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Idaho National Laboratory

From the INEEL Archives
Feature Story

Retooling Armor: INEEL Researchers Bring High-Tech Solutions to an Ancient Problem

Contributed by Kathy Gatens
August 2002
Testing the creamic composite.

A marksman zeros in a rifle to test a new ceramic armor composite.

Armor is almost as ancient as war itself. Five thousand years ago, Egyptian soldiers marched into battle wearing body armor in the form of a quilted belt stretching from their armpits to their knees. Not far away and during that same time period, tight-fitting caps of beaten copper protected the heads of Sumerian fighters. By the 15th century, a medieval knight rode a heavy charger while fully encased in articulated plate weighing as much as 65 pounds, yet so well-fitted that he could mount his horse without stirrups.

The knight was almost invulnerable against pointed weapons - swords, lances, and knives. But when the weapon changed to lead bullets, the armor needed to protect against that increased threat became too heavy to be practical and was soon abandoned.

In the centuries since, the threats have increased and the armor material has changed but the relationship of weight versus protection remains a critical factor. An anonymous author summarized the history of armor development in four lines.

  1. Weapon - Armor
  2. Bigger Weapon - Heavier Armor
  3. Bigger Weapon - Refined Armor
  4. Bigger Weapon - Heavier Refined Armor

Military Armor

The U.S. Army categorizes armor - light, medium and heavy - based on pounds per square foot. Each type of armor is designed to stop a certain caliber of threat. A new category of ultra-lightweight was instituted about 10 years ago to address body armor requirements.

INEEL mechanical engineer Henry Chu has delved some into the high-density, polyethylene "Kevlar-type" ultra-lightweight armors. For INEEL’s National Security Division and its U.S. military customers, however, Chu primarily develops and tests lightweight armor. This armor, weighing 20 to 25 pounds per square foot or less, is designed for vehicles and aircraft - everything from limousines carrying presidents to troop carriers for special forces.

Chu - teaming with other INEEL researchers - first tasted success with an alumina powder ceramic armor. The key is the high-purity and fine, uniform size of the starting powder. Using a concept initiated at Michigan Technological University, the team produced a denser and stronger fine uniform grain-sized alumina plate at relatively low temperatures and short duration. The resultant material was denser and stronger than commercially available material.

armor2

A hydraulic dolly used to raise the armor sample into position for ricochet tests. A hydraulic dolly used to raise the armor sample into position for ricochet tests.

Lightweight ceramic armor such as this became the military standard but armor never stops evolving. The Army is now driving research and industry into developing and improving other advanced ceramics such as silicon carbide and boron carbide. These materials are either less dense than alumina, or possess better ballistic performance, or both. Trouble is, quality and quantity of starting material are hard to come by, therefore constraining use. These materials require greater temperatures during processing - 1,900 to 2,000C compared to 1,200C for alumina - and still do not lend themselves to sintering. Chu and colleague Tom Lillo are working on solutions through INEEL’s Laboratory Directed Research and Development program.

"The importance of the LDRD program is clear in armor research," says Chu. "It allows us to plant the seed of initial development, demonstrate proof-of-concept, and subsequently obtain external funds to bring the products to market."

Chu and Lillo’s concepts also snared a commercial partner who provides the raw material and who - together with the INEEL team - is responding to a Broad Agency Announcement to provide 15 samples to the Army for testing.

According to Chu, only about three commercial companies manufacture advanced ceramic armor for the military and they are unable to keep up with even limited production. The Army wants other sources, and Chu’s industrial partner would like to be one of them.

The material continues to undergo tests at INEEL’s live-fire range. Results are good, but Chu will continue research and testing until he is satisfied that the material is as good as it can get. In the meantime, he works on the opposite spectrum from material development. Chu provides technical advice to the government and the contractor manufacturing armored riverboats.

Under Fire

The public is familiar with this type of boat, having seen them in news clips of wars in foreign lands and in movies such as Apocalypse Now. INEEL researchers wrote the armor requirements for the boat and the INEEL team, including Chu, reviewed and tested several proposed solutions.

Chu included one requirement in the specifications that was different from anything written before. The requirement resulted from a test Chu had witnessed sometime earlier. Initial tests on a new armor validate the material itself. Can it withstand the threat; stop the bullet? Once that is proven, additional experiments test the product design, or how the armor is put together. Chu witnessed the test of the first prototype riverboat under scripted combat conditions. The boat was launched and attacked from the land. Sharpshooters aimed at vulnerable points. To make the test more realistic, full-scale silhouettes of soldiers were placed in normal operating positions in the 9- by 31-foot boat. The shooting began.

The armor withstood the barrage of bullets effectively and passed. But when Chu examined the boat closely, he saw stray shots had riddled the silhouettes. It wasn’t poor marksmanship; it was ricochet. Chu recognized that deflection wasn’t enough, the armor had to absorb the bullet. Chu incorporated this requirement into the specifications for the riverboat.

For the next two months, Chu worked closely with the manufacturing contractor to improve the armor solutions. The resultant product stopped and controlled the projectile, becoming a "bullet trap." That boat is now in production in Louisiana and Chu regularly takes calls from the manufacturer. He will provide ongoing consultation until the fleet is finished.

As good as Chu and Lillo’s research is, another component makes INEEL armor development so strong, the live-fire test range.

"The live-fire test range is absolutely critical to our research," says Chu. "You can only conceptualize so much. Ballistic impact is such a violent phenomenon that it defies imagination. Armor designers always get humbled in the end. We still lack full understanding on how armor really works. A lot of theories and basic principles have been devised and published on armor systems and materials, but in the end, one still has to perform live-fire tests with any potential solution to ensure there are no surprises."

The range supports not only research and development, but also the day-to-day training and certification of INEEL’s elite security forces. Its combination of multiple ranges, shooting house and environmental controls makes it fairly unique, and not just in the Department of Energy complex. Security forces from around the state and other locations have come to train there. Furthermore, the Laboratory can offer independent testing and certification to any organization developing armor products. The National Security Division considers it a vital component as it establishes the INEEL Critical Infrastructure Test Range.

Whether Henry Chu is developing his own armor solutions, consulting for the military, or testing an armor product, he keeps the engineering focus of the INEEL in mind.

"We see a lot of proposed solutions. Some are not realistic, and some would just waste taxpayer money. We want to stay practical, application-driven. We want to emphasize the engineering integration part. After all, this is not abstract research; this armor can save soldiers’ lives. This armor is good for the country."

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