Programmable vibration damping material developed by Swiss Empa
Researchers from Empa (Material Science & Technology) and ETH Zurich (Federal Institute of Technology, Zurich) have succeeded in producing a prototype of a vibration damping material capable of changing the landscape of mechanics. The material not only damps vibrations completely, it is capable to further conduct certain frequencies
Clearly, the “programmable material”, at the moment, is still working in a one dimensional model construction. However, it has demonstrated unusual capabilities. The research project named “Phononic Crystal” with Adaptive Connectivity has just been published in the journal Advance Materials. The first step towards mechanical components with freely programmable properties has already been achieved.
The working model used by the researchers consists of a 1 m x 1 cm aluminium plate of one millimetre thickness. This sheet metal strip can vibrate at different frequencies. In order to control the wave propagation, ten small aluminium cylinders (7 mm thick, 1 cm high) are attached to the metal. Between the sheet and the cylinders sit piezo discs, which can be stimulated electronically and by changing their thickness in a flash. This ultimately enables the team headed by project supervisor Andrea Bergamini to control exactly whether and how waves are allowed to propagate the sheet metal strip. The aluminium strip thus turns in to a so called adaptive phonoic crystal – a material with adaptable properties.
The piezo controls can now be set in such a way that waves are able to propagate through the sheet metal strip “perfectly normally”, as though no aluminium cylinders wee attached to it. Another configuration enables a certain frequency spectrum of the waves to be absorbed. And this muffling is variable as the piezo elements can alter their elastic properties electronically in fractions of a second – from low to high stiffness. Bergamini explains what could be the further development: “imagine one produces a sheet of metal, imprinted with an electronic circuit and small piezo elements at regular intervals. This sheet metal could be programmed electronically to block a certain vibration frequency. The interesting thing is that even cutting off part of the sheet, the waves in the cropped section would largely spread in the same way as in the initial piece. This method could be used on 3D components.
Such a “meta-material” could fundamentally revolutionise mechanical engineering and plant construction. Until now, the vibration properties were already determined in the selection of material and the geometry of the part. In future, the material could react to current vibration readings and adapt its vibration properties at lightning speed.
During the Phonoic Crystal with Adaptive Connectivity research project, Empa researcher Bergamini collaborated with Paolo Ermanni’s group at ETH Zurich and Massimo Ruzzene from Georgia Institute of Technology. In a follow-up project, the programmability of the prototype will be enhanced. Until now, every piezo element has reacted to vibration alone, independent of its neighbour. As next step, it is planned to interconnect the elements with each other to be able to control them jointly or in a coordinated fashion.
Meta-materials are artificial media structured on a size scale smaller than the wavelength of external stimuli. Materials of interest exhibit properties not found in nature, such as negative index of refraction. They are cellular assemblies of multiple elements fashioned from materials, including metals and plastics, arranged in periodic patterns. Meta-materials gain their properties not from their geometry. Sizes, orientation and arrangement can affect light or sound in a manner that it is unachievable with conventional materials (Wikipedia).