Comparison of V50 Shot Placement on Final Outcome.

摘要

When characterizing ballistic performance of armor materials, V50 is a standard performance metric to consider. The V50 is the velocity at which a given projectile is expected to completely penetrate the material 50% of the time. The definition of a fair hit per MIL-STD-662F regarding shot placement states that the projectile must impact at least two projectile diameters away from any previous impact or disturbed area resulting from an impact. While this may work with ceramics or metal armor, it is inappropriate for use on composite armors like ultra-high-molecular-weight polyethylene (UHMWPE). In V50 testing of those types of materials, large delaminations may occur that influence the results. This report will expose the shortcomings of placing shots that result in delamination overlap in addition to other effects not mentioned in MIL-STD-662F. It will illustrate the possible differences in V50 results between virgin armor panels shot with and without resultant delamination overlap. These differences are important because an armor with a reported V50 resulting from numerous impacts in the same delamination area might give inaccurate results leading to false confidence as to the level of protection offered by the armor to the first impact. Generally speaking, with these types of composite armors, the V50 is lower when delamination overlap is avoided compared to the V50 resulting when the overlaps occur. Without knowledge of shot placement, a proper evaluation of materials may not be possible.