Patent ID: 7052643

Claim:
A method of subjecting carbon fiber preforms to high temperature heat treatment and to densification by chemical vapor infiltration, the method comprising the steps of: placing the carbon fiber preforms in an enclosure; subjecting the preforms in the enclosure to a heat treatment at a temperature sufficient for eliminating all or nearly all metallic impurities contained in the carbon fibers while sweeping the enclosure with inert gas under low pressure; during the heat treatment, continuously extracting gaseous effluent containing metallic impurities through a first effluent outlet connected to an effluent exhaust circuit; at the end of heat treatment, closing the first gas effluent outlet so as to isolate the effluent exhaust circuit from the enclosure; interrupting sweeping of the enclosure with inert gas; and leaving the heat-treated preforms in the enclosure and subjecting them to densification by admitting a reagent gas into the enclosure through at least one reagent gas admission duct opening out into the enclosure, gaseous effluent being extracted through a second effluent outlet distinct from the first, said second outlet being closed during the heat treatment step.