Dissertations / Theses: 'Fibre'

1

Goh, Kheng Lim. "Fibre reinforcement in fibre composite materials : effect of fibre shape." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395069.

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The aim of this project was to investigate the effects of fibre shape on its ability to reinforce a fibre composite material. Analytical and finite element (FE) models of an axisymmetric fibre composite material were developed and used to achieve this aim. Fibres of cylindrical shape, ellipsoidal shape, with paraboloidal ends and with conical ends were considered: fibre geometry was further characterised by an axial ratio, q. The scope of this study covered elastic and plastic load transfer processes. The former corresponds to the initial loading stage whereby an applied tensile stress acting on a fibre composite causes stress in an elastic matrix to be transferred to an elastic fibre which is embedded in and adheres to the matrix. The latter corresponds to the next stage when, on progressive increase of the applied stress, the matrix yields and turns plastic and failure of adhesion at the fibre-matrix interface occurs. Two approaches were used to develop analytical models. In the first approach, equations were derived for calculating stress and displacement distributions in a general axisymmetric body. This approach was based on a stress function method for structural analysis of a statically indeterminate problem. The equations derived were implemented to model a fibre composite undergoing elastic load transfer by prescribing appropriate boundary conditions. However, the approach led to no useful solutions. In the second approach, first-order ordinary differential equations for solving axial, σ_z, and surface radial, σ_r, stresses in a fibre were formulated by considering forces at equilibrium in a stress element in a fibre subjected to a fibre-matrix interfacial stress. Equations for calculating these stresses to study plastic load transfer were derived from the differential equations by prescribing appropriate boundary conditions, σ_z was assumed to be constant in the radical direction of the fibre. For a cylindrical fibre, σ_z increases linearly, from zero at the ends, to a maximum value at the centre. At the other extreme, σ_z in a conical fibre was shown to be constant. The intermediate cases of a paraboloidal and an ellipsoidal fibre showed distribution of σ_z lying between these two extremes. The effectiveness of a fibre shape for reinforcement was defined for the plastic study. It was found that the conical fibre possessed the highest value; the cylindrical fibre gave the lowest value. From this study, it was concluded that: (1) an important property of all the tapers considered is to make the distribution of σ_z in a fibre more uniform; (2) fibres with conical ends are more effective for reinforcing fibre composite materials than cylindrical fibres.

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2

David, Marie. "Optimisation de la dispersion des fibres pendant le cycle de malaxage des bétons industriels." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1157/document.

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L'homogénéité des caractéristiques est garantie par une présence en fibres constante en tout point du matériau. La dispersion d'une espèce dans une autre est régie par des mécanismes de convection et/ou de diffusion. Pour des objets de la taille d'une fibre métallique, ces deux phénomènes trouvent leur origine dans le cisaillement appliqué au matériau, une donnée souvent inconnue et difficile à mesurer dans des malaxeurs à béton. Dans un premier temps, nous proposons une méthode permettant d'estimer l'efficacité d'un malaxeur. Elle est basée sur la mesure du diamètre moyen de granules de ciment fabriqués dans ce malaxeur. Nous montrons que la mesure de ce diamètre moyen permet de quantifier le cisaillement moyen. Dans un second temps, nous présentons un moyen de mesurer la dispersion des fibres pendant le malaxage des bétons à base de mesures de résistivité électrique. Puis, dans un troisième temps, nous mesurons la présence en fibres pendant le malaxage et relions le temps nécessaire à l'obtention d'une répartition homogène à la capacité de cisaillement du malaxeur
Fibers are added to the concrete to give it news properties. The homogeneity of these characteristics is assured by a constant presence of fiber as the whole material. The dispersion of one species within another is governed by convection and/or diffusion mechanisms. Concerning objects having the size of steel fiber, these two phenomena are caused by the shearing applied to the material, an unknown and difficult to measure datum in the case of concrete mixer. To begin, a method allowing to estimate the mixer's shearing is suggested. This method is based on the measurement of the medium diameter of cement aggregates produced in the mixer. The link between the medium diameter and the mean shearing is established. In a second time, a mean to measure fiber dispersion from electrical resistivity measurements during the concrete mixing is presented. Then, in a third time, fiber dispersion are measured during mixing. The link between necessary time to obtain an homogeneous distribution and the mixer's shearing ability is established

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3

Hyensjö, Marko. "On fibre suspension flow modelling : mechanical fibre flocculation and fibre orientation /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-344.

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4

Martinez, Pinon F. "Characterizing single-mode fibres and single-mode fibre lenses." Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383403.

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5

Hale, Zoe Miranda. "Fibre optic sensors using adiabatically tapered single mode fibres." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320155.

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6

Larsson, Per. "Dimensional Stability of Paper Influence of Fibre-Fibre Joints and Fibre Wall Oxidation." Licentiate thesis, KTH, Fibre and Polymer Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4635.

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Papper är ett mycket mångsidigt material. Trots detta finns det ett flertal egenskaper som begränsar papperets användbarhet. Ett av de större problemen med cellulosa- och lignocellulosafibrer är att de sänker sin fria energi genom att sorbera vatten, och denna sorption förändrar papperets dimensioner. Detta fenomen kallas vanligtvis för bristfällig dimensionsstabilitet och uppträder i form av registerfel vid flerfärgstryck eller som krullning, buckling och vågiga papperskanter vid utskrift, kopiering och lagring, eller med en vidare definition som förkortad livslängd hos lådor på grund av mekanosorptivt kryp.

Avsikten med denna avhandling har varit att studera och kvantifiera vilka egenskaper som styr, och hur de påverkar, den vatteninducerade dimensionsförändringen som sker hos ett fibernätverk, samt hur dess dimensionsstabilitet kan förbättras. Detta har studerats både genom att ändra fiberns fuktsorptionsegenskaper och genom att förändra adhesionen och kontaktgraden mellan fibrerna i fiber-fiberfogarna. Fogegenskaperna har också varierats genom att tillverka laboratorieark torkade under inspänning samt ark torkade fritt för att minimera mängden inbyggda spänningar i arket.

Blekt kraftmassa har behandlats med polyelektrolytmultilager (PEM) för att förbättra adhesionen mellan fibrerna och för att öka kontaktgraden mellan fibrerna i fogen. Kontaktgraden har även minskats genom förhorning av fibrerna före arkformning. För de ark som fick torka fritt gav PEM-behandlingen en ökad hygroexpansionskoefficient, det vill säga dimensionsförändringen normaliserad mot förändringen i fuktinnehåll, vid samma förändring i relativ luftfuktighet medan förhorningen minskade hygroexpansionskoefficienten något. Om arken emellertid torkades under inspänning observerades ingen skillnad i hygroexpansionskoefficient mellan de olika fibermodifieringarna. Detta tolkades som ett resultat av en ökad kontaktzon och en större utbredning ut ur fogens plan, när arken torkades utan inspänning. En utbredning som medför att en större del av fiberns transversella expansion överförs som expansion i pappersplanet.

Fibrernas fuktsorptionsegenskaper förändrades genom natriumperjodatoxidering av 1,4-glukanernas C2-C3-bindning. Detta skapade sannolikt tvärbindningar i fiberväggen som förbättrade fiberväggens tålighet både genom att låsa fibrillerna närmare varandra och genom att ta bort potentiella adsorptionssäten som annars är tillgängliga för vattenadsorption. Perjodatoxidationen minskar också fibrernas kristallinitet och således frigjorde oxidationen hydroxylgrupper där vattenmolekyler kan adsorbera. Detta innebar att oxidationen både minskade och ökade interaktionen mellan vatten och fibervägg, men dock på olika strukturell nivå. Tvärbindningarna visade sig också märkbart reducera sorptionshastigheten när arken utsattes för en förändrad luftfuktighet så länge de inte tidigare utsatts för relativa luftfuktigheter nära mättnad. Som ett resultat av den lägre förändringen i fuktinnehåll vid en förändring i luftfuktighet från 20 till 85 % RF minskade dimensionsförändringens amplitud för de tvärbundna arken upp till 30 %. Emellertid uppvisade de tvärbundna arken en högre hygroexpansionskoefficeint, vilket innebär att de blev mer känsliga för absoluta förändringar i fuktinnehåll.

Paper is a very versatile material. Nevertheless, there are several factors limiting its usefulness, and one of the major issues is that cellulosic and ligno-cellulosic fibres lower their free energy by sorbing water and this water changes the dimensions of the paper. This phenomenon is usually referred to as a lack of dimensional stability and is often evident as misregister during multicolour printing or curl, cockle and wavy edges during printing, copying and storage or, with a wider definition, also as a shortened life-time of boxes during storage due to mechano-sorptive creep.

The work described in this thesis aims to study and quantify the importance of the different mechanisms causing water-induced dimensional changes in a fibre network and to investigate how to improve the dimensional stability of ligno-cellulosic materials. This has been done both by altering the fiber properties such as the moisture sorptivity and by changing the adhesion and degree of contact within the fibre-fibre joints. The properties of the fibre-fibre joints have been varied by drying laboratory sheets both under restraint and freely to minimise the generation of built-in stresses.

Bleached kraft fibres were treated using the polyelectrolyte multilayer (PEM) technique to improve the adhesion between the fibres and to increase the molecular contact within the joints. In contrast, the degree of contact was impaired by hornifying the fibres before sheet preparation. For sheets allowed to dry freely, the PEM-treatment increased the hygroexpansion coefficient, i.e. the dimensional movement normalised with respect to the change in moisture content, when subjected to changes in relative humidity whereas the hornification process resulted in a slightly lowered hygroexpansion coefficient. However, when the sheets were dried under restraint, the different joint and fibre modifications led to no difference in hygroexpansion coefficient. This was interpreted as being a result of an increase in the total contact zone between the fibres when the sheets were dried under restraint, with a greater extension in the outof- plain direction of the joint resulting in a transfer of a larger part of the transverse swelling to the in-plane expansion.

The sorptivity of the fibres was changed by oxidising the C2-C3 bond of the 1,4- glucans with periodate. This most likely created covalent cross-links in the fibre wall both improved the integrity of the fibre wall by locking adjacent fibril lamellae to each other and also removed possible sites for water sorption onto the cellulose surfaces. Periodate oxidation also led to a decrease in the crystallinity of the cellulose within the fibres, making more cellulose hydroxyl groups available for the adsorption of water molecules. This means that the oxidation both decreased and increased the interaction between the fibre wall and moisture but, on two different structural levels. The crosslinks significantly reduced the sorption rate when the papers was subjected to changes in relative humidity, as long as the fibres were not subjected to humidities close to saturation. The smaller change in moisture content when the relative humidity was changed between 20 and 85 % RH meant that the dimensional stability of the crosslinked sheets was increased. On the other hand, the hygroexpansion coefficient was increased in the case of papers made from fibres with the highest degree of oxidation, i.e. the sheets became more sensitive to absolute changes in moisture content.

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7

Larsson, Per A. "Dimensional Stability of Paper : Influence of Fibre-Fibre Joints and Fibre Wall Oxidation." Licentiate thesis, KTH, Fiberteknologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4635.

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Abstract:

Papper är ett mycket mångsidigt material. Trots detta finns det ett flertal egenskaper som begränsar papperets användbarhet. Ett av de större problemen med cellulosa- och lignocellulosafibrer är att de sänker sin fria energi genom att sorbera vatten, och denna sorption förändrar papperets dimensioner. Detta fenomen kallas vanligtvis för bristfällig dimensionsstabilitet och uppträder i form av registerfel vid flerfärgstryck eller som krullning, buckling och vågiga papperskanter vid utskrift, kopiering och lagring, eller med en vidare definition som förkortad livslängd hos lådor på grund av mekanosorptivt kryp. Avsikten med denna avhandling har varit att studera och kvantifiera vilka egenskaper som styr, och hur de påverkar, den vatteninducerade dimensionsförändringen som sker hos ett fibernätverk, samt hur dess dimensionsstabilitet kan förbättras. Detta har studerats både genom att ändra fiberns fuktsorptionsegenskaper och genom att förändra adhesionen och kontaktgraden mellan fibrerna i fiber-fiberfogarna. Fogegenskaperna har också varierats genom att tillverka laboratorieark torkade under inspänning samt ark torkade fritt för att minimera mängden inbyggda spänningar i arket. Blekt kraftmassa har behandlats med polyelektrolytmultilager (PEM) för att förbättra adhesionen mellan fibrerna och för att öka kontaktgraden mellan fibrerna i fogen. Kontaktgraden har även minskats genom förhorning av fibrerna före arkformning. För de ark som fick torka fritt gav PEM-behandlingen en ökad hygroexpansionskoefficient, det vill säga dimensionsförändringen normaliserad mot förändringen i fuktinnehåll, vid samma förändring i relativ luftfuktighet medan förhorningen minskade hygroexpansionskoefficienten något. Om arken emellertid torkades under inspänning observerades ingen skillnad i hygroexpansionskoefficient mellan de olika fibermodifieringarna. Detta tolkades som ett resultat av en ökad kontaktzon och en större utbredning ut ur fogens plan, när arken torkades utan inspänning. En utbredning som medför att en större del av fiberns transversella expansion överförs som expansion i pappersplanet. Fibrernas fuktsorptionsegenskaper förändrades genom natriumperjodatoxidering av 1,4-glukanernas C2-C3-bindning. Detta skapade sannolikt tvärbindningar i fiberväggen som förbättrade fiberväggens tålighet både genom att låsa fibrillerna närmare varandra och genom att ta bort potentiella adsorptionssäten som annars är tillgängliga för vattenadsorption. Perjodatoxidationen minskar också fibrernas kristallinitet och således frigjorde oxidationen hydroxylgrupper där vattenmolekyler kan adsorbera. Detta innebar att oxidationen både minskade och ökade interaktionen mellan vatten och fibervägg, men dock på olika strukturell nivå. Tvärbindningarna visade sig också märkbart reducera sorptionshastigheten när arken utsattes för en förändrad luftfuktighet så länge de inte tidigare utsatts för relativa luftfuktigheter nära mättnad. Som ett resultat av den lägre förändringen i fuktinnehåll vid en förändring i luftfuktighet från 20 till 85 % RF minskade dimensionsförändringens amplitud för de tvärbundna arken upp till 30 %. Emellertid uppvisade de tvärbundna arken en högre hygroexpansionskoefficeint, vilket innebär att de blev mer känsliga för absoluta förändringar i fuktinnehåll.
Paper is a very versatile material. Nevertheless, there are several factors limiting its usefulness, and one of the major issues is that cellulosic and ligno-cellulosic fibres lower their free energy by sorbing water and this water changes the dimensions of the paper. This phenomenon is usually referred to as a lack of dimensional stability and is often evident as misregister during multicolour printing or curl, cockle and wavy edges during printing, copying and storage or, with a wider definition, also as a shortened life-time of boxes during storage due to mechano-sorptive creep. The work described in this thesis aims to study and quantify the importance of the different mechanisms causing water-induced dimensional changes in a fibre network and to investigate how to improve the dimensional stability of ligno-cellulosic materials. This has been done both by altering the fiber properties such as the moisture sorptivity and by changing the adhesion and degree of contact within the fibre-fibre joints. The properties of the fibre-fibre joints have been varied by drying laboratory sheets both under restraint and freely to minimise the generation of built-in stresses. Bleached kraft fibres were treated using the polyelectrolyte multilayer (PEM) technique to improve the adhesion between the fibres and to increase the molecular contact within the joints. In contrast, the degree of contact was impaired by hornifying the fibres before sheet preparation. For sheets allowed to dry freely, the PEM-treatment increased the hygroexpansion coefficient, i.e. the dimensional movement normalised with respect to the change in moisture content, when subjected to changes in relative humidity whereas the hornification process resulted in a slightly lowered hygroexpansion coefficient. However, when the sheets were dried under restraint, the different joint and fibre modifications led to no difference in hygroexpansion coefficient. This was interpreted as being a result of an increase in the total contact zone between the fibres when the sheets were dried under restraint, with a greater extension in the outof- plain direction of the joint resulting in a transfer of a larger part of the transverse swelling to the in-plane expansion. The sorptivity of the fibres was changed by oxidising the C2-C3 bond of the 1,4- glucans with periodate. This most likely created covalent cross-links in the fibre wall both improved the integrity of the fibre wall by locking adjacent fibril lamellae to each other and also removed possible sites for water sorption onto the cellulose surfaces. Periodate oxidation also led to a decrease in the crystallinity of the cellulose within the fibres, making more cellulose hydroxyl groups available for the adsorption of water molecules. This means that the oxidation both decreased and increased the interaction between the fibre wall and moisture but, on two different structural levels. The crosslinks significantly reduced the sorption rate when the papers was subjected to changes in relative humidity, as long as the fibres were not subjected to humidities close to saturation. The smaller change in moisture content when the relative humidity was changed between 20 and 85 % RH meant that the dimensional stability of the crosslinked sheets was increased. On the other hand, the hygroexpansion coefficient was increased in the case of papers made from fibres with the highest degree of oxidation, i.e. the sheets became more sensitive to absolute changes in moisture content.
QC 20101117

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8

Lee, Ching Hao. "Fire retardant behavior of Kenaf fibre reinforced Floreon composite." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/19908/.

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According to the report, more than 41% of fatalities in flight were to find to be caused by fire. In recent years, composites used in aircrafts are carbon fibre/ glass fibre reinforced epoxy, due to light weights and high strength properties. However, these composites are known as highly flammable. Serious fire incident will be created in a short time after a spark of fire. Furthermore, ingredients for fibre and epoxies are, toxic and resulting in the release of toxic gases during fire, and cutting off fresh air to survivors and hindering their escape. In the meantime, biopolymers have attracted considerable attention due to their environmentally friendly and sustainable nature, Kenaf Fibre (KF) is one of the most famous natural fibre used as a reinforcement in Polymer Matrix Composites (PMC). Kenaf is also known as Hibiscus Cannabimus L., and is an herbaceous annual plant that is grown in a wide range of weather conditions, growing more than 3 meters within 3 months. However, the inherent drawbacks associated with Floreon (FLO) based composites include brittleness, lower strength and high moisture sensitivity, which in turn limit their application in the aircraft industry. In order to overcome such drawbacks, two modification techniques were employed in this study: (1) incorporated kenaf fibre into polypropylene polymer with magnesium hydroxide flame retardant and (2) reinforces kenaf fibre and magnesium hydroxide by different combination of volume. Consequently, KF reinforced FLO or polypropylene (PP) composites with magnesium hydroxide (MH) flame retardant specimens were successfully developed using extrusion followed by hot pressing. The increment of KF contents in PP composites had shown higher tensile modulus and decomposed mass loss at onset temperature, but lower values in tensile strength, elongation, flexural strength and onset temperature. In the meantime, 25 wt% KF contented PP composite shown a slightly higher flexural strength, while the higher volume of MH filler in composites caused lower strength, tensile modulus, elongation, but with higher onset temperature and the 2nd peak temperature in thermogravimetric analysis (TGA) testing. Furthermore, increasing the KF contents in PP matrix has found lower mass residue. However, increasing of KF contents in MH contented composite had increased the mass residue at the end of the testing. On the other hand, the increment of the melt flow properties (MVR and MFR) was found for the KF or MH insertion, due to the hydrolytic degradation of the polylactic acid (PLA) in FLO. The deterioration of the entanglement density at high temperature, shear thinning and wall slip velocity were the possible causes for the higher melt flow properties. In the meantime, increasing the KF loadings caused the higher melt flow properties while the FLO composites with higher MH contents created stronger bonding for higher macromolecular chain flow resistance, hence, recorded lower melt flow properties. However, the complicated melt flow behavior of the KF reinforced FLO/MH biocomposites was found in this study. The high probability of KF-KF and KF-MH collisions was expected and there were more collisions for higher fibre and filler loading, causing lower melt flow properties. Besides that, insufficient resin for fibre wetting, hydrolytic degradation on the biopolymer and poor interfacial bonding were attributed to low strength profile. Yet, further addition of KF increased the tensile strength and flexural. Nevertheless, inserting KF and MH filler have shown positive outcome on flexural modulus. Insertion of KF and MH showed the deterioration of impact strength, while the addition of KF increased the impact strength. Meanwhile, FLO is a hydrophobic biopolymer which showed only a little of total water absorption. In this regard, for the first 24 hours, the water absorption rates were high for all bio-composites. Hence, it is worth mentioning that the high contents of KF in bio-composites shown higher saturation period and higher total amount of water absorption while MH caused shorter saturation period but lower total amount of water absorption. However, interface bonding incompatibility has increased the water absorption of KF/FLO/MH composites. Moreover, some synergistic effect was located in char formation, Tg reduction and a lower tan δ peak shown in the three-phase system (KF/FLO/MH). The MH filler was found to be more significant in enhancing mass residual. The Tg were show deterioration for all samples compared to pure FLO biopolymer. The melting temperature has found no meaningful change for either insertion of KF or MH or both. The values of co-coefficient, C recorded decreasing as increasing the fibre loading. This showing the fibres transfer the loading effectively. As conclusion, although 10KF5MH specimen does not have the best performance in mechanical properties, a higher flame retardancy shall provide KF reinforced FLO composite with MH filler for more applications in advanced sector especially, in hazardous environment.

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9

Draghetti, Michela. "Fibre naturali nel settore dei compositi: confronto fibre di lino vs. fibre di carbonio." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18602/.

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I materiali compositi possiedono proprietà funzionali e di resistenza sempre più performanti grazie alla natura dei rinforzanti in fibra di carbonio, i quali però sono caratterizzati da criticità relative al processo di trasformazione altamente energivoro e dispendioso, all’inquinamento collegato alla produzione delle fibre e al trattamento di sizing, nonché alla difficoltà nello stadio di separazione dei costituenti del manufatto composito e del conseguente riciclo. A causa di queste problematiche sono stati introdotti in produzione materiali a matrice epossidica rinforzata con fibre di lino. Lo studio è stato indirizzato verso la caratterizzazione delle materie prime che compongono i manufatti, quindi fibre e semilavorati, mediante analisi termiche dinamiche in DSC e TGA con il fine di determinare la composizione e resistenza dei singoli componenti e la misura della variazione nel comportamento quando sono uniti per comporre i prepreg. Sono state eseguite delle prove di igroscopicità, umidità e densità per ottenere una panoramica precisa sulle differenze nella struttura delle fibre in carbonio e lino che le differenzia in modo apprezzabile. Sono stati laminati compositi reticolati secondo tecnologia in autoclave, le cui proprietà sono state definite mediante prove termiche dinamiche in DSC, TGA, DMA, prove alla fiamma mediante conocalorimetro, prove fisiche di igroscopicità, umidità e densità, prove ottiche al SEM in seguito ad una rottura in trazione. Parte del progetto seguito è stato direzionato all’ottimizzazione del ciclo produttivo in autoclave. La simulazione del nuovo ciclo di cura industriale, RAPID, è stata eseguita per valutare la variazione della Tg finale e il grado di curing, nonché le proprietà termiche e meccaniche già valutate nel ciclo di cura, STANDARD.

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10

Apriyanto, Haris. "Study, analysis and experimental validation of fiber refractometers based on single-mode, multimode and photonic crystal fibers for refractive index measurements with application for the detection of methane." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0022.

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La mesure de l'indice de réfraction a été étudiée depuis qu'Ernest Abbé aie initialement conçu un réfractomètre en 1869, appelé le réfractomètre d'Abbé. Depuis lors, de nombreux réfractomètres ont été développés tels que le réfractomètre à prisme optique ainsi que le réfractomètre à fibre optique, en raison de leurs applications étendues pour la détection de divers paramètres physiques, biologiques et chimiques. Récemment, un grand nombre de chercheurs ont mis au point des réfractomètres basés sur des fibres optiques, exploitant des mécanismes tels que la résonance des plasmons de surface (SPR), les interférences multimodes, les fibres à réseaux de Bragg (FBG), les fibres à réseaux à longues périodes (LPG), les fibres optiques coniques et la fibre multimode à gaine dénudée. Les capteurs fibrés sont avantageux grâce à leur immunité contre les interférences électromagnétiques, passivité électrique au niveau de la sonde de détection et potentiel de mesure in situ à long terme. Cette thèse concerne le développement de modèles complets fonctionnels et précis pour les réfractomètres à fibres optiques basés sur la modulation d'intensité optique, en particulier la réfractométrie à fibre multimode à gaine dénudée ainsi que les systèmes hybrides associant fibres monomode et multimode, et un réfractomètre hybride tout fibré utilisant des fibres à cristaux photoniques. L'objectif clé de ce travail est de caractériser les performances de ces réfractomètres à fibres optiques basés sur la modulation d'intensité en termes de réponse en puissance, de sensibilité, de résolution et de dynamique de mesure. Les résultats de simulation qui sont corroborés expérimentalement démontrent que la très grande sensibilité obtenue dans la zone II (c'est-à-dire le régime de détection typiquement utilisé pour mesurer l'indice du milieu supérieur à l'indice de gaine mais inférieur ou égal à l'indice du coeur) pour tous les trois réfractomètres. Cependant, la sensibilité dans la Zone (c’est-à-dire le régime de détection pour lequel l’indice du milieu à mesurer est supérieur à celui du coeur) est très faible. Ainsi, un refractomètre fibré hybride monomode-multimode est utilisé pour améliorer la sensibilité dans la Zone III. D'autre part, la sensibilité pour la zone I (c'est-à-dire le régime de détection pour mesurer l’indice du milieu inférieur à l'indice de la gaine) a été améliorée en augmentant l'absorption des ondes évanescentes à l'aide du réfractomètre hybride tout fibré à base de fibres à cristaux photoniques à coeur solide. En termes d'application réelle du réfractomètre à fibre pour la détection biochimique, une preuve de concept pour un capteur du gaz méthane a été démontrée en utilisant les supramolécules de cryptophane-A qui permettent de piéger les molécules du méthane. Le cryptophane-A incorporé dans un film hôte à base de styrène acrylonitrile (SAN) est appliqué sur la zone dénudée du capteur comme une région fonctionnalisée. L'indice de réfraction de cette couche sensible augmente proportionnellement avec l'augmentation de la concentration du méthane, ce qui induit une variation de la puissance optique transmise dans le capteur fibré
Refractive index measurement has been studied since Ernest Abbé initially designed a refractometer in 1869, which is named the Abbé refractometer. Since then, numerous types of refractometers have been developed by employing either the optical prism-based refractometer or the optical fiber-based refractometer, due to their wide-ranging applications such as for sensingvarious physical, biological and chemical parameters. Recently, a large number of researchers have been developing refractometers based on optical fibers, exploiting mechanisms such as surface plasmon resonance (SPR), multimode interference, fiber Bragg gratings (FBG), long period gratings (LPG), tapered optical fibers, and striped-cladding multimode fibers (MMF), for their advantages in immunity against electromagnetic interference, electrical passivity at the sensing probe, and capability to long term in-situ measurement. This thesis concerns the development of comprehensively functional and accurate models for optical fiber refractometers based on optical intensity modulation, in particular for stripped-cladding MMF refractometry as well as hybrid systems involving a combination of single-mode-multimode fiber refractometery and the all-fiber hybrid refractometer using photonic crystal fibers. A key objective of this work is to characterize the performance of these intensity-based optical fiber refractometers in terms of their power response, sensitivity, resolution, and dynamic range. The simulation results which are corroborated experimentally demonstrate very high sensitivity being obtained in Zone II (i.e. the sensing regime typically employed for measuring a sensing medium index higher than the cladding index but less than or equal to the core index) for all three types of refractometers. However, the sensitivity in Zone III (i.e. the sensing regime for which the sensing medium index is higher than the core index) is very low. A hybrid single-mode fiber - multimode fiber configuration is used to improve the sensitivity in Zone III. On other hand, the sensitivity for Zone I (i.e. the sensing regime typically employed for measuring a sensing medium index lower than the cladding index) has been improved by increasing evanescent wave absorption using the all-fiber hybrid refractometer based on solid-core photonic crystal fibers. As a further potential of the fiber refractometer for applications in biochemical sensing, the proof-of-concept for a methane gas sensor has been demonstrated using supramolecular cryptophane-A which enables to trap the methane molecules. Cryptophane-A incorporated into a functionalized film of StyreneAcrylonitrile (SAN) host is applied to a de-cladded region of the sensor as the sensitive region. The refractive index of this functionalized layer increases proportionally with increasing methane concentration, subsequently inducing variations in the transmitted optical power along the fiber sensor

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11

Mortimore, David Bryan. "Tapered fibre devices for optical fibre communication systems." Thesis, University of Essex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296363.

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12

Nguyen, Minh Tuan. "Contribution à l'optimisation des processus de filature des fibres libériennes." Mulhouse, 1996. http://www.theses.fr/1996MULH0440.

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La régularité de masse linéique (titre) des structures textiles linéaires produites en filature constitue le critère de qualité le plus important. En se basant sur les théories stochastiques classiques de l'étirage en grappes des fibres textiles individualisées, l'auteur a proposé une modélisation originale et très générale applicable à toutes les fibres, individualisées ou agglomérées sous forme de faisceaux fibreux ; cette théorie concerne tout particulièrement les fibres libériennes telles que le jute et le lin qui se présentent toujours sous forme de «faisceaux techniques» dissociables au cours du processus de filature. Les développements théoriques ont été totalement validés par une expérimentation industrielle approfondie réalisée dans le centre d'essais N. Schlumberger, premier constructeur français de matériel de filature. Enfin, la limite de filabilité a été discutée

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13

Chandani, Sameer M. "Fibre optic sensors based on D-shaped elliptical core fibres." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31270.

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Optical fibre-based sensors have gained much attention over the past three decades and are gaining acceptance in many industries such as the aerospace, automotive, chemical processing, biological sensing, and medical industries. The work presented here demonstrates the use of D-shaped fibres as intensity-based fibre optic sensors. The fibres are etched to gain access to their evanescent optical fields and are operated in their "leaky", regimes, i.e., the regime in which optical power leaks out of their cores. The optical power transmission through the etched D-fibre, which constitutes the sensor head, depends on the refractive index of the measurand placed on the sensor head. Thus by using materials whose refractive indices depend on the desired measurands, intensity-based sensors can be realised. A "non-destructive" process for determining the etched cladding thickness of the D-fibre is also developed. Once calibrated for a specific fibre or fibre batch, only one thermo-optic oil, three temperature measurements and a mathematical fitting routine are required to determine the etched cladding thickness with an accuracy better than 0.3 μm. Four types of sensor are demonstrated. A refractive index sensor with a high resolution region and a low resolution region, both of which can be shifted by changing the operating wavelength, is demonstrated with a maximum resolution on the order of 10⁻⁶ refractive index units. Naturally, this leads to the development of a temperature sensor with an adjustable dynamic range and resolution that uses thermo-optic oils. Proof of principle is demonstrated for an electric field sensor using chiral smectic A liquid crystals. A continuous liquid level sensor (that can also be implemented as a discrete level sensor) is also demonstrated using only one optical source, one optical detector and a single length of fibre.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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14

Farrow, G. J. "Acoustic emission in carbon fibres and carbon fibre reinforced plastics." Thesis, University of Salford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334022.

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15

Wong, Doris Wai-Yin. "Toughening of epoxy carbon fibre composites using dissolvable phenoxy fibres." Thesis, Queen Mary, University of London, 2013. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8710.

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The aim of this study is to investigate a novel toughening approach for liquid mouldable carbon fibre/epoxy composites. The toughening mechanism is based on the use of thermoplastics for the toughening of epoxy resins in which polymer blends are formed, leading to phase separated morphologies which allows for various toughening mechanisms to take place. Instead of standard melt or solution blending, the thermoplastic in this study is introduced as solid phenoxy fibres, which are combined with dry carbon fabric preforms. These phenoxy fibres remain solid during resin infusion and dissolve when the laminates are heated and phase separation takes place before curing completed. The main benefits of this approach are that the viscosity of matrix resin remains low, which makes liquid moulding of these laminates possible. Localised and selective toughening of particular regions within a structure can also be achieved. Process time and cost can also be reduced by eliminating the polymer blending process. It was found that modification with phenoxy improved composite Mode-I interlaminar toughness significantly, with an increase of up to 10-folds for bifunctional epoxy composite and 100% for tetrafunctional epoxy composite, while tensile properties were not adversely affected. It was found that it is possible to combine the dissolvable phenoxy fibres with an undissolved aramid interleaf to improve toughness and damage properties. However, the phenoxy-epoxy systems had lowered environmental stability and degraded after hot-wet and solvent conditioning.

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16

Dobb, Helen L. "Fibre gratings in novel optical fibres for applications in sensing." Thesis, Aston University, 2007. http://publications.aston.ac.uk/8102/.

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This thesis presents the fabrication of fibre gratings in novel optical fibres for sensing applications. Long period gratings have been inscribed into photonic crystal fibre using the electric-arc technique. The resulting sensing characteristics were found to depend on the air-hole geometry of the particular fibre. This provides the potential of designing a fibre to have enhanced sensitivity to a particular measure and whilst removing unwanted cross sensitivities. Fibre Bragg gratings have been fabricated in a variety of polymer optical fibres, including microstructured polymer optical fibre, using a continuous wave helium cadmium laser. The thermal response of the gratings have been characterised and found to have enhanced sensitivity compared to fibre Bragg gratings in silica optical fibre. The increased sensitivity has been harnessed to achieve a grating based device in single mode step index polymer optical fibre by fabricating an electrically tunable fibre Bragg grating. This was accomplished by coating the grating region in a thin layer of copper, which upon application of a direct current, causes a temperature induced Bragg wavelength shift.

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17

Magne, Sylvain. "Etat de l'art des lasers à fibre : étude d'un laser à fibre dopée ytterbium et spectroscopie laser de fibres dopées." Saint-Etienne, 1993. http://www.theses.fr/1993STET4027.

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Cette thèse montre l'intérêt de l'amplification optique et des lasers à fibres dopées par des ions de terres-rares pour l'instrumentation et les capteurs à fibres optiques. Nous détaillons les avantages et les inconvénients d'une telle technologie placée dans son contexte d'optique intégrée, ainsi que ses perspectives d'utilisation. Apres rappel de la théorie de la propagation guidée dans les fibres optiques, les technologies permettant de réaliser des fibres optiques dopées sont décrites. Une étude comparative des méthodes d'analyses de préformes et de fibres dopées permettant de déterminer leurs profils de guidage et de dopage est également présentée. Le comportement amplificateur des fibres optiques dopées est ensuite décrit théoriquement en insistant sur les limites fixées par l'élargissement inhomogène de la transition laser. L'évolution du gain intégré de la fibre est mise en évidence en fonction des paramètres influants (longueur, rayon de dopage. . . ) en soulignant l'intérêt d'un rayon de dopage optimisé. Le seuil d'accrochage du laser est modélisé par des équations et des abaques sans dimension déterminant la longueur de fibre optimale en fonction des pertes de la cavité laser. La conception générale du laser à fibre est ensuite synthétisée et les technologies des composants d'optique intégrée adaptés à la fibre amplificatrice le constituant sont comparées. Les techniques expérimentales concernent principalement l'étude de l'accordabilité par excitation sélective de sites et de la limitation du gain par émission stimulée sur la transition de pompage induisant une absorption résiduelle non saturable ; l'étude des effets de transferts dans les fibres dopées par luminescence coopérative : l'étude d'un procédé de changement de valence par irradiation y conduisant à une réduction des ions uranium placés en matrice verre fluoré (zblan) ; la démonstration d'un effet laser à trois niveaux, fonctionnant en régime continu et en contre-réaction externe par réseau

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18

Yehouessi, Jean-Paul. "Modélisation et caractérisation de fibres de Bragg pixélisées pour application aux lasers intenses." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10196/document.

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Ces travaux portent sur la réalisation de fibres optiques à très grandes aires effectives pour applications aux lasers intenses. Les applications possibles de ces fibres sont le transport ou la génération de puissants faisceaux lasers. En se basant sur la famille de fibre optique appelée : "fibre de Bragg pixélisée", nous avons introduit le concept de double conditions demi-onde appliquée au mode d’ordre supérieur afin d’augmenter les pertes des modes LP11, LP21, LP02. Le principe d’hétérostructuration quant à lui a permis d’accentuer les pertes des modes d’ordre supérieur grâce à un effet de fuite. Ainsi donc, nous avons réalisé une fibre ayant un diamètre de cœur de 48 µm qui a permis l’obtention d’un diamètre de mode de 40 µm à la longueur d’onde 1050 nm. Dans un second temps, une géométrie de gaine plus simplifiée est proposée. Cette nouvelle géométrie de gaine nous a permis d’accéder à des diamètres de modes allant de 47 µm à 69 µm dans le cas de fibre à bande interdite photonique toutes solides. Ce dernier résultat constitue un diamètre de mode record dans le cas des fibres de Bragg toutes solides
This work concern the design and the realization of large mode area fiber applied to high power laser. The goal of these fibers are the carrying and the generation of powerful beam laser. Based on special laser family called : "Pixaleted Bragg Fiber" we introduced the innovative concept of double half wave stack conditions applied to the higher order mode to increase the losses of LP11, LP21, LP02 modes. The principle of heterostructuration has been applied in order to increase losses of high order modes using the sieve effect. We succeeded in realizing a fiber with a core diameter of 48 µm, allowing mode field diameter of 40 µm at the wavelength 1050 nm. In the second time, cladding’s geometry has been simplified. This new generation of fiber gives us access to mode field diameter from 47 µm to 69 µm in the case of all solid bandgap fiber. This last result is up to now the highest mode field diameter produced for all solid bandgap fibers

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19

Barber, Asa H. "Fibre-matrix interactions in model glass fibre-thermoplastic composities." Thesis, Imperial College London, 2002. http://hdl.handle.net/10044/1/11822.

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20

Matarneh, Aser Mohammed Zayed. "Radio over fibre systems using multimode fibre and OFDM." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.522970.

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Kelleher, Edmund J. R. "Advancements in mode-locked fibre lasers and fibre supercontinua." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9584.

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The temporal characteristics and the spectral content of light can be manipulated and modified by harnessing linear and nonlinear interactions with a dielectric medium. Optical fibres provide an environment in which the tight confinement of light over long distances allows the efficient exploitation of weak nonlinear effects. This has facilitated the rapid development of high-power fibre laser sources across a broad spectrum of wavelengths, with a diverse range of temporal formats, that have established a position of dominance in the global laser market. However, demand for increasingly flexible light sources is driving research towards novel technologies and an improved understanding of the physical mechanisms and limitations of existing approaches. This thesis reports a series of experiments exploring two topical areas of ongoing research in the field of nonlinear fibre optics: mode-locked fibre lasers and fibre-based supercontinuum light sources. Firstly, integration of novel nano-materials with existing and emerging fibre-based gain media allows the demonstration of ultrafast mode-locked laser sources across the near-infrared in a conceptually simple, robust, and compact scheme. Extension to important regions of the visible is demonstrated using nonlinear conversion. Scaling of pulse energies in mode-locked lasers can be achieved by operating with purely positive dispersion for the generation of chirped pulses. It is shown unequivocally, through a direct measurement, that the pulses generated in ultra-longmode-locked lasers can exist as highly-chirped dissipative soliton solutions of the cubic (and cubic-quintic) Ginzburg Landau equation. The development of a numerical model provides a framework for the interpretation of experimental observations and exposes unique evolution dynamics in extreme parameter ranges. However, the practical limitations of the approach are revealed and alternative routes towards achieving higher-energy are proposed. Finally, an experimental and numerical study of the dependence of continuous-wave pumped supercontinua on the coherence properties of the pump source shows an optimum exists that can be expressed as a function of the modulation instability period. A new and simplified model representing the temporal fluctuations expressed by continuous wave lasers is proposed for use in simulations of supercontinua evolving from noise. The implications of the experiments described in this thesis are summarised within the broader context of a continued research effort.

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22

Kahanji, Charles. "Fire performance of ultra-high performance fibre reinforced concrete beams." Thesis, Ulster University, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709889.

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Ultra-high performance fibre reinforced concrete (UHPFRC) possesses favourable mechanical properties in comparison with normal strength concrete. Despite a surge in interest among researchers and industries over the past decade, there is negligible research data on the performance of UHPFRC in fire. This situation is compounded by the lack of design guidelines of UHPFRC in major structural design codes both at ambient and at elevated temperatures. The experimental work conducted was divided into three parts. The first part involved casting and testing of nine beams for flexure at ambient temperature. The beams were reinforced with steel fibres at 1, 2 and 4 vol. % and cured in two different conditions (20 °C and 90 °C water). In the second part, nine beams with two different steel fibre dosages (2 and 4 vol. %) were tested at elevated temperatures under an ISO 834 standard fire curve. Seven of these were tested while loaded at three different loading levels (0.2, 0.4 and 0.6). The other two, cured in different conditions, were tested unloaded at elevated temperatures to study the influence of the curing temperature. The third part involved determining the residual strength of the UHPFRC. The residual strength tests sought to investigate the influence of the curing temperature on the strength degradation of UHPFRC, with the aim of understanding the post-fire analysis and repairs. A finite element model was created using DIANA software followed by a parametric study. In the ambient temperature tests, the hot-cured beams recorded higher compressive strength. However, despite having lower compressive strength, the cold-cured beams had the higher load bearing capacity. Exposure of beams to fire was characterised with explosive spalling. Spalling was more prevalent in beams containing 2 vol. % of steel fibres. The beams under the 0.4 load level spalled significantly more than the other two load categories and had the least fire resistance. The addition of polypropylene fibres eliminated spalling and effectively increased the fire resistance of the beam. The curing temperature had an influence on the fire performance of the beams, the hot-cured beam spalled significantly more than the cold-cured. The findings from the residual strength tests indicated that the relative residual strength of cold-cured elements was higher than the hot-cured.

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23

Islam, Mohammad Saiful. "The Influence of Fibre Processing and Treatments on Hemp Fibre/Epoxy and Hemp Fibre/PLA Composites." The University of Waikato, 2008. http://hdl.handle.net/10289/2627.

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In recent years, due to growing environmental awareness, considerable attention has been given to the development and production of natural fibre reinforced polymer (both thermoset and thermoplastic) composites. The main objective of this study was to reinforce epoxy and polylactic acid (PLA) with hemp fibre to produce improved composites by optimising the fibre treatment methods, composite processing methods, and fibre/matrix interfacial bonding. An investigation was conducted to obtain a suitable fibre alkali treatment method to: (i) remove non-cellulosic fibre components such as lignin (sensitive to ultra violet (UV) radiation) and hemicelluloses (sensitive to moisture) to improve long term composites stability (ii) roughen fibre surface to obtain mechanical interlocking with matrices (iii)expose cellulose hydroxyl groups to obtain hydrogen and covalent bonding with matrices (iv) separate the fibres from their fibre bundles to make the fibre surface available for bonding with matrices (v) retain tensile strength by keeping fibre damage to a minimum level and (vi) increase crystalline cellulose by better packing of cellulose chains to enhance the thermal stability of the fibres. An empirical model was developed for fibre tensile strength (TS) obtained with different treatment conditions (different sodium hydroxide (NaOH) and sodium sulphite (Na2SO3) concentrations, treatment temperatures, and digestion times) by a partial factorial design. Upon analysis of the alkali fibre treatments by single fibre tensile testing (SFTT), scanning electron microscopy (SEM), zeta potential measurements, differential thermal analysis/thermogravimetric analysis (DTA/TGA), wide angle X-ray diffraction (WAXRD), lignin analysis and Fourier transform infrared (FTIR) spectroscopy, a treatment consisting of 5 wt% NaOH and 2 wt% Na2SO3 concentrations, with a treatment temperature of 120oC and a digestion time of 60 minutes, was found to give the best combination of the required properties. This alkali treatment produced fibres with an average TS and Young's modulus (YM) of 463 MPa and 33 GPa respectively. The fibres obtained with the optimised alkali treatment were further treated with acetic anhydride and phenyltrimethoxy silane. However, acetylated and silane treated fibres were not found to give overall performance improvement. Cure kinetics of the neat epoxy (NE) and 40 wt% untreated fibre/epoxy (UTFE) composites were studied and it was found that the addition of fibres into epoxy resin increased the reaction rate and decreased the curing time. An increase in the nucleophilic activity of the amine groups in the presence of fibres is believed to have increased the reaction rate of the fibre/epoxy resin system and hence reduced the activation energies compared to NE. The highest interfacial shear strength (IFSS) value for alkali treated fibre/epoxy (ATFE) samples was 5.2 MPa which was larger than the highest value of 2.7 MPa for UTFE samples supporting that there was a stronger interface between alkali treated fibre and epoxy resin. The best fibre/epoxy bonding was found for an epoxy to curing agent ratio of 1:1 (E1C1) followed by epoxy to curing agent ratios of 1:1.2 (E1C1.2), 1: 0.8 (E1C0.8), and finally for 1:0.6 (E1C0.6). Long and short fibre reinforced epoxy composites were produced with various processing conditions using vacuum bag and compression moulding. A 65 wt% untreated long fibre/epoxy (UTLFE) composite produced by compression moulding at 70oC with a TS of 165 MPa, YM of 17 GPa, flexural strength of 180 MPa, flexural modulus of 10.1 GPa, impact energy (IE) of 14.5 kJ/m2, and fracture toughness (KIc) of 5 MPa.m1/2 was found to be the best in contrast to the trend of increased IFSS for ATFE samples. This is considered to be due to stress concentration as a result of increased fibre/fibre contact with the increased fibre content in the ATFE composites compared to the UTFE composites. Hygrothermal ageing of 65 wt% untreated and alkali treated long and short fibre/epoxy composites (produced by curing at 70oC) showed that long fibre/epoxy composites were more resistant than short fibre/epoxy composites and ATFE composites were more resistant than UTFE composites towards hygrothermal ageing environments as revealed from diffusion coefficients and tensile, flexural, impact, fracture toughness, SEM, TGA, and WAXRD test results. Accelerated ageing of 65 wt% UTLFE and alkali treated long fibre/epoxy (ATLFE) composites (produced by curing at 70oC) showed that ATLFE composites were more resistant than UTLFE composites towards hygrothermal ageing environments as revealed from tensile, flexural, impact, KIc, SEM, TGA, WAXRD, FTIR test results. IFSS obtained with untreated fibre/PLA (UFPLA) and alkali treated fibre/PLA (ATPLA) samples showed that ATPLA samples had greater IFSS than that of UFPLA samples. The increase in the formation of hydrogen bonding and mechanical interlocking of the alkali treated fibres with PLA could be responsible for the increased IFSS for ATPLA system compared to UFPLA system. Long and short fibre reinforced PLA composites were also produced with various processing conditions using compression moulding. A 32 wt% alkali treated long fibre PLA composite produced by film stacking with a TS of 83 MPa, YM of 11 GPa, flexural strength of 143 MPa, flexural modulus of 6.5 GPa, IE of 9 kJ/m2, and KIc of 3 MPa.m1/2 was found to be the best. This could be due to the better bonding of the alkali treated fibres with PLA. The mechanical properties of this composite have been found to be the best compared to the available literature. Hygrothermal and accelerated ageing of 32 wt% untreated and alkali treated long fibre/PLA composites ATPLA composites were more resistant than UFPLA composites towards hygrothermal and accelerated ageing environments as revealed from diffusion coefficients and tensile, flexural, impact, KIc, SEM, differential scanning calorimetry (DSC), WAXRD, and FTIR results. Increased potential hydrogen bond formation and mechanical interlocking of the alkali treated fibres with PLA could be responsible for the increased resistance of the ATPLA composites. Based on the present study, it can be said that the performance of natural fibre composites largely depend on fibre properties (e.g. length and orientation), matrix properties (e.g. cure kinetics and crystallinity), fibre treatment and processing methods, and composite processing methods.

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24

Fisher, Alex K. "Durability design parameters for cellulose fibre reinforced concrete pipes in aggressive environments." Thesis, Queensland University of Technology, 2003.

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25

Girondin, Victor. "Etude et modélisation d'un modulateur à électro-absorption pour des applications de transmission radio sur fibre de signaux ULB aux fréquences centimétriques. Simulation système et caractérisation d'une liaison radio sur fibre à modulation externe." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066127/document.

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Ce travail de thèse, consiste à étudier les performances d'une liaison Radio sur Fibre simplifiée mettant en ¿uvre une modulation extérieure de la source optique avec des signaux OFDM. La source laser est couplée sur une même puce avec un modulateur à électro-absorption, développée par Alcatel III-V LaB été modélisée à l'aide du logiciel ADS( Advanced Design System) et caractérisée au laboratoire.Dans une première partie, nous présenterons une introduction de la technologie Radio sur Fibre avec ses applications, et son intérêt pour les technologies futures.Dans une seconde partie, nous nous intéresserons à la modélisation électrique du modulateur à électro-absorption utilisée pour effectuer la modulation numérique de type OFDM.Dans une troisième partie, sera proposée un modèle complet de la chaine de transmission intégrant tous les composants de la liaison, de manière à effectuer une analyse comportementale du système.La quatrième partie, présentent les performances mesurées réalisées au laboratoire sur le banc de caractérisation de la chaine en modulation numérique OFDM Ultra Large Bande et simulées sous ADS et les corrélations entre les résultats
This thesis is to study the performance of a radio link over fiber simplified implementing an external modulation of the optical source with OFDM signals. The laser source is coupled on a single chip with an electro-absorption modulator, developed by Alcatel III-V LaB been modeled using software ADS (Advanced Design System) and characterized in the laboratory. In the first part, we will present an introduction to the Radio on Fiber technology with its applications, and its interest in future technologies.In the second part, we will focus on the electrical modeling of the electro-absorption modulator used to make the digital OFDM type. In the third part, will be offered a complete model of the transmission chain incorporating all components of the link, so as to perform behavioral analysis system. The fourth part, have measured performance in the laboratory on the chain of characterization bench in digital OFDM Ultra Wideband and simulated in ADS and correlations between the results

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Joung, Clint Gwarngsoo. "Direct simulation studies of suspended particles and fibre-filled suspensions." Thesis, The University of Sydney, 2003. http://hdl.handle.net/2123/554.

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A new Direct Simulation ﬁbre model was developed which allowed ﬂexibility in the ﬁbre during the simulation of ﬁbre suspension ﬂow.This new model was called the 'Chain-of-Spheres' model.It was hypothesised that particle shape and deformation could signiﬁcantly aﬀect particle dynamics,and also suspension bulk properties such as viscosity.Data collected from the simulation showed that ﬂexible ﬁbres in shear ﬂow resulted in an order of 7 −10% bulk relative viscosity increase over the 'rigid' ﬁbre result.Results also established the existence of a relationship between bulk viscosity and particle stiﬀness. In comparison with experimental results,other more conventional rigid ﬁbre based methods appeared to underpredict relative viscosity.The ﬂexible ﬁbre method thus markedly improved the ability to estimate relative viscosity.The curved rigid ﬁbre suspension also exhibited increased viscosity of the order twice that of the equivalent straight rigid ﬁbre suspension.With such sensitivity to ﬁbre shape,this result has some important implications for the quality of ﬁbre inclusions used.For consistent viscosity,the shape quality of the ﬁbres was shown to be important. The 'Chain of Spheres' simulation was substantially extended to create a new simulation method with the ability to model the dynamics of arbitrarily shaped particles in the Newtonian ﬂow ﬁeld.This new '3D Particle' simulation method accounted for the inertial force on the particles,and also allowed particles to be embedded in complex ﬂow ﬁelds.This method was used to reproduce known dynamics for common particle shapes,and then to predict the unknown dynamics of various other particle shapes in shear ﬂow. In later sections, the simulation demonstrated inertia-induced particle migration in the non-linear shear gradient Couette cylinder ﬂow,and was used to predict the ﬁbre orientation within a diverging channel ﬂow.The performance of the method was veriﬁed against known experimental measurements,observations and theoretical and numerical results where available.The comparisons revealed that the current method reproduced single particle dynamics with great ﬁdelity. The broad aim of this research was to better understand the microstructural dynamics within the ﬁbre-ﬁlled suspension and from it,derive useful engineering information on the bulk ﬂow of these ﬂuids.This thesis represents a move forward to meet this broad aim.It is hoped that future researchers may beneﬁt from the new approaches and algorithms developed here.

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Joung, Clint Gwarngsoo. "Direct simulation studies of suspended particles and fibre-filled suspensions." University of Sydney. Chemical Engineering, 2003. http://hdl.handle.net/2123/554.

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A new Direct Simulation ﬁbre model was developed which allowed ﬂexibility in the ﬁbre during the simulation of ﬁbre suspension ﬂow.This new model was called the �Chain-of-Spheres �model.It was hypothesised that particle shape and deformation could signi ﬁcantly a ﬀect partic e dynamics,and also suspension bulk properties such as viscosity.Data collected from the simulation showed that ﬂexible ﬁbres in shear ﬂow resulted in an order of 7 −10% bulk relative viscosity increase over the �rigid �ﬁbre result.Results also es- tablished the existence of a relationship between bulk viscosity and particle sti ﬀness.In comparison with experimental results,other more conventional rigid ﬁbre based methods appeared to underpredict relative viscosity.The ﬂexible ﬁbre method thus markedly improved the ability to estimate relative viscosity.The curved rigid ﬁbre suspension also exhibited increased viscosity of the order twice that of the equivalent straight rigid ﬁbre suspension.With such sensitivity to ﬁbre shape,this result has some important implications for the quality of ﬁbre inclusions used.For consistent viscosity,the shape quality of the ﬁbres was shown to be important. The �Chain of Spheres �simulation was substantially extended to create a new simulation method with the ability to model the dynamics of arbitrarily shaped particles in the Newtonian ﬂow ﬁeld.This new �3D Particle �simulation method accounted for the inertial force on the particles,and also allowed particles to be embedded in complex ﬂow ﬁelds.This method was used to reproduce known dynamics for common particle shapes,and then to predict the unknown dynamics of various other particle shapes in shear ﬂow. In later sections, the simulation demonstrated inertia-induced particle migration inthe non-linear shear gradient Couette cylinder ﬂow,and was used to predict the ﬁbre orientation within a diverging channel ﬂow.The performance of the method was veriﬁed against known experimental measurements,observations and theoretical and numerical results where available.The comparisons revealed that the current method reproduced single particle dynamics with great ﬁdelity. The broad aim of this research was to better understand the microstruc- tural dynamics within the ﬁbre-ﬁlled suspension and from it,derive useful engineering information on the bulk ﬂow of these ﬂuids.This thesis represents a move forward to meet this broad aim.It is hoped that future researchers may bene ﬁt from the new approaches and algorithms developed here.

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Yeung, Anson Chi-Ming Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "Polymer segmented cladding fibres: cross fibre modelling, design, fabrication and experiment." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2009. http://handle.unsw.edu.au/1959.4/43656.

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This thesis presents the first research on polymer-segmented-cladding-fibre (PSCF), an emerging class of microstructured- optical-fibres (MOFs), which allows single-mode operation with ultra-large-core area. This research covers the modelling, design, fabrication and experiment of the polymer optical cross-fibre (4-period-SCF) whose cross-sectional view resembles a cross. A new wedge waveguide model has been formulated and applied to demonstrate that for any given parameters, the cross fibre gives the same performance for single-mode operation as the N-period-SCFs (for N = 2, 6 and 8). These fibres behave identically if the high-index segment angle, θ1, is the same and the low-index segment angular width, θ2, is sufficiently large for negligible adjacent mode coupling effects. This remarkable finding has significant ramifications for SCF fabrication, design and performance. Theoretical predictions confirmed by experiments demonstrated that a cross-fibre is all that needed to fabricate a large-core single-mode-fibre with no geometry-induced birefringence. The high-index outer ring effects on the cross fibre single-mode performance have been systematically investigated for the first time. The study reveals that the ring index value higher than its core index has very strong effects on single-mode performance. Within a narrow range of θ1, the minimum fibre length required for single-mode operation is reduced but outside this angle range, longer single-mode length is required. Furthermore, the fibre can be anti-guiding if θ1 exceeds the cutoff angle. Incorporating the fabrication constraints, the optimal cross-fibre design with high-index ring is achieved by optimising the relative index difference, high-index segment angle and core-cladding diameter ratio. Two preform-making techniques developed for the cross-fibres fabrication include the cladding-segment-in-tube method and the core-cladding-segment-in-tube method. The innovative approach in these methods overcomes the problems of bubble formation and fractures, which are related to the fibre structure complexity and the polymer intrinsic properties and their processing. It enables the successful drawing of single-mode fibres. This thesis reports the first experimental demonstration of single-mode operation of large-core cross-fibre. Three experimental studies with different cross-fibre designs have demonstrated (i) large-core single-mode operation, (ii) high-index ring effects on fibre performance and (iii) cross-fibre optimal design trial. Apart from this, the 8-period-SCF fibre performance has been demonstrated experimentally.

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Farhat, Ali Farag. "Basic problems of fibre-reinforced structural components when fibres resist bending." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/31095/.

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This thesis generates certain sets of analytical and approximate solutions to a new class of partial differential equations stemming from a version of asymmetricstress elasticity theory appropriate for the study and prediction of the behaviour of fibre-reinforced materials containing fibres that resist bending. These new solutions are of theoretical and practical interest in the static and dynamic analysis of thinwalled, linearly elastic fibre-reinforced structures influenced by couple-stress and unsymmetric stress due to fibre bending stiffness. The static and free vibration solutions are constructed considering bending resistance fibres in a small deformation of beams and plates. Numerical results for displacements, stresses, couple-stress and natural frequencies of vibration are provided to investigate the influence of the fibres resistance in bending on the deformed beams and plates.

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30

Xu, Ming Gang. "The measurement of physical fields using optical fibres and fibre gratings." Thesis, University of Southampton, 1995. https://eprints.soton.ac.uk/399097/.

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In this thesis a number of novel optical fibre and fibre Bragg grating sensors have been investigated for the purpose of measuring physical fields, particularly strain, temperature and pressure. These sensors are based on using short coherence length light source. Two laboratory prototypes of interferometric fibre pressure sensors have been demonstrated using a hollow-glass microsphere and optical fibres, respectively. These are intended for ultimate application as strain sensors for smart structures. A novel white-light polarimetric interrogator is demonstrated. The device consists of two equal lengths of highly-birefringent fibre, spliced with their polarization axes orthogonal. The dispersion effect on the responsivity of white-light interferometry is evaluated using a simplified transfer function. Using Jones matrix and Poincaré sphere analysis methods, the device performance has been discussed. Experimental results are presented by thermally-scanning the device for the interrogation of sensing interferometer. A fibre Bragg grating sensor for measuring pressure, strain and temperature is evaluated using measured data from over twenty different fibre gratings including Bragg gratings in highly-birefringent fibres. Intensive experimental results on thermally-induced decay of fibre gratings are presented for the evaluation of their potential in a wide variety of sensors and multiplexed systems. A first demonstration of a fibre grating interrogation system using an acousto-optic tunable filter is presented. The system involves frequency-shift-keying of the RF drive to the filter to track the measurand-induced wavelength shifts of multiplexed fibre gratings. An equivalent linear model has been developed to describe the operation of a wavelength tracking loop. Experimental results for both open-loop and close-loop operations are presented for strain and temperature measurements. Three novel techniques to resolve the thermal effect in strain measurement using fibre gratings are demonstrated. The first method involves using surface-mounted fibre grating pairs to compensate for thermal effects. The second technique uses two superimposed fibre gratings (single sensing element) to simultaneously measure strain and temperature. Last but not least by using a chirped Bragg grating in a tapered optical fibre as a strain sensing element, strain sensing can be made to be temperature-independent. Both theoretical analysis and experimental work are presented for these approaches.

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Wang, Ji. "Novel multicomponent glasses and fibres for fibre-optic devices and systems." Thesis, University of Southampton, 1995. https://eprints.soton.ac.uk/399119/.

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This thesis describes the novel multicomponent glasses as the basis for fibre optic device and system applications. It is shown that multicomponent glasses are expected to greatly enhance the functionality of the fibre-optical devices and systems by compensating for the limitations of current silica-glass based fibre-devices. Fabrication and characterization of various multicomponent glasses and fibres suitable for specific applications have been investigated. The fabrication of rare-earth-doped multicomponent glasses based on commercial optical-glasses has been tackled by developing a novel doping technique. An intermediate maximum phonon-energy lead-germanate glass suitable for fibre optic applications has been achieved by optimizing the glass composition via the Levin-Block concept. Non-hygroscopic chlorotellurite glass. 60TeO2. 40ZnCl2, and its modifications for fibre structure have been prepared, their intrinsic high thermal-stabilities characterized and intrinsic optical transparency in the mid-IR evaluated. Spectroscopic and structural characterization of rare-earth-doped multi-component glasses and fibres have also been conducted. Radiative and non-radiative processes for rare-earth transitions in glasses were studied with a view to finding materials in which rare-earth transitions are more radiative and less non-radiative. A "crystal-chemistry" model is proposed to evaluate the rare-earth local structure in glass, based on the Modified-Random-Network (MRN) theory in glass structure. The rare-earth spectral behaviour in glasses has been well described and predicted by this model. Using the rare-earth-doped novel multicomponent glass-waveguides has led to a number of fibre and planar-waveguide laser devices having been demonstrated. This includes the most efficient and a high-power Nd3+- fibre laser ever reported at 1.06µm in oxide glasses, the first demonstration of Nd3+- and Er3+- doped monomode planar-waveguide lasers at 1.06µm and 1.54µm and a new class of fibre laser based on rare-earth-doped lead-germanate glass.

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32

Fan, Yuan-Heng. "Fibre orientation and stiffness prediction in short fibre-reinforced thermoplastics." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339669.

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Dhillon, Jagminder. "Coated fibre composites using rubbery and ductile fibre/matrix interlayers." Thesis, Loughborough University, 1991. https://dspace.lboro.ac.uk/2134/33043.

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Advanced composite materials possessing high specific stiffness and strength have been successfully employed as structural materials in the aerospace, military and automotive industries. Despite the advantages that composites have over other materials, further development has been restricted by their brittleness. The aim of this research project was to improve the energy absorbing capabilities of unidirectional glass fibre epoxy resin composites by coating the fibres with an interlayer. UHMWPE was used as the interlayer because of its outstanding toughness while EPDM of low modulus was used to assess the difference between energy absorption through plastic deformations (UHMWPE) and highly elastic deformations (EPDM).

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34

Bonhomme, Oriane. "Étude de la formation de fibres en microfluidique : compétition entre mise en forme et gélification de fluides complexes sous écoulement." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14306/document.

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Cette thèse est consacrée à l’étude en microfluidique de la fabrication de fibres. Les deux étapes critiques sont : - la mise en forme du matériau : nous avons étudié des instabilités qui peuvent se déclencher dans des coécoulements coeur/écorce faisant intervenir des fluides complexes (polymères, suspensions concentrées), celles-ci peuvent empêcher un contrôle de cette étape ; - le figeage de cette forme : nous avons étudié la gélification de l’alginate (un biopolymère formant un gel par l’ajout d’ions calcium) sous écoulement. Nous avons étudié des phénomènes de diffusion-réaction sous écoulement pour comprendre les points de fonctionnement de nos dispositifs. Une fois ces étapes contrôlées, nous nous sommes intéressés à la fabrication des fibres d’alginates fortement chargées en cellules pour l’ingénierie tissulaire
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35

Callister, Richard D. C. "The in-situ manufacture of a metal-loaded, anisotropically conductive adhesive." Thesis, Brunel University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286803.

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Delevaque, Eric. "Contribution à l'étude de composants actifs à fibre de silice dopée aux ions de terres rares." Lille 1, 1993. http://www.theses.fr/1993LIL10040.

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Cette these traite de l'etude du comportement de composants a fibre de silice dopee aux ions de terres rares. Les fibres dopees sont particulierement attractives comme milieu amplificateur: elles permettent des gains d'amplification superieurs a 40 decibels avec des moyens de pompage compatibles avec la technologie des diodes laser semi-conducteur. Les composants etudies sont: l'amplificateur, le laser et la source superluminescente. Des experiences ont permis de montrer qu'une fraction des ions de terre rare dans les fibres se presente sous forme d'agregats de quelques ions. Ceci constitue un des points fondamentaux de cette etude. Un modele analytique est propose. Sa conception simple a permis la description du comportement des composants et une approche quantitative simplifiee de leur optimisation. Les coupleurs selectifs en frequence sont une des deux innovations technologiques experimentees. Ils ont permis le developpement de l'amplificateur a 1. 55 microns et de la source superluminescente a fibre dopee a l'erbium. Les reseaux de bragg photo-inscrits constituent la seconde innovation. Leurs possibilites ont ete testees sur un laser a fibre dopee au neodyme emettant a 1. 08 microns.

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37

Bergström, Roger. "Fibre flow mechanisms." Doctoral thesis, KTH, Fiber- och polymerteknik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240.

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The flow behaviour, and primarily the floc-floc interaction, of pulp paper suspensions have been studied visually. Analogy models based on these observations have been developed as well as the identification of important parameters of floc break-up in low shear rate flow fields. Floc compressions and the locations of voids (areas of lower fibre concentration) where found to influence the floc splitting mechanism. Based on this investigation an equipment for measuring the load carrying ability of fibre flocs and networks was designed, and the effect of measurement geometry, network structure and fibre suspension concentration was investigated. The load carrying ability with concentration increases rapidly when going from 1% to 2% in initial suspension concentration. A model handling the fibre floc behaviour during extension and compression has been developed, and some basic flocculated flow mechanisms are discussed on an analogy basis. A modified Voigt element is use, describing mainly the compressional behaviour and plastic behaviour of loose fibre network structures. Further the pos- sibility of stress chain formation is discussed on a fibre level as well as on a floc level. The effect of fibre flow (shear field) occurring in the forming zone of a roll former has been studied in detail. Basic forming mechanisms on floc scale has been investi- gated, and the effect of running parameters like dewatering pressure and jet-to-wire speed difference as well as the fibre type and concentration of the pulp suspension has been evaluated. It is evident that floc elongation increases with shear rate (jet-to-wire speed difference) and lower dewatering rate. The latter is because the fibre floc is subjected to the shear field longer due to slower immobilisation. Shorter fibre tends to create weaker networks, which promotes a higher elongation of the flocs.
QC 20100901

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Bergström, Roger. "Fibre flow mechanisms /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240.

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39

Baker, Stephen Ross. "Optical fibre lasers." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239585.

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Travis, Adrian Robert Leigh. "Optical fibre multiports." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254520.

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41

Sherwood, James Lawrence. "Mossy fibre plasticity." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618313.

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This study used extracellular field potential recordings (fEPSP) to investigate the role of kainate receptors (containing GLUK5) in short- and long-term potentiation (S-/L-TP) in the mossy fibre (MF) pathway. In vitro, the role of GLUK5 in synaptic plasticity is dependent on extracellular calcium concentration. So the physiological importance was investigated in vivo. In a single experiment GLUK5 selective antagonist, LY382884 (10 mg.kg-l, i.v.), attenuated STP. Notwithstanding, there is continued controversy regarding the role of GLUK5 in MF synaptic plasticity. Using GLUK5 selective antagonists, LY382884 and ACET, the method of hippocampal slice preparation is identified as deterministic. In parasagittal slices prepared in standard aCSF (PsH), STP, measured as ratio of 1st and 5th pulse (P5:P1) evoked at 25Hz, was antagonised by 10uM LY382884; NMDAR independent L TP, evoked by 100 pulses at 100Hz in 50uM AP5, was reversibly antagonised by 50nM ACET. Transverse hippocampal slices prepared in standard aCSF were not viable. In transverse slices prepared in high sucrose aCSF (TH), 10uM LY382884 had no effect on P5:P1-25Hz or P5:P1-50Hz; furthermore 100nM ACET had no effect on P5:P1-50Hz, or on the induction of NMDAR independent LTP. The depression of transmission by Group II mGluR agonists is reportedly a characteristic MF property. In PsH, DCG-IV had no effect on MF fEPSP but depressed P5:Pt-25Hz. In TH, DCG-IV and LY395756 (mGlu2 selective agonist) transiently depressed MF fEPSP. This was attenuated by a Group U competitive antagonist L Y341495. DCG-IV and LY395756 induced a concentration dependent long-term depression (LTD). While 100nM L Y341495 had no effect on OCGI-IV L TO, 300nM transiently reversed L Y395756 L TO. In conclusion, the pharmacology of synaptic plasticity in vitro is critically dependent on slice preparation; preliminary data suggest that GLUK5 receptors contribute to MF plasticity in vivo. Disparity in EC50 values for DCG-IV and L Y395756 induced depression suggests the possible involvement of mGlu3.

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42

Fraser, Simon G. "Fibre radio transceivers." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406200.

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Bastock, Paul. "Manufacturing novel fibre." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/386650/.

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The work described in this thesis has been funded by the “Engineering and Physical Sciences Research Council’s Centre for Innovative Manufacturing in Photonics” and has been part of the work undertaken by the “Non-Silica Glasses and Related Fibre Technology” work package, within the “Novel Glass and Fibre” group at the Optoelectronics Research Centre. Original contributions to the field include the development of a novel fibre drawing tower, which has allowed over three hundred fibre draws to be accomplished, resulting in composite metal-glass fibre and infrared transmitting fibre manufacturing processes being established. Most significantly, a refined fibre drawing procedure to produce up to 50 km of continuous glass-encapsulated microwire has been created. Fibre has been fabricated with an outer diameter of around 23 μm and inner diameter of around 4 μm, featuring standard deviations of just 2.2 and 0.8 μm for outer and inner diameters respectively, over kilometres of length. A large portion of the work reported in this thesis has been in collaboration with industrial and academic partners, including Rolls Royce, Shell, National Physical Laboratory, Nanyang Technological University, Laboratory of Ultrafast Spectrometry and others. Characterisation of optical materials has founded relationships with many partners including the University of Oxford and SPI Lasers Ltd. Analysis has been carried out for many groups within the Optoelectronics Research Centre, including the Photovoltaic, Compound Glass, Silica Fibre Fabrication and Integrated Photonics groups. Other academic units at the University of Southampton including the ‘Electronics and Computer Science’, Chemistry and ‘Engineering and the Environment’ departments have also had valuable material characterisation performed with the use of the facilities described in this work. Impurity analysis of optical glasses and raw materials has established a relationship with Northern Analytical Laboratory Inc., who has provided continued analysis for the advancing glass melting facility mentioned in this thesis.

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Fox, David Christopher Alexander. "The fire performance of restrained polymer-fibre-reinforced concrete composite slabs." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/17998.

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Composite slab flooring systems for steel-framed buildings consist of a profiled steel deck and a cast in-situ slab. The slab traditionally includes a layer of light gauge steel mesh reinforcement. This mesh is placed near the surface, which controls the early-age cracking caused by concrete drying and shrinkage. The steel mesh also performs a vital structural role at high temperatures. Structural fire tests and numerical investigations over the last 15 years have established that the mesh can provide enhanced fire resistance. A load-carrying mechanism occurs in fire with the mesh acting as a tensile catenary, spanning between perimeter supports. This structural mechanism is currently utilised regularly in the performance-based fire engineering design of steel-framed buildings. In a recent development, this mesh can be removed by using concrete with dispersed polymer fibre reinforcement to form the composite slab. The polymer-fibre-reinforced concrete (PFRC) is poured onto the deck as normal, and the fibres resist early crack development. For developers this technique has several advantages over traditional reinforcing mesh, such as lower steel costs, easier site operations and faster construction. However, to date the fire resistance of such slabs has been demonstrated only to a limited extent. Single element furnace tests with permissible deflection criteria have formed the basis for the fire design of such slabs. But these have not captured the full fire response of a structurally restrained fibre-reinforced slab in a continuous frame. The polymer fibres dispersed throughout the slab have a melting point of 160ºC, and it is unclear how they contribute to overall fire resistance. In particular, there has been no explanation of how such slabs interact with the structural perimeter to maintain robustness at high deflections. This project was designed to investigate the structural fire behaviour of restrained polymer-fibre-reinforced composite slabs. An experimental series of six slab experiments was designed to investigate the effects of fibre reinforcement and boundary restraint. A testing rig capable of recording the actions generated by the heat-affected slab was developed and constructed. Model-scale slab specimens were tested with different reinforcement and perimeter support conditions, to establish the contributions to fire resistance of the polymer fibres and applied structural restraint.

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Petermann, Ingemar. "Fibre Bragg Gratings : Characterization, Realization and Simulation." Doctoral thesis, Stockholm : Department of microelectronics and applied physics, Royal institute of technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4381.

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Farooq, Mohammed. "Development of FRP based composite fibre for fibre reinforced cementitious composites." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57668.

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This thesis describes a method of development of a novel fibre based on fibre reinforced polymers (FRP), for use fibre reinforcement in concrete. Thermosetting epoxy resin matrix were reinforced with E-glass, S-glass, and Carbon fibre to produce different types of composite fibres. The FRP panels were produced using the Vacuum Infusion technique, and then cut to different fibre sizes. The volume fractions of reinforcements within the FRP fibre were controlled by using woven and unidirectional fabrics. The number of layers of reinforcing fibres were also changed, to obtain the optimal thickness of the fibres. The FRP material was characterized by means of tensile tests and microscope image analysis. Four different compositions of FRP were produced with tensile strengths ranging from 195 MPa to 950 MPa. The different combinations in geometry broadened the total number of fibres investigated to 12. Single fibre pullout tests were performed to obtain the fundamental fibre-matrix interfacial bond parameters for the different FRP fibres. The FRP fibres, being hydrophilic, along with having a unique rough surface texture, showed a good bond with cement matrix. A bond strength superior to industrially available straight steel fibres and crimped polypropylene fibres has been observed. The 3 best fibres were then chosen to examine the flexural behaviour FRP fibre reinforced concrete beams. The optimized FRP fibres, one each of Glass FRP and Carbon FRP were then further investigated to study the effect of matrix maturity, temperature, fibre inclination, and loading rate on the fibre-matrix interfacial behaviour using single fibre pullout tests. Scanning Electron Microscope (SEM) analysis was carried out to identify the effect of above-mentioned factors on the surface characteristics of the fibre. An attempt was also made to optimize the fibre-matrix interface to achieve an optimized failure mechanism by coating the fibre with oil. The ability of the fibre to transfer stresses across a cracked section over extended periods has been investigated by means of fibre-relaxation tests. Finally, to assess durability, the fibres were conditioned at high pH and high temperature after which single fibre pullout, direct tension tests, & SEM analysis were conducted.
Applied Science, Faculty of
Civil Engineering, Department of
Graduate

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47

Leung, Ian Kin-Hay Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "Development of composite cavity fibre lasers for fibre laser hydrophone systems." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/41248.

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In this thesis, my main focus was to establish a novel composite-cavity fibre laser (CCFL) and to apply it in sensing, particularly in the hydrophone application. The CCFL that I have proposed is formed by writing three wavelength matched fibre Bragg gratings directly into a continuous length of doped fibre. I have also examined the relative advantages and disadvantages of interferometric and intensity-based hydrophone systems, and have established a hydrophone system that can be switched between the two modes of operation, by making use of digital signal processing. I have established a theoretical model to study the lasing and spectral characteristics of the CCFL. My analysis showed that whilst the CCFL have significantly different phase and threshold conditions from the common semiconductor diode lasers with external cavity, the CCFL also have mode-limiting properties that are often sought after. Through simulations, I was able to identify that a non-uniform straining scheme, that is, when one of the sub-cavities of the CCFL is restrained from strain, can improve the sensitivity with respect to existing single cavity fibre lasers, in both the frequency and intensity domains. My simulations also showed that the sensitivity of such a straining scheme can be optimised by tuning the reflectivity of the gratings, sub-cavity lengths, doping concentration and pump power. I have fabricated multiple CCFLs using the in-house grating writing facilities, and have experimentally assessed their power and spectral related lasing characteristics. Whilst having a significantly longer total cavity length compared to typical fibre lasers, the CCFLs demonstrated stable single longitudinal mode operation and narrow linewidth in the order for a few tens of kHz. Asymmetric output power and frequency as a result of unequal sub-cavity lengths were also examined. Finally, I conducted sensing experiments by applying the CCFLs in strain monitoring and intensity-based hydrophone. My results showed that the non-uniform straining scheme had significantly improved the intensity response of the CCFL, and that the acoustic pressure and frequency can be determined by directly sampling and applying Fourier transform to the output intensity of the fibre laser.

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Bel, Patricia Damian. "Cotton quality - fibre to fabric: fibre properties relationships to fabric quality." University of Southern Queensland, Faculty of Engineering and Surveying, 2004. http://eprints.usq.edu.au/archive/00003193/.

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[Abstract]: The textile industry has a recurrent white speck nep problem in cotton. “White specks” are immature clusters of fibres that are not visible as defects until dyeing, after which they remain white on the surface of a darkly dyed fabric, or appear as non uniform streaks in the fabric. Both results render the fabric unsuitable for commercial fashion fabrics. The white speck potential of cotton is difficult to predict except in extremely immature cottons. Competitive synthetic fibres are uniform in length and strength and never have a maturity problem resulting in dye defects. They are much more predictable in the mill. As a result, cotton faces the risk of being replaced by synthetic fibres. Industry requires a method to predict fabric quality from cotton bale fibre properties to minimize this risk. This research addresses the problem of predicting white specks in dyed cotton fabrics. It is part of a large study, which is supported jointly by US and Australian agencies. The main objective is to predict fabric quality from bale fibre properties given controlled gin and mill processing. Gin and mill processing must be controlled so that field and varietal effects can be seen without the interaction of mechanical processing differences. This results in achieving other objectives, including the provision of baseline data for Australian varieties, ginning effects and comparison of ring and open-end spinning. Initially a reliable method for measuring white specks had to be found. Several systems have been evaluated and are reported here. The systems accuracy was compared using fabrics from the US Extreme Variety Study (EVS), which was grown specifically to have different levels of white specks. The fabrics made from the US (Leading Variety Study 1993 (LVS) and The American Textile Manufacturers Institute (ATMI) Cotton Variety Processing Trials, 2001) and the Australian (1998 & 1999) variety studies were analysed using AutoRate-2-03, the best of the image analysis systems studied. The final release of AutoRate (February 2003) was developed by Dr. Bugao Xu to measure white specks on dark fabrics in conjunction with this research. This final analysis of these studies results in white speck prediction equations from high-speed fibre measurement systems. This information should be immediately useful to as a tool to measure the effects of field and ginning practices on the levels of white specks without having to carry the research out to finished fabrics. Cotton breeders will be able to use the equations in the development of new varieties with low white speck potential, by eliminating varieties with high white speck potential early on. The research will continue on a much larger scale in the US and hopefully a WSP (White Speck Potential) value will be incorporated into the US Cotton Grading System.

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Hilal, Ali Abdullah S. "A fibre-in-fibre bioartificial liver : design studies, development and testing." Thesis, University of Strathclyde, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426349.

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Madden, W. Iain. "Analysis and development of all fibre wavelength selective fibre optic components." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248512.

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Dissertations / Theses on the topic 'Fibre'

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