Soft body armors have been widely used by law-enforcement and military personnel.However, predictive capabilities on the critical conditions for the impact failure of thesearmors are still not well-developed. This article summarizes our recent experimentalresearch efforts aimed at developing a better understanding of impact failure of soft bodyarmors at several size scales, ranging from shoot packs, single-plies, yarns, and fibers. Theexperiments reveal that impact resistance of packets is dictated by axial properties andshear strength of the textile materials, as well as structural properties such as weavepatterns. At the single-ply level, the critical impact velocity depends heavily on the noseshape of the projectiles, as well as the axial and transverse properties of the yarns. Thefailure of yarns and fibers depends on the stress state, as interpreted from the effects of noseshapes of the indenters and from the application of multi-axial stress states. The effects ofaging on the impact resistance is also discussed.
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