Damage mechanisms of SiC-coated C/C composites subjected to cyclic loading in combustion gas environment

A SiC-coated C/C composite was subjected to cyclic loading in a combustion wind tunnel with flame temperature of 1300 °C. Both the ratchetting strain and hysteresis changes showed that the majority of damage was produced in the first 50 cycles, and then the rate of damage accumulation gradually approached a steady value as the cycles proceeded. Lamellar structure of the C/C composite was observed after oxidation, which was caused by the difference in reactivity between the carbon fiber and carbon matrix. Acoustic emission activities throughout the tensile tests of the cycled specimens showed that little damage was produced before the applied tensile load exceeded the maximum history load of the cyclic loading tests.