Two types of sized carbon fibre were used in this study, Besfight HTA-7-12000 and Besfight ST-III-7-6000, both from Toho Rayon Co. Some of the fibres were thoroughly washed in chloroform at room temperature to remove the epoxy sizing. The unsized carbon fibres, Hysol XA-S, were from Hysol Inc. The curing agents for di-glycidylether of bisphenol-A (Epon 828, Shell Chemical Co.) were methylene dianiline (MDA, Aldrich Chemical Co.) and 1, 3-phenylene diamine (Merck). Polysulphone (Vdel, Amoco) and polycarbonate (Lexan, G. E.) were chosen as the matrix systems for the interface studies of carbon fibre-thermoplastic composites. The high temperature cured Bismaleimide resin system consisted of 4,4'-bismaleimido-diphenyl-methane (IM-AD 94-306, BTL Company), diallyl bisphenol A (Matrimid 5292B, Ciba-Geigy Company) and polyetherimide (Item 1000, G. E.) The microbond method [7] was used to measure the interracial shear strengths. The procedure involved the deposition of a small amount of resin on to the surface of a fibre as shown in Fig. 1. After the curing process, the fibre specimens were pulled out of the microdroplet at a rate of 2 mm min -1, using a Shimazu tensile tester. The experimental arrangement is shown in Fig. 2. The interracial shear strength was calculated from 7; = f p/~ D L