Toughened carbon/epoxy composites made by using core/shell particles

Toughened epoxy resin composites have been prepared by resin-transfer mould ing by using a range of toughening agents. Two types of epoxy-functional pr eformed toughening particles were investigated and have a three-layer morph ology in which the inner core is crosslinked poly(methyl methacrylate), the intermediate layer is crosslinked poly(butyl acrylate) rubber and the oute r layer is a poly[(methyl methacrylate)-co-(ethyl acrylate)-co-(glycidyl me thacrylate)]. The presence of glycidyl groups in the outer layer facilitate s chemical reaction with the matrix epoxy resin during curing. Comparisons were made with acrylic toughening particles that have a similar structure, but which do not have the epoxy functionality in the outer shell, and with a conventional carboxy-terminated butadiene acrylonitrile (CTBN) liquid rub ber toughening agent. The composites were characterised by using tensile, c ompression and impact testing. The fracture surfaces and sections through t he moulded composites were examined by means of optical and scanning electr on microscopy. Short-beam shear tests and fragmentation tests were used to investigate the interfacial properties of the composites. In general, use o f the epoxy-functionalised toughening particles gave rise to superior prope rties compared with both the non-functionalised acrylic toughening particle s and CTBN. (C) 2000 Elsevier Science Ltd. All rights reserved.