Constitutive modeling of shear thickening fluid using continuum mechanics

Abstract

Shear thickening fluid (STF) exhibits intelligent rheological properties associated with its strain rates, demonstrating excellent viscosity thickening and thinning effects. These properties effectively enhance the performance of STF utilized in impact protection. However, the thickening effect has posed significant difficulties in the theoretical study of STF, resulting in a lack of specific constitutive models and experimental verification. To address this issue, we perform systematic rheological tests across a wide range of loading rates, thoroughly exploring the intelligent rheological responses of STF. Based on the mechanical behavior, we utilize an innovative approach for STF to develop a novel shear-thickening constitutive model within a framework of continuum mechanics, contributing to its theoretical understanding and providing guidance for applications. Given the nonlinearity of the constitutive equations, we present a corresponding numerical implementation approach to efficiently obtain solutions, and subsequently conduct parameter identification using this approach. The significant overlap between the experimental results and model predictions indicates that the new model accurately captures the intelligent rheological behaviors of STF. Furthermore, we design a series of simulations as anti-impact application scenarios of the STF-based composite, which activates a viscosity thickening effect to deliver strong resistance during high-speed impacts. Interestingly, unlike constant-viscosity materials, the STF-based composite exhibits a unique thinning effect and consumes very little energy during low-speed impacts. Consequently, when used as wearable equipment, it not only effectively weakens high-speed impacts, but also facilitates unrestricted movement during low-speed activities. These findings offer valuable guidance for the designs and applications of STF-based products.