Regensburg 2013 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 53: Topical Session: Fundamentals of Fracture - Novel Experimental Techniques II
MM 53.5: Vortrag
Donnerstag, 14. März 2013, 12:45–13:00, H4
Plasticity and fracture in drying colloidal films — •Lucas Goehring1, William J. Clegg2, and Alexander F. Routh3,4 — 1MPI Dynamics and Self-Organization, Göttingen, Germany — 2Department of Materials Science and Metallurgy, University of Cambridge, UK — 3Department of Chemical Engineering and Biotechnology, University of Cambridge, UK — 4BP Institute for Multiphase Flow, University of Cambridge, UK
Cracks in drying colloidal dispersions are typically modelled by elastic fracture mechanics, which assumes that all strains are linear, elastic, and reversible. We tested this assumption in films of a hard latex, by intermittently blocking evaporation over a drying film, thereby relieving the film stress. Here we show that although the deformation around a crack tip has some features of brittle fracture, only 20-30% of the crack opening is relieved when it is unloaded. Atomic force micrographs of crack tips also show evidence of plastic deformation, such as micro-cracks and particle rearrangement. Finally, we present a simple scaling argument showing that the yield stress of a drying colloidal film is generally comparable to its maximum capillary pressure, and thus that the plastic strain around a crack will normally be significant. This also suggests that a film's fracture toughness may be increased by decreasing the inter-particle adhesion.