Production in composite material of a lobed structure of a flow mixer

A method for manufacturing a composite material structure for a lobed structure of a gas turbine flow mixer, said flow flowing from upstream to downstream, the lobed structure having a final geometry and comprising a multilobed skirt portion having a plurality of lobes distributed around a longitudinal axis of the lobed structure, the method comprising:

• a) producing, by carrying it out on a first mold, a fibrous preform comprising one of a thermoformable resin and a thermosetting resin, in a configuration having a first geometry essentially developable by post-forming to the final geometry the composite material structure to be produced, and
• b) transferring on a second mold the fibrous preform having the first geometry, and, at least by exploiting the thermoformable or thermosetting nature of the resin, post-forming the first geometry, on said second mold, by deforming it to the final geometry,
• wherein the first mold has an annular upstream portion and a downstream portion which flares out, with lobes of a first amplitude and a first radius to form the first geometry, the annular upstream portion having a circular section and/or a cylindrical shape, and,
• wherein the second mold has an annular upstream portion corresponding to the annular upstream portion of the first mold and a downstream multilobed skirt portion corresponding to the final geometry, so that the downstream portion of the first geometry will be deformed on the second mold to the final geometry, the lobes of the final geometry having individually a second radius, the second radius being shorter than the first radius.