Simulation Study On Thermal Properties Of Graphene/aluminum Matrix Composites

With the rapid development of electronic devices toward high performance and miniaturization,while the installation space of electronic components is limited,it is also necessary to give full play to their performance functions.As a result,high-performance chips perform high-speed operations,generating a large amount of heat in a compact and narrow space,and the process of heat dissipation is facing new challenges.To match the heat dissipation requirements of electronic products,a new material with high thermal conductivity and low expansion performance is required.Aluminum has high thermal conductivity and is a common electronic packaging material,but its thermal expansion coefficient is large,and it is easy to generate thermal stress when temperature changes,which leads to failure.Therefore,graphene with high thermal conductivity and negative thermal expansion has become an ideal reinforcement of aluminum.At present,most of the research on graphene/aluminum matrix composites at home and abroad is to prepare composites with excellent properties by means of experiments,but there is little research on the influence mechanism on their microstructure.In this paper,based on the finite element method and the finite element software ABAQUS,a three-dimensional model of graphene nanosheets/aluminum matrix composites at the microscopic scale was established,and the thermal conductivity and thermal expansion characteristics of the composites were deeply studied.In terms of thermal conductivity,the effects of the shape,aspect ratio,geometric configuration and volume fraction ratio of graphene nanosheets on the thermal conductivity of the composites were discussed.The results show that the shape of graphene nanosheets has little effect on the thermal conductivity.Increasing the aspect ratio in a certain range can effectively improve the thermal conductivity of the composites.In addition,due to the complexity of graphene nanosheet configuration,the thermal conductivity of the composites is also affected.When the graphene nanosheets in the composite are distributed in layers,the thermal conductivity is the highest and the random distribution configuration is the smallest.By studying the influence mechanism of the orientation of graphene nanosheets on the heat flux density of composites,it is found that the orientation of graphene nanosheets is related to its own heat flux density.The larger the angle between the alignment direction of graphene nanosheets and the direction of temperature load,the smaller the heat flux density of graphene nanosheets,thus reducing the thermal conductivity of the composite.In addition,the volume fraction ratio of graphene nanosheets also has a certain influence on the thermal conductivity of the composites.At lower volume fractions,the two are almost linearly related.In terms of thermal expansion performance,the effects of graphene nanosheet shape,aspect ratio,geometric configuration and volume fraction ratio on the thermal expansion coefficient of the composite were also analyzed.The results show that the thermal expansion coefficient of the composite is less affected by the shape of the graphene nanosheets,and the effect of the aspect ratio on the thermal expansion coefficient is also less.The geometric configuration of graphene nanosheets has a certain effect on thermal expansion.The thermal expansion coefficient of the composite material is the smallest when the graphene nanosheets are agglomerated and distributed,and the thermal expansion coefficient is the largest when the graphene nanosheets are networked or randomly distributed.A similar approach was used to capture the strain on the point path,it is shown that the orientation of graphene nanosheets affects the strain in the nearby region.The larger the angle between the alignment direction of graphene nanosheets and the expansion direction,the greater the strain in the nearby region,which means that the inhibition of thermal expansion in this region is smaller.In addition,as the volume fraction of graphene nanosheets increases,the thermal expansion coefficient of the composite decreases.By comparing some of the simulation results with the experimental results in the literature,the rationality and accuracy of the three-dimensional graphene nanosheets/aluminum matrix composite finite element model for the prediction of the thermal conductivity and thermal expansion coefficient of the composite are verified.The conclusions obtained from each part of the research have certain reference value,which lays a theoretical foundation for designing and optimizing the microstructure of composite materials.