Method for manufacturing a turbine-engine fan casing having an acoustic coating

1. A method for manufacturing a turbine engine fan casing having an abradable coating on its inside face extending over a fraction of its axial dimension at a distance from upstream and downstream ends of the casing, and an acoustic coating arranged downstream and/or upstream of the abradable coating, the inside surfaces of the abradable coating and of the acoustic coating defining at least a portion of the wall of an air inlet passage, the casing being made of composite material comprising fiber reinforcement densified by a resin precursor matrix, the method comprising:

using a tooling element having a profile corresponding to the profile of the air inlet passage;

depositing a fiber structure that is to constitute fiber reinforcement of a composite material inside skin of the acoustic coating on the tooling element at a location corresponding to the location of the acoustic coating;

placing cellular structures of the acoustic coating in the form of sectors over said fiber structure;

shaping a fiber preform that is to constitute the fiber reinforcement of the casing on the tooling element with cellular structures of the acoustic coating being interposed between them;

subjecting both the fiber preform of the casing as held in its shape and impregnated with a precursor resin for the matrix of the composite material of the casing and also the fiber structure of the inside skin of the acoustic coating as impregnated with a precursor resin for the matrix of the composite material of said inside skin to common resin polymerizing heat treatment; and

multiply perforating the inside skin of the acoustic coating after the precursor resin for the matrix of the composite material of said inside skin has polymerized;

whereby an assembly is obtained that comprises the casing assembled together with an incorporated acoustic coating comprising said cellular structures and said multiply perforated inside skin.

2. The method according to claim 1 , wherein the fiber preform that is to constitute the fiber reinforcement of the casing is shaped on the tooling element with elements constituting abradable coating cartridges being interposed, such that after polymerization an assembly is obtained comprising the casing with the abradable coating cartridges and the acoustic coating incorporated therein.

3. The method according to claim 2 , wherein a layer of adhesive is interposed between firstly the fiber preform of the casing and secondly the cellular structures of the acoustic coating and also the abradable coating cartridges.

4. The method according to claim 2 , wherein an electrical isolation fiber layer is interposed between firstly the fiber preform of the casing and secondly the cellular structures of the acoustic coating and also the abradable coating cartridges.

5. The method according to claim 1 , wherein an adhesive coating is interposed between the fiber structure that is to constitute the fiber reinforcement of the inside skin of the acoustic coating and the cellular structures of the acoustic coating.

6. The method according to claim 1 , wherein the fiber preform forming the fiber reinforcement of the casing and the fiber structure forming the fiber reinforcement of the inside skin of the acoustic coating are both formed of fiber textures that are preimpregnated with resin.

7. The method according to claim 1 , wherein the fiber preform that is to form the fiber reinforcement of the casing is impregnated with resin after the fiber preform has been shaped.

8. The method according to claim 1 , wherein the fiber preform that is to form the fiber reinforcement of the casing and the fiber structure that is to form the fiber reinforcement of the inside skin of the acoustic coating are both impregnated with resin after the fiber preform has been shaped.