Role of Defects in the Mechanical Properties of Graphene-Copper Heterostructures

Through molecular dynamics simulations of tensile tests, the effect of vacancies and Stone-Wales defects on the mechanical properties of sandwich-like heterostructures, composed of graphene and two symmetrical copper layers at the nanoscale, is studied. Chirality dependence of the graphene layer is also investigated. During elastic deformation, defects adversely affect the mechanical response. However, defective systems can show an improvement of the plastic properties. Vacancies have a stronger impact compared to Stone-Wales defects. Elasticity, toughness, and ductility are enhanced along the zigzag direction, while stiffness is improved along the armchair edge. The Poisson's ratio was calculated for all graphene-copper heterostructures. At a critical strain it becomes negative along the thickness direction, preserving the auxetic property at higher strain values. In general, the heterostructure behavior is driven by the graphene response. Our findings may be useful to understand the strengthening mechanism induced by this two-dimensional material in metals such copper and for the design of similar systems.