Shear thickening fluids for application in field responsive composite materials
Co-advised by Dr. Jack Gillespie
Concentrated near hard-sphere colloidal suspensions, or shear thickening fluids (STFs), have been shown to improve the ballistic protection of Kevlar (http://www.ccm.udel.edu/STF/index.html), the stab protection of fabrics  and have the potential to be incorporated in countless other applications such as the composite materials used for armored vehicles and protective sports equipment. As a field responsive material, STFs exhibit a reversible transition from a shear thinning to a shear thickening response with increasing applied shear stress . During simple steady shear the shear thickening response is known to be connected with flow-induced microstructural rearrangements comprised of density fluctuations of particles in the suspension (termed “hydroclusters”) .For all of these applications it is important to understand STFs under dynamic conditions. The goal of the present research is to define the dynamic response of a model STF and to gain an understanding for the associated microstructural rearrangements in order to fully appreciate the origins of the shear thickening phenomena during dynamic deformations.
A combination of rheometry techniques and small angle neutron scattering (SANS) methods are used to better understand the shear thickening phenomena. As a result, the intimate connection between a concentrated colloidal suspension’s microstructural rearrangements and the resulting mechanical properties of the bulk material will be realized. The subsequent microstructure-property relationship will aid in the development of a model for colloidal suspensions that can be used to predict STF responses ultimately resulting in the rational design of STF composite materials for specific applications.
 D. Kalman and N. J. Wagner (2009). “Microstructure of shear-thickening concentrated suspensions determined by flow-USANS”, Rheol Acta 48: 897-908.
 N. J. Wagner and J. F. Brady (2009). “Shear thickening in colloidal dispersions.” Physics Today 62(10): 27-32.