Thermal expansion property of carbon/carbon composite

The thermal expansion of carbon/carbon composite from room temperature to 1300°C was measured by using a Netzsch DIL 402C dilatometer. The influences of heat treatment, the preform architecture and the environmental temperature on thermal expansion were investigated. The results show that the graphitic flat-layered structure crystallites of pyrocarbon are arranged on the surface of the carbon fiber, and grow around the carbon fiber in the form of a ringed multilayer structure. Therefore, the thermal expansion is anisotropic and is higher in perpendicular direction than parallel direction to fiber. The graphitization degree of carbon/carbon composite is enhanced with the increasing of the heat treatment temperature, at the same time, the space between graphite crystallite layers decreases and van der Waals forces between the layers increase. The coefficient of thermal expansion decreases with the heat treatment temperature increasing. With the environmental temperature increasing, the coefficient of thermal expansion increases first and then decreases with a peak value at 1200°C.