Issue 39, 2012

Shear mediated elongational flow and yielding in soft glassy materials

Abstract

In this work, we study the deformation behavior of thin films of various soft glassy materials that are simultaneously subjected to two creep flow fields, rotational shear flow by applying torque and elongational flow by applying normal force. The generic behavior under the combined fields is investigated in different soft glassy materials with diverse microstructures such as: hair gel, emulsion paint, shaving foam and clay suspension. Increase in the strength of one stress component while keeping the other constant not only leads to an expected enhanced deformation in its own direction, but also greater strain in the other direction. The Herschel–Bulkley model is observed to explain this behavior qualitatively. The elongational flow induced in the materials eventually causes failure in the same. Interestingly time to failure is observed to be strongly dependent not just on the normal force but also on the applied rotational shear stress. We believe that the presence of a three dimensional jammed structure, in which an overall unjamming can be induced by applying stress having sufficient magnitude irrespective of the direction, leads to the observed behavior. In addition, we observe self-similarity in the elongational as well as rotational strain–time curves corresponding to various combinations of both the fields. This observation suggests a mere shift in the time-scales involved keeping the path followed in the process unchanged. A phase diagram is also constructed for various soft glassy materials by determining different combinations of orthogonal stresses beyond which materials yield. The estimated yield stress in the limit of flow dominated by the applied tensile force on the top plate demonstrates scatter, which might be originating from fingering instability. Except this deviation, yielding is observed when the invariant of the stress tensor exceeds the yield stress, validating the Von Mises criterion.

Graphical abstract: Shear mediated elongational flow and yielding in soft glassy materials

Article information

Article type
Paper
Submitted
13 Jun 2012
Accepted
24 Jul 2012
First published
20 Aug 2012

Soft Matter, 2012,8, 10107-10114

Shear mediated elongational flow and yielding in soft glassy materials

A. Shaukat, M. Kaushal, A. Sharma and Y. M. Joshi, Soft Matter, 2012, 8, 10107 DOI: 10.1039/C2SM26371H

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements