Mechanical Property Of Polycrystalline Graphene:A Molecular Dynamics Study

Graphene has ultra-high strength, stiffness and excellent electrical properties, it is recognized as the strategic new materials currently and has very broad application prospects. However, the graphene industrial prepared under the existing technical conditions inevitably make the graphene contains grain boundaries and defects, this kind of graphene is called polycrystalline graphene, which greatly limits the industrial preparation and mass production application of graphene. The existence of grain boundaries and defects can be reduced the mechanical properties of graphene, but it can also improve some other properties of graphene. At the same time, it is compared with the perfect graphene which has rigorous preparation technology and low price, the polycrystalline graphene has more application potential and feasibility. If we can via the research how the defect and grain boundary of polycrystalline graphene to affect the properties of graphene and use it, that we can carry out the industrialization of graphene preparation and mass production application with current technology, this will have a huge role in promoting the industrial application of graphene. So it has great significance the to research the mechanical properties of the polycrystalline graphene.In this paper, we select single-layer perfect and polycrystalline graphene as research object, the tensile fracture process and mechanical properties of the polycrystalline graphene are investigated using thenumerical simulation based on the molecular dynamics theory. The stretch model of perfect graphene are built using molecular simulation(MD)method to achieve the quasi-static load stretching process of the perfect graphene. The tensile process of perfect graphene model is repeated by using the polycrystalline graphene model contained grain boundaries and defects based on the perfect graphene stretching model. The effect of grain boundaries and defects to the breaking strength of graphene is discussed,the surface free energy and fracture toughness of the graphene are computed, and the polycrystalline graphene contained round hole defects and crack defects are simulated Under different conditions. Draw the following conclusions: the more the numbers of grains and grain boundaries, the weaker of the mechanical properties of graphene; the larger size of the defect, the worse of the mechanical properties of graphene; the more grain boundaries within the defect, the worse of the mechanical properties of graphene. The crack defect is more influence on the mechanical properties of the graphene with the same size of hole and crack defect. Defects in different place of the polycrystalline graphene, will have different effect to the mechanical properties of graphene, and the more number of the grain boundaries within the defect, the mechanical properties of the graphene is worse.