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

Presenter: 

Vijesh A. Tanna

Authors: 

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)

Abstract: 

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