This study used both the Cunniff and Phoenix-Porwal models in deriving two separate but similar theoretical relationships between the degradation in mechanical properties of aged body armor and its decreased ballistic performance.
It has long been a goal of the body armor testing community to establish an individualized, scientifically based protocol for predicting end-of-life of fielded body armor ballistic performance. A major obstacle in achieving this goal is that the test methods used to ascertain ballistic performance are destructive and require large sample sizes. The current article reports on two studies used to validate the derived functions. The first correlates the degradation in mechanical properties of fielded body armor to that produced by a laboratory accelerated aging protocol. The second examined the ballistic resistance and 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. This article presents correlations found between the tensile strengths of yarns extracted from armor and the V50 ballistic limit when significant degradation of the mechanical properties of the extracted yarns was observed. These studies provided the basis for a validation dataset from which this project compared the experimentally measured V50 ballistic limit results to the theoretically predicted V50 results. The theoretical estimates generally provided 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. (publisher abstract modified)