A reduced mixed finite-element formulation for modeling the viscoelastic response of electro-active polymers at finite deformation

In this work, a parameter identification procedure has been held for characterizing the widely used dielectric elastomer VHB. The calibration procedure has been performed using various experimental data found in previous works including uniaxial and multiaxial tests. Unlike the uniaxial tests, the multiaxial tests yield inhomogeneous deformation fields and, therefore, the finite-element method is adopted to obtain numerical solutions for the multiaxial tests. Here, a numerical scheme has been developed using the reduced mixed finite-element formulation, which eliminates the possible volumetric locking in electro-active polymers and enhances the computational efficiency as the static condensation is circumvented. The objective function, which calculates the discrepancy between the results obtained from the computational model and the measured experimental data, has been formulated taking into account the different types of experiments. The material parameters have been extracted when the objective function reached a minimum value, which is obtained by applying an iterative procedure using the fminsearch in Matlab. Within the extracted parameters and the developed finite-element formulation, number of simulations showing the efficiency of the computational model have been performed.