite substrate. The difference was attributed to the original cracks in CVD SiC layers on CFC substrates. (C) 1998 Elsevier Science B.V. All rights reserved.