A NOVEL COUPLED MECHANICAL-PERMEABILITY APPROACH FOR PREDICTING HYDROGEN LEAKAGE IN LH2 COMPOSITE TANKS

Kurzfassung

As the world advances toward a sustainable future, hydrogen has emerged as a transformative alternative to conventional fossil fuels, offering the potential for zero-emission aviation. Despite this promise, one of the primary obstacles lies in storage. Hydrogen, being the smallest and most diffusive molecule, easily penetrates materials, particularly fibre-reinforced composites, where microscopic damage can create pathways for leakage. Understanding and predicting this phenomenon is critical not only for minimizing hydrogen losses but also for preventing explosions, given hydrogen’s wide flammability range. This study presents a modelling strategy to simulate hydrogen permeability in composite laminates, explicitly accounting for microscale defects and inter-fibre cracks. The approach integrates a coupled mechanical-permeability framework based on Darcy’s law. Continuum Damage Mechanics is correlated with the permeability coefficient, establishing a novel link between crack opening displacements and permeability, a concept not previously extended to gas-leakage modelling. The methodology is applied to analyse the influence of ply thickness and crack density on leak rates. Results demonstrate that thin plies act as effective barriers, delaying the onset of leakage and reducing overall permeability. Furthermore, the framework is extended to estimate leak rates in laminates after a loading cycle, producing values consistent with reported experimental data. Building on these findings, a leakage onset criterion is proposed to compute the critical leak rate for composite tanks. Overall, the study provides a predictive tool for assessing hydrogen leakage onset and rate in composites. While the results are presented for representative volume element laminate models, the method is readily applicable to full-scale hydrogen tanks.