Molecular modelling of interactions at the composite interface between surface-treated carbon fibre and polymer matrices: the influence of surface functional groups

Abstract

To simulate the results of surface treatments, commonly encountered functional groups were introduced onto the surface of the carbon fibre model. The carbon fibre model used in this study is based on the single layer diagonal graphitic plane, comprising 52 six-membered rings, in a 4×13 configuration, and of 150 carbon atoms. Surface treatment was represented by the introduction of functional groups (–R): each time, a C–C bond was broken along the edge of the plane, and a pair of –R groups was added to the graphitic plane. The total number of functional groups (n) was six. The effect of these functional groups on the non-covalent bonding interactions at the composite interface between carbon fibre and epoxy resin was investigated using a previously established BLENDS method. The compatibility of the resin and fibre in this model, indicated by the interaction parameter χ(T ), was dependent upon two factors: steric bulk and electrostatic interactions. The halogen substituents show a decrease in χ(T ), as one descends the group. Maximum interaction tends to be a function of steric bulk and polarizability in this group. The alkyl (C_nH_2n+1) and phenyl substituents also show a decreasing trend inχ(T ) with increasing size, although the interaction parameter with methyl is anomalously low in all cases.