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Molecular-Dynamics Analysis of Nanoindentation of Graphene Nanomeshes: Implications for 2D Mechanical Metamaterials
ACS Applied Nano Materials ( IF 5.9 ) Pub Date : 2020-03-31 , DOI: 10.1021/acsanm.0c00327
Mengxi Chen 1 , Augusto M. Christmann 2 , Andre R. Muniz 2 , Ashwin Ramasubramaniam 3 , Dimitrios Maroudas 1
Affiliation  

We report results of a comprehensive computational study of the mechanical response to nanoindentation of graphene nanomeshes (GNMs) or nanoporous graphene, namely, single-layer graphene sheets with periodic arrangements of nanopores, based on molecular-dynamics simulations of nanoindentation tests according to a reliable interatomic bond-order potential. We find the GNMs’ response to indentation to be nonlinearly elastic until fracture initiation, with elastic properties that depend strongly on the GNM porosity but are not sensitive to pore edge passivation, which, however, influences the GNM failure mechanism past fracture initiation. Increasing GNM porosity leads to a monotonic decrease of the 2D elastic modulus of the GNMs, and the modulus–porosity dependence follows a quadratic scaling law. The maximum stress reached at the GNM breaking point is high throughout the porosity range examined, even at very high porosity. The maximum deflection of the indented GNMs at their breaking point exhibits a minimum at porosities below 20%; beyond this critical porosity, the maximum deflection increases monotonically with increasing porosity and can reach values comparable to half of the indented sample radius at high porosities. Such high deformability is interpreted on the basis of the C–C bond length and stress distribution over the GNM at its breaking point. Moreover, our analysis reveals an inelastic, dissipative necking mechanism of GNM failure at high porosities that further enhances the excellent deformability of the GNMs. Our findings highlight the potential of graphene nanomeshes as 2D mechanical metamaterials whose mechanical response can be tuned by proper tailoring of their structural features.

中文翻译:

石墨烯纳米网格纳米压痕的分子动力学分析:对二维机械超材料的启示。

我们根据对纳米压痕测试的分子动力学模拟,报告了对石墨烯纳米网格(GNM)或纳米多孔石墨烯(即具有周期性排列的纳米孔的单层石墨烯片)的纳米压痕力学响应的综合计算研究结果原子间键序势。我们发现,在压裂之前,GNM对压痕的响应是非线性弹性的,其弹性特性强烈取决于GNM的孔隙率,但对孔边缘的钝化不敏感,然而,这会影响GNM在断裂开始后的破坏机理。增加的GNM孔隙度会导致GNM的2D弹性模量单调减少,并且模量-孔隙度相关性遵循二次标度定律。在整个孔隙率范围内,即使在非常高的孔隙率下,在GNM断裂点达到的最大应力也很高。凹进的GNM在其断裂点处的最大挠度在孔隙率低于20%时表现出最小值;超过此临界孔隙率,最大挠度会随着孔隙率的增加而单调增加,并且可以达到与高孔隙率时压痕样品半径的一半相当的值。如此高的可变形性是根据C–C键长和GNM断裂点上应力分布的情况来解释的。此外,我们的分析揭示了高孔隙度下GNM破坏的无弹性,耗散颈缩机制,这进一步增强了GNM的出色变形能力。
更新日期:2020-03-31
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