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Composite steel foam stops 50-caliber rounds as well as solid steel at half the weight

June 07, 2019
Source: ASM International

North Carolina State University, Raleigh, announces its researchers have demonstrated that a steel composite metal foam can stop armor-piercing 50-caliber rounds as well as conventional steel armor, even though it weighs less than half as much.


Composite metal foam (CMF) consists of hollow metallic spheres made of materials such as stainless steel or titanium that are embedded in a metallic matrix made of steel, titanium, aluminum, or another metallic alloy. This can be made by bubbling gas through molten metal to produce a frothy mixture, which can then be cooled to form a lightweight matrix and embedded with hollow metallic spheres. The result is a material much lighter than conventional metals but with comparable strength. In this study, the researchers fabricated a composite in which both the spheres and the matrix were made of steel.


For the study, researchers manufactured a hard armor system consisting of a ceramic faceplate, a CMF core, and a thin back plate made of aluminum. The armor was tested using 50-caliber ball and armor-piercing rounds. The rounds were fired at impact velocities from 500 up to 885 meters per second.


The CMF layer of the armor was able to absorb 72 to 75% of the kinetic energy of the ball rounds, and 68 to 78% of the kinetic energy of the armor-piercing rounds. "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," says Afsaneh Rabiei, a professor of mechanical and aerospace engineering at NC State.


Subject Classifications

Composite Materials | Metal-Matrix Composites

Industries and Applications | Aerospace and Defense

Industries and Applications | Automobiles and Ground Transportation

Materials Processing and Treatment | Casting

Metals and Alloys | Aluminum

Metals and Alloys | Carbon and Alloy Steels

Metals and Alloys | Stainless Steels

Metals and Alloys | Titanium

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