Mechanics of fluid-filled closed-cell structures: Theory, simulation, and experiment

• A novel analytical model for STF-filled structures is developed. • Fluid–structure interaction in closed-cell spheres and tubes is examined • Compressive and bending deformation are analyzed for spheres and tubes, respectively. • The proposed analytical model accounts for the effects of geometry, strain rate, and STF. • STF-filled structures demonstrate superior load-bearing capacity over hollow ones. This study presents a comprehensive investigation into the integration of shear thickening fluid (STF) with closed-cell structures, specifically focusing on sphere-based and tube-based configurations, to develop advanced materials for impact protection applications. A multi-method approach, combining analytical modeling, finite element simulations, and experimental testing, was employed to assess the compressive and bending behaviors of STF-filled structures. Key factors influencing these behaviors, including geometric parameters, loading rates, and the properties of the STF filler, were systematically analyzed. A novel governing equation was developed to predict energy absorption responses, which was validated against both experimental and numerical data. The validated analytical model effectively captures the key factors of geometry, strain rate sensitivity, and STF filling, providing a reliable and effective framework for the design and optimization of STF-filled structures. Experimental results demonstrated that cornstarch-based STF-filled structures outperformed their hollow counterparts in terms of load-bearing capacity. Additionally, the study highlights the beneficial role of entrapped air within hollow structures, which enhances energy absorption across varying loading rates. Furthermore, cornstarch-based STF-filled closed structures exhibited markedly superior load-bearing capacity compared to hollow structures, positioning them as highly promising candidates for applications in low-speed protective equipment, such as footwear, protective shoe soles, as well as other devices requiring effective energy absorption under low loading rates.