Thermo-mechanical Coupling Properties of Proton Exchange Membrane in Liquid Water

Abstract

In this study, the effects of the combination and interaction of thermal and mechanical loading on mechanical behaviors of proton exchange membranes (PEMs) under immersed condition were investigated. Experiments under two kinds of loading path were performed: the quasi-simultaneous loading path where mechanical loads and temperature occurred simultaneously and the rectangular loading path where thermal and mechanical loads were inserted in turn. The quasi-simultaneous loading path is composed of in-phase, 90° and 180° out-of-phase loading paths. Comparison between in-phase and 180° out-of-phase loading paths showed that strain accumulation under in-phase loading path mainly resulted from creep strain while that under 180° out-of-phase loading path were mostly induced by cyclic stress. Accumulation of strain was comprised of tensile strain and creep strain, and these two strain components showed different evolution trends with thermo-mechanical cycles. In addition, the modulus of the membrane was history-dependent as indicated from results of rectangular loading path. Through comparing creep strain with strain energy density which is an indicator of damage in the membrane, we came to the conclusion that creep strain contributed to the damage of the membrane in the first three cycles.