Research On Thermal Conductivity Of Aluminum-based Sandwich Carbon Fiber Composites Based On Numerical Analysis

With the integrated development of LED,heat dissipation has become a technical bottleneck that cannot be ignored in the development of high-power LED.As a key component of the heat dissipation channel,the substrate affects the efficiency of heat transfer to the heat sink.Currently,the mainstream homogeneous aluminum alloy substrate on the market has insufficient thermal conductivity to meet the heat dissipation requirements of high-power LED lamps.Metal-based high thermal conductivity ordered composite materials have strong designability and high cost performance,which is an important direction for the development of high thermal conductivity materials.Due to the high thermal conductivity of pitch-based carbon fibers,carbon fiber metal-based composite materials have higher thermal conductivity than homogeneous metals,and at the same time have the strength to meet performance requirements.Therefore,the analysis of the structural design of aluminum-based sandwich carbon fiber?copper-based?composite materials to improve the thermal conductivity of the substrate has certain practical significance for improving the passive heat dissipation capacity of the LED lamps.In this paper,through the meso model analysis of the core carbon fiber copper matrix composite material as the starting point,the macroscopic model of aluminum-based ordered composite plate is numerically simulated to predict the thermal conductivity of the aluminum matrix sandwich carbon fiber composite material.Finally,the application of the design material has been evaluated for preliminary use.?1?In order to obtain the thermal conductivity parameters of the key core carbon fiber copper matrix composites in the macro model,the longitudinal effective thermal conductivity is obtained by the mixing criterion,the transverse effective thermal conductivity is predicted by numerical simulation?FEM?of the representative volume element model,and the effects of the periodic distribution structure,the transverse effective thermal conductivity.In order to further understand the influence of carbon fiber on the lateral thermal conductivity of the composite,the influence of the lateral thermal conductivity,periodic distribution structure and diameter of the carbon fiber on the lateral thermal conductivity of the composite was also explored.The results show:the radial texture structure is more sensitive to the interface thermal barrier than the onion-skin carbon fiber structure,but it is more conducive to improving the lateral thermal conductivity of the composite;the radial thermal conductivity of the carbon fiber plays a major role in the lateral thermal conductivity of the composite The large carbon fiber diameter and the distance between adjacent fibers are conducive to the lateral thermal conductivity of the composite material.The analysis results have certain guiding significance for the preparation of carbon fiber composite materials.?2?Based on the FEM results of the transverse effective thermal conductivity of the carbon fiber copper matrix composite,the Hatta model assumed to be isotropic in the transverse direction of the carbon fiber has a good agreement when there is no interface thermal barrier;the Hatta model is improved and the fitting is obtained The theoretical model of lateral thermal conductivity of carbon fiber composites with higher accuracy and more suitable for considering carbon fiber anisotropy and interface thermal barrier.?3?Based on the FEM results of the effective thermal conductivity of the composite board,the flat plate heat conduction model introduced by the Hatta model and the improved model has a higher accuracy for the composite board,and the effects of the carbon fiber volume fraction and thickness ratio of the core layer are analyzed to improve the thermal conductivity of the composite board provides a design basis.Choosing radial carbon fiber as the transverse texture structure and increasing the thickness of the core layer are more conducive to increasing the thermal conductivity in the thickness direction of the composite board.When the interface combination is good,the effective thermal conductivity of the composite board with H_core=0.6 can reach 257?330 W/m K?parallel fiber axis?and 243?257 W/m K?vertical fiber axis?in the non-thickness direction;and can reach 176?180W/m K in the thickness direction,compared with the thermal conductivity of ADC12 aluminum alloy substrate with thermal conductivity of103.45 W/m K,the thermal conductivity in the thickness direction is increased by more than 70%.?4?Combining the results of numerical research,the composite board is applied to a specific heat dissipation structure for comparative analysis of thermal simulation.Under the same thermal model size and single chip input power,the chip maximum temperature of composite plate thermal model is lower than that of aluminum substrate thermal model.The heat dissipation effect of V_f,core=60%and H_core=2/3 composite plate thermal model is close to that of copper substrate thermal model.The weight is increased by 53.7%compared to aluminum substrate and decreased by 53.5%compared to copper substrate.The thermal model of the composite board with H_core=2/3 is reduced in size while maintaining the same weight as the original aluminum substrate,the heat dissipation effect under the same single chip input power is still higher than the thermal model of aluminum substrate,indicating that the application of aluminum-based sandwich carbon fiber composites is expected.