Composite structure manufacture

摘要

A filament reinforced perforate composite sheet is manufactured by forming a filament assembly which includes reinforcing filament structures in one or more layers and passage forming filament structures (16) which extend from the front face to the rear face of the assembly, applying a matrix material to the assembly to form a composite sheet and removing the passage forming filament structures (16) or a part or parts thereof to produce a multiplicity of passages extending through the composite sheet. The filament assembly may comprise one or more woven layers with the passage forming filaments being yarns of the weave or auxiliary yarns. Alternatively the layers may be knitted or braided or comprise laid filaments and the passage forming filaments may be stitching yarns. The passage forming filaments may be removed mechanically or by melting or dissolving them or if they are hollow only their end portions at the structure faces may be removed. The structure is suitable for sound attenuation panels in aero engines.