Influence of Carbon Fiber Heat Treatment on Fracture Toughness of 2D C / C-SiC Composites

In order to investigate the influence of carbon fiber heat treatment on the fracture toughness of 2D C /C-SiC composites via liquid silicon infiltration process,the carbon fiber was heat-treated at temperatures range from 600℃ to 1500℃ under vacuum. The fracture toughness was evaluated using single edge notched beam( SENB) test. The surface morphologies of C / C preform,C / C-SiC composites and the fracture surface were observed using scanning electron microscopy( SEM). The porosity and density were measured using the Archimedes method. The results indicate that the fracture toughness increases with increasing the heat treatment temperature of carbon fiber. The fracture toughness of composite reinforced with the 1200℃ heat-treated fiber is about 7. 9MPa·m1 /2,which is increases by 53% in comparison to that of the untreated fiber reinforced composite. The results of SENB test and structure show that the high fracture toughness in heat treated fiber reinforced composite is attributed to the strong fiber / matrix bonding strength,homogeneous distribution of SiC and high volume fraction of SiC in matrix.