Preparation And Properties Of High Thermal Conductivity Graphite Films Reinforced Resin Matrix Composites

With the rapid development of 5G communications,aerospace,new energy vehicles and other fields,more and more high-power devices are used,and these devices also require the development of miniaturization,thinness,multifunctional integration and lightweight.In this case,the heat generated by the device is difficult to dissipate in time,which will lead to the accumulation of heat and reduce the working life of the device,increase the cost of use,and put forward higher requirements for the heat dissipation system.Therefore,it is imperative to develop new materials with higher thermal conductivity.The high thermal conductivity resin matrix composite has the advantages of excellent thermal conductivity,light weight,corrosion resistance and so on,which is suitable for the new generation of high power device heat transfer materials.The traditional heat-conducting resin matrix composites are usually reinforced with metal particles or inorganic ceramic materials.The thermal conductivity of the prepared composites is not high,and it is difficult to meet the heat dissipation requirements of modern high-power devices.Therefore,it is urgent to find a kind of reinforcement which can greatly improve the thermal conductivity of resin matrix composites.In recent years,graphite films have attracted much attention because of their high thermal conductivity.However,the surface of graphite films is very smooth,and the adhesion of resin matrix is very poor,which leads to poor mechanical properties of composite materials.This paper introduces high temperature heat treatment defect after graphite films and carbon fibers together strengthen bis maleimide BMI by compression molding a pressure molding resin matrix composite was prepared,and explores the volume fraction of graphite films and heat treatment temperature on the properties of composite material mechanics and thermal effects.Get the main conclusions are as follows:Firstly,the composite material was prepared by a single molding process of high thermal conductivity graphite films without surface treatment,bismaleimide resin and prepreg.The test results show that the bending strength of the composites decreases by more than 94.6% after the graphite films is added,and the fracture mode of the composites changes from brittle fracture to ductile fracture.However,after the graphite films was added,the thermal conductivity of the composite was greatly improved,up to 1133.70 W/(m·K),which was about 21.42 times higher than that of the composite without graphite film added.The infrared thermal imager found that the heat of the composite without graphite film was concentrated on the hot end and difficult to dissipate,and the thermal image of the composite with graphite films was uniform in color.The small temperature difference between the cold end and the hot end also indicates that the thermal conductivity of the composite is excellent.In order to solve the problem of poor mechanical properties of graphite film reinforced resin matrix composites,the graphite film was etched by high temperature air.After heat treatment,circular,hexagonal and disordered grooves are produced on the surface of the graphite film.The defects are derived from the intrinsic defects of the graphite film and the unstable carbon atoms at grain boundaries.After heat treatment,the thermal diffusion coefficient of the graphite film did not change significantly,but the contact Angle between the graphite film and the bismaleimide resin became smaller,and the interface binding force between them was effectively improved.Finally,the modified graphite film reinforced resin matrix composites were prepared by hot pressing method with high thermal conductivity graphite film and bismaleimide resin treated at 500～800 ℃.The results show that the bending strength of the modified graphite film reinforced resin matrix composites is up to 116.18 MPa,and the thermal conductivity is down to 797.88W/(m·K),which indicates that the hole defects generated by surface modification can enhance the binding force between the graphite film and resin matrix,forming a "spike" structure.This paper provides an economical and convenient surface treatment scheme for graphite films.This strategy not only gives play to the high thermal conductivity of the graphite film,but also enhances the interface bonding strength between the graphite films and the resin matrix,so as to improve the mechanical properties and thermal conductivity of the composite materials,which provides feasibility for expanding the application scenarios of the high thermal conductivity resin matrix composite materials.