Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Liying Jiang

Abstract

Dielectric elastomers (DEs) capable of large voltage-induced deformation show promise for applications such as resonators and oscillators. However, the dynamic performance of such vibrational devices is not only strongly affected by the nonlinear electromechanical coupling and material hyperelasticity, but also significantly by the material viscoelasticity. The material viscoelasticity of DEs originates from the highly mobile polymer chains that constitute the polymer networks of the DE. Moreover, due to the multiple viscous polymer subnetworks, DEs possess multiple relaxation processes. Therefore, in order to predict the dynamic performance of DE-based devices, a theoretical model that accounts for the multiple relaxation processes is very essential. In this work, by extending the general modelling framework for finite-deformation viscoelasticity, a new model that accounts for the multiple relaxation times of DEs is proposed to study the in-plane oscillation and frequency tuning of DE membrane resonators. It is found that the failure (electrical breakdown or loss-of-tension) of the DE membrane resonator could be delayed by tailoring the microstructure of the DE. In particular, resonators made of DEs with higher viscosity usually fail earlier with smaller deformation and lower resonant frequency, but they are highly adjustable to achieve similar large deformation. The desirable parameters of the tuneable natural frequency range and voltage safe operation range are also explored. Furthermore, it is more effective to tune up the resonant frequency for such DE membrane resonators. This work can provide guidelines on better predicting the dynamic performance of DE-based vibrational devices, as well as their optimal design.

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