Making a vehicle that’s completely impervious to bullets isn’t impossible, but it would be so bulky and heavy from its thick armour plating that it would barely be able to move. Unless you build it using a new bulletproofing material developed at North Carolina State University that mimics lightweight styrofoam.
Composite metal foam—or CMF, for short—is a material made from hollow metallic spheres that are surrounded by a matrix that can be made from various types of metals, including titanium or even alloys. If you’ve ever had to clean up those tiny white balls of styrofoam after unboxing a gadget, then you already have a good understanding of what this material is. The researchers behind this study made their CMF exclusively from steel, to maximise its strength and stopping power.
The CMF material was then sandwiched between a layer of ceramic, which served as a faceplate, and a thin aluminium backplate, to create a composite panel of armour. The panel was tested against 0.50 calibre ball rounds, as well as 0.50 calibre armour-piecing rounds, with impact velocities measured at speeds between 1,799km per hour and 3,187km/h. In other words, some of the nastiest projectiles it could experience in a conflict setting.
Upon impact, the layer of composite metal foam was able to absorb up to 75 per cent of the energy of the ball rounds, and up to 78 per cent for the armour-piercing rounds, as it crumpled. For comparison, a panel of armour made from rolled steel with the same stopping power would weigh at least twice as much as the composite armour tested in this study. That’s not only a significant amount of weight savings that could improve the safety, manoeuvrability, and fuel efficiency of armoured vehicles, the CMF panels also require considerably less raw material than solid steel for approximately the same amount of protection.
But it gets better. The researchers believe the composite armour could get even lighter by optimising the thickness of the ceramic and aluminium layers through additional testing and by improving the glue that holds the various layers of the panels together. The CMF material has also been found to be quite effective at blocking X-rays, gamma rays, neutron radiation, and can handle fire and heat at twice the temperature a solid steel plate can.
You can undoubtedly expect to find CMF in use by the military and law enforcement personnel once it leaves the lab, but it has other promising applications including better protecting spacecraft from debris and radiation, and even making cars safer. Most of us would also be quite happy to see this material incorporated into our smartphones as well, absorbing the impact of a fall with a few dents instead of a shattered screen.