Laser-Induced Projectile Impact Test Confirms Graphene's Strength
Graphene's great strength appears to be determined by how well it stretches before it breaks, according to Rice University scientists who tested its properties by firing microscopic projectiles at multilayer sheets of the material. The technique could help measure the strength of a wide range of materials. The Rice University lab of materials scientist Edwin Thomas proved that graphene is on average ten times better than steel at dissipating kinetic energy. The lab pioneered its laser-induced projectile impact test (LIPIT), which uses the energy from a laser to drive microbullets away from the opposite side of an absorbing gold surface at great speed. In 2012, they first used an earlier version of LIPIT to determine the properties of multiblock copolymers that could not only stop microbullets but also completely encase them. Since that study, Thomas and his team have enhanced their technique to fire single microscopic spheres with great precision at speeds approaching 3 kilometers per second, much faster than a speeding bullet from an AK-47. The experiments revealed graphene to be a stretchy membrane that, in about 3 nanoseconds before puncture, distributes the stress of the bullet over a wide area defined by a shallow cone centered at the point of impact.