The spheres inside the composite metal foam absorb the energy of a bullet. (North Carolina State University)
Army Times has a story about a new form of armor that might be use to provided repeated protection against small arms and fragments.
A 7.62mm rifle round will go through 3 inches of steel, so a catcher material is put behind the steel, he said. (This is probably incorrect. Probably should have been 0.3 inches–Chuck)
“When the bullet hits the ceramic, it stops and absorbs the energy,” Portanova said. “The problem is you can only shoot it once because then it’s cracked.”
Composite metal foam, however, has a bunch of hollow spheres inside. When struck with a bullet, the spheres are crushed, similar to bubble wrap.
Because of its resilience, you can hit it numerous times, Portanova said.
Researchers at the directorate have helped make the material lighter and also stop bigger threats.
…
“It would only be slightly more expensive and will weight half or one-third of what they’re hanging on the side of a Humvee.”
Chuck Hill's CG Blog 
“A 7.62mm rifle round will go through 3 inches of steel.” No, it will not. A 76mm round perhaps.
Same/Similar.
Super Bainite/PAVISE™ SBS 600P., the new armour steel has been developed to have outstanding ballistics properties and, in tests, it has performed better than ‘normal’ steel armour.
The ballistic performance of perforated Super Bainite steel armour is at least twice that of conventional rolled homogenous steel armour. This is because the introduction of perforations creates a large number of edges which disrupt the path of incoming projectiles, significantly reducing their potency.
Permali Gloucester Ltd, a world leader in the manufacture of composite materials for the defence industry, said: “As part of a complete appliqué armour system we have found PAVISE offers unique benefits in particular areas”
https://www.tatasteeleurope.com/en/news/news/2013/2013_lightweight_armour_steel_trade
7.62 NATO AP rounds will penetrate about 1/4 inch harden steel at 500 meters.
So perhaps 0.3″ at a closer range. Thanks for the confirmation.
Commentary and video here. http://www.eaglespeak.us/2018/03/hey-navy-ship-designers-need.html