Use of lightweight materials is expanding to aircraft wheels.
Fraunhofer LBF
Fibre-plastic composites are already the material of choice for numerous components in aviation. Composite materials account for 22 per cent of the Airbus A380 and more than 50 per cent of the modern A350 XWB. Here, large parts of the fuselage and wings are made of ultra-light CFRP. Jens-David Wacker, who heads a research project at the Fraunhofer Institute for Structural Durability and System Reliability (LBF), explains that there is significant potential in the field of aircraft wheels: "Our institute has already proven that, for the automotive sector, replacing metal wheels with CFRP ones is promising for lightweight construction."
Aircraft wheels must reliably withstand the high static, dynamic and thermal loads that occur during take-off, landing and taxiing. Conventional models are usually forged aluminium components that can weigh up to 100 kilograms. Unlike automotive wheels, aircraft wheels are positioned on the landing gear axle via a tapered roller bearing arrangement. In addition, aircraft wheels comprise several parts to allow the relatively stiff tyre to be mounted. Although nose wheels, unlike main landing gear wheels, are not braked, the braked rolling condition turns out to be a critical load case for the nose wheel. Due to the high braking torque on the main landing gear, support forces of up to 16 metric tons per nose wheel are exerted on the nose landing gear.
Ten prototype nose wheels planned
When developing components made of fibre-reinforced composite, it is important to consider the possible manufacturing processes and materials early in the development process as they involve significant production limits. "Resin transfer moulding (RTM) is the process of choice for production of the aircraft wheel. This process offers many advantages in terms of possible automated production, the generation of complex component geometries and the realisation of high laminate qualities," Wacker explains. A total of ten aircraft wheel prototypes are to be produced under the project. To verify the component design, Fraunhofer LBF will test prototypes under the certification tests provided for aircraft wheels. The EU is funding the "Development of a composite wheel" project as part of the Clean Sky 2 Framework Programme.