Study On Surface Interface Structure And Electrothermal Properties Of Carbon Fiber Modified By High Efficiency Coating

Carbon fiber is a high-performance fiber.Due to its high specific strength,high specific modulus,fatigue resistance,corrosion resistance and low density,it is widely used as a reinforcing material for advanced matrix composites in national defense,aerospace,transportation,etc.At the same time,the good electrical and thermal conductivity of carbon fiber also promotes its application in aerospace,electromagnetic shielding,road deicing,and civil heating.However,the thermal stability of carbon fiber at high temperature in oxygen-containing environment is poor,and the electrothermal properties of electrothermal materials still need to be strengthened,which also limits the application of carbon fiber.In view of the above shortcomings,in this paper,a simple and easy graphene/epoxy resin surface coating process and electroplating nickel metallization were used to construct a functional coating on the surface of carbon fiber,and the electrothermal properties and microstructure of the carbon fiber modified by surface coating were explored.The details are as follows:(1)The surface coating of PAN-based carbon fibers was modified with epoxy resin mixture using graphene as additive through simple impregnation coating,and then it was heat-treated in nitrogen atmosphere at high temperature.The relationship between the electrothermal properties of carbon fibers and their microstructures under different modification conditions was further studied.The results show that the carbon fiber modified with surface coating and heat-treated in nitrogen atmosphere had a fast temperature response at voltage of 4 V.The surface temperature of it rapidly increased by 40 ? within 60 s and reached an equilibrium state,and its equilibrium temperature was about 21.4% higher than that of the original fiber.And it showed good electrothermal stability.Structural analysis and finite element simulation show that the graphene/epoxy surface coating process can improve the structural stability of carbon fibers at high temperature,and produce conductive microstructure on the surface of carbon fibers.(2)In order to further strengthen the electrothermal properties of carbon fibers and enhance the thermal stability of coated carbon fibers in an oxygen-containing environment,a simple and easy-to-control electroplating process was used to metallize the pretreated carbon fibers,and nickel coating was applied on their surfaces.The effects of different pretreatment conditions and current densities on the effect of nickel plating on carbon fiber surfaces were explored,and the surface structure of nickel-plated carbon fibers and the mechanism of plating formation under different plating times were analyzed.And finally the mechanical properties,oxidation resistance and electrothermal properties of nickel-coated carbon fibers were characterized.The results show that the metal nickel was well combined with the pretreated carbon fiber,and the coating was flat and dense,which could make up for the defect structure on the carbon fiber surface.When the coating thickness was less than 0.4 ?m,it could improve the mechanical properties of carbon fibers,and when the thickness was around 0.4 ?m,it had a better effect on improving the oxidation resistance of carbon fibers.The electrothermal properties of the nickel-coated carbon fibers were significantly improved with the increase of the coating thickness.The surface temperature of nickel-coated carbon fibers rapidly increased by 40 ? 86 ? within 30 s and reached an equilibrium state,which was 12% ? 81% higher than that of the uncoated carbon fibers.And nickel-coated carbon fibers also showed good electrothermal stability,having the potential to be applied to electric heating equipment in industrial and civilian industries.