A new composite metal foam (CMF) has the potential to offer unprecedented protection from bullets or other projectiles. Developed by researchers with North Carolina State and the U.S. Army Research, Development and Engineering Center, this armor can dissolve a bullet into dust upon impact.
Less than 25 millimeters thick, the armor consists of "ceramics as the strike face, composite metal foam processed by powder metallurgy technique as a bullet kinetic energy absorber interlayer, and aluminum 7075 or Kevlar panels as backplates," according to the 2015 study.
Afsaneh Rabiei, a professor of mechanical and aerospace engineering at North Carolina State, says the indentation made by a bullet (sized according to standards from the National Institute of Justice) is about 8 millimeters, although the standard allows for an indentation of up to 44 millimeters.
A video posted by NC State shows how the foam obliterates a 7.62 x 63 millimeter M2 armor piercing projectile upon contact.
The metal foam consists of metallic pores made of a combination of materials such as carbon, steel, stainless steel or titanium.
Because these foams are also lighter than metal plating, the material has obvious implications for creating new types of body and vehicle armor--and that’s just the beginning of its potential uses.
WHAT IS POWDER METALLURGY?
Powder metallurgy (PM) is a cost-effective process for forming metal parts by heating compacted metal powders to just below their melting points, according to Andrew McWilliams, a BCC Research analyst.
Its production methods can be used to fabricate large numbers of parts with complex shapes that meet demanding specifications, like the CMF developed by Rabiei and her colleagues. Unlike conventional machining, PM creates very little scrap or waste.
Most parts produced under the PM process are small, but they are strategically important to the auto, aircraft, hardware, instrumentation, oil and gas well-drilling equipment, and off-road tractor industries. A typical automobile contains more than 40 pounds of PM parts. Aircraft engine turbines, riding lawn mowers, power tools and surgical instruments depend on the PM process for their formation and strength.
Powder metallurgy technology is still evolving, McWilliams says, and the industry has adopted particulates, i.e., powders and materials not made solely of metals. Products are also changing, and PMs can be adapted or modified to meet their demands.
Technological progress has continued as iron-based powders with increased compressibility have been introduced, along with insulated iron powders, powder injection-molding equipment and warm-compaction technology. Powder metallurgy components that offer cost-effective alternatives to machined components, castings and forgings also are expanding their markets. In addition, standards have been refined and greater emphasis has been placed on user benefits.
CMFS OFFER A WIDE ARRAY OF POTENTIAL USES
But there are many applications that require a material to be more than just incredibly light and strong. For example, applications from space exploration to shipping nuclear waste require a material to be not only light and strong, but also capable of withstanding extremely high temperatures and blocking radiation.
Last year, with support from the Department of Energy’s Office of Nuclear Energy, Rabiei showed that CMFs are very effective at shielding X-rays, gamma rays and neutron radiation, Matt Shipman notes.
And earlier this year, A previous study Rabiei conducted also demonstrated that composite metal foams can withstand extremely high temperatures and can protect from fire and heat twice as better as traditional metal.
“The presence of air pockets inside CMF make it so effective at blocking heat mainly because heat travels more slowly through air than through metal,” she explains.
McWilliams projects that powder shipments will exceed 3.3 billion pounds (for a value of $8 billion) in 2015 and approach 4.3 billion pounds ($13.5 billion) by 2020. These figures represent a CAGR of 5.1% in volume terms and a 10.9% rise in market value between 2015 and 2020.