Nanotechnology used in new anti-ballistic materials

We have written about defensive envelopes for military vehicles — developed by Israeli researchers and now being tested in Iraq — which use what can only be described as the “force” to defend the vehicles and their occupants against rockets and other projectiles. Rather than rely on heavy armor, the new defensive systems use the electromagnetic field to deflect and repel the projectile and prevent it from hitting the vehicle. Now, the new carbon nanotechnology-based materials being used in the latest personal protective equipment (PPE) do not do repel bullets, but they offer first responders, police officers, and soldiers who wear them protection by making bullets bounce off them without a trace of damage. A research paper published in the Institute of Physics’ Nanotechnology details how engineers from the Center for Advanced Materials Technology at the University of Sydney have found a way to use the elasticity of carbon nanotubes to not only stop bullets penetrating material but actually rebound their force. Most antiballistic materials — think bullet-proof jackets and explosion-proof blankets — are currently made of multiple layers of Kevlar, Twaron, or Dyneema fibers which stop bullets from penetrating by spreading the bullet’s force. Targets can still be left suffering blunt force trauma — perhaps severe bruising or, worse, damage to critical organs. The elasticity of carbon nanotubes means that blunt force trauma may be avoided and this is why the Aussie engineers have undertaken experiments to find the optimum point of elasticity for the most effective bullet-bouncing gear.

Professor Liangchi Zhang and Dr. Kausala Mylvaganam from the Sydney center said, “By investigating the force-repelling properties of carbon nanotubes and concluding on an optimum design, we may produce far more effective bulletproof materials. The dynamic properties of the materials we have found means that a bullet can be repelled with minimum or no damage to the wearer of a bullet proof vest.” Working at the scale of a nanometer (one billionth of a meter), condensed matter physicists engineer structures which manipulate individual atomic and molecular interactions. Working at this microscopic scale allows engineers to design fundamentally different and useful materials. One of these materials is nanotubes, a one-atom thick sheet of graphite, rolled into a cylinder which is held together by a very strong chemical bond called orbital hybridisation. Nanotubes bind together into a strong “rope” because of the van der Waals force* they share. Van der Waals is the weak attraction that molecules have for one another when they are brought close together, used, for example, by geckos when they stick to a ceiling.

* van der Waals force, named after Dutch physicist J. D. van der Waals, is used in chemistry and physics as a synonym for the totality of non-covalent forces (also known as intermolecular forces). These forces, which act between stable molecules, are weak compared to those appearing in chemical bonding. The use of the term van der Waals force for the total non-covalent force is historically correct, because van der Waals himself considered both the repulsive and the attractive component of the intermolecular force. Note, though, that there is no strict convention regarding the definition of van der Waals force (you may have run into this confusion in school): Some texts consider only the attractive component of the intermolecular potential as the van der Waals force, while other texts designate only a certain part of the attraction as the van der Waals force.

-read more in Kausala Mylvaganam and L. C. Zhang, “Ballistic Resistance Capacity of Carbon Nanotubes,” Nanotechnology 18 (17 October 2007) (doi:10.1088/0957-4484/18/47/475701) (sub. req.)