This thesis describes the development of a general Fortran 90 framework for the solution of composite laminate design problems using a genetic algorithm (GA). The initial Fortran 90 module and package of operators result in a standard genetic algorithm (sGA). The sGA is extended to operate on a parallel processor, and a migration algorithm is introduced. These extensions result in the distributed genetic algorithm with migration (dGA). The performance of the dGA in terms of cost and reliability is studied and compared to an sGA baseline, using two types of composite laminate design problems. The nondeterminism of GAs and the migration and dynamic load balancing algorithm used in this work result in a changed (diminished) workload, so conventional measures of parallelizability are not meaningful. Thus, a set of experiments is devised to characterize the run time performance of the dGA. The migration algorithm is found to diminish the normalized cost and improve the reliability of a GA optimization run. An effective linear speedup for constant work is achieved, and the dynamic load balancing algorithm with distributed control and token ring termination detection yield improved run time performance. / Master of Science

Recent developments in the area of microfabrication technologies, has enabled the fabrication of many radio frequency/microwave components with better performance and lower cost than possible with semiconductor based fabrication technology. Many of these microfabricated RF components such as switches and phase shifters, popularly known as RF MEMS, are aimed at reducing the insertion loss and improving other performance parameters such as linearity. For these devices size miniaturization is not necessarily important, as in practical subsystems, these components are integrated with RF front-ends on a laminate. This thesis deals with concepts of a low cost passive phase shifter fabricated in-situ on a microwave laminate. The operation of this Mesoscale Electrostatically actuated Phase shifter on microwave Laminate (MEPL) is similar to that of a micromachined distributed MEMS transmission line (DMTL) phase shifter. In spite of advantages of low losses, wide bandwidth, low DC power consumption and high linearity over semiconductor/MMIC technology, microfabricated phase shifters are often not used in field because of issues related to fabrication reliability, packaging and integration. On the other hand, the proposed MEPL will have all the advantages of conventional MEMS phase shifters with additional benefit of lower cost. Furthermore, these are integrable to form a monolithic phased array. A MEPL phase shifter of 50-bridges periodically distributed on the co-planar waveguide (CPW) transmission line is demonstrated in this thesis. MEMS air bridges are electrostatically actuated to vary the capacitance of the transmission line, which changes the phase velocity of the propagation RF signal, consequently phase at the output port. The realized MEPL is characterized for electromagnetic as well as electromechanical performance. The electromechanical characterization of this device is performed using a Laser Doppler Vibrometer (LDV). The measured data showed good agreement with the analytical data.. Major application of a phase shifter is in a phased array antenna system. MEPL is particularly suited for a monolithic phase array antenna. The proposed monolithic phased array antenna system fabrication approach utilizes extremely simple and economical modern printed circuit board technology to pattern the conventional microwave laminate and copper foil. A complete monolithic phased array antenna system is fabricated on a microwave laminate using an embedded phase shifter operating with electrostatic principles. Other components such as DC block and bias tee are integrated into the CPW-microstrip transitions to optimize the space and performance. Integrated phased array antenna is fabricated and tested to demonstrate the beam steering capability. Measured S11 is better than -15dB at the operating frequency of 9.8GHz. The beam steering capability is shown as proof of concept by showing the beam scan angle of 10deg with bias voltage of 125V. The mesoscale phase shifter demonstrated in this thesis has several advantages compared to micromachined phase shifters. The proposed fabrication approach does not use metal deposition/patterning process, which removes the need of high cost clean room and sophisticated films deposition equipments. Secondly, as there are no thin films used, stiction is not expected on phase shifters fabricated with this approach. Since this approach uses thicker metal films, the power handling capability is expected to be significantly higher than micromachined phase shifters. Since conventional phased array antenna system components are fabricated on a microwave laminate, micro machined phase shifters realized on semiconductor substrates are required to be packaged separately before integrating with such phased array circuits. Packaging of the micro-machined RF-MEMS/MEMS devices is still a major issue and contributes to a substantial part of the total cost. Unlike micromachined phase shifters which are required to be packaged and then embedded in phased array applications, device presented in this thesis is packaged in-situ. Compared to similar monolithic phased array antenna reported on silicon substrate which are limited by wafer size, these arrays can be easily extended for larger arrays on microwave laminate as these are available in large size. To summarize, the proposed fabrication approach for phase shifters overcomes many limitations of micromachined components for microwave applications while retaining most of their advantages compared to other existing approaches based on ferrites or semiconductor technologies.

A model is proposed to predict the heat spreading behaviour experienced by laminate materials when heated over only a part of the domain, which is broken up into two regions, known as the heated and fin regions. The 2D, steady-state, two-region fin model is unique in its treatment of multilayer conduction heat transfer, giving the exact solution in the heat-spreading layer only, in both Cartesian and cylindrical coordinates. The experimentally and numerically validated two region fin model can help designers to assess improved heat transfer rates for laminate pouches for use to encapsulate supercooled salt hydrate phase change materials for long-term heat storage. Waste aseptic cartons (e.g. Tetra Brik) are a potentially useful resource for making laminate heat storage pouches since value-added end-uses are largely absent in Canada and in many other countries. The model is also useful for assessing improved temperature uniformity in heat spreading devices with applied heat fluxes.

[pt] As lâminas de bambu foram criadas para padronização da matéria prima de modo a aumentar sua resistência, controlar sua forma e desenvolver elementos estruturais sustentáveis e inovadores. O bambu é um material gradualmente funcional (FGM) devido a sua progressiva distribuição de fibras por toda a espessura de sua parede. Esta pesquisa apresenta os resultados de uma série de investigaçóes experimentais em que o colmo de bambu (Dendrocalamus giganteus) foi dividido em 6 segmentos de análise. Três divisões ao longo do seu comprimento, em sua porção baixa, média e alta, e, em seguida, duas divisões de sua espessura, interior e exterior. Na primeira série, os espécimes de cada segmento foram testados separadamente para estabelecer o seu módulo de elasticidade à tração Et. Seis tipos de vigas de bambu uniaxial-laminados, de 2,5 cm de largura, altura 5 centímetros e 50 cm de comprimento, foram montadas com camadas de cada segmento específico do colmo do bambu, utilizando resina adesiva de mamona. Quatro ensaios de flexão pontual foram realizados em amostras de viga para estabelecer o módulo de elasticidade em flexão, Eb. Os valores experimentais de ambos os grupos de amostra foram comparados com os valores teóricos, aplicando a teoria da mecânica dos sólidos. Os resultados forneceram informações para melhorar o arranjo dos segmentos das vigas de lâminas de bambu sujeitas a cargas de flexão. Baseado nos resultados, também é possível introduzir valores equivalentes para análises das propriedades mecânicas das vigas usando a teoria da mecânica de sólidos. / [en] Laminated bamboo was created to standardize the raw material in order to increase its strength, control its shape and develop sustainable and innovative structural elements. Bamboo is a Functionally Graded Material (FGM) due to the progressive distribution of the fibers across its wall thickness. This research presents the results of an experimental investigation series in which bamboo culm, of Dendrocalamus giganteus, was divided into 6 segments of analysis. Three divisions along its length, bottom, middle and top, and then two divisions across its wall thickness, inner and outer. In the first series, the specimens of each segment were tested separately to establish their tensile modulus of elasticity Et. Six types of bamboo uniaxial-laminated beam specimens of 2.5 cm width, 5cm height and 50 cm length were assembled with layers from each particular segment of bamboo culm, using resin of mamona adhesive. Four point bending tests were conducted on beam specimens to establish the bending modulus of elasticity Eb. Experimental values of both specimen groups were compared to those of theoretical values, applying solid mechanics theory. The results provide information to improve the segment arrangement of bamboo-laminated beams upon subjection to bending loads. Based on the results, it is also possible to introduce equivalent values for the analysis of the mechanical properties of the beams, using solid mechanics theory.

L’objet de cette thèse est de proposer et d’identifier un modèle de comportement mécanique en fatigue écrit à l’échelle du pli ou de la couche composite élémentaire. Le modèle doit permettre de prédire l’évolution des dégradations mais également la résistance résiduelle. Les matériaux concernés par cette étude sont des composites renforcés par des tissus de fibres de verre bi ou tri axiaux. Ce travail exclue les zones de liaisons ou de reprise de pli où des contraintes hors plan engendrent des couplages forts entre endommagement intra et inter laminaires. Les principaux objectifs de la thèse sont de : - Identifier sur le matériau de l’étude les mécanismes d’endommagement et leur couplage en quasi-statique et en fatigue - Caractériser et modéliser la perte de rigidité engendrée par les mécanismes d’endommagement - Caractériser et modéliser les cinétiques d’endommagement en fatigue - Caractériser et modéliser les pertes de résistance engendrées par les mécanismes d’endommagement - Implémenter et tester le modèle proposé (ou celui retenu de la littérature et qui sera modifié si besoin) dans un code de calcul EF / The purpose of this thesis is to propose and identify a model of mechanical fatigue behavior written for the lamina level. The model would be able to predict damage evolution but also residual strength. Studied materials are bi or tri axial glass fibre reinforced plastics fabrics. This work excluded joints areas where out of plane stresses generate strong coupling between intra and inter laminar damage. The main goals of the thesis are: - Identify on the material of the study damage mechanisms and their coupling in quasi-static and fatigue - Characterize and model residual stiffness caused by damage mechanisms - Characterize and model fatigue damage - Characterize and model residual strength caused by damage mechanisms - Implement and test the proposed model (or the one chosen in the literature and changed if necessary) in a computer FE code

This thesis deals with numerical simulation of a peel test with an Aluminium foil and Low Density Poly-Ethylene (LDPE) laminate. This work investigates the effects of the substrate thickness and studies the influences of interfacial strength and fracture energy of the cohesive zone between the Aluminium and LDPE. This study evaluates the proper guidelines for defining cohesive properties. A numerical cohesive zone model was created in ABAQUS. Continuum tensile tests were performed to extract LDPE material properties. The aluminium properties were found in literature. After acquiring material parameters, the simulation continued with studying the effects of changing interfacial strength, geometric parameters and fracture energy. The results were obtained in the form of root rotations and the force displacement response was studied carefully. It was validated by comparison to the traction separation curve.

O presente trabalho é um estudo qualitativo do comportamento mecânico do laminado metal-fibra GLARE-5 2/1, submetido a impacto balístico subsônico em condições que simulam à amplitude térmica em aplicações espaciais. Para isto, os corpos de prova foram submetidos e ao impacto balístico de um projétil cilíndrico e alguns destes foram submetidos ao choque térmico, alternando entre -196 e 100°C. Os danos causados por estes ensaios foram analisados com as técnicas de microscopia óptica e tomografia computadorizada de raios X (X-Ray CT), que permitiram o entendimento dos danos em duas e três dimensões. Comparouse o resultado entre estas técnicas e a influência do ordenamento das amostras no escaneamento deste material. Concluiu-se que a X-Ray CT é uma técnica não destrutiva que proporciona boa informação para o entendimento dos danos internos causados pelo impacto no GLARE, embora não replicou com exatidão os danos observados na microscopia óptica. Além disso, o agrupamento de amostras do GLARE para o escaneamento permitiu melhorar a qualidade das imagens resultantes destes escaneamentos. Os danos mais comuns causados pelo impacto foram delaminações metal-fibra, trincamentos na matriz polimérica e delaminações fibra-fibra, sendo a condição criogênica a que resultou em maior volume de danos. Amostras submetidas ao choque térmico mostraram uma queda de sua temperatura de transição vítrea e ganho na resistência ao impacto. / This is a qualitative study of the mechanical behavior of the metal-fiber laminate GLARE-5 2/1 subjected to subsonic ballistic impact under conditions that simulate thermal amplitude in space applications. For this, the specimens were submitted to the ballistic impact of a cylindrical projectile; some specimens were previously thermal shocked, alternating between - 196 and 100 ° C. The damages caused by these tests were analyzed by optical microscopy and X-ray CT (X-Ray CT), which allows the understanding of damage in two and three dimensions. Were compared the results between these techniques and the influence of the ordering of the samples in the scanning of this material. It was concluded that X-Ray CT is a non-destructive technique that provides good information for understanding the internal damage caused by impact on GLARE, although it did not replicate accurately the damage observed under light microscopy. In addition, GLARE sample collation for scanning has improved the quality of the images resulting from these scans. The most common damages caused by the impact were metal-fiber delamination, cracking in the polymer matrix and fiber-fiber delamination, the cryogenic condition being the result of greater damage. Samples subjected to thermal shock showed a drop in their glass transition temperature and gain in impact resistance.

Made available in DSpace on 2017-07-24T19:22:12Z (GMT). No. of bitstreams: 1 Joao Luiz Neves.pdf: 1812596 bytes, checksum: a76cbc76ce0b003aad7f933da512d1bd (MD5) Previous issue date: 2005-12-08 / The present work had the objective to evaluate the distribution of tensions in teeth restored with aesthetic porcelain laminates by the finites elements method, in representative models of upper incisors central, where three types of simulation had been used: teeth that did not present dental preparations with and without covering of the incisal edge, and teeth that had preparation in shoulder form and layering of the incisal edge. These models had been submitted to the loads of 100N and 350 N in the incisal edge, under angles of 450 and 900, simulating clinical conditions of carrying patients of class I of the Angle and patients with direct bite of the incisors and/or bruxomanos. We observed that the increase of the load, as well as the reduction of the angulations, had promoted an increase to the tensions in the representative models of porcelain laminate, and that the models represented by the lithium dissilicato porcelain, presented a better behavior in relation to the distribution of the tensions on teeth restored with feldspática porcelain laminate. / O presente trabalho teve por objetivo avaliar a distribuição de tensões nos dentes restaurados com facetas estéticas de porcelana pelo método de elementos finitos, em modelos representativos de incisivos centrais superiores onde foram utilizadas três tipos de simulações: dentes que não apresentavam preparos dentários com e sem recobrimento da borda incisal, e dentes com preparo em forma de ombro e com recobrimento da borda incisal. Estes modelos foram submetidos a cargas de 100N e 350 N na borda incisal, sob angulações de 450 e 900, simulando condições clínicas de pacientes portadores de classe I de Angle e pacientes com mordida de topo e/ou bruxomanos. Foi observado que o aumento de carga, bem como a diminuição da angulação, promoveu um aumento das tensões nos modelos representativos das facetas de porcelana, e que os modelos representados pela porcelana à base de dissilicato de lítio, apresentou um comportamento melhor em relação à distribuição das tensões sobre os dentes restaurados com facetas de porcelana feldspática.

O presente estudo tem como objetivo principal desenvolver um compósito cimentício reforçado com fibras de arumã. O intuito é agregar valor a uma planta típica da região Amazônica, denominada arumã, pertencente à espécie do gênero Ischnosiphon arouma (aubl) Korn e originária da família Maranthaceae, de tal modo que possa ser obtido um Novo Material. Na primeira etapa do estudo foi realizada a caracterização da fibra vegetal de arumã e de todos os componentes da matriz cimentícia, a qual compreendeu ensaios químicos, físicos e mecânicos para a investigação e avaliação de suas propriedades. Na etapa seguinte, adotou-se o procedimento de trabalhar as características físicas e mecânicas das fibras junto à matriz cimentícia, compreendendo um estudo da modificação superficial da fibra por meio de tratamentos químicos à base de soluções de hidróxido de sódio ou utilizando processos com água quente e hornificação. Na terceira etapa, foram produzidas placas reforçadas com fibras sem e com tratamento, as quais, parte delas foram submetidas à cura por 28 dias e as restantes ao ensaio de envelhecimento acelerado. Os resultados obtidos na caracterização das fibras de arumã indicam o seu potencial uso como elemento de reforço para compósitos cimentícios. Por outro lado, os compósitos produzidos com telas de fibra de arumã sem e com tratamento (hornificação e alcalino), apresentaram comportamento pouco dúctil e com baixa resistência, como consequência da degradação das fibras na matriz cimentícia. Isso foi confirmado por meio de ensaios de envelhecimento acelerado com ciclos de molhagem e secagem. / This present study aims to develop a cementation composite reinforced with arumã fiber. The aim is to aggregate value to a typical plant of the Amazon region, called arumã, belonging to species of the genus Ischnosiphon arouma (Aubl) Korn and originally from Maranthaceae family, so that, it can be obtained a New Material. In the first stage of the study was performed the characterization the vegetable fiber arumã and all components of the cementicious matrix, which comprised chemical, physical and mechanical tests for research and evaluation of their properties. In the next stage, it was adopted the procedure of working the physical and mechanical characteristics of the fibers with the cementitious matrix comprising a study of the surface of the fiber modification by chemical treatments using sodium hydroxide solution or employing procedures with hot water and hornification. In the third step, the reinforced plates were produced without and with treatment, which, part of were subjected to cure for 28 days and the remaining subjected to the accelerated aging test. The results obtained in the characterization of arumã fibers indicate its potential use as a reinforcement element for cementicious composites. On the other hand, the composites produced with arumã fiber fabrics without and with a treatment (hornification and alkaline) showed slightly ductile behavior and low strength as a result of degradation of fibers in the cementitious matrix. This was confirmed through accelerated aging tests with wetting and drying cycles.

Les structures aéronautiques sont aujourd’hui largement réalisées à partir de matériaux composites, permettant ainsi d’en diminuer la masse. L’impact sur structure composite est une des sources de dommage la plus courante et la plus pénalisante. L’objectif de cette thèse est de développer un modèle prédictif d’impact sur stratifiés unidirectionnels de faible épaisseur afin, dans un premier temps, de mieux comprendre les mécanismes d’endommagement mis en jeu et, dans un deuxième temps, de pouvoir proposer des pistes d’amélioration de la tenue de ces structures. La première étape de ces travaux a consisté à développer un modèle éléments finis explicite de stratifiés composite unidirectionnel, en s’appuyant sur les travaux d’impact sur pale d’hélicoptère réalisés par F. Pascal. Ainsi, un nouvel élément capable de représenter le comportement à l’impact des plis unidirectionnels a été formulé. Le comportement des paquets de fibres est représenté par des éléments barres stabilisés grâce à des éléments 2D spécifiques. La dégradation de ces éléments est pilotée par des lois d’endommagement déduites d’observations expérimentales. La stratégie de modélisation proposée a été identifiée sur la base d’essais expérimentaux pour deux matériaux : T700/M21 et HTA7/913. Les résultats donnés par le modèle ont ensuite été validés par une comparaison avec des essais d’impact à basse vitesse. Enfin, dans le but d’optimiser la tenue des stratifiés, des impacts à basse et moyenne vitesse sur des stratifiés hybrides unidirectionnels/tissus composites ont été étudiés expérimentalement et numériquement grâce à la stratégie de modélisation proposée. / Today, composite materials are largely used in the manufacturing of aeronautical structures, in order to lighten their weight. Impact on composite structures is one of the most detrimental loading. The present study aims to develop a predictive modelling of impacts on thin unidirectional laminates in order to, firstly, better understand the damage mechanisms involved, and, secondly, be able to provide guidance for a strength improvement of these structures. First, an explicit finite element modelling of unidirectional laminates is developed based on the work of F Pascal dealing with impact modeling on helicopter blades. Thus, a new element that can represent the impact response of unidirectional plies is formulated. The behavior of the bundle of fibers is modeled with rod elements stabilized with specific 2D elements. The degradation is managed using damage based on experimental observations. The parameters of the proposed modelling strategy are identified on the basis of experimental tests carried out on T700/M21 and HTA7/913 composites. The results provided by the modeling are then validated by a comparison with experimental low velocity impact results. Finally, in order to improve the laminate strength, low velocity and medium velocity impacts on hybrid unidirectional/woven composite laminates are studied experimentally and with the developed modelling strategy.