Experimental investigation of the electromechanical phase transition in a dielectric elastomer tube

A membrane of dielectric elastomer undergoes a large deformation when it is subjected to a voltage through the thickness. Due to the attributes of light weight and high energy density, dielectric elastomers are suitable for electromechanical actuators and generators. In this work, the phenomenon of electromechanical phase transition is demonstrated experimentally in a tube of dielectric elastomer subjected to an internal pressure, an axial force and a voltage. When the voltage exceeds a critical value, the homogeneous deformation becomes unstable, and the tube deforms into coexistent states of bulged and unbulged sections. At the transition voltage the unbulged sections gradually bulge up and propagate. Two stable states are observed at the end of the phase transition process: one is coexistent states of the bulged and unbulged sections; the other is the wholly bulged tube. The achieved maximum voltage-induced deformation of the tube is 2200% in area, and the electromechanical energy conversion density is estimated to be 1.13 J g⁻¹. These results are beyond the largest values reported in the literature. A theoretical analysis based on thermodynamics is carried out to qualitatively explain the observed experimental phenomenon. (paper)