CRYOH2

DESCRIPTION

The storage of liquid hydrogen (LH₂) in composite cryogenic tanks for aviation presents major technological challenges that currently lack viable solutions. Addressing these challenges requires a multidisciplinary effort involving advanced tank engineering, materials science, thermal management, and manufacturing technologies. The CRYOH₂ project aims to develop the experimental and technological foundations necessary for designing and validating reliable, lightweight, and safe composite LH₂ storage tanks for next-generation hydrogen-powered aircraft.

From a system perspective, four main technological areas are critical: (1) the engineering of the tank, including design of spherical or cylindrical laminates, cryogenic strength criteria, fatigue and certification under aeronautical standards; (2) thermal management, ensuring minimal boil-off and maintaining 20 K temperature stability through optimized insulation and active control systems; (3) materials behavior, particularly hydrogen permeability, cryogenic embrittlement, and fire safety; and (4) manufacturing scalability, involving the industrialization of autoclave, filament winding, or automated tape placement (ATP) processes for aircraft integration.

A key technological objective is the reproduction of real service conditions of LH₂ tanks in the laboratory to understand material behavior under combined thermal and mechanical loading at cryogenic temperatures. This requires reproducing multiaxial thermo-mechanical stresses and monitoring material degradation over time. The resulting insights will guide the selection of optimal materials and structural designs, ensuring mechanical integrity, reliability, and hydrogen tightness in operational conditions.

To achieve this, several experimental developments are proposed:

• O1 – Thermal fatigue testing at cryogenic temperatures: Design of a controlled LN₂-based system capable of reproducing cyclic cooling from ambient to 77 K–20 K without inducing thermal shock, while optimizing efficiency and safety for high-cycle tests.
• O2 – Mechanical fatigue testing at cryogenic temperatures: Development of a novel biaxial loading system capable of reproducing the combined pressure-temperature service conditions of a cylindrical or spherical tank, ensuring long-duration fatigue testing under representative stress states.
• O3 – Measurement of gas permeability in composites: Implementation of a helium-based setup (as a safe surrogate for hydrogen) to quantify permeability under different mechanical loads (uniaxial/biaxial) and temperatures (RT–20 K), including post-fatigue specimens to evaluate the influence of microcracking on leak behavior.
• O4 – Thermal expansion measurements: Design of a dedicated cryogenic dilatometer to determine the coefficients of thermal expansion (CTE) of composite laminates from RT to 20 K, allowing prediction of residual thermal stresses and microcrack formation.
• O5 – Damage detection and inspection methods: Development of advanced non-destructive techniques (X-ray tomography, laminography, optical systems, and penetrant infiltration) for the quantification and localization of microcracks and their correlation with permeability data.

In parallel, the project explores strategies to minimize microcracking and hydrogen leakage, including the use of thin-plies, graphene-reinforced resins, and novel thermoset or thermoplastic formulations. These approaches aim to enhance the intrinsic impermeability and durability of cryogenic composites.

Overall, CRYOH₂ will deliver new experimental methodologies, testing infrastructures, and material solutions to enable the safe deployment of composite LH₂ storage tanks in aviation—paving the way toward sustainable, hydrogen-powered flight.