Particle Size Effects and Gradient Hybrid Reinforcement Mechanisms of Shear Thickening Fluid in Aramid Fabrics

ABSTRACT To improve the ballistic performance of aramid fabrics, this study prepared three types of shear thickening fluid (STF) using silica particles of different sizes and polyethylene glycol. It examines the effect of STF treatment on the ballistic behavior of the fabrics, with a focus on particle size and its influence on the strengthening mechanism. Composite panels with two or three components were made by stacking fabrics treated with STFs of different particle sizes, using hot‐press lamination and a hybrid layout method. Ballistic tests were carried out with a high‐speed light‐gas gun to compare neat aramid panels, STF‐treated panels, and hybrid composite panels. The results show that hot‐press lamination retains the shear‐thickening behavior of the STF. All STF‐treated panels had better ballistic resistance than the neat fabric. They show clear increases in ballistic limit velocity (V 50 ), energy absorption, and specific energy absorption (SEA). Particle size plays a key role in the STF effect. Smaller particles can enter the gaps between yarns more easily, increasing inter‐yarn friction and energy dissipation. Larger particles tend to cluster and produce a stronger shear‐thickening response. The graded composite panel, with STF particle sizes arranged from small to large, shows the best overall performance. Its V 50 increases by about 70.47%, and its SEA improves by 204.2% compared with a neat fabric panel with the same areal density.