Study On Static And Dynamic Behaviors Of Graphene Aerogels By Coarse-grained Molecular Dynamics Method

Graphene aerogels(GAs)are a kind of 3D macroscale assemblies of graphene,which possess extremely high porosity,ultralight weight,excellent compressibility and electrical conductivity.They can serve as promising candidates in many fields,such as absorption,catalyst support,energy storage and electrochemistry.With the development of the preparation technology,the microstructures of GAs can be wellcontrolled.The superior properties of GAs arise from their microstructure.Understanding of the deformation mechanism of GAs and the structure-property relationship is of vital importance for optimal design of GAs and applications in a broad field.A new coarse-grained molecular dynamics(CGMD)method applying to graphene and its assemblies is proposed.Model of GA with honeycomb-like microstructure is established to investigate the compressive,shear behavior and impact response as well as microstructure deformation mechanism of GAs.The main contents are as follows.(1)A new CGMD method of graphene is proposed based on the function form of the Tersoff potential and the present CGMD method is validated through comparison with full-atom MD simulation results.In the simulation,each bead represents four atoms in the atomic lattice,the bonded interaction between beads are simulated by CG potential,and Lennard-Jones potential is employed to describe non-bonded interaction.Tensile and bending behavior of single-and multi-layer graphene sheets as well as the interlayer shear response of graphene are investigated.It is proved that the present CGMD method is accurate and the computational efficiency is improved.(2)The model of GAs consisting of two staggered honeycomb-like structures is established and quasi-static uniaxial compressive behavior of GAs is simulated by the present CGMD method.The stress-strain relationships of compression and compression-recovery processes are analyzed and the microstructure evolution is observed.The influence of microstructure on compressive behavior is investigated,including layer number and sizes of graphene sheets,as well as the arrangement of the microstructure.Besides,a negative Poisson's ratio within a certain range of compressive strain is described,which is related to both the microstructure and the deformation of graphene sheets.(3)The quasi-static shear behavior of honeycomb-like structure GAs is investigated by the CGMD method.The shear deformation and shear-recovery process of GAs consisting of monolayer graphene sheet in and out of the honeycomb planes are analysed.The influence of the microstructure on shear behavior is discussed.(4)An impact model of GAs with tri-layer graphene sheets is established.The impact response of GAs in and out of honeycomb planes is studied by the CGMD method.The microstructure evolution is simulated and the variation of contact force as well as energy dissipation at different impact energy is investigated.