The influences of rheological property on the impact performance of kevlar fabrics impregnated with SiO2/PEG shear thickening fluid

Shear thickening fluids (STFs) have been proven promising in enhancing the anti-impact performance of woven fabric, which can be incorporated into soft-wall containment casing in aero-engine applications. In the current study, STFs having distinct different shear thickening behaviors were investigated through yarn pull-out and ballistic impact tests to understand the relationship between the rheological behavior of STFs and their effect in enhancing impact resistance, which provide insight into the design of STF-treated soft-wall casing. Spherical SiO2 particles of diameters 100 and 650 nm were employed to prepare the STFs, which were referred to as a-system (100 nm particles) and b-system (650 nm particles). The rheological properties were investigated for two STF system series. The critical shear rate is 0.6–3.2 s−1 for a suspension system composed of 650 nm silica particles, whereas the critical shear rate is 169–627 s−1 for that of 100 nm particles. Kevlar fabrics were impregnated with STFs, and ballistic impact tests were conducted on different types of STF–Kevlar and neat Kevlar fabrics using titanium blade-like projectiles to evaluate their impact resistances in aero-engine containment applications. Energy absorption characteristics, deformation features, and damage patterns are analyzed. Impact test results show that the STF made of 100 nm SiO2 improved the anti-impact performance of the Kevlar fabric and increased the energy absorption up to 56.6%, whereas it decreased in the treatment by STFs made of 650 nm SiO2. The different trends of the two suspension systems are attributed to the specific value of shear rate with critical shear rate. The maximum deformation is estimated and compared with the pyramid deformation formed in the fabric. The STF–Kevlar fabrics under impact are more compact and act as an integrated structure compared with the loose structure of neat Kevlar fabrics. Owing to the increased interyarn friction action after the STF treatment, less yarn slippage occurred during the impact. For fabrics treated with the a-system STF, primary yarns were stretched and pulled out from the overlap structure of the woven fabric, forming perpendicular strip areas with failure modes involving unraveled yarns. The perforated damage of the b-system-STF-treated fabrics is concentrated at the area directly in contact with the blade projectile, in which a small amount of yarns fractured and pulled out.