Study of the effect of concentration and grain size of nano-silica on the impact energy absorption of impregnated glass fibers

This study investigates the low-velocity impact performance of glass fabrics impregnated with shear thickening fluids, with a focus on the effects of silica particle size and concentration. STFs were synthesized using four different average particle sizes (16 nm, 15–35 nm, 55–75 nm, and 200 nm) at three weight concentrations (40 wt.%, 52.5 wt.%, and 65 wt.%). The resulting liquids were applied to four-layer woven glass fabrics to produce twelve composite samples. All specimens were subjected to dynamic impact testing at 40 J of energy using a 20-mm hemispherical impactor. The results showed that both particle size and concentration had a significant impact on the absorption of impact energy. Sample C65, containing 55–75 nm particles at 65% w/w, showed the highest improvement in absorbed energy with a 98.1% increase over the clean weave. Interestingly, the energy absorption behavior varied with concentration for particles of varied sizes. While energy absorption improved with increasing concentration for 16 nm particles, a decrease was observed for particles ranging from 15 to 35 nm in diameter. These results highlight the critical role of optimizing STF composition, particularly nanoparticle size and concentration in enhancing the impact resistance of flexible composite fabrics. Building on this, the present work offers a systematic experimental framework that contributes to the development of advanced STF-enhanced materials for flexible impact protection applications. © The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2025.