Deconstructing the role of shear thickening fluid in enhancing the impact resistance of high-performance fabrics

Abstract

The role of shear thickening fluid (STF) in enhancing the impact resistance of STF treated fabrics has long been debated. There is a need to clarify whether the dominant mechanism of energy absorption is shear thickening (dilatancy) or friction enhancement. This study establishes that the inherent shear thickening behaviour of STF has a decisive role to play other than just improving the yarn to yarn friction. Kevlar® 363 and Kevlar® 802 F fabrics were treated with STF comprising of 65% (w/w) silica and 35% polyethylene glycol (PEG) 200. Three monodispersed STFs and nine bi-dispersed STFs were prepared from three different particle sizes of silica (100 nm, 300 nm and 500 nm) and their binary mixtures keeping the mass fraction of silica constant (65%). Rheological results showed that STFs prepared form monodispersed silica resulted in higher peak viscosity as well as discontinuous shear thickening. However, bi-dispersed STFs prepared by mixing two different sizes of silica particles, in general, showed lower peak viscosity and continuous shear thickening. In both the fabrics (Kevlar® 363 and Kevlar® 802 F), yarn pull-out force, a measure of yarn to yarn friction, did not show much difference among the fabrics treated with different STFs. However, low velocity impact tests clearly showed enhanced performance in terms of energy absorption and peak force in case of fabrics treated with monodispersed STFs. This correlation between shear thickening and impact resistance conclusively establishes that the former has a dominant role in enhancing the latter of high-performance fabrics.