Environmental Performance Test and Analysis of SiC/SiC Composites

SiC/SiC ceramic matrix composites were prepared by polymer impregnation pyrolysis (PIP) process with domestic first-generation SiC fibers as reinforced phase and SiC ceramic as matrix phase. The structure and morphology of SiC ceramic matrix and SiC/SiC composites were investigated by means of XRD and SEM method. Furthermore, the mechanical properties of SiC/SiC composites after high temperature gas testing were investigated by flexural strength using three point bending testing. Results showed SiC/SiC composites have excellent mechanical properties at room temperature with bending strength of 330 MPa. However, obvious cracks and serious oxidation appeared after up to 150 hours of high temperature gas testing, and the mechanical properties dropped dramatically with the flexural strength retention rate less than 50%. The decrease of the mechanical properties and the occurrence of cracks of SiC/SiC composites were mainly attributed to the structure evolution and the oxidation intensification which might lead to instability of material properties and component structure. (paper)