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Strength criterion of graphene GBs combining discrete bond strength and varied bond stretch
Journal of the Mechanics and Physics of Solids ( IF 5.3 ) Pub Date : 2022-09-21 , DOI: 10.1016/j.jmps.2022.105080
Guoqiang Zhang, Huichao Liu, Yan Chen, Huasong Qin, Yilun Liu

The strength criterion of graphene grain boundaries (GBs) under complex stress states plays an important role in guiding the design of high-performance graphene-related materials and devices under severe mechanical environments like ultrastrong structural materials or flexible electronics. However, finding a unified strength criterion that can adapt to different GB angles and loading states is still a challenge. In this work, we proposed a general method to construct the strength criterion of graphene GBs that includes the atomic details of defect. Firstly, systematic molecular dynamics (MD) simulations were carried out to explore the fracture behaviors of graphene GBs with different GB angles and loading states. Then, bond strength of heptagon ring σthR was obtained by projecting the applied stress field to the fractured bond direction, which gives the same value for the same type of Csingle bondC bond of same GB angle under different loading states. Besides, to further unify the bond strength of different GB angles, the residual stress caused by other pentagon–heptagon defects was considered by using the disclination dipole theory, in which the intrinsic bond strength σth0 for different GB angles collapses to the same value. With this scenario, the strength criterion of graphene GBs is presented as the bond stretch stress generated by external load exceeds any bond strength of the hexagon–heptagon defect. Furthermore, a unified bond strength is found, linearly decreasing with the equilibrium bond length, which can further be applied to the strength criterion of other defective structures like two types of SW defects (without analytical solution of residual stress) and even pristine graphene. The present results provide a comprehensive understanding of the failure of graphene by considering the balance of bond strength of defective structure and bond stretch stress generated by external load, which may pave the way to construct the atomic structure based strength criterion of other two-dimensional materials.



中文翻译:

结合离散键强度和变化键拉伸的石墨烯GB的强度标准

复杂应力状态下石墨烯晶界(GBs)的强度标准对于指导在超强结构材料或柔性电子等恶劣机械环境下设计高性能石墨烯相关材料和器件具有重要作用。然而,找到一个能够适应不同GB角度和加载状态的统一强度标准仍然是一个挑战。在这项工作中,我们提出了一种构建石墨烯GBs强度标准的通用方法,其中包括缺陷的原子细节。首先,进行系统分子动力学(MD)模拟,以探索不同GB角度和加载状态下石墨烯GB的断裂行为。那么,七边形环的键合强度σHR是通过将施加的应力场投影到断裂键的方向得到的,它给出了相同类型的单键相同GB角的C C键在不同加载状态下的相同值。此外,为了进一步统一不同GB角的键强度,利用旋错偶极子理论考虑其他五边形-七边形缺陷引起的残余应力,其中固有键强度σH0对于不同的 GB 角度,折叠到相同的值。在这种情况下,石墨烯GB的强度标准表现为外部载荷产生的键拉伸应力超过六边形-七边形缺陷的任何键强度。此外,还发现了一个统一的键强度,随着平衡键长线性下降,这可以进一步应用于其他缺陷结构的强度标准,如两种 SW 缺陷(没有残余应力的解析解)甚至原始石墨烯。本研究结果通过考虑缺陷结构的键强度和外部载荷产生的键拉伸应力的平衡,全面了解石墨烯的失效,这可能为构建基于原子结构的其他二维材料强度准则铺平道路.

更新日期:2022-09-26
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