Effects of area, aspect ratio and orientation of rectangular nanohole on the tensile strength of defective graphene – a molecular dynamics study

Abstract

Molecular dynamics simulations with adaptive intermolecular reactive empirical bond order (AIREBO) potential are performed to investigate the effects of rectangular nanoholes with different areas, aspect ratios (length/width ratios) and orientations on the tensile strength of defective graphene. The simulations reveal that variation of area, aspect ratio and orientation of rectangular nanohole can significantly affect the tensile strength of defective graphene. For example, defective graphene with a larger area of rectangular nanohole shows a bigger drop in tensile strength. It was found that the tensile strength of both armchair and zigzag edged graphene monotonically decreases with area increases in rectangular nanohole. Changes in aspect ratio and orientation of rectangular nanohole, however, can either decrease or increase the tensile strength of defective graphene, dependent on the tensile direction. This study also presents information that the tensile strength of defective graphene with large area of nanohole is more sensitive to changes in aspect ratio and orientation than is defective graphene with small area of nanohole. Interestingly, variation of tensile strength of defective graphene from MD simulations is in good agreement with predictions from energy-based quantized fracture mechanics (QFM). The present results suggest that the effect of nanoholes on the tensile strength of graphene provides essential information for predictive optimization of mechanical properties and controllable structural modification of graphene through defect engineering.

Ripples in isotropically compressed graphene

“…The distinctive difference in ∆z distortion at 5% compressive strain (and the lack thereof at 2% compressive strain) can be explained by the simple notion that graphene's elasticity becomes anisotropic for both armchair and zigzag directions as a function of strain [42,43,44]. The anisotropic behaviour of the Γ -K (zigzag) and Γ -M (armchair) directions at 5% compressive strain (and the lack thereof at 2% compressive strain) furthermore suggests that the ripple formation process under isotropic compression is based on two competing effects, a) the energy gain through out-of-plane ∆z distortions (rippling) and b) the elasticity of the sheet, which varies with direction and strain [42,43,44]. Based on the formalism of reference [44], we can therefore express the ripple formation energy as…”

“…It was found that a compressive strain of 5% gives a similar corrugation pattern to that obtained in experiments. Various studies have also shown that the elasticity of graphene varies with direction (see Figure 2) [42,43,44]. For example, previous studies have shown that armchair graphene nanoribbons (GNRs) have a higher Young's Modulus, tensile fracture stress and strain than zigzag GNRs of the same size [42,43].…”

“…Various studies have also shown that the elasticity of graphene varies with direction (see Figure 2) [42,43,44]. For example, previous studies have shown that armchair graphene nanoribbons (GNRs) have a higher Young's Modulus, tensile fracture stress and strain than zigzag GNRs of the same size [42,43]. The increased stiffness of the graphene sheet in armchair direction would be expected to result in a lower out-of-plane (zdirection) distortion than that in the zigzag direction under the application of isotropic strain.…”

Recent Progress in Graphene/Polymer Nanocomposites

“…Furthermore, Qin et al. [ 53 ] explored the impact of vacancy‐defect containing area, aspect ratio, and tilting angle of nanohole on the tensile strength of graphene by MD simulations and quantized fracture mechanics. Figure 2d1 shows the tensile strengths of defective zigzag and armchair graphene declined with the increasing area of rectangular nanohole.…”

“…Reproduced with permission. [ 53 ] Copyright 2018, Royal Society of Chemistry. e1,e2) The effect of size on the mechanical properties of armchair and zigzag graphene nanoribbon.…”