Strength and toughness improvement in a C/SiC composite reinforced with slurry-prone SiC whiskers

The present paper reports on the strength and toughness improvement in carbon-fiber reinforced silicon carbide (C/SiC) composites as a result of slurry-prone SiC whisker presence at varying concentrations. For whisker contents of 5 and 15 wt%, the SiC_w-C/SiC composite flexural strength was found to increase by 98.5% and 64.3%, respectively, from the whisker-free case while work of fracture increased by 209.8% and 179.0%, respectively. For the same respective whisker concentrations, porosity was found to decrease by 4.9% and increase by 19.4% compared to plain samples. The composites' interlaminar shear strength exhibited similar non-monotonic response with the property value for 5 wt% whisker-reinforced composites being higher by 12.5 MPa than the plain specimens and higher by 14.9 MPa than the composites with 15 wt% whisker content. Fiber pullout in SiC_w-C/SiC composites was considerably more prominent than in the whisker-free material and the corresponding mean pullout lengths were significantly longer than in plain specimens. The improvements in strength and toughness were attributed to the energy dissipation mechanisms of crack deflection, whisker bridging and pullout coupled with conventional fiber pullout.