Engineers at the University of Wisconsin-Madison have created a nanofiber material that is claimed to outperform steel plates and Kevlar at protecting against the impact of high-velocity projectiles.
Ramathasan Thevamaran, a UW-Madison assistant professor of engineering physics who led the research, said the nanofiber mats exhibit protective properties that far surpass other material systems at much lower weight.
Thevamaran and his collaborators detailed the advance in a paper published in ACS Nano†
To make the material, Thevamaran and postdoctoral researcher Jizhe Cai mixed multi-walled carbon nanotubes with Kevlar nanofibers. The resulting nanofiber mats are said to be superior at dissipating energy from the impact of small projectiles moving faster than the speed of sound.
The progress lays the groundwork for using carbon nanotubes in lightweight, high-performance armor materials such as body armor or in shields around spacecraft to mitigate damage from high-velocity flying micro-debris.
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“Nanofiber materials are very attractive for protective applications because nanoscale fibers have excellent strength, toughness and stiffness compared to macroscale fibers,” Thevamaran said in a statement. “Carbon nanotube mats have shown the best energy absorption to date and we wanted to see if we could further improve their performance.”
The team synthesized Kevlar nanofibers and incorporated a small amount of them into their carbon nanotube mats, which created hydrogen bonds between the fibers. Those hydrogen bonds changed the interactions between the nanofibers and, along with just the right mix of Kevlar nanofibers and carbon nanotubes, delivered a jump in the performance of the overall material.
“The hydrogen bond is a dynamic bond, meaning it can continuously break and re-form, allowing it to dissipate a large amount of energy through this dynamic process,” Thevamaran said. “In addition, hydrogen bonds give more rigidity to that interaction, which strengthens and stiffens the nanofiber mat. When we modified the interfacial interactions in our mats by adding Kevlar nanofibers, we were able to achieve nearly 100 percent improvement in energy dissipation performance at certain supersonic impact velocities.”
The researchers tested their new material using a laser-induced microprojectile impact testing system in Thevamaran’s lab. The system is one of the few in the United States and uses lasers to shoot micro-spheres into the material samples.
“Our system is designed in such a way that we can take a single bullet under a microscope and shoot it at the target in a very controlled manner, at a very controlled speed that can be varied from 100 meters per second to over 1 km per second. . second,” said Thevamaran. “This allowed us to run experiments on a time scale where we could observe the reaction of the material – as the interactions with hydrogen bonds take place.”
The new nanofiber material is also stable at very high and very low temperatures, making it useful for applications in a wide range of extreme environments.
The researchers patent their nanofiber material through the Wisconsin Alumni Research Foundation.