Elastically driven, intermittent microscopic dynamics in aging soft solids
| Quand ? |
Le 12/07/2016, de 10:45 à 12:00 |
|---|---|
| Où ? | Centre Blaise Pascal |
| Participants |
Mehdi Bouzid |
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Colloidal gels belong to the class of amorphous systems, they are disordered elastic solids that can form at very low volume fraction, via aggregation into a rich variety of networks, with interaction strengths comparable to the thermal energy. Such soft solids tend to undergo a progressive aging over time, due to microscopic ruptures and rearrangements of their structure, with dramatic impact on the material properties. Contrasting behaviors have been observed in experiments, which detect in similar materials a slow, continuous evolution or instead sudden, fast rearrangements. We have used numerical simulations of a minimal model and analyzed the cooperative dynamics emerging from the mesoscale organization of the network. Our computational study unravels that the fast, sudden rearrangements are the signature of large enthalpic stresses frozen-in, during solidification, in the microscopic structure of the material. In these conditions, exceedingly long time is required to relax stresses through thermal fluctuations and the microscopic ruptures and rearrangements underlying the aging are dominated by the elasticity stored in the material structure, which produces intermittent and strongly correlated dynamics. The processes unraveled here are relevant to a wide variety of soft materials and crucial to their mechanical performance.