An Investigation of the Mechanical Properties of Improved Carbon Fibre Composite Materials

Abstract

A wide range of mechanical properties, involving tension, compression, shear, notch and impact tests, have been performed on twelve carbon fibre composite materials. The materials tested ranged from standard carbon fibre reinforced epoxy systems to high strain and intermediate modulus carbon fibres with toughened epoxy, bismaleimide and thermo plastic matrices. The actual improvement in mechanical properties of composites attainable through the use of these improved materials depended on both the type of fibre and resin and their compatibility in the composite, as well as the interface between them. Thus improved materials should be selected on their overall system performance rather than individual fibre and resin behaviour. None of the improved materials had increased compressive strength, particularly in the critical hot/wet and notched case, although most proved to be tougher than the standard materials. The thermoplastic based system had the greatest resistance to impact, but the properties of the ±45 laminates appeared to show some sensitivity to the rate of cooling after mould ing. Advice on the selection of materials is given and recommendations are made of how further improvements in composite performance might be achieved.