The constitutive relation of silicone rubber soft active materials

Silicone rubber is a common dielectric elastomer material. Actuators made from it show excellent activate properties including very large strains (up to 380%), high elastic energy densities (up to 3.4 J/g), high efficiency, high responsive speed, good reliability and durability, etc. When voltage is applied on the compliant electrodes of the dielectric elastomers silicone rubber, the polymer shrinks along the electric field and expands in the transverse plane. In this paper, a theoretical analysis is performed on the coupling effects of the mechanical and electric fields. A nonlinear field theory of deformable dielectrics and hyperelastic theory are adopted to analyze the electromechanical field behavior of these actuators. Applied elastic strain energy function is obtained from the representative Yeoh model. The electric energy function involves invariant and variable dielectric constant respectively. Then deduce the constitutive relation for the dielectric elastomer film actuator based on the selected function. Also the mechanical behavior of the dielectric elastomer silicone rubber undergoing large free deformation is studied. The constitutive modules of dielectric elastomer composite under free deformation and restrained deformation are derived. The Barium Titanate (BaTiO3) with high permittivity was incorporated into the raw silicone to fabricate a new dielectric elastomer, the experimental results that the elastic modulus and dielectric constant were significantly improved. Finally the Yeoh model was developed to characterize the elastic behavior of the new dielectric elastomer. The constitutive modules of dielectric elastomer composite under free deformation and restrained deformation are derived. This is a promising analysis method for the study of the coupled fields and mechanical properties of the dielectric film actuator.