Macroscopic Fracture Properties of Glassy Nanocomposites from Molecular Dynamics Simulations and Empirical Force Fields.

Abstract

In this study, we extend a previously developed methodology for calculating macroscopic fracture properties in glassy polymers using molecular dynamics (MD) and empirical force fields to glassy nanocomposites. We apply this approach to epoxy nanocomposites with randomly dispersed carbon nanotubes (CNTs), modeling four system types: two with pristine CNTs (1 and 2% by weight) and two with hydroxyl (OH)-functionalized CNTs at similar concentrations. Using a macroscopic analytical model, we calculate the fracture energy and the stress intensity factor for each system and examine how interfacial adhesion influences load transfer and failure mechanisms. Moreover, the cohesive energies and the mean squared displacements for the different systems are calculated, to further analyze the load transfer mechanisms between CNTs and the matrix. Our results demonstrate that functionalized CNTs significantly enhance fracture properties compared to pristine CNTs due to improved interfacial adhesion, enabling better load transfer and delaying crack propagation. This study offers a computationally efficient approach for exploring fracture characteristics in CNT-epoxy nanocomposites. Using empirical force fields, we get faster calculations enabling us to model bigger and more complex systems.