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

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.