Carbon Matrix Composites Research Articles

The effect of chemical-vapor-deposition conditions on the properties of carbon-carbon composites

Properties are given for as-deposited and heat-treated carbon-felt, carbon-matrix composites infiltrated at deposition temperatures of 1100 and 1400°C, and pressures of 20 and 630 Torr. A thermal stress figure of merit was calculated for each material, with the heat-treated composite infiltrated at 1400°C and 630 Torr yielding the highest value. As with most graphitizing carbon materials, heat-treatment resulted in a decrease of the flexural strengths and moduli. The strength-to-modulus ratios, however, increased, being highest for deposition conditions of 1400°C and 630 Torr. Heat-treatment also resulted in an increase in thermal conductivity and a decrease in thermal expansion. These changes were related to the degree of crystallinity and to the formation of cracks within the matrix.

Carbon-Felt, Carbon-Matrix Composites

Carbon-felt, carbon-matrix composites were prepared by the chemical vapor deposition of carbon within carbonized viscose-rayon substrates. The thermal and mechanical properties of these carbon-carbon composites were investigated over a wide range (9-46 v/o) of fiber volume percent. In creases in fiber content resulted in: (1) decreases in both total porosity and pore size, (2) filament and matrix reorientation, and (3) reduction of the pyrolytic carbon matrix sheath thickness. Fiber content, and its inter related effects, are correlated with significant changes in flexural and ten sile strength and modulus, thermal conductivity and linear thermal expansion.