Since the water content determines

Since the water content determines the conductivity of the fuel cell, keeping the membrane fully humidified is necessary to achieve optimum fuel cell performance. Hydration /dehydration cycles are the main cause of the hygrothermal stress, which leads to the performance degradation and mechanical damage in a PEM fuel cell. Fig. 7 shows the delamination propagation (in terms of number of loading cycles) under the generated hygrothermal stress, and also the effects of the uniform and linear distribution of the hygrothermal stress on the damage state. Therefore, the absorption and desorption in the membrane due to high and low relative humidity will result in swelling and shrinking of the membrane. These relative humidity cycles lead to repeated stresses [103], which cause irreversible elongation in the membrane