Shear Thickening Fluids as Body Armour

Joel Bulley


Shear thickening fluids (STFs) are colloids that show an increase in viscosity with increasing shear rate. This phenomenon is suggested to be caused by the suspended particles jamming past some critical shear rate, which leads to dilation and viscosity increase. This behaviour makes them ideal for energy absorption applications, particularly for use in lightening body armour. STFs were fabricated using hollow glass microspheres coated in a hydrophobic surfactant, suspended in water and polyethylene glycol (PEG). Their rheological behaviours were then analysed to ensure that they displayed shear thickening regimes. The fluid that displayed all characteristics of a STF was then impregnated into Kevlar and tested for impact resistance, comparing with particles impregnated in Kevlar. Results from testing show STF impregnation increased impact resistance, and the particle impregnated sample having a similar impact resistance to STF samples. The conclusion being made that shear thickening is not the cause of increased impact resistance, but rather it is caused by the presence of micro-particles.

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