Accueil > Séminaires > Précédents séminaires > Internal stresses, cooperative processes and yielding in poorly connected soft solids

Internal stresses, cooperative processes and yielding in poorly connected soft solids

Emanuela Del GadoDepartment of Physics, Georgetown University, Washington D.C.

Colloidal gel networks are disordered elastic solids that can form even in extremely dilute particle suspensions. With interaction strengths comparable to the thermal energy, their stress-bearing network can locally restructure via breaking and reforming interparticle bonds. This allows for yielding, self-healing, and adaptive mechanics under deformation. Designing such features requires controlling stress transmission through the complex structure of the gel and this is challenging because the link between local restructuring and overall response of the network is still missing.We have used numerical simulations of a minimal model and analyzed the cooperative dynamics emerging from the mesoscale organization of the network and the mechanical response of the material to shear deformation. Our results indicate that consequences of local bond breaking propagate along the gel network over distances larger than the average mesh size. Under deformation, our space-resolved analysis of strains and stresses unravel how a strong localization of tensile stresses may trigger the yielding of the gel and eventually damage its structure. This strain-induced reorganization of the gel and the flow inhomogeneities developed upon yielding are closely reminiscent of experimental observations and strongly affected by the shear rate.
Our analysis of the gel restructuring at rest and under deformation aims at disentangling the role of thermal fluctuations and of relaxation of internal stresses in the complex dynamics detected in colloidal gels in various exper iments, where faster than exponential decays of time correlations have been detected, and in the mechanical behaviour of other poorly connected soft solids.