Performance sensitivity of hybrid phenolic composites in friction braking: Effect of ceramic and aramid fibre combination

Hybrid phenolic composites based on combination of ceramic (alumino silicate based fibres) fibre and aramid fibre were fabricated followed by their characterization and tribo-evaluation in friction braking mode. The tribo-performance in terms of their friction-fade and friction-recovery behaviour has been rigorously evaluated while synchronously taking into account of the in situ braking induced temperature rise in the disc at the braking interface on a Krauss friction testing machine following ECE regulations. The friction-fade behaviour has been observed to be highly dependent on the fibre combination ratio i.e. fade followed a consistent decrease with the decrease in the ceramic fibre content, whereas the frictional fluctuations in terms of μmax–μmin has been observed to decrease with the increase in aramid fibre content. A higher recovery response is registered when the ceramic fibre concentration is adequately balanced with aramid fibre content. The analysis of friction performance has revealed that the fade and static friction response are the major determinants of overall frictional response whereas contributions from recovery and frictional fluctuations have been counterbalancing. The interdependence of fade–recovery-disc temperature rise-wear characteristics have been intensively analyzed and a semi-empirical “composition domain-performance attribute” thematic correlation is established. Worn surface morphology investigation using scanning electron microscopy (SEM) has been carried out which has revealed that the dynamics of formation–destruction of contact patches (friction-layers) and topographical attributes largely influence the friction and wear performance of such composite brake-pads.

Research highlightsDesigning friction materials with enhanced and reliable performance has long been claimed as a problem of multi-stage optimization right from selection of ingredients to processing till reaching at the appropriate set of performance criteria. It was well reported that fibres play a very crucial role which is functionally significant from wear stabilization, wear minimization, friction optimization under a dynamic set of operating variables such as braking force, sliding speed, braking duration and braking temperature. These comprehensive discussions and findings pertaining to the performance of composite friction materials has led to many modifications in the composition and fabrication of such composites where invariably the fibrous component has been suggested to be the class of ingredients which needs special attention not only in selection, incorporation but also in judiciously choosing the right combination of fibres. Therefore, we believe that this type of study will be helpful for the readers of the ‘Wear’ who are looking for developing a new kind of materials for high temperature wear and friction performance. Further, hence we consider that this article justifies its publication in the ‘Wear’.