Graphene Could Build Better Bulletproof Vests

Chuck Bednar for – Your Universe Online
Writing in the latest edition of the journal Science, Rice University and the University of Massachusetts researchers demonstrate that bulletproof vests made from graphene could withstand the impact of a bullet better than those made from steel or Kevlar.
According to BBC News online science editor Paul Rincon, Jae-Hwang Lee of the University of Massachusetts Department of Mechanical and Industrial Engineering and his colleagues carried out small-scale ballistics tests by firing silica spheres at sheets of the thin, nearly transparent sheets of pure carbon. They found that graphene can be stronger than steel when absorbing impact.
The material, Rincon explains, consists of a sheet of single atoms that have been arranged in a honeycomb structure. It is thin, strong and flexible, and is also an extremely efficient conductor of heat and electricity. Lee’s team used lasers to observe the silica spheres as they penetrated sheets of the material that were 10 to 100 layers thick, and compared the kinetic energy of those so-called “microbullets” both before and after piercing the graphene.
“Observations using an electron microscope revealed that graphene dissipates energy by stretching into a cone shape and then cracking in various directions,” he said. The tests demonstrated that the material’s “extraordinary strength, elasticity and stiffness allowed it to absorb between eight and 10 times the impacts” of steel, but that the impact left a “wider impact hole” in the graphene, which Rincon calls “a potential disadvantage.”
Ever since graphene was first discovered in 2004, researchers have been performing extreme stunts to demonstrate its strength, Matthew Gunther of RSC’s Chemistry World explained. However, while there have been claims that the material “could withstand the force of an elephant balancing on a pencil,” this marks the first time it has been “subjected to the extreme conditions of high speed ballistics, the true strength test for armored materials.”
Lee explained to Gunther that they were unable to use conventional methods such as using a gun barrel or gunpowder on a test of this scale, so instead they used the laser to accelerate a microscale silica sphere at the multilayer graphene targets. That bullet was propelled into the stacked graphene sheets at of speeds of up to 2000 mph by the gases produced by laser pulses rapidly evaporating a gold film, he added, and the researchers calculated the energy difference of the bullet both before and after impact to determine how much energy was absorbed.
“The researchers found that the sheets were able to dissipate the energy of the bullet by stretching backwards – sort of like when someone jumps on a trampoline,” said Bob Yirka of PhysOrg. “The researchers found that the graphene was able to perform twice as well as Kevlar, the material currently used in bullet-proof vests, and up to ten times as well as steel.”
“The ability of graphene to dissipate energy, the team explains, is due to a high degree of stiffness combined with low density, which means that energy can move through it very quickly, allowing for the dissipation of energy from something traveling as fast as a bullet,” he added. “The researchers efforts show that graphene could very well mean a better bullet-proof vest, if a way could be found to produce it in enough quantity and at a low enough price.”

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