LH2-FlatLight

Fiber reinforced plastics (FRP) are the preferred choice for hydrogen tanks due to their excellent strength to weight ratio. Today's pressurized hydrogen tanks, mostly designed for the storage of gaseous hydrogen, are too much limited in their geometry to be flexible enough for many future vehicle architectures. The LH2-Flatlight project aims to develop flat, lightweight thermoplastic tanks for the storage of liquid hydrogen. In this project, different design concepts (Figure 1) will be developed and evaluated and the most suitable tank concept will be investigated in detail. In a first step, the concepts will be roughly structured on the basis of the given framework conditions and building regulations, structurally evaluated using FEM and the corresponding manufacturing concepts will be developed. Structural analysis (see Figure 2) is used to analyze the general stability of the tank and to evaluate weak points in the design. Critical areas are the ribs, which are designed to prevent the tank from buckling, and the dome cap. Both areas will be analyzed in more detail as the project progresses.

However, storing hydrogen under cryogenic conditions places special demands on the tank materials. In particular, the thermal stress caused by the filling of the tank and the final load during operation lead to temperature fluctuations of -250°C to +70°C in some cases. This can lead to the formation of micro cracks and, in the case of higher load cycles, leakage, which has to be recognized as a failure of the tank. Therefore, characterizing the material behavior at low temperatures with regard to possible leakage is an essential part of the project in order to design the construction against possible thermal failure. For this purpose, special measuring methods are used, which are available at the institute (e.g. X-ray microscopy) or will be procured as part of the project (permeation measuring cell), in order to investigate the micro crack formation and the H₂-permeation resistance of the materials used (Figure 3).