Interfacial Regulation Mechanism And Electrical Contact Properties Of Pre-Oxidized Carbon Fiber Precursors Reinforced Composites

The pantograph catenary system(pantograph/ overhead catenary wire)is the only way for high-speed trains to obtain energy.As a key collector element for energy acquisition of high-speed trains,pantograph sliding plates should have good service performance.Carbon/carbon composites have been widely used in pantograph sliders for high-speed railroads due to their excellent mechanical and electrical properties.However,with the increase of speed and power of high-speed trains,the frequency of arcing and arc-burning energy of the pantograph catenary system has increased significantly,which has led to most of the pantograph carbon sliding plates in service to fracture and fall off,affecting the stable operation of high-speed trains.Therefore,the development of high-performance pantograph carbon sliding plate material is an urgent engineering problem to be solved.There are three key issues that limit the further improvement of mechanical and electrical properties and comprehensive electrical contact properties of carbon/carbon composites.Firstly,the interface bond between carbon fiber and carbon matrix is physically bonded with weak interfacial bonding;secondly,the interface forms innate microcracks and pores with high porosity during material preparation;and finally,the electrical contact mechanism and properties of the composites are unknown.To this end,the thesis focuses on three aspects of the carbon/carbon interface modulation problem.Firstly,the transition from mechanical locking to chemical bonding of fiber and carbon matrix is achieved,which improves the interfacial bonding effect;secondly,the adaptive expansion/shrinkage of fiber/matrix is achieved and the porosity is reduced;finally,the growth and expansion of microcracks when the material is subjected to erosion is inhibited,which improves its electrical contact properties.Firstly,a platform for the preparation and characterization of high-performance carbon/carbon composites was built independently,and pre-oxidized carbon fiber-reinforced carbon/carbon composites were prepared,and the interfacial mechanism of the pre-oxidized carbon fiber-reinforced composites was investigated.Compared with carbon fiber,the interfacial bonding force is increased by 33 times;(ii)when the pre-oxidized carbon fiber reinforced composites are subjected to mechanical impact,the fracture mode changes from brittle fracture of fiber pull-out in carbon fiber reinforced to pseudoplastic fracture of fiber breakage,the material has better ductility,and the flexural strength and impact strength are improved.The simultaneous carbonization structure of binder asphalt-coated pre-oxidized carbon fibers in composites was constructed to form an adaptive expansion/contraction effect of preoxidized carbon fibers/carbon matrix,which fills the microcracks between fibers and carbon matrix,effectively inhibits the generation and development of microcrack tips during material preparation,reduces the porosity of composites,and simultaneously enhances their electrical and thermal conductivity.The electrical contact test system was constructed to investigate the electrical contact characteristics of the pre-oxidized carbon fiber reinforced composites in response to the problem of easy chipping and falling off of carbon/carbon composites during arc erosion.(i)When the carbon/carbon composite is in static contact with copper electrode,the temperature rise rate of the pre-oxidized carbon fiber reinforced composite is reduced,and the maximum surface temperature is lower,showing a more "uniform" temperature distribution,and the change rate of the average temperature rise rate is smaller.(ii)When the carbon/carbon composites were dynamically separated from the copper electrode,the mass loss,flexural strength loss rate,compressive strength loss rate and impact strength loss rate of the preoxidized carbon fiber reinforced composites before and after the ablation were significantly reduced,and the cooling rate after the arc ablation was increased.In this study,by regulating the interface of carbon material of pantograph sliding plate,a sliding plate material with excellent mechanical and electrical properties and arc ablation resistance is prepared,which provides support for the development of new pantograph sliding plate and ensures safe and reliable operation of high-speed trains.