Computational characterization on mechanical behavior of polymer electrolyte membrane based on nonaffine molecular chain network model

This paper investigates the mechanical behavior of polymer electrolyte membrane based on a nonaffine molecular chain network model (nonaffine model), which may account for the change in the entanglement situation for the physical linkages of the molecular chain during the deformation process. After the identification of the parameters used in the nonaffine model with the experimental data of the fresh membrane, a computational model is proposed for the degraded membrane, in which the swelling parts of the degraded membrane are replaced with voids. Employing the extended 2D homogenization method, the effect of the change in the entanglement situation for the physical linkages of the molecular chain and that of the macroscopic loading conditions on the mechanical behavior of the membrane with different volume fractions of voids are discussed. The results indicate that the dramatic increase in the average number of segments in a single chain, which occurs inside the microscopic sharp shear band, leads to a great strain softening after the macroscopic yield. Moreover, such strain softening tends to appear at early deformation stage for the membrane with high volume fraction of voids under high macroscopic triaxiality loading condition.