多晶石墨烯拉伸力学性能及其影响因素的灵敏度分析

Tensile Mechanical Properties and Influence Factor Sensitivity Analysis of Polycrystalline Graphene

晶粒尺寸、温度和应变率等对纳米材料的力学性能有重要影响.论文通过分子动力学(MD)数值模拟,分析了不同晶粒尺寸多晶石墨烯在不同温度、拉伸应变率下的杨氏弹性模量、极限应力和极限应变等拉伸力学性能.结果表明,晶粒尺寸、温度和拉伸应变率对拉伸力学性能有较大影响.利用正交实验理论,分别分析了杨氏弹性模量、极限应力和极限应变对晶粒尺寸、温度和拉伸应变率的敏感程度.结果表明,杨氏弹性模量和极限应力对影响因素的敏感程度由大到小依次为晶粒尺寸、温度和拉伸应变率;极限应变对影响因素的敏感程度由大到小依次为晶粒尺寸、拉伸应变率和温度.研究结果可为多晶石墨烯的理论研究和工程应用提供参考.

In recent years, graphene has become one of the hottest research fields. It is a single atom layer nanomaterial consisting of sp2-bonded carbon atoms, possessing extraordinary mechanical, thermal and electrical properties, whieh thus has a great potential to be used in a wide variety of applications, sueh as energy storage, sensors, electronics, reinforced composite materials and so on. Compared with other methods,although the chemical vapor deposition （CVD） method is currently the most sueeessful way in producing large-area graphene membranes,it leaves the polyerystalline samples with many grain bounda- ries. Therefore, research on the properties of polycrystalline graphene is of more important practical signifi- cance. Grain size,temperature and strain rate have significant effects on the mechanical properties of nano- materials. In the present study,a series of polycrystalline graphene samples of different grain sizes （2.5 nm ~12.5 nm） were set up using the Voronoi diagram. The mechanical properties, such as Young＇s elastic modulus,ultimate stress and ultimate strain of polyerystalline graphene in various grain sizes under differ- ent temperatures and tensile strain rates,were analyzed by means of molecular dynamics （MD） simulation. In addition, based on the theory of orthogonal experimental method, the sensitivities of grain size,tempera- ture,and tensile strain rate to Young＇s elastic modulus, ultimate stress, and ultimate strain were respec- tively investigated. The results showed that the tensile mechanical properties of polycrystalline graphene were significantly influenced by grain size, temperature, and tensile strain rate. It could be typically seen that crack nucleation first appeared at the joints where grain boundaries meet, then propagated through grains and resulted in the final fracture. Young＇s elastic modulus, ultimate stress and ultimate strain deceased with either a decrease in average grain size or an increase in temperature, but increased with an in crease in tensile strain rate, the increment of which became considerable when the tensile strain rate was greater than 0. 005 ps 1. The orthogonal experimental results showed that, the order of sensitivities to Young＇s elastic modulus and ultimate stress,from highest to lowest,was grain size, temperature,and ten- sile strain rate; while that to ultimate strain, was grain size, tensile strain rate,and temperature. The research results can offer some reference for the theoretical study and engineering applications of polycrystalline graphene.