Researchers at Chemnitz University of Technology and their partners from Fraunhofer IWU (Institut für Werkzeugmaschinen und Umformtechnik – Institute for Machine Tools and Forming Technology) have jointly developed a sandwich wheel rim made of a core of aluminium foam and outer layers of thermoplastic fibre-plastic composites. Compared to a conventional steel wheel of 15 inches and 6.8 kilograms, the new lightweight wheel weighs only 3.02 kilograms.
This is made possible by the sandwich design that takes advantage of the specific properties of the materials used. The wheel rim developed by researchers at the Cluster of Excellence “MERGE: Technologies for Multifunctional Lightweight Structures” consists of a stiff yet lightweight composite. A buffer layer reinforced with fibre glass is inserted between the aluminium foam core and the carbon fibre-reinforced outer layer. The buffer layer is designed to bridge the difference in stiffness between the aluminium foam and the carbon fibre-reinforced outer layers.
More comfort with less weight
The lightweight wheel combines strength with comfort: “Highly porous metal foams such as aluminium foam have excellent mechanical properties at a low density while at the same time they can potentially absorb a lot of energy. That is a contribution to driving comfort, especially when going round a turn in the road. Additionally, they have a distinct damage tolerance”, points out Alexander Hackert, research fellow at the Cluster of Excellence MERGE.
Reducing the unsprung masses has an additional advantage in that the wheel can be accelerated and decelerated more easily. The researchers see potential in the three-part rim and hope that car makers will make use of the wheel in future. “Our tests of the core compounds have shown the enormous potential of the wheel rim for an automotive application”, Hackert says. The design of the lightweight wheel has been registered as a utility model and as a patent specification at the German Patent and Trademark Office.