Research On The Less-metal And Low-resin Friction Material Reinforced By Hybrid Fibers

With the continuous development of the automotive industry,the cars ownership gradually increased.Driving safety and comfort have got more and more attention.Vehicles braking performance is directly affected by the performance of friction material.The friction materials which have stable brake,low noise,no hurt to the disc and environmental protection are more favored by the automotive industry.In order to meet the demand of the automotive industry's rapid development,the manufacture of new friction materials with high performance will be a focus research topic both at home and abroad.This research utilized orthogonal experiment method to design the formulation of friction material and adopt hot-embossing technique to prepare the less-metal based lowresin friction material sample enhanced by hybrid fiber.The mechanical characteristics friction and wear properties were measured by shear intensity testing machine,Rockwell hardness tester and constant speed tester.The influence of each influencing factor on the performance of friction material was investigated by rescaled range method.The optimal formulation was screened by FCA method.Its surface morphology of the wear surface was characterized by SEM,and the wear mechanism of the friction material was investigated by energy spectrum analysis.The results showed that the phenolic resin had the greatest effect on the hardness of the low-resin matrix friction material,and the wear mechanism of the friction material altered by its content.Copper fiber produced a transfer film on the friction surfaces during friction process,which can remove the high heat that produced by friction and reduce the thermal recession.Flake graphite has excellent lubricity to ensure the high adhesion of friction surface,however,excessive dosage would reduce the friction coefficient of friction material.The porous structure of coke can effectively absorb the gaseous substances released by the decomposition of organism and control brake noise,but excessive coke would aggravate the wear of friction material.Comprehensive consideration,the formula F8(phenolic resin 9wt.%,nitrile rubber powder 3wt.%,aramid pulp 4wt.%,compound mineral fiber 14 wt.%,copper fiber 15 wt.%,petroleum coke 8wt.% and flake graphite 12 wt.%)was the optimal formula designed for this formula.The porosity of the sample was high,which can effectively control the braking noise.Its hardness was moderate.The friction material and the brake disc have good adhesion during braking.The friction surface had no obvious carbonization layer and the friction coefficient was stable.Its wear mechanism was abrasive wear and the wear rate was low.The process parameters were optimized for the obtained formula.Orthogonal test was used to optimize design the forming pressure,hot-pressing temperature,compress time and heat treatment time.The effects of process parameters on the properties of friction materials were analyzed,and the optimum process parameters was screened out.The results showed that the hardness of the low-resin friction material most influenced by forming pressure,coefficient of friction most impacted by hot-pressing temperature,wear rate most affected by heat treatment time.For the selected optimal formula,the optimum combination of process parameters was: forming pressure was 20 MPa,hotpressing temperature was 170?,compress time was 5min and heat treatment time was 8h.