The amount of leakage is the only direct indicator of the sealing performance of a proton exchange membrane fuel cell (PEMFC). In this work, a predictive model is developed to quantitatively evaluate the variation of leakage for a PEMFC under temperature cycling conditions. The method first uses the Lattice-Boltzmann method to simulate the gas flow within the contact interfacial gap at various heights. Then the finite element method is used to analyze the local and macroscale contact state of the sealing interface and to clarify the effect of contact stresses on the interfacial gap height. Finally, the generalized Maxwell model, which considers time-temperature transfer and stiffness growth, is used to calculate the interfacial contact stresses under temperature cycling. The validity of the model was verified by comparison with experimental data from the available literature. Further analysis showed that reduced start-up temperature exacerbated the stress relaxation effect and decreased the service life of the seal material. When the start-up temperature is reduced from 25 °C to −20 °C, the model predicts that the service life of the PEMFC will be reduced by 100 temperature cycles or more. The leakage variation in a cycle was also discussed, and it was found that the leakage fluctuation became more and more significant as the number of cycles increased, weakening system reliability.

In this work, a model for predicting the leakage rate was developed to investigate the effect of irradiation on the sealing performance of ethylene propylene diene monomer (EPDM) O-rings. The model is based on a mesoscopic interfacial gap flow simulation and accurately predicts the sealing performance of irradiated and non-irradiated materials by utilizing the gap height as an indicator in a mechanical simulation of the O-ring under operating conditions. A comparison with vacuum test results indicates that the model is a good predictor of leak initiation. The positive pressure leakage of the O-rings was investigated numerically. The results show the following. The sealing performance of the non-irradiated O-ring is much better than that of the irradiated one. The sealing performance is the worst at 0. 713 MGy and the best at 1.43 MGy, and the seal is maintained at an absorbed dose of 3.55 MGy. A theoretical analysis of the non-monotonic variation using the proposed model shows that the leakage behavior of the O-rings depends not only on the material properties but also on the roughness and prestressing properties. Finally, a method was proposed to classify the sealing performance, using the maximum allowable leakage rate as an indicator.