Dielectric elastomer (DE) is capable of giant deformation subject to an electric field, and demonstrates significant advantages in the potentially application of soft machines with muscle-like characteristics. Due to an inherent property of all macromolecular materials, DE exhibits strong viscoelastic properties. Viscoelasticity could cause a time-dependent deformation and lower the response speed and energy conversion efficiency of DE based actuators, thus strongly affect its electromechanical performance and applications. Combining with the rheological model of viscoelastic relaxation, the viscoelastic performance of a VHB membrane in a circular actuator configuration undergoing separately constant, ramp and sinusoidal voltages are analyzed both theoretically and experimentally. The theoretical results indicated that DE could attain a big deformation under a small constant voltage with a longer time or under a big voltage with a shorter time. The model also showed that a higher critical stretch could be achieved by applying ramping voltage with a lower rate and the stretch magnitude under sinusoidal voltage is much larger at a relatively low frequency. Finally, experiments were designed to validate the simulation and show well consistent with the simulation results.
DE (dielectric elastomer) is one of the most promising artificial muscle materials for its large strain over 100% under driving voltage. However, to date, dielectric elastomer actuators (DEAs) are prone to failure due to the temperature-dependent electric breakdown. Previously studies had shown that the
electrical breakdown strength was mainly related to the temperature-dependent elasticity modulus and
the permittivity of dielectric substances. This paper investigated the influence of ambient temperature
on the electric breakdown strength of DE membranes (VHB4910 3M). The electric breakdown experiment of the DE membrane was conducted at different ambient temperatures and pre-stretch levels. The real breakdown strength was obtained by measuring the deformation and the breakdown
voltage simultaneously. Then, we found that with the increase of the environment temperature, the electric breakdown strength decreased obviously. Contrarily, the high pre-stretch level led to the large
electric breakdown strength. What is more, we found that the deformations of DEs were strongly dependent on the ambient temperature.
The performance of a charge-controlled dielectric elastomer membrane is remarkably affected by the leakage current. Based on a charge-controlled dielectric elastomer configuration, this
paper presents a theoretical study about the effect of leakage current on the performance of a dielectric elastomer membrane by spraying charge to the two surfaces of DE membrane. It is found that all of the stretch, the charge, and the electric displacement reduce gradually with
the time because of the current leakage. The leakage current reduces gradually with the time, and has an abrupt drop in the initial period and becomes gently after a relatively long time.
Based on the results of this paper, we have to keep spraying charge to make up the leaked one to maintain the charge-induced stretch.
Dielectric elastomer is able to produce a large electromechanical deformation which is time-dependent and unstable due to the visco-hyper-elasticity. In the current study, we use a thermodynamic model to characterize the viscoelastic relaxation in the electromechanical deformation and instability of a viscoelastic dielectric. The parameters in the model were verified experimentally. We investigate the time-dependent mechanical deformation, electrical breakdown strength, polarization, and the electromechanical stability which are coupled by viscoelastic relaxation. The results show the electromechanical stability has strong time-dependence, due to the stress relaxation when the pre-stretch is applied.
The electromechanical behavior of dielectric elastomer is strongly affected by the temperature. Very few models
accounting for the effects of temperature exist in the literature. A recent experiment showed that the variation of
dielectric constant of the most widely used dielectric elastomer (VHB 4910, 3M) according to temperature is relatively
significant. In this paper, we develop a thermodynamic model to study the influence of temperature on the instability in
dielectric elastomer by involving deformation and temperature-dependent dielectric constant. The results indicate that
the increase of temperature could improve the actuation stress and the electromechanical instability of the elastomer.