Degradation behaviour of C/C composites by atomic oxygen irradiation

Erosion mechanisms of C/C composite and C/C-SiC composite (matrix modification for C/C composite using SiC) irradiated by atomic oxygen (AO) were studied by analyzing erosion morphology and mass loss rate. Thermal diffusivity coefficient, thermal expansion coefficient and flexural strength were determined before and after AO exposure test to discuss thermal physics and mechanics of AO damage. The results show that the erosion of C/C composite is the cooperation of chemical oxidation and mechanical erosion, which can be termed bombardment-induced surface chemical etching. The SiC components show good resistance to atomic oxygen erosion and hinder internal erosion. However, SiC components can also be damaged mechanically as the exposure time increasing. The mass loss rate of C/C composite is approximately proportional to the exposure time, while the mass loss rate of C/C-SiC composite is smaller than that of C/C composites and the increase of the mass loss rate slows down as the exposure time increasing. The changes of thermophysical property and mechanical property show that the overall performances of C/C and C/C-SiC have been changed to some extent after the AO exposure testing.