SMSD Seminar - Microscopic dynamics of sheared colloidal gels: plasticity, yielding and fractures

Thursday, October 03, 2019 at 4:00pm

Room 3-333

Dr. Stefano Aime, Harvard University

The failure of materials under load is widespread, occurring from geological scales, as in earthquakes, to biological and soft-matter systems, with huge implications to everyday life and material science. Despite consistent efforts in this field, failure is very often undesired and unpredicted: surprisingly, or maybe unsurprisingly, it turns out that what is so common in our daily experience is based on profound science that is not yet fully understood.

In this talk I will discuss experiments in which we investigate the microscopic signature of failure in a colloidal gel, a model network-forming system, by simultaneously measuring their mechanical response and microscopic dynamics. Experiments under a constant or oscillatory shear stress show that the delayed failure of the gel network is anticipated by qualitative and quantitative changes of the dynamics, from reversible particle displacements to a burst of irreversible plastic rearrangements. The same tools are applied to the study of hydraulic fractures, to extract the shape and size of the fracture process zone under different loading conditions.

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School of Engineering (SoE)

Department of Materials Science and Engineering (DMSE), Department of Mechanical Engineering
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