Materials

Lightweight metal foam turns armor-piercing bullets into dust

The researchers imagine the metal foams will provide more than just ultralight, bullet-destroying body armor
The researchers imagine the metal foams will provide more than just ultralight, bullet-destroying body armor
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Afsaneh Rabiei with one of her composite metal foams
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Afsaneh Rabiei with one of her composite metal foams
The researchers imagine the metal foams will provide more than just ultralight, bullet-destroying body armor
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The researchers imagine the metal foams will provide more than just ultralight, bullet-destroying body armor
Afsaneh Rabiei with one of her composite metal foams
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Afsaneh Rabiei with one of her composite metal foams
The researchers imagine the metal foams will provide more than just ultralight, bullet-destroying body armor
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The researchers imagine the metal foams will provide more than just ultralight, bullet-destroying body armor

Composite metal foams (CMFs) are little-known materials that are beginning to show some big promise. Last year we saw researchers adapt these lightweight materials to stop various forms of radiation in their tracks, and now the same team has ramped things up to offer protection from something with a bit more force: an armour-piercing bullet, which was turned to dust on impact.

In its most simple form, foam metal is made by bubbling gas through molten metal to form a frothy mixture which then sets as a lightweight matrix. This leaves a material that offers a lighter alternative to conventional metals, while still maintaining a comparable strength.

Afsaneh Rabiei, a professor of mechanical and aerospace engineering at North Carolina State University, last year produced a foam metal shield that could block X-rays, various forms of gamma rays and neutron radiation, giving it potential as a lightweight alternative to the bulky radiation shielding currently available.

Afsaneh Rabiei with one of her composite metal foams
Afsaneh Rabiei with one of her composite metal foams

Building on this previous work, Rabiei then set about building high-strength armor. The shield was comprised of boron carbide ceramics as the strike face, with composite metal foam (CMF) as the bullet kinetic energy absorber layer and Kevlar panels as backplates. To test its durability, Rabiei and her team took aim with a 7.62 x 63 mm M2 armor-piercing projectile, which was fired in line with the standard testing procedures established by the National Institute of Justice (NIJ).

"We could stop the bullet at a total thickness of less than an inch, while the indentation on the back was less than 8 mm," Rabiei says. "To put that in context, the NIJ standard allows up to 44 mm (1.73 in) indentation in the back of an armor."

But Rabiei imagines her work will provide more than just ultralight, bullet-destroying body armor. Other potential applications include space exploration and transportation of nuclear waste due to its aforementioned abilities to block radiation.

You can check out the bullet's demise in the video below, while the research was published last year in the journal Composite Structures.

Source: North Carolina State University

NC State: Metal Foam Obliterates Bullets

28 comments
Mel Tisdale
I imagine its mechanical strength to weight ratio is also impressive.
notarichman
Neat, but please keep them away from criminals and enemies! now comes the question whether or not this type of discovery should be published?
Steve Smith
This almost seems like an April fools joke. This is remarkable if true so why isn't it getting wide coverage. It's like a miracle metal.
Colt12
This is a game changer, as was mentioned the possible resistance to space debris. This should open doors to all types of improvements.
RESISTANCE
This is not new research at all. Work was done at the Center For Composite Materials at the University of Delaware back between 1993 and 1996 using metal foams from Fraunhoffer. There was also some collaboration with ARL at Aberdeen. (Army Rearch Lab)
HensleyBeuronGarlington
Notarichman, you can't keep things out of the hands of criminals intent enough on owning such things. Prohibitions do not work and usually ensure that the law abiding public doesn't have access to such life saving products as body armor. Best thing to do is release it and let the market level it out. They will make projectiles that defeat this armor and they will make even better versions of this, but to restrict it is impossible and will not protect those you wish to protect. The same as restricting weaponry is foolish, its arguably more insane to restrict body armor.
MBadgero
Foamed metal has been around for at least several decades. Strength-to-weight has always been impressive. Not April fools, just hard to mass produce. The problem has always been to get the bubbles dispersed evenly when the foam cools and hardens. Looks like this has similar issues. The radiation protection is the same as any mass. The bullet-proof version of this uses suspended tungsten. Tungsten has also been proposed for use in copper composites for space suits to protect against micrometiorites ('The Millennial Project", Marshall Savage, 1992)
David A Galler
I wonder how it well it it will resist deterioration >
Racqia Dvorak
I'm guessing the ceramic coating has something to do with the "turned to dust" effect. The metal foam is absorbing the energy, to the tune of 70%, probably with internal deformation along all those bubbles. " A high-performance light-weight composite armor system has been manufactured using boron carbide ceramics as the strike face, composite metal foam processed by powder metallurgy technique as a bullet kinetic energy absorber interlayer, and aluminum 7075 or Kevlar™ panels as backplates with a total armor thickness less than 25 mm" "The results showed that composite metal foams absorbed approximately 60–70% of the total kinetic energy of the projectile effectively "
Stephen N Russell
Wonder how fast they'll get a DoD contract alone for this & add to tanks, trucks, The Beast for the White House etc alone. Huge implications for armoring vehicles, & homes