Nov. 27, 2007 -- Antiballistic materials can stop deadly bullets in their tracks, but the force of the impact can still cause severe bruising and even damage to internal organs.
But when woven into other materials, carbon nanotubes could work like Superman's chest, rebounding the force of bullets so that they bounce off.
"If the design and manufacture of bulletproof materials and structures can make full use of the carbon nanotubes' properties as we explored, the ballistic resistance of vests and shields can be much improved," said Liangchi Zhang, a professor at the Center for Advanced Materials Technology at the University of Sydney in Australia. Zhang and his colleague Kausala Mylvaganam reported their findings in the latest issue of the journal Nanotechnology.
Conventional soft-body pieces of armor, such as bulletproof jackets or explosion-proof blankets, are made from multiple layers of Kevlar, Twaron, or Dyneema fibers -- some of which are five times stronger than a piece of steel of the same weight. Long strands are interlaced into a dense net that absorbs the energy of the bullet and disperses it across the interlocking mesh.
But depending on the force of the bullet, injury can still occur. The best antiballistic material, the researchers say, can store energy elastically and deflect a bullet before that energy diffuses.
Carbon nanotubes could be that material. Zhang and Mylvaganam analyzed the molecule's force-repelling properties using a sheet of carbon, just one atom thick, rolled into a tube that looks something like a straw. They used a piece of diamond as a projectile to test the tube's strength.
Their studies showed that on impact, the carbon nanotube absorbed the energy of the diamond bullet, deforming as it did so. As the stored energy was released, the nanotube sprang back into shape, deflecting the bullet. The researchers found that the bigger the tube, the higher-speed bullet it could handle.
Zhang and Mylvaganam stressed that their results were theoretical and conducted under ideal conditions. For example, in the experiments the ends of the nanotubes were fully clamped down, which may not be possible in practice.
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