Effect of oxidation time on fracture behavior of C/SiC composites at 800 C in air

The fracture behavior of C/SiC composites after oxidation treatment for different time at 800 degrees C in air was studied by in-situ test technology combining DIC, AE and X-CT. From results of fracture toughness tests, it can be found that with the increase of oxidation time, the stress intensity factor and the work of fracture show different trends, and the fracture mode after oxidation changes from quasi-brittle to ductile. Combined with AE clustering analysis and X-CT images obtained through in-situ load tests, the mechanism of the coupling effect of oxidation time, toughening behavior and C-phase consumption on energy dissipation is explained. In addition, long-term oxidation causes the crack initiation point to deviate from the prefabricated notch tip and the delamination damage, which may lead to the change of failure position and unexpected damage mode in the engineering structures.