Stress-oxidized behaviors and mechanisms of C/SiC composites at elevated temperatures and stress levels

The C/SiC composite is one of the most promising materials for applications in the aerospace sector. The thermal-mechanical-chemical coupling environment has a significant influence on the mechanical properties of the C/SiC composite. However, in the high-temperature atmosphere, the fixture is susceptible to damage, the sample softens, and the slag is removed, resulting in difficulties in developing the stress-oxidized experiments and characterizing the oxidation behavior of the C/SiC composite. In this study, a new characterization parameter, the oxidized volume (%) per min, was developed to quantify the stress-oxidized behavior of the tensile and compressive samples at different temperatures for different oxidation times. Two oxidation damage modes were found. The oxidation kinetics models of stress-oxidized samples were established. The results indicate that tensile stress promotes the oxidation, while compressive stress first inhibits and then promotes the oxidation of the C/SiC composite. The competitive mechanism between the reduced area of fiber pores and the increased matrix cracking determines the stress-oxidized trend of the C/SiC composite. The thermal exposure area is a key factor affecting the oxidation behavior of the C/SiC composite. This study offers valuable insights into the antioxidant strategies and thermal protection of C/SiC composites.