Chirality-dependent interfacial energy dissipation in graphene-reinforced polymer nanocomposites: A molecular dynamics study

Abstract

Methods for controlling the macroscopic mechanical behavior of polymers through graphene insertion are now being refined to utilize the inherent chirality of graphene. In this study, we computationally investigated the variation in the damping capacity with respect to graphene chirality and the relative vibrational load direction in epoxy/graphene nanocomposites at the molecular scale. All-atom molecular dynamics simulations showed that the nanocomposites exhibited improved energy dissipation when subjected to out-of-plane oscillatory shear strain along the armchair graphene compared to that under shear strain along the zigzag graphene. In particular, the anisotropic behavior governed the interfacial friction and associated slip properties of the polymer adjacent to graphene. Due to its high elastic modulus, armchair graphene facilitated the slippage of polymer components by suppressing out-of-plane wrinkle formation and structural interlocking at the interface. Owing to the hexagonal pattern formed by the graphene units, the surface energy landscape showed higher variation in the armchair direction. This forces the adjacent polymers to bypass the high-energy points on the potential energy surface, thus elongating the displacement trajectories. By contrast, the zigzag orientation maintains good interfacial bonding with the polymer under an external load owing to its high flexibility and low surface-energy variation. These findings provide molecular-level insights into the chirality-induced anisotropy in vibration damping and highlight a novel design strategy for the optimization of the dynamic mechanical performance of graphene-reinforced nanocomposites.