Reactive atomistic molecular dynamics simulations of interfacial damage phenomena in graphene/epoxy nanocomposites

Abstract

The mechanical behavior of graphene/epoxy nanocomposites is governed by their constituents and interfacial interactions, making atomistic simulations essential for understanding interfacial damage. In this study, reactive molecular dynamics (MD) simulations utilizing a reactive force field (ReaxFF) are employed to examine the interfacial properties of graphene/epoxy nanocomposites. The ReaxFF framework, which calculates the total system energy as a function of bond-order-dependent potentials, enables the modeling of chemical reactions and bond failure. Initially, graphene/epoxy interface models are constructed to systematically evaluate the influence of key parameters, including the number of graphene layers (1, 2, 3, or 4 layers), interlayer spacing (50, 100, or 200 Å), and pull-out loading rate (0.001, 0.01, or 0.1 Å/fs), on interfacial properties. Subsequently, a representative interface model is used in reactive MD simulations to predict interfacial behavior and evaluate interfacial damage under both normal and shear pull-out modes. The simulation results show that changes in the interlayer spacing distance lead to significant variations in the elastic modulus of the interface, ranging from 3.3 % to 273.8 %. A lower pull-out loading rate results in a stiffer interfacial response. The simulations reveal that interfacial damage is induced by the stretching of entangled epoxy chains and the failure of epoxy chain components, such as ethylene linkages and hydroxyl and amino groups. Moreover, these epoxy chain failures correspond to the initiation and propagation of cracks at the interface, providing a detailed mechanism for mechanical degradation of graphene/epoxy nanocomposites.