The Nature of Silicon Carbide Phases Developed from Different Carbonaceous Sources and its Impact on the Microstructure of C _f /C‐SiC Composites

Friction surface evolution of carbon fibre reinforced carbon/silicon carbide (Cf/C-SiC) composites

“…Now, we believe that the following possibilities inside the silicon carbide might have led its surface more fragile than silicon: (a) the silicon carbide regions in the composite might have been weakly bonded as the grain boundaries were not purposely engineered in the LSI process, which could lead to a degradation of fracture toughness at the microstructure level, which was shown a possibility of less than 2.1 MPa m 1/2 by Padture and Lawn 22 ; (b) large residual tensile stress could exist on the grains boundaries due to the constraint on the growth of silicon carbide grains in LSI process and the thermal strains generated during cooling down from the silicon impregnation temperature, which are featured through the appearance of stacking fault inside the SiC grains. 23,24 This view has been demonstrated in a study on the wear resistance of alumina, where the damage resistance has little relationship with large crack propagation resistance, i.e. K IC measured by most methods, but a strong relationship with short crack energy releasing rate.…”