No abstract

This publication details the four major phases of analytical development work, coupled with several additional side studies, undertaken by the Office of Law Enforcement Standards in writing the Flexible Armor Conditioning Protocol in NIJ Standard-0101.06. This protocol partially fulfills a requirement to develop a revised performance standard for body armor to address a number of concerns, one of which was the ability of the armor to withstand environmental and wear conditions that an armor might see over its lifetime. This document details how the protocol was shortened from 9 weeks in the first phase of development to 10 days, as it appears in the current version of the standard. All major classes of ballistic materials were tested in the protocol development. The conditions selected are found to be quite detrimental to armors of a design that previously had problems in the field, but are not detrimental to armors of known good design. It is important to note that the protocol does not represent an exact period of time in the field, but efforts to correlate the protocol to a period of time in the field are the subject of future research.

No abstract

It has long been a goal of the body armor testing community to establish an individualized, scientific-based protocol for predicting the ballistic performance end of life for fielded body armor. A major obstacle in achieving this goal is the test methods used to ascertain ballistic performance, which are destructive in nature and require large sample sizes. In this work, using both the Cunniff and Phoenix-Porwal models, we derived two separate but similar theoretical relationships between the observed degradation in mechanical properties of aged body armor and its decreased ballistic performance. We present two studies used to validate the derived functions. The first correlates the degradation in mechanical properties of fielded body armor to the degradation produced by a laboratory accelerated-aging protocol. The second examines the ballistic resistance and the extracted-yarn mechanical properties of new and laboratory-aged body armor made from poly(p-phenylene-2,6-benzobisoxazole), or PBO, and poly(p-phenylene terephthalamide), or PPTA. We present correlations found between the tensile strengths of yarns extracted from armor and the ballistic limit (V50) when significant degradation of the mechanical properties of the extracted yarns was observed. These studies provided the basis for a validation data set in which we compared the experimentally measured V50 ballistic limit results to the theoretically predicted V50 results. The theoretical estimates were generally shown to provide a conservative prediction of the ballistic performance of the armor. This approach is promising for the development of a tool for fielded armor performance surveillance relying upon mechanical testing of armor coupon samples.