Research On The Formulation And Fabrication Process Of Resin Matrix Friction Material Used For Al-MMC Brake Disc

Low weight and high speed have been the main trends in the development of vehicles. Owing to the advantages of low density, good wear resistance and high heat conductivity, aluminum metal matrix composites (Al-MMC) are given great attention to substitute for cast iron as brake disc material. However, the traditional brake pads used for cast iron brake disc are not suitable for Al-MMC brake disc due to the difference of friction and wear characteristics between cast iron and Al-MMC. It is necessary to specifically develop the friction materials used for Al-MMC brake disc. In this thesis, the influence of resin adhesives, reinforcing fibers and fabrication processes on the friction and wear characteristics of Al-MMC / resin matrix friction material tribological systems were investigated and the preferable formulation and fabrication process of friction materials using for Al-MMC brake disc were developed.In the present study, cashew-modified resin had good heat-resistant performance, friction material fabricated by using this kind of resin exhibited low hardness, stable friction coefficient and low wear rate. This indicated that cashew-modified resin was preferable to be used as the matrix of friction material. The favorable content of cashew-modified resin and rubber powder were 22vol%~26vol% and 22vol%, respectively.The friction and wear characteristics of Steel/Cu fiber, Kevlar pulp/potassium titanate whisker and carbon fiber reinforced materials were investigated. For Steel/Cu fiber reinforced friction materials, the best friction and wear performance was obtained with the hybridization of 4vol% steel fibers and 11vol% Cu fibers. For Kevlar fiber/potassium titanate whisker and carbon fiber reinforcing systems, the preferable whiskers and carbon fibers content were 20vol% and 14vol%, respectively.The best formulations of the three kinds of fiber-reinforced friction materials were compared. The results showed that the Steel/Cu fiber reinforced friction material exhibited the highest friction coefficient and the lowest coefficient pressure sensitivity; the material reinforced by Kevlar fiber/potassium titanate whisker had the lowest wear rate and coefficient speed sensitivity; the carbon fiber reinforced material seemed not suitable for Al-MMC for its low friction coefficient and high wear rate. Moreover, the friction coefficient of the carbon fiber reinforced material changed greatly with pressure and sliding velocity. It could be concluded that Steel/Cu fiber was a promising reinforcing system of friction material used for Al-MMC brake disc.