A shear sensitive monomer-polymer liquid crystal system for wind tunnel applications

Parmar, D. S.; Singh, J. J.; Eftekhari, Abe

doi:10.1063/1.1142963

Cited by 9 publications

(4 citation statements)

References 8 publications

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“…The most common sensing application of liquid crystals is provided through the thermochromic effect of the chiral nematic phase. [91] In addition, chiral nematic phases have been utilized as sensory media in investigating the structures and aerodynamics of metal surfaces [92] and as voltage sensors in battery testers.…”

Section: Amplification Of Informationmentioning

confidence: 99%

Transmission and Amplification of Information and Properties in Nanostructured Liquid Crystals

et al. 2008

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In recent years the design of chemical structures of liquid-crystalline materials has developed rapidly, and in many cases changed radically. Since Reinitzer's days, liquid crystals have either been classed as rodlike or disclike, with combinations of the two leading to phasmidic liquid crystals. The discovery that materials with bent molecular structures exhibited whole new families of mesophases inspired investigations into the liquid-crystal properties of materials with widely varying molecular topologies-from pyramids to crosses to dendritic molecules. As a result of conformational change, supermolecular materials can have deformable molecular structures, which can stabilize mesophase formation, and some materials that are non-mesogenic, on complexation form supramolecular liquid crystals. The formation of mesophases by individual molecular systems is a process of self-organization, whereas the mesophases of supramolecular systems are formed by self-assembly and self-organization. Herein we show 1) deformable molecular shapes and topologies of supermolecular and self-assembled supramolecular systems; 2) surface recognition processes of superstructures; and 3) that the transmission of those structures and their amplification can lead to unusual mesomorphic behavior where conventional continuum theory is not suitable for their description.

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Section: Amplification Of Informationmentioning

confidence: 99%

Transmission and Amplification of Information and Properties in Nanostructured Liquid Crystals

et al. 2008

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“…Die bekannteste Anwendung von Flüssigkristallen als Sensoren bedient sich des thermochromen Effekts der chiralen nematischen Phase. [91] Darüber hinaus wurden chirale nematische Phasen als Sensormedien bei der Untersuchung der Struktur und Aerodynamik von Metalloberflächen [92] und als Spannungsprüfer in Batterietestgeräten verwendet.…”

Section: Amplifikation Von Informationunclassified

Übertragung und Amplifikation von Informationen und Eigenschaften in nanostrukturierten Flüssigkristallen

et al. 2008

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In den letzten Jahren hat sich das Design der chemischen Strukturen flüssigkristalliner Materialien stark und in vielen Fällen sogar radikal verändert. Seit Reinitzers Tagen wurden Flüssigkristalle entweder als stab‐ oder als scheibenförmig klassifiziert; Kombinationen davon führten zu phasmidischen Flüssigkristallen. Die Entdeckung, dass Materialien mit gebogenen Molekülstrukturen eine völlig neue Familie von Mesophasen bilden, hat den Fokus auf Substanzen mit einer großen Variationsbreite an Molekültopologien gerichtet: von Pyramiden zu Kreuzen und dendritischen Molekülen. Die Molekülstrukuren supermolekularer Materialien können durch Konformationsänderungen verformt werden können, was zu einer Stabilisierung der Mesophase führen kann, und Substanzen, die selbst nicht mesogen sind, können mesogene supramolekulare Komplexe bilden. Die Bildung von Mesophasen ist ein Prozess der Selbstorganisation, der bei supramolekularen Systemen auf zwei Ebenen stattfindet. In diesem Aufsatz wird gezeigt, dass 1) verformbare Molekülstrukturen und ‐topologien supermolekularer und selbstorganisierter supramolekularer Systeme, 2) Erkennungsprozesse an Grenzflächen von Superstrukturen und 3) die Übertragung und Amplifikation dieser Strukturen zur Bildung ungewöhnlicher Mesophasen führen können, die mit der konventionellen Kontinuumstheorie nicht ausreichend beschrieben werden können.

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“…Special surface treatments to counter this problem have been proposed. 18 A mixture with an unacceptably high viscosity would not exhibit a full-spectrum color-play response under the maximum applied shear, degrading the sensitivity of the measurement technique.…”

Section: Vector Measurement Methodologymentioning

confidence: 99%

“…A similar approach was recently employed by Parmar. 18 The absolute surface shear stress range for the present experiments was estimated 17 to be 0.3-2.6 psf.…”

Section: Experimental Arrangementmentioning

confidence: 99%

Measurement of surface shear stress vectors using liquid crystal coatings

Reda

Muratore

1994

AIAA Journal

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Under normal white light illumination and oblique observation, liquid crystal coating (LCC) color-change response to shear depends on both shear stress magnitude as well as the direction of the applied shear relative to the observer's line of sight. These color-change responses were quantified by subjecting a LCC to a wall-jet shear flow and measuring scattered-light spectra using a fiber optic probe and spectrophotometer. At any fixed shear stress magnitude, the maximum color change was measured when the shear vector was aligned with and directed away from the observer; changes in the relative in-plane view angle to either side of this vector/observer aligned position resulted in symmetric Gaussian reductions in measured color change. Based on these results, a surface shear stress vector measurement methodology, involving multiple oblique-view observations of the test surface, was formulated. Under present test conditions, the measurement resolution of this technique was found to be ±1 deg for vector orientations and ±5% for vector magnitudes. An approach to extend the present methodology to full-surface applications is proposed. Nomenclature Cf= skin friction coefficient D = jet exit diameter / = spectral scattering intensity N = number of data points used in curve fits or in datareduction technique V = velocity W = white light X, Y = chromaticity coordinates a = above-plane view angle, measured positive upward from zero in plane of test surface P = relative circumferential-view angle in plane of test surface measured between observer line of sight and shear vector (positive clockwise) AP = pressure difference used to drive jet flow X = wavelength of light A, D = dominant wavelength p = density T = magnitude of surface shear stress vector <| ) = circumferential angle in plane of test surface, measured positive counterclockwise from origin <| ) T = orientation of surface shear stress vector, directed away from observer with line-of-sight at <| ) = (| ) T Subscripts

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A shear sensitive monomer-polymer liquid crystal system for wind tunnel applications

Cited by 9 publications

References 8 publications

Transmission and Amplification of Information and Properties in Nanostructured Liquid Crystals

Transmission and Amplification of Information and Properties in Nanostructured Liquid Crystals

Übertragung und Amplifikation von Informationen und Eigenschaften in nanostrukturierten Flüssigkristallen

Measurement of surface shear stress vectors using liquid crystal coatings

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