Effects of grain size, temperature and strain rate on the mechanical properties of polycrystalline graphene – A molecular dynamics study

Abstract

We investigate the mechanical properties of polycrystalline graphene deforming under uniaxial tension by using molecular dynamics simulations, focusing on the effects of grain size, temperature and strain rate. It is found that polycrystalline graphene with smaller grain size shows a larger drop of Young’s modulus and fracture strength. For the polycrystalline graphene with grain size of 7.5nm, the Young’s modulus and fracture strength is about 80% and 40% that of single-crystalline graphene, respectively. Our simulation results also reveal that the Young’s modulus and fracture strength of polycrystalline graphene are more sensitive to the changes of temperature and strain rate than that of single-crystalline graphene. When temperature increases from 100 to 1200K, the fracture strength of polycrystalline graphene reduces by around 45%. At room temperature (300K), the fracture strength of polycrystalline graphene increases by 10% as the strain rate increases from 5×10−5 to 5×10−3ps−1. Furthermore, the strain rate has a stronger influence on the fracture strength of polycrystalline graphene at a higher temperature than at a lower temperature; while the temperature has a stronger influence at a lower strain rate than at a higher strain rate. Our study thus provides a comprehensive understanding of the mechanical properties of polycrystalline graphene.