The Distribution of Microstructure and Mechanical Properties of Carbon-Carbon Composites

The effect of microstructure and its distribution of pyrolytic carbon in different deposition stage in carbon-carbon composites infiltrated by multi-factor physical fields chemical vapor infiltration (CVI) on the mechanical has been studied by polarized -light microscopy, Raman spectra, scanning electron microscope and three-point bending tests. The temperature and the change of the [AS/VR]-ratio with progressive infiltration are key parameters for the formation of microstructure and its distribution of pyrolytic carbon around the same fiber. SL pyrolytic carbon corresponds to brittle failure mode and smooth two-step fracture surface due to its low and uniform texture，although the abnormal graphitization occurs in the carbon fiber near the fiber/matrix interface. In contrast, RL matrix can function for achievement of nonbrittle fracture behavior with a zig-zag-like fracture surface and a relatively high value of flexural strength due to high and nonuniform texture.