Shear History Extensional Rheology Experiment (SHERE)
Research Area: Complex Fluids
Expedition(s): 17- 18
Principal Investigator(s): ● Gareth H. McKinley, PhD, Massachusetts Institute of
Technology, Cambridge, Massachusetts
RESEARCH OBJECTIVES
Shear History Extensional Rheology Experiment (SHERE) is designed to investigate the effect of
preshearing (rotation) on the stress and strain response of a polymer fluid (a complex fluid
containing long chains of polymer molecules) being stretched in microgravity. The fundamental
understanding and measurement of the extensional rheology of complex fluids is important for
understanding containerless processing, an important operation for fabrication of parts (such
as adhesives or fillers) using elastomeric materials on future exploration missions.
EARTH BENEFITS
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
lead 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.
SPACE BENEFITS
Understanding the extensional rheology of a complex fluid
such as a liquid polymer is key for containerless
processing because the absence of the bounding walls of a
container or vessel removes the shearing component of
the deformation that typically dominates Earth-based
processing operations. The resulting flow is thus shear-
free or extensional in character. Containerless processing is a central component in the
development of in-situ fabrication technology, such as a means of producing new parts on
demand or replacing existing parts or tools. This represents a critical element in the evolution
of an autonomous exploration capability. In-situ fabricated parts, which may include both new
and recycled materials, will be composed of plastics, filled polymers, metals, ceramics and
composites. SHERE plays a role in this area by measuring, in microgravity conditions, a material
The Shear History Extensional
Rheology Experiment (SHERE)
operations team monitoring the
progress of the experiment from the
NASA Glenn Research Center
Telescience Support Center in
Cleveland, Ohio. NASA Glenn
Research Center image.