石墨烯裂纹扩展行为研究

基于分子动力学方法对含预制裂纹石墨烯进行扶手椅向拉伸断裂模拟.使用连续介质理论结合分子动力学计算石墨烯能量释放率,确定石墨烯能量释放率GIC为10.25 J/m2;应力强度因子K,c为3.33 MPa√m.进一步对影响石墨烯裂纹扩展速率的因素-初始裂纹长度与加载速率进行讨论.结果表明:裂纹初始长度与加载率会在一定程度上影响石墨烯中裂纹扩展速率.裂纹扩展速率会随着初始裂纹长度的增加而降低;但随着初始裂纹长度的增加,裂纹扩展速率对其敏感度降低.裂纹扩展速率会随着加载率的升高而增大.初始裂纹长度与加载率对裂纹扩展速率的影响有一定的关联性,加载率的升高会降低裂纹扩展速率对初始裂纹长度变化的敏感度.在此基础上确定了石墨烯中裂纹扩展极限速率为8350 m/s.

Study on Crack Propagation Behavior of Graphene

The fracture parameters of graphene are very important to graphene devices. But the relative research is still in the primary stage. In this paper, the tensile fracture process of pre-cracked armchair graphene is simulated by molecular dynamics software - LAMMPS. Firstly, the energy release rate and the stress intensity factor of graphene are calculated by continuum theory and molecular dynamics calculation. It is found that the energy release rate of graphene GIC is 10.11 J/m2 and the stress intensity factor KIC is 3.33MPam^1/2. Further more，a new model based on continuum theory and molecular dynamics is proposed to accurately compute the crack speed in graphene. The factors, including initial crack length and strain loading rate, that affect the crack speed of graphene are discussed. The results show that the crack initiation length and strain loading rate affect the crack speed to a certain degree. Before reaching the limit crack speed, the shorter the initial crack length is, the higher the crack speed is. But with the increasing of the initial crack length, the crack speed is insensitivity to the initial crack length. On the other hand, the higher the strain loading rate, the higher the crack speed is. Besides, the influence relationship on crack speed between initial crack length and strain loading rate is preliminarily discussed. The results show that the influence of initial crack length and strain loading rate on crack speed is related to some extent. With the increasing of strain loading rate, the sensitivity of crack speed to the initial crack length decreases. Based on the previous findings and discussion, this study finally comes to an objective analysis of the limit crack speed. The limit crack speed is 8350 m/s. The conclusions are expected to provide some reference for the practical design and application of graphene devices.