Tensile Deformation and Failure of Thin Films of Aging Laponite Suspension

TL;DR

This study investigates how aging affects the tensile deformation, failure, and brittleness of thin films of laponite suspension, revealing age-dependent mechanical properties and a superposition principle for relaxation time and elastic modulus.

Contribution

It introduces a detailed analysis of aging effects on visco-elastic thin films of laponite, including a novel time-aging time superposition method for mechanical characterization.

Findings

Force and energy dependence on velocity and thickness is intermediate between Newtonian and yield stress fluids.

Aging increases brittleness, decreasing strain at break and dissipated energy.

Time-aging time superposition allows independent estimation of relaxation time and elastic modulus.

Abstract

In this paper we study deformation, failure and breakage of visco-elastic thin films of aging laponite suspension under tensile deformation field. Aqueous suspension of laponite is known to undergo waiting time dependent evolution of its micro-structure, also known as aging, which is accompanied by an increase in the elastic modulus and relaxation time. In the velocity controlled tensile deformation experiments, we observed that the dependence of force and dissipated energy on velocity and initial thickness of the film is intermediate to a Newtonian fluid and a yield stress fluid. For a fixed waiting time, strain at break and dissipated energy increased with velocity, but decreased with initial thickness. With increase in age, strain at break and dissipated energy showed a decrease suggesting enhanced brittle behavior with increase in waiting time, which may be caused by restricted relaxation modes due to aging. In a force controlled mode, decrease in strain at failure at higher age also suggested enhanced brittleness with increase in waiting time. Remarkably, the constant force tensile deformation data up to the point of failure showed experimental time- aging time superposition that gave an independent estimation of relaxation time and elastic modulus dependence on age.