The Netherlands Aerospace Centre (NLR) together with Toray Advanced Composites and 12 other parties take part in the Netherlands liquid hydrogen (LH2) composite tank consortium which is funded by the Netherlands research & development mobility (RDM) Fund. The goal of the RDM project NLR takes part in is to develop a long-life, fully composite LH2 tank for civil aviation. Microcracking and the subsequent hydrogen permeation remain the biggest challenges. This study encompasses three fundamental facets to test and select composite materials: a comprehensive investigation into material behavior, the formulation of a Finite Element Method (FEM) model, and a partial experimental verification of said FEM model. The latter integral component involves an extensive testing system that includes room temperature and cryogenic tensile tests, permeability assessments, and microcrack evaluations facilitated by optical microscopy. During the experiments there is focussed on the critical microcrack density and material selection criteria such as ply thickness.

Hydrogen is one of aviation's most promising fuel alternatives in the coming years. However, to store it, a large and light vessel is needed.

The solution to this problem can be the carbon fibre fuel tank. Composite structures provide significant weight savings, which is crucial in this application. However, despite its superior performance, the hydrogen molecules permeate through the CFRP tank wall. Hence, researchers must first understand the driving phenomena to design a safe and robust hydrogen tank. The only proven way to do this is through experiments, but they must also be carefully considered to deliver representative results.

In this research, the question of how to perform the permeation and leakage testing of the CFRP laminates to accurately represent the behaviour of a full-scale hydrogen tank is being answered. The numerical analysis method has been used to evaluate different testing parameters and aid the development of the new testing rig. This thesis is the collaboration between the TU Delft and the DLR.

Thermoplastic composite materials are increasingly used in aircraft construction due to their high-mechanical properties, toughness, rapid processing rates and reprocessing possibilities at their end-of-life. In the production thermoplastic composite parts, 10-40% of the material remains unused, so-called production waste. Despite being a high-performance material that can be re-processed, real-world applications of the material into structures or products are lacking. This research explores how the thermoplastic composite production waste material can be utilised by designers and engineers, by demonstrating its use in a design process of new applications. This exploration resulted in the design of a structural member, that can be tailored to a specific function, and a design of a pedestrian bridge, which aims to stimulate the creative use of the material. By evaluating the design process, a framework is proposed which engineers and designers can utilise to design new applications from composite waste material.

Traditional manufacturing techniques for hydrogen pressure vessels have inherent constraints in the possible geometrical and structural optimisation. Using 5-axis Additive Manufacturing (AM) allows for a far greater shaping freedom. This thesis will provide a new manufacturing method for pressure vessels with 5-axis AM. Using the highly anisotropic Liquid Crystal Polymers (LCP) provides both the required hydrogen permeability performance, for storing gaseous hydrogen, as well as opening up a large potential for structural optimisation. LCPs in their additively manufactured form are tested for hydrogen permeability, in order to asses the effect of AM on the bulk permeability properties of this material. Furthermore the 5-axis AM process is developed for LCP pressure vessels, culminating in a series of pressure tests on additively manufactured specimens. These specimens provide a proof of concept for the manufacturing method, which is a starting point for expanding the geometrical and structural optimisation of pressure vessels designs.