Failure Mechanism of C/SiC Composites under Stress in Oxidizing Environments

Stressed oxidation testing on C/SiC composites in dry and wet oxygen environments under cyclic and constant stress was conducted in the present study. Experimental results and microstructures of fracture surfaces analyzed by SEM show that the C/SiC composites have a better oxidation resistance and a longer life under fatigue testing than under creep testing. In dry oxygen environment, the failure of C/SiC composites under creep testing is mainly due to the oxidation of carbon fibers. While in wet oxygen ambient, the fracture of C/SiC composites under creep testing is caused by the failure of SiC matrix because the water vapor accelerates the oxidation of SiC.