Vibration-absorbing, sound-damping materials such as sheets of rubber and expanded foam tend to be thick, bulky and soft. A new material is a big exception to that tendency, however, as it absorbs vibrations while staying stiff and thin.
Ordinarily, if you want to build a structure which is strong and unyielding yet also capable of absorbing troublesome vibrations, you have to combine load-bearing rigid materials with softer substances. Another option is to incorporate mechanical shock absorbers into the structure.
In either case, the finished product will be heavier, bulkier, and more expensive than it would have been if only rigid materials were used. That's where the new composite material comes in.
Developed by Ioanna Tsimouri, Andrei Gusev and Walter Caseri at the ETH Zurich research institute, it consists of ultra-thin stacked layers of stiff material connected by even thinner layers of an elastic polymer. More specifically, the initial prototypes consisted of 0.2- to 0.3-mm-thick glass plates interspersed with layers of PDMS (polydimethylsiloxane) silicone that were just a few hundred nanometers thick.
This ratio was important, as computer models indicated that in order to perform as desired, the composite needed to be at least 99% stiff material (by volume) and less than 1% polymer. "There is very little of a damping effect if the polymer layer is too thin," says Tsimouri, who led the study. "If it is too thick, the material is not stiff enough."
Samples of the material withstood standard three-point bending strength tests, while also exhibiting excellent damping qualities down to a temperature of -125 ºC (-193 ºF).
In a demonstration of the composite's properties – which can be seen in the video below – sheets of the material and of standard glass were dropped from a height of 25 cm (9.8 in) onto a tabletop. While the glass bounced into the air and made a loud clattering noise, the composite didn't bounce and made a subdued sound.
It is hoped that once the technology is developed further, different versions of the material could be utilized in applications such as windows, machine housings, automobile parts and even aerospace components. And as an added bonus, the current glass-based version of the composite can be completely recycled, since the small amounts of PDMS decompose into glass when melted.
A paper on the study was recently published in the journal Composites Part B: Engineering.
Source: ETH Zurich
