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Rheology of Suspension

Rheology is fundamentally concerned with the deformation of matter in both the solid and liquid state. Both single-phase materials and multiphase systems are investigated with regard to different parameters such as load and time behavior. Suspension rheology represents a subarea of this field. The flow properties depend on a variety of particulate properties such as shape, size, size distribution and interaction as well as the suspension matrix. In particular, with respect to shear rate dependence, suspensions exhibit extremely diverse flow properties such as apparent wall sliding. Another field of research, less studied for technical reasons, is extensional rheology (single-phase material and multiphase system), which is of great importance especially in plastics processing. At the Chair of Particle Process Engineering a wide range of different measuring systems is available for research in the field of rheology. Currently, the work is concentrated on the characterization of complex colloidal systems (suspensions) as well as extensional rheological investigations of polymer melts. Conclusions are to be drawn from this for the modeling of the various processes.

Current research areas

Suspension rheology in transparent slit dies via PIV
Modeling filament extension atomization for stretch rheological production of polymer powders for use in selective laser sintering

The development of new areas of application for selective laser sintering is closely linked to the production of new materials and is currently inhibited by the monoculture of polyamide 12. Filament extension atomization represents a promising manufacturing process for polymer powders of all types. Filament extension is a stretch rheological process in which, due to the physical properties of polymers, filaments are formed that break up into droplets with monodisperse size distribution. The experimental tests are supported by modeling using known tube models.

Moritz Neukötter

Development of an adaptive coaxial rheometer for use in the scientific characterization of fresh concrete with particle sizes of up to 5.5 mm

The currently common investigation methods for fresh concrete only allow a relative comparison of different concrete mixtures. Although rheological data are necessary especially today for the development of high-strength concretes, 3D-printable concretes or for simulations of concrete flow, they cannot be accessed by these methods. Therefore, the rheometer developed in this project should enable new possibilities for scientific concrete characterization. In addition to an adaptively designed rheometer surface, the flow field of fresh concrete can further be analyzed by means of Ultrasound Image Velocimetry (UIV).

Sebastian Pawelczyk

The University for the Information Society