Structured fluids do not obey a simple linear relationship
between applied stress and flow (Newtonian fluid behavior)
as shown in Figure 1 for suspensions of latex particles with
increasing volume fraction in water.
Nearly all these materials have a viscosity that drops at higher
rates of shear velocity resp, stress. This is the phenomenon of
shear thinning which becomes progressively larger as the
volume concentration of solid particles increases. At high
concentration of solid content, the low shear rate viscosity
region disappears completely, the material is yielding.
Some materials show after the shear thinning region with
increasing rate or stress, an increase of the viscosity, usually
due to structure rearrangements as a result of the applied
shear. This is referred to as flow induced shear thickening.