PROCESS - MICROSTRUCTURE RELATIONSHIPS OF CARBON-CARBON COMPOSITES FABRICATED BY ISOTHERMAL CHEMICAL-VAPOR INFILTRATION

Carbon/Carbon composites consist of a fibrous carbon reinforcement in a carbonaceous matrix. In this paper, a chopped pitch based carbon fib er phenolic resin was consolidated and carbonized to have an open poro sity of about 30 percent. This porous composite was densified up to an open porosity of about 15 percent with pyrolytic carbon derived from methane gas in a low pressure chemical vapor infiltration (CVI) reacto r. The aim of present study is to investigate the effect of processing parameters on the microstructure and infiltration uniformity of pyroc arbon. The gas flow velocity, reaction pressure multiplied by gas flow rate, was found to have a significant effect on the infiltration unif ormity. The lower gas velocity was also found to be advantageous in pr oducing a uniform deposit of pyrocarbon through the substrate thicknes s. The pyrolytic carbon on the surface and through the thickness of po rous composite was observed by polarized optical microscope and scanni ng electron microscope (SEM).