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A new synthetic rubber made by MIT and Army scientists stiffens under impact, and could be used in combat helmets of the future, they report in a new paper.

The polyurethane urea (PUU) material showed hyperelastic behavior, deforming to half its thickness in a less than a millionth of a second, and bouncing back after the impact, they report in the Elsevier journal Polymer.

“This is very exciting,” said Alex Hsieh, of the Army Research Laboratory. “Seeing is believing.”

The scientists at the Army Research Laboratory, and the Army Institute for Soldier Nanotechnology at MIT, report that they tested the material with micro projectile silica spheres, and measured by an all-optical laser-inducted projectile impact test, or LIPIT.

Other synthetic materials allowed the micro projectiles to pass through – and the materials did not recover from the changes wrought by the stress.

However, the PUU withstood the trauma, bouncing back even at relatively high strain rates. The material could be optimized, as well. By varying the molecular composition of the material, the depth of the penetration was reduced by another 50 percent, they added.

The PUU material, they hypothesize, is “chainmail-like” in that the molecules oscillate in different frequencies, which dissipates the energy absorbed in less than a blink of an eye.

“The essence of hyperelastic (phenomena) in bulk elastomers particularly at the moment of target (and) impulse interaction strongly points out to be a plausible pathway key to manipulating failure physics and toward a new design paradigm for robust materials,” Hsieh added. 

Other applications of the material could be in other armor or protective wear, including face shields, ballistic vests, and combat boots. Even football helmets could protect professionals and young players alike from the impacts connected to concussions, they added.

The blast effects on soldiers in modern American wars has some scientists hypothesizing that PTSD and mental wear may be the product of overlooked “blast shock” damage caused by pressure on the brain. Late last year it was reported that a U.S. military program to gauge the “blast shock gauges” on personnel in Afghanistan would be discontinued.

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