Modeling of electromechanical actuators using electro-active polymers

Abstract

Electro-Active Polymers (EAP) are smart (intelligent) materials which function comes from their electromechanical coupling (or electro-elastic). In a way, their applicability can be compared to the one of piezoelectric polymers, although their electromechanical behavior is substantially different. The EAPs are made of thin polymeric layers covered by flexible electrodes such that when subjected to high electric fields suffer large deformations. It is considered that they could have great potential for use as artificial muscles thanks to their strong energy density. They can suffer deformations up to two orders of magnitude higher than piezoelectric materials and they are more resistant and light than shape memory alloys. Therefore, most of EAP applications benefit from their ability to develop large deformations. On the other hand, this leads to substantially more complex models, if compared to piezoelectric materials for instance, in which it is necessary to characterize their material behavior using finite deformation constitutive equations. There is a number of proposed models, such as Neo-Hookean or Mooney-Rivlin, in the literature for the modeling of the nonlinear elastic behavior of these polymers. It is then worthwhile to analyze these different models and investigate the characterization of their parameters. Even the most common simplified model suggest that the induced mechanical stress is proportional to the square of the applied electric potential, leading to a nonlinear behavior. Besides, predictive models for EAP-based structures must account for geometric and material nonlinearities due to the large deformations. Therefore, the main objective of this project is to analyze theoretical and numerical models to predict the response of structures and devices that present electromechanical behavior due to the presence of actuators made of electro-active polymers.