Molecular modelling of interactions at the composite interfaces between electrolytically surface-treated carbon fibre and epoxy resin

Abstract

Two carbon fibre models, based on microscopic and XPS evidence of electrochemical surface treatment, have been proposed. A diagonal graphitic plane, comprising 52 six-membered rings (in a 4×13 configuration) and of 150 carbon atoms, was built as the principal, non-surface-treated carbon fibre model. Three layers of graphitic planes, each comprising 117 six-membered rings (in a 9×13 configuration) and of 300 carbon atoms, formed the multi-layer graphitic model. The nature and level of surface treatment was represented by the introduction of hydroxy (OH) and carboxy (COOH) groups: each time, a C–C bond was broken along the edge of the plane, and a pair of OH and COOH groups was added to the graphitic plane. Six pairs of OH and COOH were introduced gradually. The functional groups were distributed evenly along the edge of each graphitic plane. Their non-covalent bonding interaction with various amine-cured epoxy polymer models was simulated using the Cerius ² BLENDS method. Δ _mix G was used to indicate the interaction, and hence the interfacial adhesion. The results show a trend, in relation to the level of surface treatment, in agreement with experimental data of composite interlaminar shear strength (ILSS).