NONEQUILIBRIUM THERMODYNAMICS OF DIELECTRIC ELASTOMERS

NONEQUILIBRIUM THERMODYNAMICS OF DIELECTRIC ELASTOMERS

Xuanhe Zhao, Soo Jin Adrian Koh, Zhigang Suo

Abstract

This paper describes an approach to construct models of dielectric elastomers undergoing dissipative processes, such as viscoelastic, dielectric and conductive relaxation. The approach is guided by nonequilibrium thermodynamics, characterizing the state of a dielectric elastomer with kinematic variables through which external loads do work, as well as internal variables that describe the dissipative processes. Within this approach, a method is developed to calculate the critical condition for electromechanical instability. The approach is illustrated with a specific model of a viscoelastic dielectric elastomer, which is fit to stress-strain curves of a dielectric elastomer (VHB) measured at various strain rates. The model shows that a higher critical voltage can be achieved by applying a constant voltage for a shorter time, or by applying ramping voltage with a higher rate. A viscoelastic dielectric elastomer can attain a larger strain of actuation than an elastic dielectric elastomer.

The paper is in press at International Journal of Applied Mechanics