Coarse-grained Molecular Dynamics Modeling of Epoxy/CNT Nanocomposites*

Modeling fracture in a polymer nanocomposite presents a big challenge at the moment. To enable us to model larger systems over longer time scales that can be bridged to those in continuum mechanics models such as peridynamics, we have developed a coarse-grained molecular dynamics (MD) model of epoxy/carbon nanotube (CNT) nanocomposites. The polymer is described as bead-spring chains with bonded and nonbonded interactions parametrized with atomistic MD simulations. A CNT is represented similarly as a bead-spring chain but with each bond treated as a rod with finite length and radius. Such a treatment leads to a jointed-tube model in which the corrugation issue associated with traditional coarse-grained models of CNTs is removed and the represented CNT behaves as a filament with finite radius. The CNT-CNT and CNT-polymer interactions are further trained with atomistic MD modeling. Using the coarse-grained model, we study the behavior of CNTs in an epoxy matrix including dispersion and bundling and the fracture properties of the epoxy/CNT nanocomposites.