Multiscale Modeling of Fracture in Epoxy/CNT Nanocomposites

Modeling fracture in a polymer nanocomposite with molecular resolution is a big challenge. We have developed a multiscale modeling framework on the basis of coarse-grained molecular dynamics (CG-MD) simulations and peridynamics to study fracture initiation and propagation in epoxy/CNT nanocomposites. The CG model constructed via a hierarchical coarse-graining scheme enables us to model an epoxy network at micrometer scale and still capture its mechanical properties including various moduli. A jointed-tube model is developed for CNTs that overcomes the corrugation issue in traditional CG potentials between CNTs and polymers. Peridynamics simulations of CG CNT bundles dispersed in CG epoxy are used at the microscale to generate statistical distributions of moduli and fracture properties to be used in macroscale peridynamics simulations of fracture toughness tests. The calculations are validated against physical experiments at a given macroscale volume fraction. Successful validation of our hybrid hierarchical-concurrent modeling framework integrating CG-MD and peridynamics models paves the way to designing epoxy/CNT nanocomposites with desired fracture properties via tuning CNT loading and dispersion state.