Experimental Validation of A Constitutive Model for Ionomer Membrane in Polymer Electrolyte Membrane Fuel Cell (PEMFC)

The authors have implemented a nonlinear constitutive modeling for ionomer membranes with application in polymer electrolyte membrane fuel cells. The constitutive model features multiplicative decomposition of viscoelastic and plastic deformation gradient tensors, micro-mechanism inspired viscous flow rule, nonlinear viscoelastic Bergström-Boyce model, and hydration and temperature dependent elastic modulus of ionomer membrane. In this work, the authors attempted to experimentally validate the constitutive model. Experimental results obtained from uniaxial tension tests of perfluorosulfonic acid membrane (e.g Nafion® from DuPont.) under wellcontrolled environments were used to fit the model parameters, which are subsequently used in a finite element (FEM) code to predict stress and deformation of ionomers in complex loading cases. The proposed model after validation showed fairly good predictive capabilities for the large deformation behavior of Nafion membrane subjected to the creep and relaxation at different strain rates in a wide range of relative humidity.