Multi-physical modeling for electro- Transport and deformation of ionic polymer metal composites

A multi-physical model of ionic polymer metal composites (IPMCs) is presented in this paper when they deform under an applied voltage. It is composed of two parts, which describe the dynamic electro- Transport and the large deformation respectively. The first part describes the ion and water molecule transport, the equations of which are derived using the thermodynamics of irreversible process. Besides the gradient of the electric potential and the concentration usually considered in the previous models of IPMCs, the hydrostatic pressure gradient is confirmed to be one of the main factors induced the mass transport. The second states the eigen strain induced by the redistribution of ion and water molecule and reveals the stress field from micro to macro scale by the method of micromechanics. The elastic stress balanced with the eigen-stress including the hydrostatic pressure can influence the distribution of ion and water molecule reversely. To explore the reasonable mechanisms of the relaxation phenomena, various kinds of eigen-stresses are discussed here and preliminary numerical results evaluating deformation are given based on the classical Na⁺ Nafion type IPMC. It's obtained that the osmotic pressure is an indispensable eigen-stress to explain the complicated deformation.