Stabbing Resistance of Soft Ballistic Body Armour Impregnated with Shear Thickening Fluid

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Layman's Abstract

Shear thickening fluid (STF) is a non-Newtonian fluid whose viscosity increases under shear loading [5]. The use of STF with high tenacity fabrics to enhance the performance against impact loading has received substantial attention [1-3], due to the negligible contributions to the thickness and stiffness of the fabric [4]. This research investigates the feasibility of ballistic armour panels impregnated with STF aiming for higher stabbing protection. STFs were made from SiO2 and polyethylene glycol (PEG), and efforts were made to control their critical shear rate and increase of STF viscosity. STF-Twaron® fabric specimens were fabricated to ensure full impregnation and STF continuity in the STF/fabric panels. To evaluate the stabbing resistant performance, as well as ballistic performance, 6 fabric panels were designed with STF from 12nm and 650nm silica particles with 3 different particle concentrations. Non-impregnated fabric panels with the same areal density and same number of layers as the impregnated one were also created. Stabbing impact test and ballistic test were carried out using these engineered panels.This work confirmed that rheological properties of STFs can be tuned by tailoring the production parameters. Larger SiO2 nanoparticle size led to lower critical shear rates and more obvious thickening effect. Higher particle concentration related to lower critical shear rates and greater jump in viscosity. The research revealed the existence of a minimum level of particle concentration for shear thickening behaviour to appear, and that higher molecular weight of PEG resulted in lower critical shear rate and more dramatic viscosity jump. The experimental results showed that for the 12-layer Twaron® fabric panels, the STF impregnated panel absorbed at least 58% of the impact energy, compared to the 20% absorption of the impact energy by the untreated panel. On the basis of the same areal density, the STF impregnated 12-layer panels provides 100% more enhanced energy absorption than the 24-layer untreated Twaron® fabric panel. The employment of STF in the panels also significantly reduced the back-face deformation caused by the knife impact. These findings indicate the feasibility of achieving more protective stabbing panels with lower weight and less bulkiness when STF impregnated panels are used against stabbing impact.Furthermore, STF impregnated Twaron® targets exhibit superior ballistic resistance compared with untreated Twaron® targets. This research explored the possibilities for new designs of smart textiles that could combine shear thickening behaviour with ballistic fabrics to achieve lighter soft ballistic body armour with higher stabbing protection.

Keyword(s)

Shear thickening fluid, stabbing resistance, ballistic performance,; rheological properties, soft ballistic body armour

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