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BODY ARMOR TESTING RESULTS

 By Bill Siuru, Ph.D., PE 

Do materials in body armor degrade? Do upgrade kits return “like new” performance to used armor? Why did body armor fail to protect a Forest Hills, PA, officer? An attempt to answer these and other questions through testing are covered in the recent Supplement I:  Status Report to the Attorney General on Body Armor Safety Initiative Testing and Activities. This latest research is part of the DOJ’s Body Armor Safety Initiative announced by Attorney General Ashcroft in 2003 to address concerns about the effectiveness of body armor.

The NIJ’s research supports the fact that ballistic-resistant materials, including Zylon®, can degrade. Degradation may reduce the ballistic resistance safety margin manufacturers build into armor designs. It is imperative that manufacturers understand the vulnerabilities of materials used, protect the materials against these vulnerabilities, and account for any performance loss when designing armor.

Upgrade Kits

To evaluate upgrade kits, Second Chance Body Armor, the only manufacturer offering an upgrade kit for certain models of Zylon-based body armor, provided approximately 50 armors and matching upgrade kits for testing of each of the three primary soft armor protection levels (Levels IIIA, II, and IIA). Samples included both new and previously worn upgraded Second Chance Ultima® and Ultimax® models.  Ultima models achieve all of their ballistic protection from Zylon, whereas Zylon and other ballistic materials are used in Ultimax models. Because Zylon degradation reduces ballistic performance, Ultima models were used because the all Zylon construction was considered more likely to exhibit signs of degraded ballistic performance. To be acceptable, the upgrade kits had to successfully defeat a total of 48 shots of the same two threat rounds (24 each) as specified in the NIJ standard.

Results

Upgrade kits did not bring used Second Chance armor up to the level of performance of new Second Chance armor and significant backface signatures were experienced during testing.

Armor tested is mounted on clay backing material. After the shot, the depth of the clay deformation behind the armor panel is measured and recorded as the backface signature. Additionally, two of the Level IIIA armor samples experienced a penetration when tested with an upgrade kit, so the upgrade kit does not afford adequate protection for Level IIIA armor. Although the upgrade kits did not return the well-worn armor samples to the level of performance of new armor, they did provide added protection. Ultima and Ultimax models with the upgrade kits provided greater safety than the Ultima and Ultimax models alone. Officers who continue to wear the Ultima and Ultimax models should continue using their upgrade kits.

Penetration Study

In 2003, a Forest Hills, PA, police officer was seriously injured when a bullet penetrated the front panel of his Ultima armor. This incident is the first reported to the NIJ where NIJ compliant body armor appears to have failed to prevent penetration from a bullet it was designed to defeat.

To find out why, the NIJ obtained the rear panel of the officer’s armor for testing. The tensile strength (a critical property influencing ballistic performance of body armor) of the removed Zylon yarns was found to be up to 30% lower than yarns from “new” Second Chance armor of the same model.

A total of 32 new ballistic panels were tested – 16 “as supplied” by Second Chance and 16 weakened in a temperature and humidity chamber for five months to match the condition of the officer’s armor.  Five factors which may have played a role in the incident were included in the test plan: tensile strength, bullet type, barrel twist, shot angle, and shot location on armor. To test all combinations of the five factors on all panels, a total of 192 shots were used. Since none penetrated any of the armor panels, the cause of the body armor penetration cannot be explained. However, several other factors which may have contributed to the penetration have been identified. These include: (1) the possible lower tensile strength of the front panel’s ballistic material (the penetrated panel was not available because it was needed as evidence); (2) other mechanical properties which might also influence ballistic strength; (3) differences in properties and behavior determined using standardized tests under “static” conditions (i.e., forces applied to yarns very slowly) compared to “dynamic” conditions (i.e., forces applied to yarns very rapidly – as when a yarn is struck by a bullet); (4) other possible causes, including mechanical damage due to folding, flexing, abrasion, and other wear effects; and (5) moisture in an armor panel influencing ballistic resistance. Ongoing and planned studies may yet explain the Forest Hills penetration.

Ongoing Research

The NIJ is continuing to research the causes and mechanisms of armor degradation. Analytical techniques and tools are being developed to identify the cause and extent of body armor degradation. Currently, the only method of testing armor performance is destructive; that is, ballistic testing. NIJ research could result in test protocols to validate the performance of used armor and a nondestructive test procedure for ballistic armor. For the second phase of testing under the initiative, approximately 500 armors have been randomly selected for testing from five different climatic regions, five different age categories, and four different manufacturer categories. Evaluating body armor from different climatic regions may determine whether temperature and humidity affect body armor performance.

It is important to note that police homicides have declined steadily since the introduction of body armor and the initiation of the DOJ’s body armor standards and testing program. The lives of more than 2,800 police officers have been saved by body armor. An officer not wearing armor is 14 times more likely to be fatally wounded than one wearing armor. Therefore, officers should continue to wear body armor and carefully follow manufacturers’ instructions concerning its use and care.n

 A copy of this supplemental report is available on-line at:
https://vests.ojp.gov/docs/207605.pdf.

About the Author: Bill Siuru is a retired USAF colonel.  He has a Ph.D. in mechanical engineering from Arizona State University.  His military assignments include teaching engineering at West Point, commander of the research laboratory at the U.S. Air Force Academy and Director of Engineering at Wright-Patterson AFB.  For the past 35 years, he has been writing about automotive, aviation and technology subjects.