Helmets are designed with one purpose, that is to prevent blunt force trauma to the head. But, what about the brain?
There is no doubt that ski helmets can and do prevent death. Take the recent accident of Formula One superstar, Michael Schumacher, who fell headfirst while skiing off-piste in the French Alps on December 29, 2013. Had he not been wearing a helmet when his head struck a rock, the result would be far more grave.
Another tragic example is that all Sally Franklyn, an avid skier and writer, who tumbled 800 feet two years ago. Fortunately, Sally was also wearing a helmet which likely saved her life. However both Sally and Michael will have a lifelong scars of traumatic brain injury.
Dr. John Lloyd, a biomechanists from Tampa has dedicated his career to the study of traumatic brain injury, John recently conducted a study on the protective properties ski helmets. While results show that wearing a ski helmet will dramatically improve protection against potentially fatal injury, findings also show that ski helmets may not provide sufficient protection against traumatic brain injury. The mechanism that causes skull fracture is quite different from that which causes the traumatic brain injury.
We have a great physicist, Professor Holbourn from Cambridge University in England, to thank for his 1943 paper on the mechanisms of head injuries. Dr. Holbourn showed, using a bowl full of Jell-O, that forces associated with linear acceleration all likely to give rise to focal head injuries, such as skull fractures. Whereas rotational forces are those more likely to give rise to brain injuries including concussion and brain bleeding. This is because rotating a bowl of Jell-O, the Jell-O moves greatest toward the center of the bowl
As to whether or not a better helmet can be designed to protect both the skull from fracture and the brain from traumatic injury, Dr. Lloyd says absolutely. In fact, within the scope of his research into helmet protection, Dr. Lloyd’s findings show that football helmets provide far greater protection of the head and brain from traumatic injury then do ski helmets.
Upon impact linear and rotational forces act on the head. Rotational forces being tangential to the linear forces. If a tangential force acts on a material such as EPS foam we would expect little, if any, deformation of the material since such materials, as shock absorbing materials, are designed to mitigate linear forces acting directly on them.