A composite metal foam developed at NC State University is tough enough to resist the force of a bullet, disintegrating it into minute particles upon impact. The foam is lighter than steel metal plating, and will likely see large implementation into aerospace, automotive, and military applications
The foam largely comprised of steel has been in development for five years as conducted by professor of mechanical and aerospace engineering at NC State, Afsaneh Rabiei. The video above demonstrates the incredibly tough characteristics of the CMF as a 7.62 x 63 millimeter M2 armor piercing projectile was shot directly at the metal which inflicted virtually no damage to the plate.
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. He continues,
“To put that in context, the NIJ standard allows up to 44 millimeters indentation in the back of an armor.”
The results of the study conducted were published in 2015.
The CMF can be developed in various ways. Essentially, a gas must be introduced into the foam to create the bubbles within. This can be achieved by melting the material and directly injecting a gas into the molten material (see diagram below). Other methods include adding blowing agents which evaporate at a lower temperature, off-gassing in the liquid metal. Pressurized hydrogen can also be used. The end result is a low density, incredibly strong metallic structure.
[Image Source: NC State University]