Mechanical modeling of strain rate-dependent behavior of shear-stiffening gel

Shear stiffening gels (SSGs) exhibit the unique behavior of a rapid increase of modulus or viscosity with increasing strain rate. Because of this rate-dependent behavior, SSGs are used in shock-absorbing applications such as helmets and body armor. In this study, the constitutive relationship of SSGs was investigated by preparing an SSG and then performing various experiments for rheological characterization using a rheometer for low and medium shear rates, and a split Hopkinson pressure bar test for high shear rates. Then, using a stress and corresponding strain invariant, the stress and strain rate were plotted in a graph, from which a non-Newtonian relationship was established for the SSG. Finally, the impact behaviors of multi-layer structures made from the SSG were simulated, and the results were compared with experimental results, validating the constitutive relationship.