Researchers have demonstrated that vehicle armor using composite metal foam (CMF) can stop ball and armor-piercing .50 caliber rounds as well as conventional steel armor, even though it weighs less than half as much. The finding means that vehicle designers will be able to develop lighter military vehicles without sacrificing safety, or can improve protection without making vehicles heavier. CMF is a foam that consists of hollow, metallic spheres — made of materials such as stainless steel or titanium — embedded in a metallic matrix made of steel, titanium, aluminum or other metallic alloys. In this study, the researchers used steel-steel CMF, meaning that both the spheres and the matrix were made of steel. For the study, researchers manufactured a hard armor system consisting of a ceramic faceplate, a CMF core and a thin back plate made of aluminum. The armor was tested using .50 caliber ball and armor-piercing rounds. The armor was tested with the rounds being fired at impact velocities from 500 meters per second up to 885 meters per second. The CMF layer of the armor was able to absorb 72-75% of the kinetic energy of the ball rounds, and 68-78% of the kinetic ener...