A pre-impregnated part includes a main layer and a reinforcing layer. The main layer is made from a first composite material including a first matrix made from thermoplastic material, and first reinforcing fibers embedded in the first matrix. The reinforcing layer is made from a second composite material including a second matrix made from thermoplastic material, and second reinforcing fibers embedded in the second matrix. The pre-impregnated part has a flattened shape of at least a portion of a finished part to be manufactured from said pre-impregnated part, and a surface of the main layer is smaller than a developed surface of the finished part to be manufactured.