Provided by Science.
An image of an American football helmet being crushed at the moment of impact was featured on the cover of this week’s international academic journal ‘Science’. This is a pneumatic impact test scene from Biocore, a private research institute in charge of safety evaluation for the American National Football League (NFL). The moment when helmet manufacturer Riedel’s latest helmet model ‘Axiom’ collided head-on with a striker flying at a speed of 9.3 meters per second was captured.
Science reported on the 5th (local time) that data-based helmet safety testing has brought innovation to American football helmet design over the past 14 years.
The key to modern helmets is ‘controlled deformation’, which distorts upon impact. If the helmet is not deformed, the impact is transmitted to the brain within 3 milliseconds (ms, 1/1000th of a second), but if the helmet is distorted and acts as a buffer, the same shock is transmitted slowly over 15 ms. If the impact time is increased by five times, the instantaneous acceleration is reduced by one-fifth. This is the same reason why falling on a soft mat hurts less than on a hard floor.
Helmets that previously consisted of only a hard polycarbonate shell and foam padding now have a flexible nylon elastomer shell and 3D printed lining. In 2014, Riedel launched the ‘SpeedFlex’, a product with hexagonal incisions on the helmet shell, and developed it into Axiom in 2022 with incisions on all sides.
For this purpose, the helmet material and structure were changed. Helmets that previously consisted of only a hard polycarbonate shell and foam padding now have a flexible nylon elastomer shell that bends in the event of a collision. In 2014, Riedel launched the ‘Speed Flex’, a product made with hexagonal incisions on the outer shell to make it easier to crush, and in 2022, it developed it into ‘Axiom’ with incisions on all sides.
Lining technology has also undergone innovation. Colide, a lining manufacturer that won the 2019 NFL Helmet Technology Contest, developed a 3D printed lining consisting of 18 cylindrical pads. Inside each pad is a thin cone structure. When pressure is applied, the cone folds in stages starting from the tip, increasing resistance. While regular sponges are only compressed to 50%, 3D printing pads are compressed to 80-90%, increasing impact time and absorbing energy.
Concussion rates in the NFL have decreased by 35% since their peak in 2017. A study published by Biocore in 2020 found that players wearing helmets with good test scores had a lower incidence of concussions during actual games.
“Helmets cushion impacts much better than they did 5 to 10 years ago,” said Anne Bailey, a mechanical engineer at Good Biocore. “Acceleration values have decreased by about 30% since 2015.”
doi/10.1126/science.zs6zhs0
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