Composite Metal Foam Stops Bullets and Shields Against Radiation
Bilal Khan posted on March 30, 2017 |
Researchers believe CMFs can significantly improve material strength in many applications without ad...
Researchers at North Carolina State University have developed a range of composite metal foams that are lighter and stronger than the materials they are made of. The foams can be used in applications from armor to hazardous material transport -- and the researchers are now looking for collaborators to help identify and develop new applications. (Image courtesy of Afsaneh Rabiei.)
Researchers at North Carolina State University have developed a range of composite metal foams that are lighter and stronger than the materials they are made of. The foams can be used in applications from armor to hazardous material transport -- and the researchers are now looking for collaborators to help identify and develop new applications. (Image courtesy of Afsaneh Rabiei.)
Composite metal foams (CMFs) could drastically improve the strength of armor as well as increase shielding from radiation, heat and high-speed kinetic impacts.

CMFs, like other foam metals, are made by injecting gas bubbles into molten metal, which then forms a mixture that sets into a matrix. The resulting material retains the strength of the original metal, but is substantially lighter. In comparison to other metal foams, CMFs have five to six times greater strength-to-density ratio and over seven times higher energy absorption, according to Afsaneh Rabiei, professor in the department of mechanical and aerospace engineering at North Carolina State University.

To test CMF strength, Rabiei applied CMFs as the absorber layer between a boron carbide ceramic plate and Kevlar panels. This CMF-based body armor was able to withstand a round from a 7.62-mm x 51-mm battle rifle and a 7.62-mm x 63-mm M2 armor-piercing projectile.

Although existing Department of Justice–standard type IV body armor has comparable strength, CMF-based armor is substantially lighter. This advantage could potentially be extended to a host of defense and civil applications, such as military and law-enforcement vehicles, boat hulls, oil well drilling platforms and structural shock absorbers, to name a few.

However, CMFs can provide more than just strength. Rabiei’s tests have also shown that CMF is effective in shielding against various types of radiation, including X-rays, gamma rays and neutron radiation. CMF also has a high tolerance to heat, withstanding twice as much as ordinary metals. This would make CMF particularly useful in high-temperature environments and in space.

Currently, Rabiei’s team is working on tailoring CMF for armored vehicles to withstand small-arms fire, storage containers for hazardous material and aerostructure applications. Rabiei’s most recent paper on CMFs can be found in Advanced Engineering Materials.

"If others in the research community would like to work together in exploring additional applications, we'd love to talk to them," said Rabiei.

For more on metal foam, find out how this metal-foam hybrid brings “Transformers” to life.

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