Method for manufacturing a part made of composite material using an adhesion promoter comprising a Lewis acid or a Lewis complex

A method for manufacturing a part made of composite material comprising:

• a) introducing an adhesion promoter into pores of a fibrous preform formed by yarns coated by a coating having —OH groups at its surface, the adhesion promoter being a Lewis complex or a Lewis acid, the Lewis complex adhesion promoter comprising a reactive structure Si of formula B1-X—H, where B1 is a Lewis base, the Lewis acid adhesion promoter comprising a reactive structure S2 of formula X—H with the atom X having an empty orbital, in these two alternatives, X designates boron or aluminium,
• b) grafting the adhesion promoter to the surface of the coating by addition on the —OH groups at the atom X,
• c) introducing a ceramic precursor resin into the pores of the fibrous preform, after the step of grafting the adhesion promoter,
• d) polymerising the introduced resin and bonding the grafted adhesion promoter to the resin by chemical reaction between these two compounds at the X—H bond of the grafted promoter, the polymerisation and the bonding being carried out by heating the fibrous preform into which the resin has been introduced,
• e) forming a ceramic matrix phase in the pores of the fibrous preform by pyrolysis of the polymerised resin.