Mechanical properties and cushioning mechanism of shear thickening fluid

Shear thickening fluid (STF) is one type of dispersed system with rapidly changing rheological properties under an impulse load. The apparent viscosity of such a suspension system changes dramatically under high-speed impact, and the system can even change from suspension to quasi-solid. Once the load is removed, the STF will quickly return to its original state. In this paper, a mechanical model based on a particle-jammed model and added mass was proposed by calculating the acceleration response of the impact bar, and the local hardening phenomenon of STF in the low-speed impact test was interpreted. Then with the low-speed impact test, the rheological properties of STF in the cushioning process were recorded by a high-speed camera. Meanwhile, a comparison was made with the cushioning efficiency of AV-200, a closed-cell foam material, by using the force-displacement curve. Finally, based on the constitutive relation of STF and by using the fluid-solid coupling method in the FEM, the low-speed impact test of STF was analyzed to obtain more comprehensive dynamic characteristics. The acceleration response obtained in the test was consistent with the theoretical results, which further verified the rationality and effectiveness of the theoretical model. Compared with AV-200, STF has a cushioning efficiency of 50 %–60 %, and its cushioning performance was superior to AV-200. Starting with the rheological cloud map of STF and the acceleration response of the impact bar by the numerical model, a comparison was made with the results of low-speed impact test, and a good agreement is observed.