UNL engineer outlines 'nano-Velcro's' potential

Creating a so-called "super nanocomposite" that can revolutionize a range of products is the dream of materials scientists. So far, that's proved elusive. A University of Nebraska-Lincoln engineer shares that big dream but said he thinks using nanomaterials to strengthen small structures is more promising and cost-effective for the near-term.

Yuris Dzenis, professor of engineering mechanics, discusses the potential for structural nanocomposites and his UNL-patented continuous nanofiber material in the Jan. 25 issue of the journal Science.

Ten years ago, materials scientists predicted they could use carbon nanotubes to develop an advanced nanocomposite that is 10 times stronger than steel but a fraction of the weight. That hasn't happened yet, Dzenis said.

Advanced laminated composites reinforced with high-performance fibers, including carbon, ceramic and polymer fibers, represent some of the best structural materials available today, Dzenis said. They are used in thousands of everyday products, including airplane wings, automotive components and even bridge retrofits.

Dzenis said UNL researchers are developing continuous nanofibers, a new class of nanomaterial that offers several advantages over the advanced composite reinforcements currently commercially available, including carbon nanotubes.

His unique product uses continuous, entangled nanofibers, which he compares to the hooks and loops of Velcro, to toughen conventional laminated composites. Used as reinforcement between the layers that comprise laminated composites, the tiny nanofibers stick together to create a strong bond that doesn't easily chip, fracture or come apart.

"The technology is useful for almost any composite product or structure that requires mechanical integrity and durability," said Dzenis, the R. Vernon McBroom professor of engineering mechanics.

Dzenis said he believes his research is the first to investigate adding small amounts of nanomaterials to strengthen conventional advanced composites to create a blended hybrid product.

"We are using nanomaterials as a secondary reinforcement but one that is very important to the overall structural performance of the materials," he said.

Less is more when it comes to nano-reinforcement, Dzenis said. Adding only a tiny quantity of continuous nanofibers to a composite material greatly improves its strength and toughness. UNL research showed that these improvements don't significantly increase the product's weight or interfere with other composites' properties.

That could make continuous nanofibers a cost-effective option for manufacturing large structures because only a small amount of nanomaterial is required and it can be easily combined with other composite materials already used in manufacturing. Nanofibers could strengthen composites used for aerospace and military structures, including airplane frames, body and vehicle armor, sporting goods, marine structures and automobiles.

"It shows substantial improvements over what's being used currently," he said.

As the name suggests, the minute size of nanofibers is another advantage. They are 10 to 10,000 times smaller than conventional fibers and are more flexible. These characteristics make nanofibers ideal for bonding and strengthening fragile microstructures for which conventional reinforcement isn't practical, such as thin films, coatings, membranes and larger fibers. Dzenis said this type of nano-reinforcement could be used for dental prostheses and other medical applications.

UNL has patented Dzenis' continuous nanofiber composite and he continues to develop and refine it. The idea stemmed from his work on advanced aerospace composites and his collaborative research with Darrell Reneker from the University of Akron. Xiangfa Wu, a UNL research assistant professor, and several graduate students also are involved.

This work is part of Dzenis' broader research to create super nanocomposites. That's long-term research but he is developing new design strategies he hopes will yield immediate advances to keep researchers, developers and entrepreneurs excited about developing them.

"In my opinion, a super nanocomposite is still possible," he said. "It will just require unconventional thinking and approaches."