Effect of carbon particle and carbon fiber on the microstructure and mechanical properties of short fiber reinforced reaction bonded silicon carbide composite

Variation of microstructure and mechanical behavior was investigated with the content increase of carbon particles and carbon fiber in the reaction bonded silicon carbide composites. The composites were prepared by slip casting and liquid silicon infiltration. The bulk density is raised with the increase of carbon black due to the formation of fine β-SiC particles. The flexural strength increases for the reduction of residual Si and the formation of SiC framework; whereas a very high carbon content reduces the flexural strength. The fracture toughness is controlled by the contents of carbon particle and carbon fiber. Thus, fiber debonding, fiber pullout and crack deflection are considered as the main toughening mechanisms. Annealing treatment can effectively improve both the flexural strength and fracture toughness. An increase by 49% of fracture toughness is obtained. A series of structural models are proposed to illustrate the structure changes of carbon fiber.