Application of a micro/macro‐homogenization procedure to the investigation of the mechanical behavior of ionomer membranes for fuel cells

A microhomogenization/macrohomogenization procedure is proposed to compute the mechanical and swelling behavior of ionomer (Nafion) membranes for fuel cells under external compression loads. The membrane is viewed as a periodic porous media composed of a charged solid phase saturated by an aqueous electrolyte solution. We establish the equation of state in a single membrane pore based on a rigorous treatment of thermodynamic, electrostatic (Poisson–Boltzmann equation) and of mechanical equilibrium. The homogenization technique is then applied to propagate the information available in the pore‐scale model to the macroscale. Numerical experiments are performed to illustrate the results in a cylindrical pore geometry. The results show that the swelling pressure can be approximated by the osmotic pressure, which depends on the charge density at the pore walls and the pore radius. The model predicts the water content of liquid equilibrated membrane under various compression loads and the results are consistent with literature data. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1496–1509