Effect of resin impregnation on the mechanical properties of C/C composites

impregnation was used to densify carbon fiber preforms after they had been densified by chemical vapor deposition (CVD). The characteristics of mechanical properties for self-fabricated composites was compared with products obtained from the British Dunlop company and the American Bendix company. The results show that the compressive strength and the flexure strength of the composites are far above those of the foreign products, the interlaminar shear strength is also higher. The flexure strength and the interlaminar shear strength of the composites increase with increasing CVD carbon in the composites when the CVD density of the composites is not more than 1.45 g/cm(3) and the flexure modulus exhibits a maximum at a CVD density of the composite of 1.06 g/cm(3). At the same time the fracture surface of the composites was studied using SEM. The results show that the fracture of the composites impregnated by resin only is brittle, while the fracture of the other composites is pseudo-ductile type with increased ultimate strength, which indicates that the resin is not appropriate for impregnating the performs in the initial process due to the strong bonding between resin carbon and the carbon fiber.