Modelling and optimisation of Electro-Active Polymer (EAP) devices

Abstract

The control of boundary layers either for skin-friction reduction or for fight control can be achieved by their manipulation using deformable surfaces. In the case of the former, it is known that the manipulation of coherent structures in the turbulent boundary layer can lead to significant drag reductions. However, the challenge is to find actuators and sensors that are functional at these spatial scales (10 micron to 0.1 mm) and the associated temporal scale (100 kHz). Electro-Active Polymers (EAPs) provide excellent performance, are light weight, flexible, and low cost. Therefore EAPs, and in particular Dielectric Elastomer Actuators (DEAs), provide many potential applications as micro-actuators and micro-sensors. Modelling DEA devices is a cost-effective way of providing a better understanding of the devices and optimising their designs. Acquiring a model for the EAP material itself is the first essential step in DEA modelling. A modelling technique taking into account the material non-linearities and its behaviour at large deformations (`hyperelasticity') is presented in the third chapter of this thesis. The main challenge in modelling DEA devices is the modelling of their electro-mechanical coupling. Commercially available electro-mechanical modelling does not apply to non-linear materials such as EAPs. The ANSYS Finite Element (FE) software is the tool used in this work to develop a novel model presented in the fourth chapter. Various means of optimising the design of DEA devices are suggested in the sixth chapter using the developed DEA model. A novel design of an EAP-based pressure sensor is suggested in the seventh chapter; FE modelling is used to study the abilities and performance of such a device. To complete the model, its time-dependent properties are examined by a modal analysis examined in an eighth chapter. The thesis is completed by examining the potential for DEA in providing a `smart' surface for distributed aerodynamic control.