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Carbon nanotubes are the strongest and stiffest materials yet discovered, and show promise for everything from safer space-station modules to ballistic underwear and bullet resistant fiberglass panels thinner than a playing card.
AN INTRODUCTION TO CARBON NANOTUBES
A single carbon nanotube is a hollow fiber just a nanometer wide (i.e., about ten atoms thick) and millions of nanometers long. These can be readily grown in the lab. Single-walled carbon nanotubes have proven especially attractive to researchers, as they can conduct electricity, are composed of carbon (which is the fourth most abundant element in the Universe), and are up to one-hundred times stronger than steel at one-sixth the weight.
STOPPING BULLETS WITH CARBON NANOTUBES
L.C. Zhang (of the Centre for Advanced Materials Technology of the University of Sydney in Australia) has researched the ballistic applications of single-walled carbon nanotubes. Testing individual fibers, Zhang and his colleagues confirmed that these nanotubes can repel projectiles that are several times faster and more energetic than conventional bullets. As an added bonus, Zhang and his colleagues found that the carbon nanotubes retained their durability despite repeated impacts–in sharp contrast to existing bullet resistant fiberglass, which delaminates and splinters with each shot.
Although Zhang’s research is still very abstract (his team is shooting individual microscopic fibers with “bullets” made from tiny artificial diamonds moving faster than a speeding bullet), his calculations based on their findings indicate that a garment made from six layers of carbon nanotubes–totaling about 600 micrometers thick, thinner than a light t-shirt–would repel a shot from a .357 Magnum.
BRINGING CARBON NANOTUBES TO BULLET PROOF FIBERGLASS
Obviously, there’s more to stopping bullets than just preventing penetration: even if your t-shirt keeps the bullet from entering your body, the force of the impact is going to break ribs and could cause fatal soft tissue damage. But Zhang’s research–which included testing the maximum energy absorption of single-walled carbon nanotubes anchored at either end–lays a solid groundwork for advanced bullet resistant fiberglass panels. In contrast to DuPont™ Kevlar® fiber and other para-aramid synthetic fibers, which are strong but inelastic, carbon nanotubes are extremely tough and stretch. A mesh made of carbon nanotubes won’t just catch a bullet, but can also throw that projectile back, redirecting its energy instead of absorbing it.