Analysis of viscoelastic soft dielectric elastomer generators operating in an electrical circuit

TL;DR

This paper develops a comprehensive simulation framework for soft dielectric elastomer generators that incorporates viscoelastic and electrical effects, providing insights into their performance under cyclic loading.

Contribution

It introduces a coupled electro-viscoelastic model for predicting the behavior of dielectric elastomer generators, considering realistic material and circuit effects.

Findings

Time-dependent viscoelastic behavior significantly influences generator performance.

The model accurately captures the effects of large deformations and electrical circuit components.

Numerical simulations highlight the importance of considering viscoelasticity in design.

Abstract

A predicting model for soft Dielectric Elastomer Generators (DEGs) must consider a realistic model of the electromechanical behaviour of the elastomer filling, the variable capacitor and of the electrical circuit connecting all elements of the device. In this paper such an objective is achieved by proposing a complete framework for reliable simulations of soft energy harvesters. In particular, a simple electrical circuit is realised by connecting the capacitor, stretched periodically by a source of mechanical work, in parallel with a battery through a diode and with an electrical load consuming the energy produced. The electrical model comprises resistances simulating the effect of the electrodes and of the conductivity current invariably present through the dielectric film. As these devices undergo a high number of electro-mechanical loading cycles at large deformation, the time-dependent response of the material must be taken into account as it strongly affects the generator outcome. To this end, the viscoelastic behaviour of the polymer and the possible change of permittivity with strains are analysed carefully by means of a proposed coupled electro-viscoelastic constitutive model, calibrated on experimental data available in the literature for an incompressible polyacrilate elastomer (3M VHB4910). Numerical results showing the importance of time-dependent behaviour on the evaluation of performance of DEGs for different loading conditions, namely equi-biaxial and uniaxial, are reported in the final section.