Ce travail de thèse porte sur la réalisation de MEMS organiques dans un dispositif original, le microévaporateur, couplant la technique MIMIC (Micromolding in Capillaries) à la pervaporation microfluidique. Il est expliqué comment le phénomène de pervaporation peut être utilisé pour concentrer des solutions polymériques diluées jusqu'à l'obtention de matériaux composites dans des géométries de dimensions typiques 25 μm x 100 μm x 10 mm. Il a été montré qu'il est possible d'établir des modèles décrivant cette croissance en excellent accord avec l'expérience et l'étude de l'influence de différents paramètres (concentration, géométrie...) sur la croissance a alors permis de prédire les vitesses de croissance des matériaux composites. Deux systèmes ont été réalisés à partir de ces derniers, associés à deux effets : l'effet bilame thermique et l'effet piezorésistif mettant en avant une preuve de concept d'une nouvelle voie de fabrication des MEMS organiques : la voie microfluidique. Un dispositif plus complexe comprenant également des vannes microfluidiques a permis de programmer des matériaux à gradients de composition dans la longueur de divers matériaux allant des cristaux colloïdaux aux matériaux polymères. / This work deals with the making of organic MEMS within an original device, the microevaporator, coupling the MIMIC technique (Micromolding in Capillaries) and microfluidic pervaporation. It is shown how the pervaporation phenomenon can be used to concentrate polymeric diluted solutions until we obtain composite materials into geometries with typical dimensions about 25 μm x 100 μm x 10 mm. We showed that it is possible to establish models which describe this growth in excellent agreement with experiments and the study of the influence of different parameters (concentration, geometry...) upon the growth thus allowed us to predict the growth velocities of those composite materials. Two systems have been made associated to two effects : bimetallic strip effect and piezoresistive effect in order to demonstrate a new proof of concept of a new way to make organic MEMS using microfluidics. A more complex device including microfluidic valves allowed us to encode materials with a gradient of composition within their largest dimension from colloidal cristals to polymeric materials.

Quando o concreto é submetido a ações especiais, como cargas cíclicas ou ação de cargas de impacto, modificações em sua composição são necessárias, já que o concreto não apresenta desempenho satisfatório à tração, o que compromete o seu comportamento frente à ação de cargas dinâmicas. Uma alternativa para amenizar esta deficiência consiste em adicionar fibras ao concreto. Estas atuam como reforços à tração, transformando a matriz cimentícia, tipicamente frágil, em um material que apresenta boa resistência residual após a fissuração. Buscando colaborar na avaliação da eficiência de diferentes tipos de fibras, o presente trabalho analisa o comportamento de concretos com fibras de aço, submetidos ao impacto, avaliando a influência do fator de forma, do comprimento e do teor de fibras, assim como do tamanho do agregado. São ainda analisados os efeitos da incorporação de fibras na resistência à compressão, na resistência à tração por compressão diametral, no módulo de elasticidade e na tenacidade dos compósitos. Adicionalmente, é executada uma comparação entre os resultados experimentais e os derivados de um esquema de modelagem da situação de impacto através do uso do método de elementos discretos. Buscou-se, através da modelagem teórica, executar um mapeamento dos danos, provocados por cargas de impacto incrementais, ao longo do tempo, bem como determinar as energias necessárias para levar as placas até a ruptura. Os resultados indicam que a incorporação de fibras de aço não consegue retardar o aparecimento da primeira fissura, mas aumenta significativamente a tenacidade dos compósitos. Fibras mais longas e com maior fator de forma tendem a ser mais eficientes, desde que se supere um teor de fibras mínimo, que neste trabalho ficou em torno de 100.000 fibras/m3, para fibras longas (50-60 mm) e de 400.000 fibras/m3, para fibras curtas, cuja ancoragem é menos eficiente. O método de teste de impacto por queda de esfera se mostrou adequado e sensível, porém o esquema de modelagem numérica testado necessita ser refinado para permitir uma adequada simulação do comportamento de concretos com fibras. / When submitted to special loading patterns, derived from dynamical actions such as cyclic or impact loads, concrete elements need to be reinforced, in order to resist the tensile stresses. A feasible alternative, in such cases, is to incorporate fibers in the concrete matrix. The fibers act as a tensile reinforcement, transforming the fragile cement matrix into a composite with significant post-cracking residual strength. In order to contribute with the data collection about the efficiency of different fiber types, the present research work presents an analysis of the behavior of steel fiber reinforced concretes subjected to impact loads. The work investigates the influences of changes in the shape factor, length and amount of fibers. The effects of these combinations on other basic properties of the composites, such as compression strength, split cylinder tensile strength, Young’s modulus and tenacity is also measured. Additionally, a comparison is made between the experimental results from the impact tests and the estimates obtained from a theoretical model that uses the discrete element method (DEM). This theoretical approach aimed to determine if the model was able to simulate the damage evolution over time generated by the increasing impacts loads, as well as to determine the total energy necessary to crack and break the specimens. The results obtained pointed out that the introduction of steel fibers does not affect the energy for the first crack but increases significantly the tenacity of the composite. Longer fibers, with greater shape factors, tend to be more efficient, provided that the fiber content is sufficiently high. The minimum recommended fiber content, according to the data from this research, may be around 100.000 fibers/m3, for longer fibers (50-60 mm). Or around 400.000 fibers/m3, for shorter fibers, which are not so efficient in terms of anchorage. The impact test method developed was considered adequate, being sensitive to the phenomenon and providing reliable data. The DEM model, however, needs to be refined to be able to deal with fiber concrete composites.

Représentations séparées pour la simulation multi-échelle du comportementmécanique et de l’endommagement des matériaux composites.Résumé: Le développement de méthodes numériques performantes pour simuler les structurescomposites est un défi en raison de la nature multi-échelle et de la complexité des mécanismed’endommagement de ce type de matériaux. Les techniques classiques de discrétisationvolumique conduisent à des coûts de calcul importants et sont restreintes en pratique à despetites structures.Dans cette thèse, un nouvelle stratégie basée sur une représentation séparée de la solution estexplorée. L’objectif est de proposer un cadre numérique efficace et fiable pour analyser les endommagementsdans les composites stratifiés sous chargements statiques et dynamiques. Ladécomposition propre généralisée (PGD) est utilisée pour construire la solution.Pour traiter l’endommagement, et plus particulière le délaminage, un modèle de zone cohésivea été implémenté dans la PGD. Une approches multi-échelle innovante est également proposéepour simuler le comportement mécanique des composites à microstructure périodique. L’idéeprincipale est de séparer deux échelles : l’échelle du motif périodique (microstructure) et l’échellemacroscopique. Les résultats de la PGD sont très proches des résultats obtenus par la méthodeéléments fini classique. Finalement, la PGD permet de réduire significativement la complexitédes modèles tout en gardant une précision satisfaisante. / Separated representations for the multiscale simulation of the mechanicalbehavior and damages of composite materials.Abstract: The development of efficient simulations for composite structures is very challengingdue to the multiscale nature and the complex damage process of this materials. When usingstandard 3D discretization techniques with advanced models for large structures, the computationalcosts are generally prohibitive.In this thesis, a new strategy based on a separated represenation of the solution is explored todevelop a computationally efficient and reliable numerical framework for the analysis of damagesin laminated composites subjected to quasi-static and dynamic loading. The PGD (Proper GeneralizedDecomposition) is used to build the solution.To treat damage, and especially delamination, a cohesive zone model has been implemented inthe PGD solver. A novel multiscale approach is also proposed to compute the mechanical behaviorof composites with periodic microstructure. The idea is to separate two scales: the scaleof periodic pattern and the macroscopic scale. The PGD results have been compared with theresults obtained with the classcial finite element method. A close agreement is found between thetwo approach and the PGD has significantly reduced the model complexity.

A otimização estrutural, utilizando ferramentas computacionais é um grande campo de pesquisa na atualidade. Os métodos utilizados, dependendo da complexidade do problema, demandam um grande custo computacional, e por isso vem sendo avaliandas várias técnicas para diminuí-lo. Uma delas é o emprego de técnicas de aproximação de análises, dentre as quais destacam-se as redes neurais, que combinadas aos métodos de otimização e de análises clássicos conseguem bons resultados e reduzem significativamente o tempo de processamento. O emprego dos compósitos laminados como material estrutural vem crescendo nos últimos tempos, incentivado pela suas excelentes propriedades mecânicas e baixo peso. Em consenso com todo o esforço científico dedicado a essa área, o presente trabalho visa a implementação de uma ferramenta computacional capaz de otimizar estruturas complexas fabricadas com tais materiais, a um baixo custo computacional. Com isto em mente, é desenvolvido um sistema de otimização, aproveitando módulos implementados previamente para a análise estática linear e não linear através do método dos elementos finitos (MEF), e o módulo de otimização por algoritmos genéticos. Serão desenvolvidos os módulos de análise modal, para otimizar também estruturas com critérios baseados em freqüências e modos, e o modulo de redes neurais de tipo perceptron para aproximações das análises feitas através do MEF. Alguns exemplos são apresentados para demonstrar que bons resultados são obtidos com a utilização de redes neurais artificiais, cujo treinamento permite poupar tempo computacional proveniente do grande número de análises usualmente necessárias no processo de otimização. / Structural optimization using computational tools has become a major research field in recent years. Methods commonly used in structural analysis and optimization may demand considerable computational cost, depending on the problem complexity. Therefore, many techniques have been evaluated in order to diminish such impact. Among these various techniques, artificial neural networks may be considered as one of the main alternatives, when combined with classic analysis and optimization methods, to reduce the computational effort without affecting the final solution quality. Use of laminated composite structures has been continuously growing in the last decades due to the excellent mechanical properties and low weight characterizing these materials. Taken into account the increasing scientific effort in the different topics of this area, the aim of the present work is the formulation and implementation of a computational code to optimize manufactured complex laminated structures with a relatively low computational cost by combining the Finite Element Method (FEM) for structural analysis, Genetic Algorithms (GA) for structural optimization and Artificial Neural Networks (ANN) to approximate the finite element solutions. The modules for linear and geometrically non-linear static finite element analysis and for optimize laminated composite plates and shells, using GA, were previously implemented. Here, the finite element module is extended to analyze dynamic responses to optimize problems based in frequencies and modal criteria, and a module with perceptron ANN is added to approximate finite element analyses. Several examples are presented to show the effectiveness of ANN to approximate solutions obtained using the FEM and to reduce significatively the computational cost.

In last decades, there has been a relevant growth in the application of composite materials reinforced by fibers in the several industries, especially the aeronautical, automotive, construction and offshore structures segments. How the composites exhibit relationships stiffness/weight and resistance/high weight, and other interesting features compared with other materials, they have been increasingly used to replace conventional materials. The present work has as objective to develop a study about laminated polymeric composite tubes subjected to thermomechanical loads. The laminae are composed of polymeric matrix involving unidirectional long fiber reinforcement. The walls of the studied tubes present various lamination schemes and different constituent materials. The analyses are set by analytical formulations that permits obtaining the displacements, stresses and strains, as well as verification failures in the laminae. Different empirical and semi-empirical analytical models are used for failure analyses. Effects of thermomechanical loads, such as internal pressure, bending, and temperature changes are considered. The analyzed cases consist of tubes with walls comprised of several layers with different directions of fibers, some including laminae sand impregnated with resin. The results are also compared with other available in the literature. It is verified that the Tsai-Wu criterion provides superior results to the other two failure models used in the work, especially for angles greater than 50°. Moreover, this criterion obtained an inconsistent result in the analysis of the temperature effects for the laminae [+55°/−55°]2. / Fundação de Amparo a Pesquisa do Estado de Alagoas / Nas últimas décadas, houve um grande crescimento na aplicação de materiais compósitos reforçados por fibras em diversos setores, com destaque para os segmentos aeronáutico, automotivo, construção civil e de estruturas offshore. Como os referidos compósitos apresentam relações rigidez/peso e resistência/peso elevadas, além de outras características interessantes, em comparação com outros materiais, eles têm sido cada vez mais utilizados em substituição aos materiais convencionais. O presente trabalho tem como objetivo o desenvolvimento de um estudo sobre tubos de materiais compósitos poliméricos laminados submetidos a cargas termomecânicas. As lâminas são constituídas por uma matriz polimérica envolvendo fibras unidirecionais longas de reforço. As paredes dos tubos estudadas apresentam diferentes esquemas de laminação, podendo ser constituídas por diferentes materiais. As análises são feitas através de formulações analíticas que permitem a obtenção dos deslocamentos, tensões e deformações, assim como a verificação de falhas nas lâminas. Para a análise de falhas são empregados diferentes modelos analíticos empíricos e semiempíricos. Efeitos de cargas termomecânicas, tais como pressão interna, flexão e de variação de temperatura são considerados. Os casos analisados consistem de tubos com paredes constituídas por várias camadas com diferentes direções de fibras, alguns incluindo lâminas de areia impregnada com resina. Os resultados encontrados também são comparados com outros disponíveis na literatura. Verifica-se que o critério de Tsai-Wu fornece resultados superiores aos dos outros dois modelos de falha utilizados no trabalho, principalmente para ângulos superiores a 50°. Além disso, esse critério obteve resultado inconsistente na análise dos efeitos de temperatura para o laminado [+55°/−55°]2.

L'efficacité de la technique NSM dans la réparation et renforcement des structures est fortement dépendante de la performance d’adhérence entre les joncs de carbone et le béton. De nombreuses études récentes ont été réalisées pour quantifier d’adhérence sur des éprouvettes saines en raison de la complexité de ce problème. Par contre, le comportement des éléments réparés peut être affecté, d’une part, selon les conditions de pré-chargement, et d’autre part, selon l’endommagement spécifique, qui pourraient être rencontrés dans les structures existantes. En effet, un endommagement dans le béton ou dans les armatures peut modifier le comportement global des éléments réparés en réduisant la capacité portante.Tout d’abord, des essais à grande échelle en flexion ont été réalisés pour étudier le comportement des poutres en béton armé. D’une part, différents types d’endommagements ont été considérés tels que la corrosion des aciers et les charges excessives. D’autre part, différentes conditions de pré-chargement incluant les maintiens du chargement à l’heure de la mise en oeuvre de la réparation ont été étudiées. Le comportement de la poutre témoin renforcée se distingue par son côté fragile qui s’accompagne d’une ruine soudaine par pull-out du jonc de carbone de la résine suivie d’éclatement de morceaux de béton dans la zone de béton d’enrobage et d’un écrasement du béton comprimé. Par contre, la ruine de la poutre corrodée et réparée intervient par séparation (délamination) du béton d’enrobage dans la zone tendue au niveau à l’insertion du jonc de carbone, qui a commencé entre deux fissures de flexion dans la zone centrale et s’est propagé vers l’appui. Ensuite, afin de comprendre l’origine du mode de ruine de la poutre corrodée et réparée, et d'étudier le comportement global, la rigidité, la ductilité, le mode de ruine, et la capacité portante, des essais expérimentaux ont été réalisés en faisant varier les paramètres relatifs aux conséquences de la corrosion (perte généralisée de la section d’acier tendu, éclatement du béton d’enrobage, détérioration de l’adhérence acier-béton). Cependant, la ruine par la séparation du béton d’enrobage entre deux fissures adjacentes observé sur la poutre corrodée et réparée n’a jamais été obtenue. Pour nos simulations : La ruine a eu lieu par Pull-out du jonc de carbone. Dans tous les cas, la capacité portante mesurée des poutres endommagées puis réparées était supérieure à celle de la poutre témoin (non-renforcée)Finalement, puisque les structures nécessitant de la réparation par application de matériaux composites ne sont pas de récentes, et par conséquent, qui ont déjà subi un certain nombre d’endommagements dus aux contraintes mécaniques (surcharge maintenue à long-terme, charge accidentelle à court-terme), une partie expérimentale s’est intéressée à l'utilisation des joncs de carbone pour la réparation des éléments endommagés par une charge excessive, puis réparés sous ou sans charge maintenue. Un endommagement est capable de réduire légèrement la capacité portante des poutres réparées (moins de 8% par rapport à la poutre témoin renforcée). La réparation des poutres sous charge maintenue a une influence non-significative en diminuant la capacité portante entre 5% et 6% par rapport aux poutres endommagées réparées sans charge maintenue. La ruine des poutres pré-chargées puis réparées a été par l’arrachement du jonc de carbone de la résine « Pull-out » à cause des fissures longitudinales développées dans la résine qui conduit à la perte d'adhérence entre le jonc de carbone et le matériau de scellement en réduisant légèrement leur capacité portante. Par contre, les poutres endommagées par chargement excessif puis réparées ont montré un mode de ruine différent (par écrasement du béton comprimé) mais avec une réduction significative leur capacité portante / The effectiveness of the NSM technique for repairing or strengthening the RC structures is highly dependent on the bond strength behavior between CFRP rods and concrete. Many recent studies have been conducted to evaluate bond strength on undamaged concrete specimens because of the complexity of this problem. On the contrary, the behavior of repaired specimens may be affected, first, by pre-loading conditions, and the other, depending on specific damage that could be encountered in the existing structures. Indeed, damage in concrete or in reinforcement can change the global behavior of repaired elements by reducing the bearing capacity.First, large-scale bending tests were carried out to study the behavior of reinforced concrete beams. On the one hand, various types of damage were considered such as the steel corrosion and excessive loads. On the one hand, different pre-loading conditions including sustaining loads at the time of implementation repair were studied. The behavior of the beam strengthened control is distinguished by its fragile side which is accompanied by sudden failure due to pull-out of the CFRP NSM rod, followed by splitting of concrete pieces in the concrete cover and a crushing of concrete in compressive zone. On the other hand, the failure mode of corroded repaired beam occurred by concrete cover delamination in the tension zone at the level of insertion of CFRP NSM rod that started between two bending cracks in the central area and has spread to the support. Then, in order to understand the origin of the failure mode, global behavior, stiffness, ductility, and bearing capacity of repaired corroded beam, an experimental tests were performed by varying the parameters relating to the consequences of corrosion (such as generalized loss of bottom steel section, concrete cover delamination failure and bond strength failure between concrete and reinforcing steel). However, the failure occurred by the concrete cover delamination between two adjacent bending cracks was never obtained on the repaired corroded beam. For our simulations: The failure was due to pull-out of CFRP rod. In all cases, the bearing capacity measured for repaired damaged beams was greater than that of control beam (non-repaired).Finally, since the structures requiring repair by applying composite materials are not recent, and consequently, number of damages occurred due to mechanical stress (long-term sustained overloading, short term accidental load), an experimental part was interested in the use of CFRP NSM rods to repair of beams damaged by excessive load, and then repaired under or without sustained load. A damage can slightly reduce the bearing capacity of the repaired beams (less than 8% compared to the strengthened control beam). The repair of beams under sustained load has a non-significant effect by reducing the bearing capacity between 5% and 6% compared to the damaged beams repaired without sustained load. The damages of the pre-loaded RC beams repaired with NSM failed by the tearing of the carbon rod "pull-out" due to the longitudinal cracks developed in the epoxy resin volume, which leads to loss of adhesion between the CFRP rod and the sealing material by slightly reducing their bearing capacity. While, the RC beams damaged by overloading which were repaired showed a different mode of failure (crushing of concrete in compression) with also a significant reduction in their ultimate bearing capacity values

De nombreuses études ont été menées sur les matériaux composites, concernant le comportement mécanique à l’échelle macroscopique. D’autre part, le développement continu des techniques de détection et de mesures de champs permet d’aller plus loin dans l’analyse des structures complexes, dont les matériaux composites. Ainsi, la corrélation volumique (DVC) basée sur des acquisitions de la structure interne à différents états de déformation, permet la mesure du champ des déplacements dans le volume des échantillons. Le gauchissement des sections dû aux contraintes de cisaillement transverse est un phénomène propre aux structures anisotropes comme les structures composites. De nombreuses études traitent du développement des modèles analytiques pour la modélisation numérique et la détermination des déplacements avec le plus de précision possible. Ainsi, de nombreux modèles existent, certains très complexes, pour la prise en compte de ce phénomène dans l’étude des structures multicouches. L'objectifs de ce travail doctoral est d’utiliser les mesures de champs issues de la corrélation volumique couplée à la tomographie rayons X, pour visualiser le gauchissement des sections pour un cas de sollicitation de flexion trois points. Une méthode de mesure ainsi qu’un système de chargement in-situ spécifique sont développés dans ce travail de recherche. Les modèles analytiques existants sont évalués et comparés à partir de mesures expérimentales. Aussi, un nouveau modèle est également proposé à partir d'une identification numérique, basée sur les mesures de champs volumiques réalisées. Les résultats de ce travail de thèse permettront une meilleure compréhension du phénomène physique rencontrés lors de l’utilisation des matériaux composites et pourront envisager des pistes d’optimisation de leur conception et de leur mise en œuvre. / The complex mechanical behaviour of composite materials, due to internal heterogeneity and multi-layered composition impose deeper analysis. Several studies have already been conducted on the composite structures mechanical behavior at the macro level. On the other hand, the continuous development of detection techniques and field measurements can now go further in the analysis of complex structures, including composites. Thus, the digital volume correlation (DVC) based on the acquisition of the internal structure at different deformation states, allows the measurement of displacement fields through the thickness of the specimen. Warping sections due to transverse shear is a phenomenon linked to anisotropic structures, such as composite structures, which has been the subject of many studies to develop analytical models for the numerical modeling and the determination of displacements with the greatest possible precision. Many theories and models exist, some very complex, for the consideration of this phenomenon .. One goal of this doctoral work is to use measurements from the density correlation to determine whether these models the effects of transverse shear are physically consistent, and if their validity is good in the case of a kinematic measurement volume. A second objective of this thesis is to acquire know-how in the processing of information resulting from acquisitions by X-ray tomography In this sense, several studies are planned for the treatment and use of this information in an industrial context. The results of this work will provide a better understanding of physical phenomena encountered in the use of composite materials to generate optimization of their design and implementation paths.

L'objectif du projet COMPTINN (COMPosites Tièdes INNovants) est d'obtenir des matériaux composites pouvant être utilisés sur de longues durées, à des températures comprises entre 150°C et 400°C, pour des applications structurales de l'aéronautique civile. Les travaux de thèse s'inscrivent dans un objectif de développement de matériaux thermostructuraux mis au point par un procédé industrialisable pour la production de pièces en série, respectueux de l'environnement et économiquement viable. Les procédés d'élaboration choisis sont ceux utilisés pour la mise en œuvre des CMO (Composites à Matrice Organique) thermodurcissables en moule fermé et par voie liquide. Les procédés les plus conventionnels ont été sélectionnés : l'injection par transfert de résine (RTM : Resin Transfer Molding) et l'infusion de résine sous vide (LRI : Liquid Resin Infusion). Les constituants des composites sont d'une part une matrice vitrocéramique, issue d'une résine dérivée d'un système géopolymérique, et d'autre part des renforts 2D et 3D en fibres de carbone. La viscosité d'une résine est la propriété principale qui conditionne sa mise en œuvre par les procédés d'élaboration par la voie liquide. La résine utilisée étant une suspension dont la viscosité est relativement élevée, la faisabilité de l'élaboration de composites par RTM ou LRI est a priori délicate. Une attention particulière a donc été portée à la rhéologie de la résine. Les résultats de cette étude ont permis d'optimiser d'importants paramètres procédés. L'étude s'est ensuite dirigée vers l'élaboration et la caractérisation des composites. L'impact du procédé de mise en œuvre sur la microstructure et sur les propriétés thermomécaniques des composites a été évalué. L'influence d'autres paramètres procédés, tels que le taux de dilution de la résine, la direction d'imprégnation du renfort et le différentiel de pression, a été étudiée. / This research work is part of the collaborative project COMPTINN (Innovative composite materials for intermediate temperature applications). This project aims at enabling the manufacturing of competitive structural composites able to bear up continuous thermal exposure, such as in aircraft parts located close to engines. A new class of glass-ceramic matrices for structural composites was developed to reach this goal. These new matrices come from an inorganic thermosetting polymer derived from a geopolymeric system. Prepreg process is currently used to manufacture composites but these composites would be more competitive if they are produced by an easy and cost effective process technology. Liquid molding (LRI or RTM) seems to be a convenient solution. Two kinds of reinforcements were considered: a layup of several two-dimensional woven fabric plies and a three-dimensional preform.The rheological behaviour of the considered inorganic polymer was firstly investigated. The best conditions were identified to obtain the lowest viscosity of the resin in order to help the production of structural composite parts by liquid molding.Then, the research work investigates how changes in the manufacturing process impact the mechanical properties of the composites. A microstructural characterization helps to link the mechanical behavior to the processing route. The effects of varying several processing parameters have been studied such as the dilution rate of the resin, the impregnation direction or the pressure differential.

Les Lasers à Cascade Quantique (QCL) sont de "nouvelles" sources THz dont les progrès en termes de puissance, température de fonctionnement et qualité de faisceau sont remarquables. Les QCL sont utilisés dans des dispositifs d'imagerie THz continue pour le Contrôle Non Destructif de matériaux. Une première application de CND sur des matériaux composites permet de mettre en évidence de manière qualitative les défauts d'imprégnation des fibres par la résine ou les dommages causés par un impact. Des images à 3,8 THz, en transmission et ré flexion, ont pu être comparées avec une technique de CND par ultrasons. Une seconde application quantitative porte sur la concentration d'eau dans deux matériaux polymères à tendance hydrophobe : le polystyrène et le polypropylène. L'établissement d'une relation entre la transmittance de l'échantillon et sa prise de masse d'eau permet d'établir une cartographie quantifiée de la concentration d'eau. Ces cartographies sont nécessaires à la connaissance du processus de diffusion de l'eau dans les matériaux polymères. / Quantum Cascade Lasers (QCL) are "new" THz sources that have enjoyed remarkable progress in terms of power, operating temperature and beam quality. QCLs are used in continuous wave THz imaging setups applied to Non Destructive Testing of materials. A first qualitative application of NDT allows us to highlight defects in the fibers impregnation by resin or damages caused by an impact on composite materials. Transmission and reflection images at 3.8 THz are compared with a NDT ultrasonic technique. A second quantitative application relates to the water concentration in two hydrophobic polymeric materials: polystyrene and polypropylene. Establishing a relationship between the transmittance of the sample and mass water content enables us to draw up a quantified mapping of the latter. These maps are necessary for the understanding of the water diffusion process in polymeric materials.

A integridade de dutos ganha importância à medida em que o desenvolvimento da indústria expande a malha para transportar líquidos e gases num contexto de aumento das exigências ambientais. Um importante aliado para manutenção da integridade de dutos são reparos de materiais compósitos. Estes materiais apresentam baixa densidade, capacidade de direcionar resistência de acordo com as direções das solicitações, execução de reparo a frio sem necessidade de interromper produção ou grande maquinário. Este trabalho tem como objetivo desenvolver e implementar um algoritmo de elementos finitos que permita avaliar os esforços e a resistência das paredes de um tubos fabricados ou reparados com laminados de material compósito carregados com pressão interna. Entre as vantagens de desenvolver um programa tem-se: agilidade de avaliação, menor custo com licença, menores exigências computacionais, possibilidade de desenvolver o programa e o melhor entendimento da modelagem dos fenômenos. Utiliza-se como entrada do programa o diâmetro do duto, pressão interna e parâmetros do laminado. A modelagem em elementos finitos é realizada a partir da teoria clássica de laminados. Aplicando o carregamento resultante da pressão interna, determina-se os deslocamentos e são calculadas as tensões e aplicado o critério de falha de Tsai-Hill em cada camada. Estudos experimentais e numéricos encontrados na literatura foram simulados com o programa gerado e os resultados para propriedades do laminado, tensões nos dutos e pressão de ruptura apresentam concordância com os resultados da literatura.O programa ainda tem sua estrutura modificada para encontrar a pressão de falha a partir dos dados do laminado. O programa implementado permite uma avaliação rápida de resistência do reparo e possibilita avaliar rapidamente a resposta a mudanças nos parâmetros de projeto do laminado. / Nowadays the integrity of pipelines gets even more important as a result of the industry growth and strong enviromental requirements. An important ally in the maintenance of the integrity is the repair with composite materials. These materials have low specific gravity, repair can be done at low temperatures and they can orientate the main resistence according to the load. The goal of this work is to develop and inplement an algorithm that allows the assessment of loads and strength in the pipes loaded with internal pressure manufactured or repaired with composite laminates using the finite element method. Among the advantages of the own software development there are agility for the assessment , lower cost with software licence, lower computational demands, possibility of developing the software and a better understanding of the modeling of the fenomena. The inputs of the software are the diameter of the pipe, internal pressure and parameters of the composite laminate. The finite element analysis is constructed according to the classical laminate theory. After the loads resulting of the internal pressure are applied, the displacements are calculated and then the stresses and Tsai-Hill failure criteria are determined for each layer. Experimental and numerical studies were simulated with the developed software and the results for the laminae properties, pipe stress and the failure pressure are in agreement with the results found in the review. The software is modified in order to end the failure pressure to show the versatility of the algorithm. We conclude that the algorithm allows a fast assessment of the strenght of pipeline repair and the changes in the answer of the pipe when the repair parameters are changed.