Time-aging time-stress superposition in soft glass under tensile deformation field

TL;DR

This study investigates the tensile deformation and aging behavior of Laponite suspensions under stress, revealing a superposition principle that links short-term and long-term rheological responses.

Contribution

It introduces an aging time-process time-normal stress superposition principle for predicting long-term behavior from short-term tests in soft glassy materials.

Findings

Aging rate decreases with applied normal stress.

At high stress, aging halts and plastic deformation occurs.

Superposition principle enables prediction of long-term rheology.

Abstract

We have studied the tensile deformation behaviour of thin films of aging aqueous suspension of Laponite, a model soft glassy material, when subjected to a creep flow field generated by a constant engineering normal stress. Aqueous suspension of Laponite demonstrates aging behaviour wherein it undergoes time dependent enhancement of its elastic modulus as well as its characteristic relaxation time. However, under application of the normal stress, the rate of aging decreases and in the limit of high stress, the aging stops with the suspension now undergoing a plastic deformation. Overall, it is observed that the aging that occurs over short creep times at small normal stresses is same as the aging that occurs over long creep times at large normal stresses. This observation allows us to suggest an aging time - process time - normal stress superposition principle, which can predict rheological behaviour at longer times by carrying out short time tests.