LARGE AMPLITUDE OSCILLATORY SHEAR RHEOLOGY OF  SHEAR THICKENING FLUIDS FOR PERSONAL BODY ARMOR

Manojkumar Chellamuthu and Gale A. Holmes

Polymers Divison, MSEL, NIST Gaithersburg, MD, 20899

Shear Thickening Fluids (STF) exhibit an increase in viscosity under high rates of deformation. More recently the dampening properties of Shear Thickening Fluids (STF) has been exploited for use in several applications such as soft body armor, sports equipment and medical devices. These applications have motivated research to fundamentally understand the non-linear rheological response of STF. We have performed large amplitude oscillatory shear (LAOS) measurements on several well studied, model shear thickening fluids to probe the rich material non-linearities. The nonlinear regime analysis as developed by Ewoldt et al. (Ewoldt, R.H. et al. J. Rheol. 2008, 52, (6), 1427-1458) is used to quantify the instantaneous viscosities and elastic moduli throughout an oscillatory shear deformation cycle. The generated Lissajous-Bowditch Figures are compared with shear thickening under steady shear. The fundamental understanding of the non-linear stress response proves to be useful in further investigations of STF under dynamic deformations.