E-FiRST: Electric field responsive shear thickening fluids

Shenoy, Sudhir; Wagner, Norman J.; Bender, Jonathan W.

doi:10.1007/s00397-002-0289-0

Cited by 28 publications

(10 citation statements)

References 18 publications

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“…This is due to the fact that the majority of investigations are performed when the fluid is excited by a single-frequency sinusoidal AC field or by a DC one, and only a limited number of publications consider a detailed investigation over a range of frequencies [17][18][19][20][21][22]. Furthermore, to our knowledge, no systematic studies have been performed on the role of the waveform (at different amplitudes and/or frequencies) of the external electric field on the ER effect.…”

Section: Introductionmentioning

confidence: 90%

Rheological properties of a model colloidal suspension under large electric fields of different waveforms

Espin

Delgado

González‐Caballero

et al. 2007

Journal of Non-Newtonian Fluid Mechanics

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Section: Introductionmentioning

confidence: 90%

Rheological properties of a model colloidal suspension under large electric fields of different waveforms

Espin

Delgado

González‐Caballero

et al. 2007

Journal of Non-Newtonian Fluid Mechanics

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“…These suspensions feel like a thin liquid at low stresses, but become very thick and can even crack like a solid at higher stresses, and become thin again when the stress is removed. Such materials are of practical interest for their properties as dampeners and shock absorbers (Lee et al, 2003;Shenoy et al, 2003;Jolly and Bender, 2006). While some milder types of shear thickening can be explained as viscous (Brady and Bossis, 1985;Wagner and Brady, 2009;Cheng et al, 2011) or inertial (Bagnold, 1954) effects, prior approaches have not been very successful at describing the dramatic effects of Discontinuous Shear Thickening.…”

Section: Introductionmentioning

confidence: 99%

The role of dilation and confining stresses in shear thickening of dense suspensions

Brown¹,

Jaeger²

2012

Journal of Rheology

289

341

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Many densely packed suspensions and colloids exhibit a behavior known as Discontinuous Shear Thickening in which the shear stress jumps dramatically and reversibly as the shear rate is increased. We performed rheometry and video microscopy measurements on a variety of suspensions to determine the mechanism for this behavior. We distinguish Discontinuous Shear Thickening from inertial effects by showing that the latter are characterized by a Reynolds number but are only found for lower packing fractions and higher shear rates than the former. Shear profiles and normal stress measurements indicate that, in the shear thickening regime, stresses are transmitted through frictional rather than viscous interactions, and come to the surprising conclusion that for concentrated suspensions such as cornstarch in water which exhibit the phenomenon of Discontinuous Shear Thickening, the local constitutive relation between stress and shear rate is not necessarily shear thickening. If the suspended particles are heavy enough to settle we find the onset stress of shear thickening τmin corresponds to a hydrostatic pressure from the weight of the particle packing where neighboring particles begin to shear relative to each other. Above τmin, dilation is seen to cause particles to penetrate the liquid-air interface of the sheared sample. The upper stress boundary τmax of the shear thickening regime is shown to roughly match the ratio of surface tension divided by a radius of curvature on the order of the particle size. These results suggest a new model in which the increased dissipation in the shear thickening regime comes from frictional stresses that emerge as dilation is frustrated by a confining stress from surface tension at the liquid-air interface. We generalize this shear thickening mechanism to other sources of a confining stress by showing that, when instead the suspensions are confined by solid walls and have no liquid-air interface, τmax is set by the stiffness of the most compliant boundary which frustrates dilation. All of this rheology can be described by a non-local constitutive relation in which the local relation between stress and shear rate is shear thinning, but where the stress increase comes from a normal stress term which depends on the global dilation.

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“…One proposed mechanism in which compressional stress contributes to shear thickening is hydroclustering (Brady & Bossis, 1988;Farr et al, 1997;Shenoy et al, 2003;Melrose & Ball, 2004) in which the compressive and viscous lubrication stresses cause particles to cluster along the compressive axis at a 45…”

Section: Discussionmentioning

confidence: 99%

Shear thickening in densely packed suspensions of spheres and rods confined to few layers

Brown¹,

Zhang²,

Forman³

et al. 2010

Journal of Rheology

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We investigate confined shear thickening suspensions for which the sample thickness is comparable to the particle dimensions. Rheometry measurements are presented for densely packed suspensions of spheres and rods with aspect ratios 6 and 9. By varying the suspension thickness in the direction of the shear gradient at constant shear rate, we find pronounced oscillations in the stress. These oscillations become stronger as the gap size is decreased, and the stress is minimized when the sample thickness becomes commensurate with an integer number of particle layers. Despite this confinement-induced effect, viscosity curves show shear thickening that retains bulk behavior down to samples as thin as two particle diameters for spheres, below which the suspension is jammed. Rods exhibit similar behavior commensurate with the particle width, but they show additional effects when the thickness is reduced below about a particle length as they are forced to align; the stress increases for decreasing gap size at fixed shear rate while the shear thickening regime gradually transitions to a Newtonian scaling regime. This weakening of shear thickening as an ordered configuration is approached contrasts with the strengthening of shear thickening when the packing fraction is increased in the disordered bulk limit, despite the fact that both types of confinement eventually lead to jamming.When fluids are confined to thin layers, their flow behavior can differ markedly from the bulk. This is an issue of considerable importance in situations ranging from molecular lubrication films where it can induce increased friction (Braun & Naumovets, 2006) to macroscopic granular materials flowing out of a narrow hopper opening, where the particles can jam into rigid structures. Here we investigate this transition from flowing to jamming for densely packed, non-Brownian suspensions which exhibit shear thickening in the absence of strong interparticle interactions (Barnes, 1989;Brown et al., 2010). Shear thickening fluids are non-Newtonian such that their dynamic viscosity -defined as shear stress divided by shear rate in a steady state -increases over some range of shear rate. In dense suspensions this phenomenon is remarkable because it is characterized by a dramatic increase of stress with shear rate (Metzner & Whitlock, 1958;Hoffmann, 1972;1982;Laun, 1994;Frith et al., 1996;Maranzano & Wagner, 2001;Egres & Wagner, 2005;Lootens et al., 2005;Fall et al., 2008;Brown & Jaeger, 2009) which goes by the name of Discontinuous Shear Thickening, as well as the ability to absorb impacts (Lee et al., 2003). Consequences of jamming can be seen even in bulk rheology in terms of a critical packing fraction φ c corresponding to random loose packing above which the suspension is jammed, i.e. a yield stress is measured. This critical packing fraction controls the shear stress as a function of shear rate such that the slope increases with packing fraction and becomes discontinuous at φ c (Brown & Jaeger, 2009). Prior work on shear thickening fluids ...

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E-FiRST: Electric field responsive shear thickening fluids

Cited by 28 publications

References 18 publications

Rheological properties of a model colloidal suspension under large electric fields of different waveforms

Rheological properties of a model colloidal suspension under large electric fields of different waveforms

The role of dilation and confining stresses in shear thickening of dense suspensions

Shear thickening in densely packed suspensions of spheres and rods confined to few layers

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