Journal
RHEOLOGICA ACTA
Volume 49, Issue 2, Pages 119-129Publisher
SPRINGER
DOI: 10.1007/s00397-009-0415-3
Keywords
Suspension; Thixotropy; Extensional flow; Elongational flow; Shear thickening
Categories
Funding
- National Science Foundation [CBET-0547150]
- MRSEC
- CHM at the University of Massachusetts, Amherst
- Division Of Materials Research
- Direct For Mathematical & Physical Scien [820506] Funding Source: National Science Foundation
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A filament-stretching rheometer is used to measure the extensional viscosity of a shear-thickening suspension of cornstarch in water. The experiments are performed at a concentration of 55 wt.%. The shear rheology of these suspensions demonstrates a strong shear-thickening behavior. The extensional rheology of the suspensions demonstrates a Newtonian response at low extension rates. At moderate strain rates, the fluid strain hardens. The speed of the strain hardening and the extensional viscosity achieved increase quickly with increasing extension rate. Above a critical extension rate, the extensional viscosity goes through a maximum and the fluid filaments fail through a brittle fracture at a constant tensile stress. The glassy response of the suspension is likely the result of jamming of particles or clusters of particles at these high extension rates. This same mechanism is responsible for the shear thickening of these suspensions. In capillary breakup extensional rheometry, measurement of these suspensions demonstrates a divergence in the extensional viscosity as the fluid stops draining after a modest strain is accumulated.
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