Abstract: The processing window for thermosetting resins that contain particulate hardeners is prolonged using the combined steps of heat-treating the resin to form a low-viscosity resin mixture in which the particles are dissolved and then moulding the low-viscosity resin mixture at temperatures below the dissolution temperature of the particles to infuse a fibrous preform. The infused resin preform is heated to the curing temperature of the resin to provide final curing of the resin.

Abstract: A process for the manufacture of a prepreg comprising feeding a layer of unidirectional conductive fibres having a defined width, bringing into contact with a first face of the fibres a first layer of resin comprising thermosetting resin, and compressing the resin and fibres together by passing over one or more impregnation rollers, wherein the pressure exerted onto the conductive fibres and resin does not exceed 40 kg per centimetre of the width of the conductive fibres, and the resin being in sufficient amount for the resin to enter the interstices of the fibres and leave a first outer layer of resin essentially free of unidirectional conductive fibres.