Normal stresses in fibre suspensions

Zirnsak, M.A.; Hur, Dong-Soo; Boger, David V.

doi:10.1016/0377-0257(94)80020-0

Cited by 75 publications

(58 citation statements)

References 69 publications

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“…DP e has also been used for estimation of extensional viscosity. [2][3][4] Zirnsak et al 5 gave a good review of the theories related to suspension, and their ability to predict the steady shear and extensional viscosities, as well as the first normal stresses observed in dilute and semiconcentrated solutions.…”

Section: Introductionmentioning

confidence: 99%

End pressure corrections in capillary rheometry of concentrated suspensions

Wang

Joshi

Lam

et al. 2009

J of Applied Polymer Sci

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ABSTRACT:The end effect of a capillary die was investigated on concentrated suspensions with different particle concentrations, using dies with different diameters and at different temperatures. Nonlinearity in the Bagley plots was observed experimentally, and the nonlinearity increased with increasing particle concentration, decreasing temperature, and smaller capillary dies. Calculated end pressures based on the nonlinear Bagley plots were compared with those measured using an orifice die. As the extruded melts tended to stick on the exit wall of the capillary die, measurements by orifice die registered (40-50%) higher losses than those obtained from Bagley corrections. The key factors, which include particle concentration, contraction ratio, temperature, and flow rate, were discussed for their effects on end pressure. A formula was proposed combining the effects of these factors. Good agreement was obtained between the calculated end pressures with predicted results by the proposed formula.

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Section: Introductionmentioning

confidence: 99%

End pressure corrections in capillary rheometry of concentrated suspensions

Wang

Joshi

Lam

et al. 2009

J of Applied Polymer Sci

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“…In fact, the overshoot of the axial velocity along the centerline has been reported in experimental investigations involving the flow of polymer solutions through contractions (Quinzani et al, 1994). This overshoot has been attributed to the interactions between the flow and the first normal stress differences, which are known to be present in the flow of suspensions of fibres in a Newtonian fluid (Zirnsak et al, 1994). Therefore, one may speculate that the overshoot obtained in the numerical simulations should be observed in experimental visualization of flows similar to the one we are studying.…”

Section: Profiles Of the Axial Velocitymentioning

confidence: 93%

Numerical Modelling of the Flow of Fibre Suspensions through a Planar Contraction

Azaiez

Guénette

2002

Can J Chem Eng

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Fibre reinforced composites have gained increasing technological importance due to their versatility, which lends them to a wide range of applications. These composites are useful because they include a reinforcing phase in which high tensile strengths can be reached, and a matrix that allows one to hold the reinforcement and to transfer the applied stress to it. It is a well-known fact that such materials can have excellent mechanical, thermal, and electrical properties that make them widely used in industry. During the manufacturing process, fibres adopt a preferential orientation that can vary significantly across the geometry. Once the suspension is cooled or cured to make a solid composite, the fibre orientation becomes a key feature of the final product since it affects the elastic modulus, the thermal and electrical conductivities, and the strength of the composite material (Pipes et al., 1982;Agari et al., 1991).With the increase in composite materials usage, interest in the rheology and processing of fibre suspensions has increased significantly. This growing interest stems from the need to model the flow of fibres as accurately as possible in order to design and control manufacturing processes that generate favourable fibre orientations states, which will ultimately lead to the best mechanical and thermal properties of the composite. The rheological behaviour of a suspension of rigid particles has been the subject of a considerable amount of research (Stover et al., 1992;Becraft and Metzner, 1992;Bay and Tucker, 1992;Ramazani et al., 1997). Most of the existing theoretical work is based on the early studies of Jeffery (1923) and Batchelor (1971).Continuum models are often used to describe the orientation of fib r e s in a flo w. These models are hyperbolic in nature, and often lead to sharp b o u n d a ry layers and singularities even for simple flow geometries. In order to avoid this limitation, many authors adopted a simplifying approach known as the fibre-aligned assumption to study fibre suspension flows in various contraction and expansion geometries (see for example Lipscomb et al., 1988;Chiba et al., 1990; Baloch and We b s t e r, 1995). In this approach, it is assumed that the fibre is completely aligned with the streamlines, and therefore one has to solve only for the velocity field from which the fibre orientation can be deduced. The same approach has also been used by Rallison and Keiller (1993) to investigate

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“…Mongruel et al (1999) suggested that measurements showing shear thinning behaviour are not a true reflection of hydrodynamic stress. Zirnsak et al (1994) proposed the possible reasons as the formation of fibre aggregates and anisotropic fibre orientation, but the explanation is not supported by any experimental evidence.…”

Section: Shear-thinning Properties Of Carbon Fibre Suspensionsmentioning

confidence: 96%

The shear viscosity of carbon fibre suspension and its application for fibre length measurement

2015

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. (2016) The shear viscosity of carbon fibre suspension and its application for fibre length measurement. Rheologica Acta, 55 (1). pp. A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. AbstractThe viscosity of short carbon fibre suspensions in glycerol aqueous solution was measured using a bespoke vane-in-cup viscometer, where the carbon fibre has an aspect ratio from 450 to 2209. In the semi-concentrated regime, nL 3 ranging from 20 to 4400, the suspensions demonstrated strong shear-thinning characteristics particularly at higher concentrations. The shear-thinning characteristic is strongly related to the crowding factor proposed by Kerekes, indicating that non-hydrodynamic interactions occur in the suspensions. The influence of fibre bending on viscosity emerges when the bending ratio is lower than 0.0028. An empirical model based on transient network formation and rupture was proposed and used to correlate the relative viscosity with fibre concentration nL 3 and shear rate. Based on the model, a viscosity method is established to analyse the fibre length by measuring the viscosity of the fibre suspension using a bespoke vane-in-cup viscometer.

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Normal stresses in fibre suspensions

Cited by 75 publications

References 69 publications

End pressure corrections in capillary rheometry of concentrated suspensions

End pressure corrections in capillary rheometry of concentrated suspensions

Numerical Modelling of the Flow of Fibre Suspensions through a Planar Contraction

The shear viscosity of carbon fibre suspension and its application for fibre length measurement

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