THERMODYNAMIC MODELING OF IONIC POLYMER-METAL COMPOSITE BEAMS

A thermodynamically consistent model to simulate the electromechanical response of ionic polymer-metal composite (IPMC) beams has been developed based on Euler-Bernoulli beam theory. Appropriate assumptions have been made and suitable forms for the Helmholtz free energy and the rate of dissipation have been chosen. The governing equations, describing the actuation and sensing behavior of IPMC strips in air, have been formulated using a set of kinematic assumptions, the power theorem, and the maximum rate of dissipation hypothesis, neglecting inertial effects. The model has been extended to solve for large deformations in IPMC cantilevers with certain loading conditions. The model has been shown to simulate the electromechanical responses of both Nafion and Flemion based IPMC strips. This includes the initial overshoot followed by a gradual back-relaxation observed in the tip deflection measurements of Nafion based IPMC strips under the application of a step voltage. It has been shown that a coupled convective heating term in the rate of dissipation function is crucial for simulating this overshoot and the back relaxation.