Shear thickening fluid (STF) occurs in dispersions of highly condensed colloid particles and is categorized as a non-Newtonian fluid whose viscosity increases under shear loading which makes them beneficial in protective and impact resistance applications. The aim of this study is to synthesis two different STFs and characterize their microstructural properties to provide a data base for comparing the final macrobehavior of the two fluids under mechanical testing. Therefore, fumed silica and polyethylene glycol STF and starch with water STF-based dispersions were prepared. The particle size, zeta potential, SEM micrographs, and rheological analysis were performed for each type of STF. The effect of filler concentration was observed by using 10–30 weight% filling material. The rheological properties of STFs show higher viscosity measurements at same shear rates for starch/water STF than silica/PEG with maximum viscosity reaching 523.6 Pa s and 178.9 Pa s, respectively. Larger starch particle size over silica recorded as 303.7 nm and 16.49 nm, respectively, and zeta potential analysis recorded particle electrostatic charges as 22.6 mV and 12.8 mV, respectively, leading to more dispersion stability and obvious thickening effect at higher particle concentration leading to greater jump in viscosity at sudden shear rate. The results indicate the capability of trying more protective applications with more flexibility and less thickness when STF is implemented and a good database for the fluids to choose from according to their behavior.

This research aims to participate in producing body shield that can overcome pervious drawbacks using behaviour of shear thickening fluid. Initially, the rheological behaviour of silica-polyethylene glycol shear thickening fluid is examined at different concentrations. Then, ballistic fabric samples are impregnated into silica-polyethylene glycol shear thickening fluid at various concentrations of silica and tested using gas gun simulating real ballistic threat. After that, the impact of rubbery hot water pack filled with around 66.67 wt% starch in water is tested using gas gun. Results showed as the concentration of silica increases, the indentation depth in the impregnated fabric decreases which may result in improving performance of ballistic fabric to 12.5 % in case of using 60 wt% silica, 7.35 % in case of using 30 wt% silica and 3.31 % in case of using 7.5 wt% silica with respect to plain sample. As it showed that no indentation depth is formed in modelling clay when rubbery hot water pack filled with around 66.67 wt% starch in water is tested using gas gun causing improvement percentage to be 100% compared to plain sample of Twaron (CT 714).

The novelty of this research is the synthesis and comparison of a soft liquid composite shield made from two different Shear Thickening Fluids (STFs) / Polyamide fabric composite material and choosing the best one for impact resistance based on characterization and performance. The STFs microstructural properties are characterized, and STF / Polyamide composites are prepared while testing their ballistic resistance using an air gun with intermediate velocities (<100 m/s) for energy absorption. Materials used for this purpose are fumed silica with polyethylene glycol (PEG) STF and starch with water STF based dispersions. The results confirmed the superior performance of STF to absorb energy, especially for starch and water system. The rheological properties for starch/water STF showed higher viscosity than silica/PEG reaching 523.6 Pa.s and 178.9 Pa.s respectively. Other characterization tests proved the superior performance of starch with water STF leading to more dispersion stability and obvious thickening effect at higher particle concentration leading to a greater jump in viscosity at sudden shear rate. The highest concentration of silica/PEG STF/fabric showed improvement in indentation depth by 26.9%, while the starch/water STF by 43.6%. These results show the viability of the STF/Polyamide composite material if integrated for personal protection applications.