Researchers devised a new miniature ballistics test to test graphene’s bullet resistance. They used a laser pulse to superheat gold filaments until they vaporised, acting like gunpowder to fire a micron-size glass bullet into 10 to 100 sheets of graphene at 3000 meters per second.
The team found that graphene sheets dissipate this kinetic energy by stretching into a cone shape at the bullet’s impact point, and then by cracking outward radially. The cracks are one weakness of single-layer graphene, Lee says, but it nevertheless performs twice as well as Kevlar and withstands 10 times the kinetic energy that steel can. Using multiple layers of graphene or incorporating it into a composite structure could keep the cracks from spreading, too.
Multilayer graphene is an exceptional anisotropic material due to its layered structure composed of two-dimensional carbon lattices. Although the intrinsic mechanical properties of graphene have been investigated at quasi-static conditions, its behavior under extreme dynamic conditions has not yet been studied. We report the high–strain-rate behavior of multilayer graphene over a range of thicknesses from 10 to 100 nanometers by using miniaturized ballistic tests. Tensile stretching of the membrane into a cone shape is followed by initiation of radial cracks that approximately follow crystallographic directions and extend outward well beyond the impact area. The specific penetration energy for multilayer graphene is ~10 times more than literature values for macroscopic steel sheets at 600 meters per second.
SOURCES – New Scientist, Journal Science
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