Could you give an example of the projects you’re working on?

“In current aircraft for short to medium distance, the fuselage is made of aluminium. We’re now investigating whether it’s possible to make the hull out of carbon fibre-reinforced thermoplastic, a composite material. This can be recycled more easily than aluminium and this new material could make the fuselage up to ten per cent lighter. The intention is that this material will be used in new Airbus aircraft.”

“We recreated part of the lower half of a hull from thermoplastic, including integrating some of the systems. One advantage of thermoplastics is that they can be joined together relatively easily by welding. You don’t need coupling pieces or components made from other materials. Part of the research therefore focuses on finding the best welding techniques. The properties of thermoplastic compounds make them suitable for modular construction: pieces of the fuselage equipped with systems and interior parts can be assembled in a factory and then joined together in the final assembly. That lets you work much more easily and efficiently because you don’t get in each other’s way at the final assembly.”

“Within the STUNNING consortium, we’re working on the lower half of the hull, up to the level of the passenger cabin floor. Several European companies are involved in this consortium, including NLR, Delft University of Technology and SAM|XL, all led by GKN Fokker. It’s part of Clean Sky 2, a European cooperative programme. The upper half of the hull has also already been made through the same programme. We’re now working on connecting the upper and lower halves.”

NLR Fibre Placement Machine

 “Within the consortium, NLR was responsible for developing the aircraft’s skin, the outer layer that goes around the hull. The skin is only a few millimetres thick. It has to be extremely strong because it is the interface between the inside and outside air. We’ve managed to make a skin section of four by eight metres as a single piece of thermoplastic. That had never been done before. The larger the skin sections are, the fewer welds are needed – making the skin more lightweight and the production more efficient.”

New technology

“Aircraft manufacturers want to market a new aircraft in 2035. The new technology we’re investigating now should help achieve that. It may sound a long way off but the development process is lengthy. We need to be sure of the qualities of new materials and the structures we make with them before using them in an aircraft, of course.”

“You can think of the developments in thermoplastic as the building blocks for a new aircraft. The aircraft is lighter, so it uses less fuel. Fuselages made from thermoplastics can be used both in kerosene vehicles and in aircraft with new forms of propulsion. If we start flying on hydrogen in the future, it will have consequences for the fuselage design: the fuel tanks are in the wings in many kerosene-fuelled planes, whereas the tank for liquid hydrogen in a hydrogen aircraft would probably be in the hull. We’re also investigating the possibility of making such a tank from lightweight composites. In this process, we’re developing facilities to test the materials and structures at temperatures below twenty kelvin.”

“NLR also participates in various projects within the European partnership called Clean Aviation, the successor to Clean Sky 2. There is a lot of emphasis on propulsion technology, aircraft powered by hydrogen combustion, hybrid electric concepts and improving fuel efficiency. One of the studies NLR focuses on is high-power wiring in hybrid electrical aircraft. Another is looking at the integration of fuel cells. NLR’s contribution is in temperature control of these systems, making use of experience gained in the space sector. There is also attention for the integration of components for hydrogen propulsion into the composite construction of aircraft. This also fits in with the way knowledge was built up in previous projects within the Aerospace Vehicle Development programme.”