U.S. ARMOR PLATES’ BALLISTIC PROTECTION SCRUITINIZED FOR SOLDIER SAFETY
06 Dec 13. A team of U.S. Army engineers is enhancing Soldier safety in ground vehicles by scrutinizing and validating improved alloys for armor-plate applications. The military’s ground systems require better structural armor plate materials to meet the ballistic and blast threats from America’s adversaries while withstanding the corrosiveness of harsh combat environments, the group said.
The U.S. Army Research Laboratory, known as ARL, one of seven organizations that make up the U.S. Army Research, Development and Engineering Command, is leading the effort. The group has turned to the Office of the Secretary of Defense Comparative Technology Office for funding. As aluminum manufacturers, both domestic and foreign, developing a new alloy to be considered for America’s ground forces, ARL engineers place the product through a series of standardized tests to validate the material’s performance in the ballistic protection level, corrosion resistance and weldability. Because ARL has the expertise for all three technical areas, its engineers perform the tests concurrently.
“We are the independent evaluators,” said Rich Squillacioti, materials engineer and leader of the Specifications and Standards Office, explaining that ARL evaluates the claims of manufacturers to ensure that Army requirements are met. Adhering to the requirements for all three aspects — ballistic protection level, corrosion resistance and weldability — is critical to Soldier safety because a failure could be catastrophic, said Brian Placzankis, team leader for the Corrosion and Surface Science Team at ARL.
“The ARL Weapons and Materials Research Directorate is trying to down-select viable plate alloys for the Army to use. We separate the contenders from the pretenders,” Placzankis said.
The group is composed of five ARL Weapons and Materials Research Directorate, or WMRD, engineers — Placzankis; Squillacioti; Tyrone Jones, mechanical engineer in the Armor Mechanisms Branch; Denver Gallardy, general engineer in the Armor Mechanisms Branch; and Kevin Doherty, materials engineer in the Lightweight and Specialty Metals Branch.
CREATING, AND MAINTAINING MILITARY SPECIFICATIONS
Squillacioti said ARL is responsible for creating and maintaining the Army’s material specifications that include armor-plate specifications for steel, aluminum and magnesium. The military specifications determine minimum acceptance values for ballistics, mechanical and chemical properties for different plate thicknesses. Performance values are determined for each material alloy, and manufacturers use these to design new ground systems or upgrade existing platforms. These specifications ensure these material alloys are consistently created to maintain performance values by testing random samples of the alloy against minimum acceptance requirements, known as quality-assurance provisions.
DEMONSTRATING PERFORMANCE IMPROVEMENTS
The analysis has resulted in a significant protective benefit as Aluminum Alloy 7017 has demonstrated a reduction in spallation compared with the legacy AA7039, Jones said. An armor plate must not only arrest the projectile, but mitigate the kinetic energy before it fatally compromises a protected asset.Gallardy described the issue of spall, a plate failure in which material is ejected off the back of the armor plate.
“When a projectile strikes the front of the plate, it sends a compressive wave through the plate. The compressive wave hits the back surface of the plate and it reflects as a tensile wave,” Gallardy said. “If the tensile stresses developed by the wave are higher than the tensile strength of the material, you get a large piece of a material, bigger than the caliber of the projectile, that breaks off. Even though the projectile stopped in the plate, a piece of material with residual energy capable of causing damage flies off the back.”
Spallation is not a c