FORCED FLOW-THERMAL GRADIENT CHEMICAL-VAPOR INFILTRATION (FCVI) FOR FABRICATION OF CARBON/CARBON

Carbon/carbon composites with porosities as low as 7% were fabricated within 8-12 hours using the forced how-thermal gradient chemical vapor infiltration (FCVI) process. Performs consisting of 40 layers of T-300 plain weave carbon cloth were infiltrated with a feed containing a carbon source and a diluent. The carbon sources studied in the present work included propylene, propane, and methane and the diluent was hydrogen. Shorter processing times were obtained when propylene and propane were used as compared to methane. The highest deposition rate obtained in the present study was similar to 3 mu m/h which is more than an order of magnitude faster than the typical Value of 0.1-0.25 mu m/h for the isothermal infiltration process. In the infiltrated composites it was observed that the tows in a cloth were appreciably infiltrated, independent of their position in the preform. Whereas, the coating thickness between the tows and cloth layers strongly depended on the temperature, i.e. position within the preform.