"The structure can be designed to absorb vibrations with oscillations of a few hundred to a few tens of thousand times per second. This includes vibrations in the audible range."Chiara Daraio, ETH Zurich

Vibrations from a bus engine can sometimes be felt uncomfortably strongly through the seats. Similarly, vibrations from the propellers or rotors in propeller aircraft and helicopters can make flights bumpy and loud, and also lead to increased levels of fatigue damage in the aircraft and its components. Engineers have therefore sought to prevent such vibrations in machines, vehicles and aircraft.

A new three-dimensional (3D) lattice structure developed by scientists at ETH Zurich in Switzerland could now help dampen these vibrations more than ever before. The lattice structure is described in a paper in the Proceedings of the National Academy of Sciences.

Led by Chiara Daraio, professor of mechanics and materials at ETH Zurich, the scientists made the structure, which has a lattice spacing of around 3.5mm, out of plastic using a 3D printer. Inside the lattice they embedded steel cubes that are somewhat smaller than dice and act as resonators.

"Instead of the vibrations traveling through the whole structure, they are trapped by the steel cubes and the inner plastic grid rods, so the other end of the structure does not move," explains Kathryn Matlack, a postdoc in Daraio's group.

Materials for absorbing vibrations already exist. In vehicles, machines and household appliances, vibrations are partly absorbed using special, mostly soft materials. The ETH researchers' vibration-absorbing structure is novel because it is rigid and thus can also be used as a load-bearing component, for instance in mechanical engineering or even in aeroplane rotors and helicopter propellers. The new structure offers another major advantage too: compared to existing soft materials, it can absorb a much wider range of vibrations, both fast and slow, and is particularly good at absorbing relatively slow vibrations.

"The structure can be designed to absorb vibrations with oscillations of a few hundred to a few tens of thousand times per second (Hertz)", says Daraio. "This includes vibrations in the audible range. In engineering practice, these are the most undesirable, as they cause environmental noise pollution and reduce the energy efficiency of machines and vehicles."

In theory, it would be possible to build a similar lattice structure out of aluminium and other lightweight metals instead of plastic, says Matlack. This would just require structuring a lightweight material in the lattice geometry and embedding it with resonators with a larger mass density. The geometry of the lattice structure and the resonators would then need to be optimally aligned for the anticipated vibrations.

These vibration absorbers are essentially ready for technical applications, says Matlack. But they are hampered by the fact that 3D printing technology is currently geared toward small-scale production and works with materials with properties such as load-bearing capacity that cannot yet match those of components manufactured with traditional methods. Once 3D printing is ready for industrial use, there is nothing standing in the way of a broader application.

Such broader applications could include in wind turbine rotors, where minimizing vibrations would increase efficiency. The technology could also conceivably be used in vehicle and aircraft construction as well as in rockets.

This story is adapted from material from ETH Zurich, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.