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DY: Fachverband Dynamik und Statistische Physik
DY 22: Granular Matter/ Contact Dynamics
DY 22.11: Vortrag
Mittwoch, 16. März 2011, 16:45–17:00, HÜL 186
Nanoindentation on sedimented colloids — •Marcel Roth1, Carsten Schilde2, Philipp Lellig1, Arno Kwade2, and Günter K. Auernhammer1 — 1MPI for Polymer Research, Mainz, Germany — 2Institute for Particle Technology, TU Braunschweig, Germany
The mechanical properties of colloidal and granular matter depend on the mutual interplay of inter-particle forces as well as structural and material properties. While attractive forces are directly connected to the mechanical strength of the sample, particle rearrangements under gravity or external loads are critically affected by the particle density and surface properties.
In the present paper we investigate the mechanical properties of dense amorphous and semi-crystalline colloidal sediments made from monodisperse PMMA particles (diameter: 1.6 µ m) via nanoindentation in combination with confocal microscopy. In doing so the bare mechanical data are complemented by three-dimensional trajectories of all particles during the indentation. Reorganization processes are identified and the average deformation field is calculated. Although the indent extension is only ten times larger than the particle size the deformation field of the amorphous structure is in reasonable agreement with the predictions from the continuum theory. In semi-crystalline assemblies heterogeneities and generation of dislocation defects are observed. As a consequence measured force-depth curves can be quantitatively analyzed with the theory of Oliver and Pharr to extract average values for hardness and effective elastic modulus characteristic for the tested structure.