Molecular dynamics simulations and continuum modeling of temperature and strain rate dependent fracture strength of graphene with vacancy defects

Abstract

We investigated the temperature and strain rate dependent fracture strength of defective graphene using molecular dynamics and an atomistic model. This atomistic model was developed by introducing the influence of strain rate and vacancy defects into the kinetics of graphene. We also proposed a novel continuum based fracture mechanics framework to characterize the temperature and strain rate dependent strength of defective sheets. The strength of graphene highly depends on vacancy concentration, temperature, and strain rate. Molecular dynamics simulations, which are generally performed under high strain rates, exceedingly overpredict the strength of graphene at elevated temperatures. Graphene sheets with random vacancies demonstrate a singular stress field as in continuum fracture mechanics. Molecular dynamics simulations on the crack propagation reveal that the energy dissipation rate indicates proportionality with the strength. These findings provide a remarkable insight into the fracture strength of defective graphene, which is critical in designing experimental and instrumental applications.