Redefining Energy Density for an uniaxial Dielectric Elastomer Actuator

The dielectric elastomer actuator (DEA) is a technology known to potentially provide high energy density $(0. 3 - 0. 4 J \cdot cm^{-3})$. However, in the literature, few demonstrations have been done to evaluate this figure. To well understand the ability of this technology, this paper redefines the energy densities which allow to classify the DEA and better understand the values presented in the literature. For this study, the Elastosil
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film from Wacker has been used and an uniaxial planar actuator has been studied. According to the considered limits and loads, it is shown that the energy density could pass from $0. 2 J \cdot cm^{-3}$ to ten times lower. The first approach provides a theoretical value for the DEA and is called practical energy density, while the second definition (specific energy density), considers the real work provided to a constant load. The pre-stretch of the DEA is a widespread way to increase the deformation of any dielectric actuators. By keeping in mind the objective to provide energy to a constant load, the results of this study show that the obtained energy density could be doubled through this way. Finally, another biasing element with a negative force-displacement characteristic already published in the literature is investigated. The special mechanical characteristic of this element allows to increase both the displacement and the energy density. The latter provides five times the energy density obtained with the constant-stress biasing element which validates its beneficial aspect.