Temperature effects on the dynamic response of viscoelastic dielectric elastomer

Viscoelasticity and temperature can significantly affect the performance of a dielectric elastomer. In the current study, we use a thermodynamic model to describe the effect of temperature and viscoelasticity on the electromechanical response undergoing a cyclic electric load by taking into account of the temperature dependent dielectric constant. Because of the significant viscoelasticity in the dielectric elastomer, the deformation and the nominal electric displacement can not keep in phase with the electric field at low frequencies. The results show that the magnitude of the cyclic electromechanical actuation strain increases with the decrease of the temperature and decreases with the increasing frequency, and viscoelasticity can result in significant hysteresis for dielectric elastomers under a relative low temperature and a low frequency.

Experimental investigation on electromechanical deformation of dielectric elastomers under different temperatures

Under an applied voltage, dielectric elastomers （DEs） produce an actuation strain that is nonlinear, partly because of the material properties. In this study, an experimental characterization is conducted to evaluate how the ambient temperature and pre-stretch affected the actuation performance. For DEs with a pre-stretch of 2 × 2, an increase of temperature from -10° to 80° results in a variation in the actuation strain of more than 1700%. Low pre-stretched DEs are more susceptible to temperature change; while highly pre-stretched DEs are relatively insensitive to temperature, because in this case the energy conversion was dominated by mechanical stretching, rather than thermal conduction, during the actuation.

Constitutive relation of viscoelastic dielectric elastomer

In this paper, we present a modified model describing the constitutive relation of viscoelas-tic dielectric elastomer （DE）. The uniform uniaxial tension-recovery experiment was carried out at different stretching rates. Based on Yeoh hyper-elastic model, model-fitting approach is put forward to obtain the relationship between parameters of Yeoh model and stretching rate, thus the modified model was obtained. From the approximate relationship between harmonic motion and uniform reciprocating motion, the stress-strain curve in the recovery process was also identified through the hysteresis between stress and strain. The modified model, with concise form and evident physical concept, can describe the strong nonlinear behavior between deformation and mechanical stress of the material in a common stretching rate range （from 0.01s^-1 to 0.8s^-1 at least）. The accuracy and reliability of the modified model was examined.

Electromechanical performance of a viscoelastic dielectric elastomer balloon

In this paper,we present a theoretical study about the effect of viscoelasticity on the electromechanical performance of a dielectric elastomer(DE)balloon.The thermodynamic dissipative model is given and the equation of motion is deduced by a freeenergy method.It is found that when the balloon is only subject to the pressure or a static voltage,it may reach a state of equilibrium after the viscoelastic relaxation.When the static voltage exceeds a certain value,the balloon will never reach the equilibrium and be in failure eventually.When the voltage is sinusoidal,the balloon will resonate at multiple frequencies.The study result indicates that the natural frequency is independent on the viscoelasticity.However,the presence of viscoelasticity can reduce the amplitude and increase the mean stretch of the DE.

Energy harvesting performance of viscoelastic polyacrylic dielectric elastomers

Viscoelasticity dissipates the mechanical energy,leading to a reduction of energy conversion efficiency in both dielectric elastomer(DE)actuators and generators.By measuring the uniaxial tension-recovery experiments of very-high-bond-based DE,this article quantitatively presents the effect of viscoelasticity on energy harvesting performance of DE generators.By employing a DE strip energy harvester with constant surface charge,an analytical model is established to calculate the generated electrical energy and energy conversion efficiency.Numerical results demonstrate that viscoelasticity has a significant influence on DE energy harvesting performance.