Aspect ratio effect on shear modulus and ultimate shear strength of graphene nanoribbons

This paper focuses on shear modulus and shear deformation behavior of Graphene Nano Ribbons (GNR) post-wrinkling taking into account size effect. Atomistic modeling of armchair and zigzag GNR were performed at 300 °K for GNR with a constant 10 nm width and lengths ranging from 2.5 nm to 25 nm. Results show that ridge formation is oriented at 45 degrees for GNR with an aspect ratio less than one and that the number of ridges is equal to the reciprocal of the aspect ratio, while for aspect ratios higher than one, the ridge formation direction coincides with the diagonal direction of the GNR and only one ridge is formed. Once the diagonal tension reached its ultimate elastic level, three major stress-relaxing phenomena are reported. Results show that the average slope of the stress-strain curve beyond the ultimate elastic stress decreases with increasing GNR length. Moreover, the slope of the shear stress-strain curve in that region is always greater in armchair GNR than in Zigzag GNR. GNR can sustain very high plastic shear strains beyond 400% before failure for wide GNR. It is observed that the shear modulus is inversely proportional to the aspect ratio of the GNR.