Composite aircraft wing member manufacture incorporating suction holes to enhance laminar flow

摘要

A process is claimed for manufacturing a structural member with perforations, especially for creating laminar suction over an aircraft wing. Two independent, three-dimensional carbon fibre prepregs (1,2) are produced and placed on top of each other and retaining fibres (5) of a material with a vapourisation temperature above the curing temperature of the prepreg resin are woven into the prepregs perpendicular to the contact surface (4) between the prepregs to hold then together. After being compressed the prepregs (1,2) are separated at the contact surface (4) and reveal the retaining fibres (5) running perpendicular to the exposed prepreg surfaces (4'). The prepregs (1,2) are moulded and cured at 120 deg C to a desired shape and the temperature is then increased to vapourise the retaining fibres (5) leaving perforation channels through the prepregs perpendicular to the surfaces (4'). Preferably the prepregs (1,2) are produced either by a three-dimensional weaving of resin impregnated carbon fibres (3) or by impregnating pre-woven fabrics. Retaining fibres (5) are made of polyoxymethylene (POM), polymethylmethacrylate (PMMA) or polyethyleneterephthalate (PET) and may be coated, e.g. with metal, so that after vapourisation the coating forms the walls of the perforation channels. After the curing and vapourisation stages the final structural member may be pyrolised at about 1400 deg C. In a process variation to guarantee perfectly perpendicular retaining fibres (5) a layer of retaining fibres is woven onto the outer surfaces of the prepregs (1,2) and are penetrated by the retaining fibres (5) perpendicular to the prepreg surfaces (4). These layers of retaining fibres are removed prior to finishing of the structural member, preferably during the thermal vapourisation of the perpendicular retaining fibres(5).