A unified picture for creep and shear startup flows in Soft Glassy Materials
Thibaut Divoux
Laboratoire de Physique, ENS Lyon

May 12, 2022, 1 p.m.
This seminar is held online.
Online: https://tinyurl.com/nanoSeminar-GA

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Yield stress fluids (YSFs) encompass a wide variety of amorphous soft materials, from soft glasses like shaving creams and mayonnaise to colloidal gels such as fresh cement pastes and silica or alumina precursors for catalyst supports. YSFs display a dual nature highlighted by the existence of a critical stress σ_y such that YSFs are solid for stresses σ imposed below σ_y , whereas they flow like liquids for σ > σ_y . Under an applied shear rate, the solid-to-liquid transition is associated with a complex spatiotemporal scenario that depends on the microscopic details of the system, on the boundary conditions, and on the system size. Still, the general phenomenology reported in the literature boils down to a simple sequence that can be divided into a short-time response characterized by the so-called “stress overshoot,” followed by stress relaxation towards a steady state. Such relaxation can be either (1) long-lasting, which usually involves the growth of a shear band that can be only transient or that may persist at steady state or (2) abrupt, in which case the solid-to-liquid transition resembles the failure of a brittle material, involving avalanches. In this talk, we will use a continuum model based on a spatially resolved fluidity approach to rationalize the complete scenario associated with the shear-induced yielding of YSFs.


Brief CV

Thibaut is a tenured research associate at CNRS with an appointment at the Physics Laboratory at ENS Lyon (Lyon, France) since March 2020. I was first appointed at the Centre de Recherche Paul Pascal (2012-1016) before being transferred to the CNRS-MIT Lab in the Department of Civil and Environmental Engineering at MIT (2016-2020). He received his BA (2004) and Msc (2006) degrees from the Ecole Normale Supérieure in Paris and his Ph.D. (2009) from the Physics Laboratory of the Ecole Normale Supérieure in Lyon (France). He succeeded (top 2%) in the prestigious French competitive exam known as the Agrégation in physics and was a lecturer for 5 years at ENS Lyon. He joined the CNRS in 2012, where he has built an independent experimental activity in the field of Soft Matter. His current research interests include colloidal and biopolymer gels, the microscale scenario underpinning the yielding of amorphous soft solids, and the multiscale characterization of soft solids via nanoindentation.



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A unified picture for creep and shear startup flows in Soft Glassy Materials
Thibaut Divoux
Laboratoire de Physique, ENS Lyon

May 12, 2022, 1 p.m.
This seminar is held online.
Online: https://tinyurl.com/nanoSeminar-GA

Google Scholar Linkedin


Yield stress fluids (YSFs) encompass a wide variety of amorphous soft materials, from soft glasses like shaving creams and mayonnaise to colloidal gels such as fresh cement pastes and silica or alumina precursors for catalyst supports. YSFs display a dual nature highlighted by the existence of a critical stress σ_y such that YSFs are solid for stresses σ imposed below σ_y , whereas they flow like liquids for σ > σ_y . Under an applied shear rate, the solid-to-liquid transition is associated with a complex spatiotemporal scenario that depends on the microscopic details of the system, on the boundary conditions, and on the system size. Still, the general phenomenology reported in the literature boils down to a simple sequence that can be divided into a short-time response characterized by the so-called “stress overshoot,” followed by stress relaxation towards a steady state. Such relaxation can be either (1) long-lasting, which usually involves the growth of a shear band that can be only transient or that may persist at steady state or (2) abrupt, in which case the solid-to-liquid transition resembles the failure of a brittle material, involving avalanches. In this talk, we will use a continuum model based on a spatially resolved fluidity approach to rationalize the complete scenario associated with the shear-induced yielding of YSFs.


Brief CV

Thibaut is a tenured research associate at CNRS with an appointment at the Physics Laboratory at ENS Lyon (Lyon, France) since March 2020. I was first appointed at the Centre de Recherche Paul Pascal (2012-1016) before being transferred to the CNRS-MIT Lab in the Department of Civil and Environmental Engineering at MIT (2016-2020). He received his BA (2004) and Msc (2006) degrees from the Ecole Normale Supérieure in Paris and his Ph.D. (2009) from the Physics Laboratory of the Ecole Normale Supérieure in Lyon (France). He succeeded (top 2%) in the prestigious French competitive exam known as the Agrégation in physics and was a lecturer for 5 years at ENS Lyon. He joined the CNRS in 2012, where he has built an independent experimental activity in the field of Soft Matter. His current research interests include colloidal and biopolymer gels, the microscale scenario underpinning the yielding of amorphous soft solids, and the multiscale characterization of soft solids via nanoindentation.



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