Multiaxial deformation and failure of acrylic elastomer membranes

Dielectric elastomers are increasingly used for so called electro-active polymer actuators, sensors and generators. The materials are typically shaped as thin membranes loaded with an electric field in thickness direction. To increase the electromechanical performance, the membranes are pre-stretched with an in-plane area stretch up to 36. These large deformations may lead to rupture and thus impair the mechanical integrity of the devices.This work reports about a systematic investigation of the multiaxial deformation and mechanical failure characteristics of the acrylic elastomer membrane VHB 4910. Different tensile plane stress configurations were experimentally investigated using a large number of samples. Uniaxial and pure-shear tensile tests as well as membrane inflation tests were performed. Results of ultimate stretch, critical stress and stored deformation energy are reported along with stress–stretch relations for the three different kinematic configurations.The critical value of the maximum principal stretch at failure is found to be in the range of 9 and to be relatively independent of the imposed state of deformation. This is attributed to local failure initiating at stress rising features at the edges of the membranes. Stress concentrations at notches or load introduction regions were observed to dominate the mechanical failure behavior of VHB 4910.The present data are used to investigate the predictive capabilities of different nonlinear constitutive models previously proposed for VHB 4910. Limitations of the applicability of these models are shown for very large deformations and uniaxial stress states. A new set of parameters is determined for a simple Yeoh-model formulation to overcome these limitations.