Rate-Dependent Behavior Of Aramid Fibers Coated With Shear Thickening Fluids

Due to their high strength and stiffness and in particular toughness, aramid fabrics have been used in bulletproof applications. Recently, aramid fabrics have been coated with shear thickening fluid (STF), demonstrating more enhanced bulletproof and mechanical properties. In our previous study, the shear thickening behavior of STF-coated aramid fabrics were characterized using picture-frame and bias extension tests, revealing that the STF effect was in fact observed over yarn crossovers at mesoscale. This observation can explain improved bulletproof and mechanical properties due to STF, however it is still unclear at microscale level, i.e., whether STF-coated single aramid fiber inside yarns can contribute to the STF effect of STF-coated aramid fabrics. This study aimed to investigate the rate-dependent behavior of STF-coated single aramid fiber inside aramid yarns. A STF was prepared by making the colloidal suspension of silica nano particles (about 84 nm in size) in poly (ethylene glycol). The STF was then coated onto a single aramid fiber and aramid yarns. A special test rig was using 3D printers that can hold the single aramid fiber passing through the aramid yarns, in which it contacts with many other aramid fibers. The test rig was installed into a universal tensile machine, measuring the force that the single fiber experienced.