Separable finite viscoelasticity: integral-based models vs. experiments

In the present paper, the predictive capabilities of some integral-based finite strain viscoelastic models under the time-strain separability assumption have been investigated through experimental data for monotonic, relaxation and dynamic shear loads, in time and frequency domains. This analysis is instigated by experimental investigation results on two vulcanized carbon black filled rubbers. A unified identification procedure has been deployed to all models to determine the constitutive parameters. The monotonic tests were performed to capture the rate dependent and the long-term response of the materials. For the purely hyperelastic response, we considered the proposed hyperelastic potential proposed in Abaqus for incompressible materials. Relaxation tests were intended to identify the time-dependent material properties, and completed with a dynamic mechanical analysis. Models under consideration are Christensen, Fosdick & Yu, a variant of BKZ model, and the Simo model implemented in Abaqus. In the time domain, for each test case and for each model, the nominal stress is hence compared to experimental data, and the predictive capabilities are then examined with respect to three polynomial hyperelastic potentials forms. The dynamic properties had been investigated in the frequency domain with respect to the frequency and predeformation dependencies, and then comparison conclusions have been drawn.