Friction Performance Improvement of Phenolic/Rockwool Fibre Composites: Influence of Fibre Morphology and...

The size and morphology of reinforcing fibres have a great influence on organic brake friction composite material properties and performance. This research aims to establish the link between friction material microstructure heterogeneity induced by rockwool fibre morphology and distribution and the resulting tribological behaviour. The adopted approach is based on simplified formulations designed to limit synergistic effects by reducing the number and size distribution of constituents. Two simplified materials are developed with different rockwool fibre size and morphology. The first material is elaborated with calibrated fibre balls, and the second one is performed with separated fibres. Friction and wear behaviour are correlated with thermal phenomena in order to reveal wear mechanisms and thus understand the link between microstructural characteristics and the resulting tribological behaviour. It was found that a regular size and distribution of rockwool fibre balls induce better tribological behaviour and enhance wear resistance. Indeed, a homogeneously distributed porosity, which is induced by fibre balls, favours the development and preservation of the load-bearing plateaus in the contact. This, consequently guarantees a stable friction and a reduced wear rate. Consequently, reducing microstructural heterogeneity, resulting from rockwool fibre morphology and distribution, improves the performance of composite friction material.