Concept development for an aircraft wheel made of fiber-reinforced plastic.
Composites, aircraft wheel, carbon fiber reinforced plastic
During take-off, landing and taxiing high static, dynamic and thermal loads occur which aircraft wheels must withstand reliably. Conventional aircraft wheels are usually forged aluminum components that can weigh up to 100 kg. With the development of an aircraft nose wheel made of carbon fiber-reinforced plastic (CFRP) as part of an EU research project, Fraunhofer LBF wants to demonstrate a lightweight potential of up to 40 percent.
Unlocking lightweight potential
Fiber-reinforced composites are increasingly being used in aviation due to their high specific stiffness and strength. Composite materials make up 22 percent of the large Airbus A380. This figure rises to more than 50% in the cutting edge A350 XWB. Here, large parts of the fuselage and the wing units are made of ultra-light CFRP. There has been no significant advancement in aircraft wheels in terms of materials used and basic design since the 1980s. Fraunhofer LBF intends to open up this field of innovation by developing a first CFRP nose wheel for an A320. It has already been possible in the Institute’s projects to demonstrate promising lightweight design potential by substituting CFRP wheels for metal in the automotive sector. When it comes to the reliable design of safety-critical lightweight parts, Fraunhofer LBF has many years of experience and is an acknowledged research partner.
Fig. 2: Sectional view of a conventional aircraft wheel (source: M. C. Niu, “Landing Gears” in Airframe Structural Design, Conmilit Press Ltd, 1988).
Fig. 3: Identification of an optimum lightweight structure by analyzing different wheel geometries regarding their stiffness.
Fig. 4: Comparison between displacements of wheel geometries under different load cases.
The development process starts with the definition phase and includes gathering all the key requirements. Among other things, this includes the interfaces to the tire and the mounting, specifications for the installation space and the load situations. Unlike automotive wheels, aircraft wheels are positioned on the landing gear via a tapered roller bearing arrangement (cf. Fig. 2). In addition, aircraft wheels are made in several parts to allow the relatively stiff tire to be mounted. Although nose wheels, unlike main landing gear wheels, are not braked, braked roll 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 occur on the nose landing gear.
Concept development is the second step in the development process. To find a concept for an optimum lightweight structure, basic geometric concepts were examined and evaluated with regard to their stiffness in relation to the loads imposed by radial load, lateral load, tire pressure and superimposed load cases (cf. Figs. 3 and 4). The result is confirmed by optimizing the system’s topology.
When developing components made of fiber-reinforced composite, it is important to deal with the possible manufacturing processes and materials early in the development process as they involve significant production limits. “Resin Transfer Molding” (RTM) is the process of choice for production of the aircraft wheel. This process offers many advantages in terms of possible automated production, the creation of complex component geometries and the realization of high laminate qualities.
The aim of the project is to produce 10 prototypes of the aircraft wheel in total. To verify the component design, the prototypes will be tested under the certification tests provided for aircraft wheels.
There has been no significant advancement in aircraft wheels in terms of basic design and materials used since the 1980s. Fraunhofer LBF wants to demonstrate the potential for new lightweight design in aircraft by developing a first nose wheel made of carbon fiber reinforced plastic (CFRP) for an A320. To identify an optimum lightweight structure, basic geometric concepts are developed in the concept phase and evaluated with regard to their stiffness in relation to various load cases. The identified lightweight structure is confirmed by topology optimization. The aim of the project is to produce 10 prototypes of the wheel using an RTM process and to test them under the certification tests provided..
Lightweight design methods are a high priority in aviation. The development of a lightweight aircraft wheel made of carbon fiber reinforced plastic (CFRP) helps to reduce the overall mass of the aircraft. These results in lower fuel consumption and the aircraft can be operated more economically, and the range or payload can be increased.
The “Development of a composite wheel” project is funded by the EU under the Clean Sky II Framework Program (H2020/2014-2020) (Grant Agreement for Members No. AIR-GAM-2016-2017-05). http://www.cleansky.eu/
- Jens-David Wacker, M.Eng.
- Phone: +49 6151 705-8356