Mar 21 2019
Aerodynamics in aircraft and cars is critical in order to save energy. However, technologies regulating saving of energy are only engineered for one-speed range. Scientists at Technische Universität Kaiserslautern have formulated a more versatile technique: Thanks to a so-called shape memory wire, the "intelligent material" can automatically adapt its shape to varying circumstances. It can also be customized to customer needs and combined into current components. The scientists promote their material via their start-up “CompActive.” They will showcase this material at the Hannover Messe from 1 to 5 April at the Rhineland-Palatinate research stand (Hall 2, Stand B40).
Hunting for prey, eagles circle slowly in the sky. Their fan-shaped spread feathers at their wing ends guarantee that they are traveling as efficiently as possible at moderately low speed. Thanks to their wings, however, the birds adjust to the new situations also during a rapid nosedive.
Aircraft are yet to become as flexible as birds of prey. There are commercial technologies that help to enhance efficiency. These include, for instance, so-called winglets, a sort of curved extension at the tips of the wings. “Turbulators are another example,” says Dr Moritz Hübler from the Institute for Composite Materials (IVW) at the Technische Universität Kaiserslautern (TUK). “These are a large number of small disturbing surfaces that stabilize the flow on the wing surface. This allows pilots to fly more slowly,” continues his research colleague Patricia Schweitzer. Both have one shared factor: they are only inflexible components that do not adjust automatically during flight. “Here, aerodynamics of the aircraft is only designed for certain speeds,” says Hübler.
The technology on which the researchers around Hübler and Schweitzer are working is correspondingly flexible as the eagle’s wing. It adjusts automatically to various speeds and temperatures. Wires created using a shape memory alloy consisting of a nickel-titanium compound are used.
This is how experts describe the phenomenon that these wires return to their old form after being deformed. When the wires are heated, for example by electric current, they contract.
Dr Moritz Hübler, Institute for Composite Materials (IVW), TUK.
The wires are added to a flexible plate composed of composite material. Akin to the human musculature, a contraction of the wires makes the material to bend.
“Our active material requires less volume and has a lower weight than conventional techniques such as compressed air or electric motors,” explains Schweitzer. They can modify their modules, or actuators, as the team refers to them, to individual customer needs. “We offer different sizes and they can be used on different materials, such as fibre-reinforced plastic or metal,” Schweitzer continues. The actuators can also be applied to the part in various ways and combined into electrical systems. “Bonded and screwed joints are possible as well as soldered connections or plugging onto a brass wire,” Schweitzer continues to explain. The material structure has already been patented by the team. In their start-up “CompActive”, Hübler and Schweitzer expand it to market maturity along with their three partners Daniel Vogelsanger, Nicolà Hammann, and Nils Neblung.
A number of new functions are imaginable with this “intelligent material”, such as gap- and bend-free aircraft flaps that automatically enhance aerodynamics for various speeds and thereby save energy. In flight tests, IVW scientists and partners have already been able to demonstrate that their material can also be employed in turbulators: they could be easily stretched at the touch of a button.
This allows slower, steeper and safer landing approaches without compromising efficiency.
Dr Moritz Hübler, Institute for Composite Materials (IVW), TUK.
So as to minimize fuel consumption, a related area of application is also likely for vehicles. Hübler quotes another example: “This technology could be automatically used to achieve optimum aerodynamics at any time by means of existing sensors, regardless of whether you are driving in the city or on the motorway.”
Another area of application is ventilation and heating systems, but the technology is also applicable for a cooling system for protective helmets in the sports domain or for advanced lamp designs.
At the Hannover Messe, the scientists will showcase a model of an aircraft wing in which six actuators are fitted that can be regulated independently. They also present a method wherein their material is contracted and thus stays in a bent state without consuming energy. “We use a simple latch with which we fix the system in this state; it resembles latches in a garden gate, for example,” says Schweitzer. They have also formulated another option for this technology, using a sort of click system that is akin to that of a ballpoint pen, which ensures that the refill stays outside.
The start-up project has been funded by the Federal Ministry of Economics and Technology (BMWi) as an “EXIST research transfer project” at the Institute for Composite Materials in the first funding phase until the beginning of 2020. In their research, the young entrepreneurs are aided by TUK and the Institute for Composite Materials. The team has already made contact with customers and is scheduling a first series production for the next year.