Two football players collide on the field. Both are wearing helmets. Still, their heads bang together, risking serious injury. A new helmet design might offer these players’ brains much better protection. Key to its advantage: three layers of energy-absorbing insulation. Most helmets today offer just a single layer.
“Current helmets do a good job of reducing the force that gets to the skull,” says Ellen Arruda. She’s a mechanical engineer at the University of Michigan in Ann Arbor. But reducing force isn’t the only problem. A blow to the head sends waves of kinetic (Ki-NET-ik) energy through the skull and into the brain. Kinetic energy is the energy of motion.
“Let’s imagine you have an egg and you hit the egg,” explains Michael Thouless, also a mechanical engineer at Michigan. Hitting the egg could crack its shell. But the impulse of kinetic energy might also send the egg flying.
Something similar happens when an athlete’s head gets hit. Even if the skull doesn’t crack, an impulse of energy travels through the skull and brain. But the brain and skull don’t always move at the same speed. So parts of the brain can crash against the inside of the skull.
Bike helmets are made to crush, or deform, on impact. That action absorbs a good deal of the kinetic energy. Afterward, however, the helmet must be thrown out. That’s not practical for football and other contact sports. And helmets for those sports do a poor job of cutting down on that kinetic energy, says Arruda.