Paper Number
VP91
Session
Pre-recorded Flash Presentations (virtual)
Title
Yielding of model viscoplastic interfaces in shear and compression: Landmark observations and constitutive modelling
Presentation Date and Time
All Week (Asynchronous) Any Time
Track / Room
Pre-recorded Presentation / Virtual
Authors
- Alicke, Alexandra (ETH Zurich, Department of Materials)
- Tervoort, Theo (ETH Zurich, Department of Materials)
- Vermant, Jan (ETH Zurich, Materials Departement)
Author and Affiliation Lines
Alexandra Alicke, Theo Tervoort and Jan Vermant
Department of Materials, ETH Zurich, Zurich, Switzerland
Speaker / Presenter
Alicke, Alexandra
Keywords
experimental methods; colloids; interfacial rheology; non-Newtonian fluids; rheology methods
Text of Abstract
Colloidal particles are widely employed to provide Pickering stability to high interface systems. Their colloidal nature makes them prone to irreversibly adsorb at interfaces, and the flexibility to tune interactions makes them ideal candidates as model systems to understand the behavior of more complex interfaces. Typically, they are used to fully cover the surface of bubbles and droplets, though it has been recently shown[1] that the existence of an interfacial yield stress at sub-monolayer coverages suffices to resist bubble dissolution (and the main driving force for Ostwald-ripening). Analogously to bulk materials, the viscoplastic nature can be achieved by different material design routes; specific to interfaces as an extra handle to tune interactions are capillary forces that arise from contact line variations due to e.g. shape or roughness. However, differently than their 3D counterparts, these 2D materials have the advantage of being compressible, which means that we can experimentally interrogate the full tensorial nature of yielding for constitutive modelling. Here, we used both i) flocculated particle interfaces that behave as 2D-gels and ii) dense particle interfaces close to monolayer coverage that resemble glassy systems. By using custom-built interfacial rheology set ups we investigated the transition from linear to nonlinear behavior in both shear and compressional/dilatational deformation modes. We report the main features observed during yielding, for the first time in isotropic compression, and discuss these in relation to designing complex interfaces. In addition, we also propose and verify a simple constitutive model to account for viscoplasticity that can potentially give important insights also for bulk materials.
[1] Beltramo et al, PNAS (2017)