Thermo-mechanical analysis and structural modification of the boss–liner interface in Type IV hydrogen pressure vessels

Type IV hydrogen pressure vessels rely critically on the boss–liner interface for sealing, which is challenged by coupled temperature and pressure variations. Since the localized evolution of interfacial contact behavior lacks sufficient quantitative characterization, this study proposes an integrated framework combining high-resolution thin-film pressure sensing with full-scale thermo-mechanical finite element (FE) modeling. Compression tests on modified LLDPE liners from −40 °C to 90 °C revealed pronounced temperature-dependent stiffening and softening. By embedding the temperature-dependent elastoplastic behavior with anisotropic thermal expansion into vessel-scale simulations, we tracked the evolution of contact stress throughout the manufacturing cooling and service stages. These numerical predictions were further corroborated by macroscopic burst and pressure-holding tests, confirming the structural integrity and macroscopic sealing capacity of the vessel. Crucially, our quantitative analysis uncovered the distinct functionalities of the labyrinth interface: radial grooves serve as the primary sealing zone by maintaining sufficient contact pressures across the investigated pressure–temperature conditions, while axial grooves primarily provide mechanical interlocking to restrain relative boss–liner deformation. Furthermore, to advance structural optimization, we demonstrated that replacing sharp right-angled grooves with rounded fillets effectively mitigates potential stress concentrations, promotes smoother stress transfer, and maintains the mechanical robustness of the seal. This study provides critical mechanistic insights and a robust design strategy for enhancing the thermo-mechanical sealing reliability of high-pressure hydrogen storage systems.