Electro-viscoelastic Modeling of Electroactive Polymers

Abstract: While traditionally treated separately, the research disciplines dealing with electromagnetic fields respectively continuum mechanics are naturally connected. Not only are the basic equations formulated in a similar way, but the presence of electromagnetic fields affect the balance equations of continuum mechanics and likewise, the presence of material continua affect the electromagnetic fields. For certain classes of materials, the interactions between electromagnetic fields and the mechanical continuum is notably present. Such materials include piezoelectrics, which deform in the presence of electric fields and reversibly generate charge when they are deformed. Piezoelectric materials have been known for a long time and are used in a wide variety of technological applications. More recently, other materials where electromagnetic fields give rise to mechanical effects have been discovered and made use of. Electroactive polymers (EAP) is one class of such materials. The EAP considered in this thesis react to electric input by mechanical deformation. It has been shown that they have properties that make them comparable to natural muscle. Areas where EAP are considered include biomimetics and microrobotics, where traditional engineering materials may not be possible to use. In this thesis, these materials are treated from a continuum mechanics point of view. A phenomenological constitutive model is established which include the electromechanical behavior as well as mechanical properties traditionally associated with elastomers, such as viscosity. Furthermore, the balance equations relevant for electromechanical continua are solved numerically by means of the finite element method for some representative boundary value problems.