Twisted nanofibers create structures tougher than Kevlar

27-Mar-15

New structures that exploit the electromechanical properties of specific nanofibers to stretch to up to 7 times their length, while remaining tougher than Kevlar have been created by Researchers at the University of Texas at Dallas. These structures absorb up to 98 joules per gram, vs Kevlar, that absorb up to 80 joules per gram. The material can reinforce itself at points of high stress and could potentially be used in military airplanes or other defense applications. In a study published by ACS Applied Materials and Interfaces, researchers twisted nanofiber into yarns and coils. The electricity generated by stretching the twisted nanofiber formed an attraction 10 times stronger than a hydrogen bond, which is considered one of the strongest forces formed between molecules. Researchers sought to mimic their earlier work on the piezoelectric action (how pressure forms electric charges) of collagen fibers found inside bone in hopes of creating high-performance materials that can reinforce itself, said Dr. Majid Minary, an assistant professor of mechanical engineering in UT Dallas' Erik Jonsson School of Engineering and Computer Science and senior author of the study. "We reproduced this process in nanofibers by manipulating the creation of electric charges to result in a lightweight, flexible, yet strong material," said Minary, who is also a member of the Alan G. MacDiarmid NanoTech Institute. "Our country needs such materials on a large scale for industrial and defense applications." The team took inspiration from the piezoelectric action—where pressure is converted into electrical charges—observed in collagen fibers within human bone. The researchers recreated the collagan fibers by spinning polyvinylidene fluoride (PVDF) and polyvinvylidene fluoride trifluoroethylene (PVDF-TrFE)—themselves piezoelectric materials—into nanofibers. They then twisted these strands into yarns. When stretched, these polymer-based yarns create an electrical charge which acts to attracts the polymer strands back in on themselves—an attraction found to be 10 times stronger than a hydrogen bond