Relationships between the heterogeneous microstructure, the mechanical properties and the braking behaviour of an organic brake lining material

Abstract

Industrial brake lining materials are composite with complex formulations consisting of multiple constituents. Resulting from the fabrication process, the morphology and distribution of the constituents have significant influences on the future properties and braking performance. In this study, an in-depth analysis ranging from the microscale to the macroscale was performed to assess the relationships between the microstructure, the mechanical properties and the braking performance of an industrial brake lining material formulated for heavy vehicles. It was observed that the manufacturing process had different effects on the morphology and size of constituents and on their distribution in the phenolic binder. The morphologies of large organic particles such as rubber and graphite were affected by the mixing procedure, contrary to those of fibres and mineral particles. A transverse anisotropy consistent with fibre orientation due to cold preforming and hot moulding was observed. The microstructure displayed a strong local heterogeneity right up to the mesoscopic scale at which friction and wear mechanisms typically occur. The mechanical properties were analysed with regard to the heterogeneity of the microstructure to determine the scale at which these properties could be considered to be associated with a homogenised behaviour. The rubbing surface after braking showed that load-bearing localisation depends on the nature, morphology and orientation of constituents but that this heterogeneity can be of interest with regard to the braking ability.

Impact of hot molding temperature and duration on braking behavior of friction material

“…Microscopic observations revealed no mark of matrix degradation under braking solicitation as has been shown in previous work. 17 Indeed, mass temperatures recorded for materials A and B during braking (Figure 3(b)) did not exceed the degradation temperature of these materials (270 C), whereas for previous work, recorded temperatures recorded exceeded it. The worn surface of material A was characterized by flat plates of few hundred micrometers.…”

“…Microscopic observations revealed no mark of matrix degradation under braking solicitation as has been shown in previous work. 17

Figure 8.Worn surfaces of materials (a) A and (b) B (SEM-SE).

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“…Their formulation had a reduced number of constituents, derived from an industrial one. 17,18 This simplified formulation contained six constituents whose matrix was in phenolic resin binding mineral fibers and mineral and organic particles, as it was mentioned in Table 1.…”

Synergistic effects of fibre arrangements on the microstructure and properties of organic composite materials

“…which leads to a tribologically relevant behaviour compared to fully formulated brake linings. 8 One constituent of each class is used according to the class volume fraction of the original formulation. 10 This selection leads to a simplified formulation used as a baseline and given in Table 1.…”

Impact of the glass fibers addition on tribological behavior and braking performances of organic matrix composites for brake lining

“…But, this can produce less ability to accommodate to braking solicitation than the model. In conclusion, the difference in rigidity observed in both directions can be explained by the anisotropy of the materials caused by the manufacturing process that preferentially orients fibers in the transverse direction and reinforces the linings in this direction [17].…”