Preload driven degradation model and life prediction of automotive PEM fuel cell stacks

Bolted joints are critical for maintaining the sealing and internal contact pressure of automotive proton exchange membrane fuel cell (PEMFC) stacks. However, existing durability models typically assume static mechanical boundary conditions, neglecting the dynamic decay of clamping force induced by road excitation and its cascading impact on electrochemical performance. To bridge this gap, this study proposes a novel comprehensive degradation framework that explicitly couples vehicle-level vibration, fastener loosening dynamics, and functional layer damage mechanisms. Unlike traditional approaches, a system-level PEMFC model is integrated with a mixed fastener loosening model accounting for both frictional rotational slip and accumulated plastic deformation under real-world proving ground road spectra. The time-varying clamping force is mapped to the stress evolution within the stack, driving physics-based damage accumulation in the gas diffusion layer (GDL), membrane (PEM), and catalyst layer (CL). Numerical results reveal a non-linear sensitivity of stack life to preload: insufficient preload triggers rapid rotational loosening. In contrast, excessive preload accelerates thread plasticity, creating a mechanistic trade-off that defines a narrow optimal design window. Crucially, the study quantifies that moderate preload loss can lead to significant power capability reduction before any structural failure occurs. This work provides a pioneering quantitative tool for automotive engineers to optimize stack assembly strategies and predict on-board durability by linking chassis vibration directly to electrochemical aging.