Computational tools and design of lightweight composite hydrogen tanks

Licentiate thesis, 2025

The transition of the aviation industry towards zero carbon emissions has been the subject of ongoing research due to the challenges in aeroengine technology, aircraft level integration and alternative fuel storage. In this context, hydrogen-powered aircraft show a great potential in terms of mass specific energy and reduction of emissions (CO2 and NOx), which has triggered attention to lightweight composite hydrogen tanks. However, cryogenic storage conditions impose major challenges in the design due to high-cycle thermomechanical fatigue and fracture at extremely low temperatures (-253°C), at which conventional laminated composites are not suitable and therefore heavier multilayer designs with metallic materials have been employed in the industry. In recent years, ultra-thin ply composites have shown promising advantages in terms of mechanical properties and strength compared to conventional composites. The research problem addressed in this thesis is based on the exploration and computational modelling of ultra-thin ply composites to evaluate new lightweight hydrogen tank designs. The research goals include the development, numerical implementation and validation of constitutive models, failure criteria, and fatigue life models of thin-ply composites.

In the first paper, a numerical framework for modelling tow-based discontinuous composites (TBDCs) is developed using a multi-scale approach and computational homogenisation to predict the elastic properties from statistical volume elements (SVEs). The framework is validated for three TBDC material systems, i.e. thick, thin, and ultra-thin tow systems.

The second paper exploits the developed models to study the significance of material design parameters both at tow and plate levels. Specifically, a parametric study based on this approach has been used to evaluate the impact of parameters such as the tow modulus, in-plane tow aspect ratio, tow thickness, plate size, and preferred fibre orientation distributions (FODs). A sensitivity analysis is performed to compare and quantify the effects. Key findings for future material optimisation are reported.