Indentation of a compressible soft electroactive half-space: Some theoretical aspects

We theoretically study the indentation response of a compressible soft electroactive material by a rigid punch. The half-space material is assumed to be initially subjected to a finite deformation and an electric biasing field. By adopting the linearized theory for incremental fields, which is established on the basis of a general nonlinear theory for electroelasticity, the appropriate equations governing the perturbed infinitesimal elastic and electric fields are derived particularly when the material is subjected to a uniform equibiaxial stretch and a uniform electric displacement. A general solution to the governing equations is presented, which is concisely expressed in terms of four quasi-harmonic functions. By adopting the potential theory method, exact contact solutions for three common perfectly conducting rigid indenters of fiat-ended circular, conical and spherical geometries can be derived, and some explicit relations that are of practical importance are outlined.

WAVES IN PRE-STRETCHED INCOMPRESSIBLE SOFT ELECTROACTIVE CYLINDERS:EXACT SOLUTION

This paper studies wave propagation in a soft electroactive cylinder with an under- lying finite deformation in the presence of an electric biasing field. Based on a recently proposed nonlinear framework for electroelastieity and the associated linear incremental theory, the basic equations governing the axisymmetric wave motion in the cylinder, which is subjected to homo- geneous pre-stretches and pre-existing axial electric displacement, are presented when the elec- troactive material is isotropic and incompressible. Exact wave solution is then derived in terms of （modified） Bessel functions. For a prototype model of nonlinear electroactive material, illus- trative numerical results are given. It is shown that the effect of pre-stretch and electric biasing field could be significant on the wave propagation characteristics.

Electromechanical Fields Near a Circular PN Junction Between Two Piezoelectric Semiconductors

We study electromechanical fields near the interface between a circular piezoelectric semiconductor cylinder and another piezoelectric semiconductor in which it is embedded. The cylinder is p-doped. The surrounding material is n-doped. The phenomenological theory of piezoelectric semiconductors consisting of the equations of piezoelectricity and the conservation of charge for holes and electrons is used. The theory is linearized for small carrier concentration perturbations. An analytical solution is obtained, showing the formation of a PN junction near the interface. Various electromechanical fields associated with the junction are calculated. The effects of a few physical parameters are examined.

RATE DEPENDENT STRESS-STRETCH RELATION OF DIELECTRIC ELASTOMERS SUBJECTED TO PURE SHEAR LIKE LOADING AND ELECTRIC FIELD

The performance of dielectric elastomer （DE） transducers is significantly affected by viscoelastic relaxation-induced electromechanical dissipations. This paper presents an experi- mental study to obtain the rate dependent stress-stretch relation of DE membranes （VHBTM9473） subjected to pure shear like loading and electric loading simultaneously. Stretching rate depen- dent behavior is observed. The results also show that the tensile force decreases as the voltage increases. The observations are compared with predictions by a viscoelastic model of DE. This experiment may be used for further studies of dynamic electromechanical coupling properties of DEs.

A FINITE ELEMENT METHOD FOR DIELECTRIC ELASTOMER TRANSDUCERS

We present a finite element method for dielectric elastomer （DE） transducers based on the nonlinear field theory of DE. The method is implemented in the commercial finite element software ABAQUS, which provides a large library functions to describe finite elasticity. This method can be used to solve electromechanical coupling problems of DE transducers with complex configurations and under inhomogeneous deformation.