Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Jiang, Liying

Abstract

As a typical type of soft electroactive materials, dielectric elastomers (DEs) are capable of producing large voltage-induced deformation, which makes them desirable materials for a variety of applications in transduction technology, including tunable oscillators, resonators, biomimetics and energy harvesters. The dynamic and energy harvesting performance of such DE-based devices is strongly affected not only by multiple failure modes such as electrical breakdown, electromechanical instability, loss-of-tension and fatigue, but also by their material viscoelasticity. Moreover, as suggested by experiments and theoretical studies, DEs possess nonlinear relaxation processes, which makes modeling of the performance of DE-based devices more challenging.

In this thesis, by adopting the state-of-art modeling framework of finite-deformation viscoelasticity, the effects of nonlinear viscosity of the polymer chains on the oscillation and frequency tuning of DE membrane oscillators are firstly investigated. From the simulation results, it is found that the nonlinear viscosity only affects the transient state of the frequency tuning process of DE oscillators. Secondly, with both finite-deformation viscoelasticity and deformation-dependent viscosity of polymer chains considered, the energy conversion efficiency and harvested energy of dielectric elastomer generators under equi-biaxial loading are also examined. It is found that when a nonlinear viscosity model is used, DE generators appear to reach an equilibrium state faster and the nonlinear viscosity significantly influences the energy harvesting performance. The modeling framework developed in this work is expected to provide useful guidelines for predicting the performance of DE-based oscillators and energy harvesters as well as their optimal design.

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