Fracture characteristics of carbon/carbon composites prepared by mix technics

2D carbon/carbon composites with different densities lapped with 3K-carbon cloth were fabricated by two-step technique of thermal gradient CVI and HPIC(High-Pressure-Impregnation-Carbonization). Flexural properties, fracture morphology of carbon/carbon composites were tested by comparing with carbon felt sealing composites. The results show that the strength and modular of C/C composite made by mix techniques are greater than those of graphite sealing material; Carbon/Carbon composites with high density showed brittle fracture behavior and fracture surface was almost flat while low density composites were inclined to tough fracture, but the samples with tough fracture showed that a lot of carbon fibers were pulled-out. The graphite sealing material showed brittle fracture obviously. Polarized microstructure shows that the blending organization was formed in composites, which increase the interface area and extend the crack diffuse distance.