This paper proposes a free energy model to study the dynamic characteristics of a dielectric elastomer membrane undergoing in-plane deformation, subject to the combined loads of a mechanical press and an electric field. The natural frequency of the small-amplitude perturbation around the state of equilibrium is calculated with focus on the damping effects and the resonance phenomenon. The numerical results, such as the oscillation, phase diagrams and Poincaré maps, are presented to show the influence of the damping on the nonlinear dynamic characteristics of the dielectric elastomer. The numerical results indicate that pre-stresses, damping effects and applied voltages could tune the natural frequency and modify the dynamic behavior of the dielectric elastomer. There is a stability transition when taking the damping effect into account. The damping effect could cause the dynamic responses to constant vibration and decrease the amplitude. These conclusions may guide the exploration of high-performance dielectric elastomers under dynamic mechanical and electrical loads.

Recently, dielectric elastomer actuators (DEAs) have garnered remarkable attention mainly due to their ability of large deformation. Previously, the dynamic responses of out-of-plane deformations of inflated and clamped dielectric elastomer (DE) membranes were experimentally investigated, and a quasi-static model of large deformation concerned with the configuration was derived. However, the research work on the time-varying response of in-plane deformation of DE is insufficient. In this paper, we studied the dynamic response of the in-plane deformation of a dielectric elastomer membrane under a pure-shear state. We experimentally analysed how this response was affected by the peak voltage, frequency, pre-stretching, and signal waveform. The deformation equilibrium position of the membrane drifted severely during vibration, which may be attributable to the high viscoelasticity of the membrane and may lead to issues when designing precise instruments. We also studied how the peak voltage, frequency, pre-stretching, and waveform affected this viscoelastic drifting.

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Dielectric elastomer (DE) is a kind of electroactive polymer material, capable of large deformation up to 380%. However, under conservative operating conditions, DE is susceptible to instability with a small deformation due to various modes of failure, including electrical breakdown, electromechanical instability (EMI), loss of tension and rupture by stretch. This paper proposes a free energy model in the thermodynamic system of DE involving thermoelastic strain energy, electric energy and purely thermal contribution energy to obtain the stability conditions of all failure modes. The numerical results indicate that the increase in temperature can markedly contribute to improving the entropy production, the actuation stress and the critical nominal electric field of the DE. The increase in temperature could modify the failure modes of loss of tension and the EMI, which consequently enhances the stability of DE. Simultaneously, estimations on the maximal energy to be converted can be made from the theoretical formulation of the stability states. These conclusions may guide the exploration for high-performance DE materials under thermo, mechanical and electrical loads.

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