Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology , Beijing 100081, China.
The State Key Laboratory of Nonlinear Mechanics, Institute of Mechanics, Chinese Academy of Sciences , Beijing 100190, China.
ACS Nano. 2017 Sep 26;11(9):8988-8997. doi: 10.1021/acsnano.7b03474. Epub 2017 Aug 25.
Because of the combined advantages of both porous materials and two-dimensional (2D) graphene sheets, superior mechanical properties of three-dimensional (3D) graphene foams have received much attention from material scientists and energy engineers. Here, a 2D mesoscopic graphene model (Modell. Simul. Mater. Sci. Eng. 2011, 19, 054003), was expanded into a 3D bonded graphene foam system by utilizing physical cross-links and van der Waals forces acting among different mesoscopic graphene flakes by considering the debonding behavior, to evaluate the uniaxial tension behavior and fracture mode based on in situ SEM tensile testing (Carbon 2015, 85, 299). We reasonably reproduced a multipeak stress-strain relationship including its obvious yielding plateau and a ductile fracture mode near 45° plane from the tensile direction including the corresponding fracture morphology. Then, a power scaling law of tensile elastic modulus with mass density and an anisotropic strain-dependent Poisson's ratio were both deduced. The mesoscopic physical mechanism of tensile deformation was clearly revealed through the local stress state and evolution of mesostructure. The fracture feature of bonded graphene foam and its thermodynamic state were directly navigated to the tearing pattern of mesoscopic graphene flakes. This study provides an effective way to understand the mesoscopic physical nature of 3D graphene foams, and hence it may contribute to the multiscale computations of micro/meso/macromechanical performances and optimal design of advanced graphene-foam-based materials.
由于多孔材料和二维（2D）石墨烯片的综合优势，三维（3D）石墨烯泡沫具有优异的机械性能，引起了材料科学家和能源工程师的广泛关注。在这里，通过利用物理交联和不同介观石墨烯片之间的范德华力，将二维介观石墨烯模型（Model. Simul. Mater. Sci. Eng. 2011, 19, 054003）扩展为 3D 键合石墨烯泡沫系统，同时考虑脱粘行为，以评估基于原位 SEM 拉伸测试的单轴拉伸行为和断裂模式（Carbon 2015, 85, 299）。我们合理地再现了包括明显屈服平台在内的多峰应力-应变关系，以及从拉伸方向近 45°平面的延性断裂模式，包括相应的断裂形态。然后，推导出拉伸弹性模量与质量密度的幂律关系和各向异性应变相关的泊松比。通过局部应力状态和介观结构的演化，清晰揭示了拉伸变形的介观物理机制。键合石墨烯泡沫的断裂特征及其热力学状态直接导航到介观石墨烯片的撕裂模式。本研究为理解 3D 石墨烯泡沫的介观物理性质提供了一种有效方法，从而有助于对微/介观/宏观力学性能的多尺度计算和先进石墨烯泡沫基材料的优化设计。
