Fire protection of a part made of a three-dimensional woven composite material

A fire protection method for a part of a gas turbine engine, made of a composite material comprising a main fiber reinforcement densified by a main matrix, the main fiber reinforcement being three-dimensionally woven and the main matrix being polymerized, wherein the part of the gas turbine engine is a fan casing, a surface of the fan casing to be protected against fire comprising an upstream radial face and a downstream radial face of an upstream flange of the fan casing, an outer face of a barrel of the fan casing and an upstream radial face of a downstream flange of the fan casing, the upstream flange of the fan casing having a top having an axial length greater than 2 mm,

• the protection method comprising the following steps:
• preforming of a prepreg panel so as to impart a shape corresponding to the shape of a surface of the part to be protected against fire, wherein the prepreg panel is preformed by ring sectors applied onto the surface of the part to be protected with overlapping, said prepreg panel comprising a secondary fiber reinforcement densified by a secondary matrix, a resin of the secondary matrix swelling under the effect of heat and delaminating the prepreg panel after polymerization of the prepreg panel,
• application of the prepreg panel preformed onto the part, and
• fastening of the prepreg panel onto the surface by heat treatment of the part fitted with said prepreg panel to produce a protective layer against fire, wherein the fastening step includes a sub-step during which joggling on the ring sectors is performed to ensure overlapping of the ring sectors on each other.