Tribo-mechanical characterization of spark plasma sintered chopped carbon fibre reinforced silicon carbide composites

Short carbon fibre (Cf) reinforced silicon carbide (SiC) composites with 7.5 wt% alumina (Al2O3) as sintering additive were fabricated using spark plasma sintering (SPS). Three different Cf concentrations i.e. 10, 20 and 30 wt% were used to fabricate the composites. With increasing Cf content from 0 to 20 wt%, micro-hardness of the composites decreased ~28% and fracture toughness (KIC) increased significantly. The short Cf in the matrix facilitated enhanced fracture energy dissipation by the processes of crack deflection and bridging at Cf/SiC interface, fibre debonding and pullout. Thus, 20 wt% Cf/SiC composite showed >40% higher KIC over monolithic SiC (KIC≈4.51 MPa m0.5). Tribological tests in dry condition against Al2O3 ball showed slight improvement in wear resistance but significantly reduced friction coefficient (COF, μ) with increasing Cf content in the composites. The composite containing 30 wt% Cf showed the lowest COF.