Dissertations / Theses on the topic 'Fire resistant polymers'

Compared to conventional materials, polymer matrix composites (PMCs) have a number of attractive properties, including light weight, easiness of installation, potential to lower system-level cost, high overall durability, and less susceptibility to environmental deterioration. However, PMCs are vulnerable to fire such that they degrade, decompose, and sometimes yield toxic gases at high temperature. The degradation and decomposition of composites lead to loss in mass, resulting in loss in mechanical strength. This research aims to improve the structural integrity of the PMCs under fire conditions by designing and optimizing a fire retardant nanopaper coating, and to fundamentally understand the thermal response and post-fire mechanical behavior the PMCs through numerical modeling. Specifically, a novel paper-making process that combined carbon nanofiber, nanoclay, exfoliated graphite nanoplatelet, and ammonium polyphosphate into a self-standing nanopaper was developed. The nanopaper was then coated onto the surface of the PMCs to improve the fire retardant performance of the material. The morphology, thermal stability, flammability, and post-fire flexural modulus of the nanopaper coated-PMCs were characterized. The fire retardant mechanism of the nanopaper coating was studied. Upon successfully improving the structure integrity of the PMCs by the nanopaper coatings, a thermal degradation model that captured the decomposition reaction of the polymer matrix with a second kind boundary condition (constant heat flux) was solved using Finite Element (FE) method. The weak form of the model was constructed by the weighted residual method. The model quantified the thermal and post-fire flexural responses of the composites subject to continuously applied heat fluxes. A temperature dependent post-fire residual modulus was assigned to each element in the FE domain. The bulk residual modulus was computed by assembling the modulus of each element. Based on the FE model, a refined Finite Difference (FD) model was developed to predict the fire response of the PMCs coated with the nanopapers. The FD model adopted the same post-fire mechanical evaluation method. However, unlike the FE model, the flow of the decomposed gas, and permeability and porosity of the composites were taken into account in the refined FD model. The numerical analysis indicated that the thickness and porosity of the composites had a profound impact on the thermal response of the composites. The research funding from the Office of Naval Research (ONR) and Federal Aviation Administration Center of Excellence for Commercial Space Transportation (FAA COE AST) is acknowledged.
ID: 031001281; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Adviser: Jihua Gou.; Title from PDF title page (viewed February 26, 2013).; Thesis (Ph.D.)--University of Central Florida, 2012.; Includes bibliographical references (p. 179-198).
Ph.D.
Doctorate
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering

Thesis (M.S.)--University of Alabama at Birmingham, 2008.
Title from PDF title page (viewed Feb. 1, 2010). Additional advisors: Derrick R. Dean, Gregg M. Janowski, Selvum (Brian) Pillay (ad hoc). Includes bibliographical references (p. 76-82).

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.

Fiber reinforced polymeric composites (FRPC) have superior physical and mechanical properties, such as high specific strength, light weight, and good fatigue and corrosion resistance. They have become competitive engineering materials to replace conventional metallic materials in many important sectors of industry such as aircraft, naval constructions, ships, buildings, transportation, electrical and electronics components, and offshore structures. However, since FRPC contain polymer matrix, the polymer composites and their structures are combustible. FRPC will degrade, decompose, and sometimes yield toxic gases at high temperature or subject to fire conditions. The objective of this study is to design and optimize fire retardant nanopaper by utilizing the synergistic effects of different nanoparticles. A paper-making technique that combined carbon nanofiber, nanoclay, polyhedral oligomeric silsesquioxanes, graphite nanoplatelet, and ammonium polyphosphate into self-standing nanopaper was developed. The fire retardant nanopaper was further incorporated into the polymer matrix, in conjunction with continuous fiber mats, through resin transfer molding process to improve fire retardant performance of structural composites. The morphology, thermal stability, and flammability of polymer composites coated with hybrid nanopaper were studied. The cone calorimeter test results indicated that the peak heat release rate of the composites coated with a CNF-clay nanopaper was reduced by 60.5%. The compact char material formed on the surface of the residues of the CNF-clay nanopaper was analyzed to understand the fire retardant mechanism of the nanopaper. The financial support from Office of Naval Research is acklowdged.
M.S.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering MSME

The currently lack of design guidance for pultruded fibre-reinforced polymer member requires more study on their structural behaviours in order to provide structural designer with confidence when applying this material into civil engineering. Elastic lateraltorsional buckling is an important global instability mode of failure for flexure about the major axis of open sections which is characterised by a coupled elastic deformation of lateral deflection and twist about beam’s longitudinal axis. The key elements of this study are laboratory testing, finite element analysis and development of design guidance that is compatible with Eurocode 3 design procedure. 94 tests have been carried out on tensile coupons to characterise the four key material properties for longitudinal, transverse, shear moduli of elasticity and major Poission’s ratio that are required for the prediction of the buckling resistance using closed-form equations and by finite element analysis. 114 tests on the elastic lateral-torsional buckling of I and channel beams under various loading and displacement boundary conditions have been carried out to determine the buckling resistance. Finite element modelling methodology has been developed and both linear and nonlinear numerical analyses have been performed to show that the methodology is suitable. Further sensitivity analysis has been conducted to demonstrate that the buckling resistance is highly influenced by the combination of material, geometric and loading imperfection. A calibration has been implemented, based on the new test results, following the Eurocode 0’s approach to establish the material partial factor for the investigated instability mode of failure.

Les matériaux composites à matrice polymère thermodurcissable interviennent dans de nombreux domaines d’application, parmi lesquels le secteur des transports. Ils présentent toutefois une faible tenue au feu qui limite leur utilisation pour des raisons évidentes de sécurité. De par les restrictions de plus en plus exigeantes de la Commission Européenne (REACH), il existe un réel besoin de se tourner vers des solutions alternatives. Des études récentes ont prouvé l’intérêt des Silsesquioxanes Oligomériques Polyhédriques (POSS) comme agents ignifuges, et particulièrement les POSS portant des ligands phenyl. L’objectif de ce travail a été d’étudier comment la tenue au feu de réseaux hybrides époxy-amine pouvait être améliorée par l’ajout de POSS dans ces matériaux. En faisant varier la nature des comonomères époxydes et amines, ainsi que la structure des POSS sélectionnés, des éléments de réponse ont pu être apportés à la question : existe-t-il une relation structure-propriété en ce qui concerne le comportement au feu des réseaux époxydes ? Des POSS fonctionnels et inertes ont été choisis pour cette étude, et une attention particulière a été portée sur le trisilanolphenyl POSS (POSSOH), pour lequel différents procédés de dispersion ont été mis en œuvre. Il a été montré que l’état de dispersion des POSS était significativement influencé par le type de ligands de ces POSS, mais également par le type de prépolymère époxyde utilisé. En particulier, des structures complexes, jamais observées, ont été découvertes dans les réseaux hybrides basés sur la Tétraglycidyl(diaminodiphenyl) méthane (TGDDM). Des études cinétiques visant à comprendre les interactions développées par les POSS au sein des réseaux ont été menées. Un fort pouvoir catalytique de l’association POSSOH avec un composé à base d’aluminium sur les réactions de réticulation a notamment été mis en évidence. D’autre part, les propriétés thermomécaniques des réseaux finals n’ont pas été modifiées de manière significative par l’ajout de POSS. Finalement, une amélioration remarquable de la tenue au feu a été obtenue dans certains cas, notamment par l’ajout de POSSOH en combinaison avec le composé métallique. La tenue au feu des réseaux à base de TGDDM a été identifiée comme étant liée à un mécanisme d’intumescence
Thermoset polymer composite materials are used in a number of application domains, amongst which the transports sector, but they suffer from poor fire resistance which limits their use for obvious safety and security issues. With the increasingly demanding restrictions from the European Commission, there is a real need to seek for alternative solutions. Recent studies have found the Polyhedral Oligomeric Silsesquioxane (POSS) compounds interesting as fire retardant agents, particularly the POSS bearing phenyl ligands. The present work aimed at investigating how the fire retardancy of hybrid epoxy networks can be improved by incorporating Polyhedral Oligomeric Silsesquioxanes (POSS). In this study, the nature of the epoxy-amine comonomers was varied, as well as the POSS structure. An inert POSS and two multifunctional POSS were selected in order to generate various morphologies. The aim was to answer the question: does a structure-property relationship exist as concerns the fire behaviour of epoxy networks? Particular attention was dedicated to systems containing the trisilanolphenyl POSS (POSSOH) for which different processes of dispersion were implemented. The POSS dispersion state was shown to be greatly influenced by the type of POSS ligands, but also by the epoxy prepolymer nature in the case of the versatile POSSOH. In particular, intricate, never-observed morphologies were discovered in the networks based on Tetraglycidyl(diaminodiphenyl) methane (TGDDM) and containing POSSOH. The study of functional POSS-involving interactions and epoxy-amine kinetics in the model systems revealed the high catalytic power of the combined presence of POSSOH and an aluminium-based catalyst in the model epoxy networks, as well as the occurrence of homopolymerisation. The thermo-mechanical properties were not significantly modified by the addition of POSS. Finally, spectacular improvements in fire retardancy were obtained in some cases, in particular when the POSSOH and the Al-based catalyst were introduced in combination. The fire protection mechanism was attributed to intumescence in the TGDDM-based networks. The addition of POSSOH and the Al-catalyst was found to be efficient in all the epoxy-amine network types, which could not be clearly related to the POSSOH structures but was rather attributed to a chemical synergistic effect

Les matériaux composites à matrice polymères renforcés aux fibres de carbone (PRFC) sont de plus en plus utilisés dans les avions, en raison de leur faible densité et de leurs propriétés mécaniques comparables aux alliages généralement utilisés. Ils sont cependant sensibles aux impacts répétés des particules solides et liquides intervenant au cours du cycle de vol d’un avion, et nécessitent d’être protégés. Cette thèse est inscrite dans ce contexte de protection des PRFC, plus particulièrement ceux à matrice époxy, par le biais de dépôts anti-usure réalisés par projection plasma sous air. De tels recherche ont été menées auparavant avec pour résultats des dépôts céramique et métallique peu adhérents, sur des composites fortement endommagés par le procédé. Les travaux de cette thèse ont donc été organisés autour de deux objectifs :- Objectif fondamental : comprendre les interactions entre les particules fondues et le composite. Grâce à une étude multiéchelles d’impacts de gouttes sur le composite, la résine époxy et sa dégradation thermique ont été identifiés comme responsable de la mauvaise adhérence des dépôts projetés par plasma sur les PRFC.- Objectif expérimental. Déterminer la faisabilité de réaliser un revêtement anti-usure par projection plasma sur PRFC. Deux traitements de surface avant dépôt ont été choisis puis testés, en conditions d’impacts de particules isolées et de formation de dépôts. Des dépôts d’alumine ont pu être obtenus, sans dégradation thermique ou mécanique du composite
Carbon fiber reinforced polymers (CFRP) are increasingly used in aircraft structures, due to their good strength to weight ratio. However, they are more sensitive to the impacts of solid and liquid particles, occurring during the aircraft flight cycle, and thus need to be protected. This work focuses on the protection of carbon fiber reinforced epoxy by air plasma spraying (APS). Numerous studies have been conducted on applying such coatings, but the obtained metallic and ceramic coatings show poor adhesion strength, and the underlying composite material is damaged by the APS process. This PhD is organized around two objectives:- Fundamental objective: understand the interactions between molten particles and the composite. A multi-scale study of droplets impacts on the composite led to identify the epoxy resin as responsible for the poor adhesion strength of air plasma sprayed coatings on CFRPs.- Experimental objective: determine the feasibility of producing an anti-wear coating by plasma spraying on CFRP. Two surface treatments prior to APS were chosen and tested in single particles impacts and coating formation. Alumina coatings have been obtained, without thermal or mechanical degradation of the underlying composite

Sandwich structure is one type of composite materials that has been widely used in automotive, marine and aerospace structures. It offers high specific modulus and specific strength. Sandwich structures consist of two thin face plates that enclose a thick core. The face plate is generally stiff enough to resist bending load, whilst the foam core is of lower modulus, lightweight yet it can transfer the shear and compressive loadings. Sandwich structures with composite faces have been applied to fabricate aerospace structures (e.g., engine cowling, floor panels, etc.) because of their excellent bending stiffness and their resistance to impact (good energy absorption). However, sandwich composites commonly suffer face-core interface failure that could lead to catastrophic failure of the whole structure. This failure would also give a significant increase on its maintenance and repair cost. To alleviate the interface failure between face materials and core, there are several techniques that have been proposed: (a) through-thickness reinforcement by inserting z-pins to connect the faces and the core; (b) insertion of an interleaf (thin layer) which acts as an adhesive between the faces and the core; and (c) matrix modification utilizing polymer nanocomposites (or nanofillers) on the facing materials (which the modified matrix is able to penetrate into the top surface of the core material) to improve face/core interface bonding. The aim of this research is to investigate the improvement level of the face/core interface strength by z-pinning and interleaving. Here, the role of z-pins and interleaves with nanofillers in changing the delamination resistance under mode I (opening mode) was investigated by the double cantilever beam (DCB) test. The results showed improvement in both reinforcement methods on mode I debonding fracture toughness. Cracked sandwich beam (CSB) test was carried out to study the enhancement of fracture resistance of the face-core interface of the structure under mode II (shear loading mode). Almost similar to mode I test, mode II tests also showed a significant improvement in mode II fracture toughness up to 9.5 times in z-pinning. Unlike z-pinning, interleaving did not show a significant result with only 11% improvement at most. Particularly on z-pinning, the increased mode I fracture toughness was achieved by the role of z-pin bridging on crack growth whose effect is controlled by the crack-wake bridging law. Pullout tests were performed to study the bridging law due to the z-pins. The results showed that pullout was dominantly from the face laminates and that the interface bonding between the z-pin and the foam-core was very small and neglected in the analysis. Computer simulation of mode I DCB tests with z-pins was done to compare the model predictions with obtained experimental data.

Orientador: Armando Lopes Moreno Junior
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo
Made available in DSpace on 2018-08-20T12:44:06Z (GMT). No. of bitstreams: 1 Oliveira_ClaytonReisde_D.pdf: 8877102 bytes, checksum: d8520eb5d1f0d3af309830281acd7dfc (MD5) Previous issue date: 2012
Resumo: A técnica de polímeros reforçados com fibras (FRP) vem sendo cada vez mais utilizada como alternativa de reforço estrutural, com o objetivo de aumentar a resistência e a ductilidade das estruturas de concreto armado. Entretanto, o desempenho desses sistemas em situação de incêndio é uma séria preocupação devido ao fato dos materiais de FRPs serem combustíveis. Informações a esse respeito ainda estão restritas à literatura internacional e, mesmo assim, ainda são escassas e limitadas. Assim, antes de serem utilizados, com segurança, em reforços estruturais no interior de edifícios, os FRPs devem ter seu comportamento avaliado em situação de incêndio, verificando tanto o cumprimento dos critérios de resistência ao fogo, especificados em códigos normativos nacionais, quanto procedimentos de dimensionamento dessas estruturas contra a ação do fogo. Este trabalho, inicialmente, reuniu informações disponíveis na literatura internacional sobre os principais efeitos da exposição à altas temperaturas de cada material componente do compósito e, na mesma linha, sobre o comportamento de elementos estruturais reforçados com fibra de carbono em situação de incêndio. A parte experimental do trabalho consistiu na avaliação em laboratório do comportamento de corpos de prova de concreto reforçados com fibra de carbono. As variáveis em análise foram a temperatura limite de exposição do reforço e o tipo de revestimento de proteção ao fogo desses elementos reforçados. Os resultados mostraram que o reforço perde sua eficiência já nos primeiros minutos de exposição ao fogo e que os materiais de proteção, usuais na proteção de elementos de aço, são ineficazes em manter a segurança do sistema FRP em situação de incêndio. Uma simulação computacional via Elementos Finitos, utilizando o software TCD foi feita. Ao final, os resultados deste trabalho confirmaram procedimentos normativos internacionais vigentes que, por unanimidade, enfatizam que durante o incêndio a resistência proporcionada pelo reforço de compósito FRP deve ser desprezada
Abstract: The fiber technique reinforced polymer (FRP) has been used as alternative of structural reinforcement, with the objective to increase the resistance and ductilidade of the reinforcement concrete structures. However, the performance of these systems in fire situation is a serious concern due to the fact of the FRP materials to be combustible. Information to this respect still remain restricted to international literature and, eventhose, still scarced and limited. Thus, before being used, with safety, in structural reinforcements in the interior of buildings, the FRPs must have its behaviour evaluated in fire situation. This paper analyzed the main effects of exposure to high temperatures in FRP systems and investigated this material at laboratory. The main parameter evaluated were the critical temperature of fire exposed and the type of fire coating. The results showed that the reinforcement has lost its efficacy in the first minutes of exposure to fire and protection materials evaluated were ineffective in maintaining the security of the system under fire. Using the software TCD, a computer simulation was generated. At the end, the study confirmed that current code procedures unanimously emphasize: the additional resistance provided by the FRP can not be considered on fire safety design concrete structures
Doutorado
Estruturas
Doutor em Engenharia Civil

Le scellement chimique est une technique d’assemblage structural permettant de connecter et d’assurer le transfert d’efforts entre deux éléments adjacents en béton, à travers le collage d’une armature en acier à l’aide d’une résine polymère. Les scellements chimiques ont été initialement utilisés dans les ouvrages en béton armé pour la rénovation, l’extension et la réparation des structures à travers l’ajout de nouvelles sections de béton aux éléments existants. L’évolution, au fil du temps, des propriétés mécaniques et des propriétés d’adhérence des résines polymères a permis d’améliorer le comportement mécanique des scellements chimiques, leur permettant d’atteindre des propriétés équivalentes ou même supérieures à celles des ancrages mécaniques classiques, à des températures normales de service. Ainsi, les scellements chimiques ont pu progressivement substituer les ancrages mécaniques classiques dans certaines applications, en proposant des solutions plus avantageuses et en offrant plus de flexibilité pour répondre aux exigences architecturales. Cependant, le comportement mécanique des scellements chimiques est principalement gouverné par celui des résines polymères, qui demeurent très sensibles à la variation de la température. Par conséquent, l’augmentation de la température au niveau des scellements chimiques présente un risque potentiel affectant leur sécurité d’utilisation. Par ailleurs, une situation d’incendie présente un danger sérieux qui doit être considéré lors du dimensionnement des scellements chimiques. Récemment, la technique des scellements chimiques, exclusivement utilisée dans les ouvrages en béton armé, a été transférée à la construction des ouvrages bois, sous l’appellation de « goujons collés ». Cette technique, originellement utilisée dans la rénovation et le renforcement des monuments historiques, est aujourd’hui employée dans la construction neuve grâce à la bonne tenue mécanique et séismique et aussi à la possibilité qu’elle offre pour réaliser des assemblages invisibles. Cependant, les goujons collés sont aujourd’hui confrontés aux mêmes problématiques que les scellements chimiques, notamment vis-à-vis l’augmentation de la température. L’objectif de cette thèse est d’étudier l’évolution du comportement mécanique de ces deux systèmes d’assemblages dans le but de proposer une méthode de dimensionnement permettant d’assurer leur tenue structurale en situation d’incendie. L’étude est répartie sur quatre niveaux :i. Etude du comportement des ancrages chimiques à l’échelle des matériaux à travers des essais de caractérisation des constituants de l’ancrage, avec une focalisation particulière sur l’étude des phénomènes se produisant à haute température dans la résine polymère.ii. Etude du comportement global de l’ancrage par le biais d’essais d’arrachement à haute température, à effort constant et à température stabilisée, réalisés sur des scellements chimiques dans des cylindres en béton et des goujons collés dans des parallélépipèdes en lamellé-collé d’épicéa.iii. Etude du comportement mécanique à haute température des ancrages chimiques à l’échelle de la structure à travers la réalisation d’un essai au feu à l’échelle 1 sur une dalle en console ancrée chimiquement dans un mur en béton par 8 scellements chimiques. Les résultats de cet essai ont permis de valider la méthode de dimensionnement proposée pour prédire la durée de résistance au feu des scellements chimiques lors d’une situation d’incendie.iv. Etude théorique portant sur l’évolution de la distribution des contraintes le long de l’ancrage lors d’une variation de la température, à travers le développement d’un modèle non linéaire de cisaillement différé « Shear-lag », permettant d’obtenir les profils théoriques des contraintes pour une distribution thermique quelconque, à partir des données d’entrée expérimentales obtenues par des essais d’arrachement
Post-installation of rebars is a structural joining technique allowing the connection and the load transfer between two neighboring structural elements using steel rebars and adhesive polymers. Post-installed rebars were initially used in concrete constructions in retrofitting, extension and in repairing structures by adding new concrete sections to existing elements. Over the time, the improvement in mechanical and adhesion properties of polymer adhesives have allowed to enhance the mechanical behavior of post-installed rebars and led to achieve equivalent or even higher mechanical responses than cast-in place rebars at normal operating temperatures. Thus, post-installed rebars have gradually replaced cast-in place rebars in new constructions for some applications by offering advantageous solutions and flexibility allowing meeting the high architectural requirements. However, the mechanical behavior of post-installed rebars is essentially governed by the mechanical properties of polymer resins, which remain highly sensitive to temperature variation. Consequently, the temperature increase of the post-installed rebars presents a potential risk affecting their safety use. Therefore, fire presents a serious hazard that should be considered when designing post-installed rebars. Recently, the technique of post-installed rebars, exclusively used in reinforced concrete structures, has been transferred to wood structures construction, and called "glued-in rods". This technique, initially used in the retrofitting and the reinforcement of historical monuments, is today used in new construction thanks to its good mechanical and seismic behavior in addition to the possibility it offers to make invisible connections. However, glued-in rods face the same problems as post-installed rebars, especially concerning the temperature increase. The aim of this thesis is to study the evolution of the mechanical behavior of these two connection techniques in order to suggest a design method allowing ensuring their safe use in a fire situation. The study is divided into four levels:i- Study of the behavior of chemical anchors at the scale of materials through characterization tests performed on the anchor components, with a particular emphasis on the study of phenomena occurring at high temperature in the polymer resin.ii- Study of the global behavior of chemical anchors by means of pull-out tests performed at high temperature, at constant load and at stabilized temperature, carried out on post-installed rebars in concrete cylinders and on glued-in rods in parallelepipeds of spruce glulam.iii- Study of the mechanical behavior at high temperature of chemical anchors at the scale of the structure through a full-scale fire test carried out on a cantilever concrete slab connected to a concrete wall using eight post-installed rebars. Test results were also used to validate the suggested design method to predict the fire resistance duration of post-installed rebars in a fire situation.iv- Theoretical study on the evolution of the stress distribution along the anchor during a temperature variation, through the development of a non-linear shear-lag model, allowing to obtain the theoretical stress profiles for any thermal distribution, from the experimental input data obtained by pull-out tests

The thesis deals with composite systems, with a focus on matrix resistant to extreme conditions. The aim of this work was to research and development matrix, resistant to high temperatures, typical in case of fire. Used theoretical knowledge were realized with subsequent laboratory research. Attention was paid matrices based binder mixed with any alkali activation of alternative raw materials and geopolymers. Scattered reinforcement featured polypropylene fibers. The subject of the practical part of the two alternatives, including a matrix based on basic ingredients - cement, alternative raw materials - high fly ash, blast furnace slag, geopolymer and polymeric components incl. combinations thereof. Laboratory research conducted by determining the fundamental material properties such as density, strengths, etc., after heat exposure. The developed materials were subjected to a temperature 1400 ° C. The conclusion was selected several recipes that were based on the resulting values found to be optimal.

Wood-polymer composite is a relatively new type of material that combines shattered wood mass and a thermoplastic polymer. This material is utilized especially as an alternative to hard wood in the area of non-bearing exterior elements, as it reaches better properties in terms of the basic durability and low maintenance. Raw material composition and processing of the composite enable to provide a significant modification with further matters leading to an improvement of the end-product properties. Research and development in this field focuses predominantly on the utilization of such modifying additives that either enhance the resistance to weathering or are of the recycled nature, as a significant part of the raw material mixture comprises the constituent obtained from non-renewable resources. The aim of the thesis is the evaluation of the influence of the wood-polymer composite modification separately at two levels. First of them is the modification to matrix by using a recycled polymer, the second one comprises the modification of the wood flour with a secondary spherical filler. Both types of modified composites have been assessed in terms pf the prime characteristics and the resistance to adverse ambient.

L’un des enjeux majeurs de la société Nexans est de développer des câbles résistants au feu pour le bâtiment, l’industrie et les réseaux d’infrastructures. Dans ce contexte, un des systèmes développés est un câble électrique dit à isolation tricouche. Le principal désavantage du matériau composite entrant dans la composition de ce câble électrique est son taux de charges important, nécessaire pour obtenir un matériau répondant aux performances électriques et thermiques attendues. Ce haut taux de charges peut constituer un obstacle à la mise en œuvre du matériau du fait de la forte viscosité induite mais aussi détériorer ses propriétés finales comme la flexibilité et la dureté. La stratégie alternative développée visant à réduire le taux de charges introduit et ainsi à diminuer la viscosité des matériaux pour faciliter leur mise en œuvre a été de synthétiser directement les charges dans le polymère en voie fondue. Le procédé sol-gel par lequel une phase inorganique peut être générée in situ pendant le procédé d’extrusion grâce à l’utilisation de précurseurs inorganiques est particulièrement adapté. En effet, les précurseurs inorganiques pourront jouer le rôle de solvant ou plastifiant préalablement à leur réaction, permettant ainsi d’abaisser la viscosité du système complet. De ces observations découle l’objectif principal des travaux de cette thèse qui est de développer des matériaux résistants au feu en intégrant des charges générées in situ par extrusion réactive dans une matrice polymère pré-chargée
One of Nexans' major challenges is to develop fire-resistant cables for buildings, industry and infrastructure networks. In this context, one of the systems developed is a three-layer insulated electric cable. The main disadvantage of the composite material used in the composition of this electrical cable is its high filler content, necessary to obtain a material that meets the expected electrical and thermal performance. This high filler rate can constitute an obstacle to the fabrication process of the material due to the high viscosity induced, but also deteriorate its final properties such as flexibility and hardness. The alternative strategy developed aiming to reduce the filler rate and thus reduce the viscosity of the materials to facilitate their implementation was to synthesize the fillers directly in the molten polymer. The sol-gel process by which an inorganic phase can be generated in situ during the extrusion process through the use of inorganic precursors is particularly suitable. Indeed, the inorganic precursors can play the role of solvent or plasticizer prior to their reaction, thus making it possible to lower the viscosity of the complete system. From these observations stems the main objective of the work of this thesis, which is to develop fire-resistant materials by integrating charges generated in situ by reactive extrusion in a pre-charged polymer matrix

Ce projet de recherche mené en collaboration avec le CTP (Centre Technique du papier) a eu comme objectif de mettre en place une stratégie de greffage de polymères sur des fibres de cellulose via « Chimie Click » dans l’eau et dans des conditions douces et respectueuses de l’environnement afin de conférer de nouvelles propriétés mécaniques aux papiers résultants. La première étape a été d’élaborer une fonctionnalisation alcyne des fibres dans des conditions douces – dans l’eau ou dans un mélange eau/isopropanol – permettant à la fois une fonctionnalisation conséquente tout en préservant la cristallinité de la cellulose, la structure fibre et les propriétés mécaniques. Différentes méthodes de microscopie ont été utilisées pour mieux comprendre l’impact de la fonctionnalisation sur les propriétés mécaniques. Afin d’améliorer les propriétés mécaniques du papier, le greffage sur les fibres de polyéthers d’alkyle fonctionnalisés azoture a été réalisé dans l’eau par cycloaddition de Huisgen d’azoture-alcyne catalysée par le cuivre (II) (CuAAC). Plusieurs polymères de natures différentes (poly(éthylène glycol) et poly[(éthylène glycol)-stat-(propylène glycol)]), de différentes masses molaires et fonctionnalités (mono- ou difonctionnels) ont été liés aux fibres de cellulose. L’ajout de chaînes de poly(éthylène glycol) s’est avéré avoir un effet lubrifiant entraînant une légère diminution de l’indice de traction mais une augmentation importante de la flexibilité du papier. De plus, le greffage de polymères difonctionnels a démontré des propriétés originales de résistance à l’eau sans changer la nature hydrophile des fibres de cellulose. Enfin, le couplage Thiol-Yne a permis de fixer de petites molécules hydrosolubles fonctionnalisées thiol sur des fibres modifiées alcyne en s’affranchissant du cuivre nécessaire à la réalisation de la réaction de CuAAC
This research project, in collaboration with CTP (Centre Technique du Papier), aimed at developing chemical pathway in water to graft polymers on cellulose fibers via “Click Chemistry” in eco-friendly and non-degrading conditions conferring new mechanical properties upon the resulting paper sheets. A first step was to develop a “green” alkyne derivatization method in mild conditions – through pure water or water/isopropanol mixture – allowing for a substantial alkyne functionalization without jeopardizing the cellulose crystallinity, the fiber structure, and maintaining good mechanical properties of the cellulose fibers and resulting paper sheets. To better understand how the functionalization impacts the mechanical properties, several microscopy methods were employed. Then, aiming at improving mechanical properties of the resulting paper, grafting of azidefunctionalized polyoxyalkylenes on alkyne-modified fibers was achieved via Copper(II)-Catalyzed Alkyne-Azide Cycloaddition (CuAAC) in pure water. Water soluble polymers of different nature (poly(ethylene glycol) or poly[(ethylene glycol)-stat-(propylene glycol)]), with different molar mass and functionality (one or two azide groups per macromolecular chain) were successfully attached on cellulose fibers. Grafting of PEG chains involved a slight decrease of the tensile index but a drastic increase of the flexibility of the paper sheet. Interestingly, fibers grafted with difunctional polymers demonstrated an original water resistance maintaining the hydrophilic nature of fibers. Finally, Thiol-Yne reaction was successfully carried out to attach small water soluble thiol-bearing reagents on alkyne-functionalized fibers in water as a metal-free alternative to CuAAC reaction

Les enquêtes récentes sur les séismes ont fait ressortir l'importance des murs en béton armé en tant que partie intégrante des structures. L'évolution des règlements prend en compte ces considérations, par contre le bâti existant doit subir des renforcements dans l'objectif de leur mise en conformité. Dans cette thèse une étude expérimentale faite sur douze murs (six élancés et six courts) renforcés par un collage externe en composite a été conduite. Les murs ont été conçus en étant sous-renforcés à la flexion et cisaillement. Quatre de ces six échantillons ont été renforcés par des bandes de PRFC collées. Deux spécimens, un témoin et un renforcé, ont été soumis à un test de chargement statique et quatre échantillons, l'un témoin et trois rénovés, ont été soumis à des essais de charge cyclique. La discussion et l'analyse des tests incluent la description de la fissuration, l'analyse de la rigidité, de la capacité de charge ultime, de la ductilité.

El reactor anaerobio de membranas sumergidas (SAnMBR) está considerado como tecnología candidata para mejorar la sostenibilidad en el sector de la depuración de aguas residuales, ampliando la aplicabilidad de la biotecnología anaerobia al tratamiento de aguas residuales de baja carga (v.g. agua residual urbana) o a condiciones medioambientales extremas (v.g. bajas temperaturas de operación). Esta tecnología alternativa de tratamiento de aguas residuales es más sostenible que las tecnologías aerobias actuales ya que el agua residual se transforma en una fuente renovable de energía y nutrientes, proporcionando además un recurso de agua reutilizable. SAnMBR no sólo presenta las principales ventajas de los reactores de membranas (i.e. efluente de alta calidad, y pocas necesidades de espacio), sino que también presenta las principales ventajas de los procesos anaerobios. En este sentido, la tecnología SAnMBR presenta una baja producción de fangos debido a la baja tasa de crecimiento de los microorganismos implicados en la degradación de la materia orgánica, presenta una baja demanda energética debido a la ausencia de aireación, y permite la generación de metano, el cual representa una fuente de energía renovable que mejora el balance energético neto del sistema. Cabe destacar el potencial de recuperación de nutrientes del agua residual bien cuando el efluente es destinado a irrigación directamente, o bien cuando debe ser tratado previamente mediante tecnologías de recuperación de nutrientes. El objetivo principal de esta tesis doctoral es evaluar la viabilidad de la tecnología SAnMBR como núcleo en el tratamiento de aguas residuales urbanas a temperatura ambiente. Por lo tanto, esta tesis se centra en las siguientes tareas: (1) implementación, calibración y puesta en marcha del sistema de instrumentación, control y automatización requerido; (2) identificación de los parámetros de operación clave que afectan al proceso de filtración; (3) modelación y simulación del proceso de filtración; y (4) desarrollo de estrategias de control para la optimización del proceso de filtración minimizando los costes de operación. En este trabajo de investigación se propone un sistema de instrumentación, control y automatización para SAnMBR, el cual fue esencial para alcanzar un comportamiento adecuado y estable del sistema frente a posibles perturbaciones. El comportamiento de las membranas fue comparable a sistemas MBR aerobios a escala industrial. Tras más de dos años de operación ininterrumpida, no se detectaron problemas significativos asociados al ensuciamiento irreversible de las membranas, incluso operando a elevadas concentraciones de sólidos en el licor mezcla (valores de hasta 25 g·L-1 ). En este trabajo se presenta un modelo de filtración (basado en el modelo de resistencias en serie) que permitió simular de forma adecuada el proceso de filtración. Por otra parte, se propone un control supervisor basado en un sistema experto que consiguió reducir el consumo energético asociado a la limpieza física de las membranas, un bajo porcentaje de tiempo destinado a la limpieza física respecto al total de operación, y, en general, un menor coste operacional del proceso de filtración. Esta tesis doctoral está integrada en un proyecto nacional de investigación, subvencionado por el Ministerio de Ciencia e Innovación (MICINN), con título ¿Modelación de la aplicación de la tecnología de membranas para la valorización energética de la materia orgánica del agua residual y la minimización de los fangos producidos¿ (MICINN, proyecto CTM2008-06809- C02-01/02). Para obtener resultados representativos que puedan ser extrapolados a plantas reales, esta tesis doctoral se ha llevado a cabo utilizando un sistema SAnMBR que incorpora módulos comerciales de membrana de fibra hueca. Además, esta planta es alimentada con el efluente del pre-tratamiento de la EDAR del Barranco del Carraixet (Valencia, España).
Robles Martínez, Á. (2013). Modelling, simulation and control of the filtration process in a submerged anaerobic membrane bioreactor treating urban wastewater [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34102
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The synthesis, processing, and engineering of low heat release, ultra fire-resistant materials present an important challenge in polymer materials chemistry. One approach to this problem involves the use of materials that char upon decomposition rather than evolve flammable gas. Here, the synthesis and characterization of 1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethene (bisphenol C or BPC) and deoxybenzoin containing polymers are described. Poly(aryletherketone)s containing 1,1-dichloro-2,2-bis(4-hydroxyphenyl)ethene (BPC) were synthesized by the cesium fluoride initiated polymerization of 1,1-dichloro-2,2-bis(4-t-butyldimethylsiloxyphenyl)ethane with 4,4′-difluorobenzophenone (BP-F). These polymers exhibit high char yields by thermogravimetric analysis (TGA), and low heat release capacities were measured by pyrolysis combustion flow calorimetry (PCFC). Poly(aryletherketone)s were prepared from BP-F and various ratios of BPC and bisphenol-A (BPA), and their thermal properties were characterized by TGA and PCFC. Fire-resistant bisphenol C and polydimethylsiloxane (PDMS) polyurethanes were prepared through the polycondensation of 1,1-dichloro-2,2-bis(4-isocyanatophenyl)-ethene (BPC-NCO) with BPC and 2000 g/mol hydroxybutyl-terminated PDMS (PDMS-BuOH). These polyurethanes showed increased char yields based on inclusion of BPC-NCO and PDMS-BuOH, and substantially reduced heat release capacities compared to similar polyurethanes prepared with 2,4-tolylene diisocyanate and poly(tetramethyleneoxide). Halogen-free, fire-resistant copolyarylates were prepared by interfacial copolymerization of isophthaloyl chloride and several relative ratios of 4,4 ′-bishydroxydeoxybenzoin and bisphenol A. The fire-resistance of these polyarylates was explored by TGA and PCFC, and char yields of nearly 40% were observed, twice that of bisphenol A polyarylate. Heat release capacities as low as 81 J/g·K were measured by PCFC. Thus, halogenation, often used to effect fire-resistance in materials, is eliminated all together. Hyperbranched polyphenylenes with bromine and boronic acid termination were prepared by Suzuki coupling polymerization. An exceptionally low heat release capacity of 6 J/g·K were measured by PCFC for bromine terminated polymers and char yields were shown to increase as a function of boronic acid termination due to the formation of a glassy network.

Computational quantum chemistry was used as a tool to predict needed thermochemistry and kinetics for two classes of problems: formation and destruction of NOx pollutants and development of new fire-resistant polymers. Of the latter, polycarbodiimides and polyhydroxyamides (PHA's) were studied. Different methods were used: HF/6-31 G(d), BAC-MP4 (bond-additivity corrections to UMP4 energies and HF vibrational frequencies), PM3 semi-empirical, and combinations. On the NOx problem, work focused on using theory to generate improved kinetics in H2/O2/NOx combustion. The results were a set of thermochemical data and highpressure-limit kinetics for NOx formation and destruction. Hartree-Fock structures and frequencies and fourth-order Moeller-Plesset energies were used for reactions of H/N/O-species involving H1N1O1 , N1O2, N2O1, H1N 2O1, and N2O2 surfaces, including NH + NO ↔ N2O + H, N2O + O ↔ NO + NO, N + OH ↔ NO + H, N + O2 ↔ NO + O, and N + NO ↔ N2 + O. Thermochemical results were discussed in the form of potential energy surfaces. In general, BAC-MP4 heats of formation compared consistently well to literature data. The results generated from this work allowed evaluation of pressure-dependent kinetics and, ultimately, a refined group of reactions for the NOx mechanism. Strengths of particular bonds and bonding combinations in polycarbodiimides were calculated. Work focused on effects of R groups, chain size and stereoregularity on bond dissociation energies (BDE). Specifically, five polycarbodiimide systems were studied: (1) R=R′=H, (2) R=R′ =CH3, (3) R=R′=CH2CH 3, (4) R=CH(CH3)(Phenyl), R′=H, and (5) R=CH(CH3)(phenyl), R′=CH 3. Methyl- and ethyl-substituted polycarbodiimides decreased the bond strength of the central C-N bond. Ligands on the amine (backbone) nitrogen weakened its chain C-N bond dramatically. However, a lower barrier reaction has also been identified. Results imply rapid, concerted unzipping of this polymer, a result consistent with experiment. For the polyhydroxyamide (PHA) system, a model cyclization reaction of PHA to polybenzoxazole (PBO) was evaluated. PHA cyclization to PBO has been studied experimentally, but a detailed theoretical reaction surface has never been evaluated. Moreover, a plausible mechanism by which PHA arrives at PBO had not been previously determined. The calculated overall heat of reaction was thermoneutral, and decomposition was determined to occur at 212°C, compared to the 215°C experimental value. The hydrogen-transfer reaction and a four-center concerted transition-state reaction were found to be the limiting steps.

Fibre reinforced polymer (FRP) materials have been a material of interest in the field of structural engineering due to their superior mechanical properties such as high strength to weight ratios and resistance to environmental degradation and corrosion. Even though research has established the material to be a viable option for construction they are highly susceptible to elevated temperatures. There are several systems available on the market and a great deal of research needs to be conducted to investigate the change in properties and different behaviour at elevated temperature to serve as a better basis for design. The main objective of this project and the experimental program presented in this thesis is to study the thermo mechanical properties of the available systems on the market. A summary of the previous research done in the area covering other materials is presented providing an introduction to the behaviour of different systems under elevated temperature. Then, two different experimental programs are presented. The first considers the glass transition temperature and thermal decomposition of the different systems and the second examines the tensile strength of the different systems under different temperature regimes. The results of both experimental programs are presented and then a connection between the thermo mechanical properties of the resins and the overall strength of the system is established. The research demonstrates that the glass transition temperature of the resin used for an FRP strengthening system is the main determinant of the performance at high temperatures.
Thesis (Master, Civil Engineering) -- Queen's University, 2011-06-16 09:21:32.228

碩士
國防大學理工學院
化學工程碩士班
101
The lowest manufacturing cost , the high effectiveness , the small smog and the lowest poisoned release gases of the intumescent fire retardant coatings were hybrided with Polyurethane , melamine , Organic material and the inorganic materials(such as Mesophase Graphite Powder, Sericite and SiO2). SiO2 was prepared by the sol-gel process. The crystal structures of inorganic component in coating were confirmed by X-ray diffraction(XRD) and the types of functional group were determined with FT-IR .The thermodynamic properties , macrostructure and microstructure of hybrid fire retardant coating were measured by using TGA, DSC,OM and SEM respectively. The results of limiting oxygen index LOI test, UL94 vertical burning test, CNS 7614 flameproof resistance test method and imitation CNS 14705 of flame test show that the paint has reached the second grade and also satisfy the requirement of UL94-V0 level of the flame effect.

碩士
國防大學理工學院
化學工程碩士班
101
In this study, We have choosed waterborne polyurethane and the other organic polymer as organic substrates, pentaerythritol as carbon-formation reagent, ammonium polyphosphate as dehydration agent, melamine as buble-formation reagent to mix with inorganic materials of Al(OH)3 and TiO2 for the preparation of composite fire-resistant coatings. Thermal properties, functional groups and microstructure changes of fire-resistant coatings were be measured using TGA, FTIR and SEM respectively. The X-ray diffractiometer was used to identify the compounds of Al(OH)3 and TiO2. The results of CNS 14705 test reveals that the fire-resistant coating prepared in this study has reached the third degreed of the fire-resistant material.

Concrete-filled steel tubular (CFST) columns, composed of core concrete and outer tubes, have been extensively used as main structural elements in high-rise buildings to carry loads. Due to the composite action between the steel and core concrete, this type of composite construction has been reported to have many constructional and structural benefits, such as easy construction from the omission of formwork, restraint to local buckling of the steel tube provided by the core concrete, high strength, stiffness and ductility. Recently, there is increased interest in adopting CFST columns in composite frame systems. In recent years, fire disasters have frequently been reported worldwide, and seriously threatened personal and public safety. Exposure of concrete and steel to fire will lead to serious structural deterioration and possible failure of columns, thus resulting in local or global collapse of a building. However, in most cases, unprotected CFST columns are not able to maintain structural integrity for sufficient time under fire conditions. External insulating coating or internal reinforcing steel are required to improve the fire resistance of CFST columns, but these two methods tremendously increase the cost of CFST columns and the difficulty of construction. Although ordinary Portland cement (OPC) concrete is classified as a fire-resistant construction material, during fire exposure severe spalling may occur, as well as significant deterioration of strength and stiffness. Therefore, there is a need to find alternative materials to replace OPC to further improve the fire resistance of concrete. Geopolymer is aluminosilicate synthesised from a material of geological origin or industry by-products (e.g. fly ash) with alkaline solutions. In Australia, fly ash is abundantly available from numerous thermal power plants. The use of fly ash to manufacture construction materials can promote the better utilisation of this industry by-product, avoiding disposal into landfill. Previous studies have demonstrated that geopolymer can be successfully used as a binder to make geopolymer concrete. The absence of OPC in geopolymer concrete (GPC) can significantly reduce CO2 emissions for the construction industry. Recent research has proved that GPC has substantially better fire performance than OPC concrete. Therefore, GPC has the potential to be used in CFST columns to improve their fire performance. So far, very little research has been conducted to investigate the behaviour of geopolymer concrete-filled steel tubular (GCFST) columns, and this research aims to address this knowledge gap. In this thesis, salient parameter analysis of GPC mix was conducted based on the Taguchi method, and three optimised GPC mix designs were proposed. Material properties such as slump, density, Young’s modulus, compressive strength, flexural strength and splitting tensile strength were experimentally studied. The measured values of Young’s modulus, flexural strength and splitting tensile strength of GPC are compared favourably to the predictions of existing standards. The measured hot strength and displacement of GPC under combined loading and elevated temperature were reported. Full-range stress-strain curves of GPC and reference OPC after exposed to elevated temperatures were evaluated. The results further confirm that GPC has the potential to improve the fire performance of CFST columns. A total of 15 tests were carried out on GCFST columns and conventional CFST columns to compare their behaviours. The main experimental parameters included: (1) Concrete type (geopolymer concrete and OPC concrete); (2) Curing procedure of GPC (ambient curing and elevated temperature curing); (3) Strength of geopolymer concrete (37.4, 58.6 and 68.4 MPa); (4) Test method (tested at ambient temperature, in fire, or after fire exposure). The axial load, axial strain and lateral strain were measured for ambient temperature tests and residual property tests. The axial displacement versus the temperature curves were recorded for the specimens tested under combined load and temperature increase. The results were compared to predictions of numerical models developed with ABAQUS, and the agreement between them is reasonable. This research confirms that the behaviour of GPC at an ambient temperature is comparable to that of OPC concrete at an ambient temperature. However, GPC has better fire performance and a higher post-fire residual strength than OPC concrete. This study has proved the potential of using GPC as fire-resistant concrete in CFST columns. Thus, the use of external insulating coating or internal reinforcing steel could be potentially eliminated for CFST columns.

Research Doctorate - Doctor of Philosophy (PhD)
Inserting fibre reinforced polymer (FRP) strips into pre-cut grooves in the surface of masonry walls is an emerging technique for the retrofit of unreinforced masonry (URM) structures. This method, known as near surface mounting (NSM), provides significant advantages over externally bonded FRP strips in that it has less of an effect on the aesthetics of a structure and can sustain higher loading before debonding. As this technique is relatively new, few studies into the behaviour of masonry walls strengthened using this technique have been conducted. A combined experimental and numerical program was conducted as part of this research project to study the in-plane shear behaviour of masonry wall panels strengthened with NSM carbon FRP (CFRP) strips. In this project the FRP strips were designed to resist sliding along mortar bed joints and diagonal cracking (through mortar joints and brick units). Both of these failure modes are common to masonry shear walls. Different reinforcement orientations were used, including: vertical; horizontal; and a combination of both. The first stage of the project involved characterising the bond between the FRP and the masonry using experimental pull tests (18 in total). From these tests the bond strength, the critical bond length and the local bond-slip relationship of the debonding interface was determined. The second stage of the project involved conducting diagonal tension/shear tests on masonry panels. A total of four URM wall panels and seven strengthened wall panels were tested. These tests were used to determine: the effectiveness of the reinforcement; the failure modes; the reinforcement mechanisms; and the behaviour of the bond between the masonry and the FRP in the case of a panel. The third stage of the project involved developing a finite element model to help understand the experimental results. The masonry was modelled using the micro-modelling approach, and the FRP was attached to the masonry model using the bond-slip relationships determined from the pull tests. Reinforcement schemes in which vertical FRP strips were used improved the strength and ductility of the masonry wall panels. When only horizontal strips were used to reinforce a wall panel, failure occurred along an un-strengthened bed joint and the increase in strength and ductility was negligible. The vertical reinforcement prevented URM sliding failure by restraining the opening (dilation) of the sliding cracks that developed through the mortar bed joints. The finite element model reproduced the key behaviours observed in the experiments for both the unreinforced and FRP strengthened wall panels. This model would potentially be useful for the development of design equations.

Research Doctorate - Doctor of Philosophy (PhD)
Inserting fibre reinforced polymer (FRP) strips into pre-cut grooves in the surface of masonry walls is an emerging technique for the retrofit of unreinforced masonry (URM) structures. This method, known as near surface mounting (NSM), provides significant advantages over externally bonded FRP strips in that it has less of an effect on the aesthetics of a structure and can sustain higher loading before debonding. As this technique is relatively new, few studies into the behaviour of masonry walls strengthened using this technique have been conducted. A combined experimental and numerical program was conducted as part of this research project to study the in-plane shear behaviour of masonry wall panels strengthened with NSM carbon FRP (CFRP) strips. In this project the FRP strips were designed to resist sliding along mortar bed joints and diagonal cracking (through mortar joints and brick units). Both of these failure modes are common to masonry shear walls. Different reinforcement orientations were used, including: vertical; horizontal; and a combination of both. The first stage of the project involved characterising the bond between the FRP and the masonry using experimental pull tests (18 in total). From these tests the bond strength, the critical bond length and the local bond-slip relationship of the debonding interface was determined. The second stage of the project involved conducting diagonal tension/shear tests on masonry panels. A total of four URM wall panels and seven strengthened wall panels were tested. These tests were used to determine: the effectiveness of the reinforcement; the failure modes; the reinforcement mechanisms; and the behaviour of the bond between the masonry and the FRP in the case of a panel. The third stage of the project involved developing a finite element model to help understand the experimental results. The masonry was modelled using the micro-modelling approach, and the FRP was attached to the masonry model using the bond-slip relationships determined from the pull tests. Reinforcement schemes in which vertical FRP strips were used improved the strength and ductility of the masonry wall panels. When only horizontal strips were used to reinforce a wall panel, failure occurred along an un-strengthened bed joint and the increase in strength and ductility was negligible. The vertical reinforcement prevented URM sliding failure by restraining the opening (dilation) of the sliding cracks that developed through the mortar bed joints. The finite element model reproduced the key behaviours observed in the experiments for both the unreinforced and FRP strengthened wall panels. This model would potentially be useful for the development of design equations.

No
An extensive study of the fibre orientation structures developed in a transverse ribbed plate during injection moulding, and the use of these structures to investigate the effect of local fibre orientation state on crack initiation resistance, is reported. The fibre orientation results for the ribbed plate, measured using large area image analysis system developed at Leeds University, showed that after an initial settling down period, the central core region, where the fibres are aligned perpendicular to the flow direction, decreased in size monotonically, with an associated monotonic increase in the outer shell regions, where the fibres are aligned preferentially along the injection direction. Interestingly, the level of orientation in the two regions remained almost constant: only the proportions of the two regions were found to change with flow length. Across the plate, close to the gate, the central core region was found to have a lens-like shape, while at the other end of the plate the core was thinner and also consistent in thickness across the sample width. The transverse rib was found to cause little disturbance to the fibre orientation of the base plate. The different proportions of the shell and core regions at different locations over the ribbed plate provided an ideal case to test the proposition of Friedrich that the crack resistance of a short fibre reinforced material depends on the number of fibres that are perpendicular to the crack tip. The impact test results gathered in this way confirmed this hypothesis of Friedrich.