MOlecular Dynamics Study Of The Young's Modulus Of Graphene Sheet

Graphene has broad application prospects due to its perfect optical, electrical,magnetic, and mechanical properties, which make it an excellent platform to design anovel class of advanced composites, impermeable membrane, electric transistors,semiconductor devices, nanosensors, and micro-nano electronic and mechanicalsystem, etc. However these excellent properties of graphene are related to itsmechanical properties which also determine the stability and reliability of the systemsequipped with graphene.In this paper, during the molecular dynamics method (MD) and the employscircular membrane elastic theory, we have studied the Young's modulus of freestanding circular membrane graphene. The main contents of this study are as follows:1. According to the different stages of the deflection, we perform studiesrespectively. There are different elastic responding characters of different deflectionstages. In small deflection, the indenter has little effect on the film deformationcharacter and point indenter loading model is suitable for depicting the force loading;in larger deflection, the influence of the film deformation caused by indenter shouldnot be ignored, and spherical indenter loading model should be taken. From the smalland larger deflection data sets analysis, we determine the Young's modulus of themonolayer graphene which is about 1.0±0.05 TPa.2. We have performed the analysis of the impact on the calculation results by theradius of the indenters, the size of the membrane, and the different pre-strain.Different results from cubic or polynomial force-deflection function for data setsfitting have also been discussed.3. The young's modulus of multilayer graphene has been investigated. We proposeda concept of equivalent indenter. By using larger deflection data sets and employingspherical indenter loading model, the Young's modulus values of 1-5 layers graphene aredetermined, which are 1.06 TPa, 0.82 TPa, 0.78 TPa, 0.91 TPa, 1.00 TPa, respectively.The simulation results show that: the graphene Young's modulus of graphene depends ontheir thickness. As the thickness is less than 3 atom layers, the modulus will decrease asthe thickness increases. However, when the thickness is more than 3 atom's layers themodulus will increase as the thickness increases, and equal to the bulk graphite modulusat last.