The objective of this research was to characterize the ballistic performance of p-aramid fabrics impregnated with shear thickening fluid (STF) focusing on the laminating sequence of the layers. A panel of all neat Kevlar fabrics and two hybrid panels of neat and STF impregnated Kevlar fabrics were tested against 9 mm bullets at 436 m/s for body armor application. When the STF impregnated fabrics were laminated behind the neat Kevlar layers (N/S-panel), the backface signature decreased compared to the panel of all neat fabrics (N-panel) and the hybrid panel with neat Kevlar layers placed on the backside of the panel (S/N-panel). The enhanced ballistic performance of the N/S-panel was assumed to be due to the synchronized (or coupled) elongation of the facing yarns in the frontal layers and those in the following rear layers during the impact. Analysis was carried out, by adapting the method of accumulating successive line segments, to present the energy dissipation route of each panel during the impact.

The objective of this research was to characterize the ballistic performance of p-aramid fabrics impregnated with shear thickening fluid (STF) focusing on the fabric count and shot location. Panels made of fabrics with different fabric counts were tested against 9 mm bullets at 436 m/s for body armor application. Panels with higher fabric count dissipated a higher fraction of the given impact energy through tensile dissipation and this led to a lower backface signature. The decrease in backface signature value by the hybridization of neat and STF impregnated fabrics was smaller for panels of densely woven fabric due to the larger difference in the warp and weft crimp ratios. Shot location affected the ballistic limit value ( V50), as well as the BFS value of the panels, where both values increased as the shot location approached the edge. The energy transferred to the backing material upon an impact was calculated based on the weight dropping test results, where the dent volume was proportional to the impact velocity.

The aging of propellants in PMDs is considered to be one of the primary factors affecting the performance of PMDs. Thus, studies on the aging mechanism of propellants, which have not yet been addressed extensively, pose a solution to securing the sustainable operation of PMDs. We characterized one of the most commonly used commercial propellants (boron potassium nitrate (BKNO3)) and investigated its aging mechanism rigorously. Based on thermal analyses, we demonstrate that the decomposition of laminac, a polymer binder, is the fastest spontaneous reaction. However, it will not self-initiate at a storage temperature as high as 120 °C. The effect of the humidity level was examined by characterizing BKNO3 samples prepared. The heat of reaction and the reaction rate decreased by 18% and 67% over 16 weeks of aging, respectively. This is attributed to the oxide shells on the surface of boron particles. The formation of oxide shells could be confirmed using X-ray photoelectron spectroscopy and transmission electron microscopy–energy dispersive spectroscopy. In conclusion, surface oxide formation with the aging of BKNO3 will decrease its propulsive efficiency; oxidation reduces the potential energy of the system and the resulting oxide decreases the reaction rate.

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