Dissipative mechanisms at frictional interfaces

In soft materials (rubber, glassy polymers, hydrogels, decorated particles, etc.), the classical laws of friction do not apply. In fact, friction combines dissipative mechanisms of various origins: molecular adsorption mechanisms at the friction interface, viscoelastic dissipation in volume (rubber), to which are added poroelastic dissipation (hydrogels) or losses due to covalent bond breakage (wear). This complexity is found in the rheology of particle suspensions, where friction between particles is coupled with viscous dissipation in the continuous phase. The approach developed at SIMM aims to isolate the contribution to friction of the various dissipative mechanisms and to measure their molecular parameters.

Thus, in concentrated suspensions where interparticle interactions control adhesion and friction at the elementary scale, techniques for measuring dissipation at the two-particle scale are being developed in the laboratory, and the results are compared with macroscopic rheology measurements.
On extended interfaces, we are developing new experimental techniques combining imaging (interferometry, fluorescence, etc.) and force/displacement measurements, or even stress/strain fields, to directly link molecular parameters, surface interactions, and macroscopic properties.

– Hydrogel friction: poroelasticity and molecular interactions
– Non-Newtonian rheology of liquids confined at the nanoscale
– Solid friction at the nanoscale in confined aqueous systems: an application to the rheology of construction materials
– Charge transport at solid interfaces and triboelectrification