#aramids

[materialsscienceandengineering]

Next-generation aramid fiber with electrical conductivity

Aramid fiber is known as "super fiber," or "golden silk," because even though its weight is equivalent to only 20% of the weight of steel, it is more than five times as strong and does not burn, even at 500°C. Aramid fiber is an essential material used in various applications such as body armor, fire-resistant clothing, fiber optic cable reinforcement, high-performance tires, and aerospace materials. The late Dr. Han-Sik Yun began researching aramid fiber at the Korea Institute of Science and Technology (KIST) in 1979 and secured independent source technology in 1984.

Dr. Dae-Yoon Kim and his research team at the Functional Composite Materials Research Center within the KIST Jeonbuk Institute of Advanced Composite Materials announced that they have applied carbon nanotubes to aramid fibers to develop a new kind of composite fiber. The findings are published in the journal Advanced Fiber Materials.

In addition to being lightweight, strong, and fire-resistant, the fiber also has electrical conductivity, which is a first for conventional aramid fibers. The newly developed fiber is black in color due to the presence of carbon nanotubes.

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[materialsscienceandengineering]

Stab-resistant fabric gains strength from carbon nanotubes, polyacrylate

Fabrics that resist knife cuts can help prevent injuries and save lives. But a sharp enough knife or a very forceful jab can get through some of these materials. Now, researchers report in ACS Applied Nano Materials that carbon nanotubes and polyacrylate strengthen conventional aramid to produce lightweight, soft fabrics that provide better protection. Applications include anti-stabbing clothing, helmets and insoles, as well as cut-resistant packaging.

Soft body armor is typically made from aramid, ultra-high-molecular-weight polyethylene, or carbon and glass fabrics. Their puncture resistance depends, in part, on the friction between yarn fibers within these materials. Up to a point, greater friction means greater protection. Manufacturers can boost friction by roughening the fiber surfaces, but that requires a complicated process, and product yield is low.

Alternatively, the bonding force between yarns can be enhanced by adding another component, such as a sheer thickening fluid (STF) or a polyurethane (PU) coating. But these composite fabrics can't simultaneously satisfy the requirements for thinness, flexibility and light weight. Ting-Ting Li, Xing-xiang Zhang and colleagues wanted to find another way to improve performance while satisfying these criteria.

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[materialsscienceandengineering]

New material, modeling methods promise advances in energy storage

Work offers promise for lightweight materials for energy technologies

The explosion of mobile electronic devices, electric vehicles, drones and other technologies have driven demand for new lightweight materials that can provide the power to operate them. Researchers from the University of Houston and Texas A&M University have reported a structural supercapacitor electrode made from reduced graphene oxide and aramid nanofiber that is stronger and more versatile than conventional carbon-based electrodes.

The UH research team also demonstrated that modeling based on the material nanoarchitecture can provide a more accurate understanding of ion diffusion and related properties in the composite electrodes than the traditional modeling method, which is known as the porous media model.

"We are proposing that these models based on the nanoarchitecture of the material are more comprehensive, detailed, informative and accurate compared to the porous media model," said Haleh Ardebili, Bill D. Cook Associate Professor of Mechanical Engineering at UH and corresponding author for a paper describing the work, published in ACS Nano.

More accurate modeling methods will help researchers find new and more effective nanoarchitectured materials that can provide longer battery life and higher energy at a lighter weight, she said.

The researchers knew the material tested -- reduced graphene oxide and aramid nanofiber, or rGO/ANF -- was a good candidate because of its strong electrochemical and mechanical properties. Supercapacitor electrodes are usually made of porous carbon-based materials, which provide efficient electrode performance, Ardebili said.

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[materialsscienceandengineering]

Kevlar-based artificial cartilage mimics the magic of the real thing

The unparalleled liquid strength of cartilage, which is about 80 percent water, withstands some of the toughest forces on our bodies.

Synthetic materials couldn't match it -- until "Kevlartilage" was developed by researchers at the University of Michigan and Jiangnan University.

"We know that we consist mostly of water -- all life does -- and yet our bodies have a lot of structural stability," said Nicholas Kotov, the Joseph B. and Florence V. Cejka Professor of Engineering at U-M, who led the study. "Understanding cartilage is understanding how life .forms can combine properties that are sometimes unthinkable together."

Many people with joint injuries would benefit from a good replacement for cartilage, such as the 850,000 patients in the U.S. who undergo surgeries removing or replacing cartilage in the knee.

While other varieties of synthetic cartilage are already undergoing clinical trials, these materials fall into two camps that choose between cartilage attributes, unable to achieve that unlikely combination of strength and water content.

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