Scientists have demonstrated a light foam of hollow metal balls that can withstand the incredible impact of .50 caliber bullets: the kind of bullets fired by heavy machine guns and sniper rifles.
Weighing only about half of conventional steel armor, this material, referred to as composite metal foam (CMF), is equally effective at protecting these deadly projectiles, even when tested against armor piercing ballistics.
The CMF armor was less than half the weight of the rolled homogeneous steel armor needed to achieve the same level of protection, "says engineer and materials scientist Afsaneh Rabiei of North Carolina State University (NCSU).
In other words, we have been able to achieve significant weight savings that benefit vehicle performance and fuel efficiency without sacrificing protection. "
About 15 years ago, Rabiei was instrumental in the development of composite metal foam at NCSU. Days leads the university's Advanced Materials Research Lab (AMRL).
Her team experiments a lot in the lab to find out what this metal foam is capable of.
CMF, which is manufactured by patented processes, is made of metals such as aluminum and steel, interspersed with hollow air pockets throughout, like other types of foam.
In earlier investigations, Rabiei's team has shown that the CMF shown can, for example, extinguish medium-sized projectiles protected against the explosion of high-explosive projectiles, as well as protect against fire, heat and a range of radiation and radiation.
In the new Researchers wanted to see how CMF copes with the deadly force of .50 caliber bullets with a size of 12.7 x 99 mm One of the largest types of balls commonly used in conventional machine guns and long range rifles.
Their experiments consisted of firing bullets and armor punches in caliber .50 at speeds of 500 meters per second up to 885 meters per second.
In the tests, the CMF acted as an active core in armor covered with a ceramic faceplate with a thin aluminum backing plate.
19659003] The results showed that the CMF layer absorbed 72-75 percent of the kinetic energy of the balls and 68-78 Percent of the kinetic energy of the armor projectiles can absorb – and the penetration of projectiles at speeds of up to 819 prevents meters per second.
While Researchers Th It is amazing that this bubble-filled foam can hold projectiles at a speed of more than 800 meters per second.
"There is additional work we could do to make it even better," says Rabiei.
"For example, we want to optimize the adhesion and thickness of the ceramic, CMF, and aluminum layers, resulting in even lower total weight and improved final armor efficiency." We're looking for a kind of technical material that can stop some of the deadliest bullets used in the war – and a material that's only half as heavy as normal protection, so things like military vehicles could be lighter and more agile.
It's pretty clear that this kind of material advantage is badly needed – as long as gun manufacturers continue to manufacture bullets, that is.
The results are reported in Composite Structures .