Study On The Interface Adhesion, Friction And Wear Properties Of Paper-based Friction Material

Paper-based friction material which has outstanding friction properties has been gradually applied for automatic transmissions and brake system in various vehicles and engineering machines. The interfacial adhesion between Fibre and resin has significant impact on the mechanical and firiction properties of fibre/resin composites. The research of his paper focused on the influences of fibre/resin interfacial adhesion on the mechanical and friction properties of paper-based friction material. We also investigated the effect of factors, such as dosage of fibre and filler, and press pressure, to composites. In addition, wear mechanisms of the material were discussed in this paper.The load of aramid fibre and filler showed little impact on the porous structure of paper-based friction material. The dynamic friction coefficient rose with the increase in aramid fibre dosage, whereas static friction coefficient reached its maximum value at aramid fibre content of 25%. Higher dynamic friction coefficient and static friction coefficient could be obtained at a higher content of filler dosage. A higher content of aramid fibre or filler led to a lower wear rate of the paper-based friction material and a higher wear rate of the friction disc. Increasing the hot pressure could result in a denser composite that had more resin on material surface, which led to a less porous structure. For this reason, the tensile strength and internal bonding strength decreased. On the other hand, the increasing hot pressure increased the static friction coefficient whereas deduced the dynamic friction coefficient and wear rate.The wear mechanisms of the paper-based friction material were investigated by worn surface and thermal decay analyzing. Results showed that serious abrasion and debonding occurred between fibres when material was subjected to repeated shear and compression. The fraction of fibre and the abrasion particles of filler were entrapped in the soft fibres and micro holes, and thus would not promote further wear. In addition, thermal decay also occurred to the friction material, which was mainly due to the degradation of plant fibre. These observations indicated that the main wear mechanisms are adhesion wear and fatigue wear.To investigate the influences of fibre/resin interfacial adhesion behavior on the mechanical and wear properties of paper-based composites, chlorine dioxide treatment was introduced. Fibre surface characteristics and the interfacial behaviour of the sisal fibre/phenolic resin composites were studied by SEM, AFM, and XPS. The results showed that the surface of the untreated fibre contained a large amount of lignin with granular structure and non-granular structure. The surface lignin concentration was up to 51% for the untreated fibre, and then it decreased to 24% and 20% for the ones treated with 1.5 % and 2.0% chlorine dioxide. The removal of lignin from fibre surface enhanced the interface strength of the composites, giving rise to increases by 36% and 28% in tensile strength and internal bonding strength, whereas decrease by 21% in wear rate. These results indicated that the surface properties of single cellulose fibre can be tailored to improve the fibre/resin interface. Chlorine dioxide treatment can be a potential surface modification of cellulose fibre in engineering the interfacial behaviour of composites.The infuences of microfibrillation on fibre morphology, ultrastructure, specific surface area, and tensile strength were investigated. Surface microfibrillation of cellulose fibre was adopted as a facile method for improving cellulose fibre/resin interfacial adhesion in hybrid composites composed of sisal fibre and aramid fibre. Development of microfibrils and aggregates on the fibre surface significantly increased the interfacial adhesion between the sisal fibre and resin by providing a large contact area and by inhibiting the formation of spontaneous cracks in the composites. Consequently, the compression, tensile and internal bonding strengths, and wear resistance of the hybrid composites were remarkably improved. Further research showed that microfibrillation greatly affected the properties of sisal fibre and the subsequently prepared composites. The tensile strength of the hierarchical fibre showsed no significant difference when microfibrillation was limited to S1 or the outer layer of S2 of fibre cell wall, whereas the tensile strength of composites increased. However, a serious damage of S2 layer led to deterioration in the tensile strength of hierarchical sisal fibre, which resulted in decrease in tensile strength of composites.We also investigated that the microfibrillation of nature fibre affected the friction and wear properties of paper-based friction material. The microfibrillation of nature fibre had remarkable influence on porosity, interfacial adhesion and filler retention. The nature fibre with low microfibrillation degree didn't impact on the porosity of materials, but could significantly improve the interfacial adhesion and filler retention compared with the sample without microfibrillation, which resulted in higher friction coefficient and lower abrasion. However, in the case of high microfibrillation degree, low porosity would lead to poorer heat diffusion from the work area, which gave rise to low friction coefficient and higher abrasion of the material.