Impact protection performance of Kevlar fabric composites impregnated with modified multiphase shear thickening fluids

Shear thickening fluids (STFs) exhibit significant potential for impact protection owing to their unique rheological properties. In this study, a SiO 2 /PEG200 dispersion system was used to formulate multi-phase STFs with a mass fraction gradient. STFs were further modified with additives, such as nanocellulose (CNC) and nano-silicon carbide (SiC), to create modified multi-phase shear thickening fluids (MSTFs). Kevlar fiber cloth was impregnated with MSTFs to prepare MSTF-Kevlar composites. Scanning electron microscopy and rheological analyses at normal temperature revealed that 58wt% was identified as the critical mass fraction for the shear-thickening effect. The modification of high-mass fraction SiO 2 and CNC significantly enhanced the shear thickening and energy absorption properties, while SiC mainly influenced the structure and stiffness of STF clusters. The variable-temperature rheology analysis revealed that additive modification effectively enhanced the temperature adaptability of STFs. In single-yarn and multi-yarn pulling experiments, the shear thinning behavior of MSTFs at low shear rates negatively affected the tensile strength and anti-slip properties of the yarns. However, under high shear rate conditions in drop-weight impact tests, MSTFs significantly improved the ultimate impact resistance and energy absorption capacity of the fiber cloth. Among the modified materials, CNC provided the best protective performance, while SiC enhanced the stability of material protection. Numerical simulations based on LS-DYNA further confirmed the energy absorption behavior observed in the drop-weight impact experiments. These findings provide both theoretical and experimental guidance for developing MSTF-Kevlar fiber cloth composites for impact protection applications.