A comparison of the ballistic performance of shear thickening fluids based on particle strength and volume fraction

• Analytical scaling techniques are used to model the penetration events.
• Evidence of dynamic material strength is shown in several of the suspensions.
• Ballistic resistance is shown to be strongly influenced by particle strength.
• Particle strength is shown to only become a factor at elevated volume fractions.
• Strength effects are shown to diminish significantly at higher impact velocities.

The ballistic response of suspensions of solid particles (cornstarch, silicon carbide, and silicon dioxide) in a liquid (ethylene glycol) is experimentally investigated. Some of the suspensions are at sufficient volume fraction to exhibit shear-thickening behaviour, while the others are Newtonian or mildly shear-thinning. The response of neat (liquid) ethylene glycol is also studied. Capsules containing the suspensions are impacted with a chisel-nosed fragment-simulating projectiles at velocities between 200 and 700 m/s. The residual projectile velocity upon exit from the capsule is measured via direct videography. The results are analysed using a number of different energy-based and momentum-based penetration models. A momentum-based model that normalizes the effect of the density of the suspension is seen to perform the best in terms of collapsing the results onto a single curve for the liquid and non-shear thickening suspensions. Only shear thickening suspensions with particles having sufficient strength (SiO2 and SiC) show significant deviation from hydrodynamic-dominated response, resulting in significant velocity decrements in the projectile attributable to the shear strength of the suspensions. These shear strength effects diminish as the projectile velocity increases, suggesting that the strength of the solid material in the interparticle contacts is overcome by the impact-generated stresses.