Study Of The Mechanical Properties Of Grapheme With Crack Based On Molecular Dynamics

Graphene is now recognized as a new strategic materials due to it's high mechanical strength, superior thermal conductivity, and excellent electron mobility. It can be applied to many filed. But it's expensive to get perfect graphene under the current technical conditions. Meanwhile, both material production processes and chemical treatment may introduce structural defects in graphene. This greatly restricted the industrialization and the production of graphene. Although the existence of defects can reduce the mechanical properties of graphene, but it can improve some properties of graphene. On the other hand, compared with perfect graphene, defective graphene may be more economical and practical. If we can find the relationship between the properties and the defect in graphene and make the relationship on use, the industrialized production of graphene could be carried out by current tecnology. It can be a huge effect on the industrial application of graphene. So the research of defective graphene's mechanics properties has great significance.This article selects the single-layer graphene as the research object. Based on the theory of molecular dynamics, the tensile process of perfect graphene is studied firstly.Furthermore, the tensile process of defective graphene is studied.The relationship between fracture intensity and the initial crack length is discussed. The longer the initial crack, the lower the fracture strength. The classical theory of macroscopic fracture mechanics is used to calculate surface free energy and fracture toughness of graphene. And a preliminary discussion of the effects of initial crack on graphene energy release rate is : As the initial crack length increases, the maxmum graphene energy release rate decreases. The energy release rate increases as the crack growth.Further discussion of crack speed is made based on the result of the static fracture. During the quasi-static tensile process, the limit of graphene crack speed is 8350 m/s. Graphene crack growth rate was mainly affected in two aspects: the initial crack length and loading rate. Initial crack length will affect the maximum rate of crack propagation during the Quasi-static tensile process. The longer the initial crack, the smaller the maximum crack speed. Loading rate affects the crack growth rate in crack growth stage, when the crack propagation speed is far less than the limit speed, the higher the loading rate, the larger the crack propagation speed. But this phenomenon is not significant when the crack speed is closed to the limit speed. Before the crack growth, the change of loading rate is not obviously impacting on the crack speed. But when the crack growth, the change of loading rate is obviously impacting on the crack speed.