Investigation of microstructure and flexural behavior for oxidation protection coated C/C composites

Mechanical properties of MoSi₂-SiC oxidation resistant coated C/C composites were investigated by three-points bending tests. The microstructure of coated C/C composites and flexural fracture surface, and the interface characteristics of C/C composites were investigated; the influences of oxidation protection coating and its process on the flexural mechanical behavior of these materials were analyzed. The results showed that with the progress of the coating process, SiC conversion layer was formed in the interfaces of carbon fiber/carbon matrix and fiber bundle/matrix, and open pores or gaps existing within the composites. On the other hand, the pyro-carbon matrix converted into SiC was easier than the carbon fiber. After infiltration process, the fracture behavior of C/C composite was changed. Also the correlation between microstructure and fracture behavior was discussed with the SEM results.