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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

A Method for Winding Advanced Composites of Unconventional Shapes using Continuous and Aligned Fibers

Allen, Abraham K. 03 December 2004 (has links) (PDF)
Advanced composites are extremely strong, rigid, and light, even when compared with advanced metals. Advanced composites are replacing high-tech metals as the material of choice for aerospace engineering. However, the processes used to manufacture advanced composites generally lose some of the properties of the materials by their process limitations. One process that keeps the theoretically awesome qualities of the composite materials in tact is filament winding. Filament wound parts are used as rocket shells, bicycle frame tubes, drive shafts, pressure vessels, etc. Filament winding is an automated process and makes reliable parts to close tolerances. If a straight tube were to be made by all the existing composites manufacturing processes, filament wound tubes would be significantly better than any other. However, filament winding is generally limited to making straight tubes. A new process based on filament winding is proposed; one that can wind complex shapes of the same high quality as conventional filament winding. This process has achieved this by winding continuous, uncut, and aligned fibers. This process is called Lotus Filament Winding.
32

[en] DIGITAL MICROSCOPY AND IMAGE ANALYSIS FOR THE CHARACTERIZATION OF FILAMENT WOUND COMPOSITE PIPES / [pt] MICROSCOPIA DIGITAL E ANÁLISE DE IMAGENS PARA CARACTERIZAÇÃO DE TUBOS COMPÓSITOS FABRICADOS POR ENROLAMENTO FILAMENTAR

JULIA GOMES AZARA DE OLIVEIRA 28 October 2008 (has links)
[pt] Tubos de material compósito - matriz polimérica reforçada por fibra de vidro - fabricados pela técnica de enrolamento filamentar, foram caracterizados através de microscopia eletrônica digital e processamento de imagens. Três tubos foram fabricados em equipamento próprio seguindo parâmetros de enrolamento similar. Um tubo comercial fabricado por empresa especializada, com parâmetros de enrolamento mais complexos, também foi caracterizado. Para tal, seções circunferenciais foram observadas em um microscópio eletrônico de varredura com captura digital de imagem. Mosaicos de imagens foram gerados, permitindo obter informação com boa resolução local e, simultaneamente, grande abrangência espacial. Assim, foi possível realizar uma caracterização que abrangia desde o tamanho e forma de fibras individuais até a distribuição espacial de milhares de fibras em uma vasta área da amostra. Foram cridas rotinas de processamento e análise de imagens para medir dados como diâmetro, fator de forma, fração volumétrica e ângulo de enrolamento de fibras. Além disso, uma rotina específica foi desenvolvida para a identificação automática das várias camadas de fibras presentes no tubo comercial. / [en] Pipes made from composite material - polymer matrix reinforced with glass fibers - manufactured by filament winding, were characterized by scanning electron microscopy and image analysis. Three pipes were manufactured with equipment owned by the research group, following similar winding parameters. A commercial tube made by a specialized company, with more complex winding conditions, was also characterized. Circumferential sections were observed in a scanning electron microscope with digital image acquisition. Image mosaics were created, providing information with good spatial resolution and, at the same time, wide spatial coverage. Thus, it was possible to characterize size and shape of individual fibers and, simultaneously, obtain the spatial distribution of thousands of fibers within a large sample area. Image processing and analysis routines were created to measure fiber diameter, shape factor, area fraction and winding angle. A specific routine was developed for the automatic identification of the several fiber layers present in the commercial pipe.
33

Investigation Of The Effect Of Semi-geodesic Winding On The Vibration Characteristics Of Filament Wound Shells Of Revolution

Ibrahimoglu, Can Serkan 01 September 2010 (has links) (PDF)
In this thesis, the effect of semi-geodesic winding on the free vibration characteristics of filament wound composite shells of revolution with variable radii of curvature is studied. The analysis is performed by a semi-analytical solution method which is based on the numerical integration of the finite exponential Fourier transform of the fundamental shell of revolution equations. The governing equations for the free vibration analysis are initially obtained in terms of fundamental shell variables, and they are reduced to a system of first order ordinary differential equations by the application of finite exponential Fourier Transform, resulting in a two point boundary value problem. The boundary value problem is then reduced to a series of initial value problems, and the multisegment numerical integration technique is used in combination with the frequency trial method in order to extract the natural frequencies and determine the mode shapes within a given range of natural frequencies. Previous studies on geodesic winding is extended such that the effect of semi-geodesic winding which rely on the preset friction between the fiber and the mandrel surface on the stiffness and vibration characteristics of filament wound shells of revolution is investigated. Additionally, finite element analysis is employed to compare the results obtained from semi-analytical model solved by numerical integration and finite element model solved by finite element method. Sample results are obtained for filament wound truncated conical and spherical shells of revolution and the effect of the winding pattern on the vibration characteristics of shells of revolution is investigated thoroughly.
34

Tubula??es de PRFV com adi??o de areia quartzosa visando sua aplica??o na ind?stria do petr?leo

Barros, Gustavo de Ara?jo 19 January 2007 (has links)
Made available in DSpace on 2014-12-17T14:58:25Z (GMT). No. of bitstreams: 1 GustavoAB.pdf: 2461248 bytes, checksum: 0536be02b6961005820ca67a7e2765de (MD5) Previous issue date: 2007-01-19 / Fillers are often added in composites to enhance performance and/or to reduce cost. Fiberglass pipes must meet performance requirements and industrial sand is frequently added for the pipe to be cost competitive. The sand is added to increase pipe wall thickness, thus increase pipe stiffness. The main goal of the present work is to conduct an experimental investigation between pipes fabricated with and without de addition of sand, to be used in the petroleum industry. Pipes were built using E-glass fibers, polyester resin and siliceous sand. The fabrication process used hand lay up and filament winding and was divided in two different parts: the liner and the structural wall. All tested pipes had the same liner, but different structural wall composition, which is the layer where siliceous sand may be added or not. The comparative investigation was developed considering the results of longitudinal tensile tests, hoop tensile tests, hydrostatic pressure leak tests and parallel-plate loading stiffness tests. SEM was used to analyze if the sand caused any damage to the glass fibers, during the fabrication process, because of the fiber-sand contact. The procedure was also used to verify the composite conditions after the hydrostatic pressure leak test. The results proved that the addition of siliceous sand reduced the leak pressure in about 17 %. In the other hand, this loss in pressure was compensated by a stiffness increment of more than 380 %. MEV analyses show that it is possible to find damage on the fiber-sand contact, but on a very small amount. On most cases, the contact occurs without damage evidences. In summary, the addition of sand filler represented a 27.8 % of cost reduction, when compared to a pipe designed with glass fiber and resin only. This cost reduction combined to the good mechanical tests results make siliceous sand filler suitable for fiberglass pressure pipes / Cargas de adi??o s?o utilizadas com freq??ncia, em materiais comp?sitos, para atingir propriedades mec?nicas requeridas por normas e para redu??o de custos. As tubula??es em pl?stico refor?ado com fibras de vidro (PRFV), utilizadas para aplica??es com altas press?es, devem atender a requisitos m?nimos de projeto estabelecidos em normas. Para tanto, a areia vem sendo utilizada como carga de adi??o, no sentido de manter os tubos em PRFV competitivos no mercado. A areia ? adicionada para aumentar a espessura da parede, aumentando com isso a rigidez. Este trabalho teve como principal objetivo analisar a influ?ncia da areia nas propriedades mec?nicas de tubula??es de PRFV, visando sua aplica??o na ind?stria do petr?leo e do g?s, atrav?s de ensaios comparativos entre tubos com e sem a adi??o de areia. Os tubos foram fabricados com fibras de vidro tipo E na forma de fios cont?nuos e manta, resina poli?ster ortoft?lica e areia quartzosa. A fabrica??o foi realizada em duas etapas distintas, sendo a primeira camada do tubo denominada de barreira qu?mica (processo de lamina??o manual) e a segunda camada denominada estrutura (fabricada pelo processo de filamento cont?nuo). A areia ? adicionada no tubo juntamente com as camadas de filamento cont?nuo e, portanto, ? um constituinte da estrutura do tubo. A an?lise comparativa foi conduzida atrav?s de ensaios de tra??o axial e ircunferencial, press?o hidrost?tica e rigidez, al?m de an?lises com microsc?pio eletr?nico de varredura (MEV). Foram avaliadas as for?as resultantes de ruptura e o m?dulo de elasticidade circunferencial, al?m da rigidez. As an?lises com MEV foram conduzidas para verificar a presen?a de danos causados as fibras, durante o processo de fabrica??o, e para verificar as condi??es do laminado ap?s os ensaios de press?o hidrost?tica. Os resultados mostraram que a adi??o de areia causou uma redu??o na press?o de ruptura do tubo de 17 %. Por?m esta perda foi compensada pelo grande acr?scimo na rigidez que foi da ordem de 380 % . As an?lises no MEV mostraram que ocorrem danos durante o processo de fabrica??o, mas em quantidades muito pequenas. Na maioria dos casos o contato areia/fibras ocorre sem evid?ncias de danos. Em resumo, a areia representa uma redu??o de 27,8 % no custo final do tubo, que somado aos bons resultados obtidos nos ensaios mec?nicos, faz deste material uma excelente op??o de carga de adi??o para tubula??es de PRFV utilizadas com altas press?es
35

Caractérisation des structures composites bobinées épaisses, application à l’étude du comportement de réservoirs de stockage d’hydrogène

Pilato, Aurélie 09 December 2011 (has links)
Ce travail de thèse s'est déroulé dans le cadre du programme H2E (Horizon Hydrogène Énergie) piloté par Air Liquide et en partenariat industriel avec Composites Aquitaine. Le stockage d’hydrogène sous forme gazeuse impose que les réservoirs bobinés en composite carbone/époxy utilisés résistent à des pressions internes en service allant de 350 à 700bar.L’état de l’art montre que le procédé d’enroulement filamentaire et son application à des épaisseurs de matériaux composites importantes peuvent générer des variations, dans l’épaisseur, des contraintes résiduelles d’origine thermique, de la teneur en fibres et en porosités et de l’épaisseur des couches. Ces hétérogénéités peuvent alors être à l’origine de modifications des propriétés mécaniques du composite. Notre travail s’est donc appuyé sur la caractérisation physico-chimique à l’échelle des constituants (mesure de températures, nano-indentation, analyse d’images et microtomographie) ainsi que la caractérisation mécanique à l’échelle de la couche de référence mais également à l’échelle de la structure (essais plans spécifiques sur éprouvettes bobinés et essais hors-plan).Les hétérogénéités de la matière ainsi identifiées sur le réservoir ont été intégrées dans un modèle de calcul analytique permettant d'étudier leurs influences sur sa pression d'éclatement. La conception d'un essai de mise sous pression interne d'un anneau a par ailleurs permis de vérifier le comportement mécanique de la structure réelle. / This PhD work was conducted in the H2E (Horizon Hydrogen Energy) program coordinated by Air Liquide and with the industrial partnership of Composites Aquitaine. The hydrogen storage under gaseous form needs the filament-wound carbon/epoxy composite vessels used to resist to service pressures between 350 to 700bar.The influences of the process and of the thickness of the structure on its mechanical behaviour were determined by precise bibliographic work and were supposed to generate thermal residual stresses and also to be responsible of variations in the thickness and fibre content of the plies. These heterogeneities could modify the mechanical properties of the composite material. Our work focuses, first of all, on the physical chemistry characterization at the constituents scale (temperature measurement, nano-indentation, image analysis and microtomography) and then on the mechanical characterization of the reference ply and also of the structure (dedicated tests on filament-wound samples and out-of-plane tests).The material heterogeneities identified on the vessel were integrated in an analytical calculation model to study their influences on its burst pressure. The development of an internal pressure test allows us to verify the global mechanical behaviour of the real structure.
36

[en] CILINDRICAL DEFECTS INFLUENCE ON THE TENSILE STRENGTH OF FIBERGLASS REINFORCED VINYL ESTER COMPOSITE RINGS / [pt] INFLUÊNCIA DE DEFEITOS CILÍNDRICOS SOBRE O LIMITE DE RESISTÊNCIA DE ANÉIS DE RESINA ÉSTER VINÍLICA REFORÇADA COM FIBRAS DE VIDRO

EGBERT NASCIMENTO BUARQUE 11 February 2005 (has links)
[pt] Em Influência de defeitos cilíndricos sobre o limite de resistência de anéis de resina éster vinílica reforçada com fibras de vidro é realizado um estudo da influência de defeitos sobre a resistência mecânica de um tubo compósito de resina vinil éster reforçada com fibras de vidro picadas e contínuas. Os defeitos, com geometria cilíndrica, são artificialmente fabricados e têm suas dimensões (raio e profundidade) variados. A resistência mecânica do material foi avaliada através do ensaio de tração de anéis previsto na norma ASTM D 2290. Os resultados são analisados pelo método da ANOVA, obtendo-se, assim, a significância das variáveis relacionadas ao defeito (raio e profundidade). Realiza-se também a modelagem por elementos finitos do ensaio de tração, a fim de se avaliar o comportamento mecânico do material durante o ensaio. / [en] Cilindrical defects influence on the tensile strength of fiberglass reinforced vinyl ester composite rings investigates the influence of defects on the mechanical strength of a fiberglass reinforced vinylester composite pipe. The defects are manufactured in cilindrical shape with dimensions (radius and depth) varying over a selected range. The samples are tested in accordance with the ASTM D 2290 standard and the results are analyzed by the ANOVA method. A finite element model of the test is made in order to investigate the mechanical behaviour of the material during testing.
37

Étude de la durabilité d'un matériau composite bobiné sous chargements sévères / Study of the durability of a wound composite material under severe loads

Crozatier, Mathilde 13 April 2017 (has links)
Les matériaux composites sont très étudiés depuis des décennies. En effet, l'alliance entre légèreté et résistance de ces structures entraîne le développement de leur utilisation. Leur caractérisation reste un point essentiel dans la plupart des études.Ce travail s’inscrit dans le projet Sollicitern qui vise à concevoir un camion d’hydrocurage en matériaux composites, financé par un fond unique interministériel. L’objectif est d’étudier la durabilité du matériau composite retenu sous chargements sévères. Elle permettra ainsi d’alimenter les modèles numériques des partenaires industriels afin d’ajuster les paramètres pour l’optimisation de la citerne et également d’estimer sa durée de vie face à ces diverses sollicitations.Dans un premier temps, l’attention se porte sur l’intégration de la courbure de la structure et donc du matériau dans l’étude. En effet, ce dernier est fabriqué par enroulement filamentaire, ce qui génère nécessairement une structure tubulaire. Dans un second temps, une caractérisation statique est menée. Cette partie comporte notamment des essais de compression radiale sur l’ensemble de la structure tubulaire où un protocole expérimental est mis en œuvre. En couplant les résultats de ces essais avec ceux d’une simulation numérique reproduisant l’essai, les propriétés élastiques du pli unidirectionnel sont accessibles grâce à une optimisation. Dans un troisième et dernier temps, la durabilité plus spécifique est abordée. Des campagnes d’essais de fatigue, d’impacts, d’usure et de vieillissement sont tout d’abord réalisées indépendamment les unes des autres. L’objectif final est de coupler ces différentes sollicitations et d’appréhender ainsi leur effet combiné. / Composites materials have been studied for decades. Indeed, the association between lightness and resistance of these structures leads to the development of their use. Their characterization remains an essential point in most researches.This work is part of Sollicitern project, which aims to design a composite water treatment truck, financed by a single interministerial fund. The aim is to study the durability of the composite material retained under severe loads. It thus offers tools to industrialists for adjusting parameters in the tank optimization and the estimation of the lifetime under these various loadings.In the first stage, attention is focused on the integration of the curvature of the structure and therefore of the material in the study. Indeed, it is manufactured by filament winding, which necessarily generates a tubular structure. In a second step, a static characterization is carried out. This part includes, in particular, radial compression tests on the whole tubular structure where an experimental protocol is developed. By coupling the results of these tests with a numerical simulation reproducing the test, the elastic properties of the unidirectional ply are obtained by optimization. In a third and final stage, more specific durability is discussed. Fatigue, impact, wear and aging tests are first carried out independently of one another. The final objective is to associate these different loadings and thus to apprehend their combined effect.
38

Experimental study on compressive behavior and failure analysis of composite concrete confined by glass/epoxy ±55° filament wound pipes

Gemi, L., Koroglu, M.A., Ashour, Ashraf 21 December 2017 (has links)
Yes / This paper investigates the strength and ductility of concrete confined by Glass/Epoxy ±55° Filament Wound Pipes (GFRP) under axial compression. A total of 24 cylinderical specimens were prepared with expansive and Portland cements, properly compacted and un-compacted for different composite fresh concrete matrix. Test results showed that compressive strength and axial deformation at failure of concrete confined with GFRP tubes increased by an average of 2.85 and 5.57 times these of unconfined concrete, respectively. Macro and micro analyses of GFRP pipes after failure were also investigated. Debonding, whitening, matrix/transfer cracking, delamination and splitting mechanisms were detected at failure, respectively. The experimental results were also employed to assess the reliability of design models available in the literature for confined concrete compressive strength.
39

Flexural behaviour of rectangular FRP tubes fully or partially filled with reinforced concrete / Comportement en flexion de tubes en PRF rectangulaires entièrement ou partiellement remplis de béton armé

Soliman, Ahmed Mohamed Abouzied January 2016 (has links)
Abstract: Recently, fiber-reinforced polymer (FRP) composite materials have been used in the field of civil engineering constructions especially in corrosive environments. They can be used as internal reinforcement for beams, slabs, and pavements, or as external reinforcement for rehabilitation and strengthening different structures. One of their innovative applications is the concrete-filled FRP tubes (CFFTs) which are becoming an alternative for different structural members such as piles, columns, bridge girders, and bridge piers due to their high performance and durability. In such integrated systems, the FRP tubes act as stay-in-place forms, protective jackets for the embedded concrete and steel, and as external reinforcement in the primary and secondary direction of the structural member. Extensive research was developed on CFFTs as columns, but comparatively limited research was carried out on CFFTs as beams especially those with rectangular sections. The circular sections exhibit magnificent confinement efficiency in case of columns. However, the rectangular sections have higher moment of inertia and flexural stiffness to resist the applied loads and deformations in case of beams. Moreover, the construction and architectural requirements prefer the rectangular section of beams, rather than the circular beams, due to its stability during installation and its workability during connecting to other structural members like slabs and columns. Also, CFFTs that are completely filled with concrete are not optimal for applications governed by pure bending, because the excess weight of the cracked concrete below the neutral axis may increase the transportation and installation cost. This dissertation presents experimental and theoretical investigations on the flexural behaviour of rectangular CFFT beams with steel rebar. These hybrid FRP-concrete-steel tubular rectangular beams contain outer rectangular filament-wound glass-FRP (GFRP) tubes to increase the sectional moment of inertia, to provide flexural and shear reinforcement, and to protect the inner structural elements (concrete and steel) against corrosion. The outer tubes were fully-or-partially filled with concrete and were reinforced with steel rebar at the tension side only. Inner hollow circular or square filament-wound GFRP tubes, shifted toward the tension zone, were provided inside the CFFT beam to eliminate the excess weight of the cracked concrete at the tension side, to confine actively the concrete at the compression side and to act as reinforcement at the tension side. The surfaces of tubes adjacent to concrete were roughened by sand coating to fulfill the full composite action of such hybrid section. Several test variables were chosen to investigate the effect of the outer and inner tubes thickness, fibers laminates, and shape on the flexural behaviour of such hybrid CFFT beams. To fulfil the objectives of the study, twenty-four full-scale beam specimens, 3200 mm long and 305×406 mm2 cross section, were tested under a four-point bending load. These specimens include eight fully-CFFT beams with wide range of tube thickness of 3.4 mm to 14.2 mm, fourteen partially-CFFT beams with different outer and inner tubes configurations, and two conventional steel-reinforced concrete (RC) beams as control specimens. The results indicate outstanding performance of the rectangular fully and partially-CFFT beams in terms of strength-to-weight ratio and ductility compared to the RC beams. The fully-CFFT beams with small tube thickness failed in tension by axial rupture of fibers at the tension side. While, the fully-CFFT beams with big tube thickness failed in compression by outward buckling of the outer tube compression flange with warning signs. The results indicate also that the flexural strength of the fully-CFFT beams was ascending nonlinearly with increasing the tubes thickness until a certain optimum limit. This limit was evaluated to define under-and-over-reinforced CFFT sections, and consequently to define the tension and compression failure of fully-CFFT beams, respectively. The inner hollow tubes act positively in reinforcing the partially-CFFT beams and confining the concrete core at the compression side. The strength-to-weight ratio of the partially-CFFT beams attained higher values than that of the corresponding fully-CFFT beams. Generally, the partially-CFFT beams failed gradually in compression due to outward buckling of the outer tube compression flange with signs of confining the concrete core at the compression side. The inner circular voids pronounced better performance than the square inner voids, however they have the same cross sectional area and fiber laminates. Theoretical section analysis based on strain compatibility/equilibrium has been developed to predict the moment-curvature response of the fully-CFFT section addressing the confinement and tension stiffening of concrete. The analytical results match well the experimental results in terms of moment, deflection, strains, and neutral axis responses. In addition, analytical investigation was conducted to examine the validity of the North American design codes provisions for predicting the deflection response of fully and partially-CFFT beams. Based on these investigations, a new power and assumptions were proposed to Branson’s equation to predict well the effective moment of inertia of the CFFT section. These assumptions consider the effect of the GFRP tube strength, thickness and configuration, in addition to the steel reinforcement ratio. The proposed equations predict well the deflection in the pre-yielding and post-yielding stages of the hybrid FRP-concrete-steel CFFT rectangular beams. / Résumé: Les matériaux composites en polymère renforcé de fibres (PRF) ont récemment été utilisés dans le domaine des constructions de génie civil, en particulier dans les environnements corrosifs. Elles peuvent être utilisées comme une armature interne pour des poutres, dalles et les trottoirs, ou comme une armature externe pour la réhabilitation et le renforcement de différentes structures. L'une de leurs applications novatrices est les tubes de polymères renforcés de fibres remplis de béton (TPFRB ) qui sont en train de devenir une alternative pour divers éléments structuraux tels que les pieux, les colonnes, les poutres et les piliers de ponts en raison de leur haute performance et durabilité. Dans de tels systèmes intégrés, les tubes PRF agissent comme un coffrage permanent, une chemise protectrice pour le béton et l'acier encastrés, et comme une armature externe dans les directions longitudinale et transversale de l'élément structural. La recherche a été concentrée sur les TPRFB comme des colonnes, mais très peu de recherche a été effectué les TPRFB comme des poutres particulièrement celles à section rectangulaire. La section circulaire présente une efficacité de confinement efficace en cas de colonnes. Toutefois, la section rectangulaire a un moment d'inertie plus élevé et une rigidité flexionnelle plus efficace pour résister les charges appliquées et les déformations dans le cas des poutres. Par ailleurs, les travaux de construction et les exigences architecturales préfèrent la section rectangulaire des poutres, plutôt que les poutres circulaires, en raison de sa stabilité pendant l'installation et sa maniabilité lors de la connexion à d'autres membres structuraux comme les dalles et les colonnes. En outre, les poutres TPRFB qui sont complètement remplis de béton ne sont pas optimales pour les applications contrôlées par la flexion pure, puisque le béton fissuré en dessous de l'axe neutre ne contribue pas à la résistance et augmente le poids propre et les coûts de transport et d'installation. Cette thèse présente des études théoriques et expérimentales sur le comportement en flexion de poutres rectangulaires (TPRFB) en béton armé. Ces poutres rectangulaires tubulaires hybrides en PRF-béton-acier sont composées de tubes rectangulaires externes fabriquées par enroulement filamentaire. Ces tubes fournissent un renforcement de flexion et de cisaillement; et protègent le béton armé contre la corrosion. Les poutres peuvent être soient entièrement ou partiellement remplies de béton. Des tubes intérieurs ( de section circulaires ou carrés) en polymères renforcés de fibres de verre (PRFV) sont positionnés dans la zone tendue de la poutre afin de réduire le poids et d’éliminer le béton fissuré en traction. Pour augmenter l'action composite de la section hybride, les surfaces des tubes adjacents au béton ont été rendues rugueuses par enrobage de sable. Plusieurs variables ont été choisis pour étudier l'effet de l’épaisseur des tubes extérieurs et intérieurs, les laminés de fibres, et la forme sur le comportement en flexion de ces poutres hybrides (TPRFB). Pour atteindre les objectifs de l’étude, vingt-quatre échantillons de poutre pleine grandeur, ayant une longueur de 3200 mm et une section transversale de 305×406 mm2, ont été testés sous une flexion à quatre points. Ces échantillons comprennent huit poutres de TPRFB entièrement remplis avec une large gamme d'épaisseur du tube externe de 3.4 mm à 14.2 mm, quatorze poutres de TPRFB partiellement remplis avec différentes configurations de tubes extérieurs et intérieurs, et deux poutres en béton armé conventionnel, comme échantillons de référence. Les résultats indiquent une performance exceptionnelle des poutres rectangulaires de TPRFB entièrement et partiellement remplies en termes du rapport de la résistance sur la masse et de la ductilité par rapport aux poutres en béton armé conventionnel. Les poutres de TPRFB entièrement remplies avec un tube de petite épaisseur ont rompu de façon moins ductile en tension par rupture axiale des fibres. Les poutres de TPRFB entièrement remplies et ayant une grande épaisseur ont rompu de façon ductile en compression par flambage local vers l’extérieur des parois en compression du tube externe. Les résultats indiquent également que la résistance à la flexion des poutres de TPRFB entièrement remplies augmente d’une façon non linéaire avec l'augmentation de l'épaisseur des tubes jusqu'à une certaine limite optimale. Cette limite a été évaluée pour définir les sections TPRFB sous-armées et surarmées et, par conséquent, pour définir la rupture en tension et en compression des poutres de TPRFB entièrement remplies, respectivement. Les tubes creux intérieurs agissent positivement dans le renforcement des poutres de TPRFB partiellement remplies et en confinant le noyau de béton du côté en compression. En général, les poutres de TPRFB partiellement remplies ont rompu en compression par flambage local vers l'extérieur des parois en compression du tube externe. Les vides circulaires intérieurs ont montré une meilleure performance que les vides carrés intérieurs, bien qu’ils aient la même superficie de la section transversale et le même taux de PRF. Une analyse théorique basée sur la compatibilité des déformations d’une section en flexion a été développée pour prédire la réponse moment-courbure de la poutre TPRFB en tenant compte des pourcentages de confinement externe et interne. Les résultats analytiques et les résultats expérimentaux s’accordent en termes de moment, flèche, déformations, et positions de l'axe neutre. En outre, une étude analytique a été menée afin d'examiner la validité des codes de conception nord-américains pour prédire la réponse en flexion des poutres TPRFB. En se basant sur les résultats de ces études, de nouvelles équations ont été proposées pour mieux prédire le moment effectif d'inertie de la section et une nouvelle procédure de conception pour prédire les capacités ultimes. Ces équations considèrent l'effet de la résistance des tubes en PRFV externe et interne que le taux d’armature en acier. En outre, ils prédisent bien la flèche dans les phases avant et après la limite élastique des poutres rectangulaires hybrides à haute performance.
40

Développement d'un procédé d'enroulement filamentaire adapté aux matériaux composites sandwichs et caractérisation mécanique des matériaux / Development of a filament winding process adapted to sandwich composite materials and mechanical characterization of materials

Haddad, Mohamed 23 October 2017 (has links)
Les matériaux composites, et en particulier les sandwichs, sont très étudiés depuis des décennies. En effet, l'alliance entre légèreté et résistance de ces structures entraîne le développement de leur utilisation. Leur méthode de fabrication et éventuellement leur caractérisation restent des points essentiels dans la plupart des études. Ce travail s’inscrit dans le projet FUI SOLLICITERN qui vise à développer une citerne routière en matériau composite sandwich pour un véhicule d’hydrocurage. Comme première étape, et à partir du principe de l’enroulement filamentaire classique, l’objectif consiste à chercher des conceptions qui sont les mieux adaptées à l’enroulement d’un matériau sandwich sur un mandrin cylindrique, tout en respectant les paramètres de l’enroulement et leur influence sur la structure et les propriétés. La solution optimale étant validée, les matériaux constitutifs ont été étudié en mesurant de nombreuses propriétés mécaniques. L’objectif est de pouvoir aider le bureau d’étude à valider une solution de fabrication et de vérifier que les propriétés sont celles attendues. Pour ce faire, des caractérisations statique et dynamique ont menée sur des échantillons incurvés fabriqués par le procédé optimisé pour notre application. Cette partie comporte notamment différents essais expérimentaux dans le but de valider le comportement de la structure visée avec les dimensions et les combinaisons de matériaux les plus appropriées, en tenant compte du processus de fabrication. La meilleure configuration structurelle est retenue à la fin pour la fabrication de la citerne routière prototype. / Composite materials, and especially sandwich structures, have been studied for decades. Indeed, the association between lightness and resistance of these structures leads to the development of their use. Their manufacturing method and their characterization remain as essential points in most studies. This work is part of the FUI SOLLICITERN project, which aims to design a composite water treatment tank for vehicles intended for this purpose. As a first step, and based on the classical filament winding principal, we aim to search designs that are best adapted to the fabrication of a curved sandwich material on a cylindrical mandrel, while respecting the process parameters of and their influence on structural properties. Since an optimal solution was validated, the constituent materials were studied by measuring mechanical properties. The objective is to help our industrial partner to validate a manufacturing solution and verify that such properties are the expected ones. For that, several static and dynamic characterizations were carried out on curved samples manufactured by the optimized process designed for our application. This part includes various experimental tests in order to validate the structure behavior with the most appropriate dimensions and material combinations, taking into account the manufacturing process. At the end, the best structural configuration is retained for the first tank prototype fabrication.

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