R&D Magazine (a nerd favorite of mine) has covered some development testing of graphene. Materials scientist Edwin “Ned” Thomas or Rice University has looked at the material as a future component to body armor. Its high strength and lightweight make it ideal for body armor (if it just wasn’t so expensive).
Using micro-bullets of about 3 micros (about 1/10th the size of a human hair), shot at over 1 km/s, the scientists were able to see the energy dissipation of graphene on a micro level. The key was to see how much it stretches before it breaks. The video has all the details of what reaction they were looking for and how it applies on a macro level.
As a microbullet impacts the graphene, the diameter of the cone it creates—determined by later examination of the petals—provides a way to measure how much energy the graphene absorbs before breaking.
“The game in protection is getting the stress to distribute over a large area,” Thomas said. “It’s a race. If the cone can move out at an appreciable velocity compared with the velocity of the projectile, the stress isn’t localized beneath the projectile.”
Controlled layering of graphene sheets could lead to lightweight, energy-absorbing materials. “Ideally you would have a lot of independent layers that aren’t too far apart or so close that they’re touching, because the loading goes from tensile to compressive,” Thomas said. That, he said, would defeat the purpose of spreading the strain away from the point of impact.