Process for producing a laminated tubular fibrous structure for use as reinforcing structure for a composite piece

A process for the production of a laminated tubular fibrous structure comprising layers of fibrous material which are superposed in axial direction, each one extending from the inside surface to the outside surface of the structure, said process including the steps of providing a tubular braid made of fibrous material and progressively folding over the wall of the tubular braid to form corrugations or wrinkles and to progressively bring said corrugations or wrinkles into superposition upon one another, which corrugations and wrinkles constitute said layers of fibrous material, by the steps of:

• bringing the tubular braid over a mandrel of which the inner diameter corresponds to the inner diameter of the structure to be produced, by causing the braid to pass around a forming head which is mounted on the mandrel and of which the outer diameter corresponds to the outer diameter of the structure to be produced, and in
• winding at least one yarn following a helicoidal path on the braid, around the mandrel and at the front of the forming head, between said head and a counter-piece of which the faces in facing relationship have shapes corresponding to the shape of the wrinkles to be produced, said winding of the yarn being performed while the forming head is moved away from the counter-piece progressively with the formation of the wrinkles.