The constituents in a CC composite do not oxidize at the same rate. At temperatures between 650-800C the matrix carbon oxidizes faster than the more graphitic carbon fibers. The oxidation apparently starts at fiber/matrix interface, proceeds to the matrix and then the fibers.
The rate of oxidation for a CC composite is reported to be higher than the rate for pyrolytic or amorphous carbon and composites made from PAN fibers are more reactive than composites made from pitch fibers. This lower reaction rate may be related to the more graphitic structure that can be attained in the pitch fibers.
The heat treatment temperatures used in the fabrication of a CC composite can affect oxidation. The reason for the effect is unclear but may be related to retained impurities.
Flow rate has been shown to affect the oxidation behavior of CC composite. Generally as the flow rate increases the oxidation rate also increases. Dependence of an oxidation rate on flow rate indicates that diffusion through a boundary layer is controlling.
Stresses on a sample during oxidation have also affected oxidation rates. Compressive stresses have little or no affect on the oxidation, while tensile stresses open pores and microcracks, which accelerate oxidation.