Onset of Non-Linearity and Yield Strain of a Model Soft Solid


Vijesh A. Tanna


Vijesh A. Tanna Casey Wetzel H. Henning Winter

Author Affiliation: 

Vijesh A. Tanna (UMass Polymer Science and Engineering) Casey Wetzel (UMass Chemical Engineering) H. Henning Winter (UMass Chemical Engineering, Polymer Science and Engineering)


For soft solids with their low modulus, small stress already results in large strain, which may cause non-linearity and yielding. These competing effects were studied on a clay/polybutadiene (clay/sPB) composite, which is a soft physical gel. Structural changes were introduced by oscillatory shear at large amplitude (LAOS). LAOS beyond a critical limit reduced the internal connectivity. This softened the already soft solid even further, thereby moving it closer to its physical gel point. For clay/sPB, the shear induced changes were irreversible so that they could get probed using small amplitude shear (SAOS) frequency sweeps. Sequences of SAOS-LAOS-SAOS (SLS) where repeated with increasing LAOS amplitude and increasing duration. The flow-induced structural changes in the soft solid were attributed to yielding, which began to occur at about the same stress/strain values as found in traditional SAOS to LAOS (StL) stress amplitude sweeps. The onset of non-linearity and yielding seems to be strain controlled since the characteristic strain amplitude is independent of frequency. Not so for the characteristic stress amplitude