Getting More Fiber with Polymer-Coated Metal Core

Michael Dickey, Alcoa Professor of Chemical and Biomolecular Engineering at NC State, and his colleagues have developed fibers comprising a gallium metal core surrounded by an elastic polymer sheath. Under tension, the fiber displays the strength of the metal core. However, when the metal ultimately breaks under the strain, the fiber as a whole does not snap. The polymer sheath absorbs some of the strain between the breaks in the metal and transfers the stress back to the metal core. One might think of it as being akin to how human tissue holds together a broken bone despite the snap. "Every time the metal core breaks it dissipates energy, allowing the fiber to continue to absorb energy as it elongates," Dickey explains. "Instead of snapping in two when stretched, it can stretch up to seven times its original length before failure, while causing many additional breaks in the wire along the way. So, if such a fiber is being used to bear a heavy load it won't simply snap when the strain gets too much it will continue to support the weight, which might have engineering or other applications in sustaining a structure and delaying its failure considerably.