Multi-axial viscoelastic deformation of carbon-black filled EPDM rubber

Cyclic tensile stress-strain data for a cross-linked EPDM rubber in uniaxial, biaxial and constant width modes of deformation are presented. After extraction of the rubbery and viscous contributions, the rubbery data is modelled using the Edwards-Vilgis strain energy function with parameters evolving with the maximum stretch. It is found that the cross-link density reduces with increasing stretch, but the slip-link density is invariant. The viscous contribution is a strong function of stretch but invariant of maximum stretch. This presents an opportunity to model the behavior using a strain energy function with evolving parameters in parallel with viscoelastic anisotropic flow units. Uniaxial stretch 1 2 3 4 5 6 7 T ru e S tr es s (M P a) 0 10 20 30 40 50 60 70 Figure 1. Representative uniaxial stress-strain cycles to different levels of pre-deformation. Biaxial stretch 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 T ru e S tr es s (M P a)