Hydrogen Technology New Manufacturing Processes for CFRP Hydrogen Tanks

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Fraunhofer IFAM Forschungszentrum CFK Nord

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Lightweight and at the same time dense hydrogen tanks are a central challenge for aviation. New processes for surface treatment, coating, and automated manufacturing are intended to provide a solution.

Researchers at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM are developing technologies for the resource-efficient production of hydrogen tanks made of carbon fiber reinforced plastic (CFRP) in the "Hytank" project. The aim is to produce lightweight, dense, and reliable tank structures under cryogenic conditions, for example, for aviation.

Liquid hydrogen (LH₂) is considered a promising option for future aviation propulsion systems. However, the tanks must withstand extreme requirements. At temperatures as low as -253°C (-423 °F), they must be lightweight, permanently sealed, and mechanically durable. CFRP provides suitable conditions for this but requires adapted manufacturing and joining technologies, especially for double-walled tank structures with insulating vacuum between the inner and outer shells.

Technologies for CFRP Hydrogen Tanks

In the "Hytank" project, the Fraunhofer IFAM developed an integrated approach along the entire process chain. This ranges from surface pretreatment to barrier coatings to automated manufacturing on a 1:1 scale.

A focus was placed on the pretreatment of CFRP surfaces to ensure high adhesive strength for subsequent coatings. Various methods were investigated, including atmospheric pressure plasma, VUV irradiation, and laser treatment. Depending on the method, these improve wettability, chemically activate the surface, or remove adhesion-critical residues. For example, atmospheric pressure plasma treatment increases wettability and adhesion without significantly thermally or mechanically stressing the surface. VUV irradiation activates the surface by introducing polar functional groups, while laser treatments enable precise cleaning and surface activation.

Additionally, the team developed coating systems based on polymer binders with barrier pigments to reduce the gas permeability of polymer-based tanks. The layers extend the diffusion path for gas molecules, helping to minimize hydrogen leakage and limit moisture ingress. At the same time, they support the stabilization of the insulating vacuum in double-walled tank structures and enhance operational safety.

Automated Large-Scale Manufacturing

Technologies for mechanical processing, precise positioning, and adhesive bonding were developed for production. A modular assembly system enables the handling of large-format CFRP structures and supports scalable manufacturing.

A robot-guided end effector ensures reproducible adhesive application even on curved surfaces. The joining partners are then automatically positioned and connected. Accelerated curing processes shorten production time.

Industrial Implementation and Applications

The results show that automated processing, joining, and assembly processes for CFRP hydrogen tanks are fundamentally feasible. For industrial implementation, robust strategies for tolerance control, gap management, and process stability are particularly required.

The developed technologies can help make hydrogen tanks lighter, denser, and more efficiently producible. This applies not only to aviation but also prospectively to applications in shipping and hydrogen infrastructure.