Damage evolution in 3D C_f/SiC composites in stressed oxidation environments

The damage evolution in three dimensional carbon fiber reinforced silicon carbide (3D C_f/SiC) composites in a stressed oxidation environment was investigated by scanning electron microscopy in terms of generation and propagation of cracks. The results indicate that the main damages in 3D C_f/SiC composites in the stressed oxidation environments include cracking of SiC matrix, debonding and oxidation of pyrolytic carbon interphase, and fracture and oxidation of carbon fibers. The interphase and fibers are oxidized by oxygen through microcracks in the matrix. The fibers are elongated due to debonding and oxidation of interphase, which contribute to the propagation of cracks. The mutual promotion between the fracture of fibers and propagation of cracks provides the essential driving force for the crack extension.