Researchers at North Carolina State along with help from the Joint Aviation Survivability Program have demonstrated a new type of composite metal foam, or CMF, that can stop armor-piercing anti-materiel rounds up to .50 BMG as well as steel.
The CMF weighs less than half as much as a similar amount of steel armor plating, which means that future armored vehicle designs can either be lighter without giving up armor capacity or add additional armor without tipping the scales.
Researchers describe the foam as a matrix of hollow metal balls made using materials like stainless steel and titanium suspended in another alloy of aluminum, steel or titanium. For this experiment, the researchers tested steel spheres in a steel matrix although other combinations are possible.
“The CMF armor was less than half the weight of the rolled homogeneous steel armor needed to achieve the same level of protection,” said North Carolina State’s Afsaneh Rabiei, a professor of mechanical and aeronautical engineering.
The researchers tested a composite armor made using a ceramic faceplate, a CMF core and an aluminum backplate with standard and armor-piercing .50 BMG rounds. Sandwiched between the other two layers the CMF material was capable of absorbing as much as 78 percent of the kinetic energy of both ball and AP ammo, performing on-par with solid steel.
“In other words, we were able to achieve significant weight savings – which benefits vehicle performance and fuel efficiency – without sacrificing protection,” said Rabiei.
“This work shows that CMF can offer a significant advantage for vehicle armor, but there is still room for improvement,” she continued. “These findings stem from testing armors we made by simply combining steel-steel CMF with off-the-shelf ceramic faceplates, aluminum back plate and adhesive material.
“We only optimized our CMF material and replaced the steel plate in standard vehicle armor with steel-steel CMF armor,” said Rabiei. “There is additional work we could do to make it even better. For example, we would like to optimize the adhesion and thickness of the ceramic, CMF and aluminum layers, which may lead to even lower total weight and improved efficiency of the final armor.”
In other experiments Rabiei and her team used CMF armor to completely stop the blast pressure and fragments from high explosive incendiary rounds from just 18 inches away. Her team also demonstrated CMF less than an inch thick stopping .30-06 AP rounds with little deformation.
Additionally, the composite metal foam is more capable of stopping heat and radiation. The team showed the material absorbing more X-rays, gamma rays and even neutron radiation than conventional metals while absorbing twice as much heat before starting to compromise.
“In short, CMFs hold promise for a variety of applications: from space exploration to shipping nuclear waste, explosives and hazardous materials, to military and security applications and even cars, buses and trains,” Rabiei says.