Study On Mechanical Properties Of Graphene/Aluminum Composites By Molecular Dynamics Method

Graphene metal matrix composites(GMMCs)have wide application prospects in military,aerospace,microelectronics and many other fields due to their excellent mechanical properties such as high strength,high modulus and good wear resistance,good electrical and thermal conductivity.The dispersion of graphene in GMMCs and the interfacial property between graphene and metal have important effects on the overall properties of GMMCs.It is important for the design and application of GMMCs to reveal the relationship between the microstructure and the macro-mechanical properties.In this paper,a model of graphene/Al composite was established.The interfacial properties,mechanical behavior under compression,tension and nanoindentation loads and the corresponding microstructural evolution mechanism of the composites were studied based on molecular dynamics(MD)method.The main works of this paper are summarized as follows:(1)MD models of graphene/Al composites were established to study the mechanical behavior of graphene/Al composites under uniaxial compression.The compressive properties of composites with different graphene interlayer spacing and different crystal orientation of Al were investigated.The dislocation nucleation and movement within the Al matrix during the deformation and yield period are analyzed.Based on the dislocation-blocking mechanism and the load transfer effect at the interface,the reinforcing mechanism of graphene was revealed.(2)The mechanical properties of graphene/Al composites under tensile loads in different directions were studied by using MD simulation.Based on the stress-strain relationship and the deformation characteristics of the microstructures of the composites during deformation process,the differences of mechanical properties between graphene/Al composites and pure Al were investigated.The effects of different arrangement modes and volume fractions of graphene on the mechanical properties of composites were compared and analyzed.Tensile mechanical behavior of composites at different temperatures was studied by comparing the variation of atomic structure and dislocation line length at different temperatures.(3)The interfacial mechanical properties of graphene and Al in composites were studied by MD simulation of interfacial separation and slippage.The load transfer mechanism of interface under normal and tangential failure is revealed.The effects of crystal orientation of Al and the size of graphene on the interfacial properties were investigated.Besides,the variation of interfacial cohesion was obtained by simulating the rigid separation of graphene and Al matrix and then the interfacial behavior of graphene and Al was described by the cohesion curves.(4)Based on the nanoindentation MD simulation,the orientation dependence of single crystal Al,the nanoindentation mechanical behaviors of graphene coated Al materials(GCA)and graphene reinforced Al composites(GRA)were studied.The effects of thickness of graphene coatings on the surface mechanical properties were investigated by comparing the indentation resistance-displacement curves and the evolution of atomic microstructures of Al with different graphene coating layers.The effects of the thickness of Al layer within the GRA composite on indentation behavior were investigated.