Aligning fibres

A process for the production of a mat of aligned fibres, suitable for impregnating with a matrix to form a composite material, comprising (1) passing a continuous stream of a dispersion of fibres in a liquid medium from a dispersion supply source to and over the whole of a permeable surface, subjecting the stream of dispersion to continuous acceleration relative to the permeable surface as it progresses across the permeable surface, thereby generating a continuous stable aligning force to produce and maintain a uniform pattern of alignment of the fibres in the dispersion, and simultaneously (2) applying a pressure difference across the permeable surface to cause part of the liquid medium to pass through the permeable surface and leave a mat of aligned fibres on the said surface, the rate at which liquid medium is withdrawn through the surface at any point being maintainend well below the rate of flow of the dispersion across the surface at that point to maintain an accelerating layer of disposition above the surface and minimize end-on deposition of fibers.