Molecular modeling of crosslinked graphene-epoxy nanocomposites for characterization of elastic constants and interfacial properties

The mechanical properties of crosslinked graphene/epoxy nanocomposites have been investigated using molecular mechanics (MM) and molecular dynamics simulations (MD). The influence of graphene nanoplatelet concentrations, aspect ratios and dispersion on elastic constants and stress-strain responses are studied. The cohesive and pullout forces at the interface of G-Ep nanocomposites are also investigated. The simulated MD models were further analyzed through radial distribution function, molecular energy and atom density. The results show significant improvement in Young's modulus and shear modulus for the G-Ep system in comparison to neat epoxy resin. The graphene concentrations in the range of 1-3% and graphene with low aspect ratio are seen to improve Young's modulus. The dispersed graphene system is seen to enhance in-plane elastic modulus than the agglomerated graphene system. The cohesive and pullout forces versus displacements data were plotted under normal and shear modes in order to characterize interfacial properties. The cohesive force is significantly improved by attaching chemical bonding at the graphene-epoxy interface. It appears that elastic constants determined by molecular modeling and nanoindentation test methods are comparatively higher than the micromechanics based predicted value and coupon test data. This is possibly due to scaling effect. (c) 2013 Elsevier Ltd. All rights reserved.