Effects of plasma oxidation on the surface and interfacial properties of carbon fibres/polycarbonate composites

Two types of carbon fibres, ultra-high modulus (pitch-based) and high strength (PAN-based), were submitted to an oxygen plasma treatment. Single filament tests were performed to evaluate the effects of the treatment on the mechanical properties of the fibres, Weibull analysis of the tensile data revealed no substantial changes in the tensile strength after fibre oxidation. Fragmentation tests performed on carbon fibre/polycarbonate composites showed that the plasma treatment increases significantly the interfacial shear strength. This demonstrates the ability of the cool plasma oxidation to enhance the adhesion of carbon fibres to polycarbonate. The possible influences of the structural and chemical properties of the carbon surfaces upon the final response of the interface were investigated using inverse gas chromatography (IGC) at infinite dilution. The increase of surface functional groups induced by the plasma treatment seems to be the main reason for the improvement of the interfacial adhesion. (C) 2001 Elsevier Science Ltd. All rights reserved.