of trichloromethyl silane and hydrogen raised to 900 u00b0 c in a ratio of h 2 ch 3 sicl 3 of 8 at a pressure of 10 mpa for 10 hours the thus obtained substrate is then shaped as indicated at 25 followed by densification with a view to forming a sic doped carbon matrix as indicated by block 26 in fig2 to this end the substrate undergoes vacuum impregnation by a phenolic resin of the resol type and onto which have been chemically grafted 10 silicone functions this impregnation takes place in vacuo pressure below 1 kpa the impregnated structure is then polymerized at atmospheric pressure to a temperature of 200 u00b0 c and then the crust is removed so as to take away excess resin this is followed by a pyrolysis of the resin in a neutral medium at about 800 u00b0 c in order to convert the cross linked polymer into hard coke vitreous carbon a subsequent heat treatment at between 1200 u00b0 and 1800 u00b0 c makes it possible to convert the si o bonds of the polymer into sic this treatment phase involving the impregnation polymerization pyrolysis and subsequent thermal treatment is carried out five times in succession the composite material then reaches a density of 1 45 to 1 5 after.