Study On Dispersion Characteristics Of Filler Particles And Thermal Conductivity Of Composites With Hybrid Fillers

With the development of science and technology,composite materials with high thermal conductivity has been widely used.Due to the small size of filler particles,the fillers often exist in the form of "Poly Group".It is necessary to disperse filler particles when preparing high thermal conductivity composites.The dispersion characteristics of filler particles and their applications in composites have become the research topics of scholars.In this paper,experimental and numerical simulation methods were used to study the dispersion effect of particles in gas environment.The influence of gas flow velocity and aperture of wind-distribution plate on dispersion characteristics of particles and the velocity distribution of particles during the process were investigated.The representative volume element(RVE)model of composites was established.And the steady-state thermal analysis of the RVE model was performed by finite element software.The influence of spatial distribution,volume ratio,filling content of hybrid fillers on thermal conductivity of composites was discussed.The results show that during the dispersion process of filler particles in gas environment,the PIV experimental measurement and numerical simulation study have found that the dispersion of filler particles in cavity is more uniform with smaller inlet gas flow velocity,when the aperture of wind-distribution plate is fixed.The larger the inlet gas flow velocity is,the greater disturbance of flow field is,and the dispersion uniformity of particles is reduced.When the inlet gas flow velocity and the opening rate are fixed,the aperture of wind-distribution plate is appropriately reduced,the number of air holes will increase,and the air holes are distributed uniformly,which are beneficial to improve the dispersion uniformity of filler particles.During the process of dispersion,the average vertical velocity of particles tends to decrease with theincrease of height.The vortex generated in the dispersion process is the main reason for velocity mutation of filler particles,which will affect the dispersion effect of filler particles to a certain extent.When filled with hybrid fillers of same material and different shape parameters,the thermal conductivity of composites is better than the additive effect of fillers filled alone.That is,hybrid fillers can further improve the thermal conductivity of composites.The thermal conductivity of composites filled with fibrous fillers is obviously higher than that of spherical fillers when the same kind of material is used.When filled with hybrid fillers of carbon fibers/spherical aluminum nitride(AlN),the thermal conductivity of composites is also higher than the superimposed effect of fillers filled alone.The thermal conductivity is different in three directions of composites with hybrid fillers of carbon fibers/spherical AlN.The average thermal conductivity in all directions can macroscopically characterize the thermal conductivity of the composites.Carbon fiber plays a dominant role in the thermal conductivity of composites with hybrid fillers under different spatial distributions,volume ratios and filling contents.