Multiscale Simulation Of The Mechanical Properties Of Graphene And Ceramic Composites

Due to the prominent mechanical properties including high Young's modulus and compressive strength,advanced ceramics represented by silicon carbide have been widely applied in both traditional industrial fields and emerging microelectronics fields.However,silicon carbide,which is known as a hard brittle material,is easy to be destroyed with the presence of interal or surface microcracks.The progress of this material is limited by the damage characteristics mentioned above.Graphene,with its outstanding mechanical properties and super specific surface area,presents great potential as a reinforcing phase to significantly enhance the mechanical properties of the matrix.The primary object of this research is a kind of composite which is mainly composed of silicon carbide and enhanced by graphene.With the employment of the molecular dynamics simulation at the microscale and the finite element method at the macro-scale,the enhancement mechanism and adjusting effect of graphene have been systematically investigated.The main work and results of this paper are shown as following.Firstly,the failure process of silicon carbide ceramic is studied by using the multiscale analysis method based on the cohesive zone model.With the application of molecular dynamics simulation,the process of crack propagation for silicon carbide crystals loaded by the tensile and shear traction has been illustrated respectively.Under the further analysis of the process behaviors,the crack extension mechanism at microscopic scales and the traction-displacement curve in which the cohesion parameters can be extracted are clarified.The three-point bending geometry of silicon carbide ceramics at macroscale is modeled with implementing these cohesion parameters into the main procedure of ABAQUS.On the other hand,the relationship between micro and macro mechanical properties of silicon carbide ceramics was established.The calcution results reveal the mechanism of brittle failure of silicon carbide ceramics.Secondly,based on the brittle fracture mechanism of silicon carbide ceramic,the uniaxial tensile mechanical responses of graphene-embedded silicon carbide composites are studied with the utilization of molecular dynamics simulation.The effects of interface contact types,layers and distribution of graphene,temperature and prefabricated cracks on the mechanical perpoterties of this composite material are considered.It is found that the volume fraction and distribution of graphene as well as the type of contact interface have a significant enhancement influence on silicon carbide ceramic matrix.For the reinforced composites with the same volume fraction of graphene,the enhancement effect of uniform distribution is better than that of serried stacking distribution.In addition,the crack propagation of silicon carbide matrix with the inclusion of graphene is also studied The results show that the plastic deformation ability of the composites is effectively improved by preventing crack penetration.Finally,with the help of three-point bending test simulated by molecular dynamics method,the mechanical properties of graphene-embedded silicon carbide composites under bend loading are investigated.Compared with the bending failure of pure silicon carbide beams,it can be observed that the synergistic effect of graphene and silicon carbide significantly improves the bending mechanical properties of composites.By alteringing the embedded position of graphene in composites,it can be concluded that the degree of bearing capacity of graphene and the ability to descrease stress concentration at the crack tip of silicon carbide are the key factors affecting the bending mechanical properties of composites.Futhermore,the size effect of graphene reinforced nancomposite beams was also studied by changing the span-depth ratio of composite With the increasing of span-depth ratio,the surface effect of nancomposite beam gradually decreases.The results of this paper expand the research field of mechanical properties of grapheneembedded silicon carbide composite.First,the analysis of this type of composite in multiscale is completed.Based on the cohesive zone model,the molecular dynamics simulation and finite element simulation are successfully combined to realize the investigation of the brittle failure of silicon carbide matrix;Second,the influence of graphene on the mechanical properties of silicon carbide ceramic matrix is studied in atomic scale.The mechanical response and deformation mechanism of the novel composite materials under different loads have been investigated comprehensively,which provids some theoretical guidance for the optimization of mechanical properties of grapheneembedded composite.