B5.2 - Application of physics-based finite-element tools in stiffness tailored structures for cryogenic hydrogen storage for improved mechanical and thermo-mechanical response

Summary

Type IV and V Composite Pressure Vessels (CPV) are well suited for hydrogen storage. Type IV CPVs consist of a composite shell that has been filament wound over a polymeric liner. The liner is used to make the CPV gastight, but it does not contribute to the stiffness and strength of the CPV. Type V CPVs are similar in construction to type IV CPVs, but do not have a liner. In this case the composite structure itself must be gastight to prevent the CPV from leaking. In this project, we will look at the filament- wound composite shell of the CPV, the project will therefore be relevant to both type IV and V CPVs.

The project will focus on the tailoring of thermo-mechanical properties of a hydrogen storage tank for cryogenic working conditions using variable stiffness filament winding architectures. The novelty of the research will be the tailoring of thermo-elastic response of filament-wound composite structures to optimize the gravimetric efficiency of CPVs for hydrogen storage. This requires the prediction of the stress state and failure of the laminate factoring in residual stresses of the manufacturing process and thermal stresses under cryogenic (working) conditions which need specifically developed analysis tools. Thermal stresses and different failure phenomena including failure of the vessel under cryogenic conditions will be considered in the model. Physics-based modelling approaches are being chosen in a finite element analysis framework. After validating the thermal stresses and resulting displacements for a flat plate, the complete composite pressure vessel will be modelled.

The developed analysis method will be used to tailor the thermo-mechanical response of the laminate to alleviate the thermal stresses and strains. This will allow on the one hand for a lighter and thus cheaper tank, and on the other hand could be used to create a tank that suffers less from thermal fatigue. A better fatigue life of a CPV for hydrogen storage can also be used to increase the working pressure of the tank, increasing thereby the volumetric efficiency of the system, or to reduce the structural mass of the tank, increasing the gravimetric efficiency of the system. In the final stage of the project this will be investigated as well.

Objectives

The overarching objective of the project is to make use of the directionality of composite material and its coefficient of thermal expansion to tailor the mechanical response of composite pressure vessels when subjected to large temperature differences for a better gravimetric and volumetric efficiency of the composite pressure vessel. The tailoring shall be achieved by spatial variation of the stacking sequence in the structure using non-geodesic filament winding.

This overarching objective will be achieved with the three sub-goals:

• Generate in-depth understanding of thermo-mechanical stresses that occur in a composite pressure vessel due to the filling and draining of hydrogen
• Develop a framework where the directionality of the coefficient of thermal expansion  can be used to tailor the thermo-mechanical stresses
• Link thermo-mechanical stresses to local matrix failure (crack initiation) using low-fidelity analysis tools.