Hysteresis friction and nonlinear viscoelasticity of rubber composites

Evaluation of tire friction is essential from the perspective of enhancing vehicle performance and improving its safety. Earlier investigations have identified rubber adhesion and hysteresis as two fundamental mechanisms underlying tire friction. This contribution aims at analyzing the effect of nonlinear viscoelastic behavior of tire treads on their hysteresis friction coefficient. Tire tread is a composite material made of synthetic or natural rubber reinforced with particles such as carbon black or silica. Hysteresis that refers to energy dissipation during a cyclic deformation is an essential feature of mechanical behavior of rubber composites. The effect of nonlinear viscoelasticity of filled rubbers on the hysteresis friction of tire treads is not well understood. In this contribution, we use an analytical model to predict the hysteresis friction of filled rubbers sliding on a rough surface. The model accounts for the nonlinear viscoelasticity of the slider subjected to finite strains. It will be shown that the kinetic coefficient of friction directly correlates with the magnitude of strain. Comparison of model results against the experimental measurements for tire tread materials reveals that the predicted friction coefficients become comparable with experimental data at large strains (8-10%). This study suggests that the nonlinear viscoelasticity of tire treads needs to be taken into account in order to have a more realistic assessment of frictional performance of tires.