Effects of SBR Molecular Structure and Filler Type on the Hyper-Viscoelastic Behavior of SBR/BR Tread Compounds Using a Combined Numerical/Experimental Approach

Reduction of rolling resistance in tyres plays a crucial role in reducing global warming and CO2 emissions. Consequently, the prediction of energy dissipation in tyre tread compounds has received increasing interest from tyre manufacturers to design low dissipative compounds. In the present work, a triple model based on the Ogden hyperelastic equation, Bergstrom-Boyce nonlinear viscoelastic relationship in conjunction with a stress softening equation was proposed for the prediction of the force-displacement behavior of tread compounds. Two series of rubber blends compounds based on SBR/BR solution and SBR/BR emulation reinforced by two carbon black (CB) grades and a surface-modified silica were prepared. Each series was comprised of three blends with different filler contents. The total part of filler in each compound was kept constant as 80 phr.  The first compound contained 80 phr of CB without any silica, while the second and third compounds were prepared using 20 and 40 phr silica as replacement. The mechanical behavior of the cured compounds was determined using a tensile test carried out on a ribbon type sample with 2X11 cm dimension and ATM D-412 C test specimens. An optimization loop was designed in Isight code using three Abaqus, data matching and optimization components. The developed algorithm was used for the determination of the parameters of the mentioned model. It is shown that the proposed material model and the developed numerical algorithm can predict the mechanical behavior of the compounds during a loading/unloading cycle. The trends of the variations of the predicted parameters are in reasonable agreement with macro- and micro- structure of the SBR and filler type (CB or silica). It is also found that the addition of silica to rubber compound has 25-35% decreasing effect on energy dissipation. Moreover, solution SBR has approximately 50% more reduction effect on energy dissipation compared to emulsion SBR at equal filler type and content.