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Every day, law enforcement, security officers, and military personnel (along with politicians and movie stars) depend on bulletproof vests for their very lives. The materials used can vary from bulletproof metal plates to man-made Kevlar fabric, to composites, which combine two different types of material together to produce one with superior characteristics.
All of these types of protection rely on the principle of absorbing the bullet’s enormous energy, though they approach this in different ways. And of course, they must do this with the minimal amount of bulk and weight – or they’ll be too uncomfortable to wear.
Current Bulletproof Vest Technologies
Ever since chemist Stephanie Kwolek invented the stronger-than-steel material Kevlar for DuPont de Nemours, other companies have competed to discover even stronger and lighter materials for bulletproof vests. Some of the newer materials for this purpose include Dyneema, Zylon, and Spectra.
Meanwhile, researchers across the globe continue searching for armor materials that are even lighter and stronger – as well as easier and cheaper to make. Some of the proposed materials include ceramic composites with titanium or carbon fibers, and graphene nanowires.
One of the more fascinating new materials that could prove to be the strongest yet is a composite metal foam invented by a team of researchers at North Carolina State University led by Afsaneh Rabiei. This material is much lighter than metal plating, yet can shatter an armor-piercing bullet on contact.
Material Just Like Styrofoam
The new material is a composite made by melting aluminum around hollow steel spheres, which creates air bubbles surrounded by a metal matrix. The result is a metallic “foam.” On impact, the metal spheres squeeze down and the pores collapse – just like squeezing a sheet of bubble wrap or stepping on a piece of Styrofoam.
“What we did is introduce the same concept to metals, and now we have the impact protection, because of the porosity inside,” said Professor Rabiei in a video interview. “But this time you have it against much heavier impact.”
Rabiei’s initial testing showed that the metallic foam could go to 80 percent compression without damage, because the energy is absorbed as the outside force compresses the material.
Later, when a 7.62 x 63 mm M2 armor-piercing round was fired into a sample of metal foam, following standard testing procedures established by the National Institute of Justice (NIJ), the bullet shattered on impact. The round caused an 8 mm indentation on the back – an 80 percent improvement over the 44 mm indentation allowed by the NIJ standard.
But not only is the metallic foam strong, it’s only about 1/3 to 1/2 the weight of sheet metal, due to the air bubbles inside. In fact, the foam is so strong and light, it can stop a bullet even at a total thickness of less than an inch, making an entire bulletproof metal suit not out of the realm of possibility.
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