[Image above] Afsaneh Rabiei examines a sample of composite metal foam. Credit: North Carolina State University
Researchers from North Carolina State University definitely think so.
Professor of mechanical and aerospace engineering Afsaneh Rabiei has spent several years studying composite metal foams to better understand their properties and potential.
Composite metal foams consist of hollow spheres encased within a metallic matrix, so the materials contain lots of little air pockets. Rabiei’s work shows that this structure makes the metal foams “very effective at shielding X-rays, gamma rays and neutron radiation” and able to “handle fire and heat twice as well as the plain metals they are made of,” according to a NC State news story.
But the most visual demonstration of the awe of composite metal foams may come from this short video below.
Credit: NCState; YouTube
Not only does the foam completely and utterly destroy a bullet, but that test was done with an armor-piercing bullet. To be specific, it’s a 7.62 x 63 mm M2 armor piercing projectile fired per standard testing protocol by the National Institute of Justice. Read: the real deal.
When it comes to stopping bullets, ceramic materials are usually the gold standard for armor applications. But the visual proof above shows pretty clearly that other materials can be just as effective.
“We could stop the bullet at a total thickness of less than an inch, while the indentation on the back was less than 8 millimeters,” Rabiei says in the NC State story. “To put that in context, the NIJ standard allows up to 44 millimeters indentation in the back of an armor.”
Go ahead, watch the video again—it’s impressive.
The team published that ballistics research in Composite Structures last year. But, according to the paper, the researchers tested composite metal foams in addition to—rather than as a replacement for—ceramics. They developed an armor system with a boron carbide ceramic strike face with a composite metal foam energy absorber interlayer, all backed by a Kevlar or aluminum 7075 backplate.
Ballistics tests with those composite armor systems showed that the metal foams can absorb 60%–70% of the armor-piercing bullet’s total kinetic energy. That means that these air-filled metallic materials have the potential to offer significant weight savings and increased protection ability to existing ballistic armor systems.
And beyond armor, the foams also have potential applications that extend into space exploration, nuclear waste shielding, and much more.
So, what do you think—should ceramic materials be concerned?