Research On Properties And Coupling Mechanism Of Low-Resin Friction Material Reinforced By Hybrid Fibers

With the rapid development of modern transportation industry and the enhancement of energy saving and environmental protection consciousness,friction materials are required to have fast reaction speed,low brake attenuation,high thermal stability,good wear resistance and low noise.Due to the shortage of performance in traditional friction materials and cost constraints in high performance friction materials,a new cost-effective friction materials has emerged.The method of hybrid fiber reinforced resin matrix has significant practical effect in improving performance of automobile brake pad friction material and wide application prospects.The resin based friction materials reinforced by carbon fiber,aramid fiber,composite mineral fiber and potassium hexatitanate whisker were prepared by utilizing hot-forming process.The effects of hybrid fibers on properties of resin-based friction materials were studied by combining three methods of range analysis,qualitative calculation and quantitative analysis to determine the reasonable dosage ratio of hybrid fibers.The golden ratio method was applied to optimize the proportion of reinforced fibers and orthogonal experiment was used to the formulation design.The optimization model of friction material performance was established by using Matlab software,and the best formula was screened out by fuzzy comprehensive evaluation.The microstructure of low resin-based friction material was observed by scanning electron microscopy（SEM）,surface and wear debris before and after wear were analyzed,elemental composition of worn surface was investigated by energy dispersive spectrometer,coupling mechanism was discussed.It will provide theoretical basis and support for the development of new high-performance friction materials.The following conclusions and conclusions were drawn through experimental research:（1）The results showed that hybrid fiber reinforced low-resin-based friction material exhibited excellent wear resistance and high thermal stability,its rockwell hardness was ranged from 50 to 60 HRB,and shear strength was in appropriate range of11-16 MPa.As hybrid fiber content increased from 8%to 10%,hardness and shear strength of friction materials increased by 14.5%and 31.2%,respectively.（2）When hybrid fiber content was 9.4wt.%（carbon fibers1.4wt.%,aramid fibers1.3wt.%,potassium hexatitanate whiskers1.3wt.%and composite mineral fibers5.4wt.%）,friction coefficient of friction material was maintained at 0.38⁰.42,and wear rate was only 0.12×10^-7cm³/（N·m）,F6 was the best formula of sample preferred.（3）The hexa-titanate whiskers had the greatest effect on Rockwell hardness of friction material.The aramid fiber had the most influence on shear strength.The excellent self-lubricity of carbon fiber and "transfer film" formed at friction interface not only helped to reduce the exfoliated reinforcing fibers and the filler pilling effect on substrate,but also can derive high heat generated by friction,effectively alleviate the heat decline,friction coefficient and wear rate were the most affected.（4）The results showed that the cross-coupling effect between fiber and resin,the degree of cross-linking between components and interfacial strength determined mechanical and physical properties of resin-based friction materials.The synergistic coupling effect of hybrid fiber changed friction force in the adhesion process by transfer film,and affected friction coefficient of friction material.（5）The different content of hybrid fibers and modified phenolic resin both played a role in wear mechanism of friction material from abrasive wear and thermal decomposition wear into a variety of complex mechanisms;hybrid fiber reinforced resin based friction material was sensitive for abrasive wear,the transfer film friction surface dense adhesive wear played a leading to self-cleaning effect;debris particle size can improve the transfer film,thereby reducing wear rate.