Modelling of sliding friction for carbon black and silica filled elastomers on road tracks

The paper presents an analytical multi-scale approach for the modelling of rough surfaces in regard to rubber friction properties. In addition to a fractal description of the micrometer range within the length-scale interval [5–100 μm], the macrotexture is considered via the introduction of a second scaling regime for the contact interval [300–1000 μm]. As a result, the hysteresis friction coefficient is decomposed in two distinct contributions. The macrotexture mostly contributes to hysteresis friction, while the microtexture is found to be determining for the amount of contact patches, e.g. the real area of contact. Experimental friction tests carried out for carbon black and silica filled S-SBR 5025 on rough surfaces and road pavement under wet conditions point out the relevance of a two-scaling-ranges approach for the modelling of hysteresis friction. Finally, predictions of the load dependent hysteresis friction coefficient are formulated for rough surfaces and give a deeper insight into the physical mechanisms involved in rubber friction properties.