Polymer-Coated Metal Core Boosts Fiber Content

Michael Dickey, professor of chemical and biomolecular engineering at NC State, and his colleagues have produced fibers containing a gallium metal core surrounded by an elastic polymer coating. Under tension, the fiber exposes the resistance of the metal core. However, when the metal eventually fractures under tension, the fiber does not break completely. The polymer coating absorbs some of the tension between the fractures in the metal and transfers the pressure back to the metal core. This situation can be compared to how human tissue keeps a broken bone together despite the fracture. Dickey explains this situation as follows: "Each time the metal core breaks, it dissipates energy and allows the fiber to continue absorbing energy as it extends." Rather than breaking in two when stretched, it can stretch up to seven times its original length while causing multiple additional fractures along the entire cable length before breaking. Therefore, if such a fiber is used to carry a heavy load, when the tension becomes too great, it will not simply break but will continue to support the weight. This could have engineering and other applications in maintaining a structure and significantly delaying its failure.