Abstract: The invention relates to a method for the treatment of silicon carbide fibers, comprising a step involving the chemical treatment of fibers with an aqueous acid solution containing hydrofluoric acid and nitric acid but free of acetic acid in order to remove the silica present on the surface of fibers and to form a layer of microporous carbon. The invention also relates to a method for the production of a fibrous preform, comprising the formation of a fibrous structure comprising treated silicon carbon fibers and the use of said preform for the production of a part made from composite material.

Abstract: The invention relates to a method for the treatment of silicon carbide fibres, comprising a step involving the chemical treatment of fibres with an aqueous acid solution containing hydrofluoric acid and nitric acid but free of acetic acid in order to remove the silica present on the surface of fibres and to form a layer of microporous carbon. The invention also relates to a method for the production of a fibrous preform, comprising the formation of a fibrous structure comprising treated silicon carbon fibres and the use of said preform for the production of a part made from composite material.

Abstract: In a process according to the invention, before a carbon/fiber ceramic matrix is densified, the carbon fiber reinforcement material is subjected to a thermal treatment in a non-oxidizing environment at a temperature greater than 1300.degree. C. and less than 2200.degree. C., to act on the bonding between the fibers and the matrix. If a preform of the carbon fiber reinforcement material is formed prior to densification by a matrix, then the thermal treatment may be performed on the preform, prior to densification by the matrix. If the matrix is densified by chemical vapor infiltration inside a furnace, then the thermal treatment may be performed inside the infiltration furnace prior to the densification. The thermal treatment achieves a significant improvement in the strength of the resulting composite material.