Electromechanical performance of ionic polymer-metal composite under electrode constraint

The electro-active performance of ionic polymer-metal composite has been widely reported to be related to the strain caused by the unbalance of local water content. In this paper, the anisotropic strain under electrode constraint in ionic polymer-metal composite during water uptake was investigated. A model was proposed to claim that existence of electrode would lead to anisotropic swelling in ionic polymer-metal composite, and the strain state was significantly affected by the electrode volume proportion as well as the elasticity ratio of the electrode and polymer. Based on Nafion-Pd ionic polymer-metal composite, experiments were carried out to measure the swelling strain during saturation process. Evaluation by the proposed model showed great agreement with the experimental observation, both of which gave the conclusion that, under the surface electrode constraint, strain in the thickness direction was much larger than that in plane directions. At last, based on a formerly-established multi-physical model, it was predicted that for ionic polymer-metal composite, the anisotropy of local swelling can lead to a 10%–15% decrease of the tip displacement.