Levich Institute Seminar Announcement, 05/05/2015
Steinman Hall, Room #312
(Chemical Engineering Conference Room)
Dr. Thibaut Divoux
CNRS Centre de Reserche Paul Pascal
"Yogurts Under Stress"
Biomaterials such as protein or polysaccharide gels are known to behave qualitatively as soft solids and to rupture under an external load. Combining optical and ultrasonic imaging to shear rheology we show that the failure scenario of a protein gel is reminiscent of brittle solids: after a primary creep regime characterized by a power-law behavior whose exponent is fully accounted for by linear viscoelasticity, fractures nucleate and grow logarithmically perpendicularly to shear, up to the sudden rupture of the gel. A single equation accounting for those two successive processes nicely captures the full rheological response. The failure time follows a decreasing power law with the applied shear stress, similar to the Basquin law of fatigue for solids. These results are in excellent agreement with recent fiber-bundle models that include damage accumulation on elastic fibers and exemplify protein gels as model, brittle-like soft solids.
BRIEF ACADEMIC/EMPLOYMENT HISTORY
RECENT RESEARCH INTERESTS
My research interests focus on the mechanical properties of soft glassy materials (SGM). Combining rheology and local techniques such as velocimetry, diffusion light scattering or particle tracking, I try to obtain simple pictures associated to the yielding/rupture of these materials. One of my goals is to provide a local scenario to the early response in creep experiments, in amorphous soft materials such as colloidal gels and model biopolymer gels. For the latter type of materials, deformation goes hand in hand with the release of solvent -also called syneresis- that I am currently trying to quantify thanks to original techniques such as interferometry and rheology under controlled normal force.