Nano-Modified Hybrid Recycled Composite: An Alternative for Ballistic Shields

Abstract

A critical issue on ballistic materials, in addition to the impact resistance is weight. One class of fibers that combines a good weight/impact resistant ratio is aramid fibers. The usage of aramid fibers into bulletproof vests takes the advantage of such good properties. However, the high cost of these fibers is a disadvantage and these vests cannot be discarded without proper treatment, thus a recycling procedure is urgent. This paper investigates new applications for aramid fabrics from discarded bulletproof vests and its application as ballistic shield. The new ballistic composite material is a hybrid laminate, where recycled aramid fibers are consolidated by epoxy resin and a shear thickening fluid (STF) reinforcement. The aramid fibers from bulletproof vests have an areal density of approximately 300 g/m2 (12.6 oz./yd2) and were intercalated to form a symmetric and balanced laminate. The epoxy system is an amine-cured bisphenol-A-diglycidyl ether epoxy resin from Barracudatec Inc., while the nano-reinforcements are colloidal silica and powder of organically modified montmorillonite nanoclay (Cloisite 30B). As this research deals with two different levels of analysis, i.e. the first one on nanoscale and the second one on macro scale, the experimental investigation must be divided in two different time frames. At nanoscale, the nanostructures are investigated by SEM and FTIR. At macro scale, ballistic tests are based on the NIJ Standard–0101.04. Two types of ammunition are considered, i.e. 9 mm Full Metal Jacketed (FMJ) and 357 Magnum Jacketed Soft Point (JSP). The results demonstrated a significant enhancement (close to 25%) in ballistic penetration resistance due to the addition of shear thickening fluid to the recycled fabric, without any loss in material flexibility. Moreover, the new system can be applied to shield and patrol cars protection system at low cost with the same efficiency of the new aramid fibers.