Armor plates' ballistics protection scrutinized for Soldier safety

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.


While the ARL engineers possess the research knowledge and capability to provide the improved armor plate, funding is required for materials and equipment such as bullets, X-rays, guns and powder. They used the Office of the Secretary of Defense Comparative Technology Office's Defense Acquisition Challenge and Foreign Comparative Testing programs.

"FCT provides foreign vendors the 'on ramp' to Army acquisition," said William "Randy" Everett, FCT project officer at RDECOM headquarters. "When a foreign company has a mature technology or product that the U.S. Army has a requirement for, FCT allows program management offices to leverage OSD funds to test and evaluate the technology for procurement."

Because the group took advantage of both DAC and FCT opportunities, it was able to simultaneously evaluate alloys from domestic and foreign aluminum companies.

The Department of Defense established DAC in 2003 in response to a Congressional mandate for a program that was innovative, flexible, competitive and affordable to integrate mature technologies into the acquisition cycle. FCT's mission since 1980 has been to find and evaluate "here and now" solutions to meet operational needs regardless of the origin of that technology.

The Office of the Secretary of Defense Comparative Technology Office evaluates the proposals and selects candidates for funding. The RDECOM Global Technology Integration Team manages the programs for the Army. DAC was funded through fiscal year 2012.


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.


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 certain failure mode for all metal armors under ballistic impact, Jones said.

"There is a critical thickness where spallation of a plate begins under ballistic loads. Spall is a function of armor plate thickness and momentum transferred by a projectile into the armor plate," Jones said.

The weldability of alloys is also a vital consideration during the testing process, Doherty said. Many of the features of an alloy's chemistry and heat treatment that lead to improved strength and ballistic protection typically degrade the weldability.

"Operational conditions for ground vehicles are different from what you see in the normal world. The welds experience severe stresses that are magnified during a ballistic impact or blast event," Doherty said. "They need to handle much more than welds do in the everyday world."


The group emphasized that the goal of this program is not to design armor systems. Its role is to define whether a new or re-designed aluminum alloy's properties exceed the current material options. The new option could then be incorporated into a program managers' designs.

Without these quality controls, the Army would be unable to determine whether the material being purchased meets the necessary stringent requirements, Squillacioti said.

ARL's work allows new alloys to be introduced as replacements or improvements of the existing material to legacy vehicles that are being repaired or upgraded. This can provide better protection and performance without incurring additional costs because the new alloy can be incorporated into an existing specification, Placzankis said.

"If we validate a new material and it fits into an existing specification, that is an opportunity for an upgrade without totally altering the drawings, which can be very expensive," Placzankis said.

A key aspect of the engineers' work is the immediate impact on legacy, current and future Army ground vehicle platforms, Squillacioti said.

"It's all working toward vehicles that are in production or that are going to be in production in the near future," he said. "There is a direct use. It's not just something that's going to sit on a shelf. It's going to be implemented."

The aluminum alloys validated by ARL can be applied to all types of vehicles, depending on the PMs' needs. These include mine-resistant ambush-protected vehicles, commonly known as MRAPs; Humvees; and lightweight armored vehicles such as personnel carriers and the Bradley Fighting Vehicle.

Source: US Army
Date: Dec 4, 2013