Abstract:

D-C/C composites fabricated by a rapid densification process-Liquid-Vaporized CVI were heat treated at various high temperatures. The microstructural change and graphitability of the pyrocarbon matrix were studied with X-ray diffraction (XRD) technology; changes in mechanical properties and fracture behaviour were correlated with scanning electron microscopy (SEM) observations of fracture surfaces, fiber and matrix microstructures, and fiber/matrix interfacial structures. It was confirmed from XRD that the interlaminar distance of (002) planes (d₀₀₂) decreased from 3.501Åto 3.376Å; the microcrystalline stack height (L_c) increased; flexural strength was found to decrease drastically, while interlaminar shear strength (ILSS) to increase obviously after graphitization, and at the same time, the fracture toughness to increase.

Key words: carbon/carbon composites, graphitization, mechanical properties, rapid densification, fracturebehavior, interfacial strength