By Katie Lange
DoD News, Defense Media Activity
Imagine watching a test dummy fall to the ground over and over. After a time or two, you adjust some details of the properties of the rubber band-like harness you have attached to it. Then you let it fall again … over and over and over.
It sounds tedious, sure. But for the Army Research Laboratory crew doing it, they’re pretty pumped for the reasoning – a collaboration with the National Football League to minimize the chance of concussions in service members and athletes.
Through a grant from the NFL Head Health Challenge II, the ARL is working to perfect rate-dependent tethers that will go into the gear used by football players and service members to cut down on brain injuries they commonly suffer. The tethers will couple the head to the body, acting like a shock absorber when someone’s head violently whips backward.
Take quarterbacks and paratroopers, for example. A quarterback can go from standing upright to quickly being knocked backward off his feet by a defender, with his head usually smacking the ground last. With paratroopers, they’re taught to roll as they land, but if they’re inexperienced, it’s dark or the terrain is rough, their heads are often the last to hit ground, too. This tether system would cut the momentum of both of those head smacks and, therefore, cut down on the likelihood of a concussion.
For the ARL team involved in the project, it’s new technology based off old work, really. The idea they proposed to the NFL in November 2014 stemmed from a concept developed under a DARPA grant years before, when researchers created a speed-reliant elastic strapping material to help develop ankle and knee braces for soldiers. That project was scrapped, but it’s since gotten new life.
“We had that technology on the shelf, so when this call came out from the NFL … We thought, ‘What if we could use this as a way of supplementing the neck muscles and controlling head motion during violent events?’” said the project’s lead scientist, Dr. Eric Wetzel.
So they set to work to prove their idea was feasible. They built a test dummy, complete with sensors, cameras and equipment that would mimic a football player’s head hitting the ground at 100 G’s – a number based on typical acceleration levels, according to data collected from the NFL, collegiate and high school football studies, Wetzel said.
Then, they attached a harness they developed with the revamped elastic strapping material, which was made into rubber band-like tethers filled with a shear thickening fluid that can transform into a solid-like material. That happens because the fluids are colloids — suspensions of very small particles at high concentration in the liquid. “At low speeds and stress, the particles can flow past each other, and the overall system behaves like a viscous fluid; but at higher speeds and stress, they collide and behave more like packed sand,” Wetzel explained.
The team tested multiple scenarios, changing the harness’ variables about 250 times until they came up with an effective combo that brought the dummy’s acceleration level down to 50 G’s.
“[The combination] reduced peak accelerations by about 50 percent, which correlates with a pretty significant decrease in the likelihood of concussion,” Wetzel said.
His team, which consists of about 30 people, is still perfecting the liquid’s formula dgewood and the properties of all the components to determine how long their elasticity will last in a marketable product. From intern Michelle Torelli, who adjusts the liquid concoction, to Edgewood Chemical and Biological Center industrial designer Greg Thompson, whose focus is ergonomics and aesthetics, everyone’s role is crucial to the project’s success – including the computers models.
“Instead of having to go to the lab and make new liquid to have a different response, with a computer model, we can essentially make a few clicks and change the properties of that tether so, hopefully, we can get to the optimized solution quicker than we can through a whole series of experiments,” said research scientist Dr. Tom Plaisted.
A year of testing won the team a second NFL grant in December, which means they’ll hopefully be able to make the contraption a reality for NFL, youth and high school football players, as well as soldiers.
“It’s been exciting for us to learn about that field of injury – the physics, mechanics and biology of all that — and to have a solution that could actually be useful,” said Wetzel, whose team has traditionally worked on soldier protection projects dealing with ballistics and shrapnel.
He said projects like this are the reason why it’s important to invest in science and research.
“When I started working on these materials 15 years ago, I was not thinking about concussions. I wasn’t thinking about football or brain injury,” Wetzel said. “I was just trying to improve our understanding of these interesting materials. I wasn’t sure what they were applicable for.”
If you want to find out how the tethers are going to work in the field, check out our blog on DoDLive.
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