As if we needed a report to tell us that the current helmet design contributes to brain injuries. The current pattern is after all a compromise designed so that a Soldier can breath, smell, hear, and see. All pretty critical capabilities on a battlefield. Based on the cut, it isn’t any big surprise that blast waves enter the helmet. What is interesting is how one protective feature of modern helmets is protecting our troops, it is also putting them at risk to TBI.
The study entitled “Skull Flexure from Blast Waves: A Mechanism for Brain Injury with Implications for Helmet Design” discusses traumatic brain injury [TBI] and how it may be caused by skull flexure from even non-lethal blasts and without actual head impact.
Ultimately, what we are seeing is a similar phenomenon to what we have seen with body armor. Personal protection technology has developed to the point where they protect a Soldier from death in many attacks that would have killed them in previous conflicts. Consequently, we have seen a marked increase in burn, amputation, and brain injuries. These are effects that weren’t considered major requirements, if at all when the current family of PPE was under development.
In particular this report cites the air gap between the Soldier’s head and the inside of his helmet. Once again, with earlier technologies, the helmet shell’s material would not have been sufficient to protect the Soldier from most blasts and the accompanying shrapnel. Current and emerging shell technologies do a much better job at protecting from shrapnel injuries and so TBI is now being found in blast survivors. Unfortunately, the air gap in the helmet protects the wearer from blunt trauma injuries associated with back face deformation of the shell’s ballistic material. The ACH maintains a 1.3-cm gap between helmet and head; in simulations involving a 5-pound bomb exploding 15 feet from a Soldier’s head, blast waves washed into the helmet through this gap. “The helmet acts as a windscoop, so the pressure between the skull and helmet is larger than the blast wave by itself,” study co-author Michael King said. While the ACH’s pads mostly prevented this underwash, they also passed on forces to the skull.
King suggested that the pads’ stiffness could be optimized to “take the best of both worlds; it doesn’t allow the blast in there, and it doesn’t transfer [forces] from the helmet to the head.” He stressed that when making changes to the helmet, preserving its ability to reduce impacts and fend off bullets was paramount. “You’d have to be careful to make sure it doesn’t interfere with what the helmet does very well, which is stopping fragments and bullets,” he said. “The whole idea why there was a big gap between skull and helmet in the first place, is it makes it more likely for the soldier to survive if a bullet hits the helmet.”