Material-efficient and cycle-time-optimized industrialization of H2 pressure vessels

Hydrogen is an important component on the path to more sustainable mobility and plays a central role in the future of energy transition. As a zero-emission energy carrier, hydrogen offers an environmentally friendly alternative to conventional fossil fuels. In road transport, for example, hydrogen enables the operation of fuel cell vehicles such as cars, buses and commercial vehicles. When hydrogen is converted to electricity in fuel cells, the only waste product is water vapor, making it a clean and sustainable solution for the transport sector. However, the potential uses of hydrogen are not limited to road transportation. In aviation, hydrogen propulsion can enable the development of zero CO2emission aircraft. These could make a significant contribution to reducing aviation emissions.

While hydrogen offers promising benefits, we still face a number of challenges. In particular, there are still some hurdles to overcome in terms of efficient and safe storage. Current methods, such as pressurized and cryogenic storage, require advanced technologies to store hydrogen in sufficient quantities and at acceptable pressures. In order to promote the widespread acceptance of hydrogen as an environmentally friendly energy source for mobile applications, it is important to develop cost-effective and efficient hydrogen storage technologies. In particular, the high material costs associated with the use of carbon fibers should be taken into account. The MaTaInH2 project - Material Efficient and Cycle Time Optimized Industrialization of H2 Pressure Tanks - addresses this issue and contributes to overcoming all these challenges.

The pressurized tank is a key component for road vehicles. The project focuses on the industrialization of the hydrogen pressure tank. In order to achieve the desired cost reduction in the production of 700 bar pressure tanks, pre-impregnated carbon fiber semi-finished products are to be used and a manufacturing process adapted to them. An important part of the project was the in-depth investigation and characterization of reference materials for wet winding and towpreg winding. Samples were produced in accordance with the relevant standards, allowing detailed static mechanical tests to be carried out. These tests provided fundamental insights into various factors influencing the wet and towpreg winding process. In particular, the use of tension-compression-torsion specimens (see Figure 1) has helped to improve the understanding of the material properties. The aim was to create a comprehensive material map summarizing all relevant mechanical and process sensitive properties. The analysis of these reference materials provided a solid basis for verifying the design parameters and ensuring the reliability of the winding processes. At the same time, fatigue tests were carried out to evaluate the long-term behavior of the materials. Dynamic mechanical testing, in particular load increase tests on the ring specimen, provided valuable insight into the load capacity and durability of the materials under real-world conditions.

The project also focused on upgrading the equipment for processing towpregs. To this end, the existing winding system at IVW was successfully converted and expanded to meet the specific requirements of towpreg semi-finished products. In particular, a latest-generation 8-stand with controlled tension monitoring and an adapted towpreg winding head with individual roving guides were installed. These modifications allow the integration of towpreg materials under near-series process conditions. This strengthens the industrial comparability of the developed technologies and test results.

The planning and execution of winding tests to produce a pressure tank were key milestones in the course of the project. In order to determine the optimum structure and strength of the pressure vessels, extensive series of tests were carried out using both the towpreg and wet winding processes. Approximately 50 tanks were manufactured and used for burst tests. The laminate structure of the pressure vessels was optimized in an iterative process based on the results of the burst tests. These results provided valuable information about the weak points and load limits of the tanks. As a result, the laminate structure was adapted and improved.

In addition to commercially available towpreg materials, a towpreg developed by Technical University of Munich (TUM) was included in the test program. The material is an epoxy based towpreg that was produced and optimized by TUM. At the end of the project, several tanks were produced with this material and the layer structure for the towpreg was adapted and optimized.

MaTaInH2 project makes a significant contribution to the further development of hydrogen as a key technology for mobility. By focusing on the industrialization of hydrogen pressure tanks and the integration of new technologies such as towpregs, the challenges in the field of hydrogen storage are addressed. The investigation and characterization of reference materials, the improvement of system technology and the planning and execution of winding tests demonstrate the holistic approach within the project. The optimization of the laminate structure and the production of about 50 pressure vessels for burst tests underline the practical contribution to the efficient and safe use of carbon fibers in the production of hydrogen pressure vessels for mobile applications.