Integrating stiff carbon nanotubes into more traditional materials, such as polycarbonate, can dramatically improve the material's ability to absorb vibrations, especially at high temperatures, according to US researchers. The discovery could lead to new composites for aerospace and automobile engineering applications as well as improving golf clubs and other sports equipment.

Materials being investigated as novel vibration dampening systems are commonly based on viscoelastic polymers, but Nikhil Koratkar of the Rensselaer Polytechnic Institute reckons the weight and volume penalties are too severe for many applications as well as not coping when the heat is on. "Traditional damping polymers perform poorly at elevated temperatures," he says. "Our new materials provide excellent damping at high temperatures, suggesting that these nanocomposites have great potential for a variety of applications in aircraft, spacecraft, satellites, automobiles, and even sensors for missile systems - basically any structure that is exposed to vibration."

Koratkar and his colleagues pursued the idea that the combination of an extremely large interfacial contact area and a high aspect ratio, coupled with a low mass density, would allow nanotube fibers within a polymer or epoxy matrix to readily dissipate energy but with little weight penalty. They have found that a nanotube-polycarbonate composite does indeed show such slippage and can be activated at relatively low dynamic strain levels by raising the temperature to about 90° Celsius.

The new materials could be extremely useful for any kind of space application, because temperatures swing wildly from very hot in the day to very cold at night, Koratkar notes. And he expects to use them in the diaphragms of loud speakers to help improve sound quality by reducing the buzz associated with high bass levels.

The sporting goods market is also an especially promising outlet, particularly for golf clubs and tennis racquets. "Manufacturers want tennis racquets and golf club shafts to be light and stiff, but without the annoying sting that comes from a bad shot," Koratkar says.

Nano Letters, 2006, 6, 219-223; http://dx.doi.org/10.1021/nl0521524

http://www.rpi.edu/~koratn/