Numerical Simulation Research Of The Thermal Conductivity Of Filled Composite

Heat conduction materials are widely used in chemical,microelectronics,aerospace,defense industry and other fields.With the development of science and the expansion of application,people put forward new requirements for heat conduction materials.Filled polymer composites not only have good thermal conductivity,but also possess corrosion resistance,light weight,excellent mechanical property and other advantages.Now they are playing an important role in many fields and replacing traditional heat conduction materials gradually.The thermal conductivity of filled composite depends on synergistic effects of polymer matrix and thermal conductive filler.It's not a simple blending process.At present,there are a lot of problems in the simulation of the thermal conductivity of composite.They are not perfect and in-depth,especially under high filling amount,the error between the predicted value and the experimental result is large.Therefore,the establishment of reasonable calculation model and the numerical simulation research of effect factors of the thermal conductivity are important to the design of thermal conductive composite materials.The article takes microstructure difference between low filler content and high filler content into account and establishes the corresponding representative volume elements respectively for numerical simulation research on the thermal properties of polymer filled composite,which provides references for the design of filled composite.Main research works and results are as follows:Many Al₂O₃/EP composites are prepared,and the distribution characteristics of fillers in the matrix are observed by SEM.When volume fraction is low,the dispersion of the particles in the matrix is good,which is similar to random distribution.The distribution of the particles in the matrix has a significant microscopic inhomogeneity under high filling volume fraction.The thermal conductivity values of samples are tested,and the effect of filler volume fraction on the thermal conductivity of the composite is analyzed.According to the SEM pictures,representative volume elements which represent microscopic characteristics of the composites are established.Particles random distribution 3D RVE models under low filler content are established using the random sequential adsorption method.Through controlling particle sparse regions,particles non-uniform distribution 3D RVE models under high filler content are established.The predicted values of thermal conductivity can obtain through finite element solution,what are consistent well with experimental results.It's proved that the RVE models established in this paper can describe the microstructure of composites accurately.Finally,the influence of various factors on the thermal conductivity of the composite and their influence laws are analyzed,the results are as follows:?1?The thermal conductivity of composite increases with volume fraction,and the magnitude of increase becomes bigger and bigger.?2?When filler volume fraction is low,the effect of filler size on the thermal conductivity of composite turns out to be small.?3?The selection of lamellar or fibrous filler obviously enhances the thermal conductivity of composite.?4?There existing a critical value of the ratio between thermal conductivity of filler and matrix.Thermal performance of composite material will effectively improve by improving the thermal conductivity of filler under the critical value.?5?When the filler content is high,different spatial distributions will result in different network structures,which have a great influence on the thermal conductivity of composite.?6?The contact and interaction between fillers significantly strengthen the thermal conductivity of composite.