Mechanical stress and strain investigation of sulfonated Poly(ether ether ketone) proton exchange membrane in fuel cells: A numerical study

Mechanical durability of hydrocarbon-based proton exchange membranes in long-term fuel cell operation is vital for their successful commercialization. Herein, a complex finite element model is developed that couples electrochemical performance of sulfonated poly(ether ether ketone) (SPEEK) membrane with its mechanical response at different operating conditions to predict the susceptible sites to mechanical failure. To this end, the impacts of cell voltage (0.1–0.9 V), operating temperature (30–80 °C) and backpressure (0.3–1.5 bar), inlet reactants relative humidity (30–100%), and clamping pressure (1–5 MPa) on hydration and consequently, stress and strain formation in the SPEEK membrane are investigated. Results suggest that SPEEK membrane, particularly at the channel outlet, undergoes the greatest swelling-induced degradation when the cell is running at low voltages, high temperature and backpressure values. Clamping pressure, however, imposes compressive stress and thinning upon the land region and is the dominant factor compared to hygrothermal swelling, albeit high hydration level shifts the maximum stress to the channel region. Despite superior resistance to different hygrothermal conditions and lower chance of thinning under the clamping pressure, Nafion membrane exhibits a relatively higher risk of wrinkle deformation under compression. This study provides insights into the mechanical response of hydrocarbon-based membranes under various fuel cell conditions.