Research On Performance Of Less-Metallic Friction Material Reinforced By Hybrid Fibers

With the rapid development of automobile industry,higher requirements for friction materials,such as excellent braking performance,environmental protection and economy were put forward.So far,the requirements above could not be fully satisfied by traditional friction materials.Therefore,accelerating the development of the new type of high-performance friction materials was regarded as the research hotspot at home and abroad.In this paper,reinforcing fibers content was optimized by using orthogonal test for formulations.The less-metallic friction materials reinforced by hybrid fibers were prepared by using one-step hot press molding technology.The friction and wear properties and mechanical-physical properties of friction materials were tested on a variety of testing equipment.The effects of the various reinforcing fibers for friction performance were studied by using range analysis.The optimal formulation was selected by using fuzzy comprehensive evaluation.Wear mechanism of the various formulations was analyzed by means of morphology and microstructure analysis.The results showed that the friction coefficient was greatly influenced by compound mineral fiber.The low-temperature friction coefficient was greatly improved with the increase of compound mineral fiber content.Heat recession was effectively mitigated by aramid pulp.The friction coefficient was improved by the synergistic effect of the same mass fraction of aramid pulp and potassium titanate whiskers.The wear rate was most affected by copper fiber.Copper transfer films were formed at friction interface,which could stabilize the friction coefficient and reduce the wear rate.S4 formulation(aramid pulp 4wt.%,potassium titanate whiskers 3wt.%,compound mineral fiber 15 wt.%,copper fiber 18 wt.%)with the highest fuzzy comprehensive evaluation value was considered to be the best formulation.Reinforcing fibers as bearing substances were thought to have a great influence on high-temperature wear mechanism during friction operation.The wear type was thermal decomposition wear and adhesive wear when friction materials containing a small amount of reinforcing fibers.The wear type was thermal decomposition wear and abrasive wear when bearing substances were compound mineral fiber and copper fiber.The wear type was thermal decomposition wear,fatigue wear and abrasive wear when bearing substance was compound mineral fiber.The wear type was abrasive wear when bearing substance was copper fiber.The technological parameters(hot-pressing temperature,heat treatment time and thermal pressure)were optimized by using orthogonal test for the optimal formulation.The effects of technological parameters on friction performance were studied.The results showed that the friction coefficient was most affected by hot-pressing temperature.The wear rate and shear strength were most affected by heat treatment time.The hardness was most affected by thermal pressure.The hot-pressing technological parameters of 160?×300s×20MPa and heat treatment parameters of 180?×11h were selected as the optimal technological parameters for S4 formulation.Wear resistance and shear strength were improved though heat treatment time was longer than before.