Yang Tian, Wang Chao, Wu Zuobing
LNM, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China.
School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China.
ACS Omega. 2021 Aug 25;6(35):22780-22790. doi: 10.1021/acsomega.1c03127. eCollection 2021 Sep 7.
Strain hardening is an important issue for the design and application of materials. The strain hardening of graphene foams has been widely observed but poorly understood. Here, by adopting the coarse-grained molecular dynamics method, we systematically investigated the microscopic mechanism and influencing factors of strain hardening and related mechanical properties of graphene foams under shear loading. We found that the strain hardening is induced by cumulative nonlocalized bond-breakings and rearrangements of microstructures. Furthermore, it can be effectively tuned by the number of graphene layers and cross-link densities, i.e., the strain hardening would emerge at a smaller shear strain for the graphene foams with thicker sheets and/or more cross-links. In addition, the shear stiffness of graphene foams increases linearly with the cross-link density and exponentially with the number of graphene layers by ∼ . These findings not only improve our understanding of the promising bulk materials but also pave the way for optimizing structural design in wide applications based on their mechanical properties.
加工硬化是材料设计与应用中的一个重要问题。石墨烯泡沫的加工硬化现象已被广泛观察到，但人们对其了解甚少。在此，我们采用粗粒度分子动力学方法，系统地研究了石墨烯泡沫在剪切载荷作用下加工硬化及相关力学性能的微观机制和影响因素。我们发现，加工硬化是由微观结构的累积非局部化键断裂和重排引起的。此外，它可以通过石墨烯层数和交联密度有效地调节，即对于具有更厚片层和/或更多交联的石墨烯泡沫，加工硬化将在较小的剪切应变下出现。此外，石墨烯泡沫的剪切刚度随交联密度呈线性增加，随石墨烯层数呈指数增加，增加量约为 。这些发现不仅增进了我们对这种有前景的块状材料的理解，也为基于其力学性能在广泛应用中优化结构设计铺平了道路。
