Tensile Strength of Carbon–Carbon Composites: II – Effect of Heat Treatment Temperature

Abstract

The effects of heat treatment temperature, HTT, on the tensile strength (u) of PAN-based carbon-fiber-reinforced carbon matrix composites (C–Cs) were examined. In order to understand the mechanisms yielding variation of the tensile strength, the distribution of fiber strength and the interfacial strength between the fiber and the matrix were also determined as a function of HTT. The us of the C–Cs and the PAN-based-fiber was found to decrease with increasing HTT. The degradations of the fiber strength proceeded with distortion of the fiber cross section and reduction of the fiber diameter. The interfacial strength slightly decreased with increasing HTT. The tensile strength of C–Cs is generally enhanced by the reduction of the interfacial bonding strength. Thus, the interfacial change is not a main source of the strength degradation. Finally, a comparison of u between two types of C–Cs, showed that the only difference was reinforcing fibers and led to the conclusion that the primary factor yielding the degradation of C–C strength by HTT was the fiber degradation.