The size effect in mechanical properties of finite-sized graphene nanoribbon

Size effect in mechanical behavior of finite-sized graphene nanoribbons (GNRs) under uniaxial tension is studied using Molecular Dynamics (MD) simulations. The size effect and aspect ratio effect are significant in zigzag GNRs (ZGNRs), while their influence on the mechanical behavior of armchair GNRs (AGNRs) is negligible. For square shaped ZGNRs of increasing size, the elastic modulus increases while the ultimate failure stress and strain decrease. For rectangular shaped ZGNRs, the aspect ratio effects are especially predominant in those with fixed length. Wider ZGNRs have higher elastic modulus but lower failure stress and strain. For GNRs of fixed width, neither ZGNRs nor AGNRs show significant aspect ratio effect when length increases. The results show that ZGNRs are generally stronger than AGNRs under the same loading conditions. A new concept Density of Weakness (DOW) has been proposed to explain the size effect of ZGNRs.