The Preparation Of High Friction Composite Brake Shoe And Study On The Properties

Friction material is a very important component in the braking system of rail transit,and its performance will directly affect the safety and reliability of vehicle and mechanical equipment.With the development of the rail transportation industry and aerospace industry,the requirements for friction materials are getting higher and higher.In this paper,high friction brake shoes were prepared by dry hot pressing process.Effect of Preparation technology on friction and wear properties of high friction composite brake shoe was studied through RSM(Response Surface Methodology).Preparation technology of high friction brake shoes was optimized by RSM.The relationship between the molding pressure,temperature and time and the properties of friction materials were investigated.And the molding processes were optimized through RSM.The influences of the high performance filler,and mass ratio of cashew oil modified phenolic resin(CPR)to nitrile rubber(NR)on the properties of composite materials were discussed.The surface morphology of composites were observed and analyzed by Laser Scanning Confocal Microscopy and Scanning Electron Microscopy.The results show that:(1)The hot pressing process of high friction composite brake shoe has a great influence on the wear performance of the friction.There is a strong interaction between the molding temperature and molding time.The optimum pressing process for high friction composite brake shoe are 19~25MPa,165~174 ℃ and molding time 18 ~ 22 min.(2)NR is high temperature resistant.And the hardness of the friction material density,compression strength,compression modulus,are increased with NR increased,but the impact strength of the opposite trend.The heat resistance temperature of CPR is higher than NR,and the increase of resin content improves the heat resistance of high friction composite brake shoe.With the increase of CPR,the interface strength between the matrix and the other components of were enhanced,and the formation of secondary contact area was promoted.The increases of real contact areas improve the tribological properties.(3)High performance fillers have a significant influence on the tribological properties of high friction composite brake shoes.With the increase of filler content,the friction coefficient of high friction composite brake shoes increases gradually,and the specific wear rate also increases.When the filler content at a low level,the main wear forms are abrasive wear and adhesive wear.With the increase of filler content,the main wear forms of the material change to abrasive wear and fatigue wear.(4)The surface modification of fiber can improve the interfacial properties of fiber and adhesive matrix.High friction composite brake shoe with modified fiber have higher impact strength.And the impact strength of high friction composite brake shoe increases with the fiber content.(5)The formulation of high friction composite brake shoe was optimized by orthogonal test orthogonal experimental design.The formulation of better friction coefficient is 7% CPR,9.9% NR,33.8% fiber,49.3% filler.And the formulation of better specific wear rate is 20% CPR,2.7% NR,24% fiber,53.3% filler.