Demand Activated Toughening in Garments.

Although armor protective fabrics do not have a very large market share (some 200,000 units per year, but increasing every year), their high added value is counted in the number of lives they save each year and in the number of serious life threatening injuries they prevent. Law enforcement agents routinely use them to protect themselves from hand-held weapons fire. Such fabrics are used in areas where there exists a potential threat to life due to high velocity projectiles (e.g. bullets and shrapnel, containers for check-in baggage in airplanes to protect from explosives, etc.). However, existing multilayer fabric vests used for this purpose are heavy and bulky to wear, and usage of such fabrics in extreme conditions (such as in jet engine containment walls to capture broken blade projectiles) causes thermal oxidative degradation of organic fibers resulting in diminished properties. Successful completion of our effort will provide additional means for protecting lives and body parts from various impacts and impact-generated projectiles. In addition, instead of relying solely on the innate strength and modulus of plied fabrics to resist impact damage, as is currently done, the proposed work would provide an "intelligent" fabric system that transforms into a tough/hard material only when needed, i.e., only when triggered by a high velocity projectile impact. This project is particularly important now that Homeland Security is a high National concern. The basic mechanism involves shock-induced reactions in a carefully chosen metal/polymer system or polymer system with metal/metal mix that transforms into a hard impact resistant material. The reactions occur because of the actual stress waves generated by the penetration of the projectile, hence the transformation takes place due to shock waves that move ahead of the projectile in the material. The selection of particle/polymer system as well as their distribution is the most important aspect in maximizing the transformation toughening of garments, and we have been focusing on understanding the mechanism of this transformation in order to enhance ballistic resistant properties of fabric systems. [ABSTRACT FROM AUTHOR]