Capacitive Extensometry for the Estimation of Meaningful Stretch-Dependent Dielectric Strength of Dielectric Elastomer

The electromechanical performance of a dielectric elastomer (DE) is greatly influenced by the dielectric strength of the elastomeric materials. The dielectric strength of an elastomer profoundly depends on the state of mechanical stretch. In this work, the stretch-dependent dielectric strength for DE is measured for all possible modes of stretches using compliant electrodes. Dielectric breakdown measurement using compliant electrodes considers voltage-induced deformation, which reflects the actual working condition energy transduction. Hence, the measured strength is for a meaningful value of a working DE. Capacitive extensometry and optical method are the two leading methods for the same. We compare the extensometry and optical methods in estimating the true value of dielectric breakdown strength of DEs at high prestretches. Furthermore, we propose a modified thickness stretch-based power law for the dielectric breakdown strength. Using the capacitive extensometry method, we verify the model on comprehensive experimental data on three types of elastomers, i.e., acrylic, silicone, and natural rubber. This work proposes a general framework for estimating the meaningful stretch-dependent dielectric strength of DEs.