Experimental characterization of cyclic stress-strain response and its modeling for filled SBR vulcanizates

The objective of this study is to develop a new constitutive model, which can precisely reproduce cyclic stress-strain responses of carbon black-filled SBR vulcanizates under wide ranges of applied strains and strain rates. Dumbbell specimens made from the vulcanizates were prepared for uniaxial cyclic tests. The comprehensive experimental investigations clarified that the cyclic stress-strain response for pre-strained specimens showed characteristic phenomena (stress softening, and emergences of residual strain and hysteresis loop), and the phenomena were changed with cycles. However, such changed stress-strain response recovered the initial one by relaxation treatment under an unloaded state at room temperature for a specific period; therefore, the characteristic phenomena of the pre-strained specimens were presumed to be caused by viscoelasticity. Thus, uniaxial cyclic tests for the pre-strained specimens were performed at strain rates of 0.1, 1 and 10%/s under applied strains of 50% and 100%, and their experimental cyclic stress-strain responses were reproduced by the proposed constitutive model based on hyperelasticity and nonlinear viscoelasticity.