Sealant cross-section optimization and nonlinear clamping stiffness analysis in PEMFC stacks

The sealant cross-sectional geometry critically governs sealing performance, while the PEMFC stack exhibits highly nonlinear mechanical behavior during clamping due to nonlinear material behaviors. To address these dual limitations, this study systematically investigates the effects of different sealant cross-sectional configurations and temperature variations on the sealing contact pressure to determine the optimal sealant geometric design, and comprehensively analyzes the nonlinear stiffness profile of the stack during compression. The results showed that a double-hump cross-section reduces the peak contact pressure by 43.0% compared to a rectangular design. Temperature-dependent analyses revealed that the high thermal expansion coefficient of the sealant reduces the peak contact pressure by 15.8% from 95 °C to −40 °C. Three-stage compression mechanics of the stack were identified: Stage I with exclusive compressive deformation in the symmetric sealing region; Stage II with simultaneous compression development in both symmetric and asymmetric sealing regions; Stage Ⅲ where GDL-bipolar plate contact is achieved, marking the onset of concurrent compression across symmetric sealing, asymmetric sealing, and reaction regions. Experimental validation using pressure-sensitive films and 252-cell stack compression tests confirmed the analytical model. The results establish practical guidelines for sealant geometry optimization and stage-adaptive clamping strategies.