Fabrics made from fibres having a circular cross-section are prepared for use in thermoset laminates by impregnating the fabric with liquid resin and then adjusting the impregnated fabric to repetitive treatment by a roller under sufficient pressure to partially flatten the fibres and thus reduce both the fabric thickness and the interstitial void area. Used esp. for making laminates from untwisted multistrand carbon fibres, by preparing pre-impregnated sheets not more than 0.18 mm thick and contg. not more than 42% pref. not more than 35% wt. resin. Compressive impregnation and flattening significantly reduces the porosity and void content of the individual sheets and laminates made thereof, e.g. allowing a gas-impermeable laminate to be made from two impregnated sheets instead of four, thus reducing component wt. and cost of e.g. aircraft or rocket structures etc.
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