Effects of random chopped fiber on the flexural strength and toughness of reaction bonded silicon carbide composite

Chopped carbon fibers were introduced into the SiC/C suspensions to enhance the mechanical behaviors of reaction bonded silicon carbide ceramics. The effects of fiber fraction on the flexural strength and fracture toughness were investigated. No preferred fiber orientation was observed on the fracture surface of the green body. This implies a homogeneous dispersion of chopped fiber in the composite. XRD analysis indicates a complete siliconization of both carbon particles and carbon fiber during liquid silicon infiltration. The flexural strength and fracture toughness increase with chopped fiber ranging from 10 vol.% to 30 vol.%. This improvement derives from the fiber pullout, fiber debonding as well as crack deflection. The consequent decline at fiber fraction of 40 vol.% is resulted from the siliconization of chopped fiber and the increase of residual silicon.