Shear History Extensional Rheology Experiment – II (SHERE-II)
Research Area: Complex Fluids
Expedition(s): 27-ongoing
Principal Investigator(s): ● Gareth H. McKinley, PhD, Massachusetts Institute of
Technology, Cambridge, Massachusetts
RESEARCH OBJECTIVES
The Shear History Extensional Rheology Experiment-II (SHERE-II) investigation involves a non-
Newtonian fluid that will undergo preshearing (rotation) for a specified period of time, followed
by stretching. This combination of shearing and extensional deformations is common in many
Earth-based polymer processing and manufacturing operations such as extrusion, blow-
molding, and fiber spinning. However, in order to accurately predict the flow behavior of
polymeric fluids under such deformation histories, an accurate knowledge of the extensional
viscosity of a polymer system and its variation with strain rate is critical and will be measured
during this experiment. The fundamental understanding and measurement of these complex
fluids is important for containerless processing, a
key operation for fabrication of parts, such as
adhesives or fillers, using elastomeric materials
on future exploration missions.
EARTH BENEFITS
A fundamental understanding and measurement
of the extensional rheology of complex fluids also
allows Earth-based manufacturing processes to
be controlled and improved. Ground-based work
using variants of the Filament Stretching
Rheometer includes studies of spinnability and
the investigations of cohesive and adhesive
instabilities that manifests themselves in adhesion
and tackiness of materials. It has led to the
development of a Resin-spinning technology that
allows the formation of ultra-fine elastic threads
analogous to spider-silks. Control of the fluid
shear history and extensional rheology of test fluid is essential to optimizing the ultimate web
properties. Extensional rheology is of critical importance in optimization of polymer processing
operations that involve complex flows, ie, flows that contain both shearing (rotation) and
elongation (stretching) components. Suspensions of particles in viscoelastic liquids are used in
many terrestrial processing operations: polymer melts with fillers, ceramic pastes, biomedical
materials, food, cosmetics, or detergents. The final properties of the suspensions are greatly
determined by the shape, concentration, and size of the filler. In particular, the fillers can range
from nanoscopic to microscopic characteristic dimensions, and this leads to very different types
of flow behaviors, filler/matrix interactions, and dynamics.
The SHERE main hardware (Rheometer,
Interface Box, Tool Box, Cables & Keyboard)
along the SHERE II fluid modules and stowage
tray are scheduled to come down from ISS on
the Space-X Demo flight which successfully
launch on May 22, 2012. NASA Glenn Research
Center, Cleveland, Ohio image.