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Engineers create structures tougher than bulletproof vests

27 March 2015

Researchers at UT Dallas have created new structures that exploit the electromechanical properties of specific nanofibres to stretch to up to seven times their length.

Dr Majid Minary

These structures absorb up to 98 joules per gram; Kevlar, often used to make bulletproof vests, can absorb up to 80 joules per gram. Researchers hope the structures will one day form material that can reinforce itself at points of high stress and could potentially be used in military aircraft or other defence applications.

In a study published in the journal, Applied Materials and Interfaces, the researchers describe how they twisted the nanofibre into yarns and coils. The electricity generated by stretching the twisted nanofibre formed an attraction ten 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 of collagen fibres found inside bone, in the hope of creating high-performance materials that were able to reinforce themselves.

“We reproduced this process in nanofibres by manipulating the creation of electric charges to result in a lightweight, flexible, yet strong material,” says Dr Majid Minary, the senior author of the study.

For their experiment, the researchers first spun nanofibres from polyvinylidene fluoride (PVDF) and its co-polymer, polyvinvylidene fluoride trifluoroethylene (PVDF-TrFE). They then twisted the fibres into yarns, and continued to twist the material into coils, much like the basic process used in making conventional cable.

“Our experiment is proof of the concept that our structures can absorb more energy before failure than the materials conventionally used in bulletproof armours,” says Dr Minary. “We believe, modelled after the human bone, that this flexibility and strength comes from the electricity that occurs when these nanofibres are twisted.”

The next step in the research is to make larger structures out of the yarns and coils.

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