Orientador: Cecília Amélia de Carvalho Zavaglia / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T16:53:54Z (GMT). No. of bitstreams: 1 Galdino_AndreGustavodeSousa_D.pdf: 8544982 bytes, checksum: 9bbd7c8f53578d5a0a79aeec90ea4222 (MD5) Previous issue date: 2011 / Resumo: À medida que há uma melhoria na tecnologia aplicada à saúde humana, a expectativa de vida vem aumentando, mas nem todas as partes do corpo podem manter suas funções com o processo de envelhecimento. É preciso que os ossos e a cartilagem apóiem o envelhecimento do corpo, embora as células que os produzem se tornem menos ativas com o tempo. Outros órgãos, tais como os rins, o coração e o fígado devem ser operados para ter um tempo de vida maior. A engenharia tecidual foi desenvolvida para substituir, reparar ou reconstruir tecidos ou órgãos perdidos ou danificados por acidentes ou doenças graves através da utilização e desenvolvimento de novos materiais, que sejam biocompatíveis, bioabsorvíveis, porosos, entre outras características. Os scaffolds são arcabouços tridimensionais porosos e são utilizados na regeneração de tecidos para seu estado natural e suas funções, que é fundamental para a engenharia tecidual. Eles podem ser classificados em arcabouços que induzem a migração e o crescimento celular e em arcabouços carreadores de células osteogênicas autógenas, que foram colonizadas em biorreatores e subsequentemente reimplantadas no paciente. Tais scaffolds podem ser naturais ou sintéticos. O objetivo deste trabalho é avaliar o compósito poroso de hidroxiapatita - titânia (HATiO2), em três composições diferentes (50% HA - 50% TiO2, 60% HA - 40% TiO2, 70% HA - 30% TiO2) para obter scaffolds utilizados para engenharia tecidual óssea. Os corpos de prova foram produzidos pelo método da esponja polimérica, utilizando bicarbonato de sódio como ligante e floculante. A sinterização foi realizada em três temperaturas: a 1250ºC; 1300ºC e 1350ºC. As propriedades analisadas foram: resistência à compressão e dureza através das normas da ASTM, porosidade aparente, densidade aparente, retração linear de queima e absorção de água, pelo método de Souza Santos para argilas. Os resultados obtidos mostraram-se bastante satisfatórios, onde foi mostrado que os corpos cerâmicos porosos obtiveram valores de resistência à compressão e dureza coerentes com os da literatura e superiores aos da hidroxiapatita pura. Realizou-se também uma caracterização estrutural das amostras via difração de raios - x (DRX), microscopia eletrônica de varredura (MEV) e espectroscopia por infravermelho com transformada de Fourier (FT-IR). Com base nos resultados mecânicos e de caracterização estrutural, foi escolhida a amostra com composição de 50% HA - 50% TiO2 sinterizada a 1350ºC para realização de ensaios in vitro, onde foram avaliadas citotoxicidade e crescimento celular de osteoblastos e fibroblastos de camundongos. Os resultados indicaram que o compósito é biocompatível e que as células cresceram nos scaffolds. De forma geral, pode-se concluir que todas as amostras são indicadas para a utilização como matéria prima para aplicação em engenharia tecidual óssea. A amostra com 50% HA - 50% TiO2 apresentou melhores características para a realização dos ensaios in vitro realizados neste trabalho e pode-se indicar esta para a realização de ensaios in vivo, onde devem ser avaliadas as características de citotoxicidade e crescimento de células ósseas em animais, por um período de 15 e 30 dias, conforme normas da área de saúde / Abstract: As we witness an improvement in the technology applied to human health, life expectancy increases, even though not every part of the body can maintain their functions with the aging process. It is necessary that bones and cartilage support the body's aging, even if the cells that produce them become less active with time. Other organs, such as kidneys, heart and liver must be operated to have a higher lifetime. Tissue engineering has been developed in order to replace, repair or rebuild tissues or organs lost or damaged due to accidents or serious diseases through the use and development of new materials that are biocompatible, bioabsorbable, with porosity among other characteristics. Scaffolds are a kind of porous tridimensional net and they are used on tissues regeneration to their natural state and functions, which is fundamental for tissue engineering. They can be classified as scaffolds that induce migration and cell growth and as carrier scaffolds for autogenous ostheogenic cells, which were colonized inside bioreactors and then redeployed on the patient. Those scaffolds can be natural or synthetic. This research aimed to evaluate hydroxyapatite-titanium oxide (HA-TiO2) with three different compositions (50% HA - 50% TiO2, 60% HA - 40% TiO2, 70% HA - 30% TiO2) to obtain scaffolds used for bone tissue engineering. Samples were made by the polymeric sponge method, using sodium bicarbonate as a binder and flocculating agent. Sintering was carried out at 1250ºC; 1300ºC e 1350ºC. It was analyzed compressive strength and Vickers hardness using ASTM Standards, apparent porosity, apparent density, burning linear retraction and water absorption by Souza Santos method used for clays. Results proved satisfactory showing that ceramic bodies obtained compressive strength and Vickers hardness according to literature and higher than those for pure hydroxyapatite. Samples structural characterization was done by x-ray diffraction (XRD), scanning electronic microscopy (SEM) and Fourier transformed infrared (FT-IR). It was chosen 50% HA - 50% TiO2 sintered at 1350ºC based on its mechanical properties and structural characterization and in vitro essays were done to evaluate citotoxicity and mouse osteoblasts and fibroblasts cell growth. Results have shown that the composite is biocompatible and the cell growth above scaffolds surface. In general, samples can be recommended for use as raw material for bone tissue engineering application. The sample with 50% HA - 50% TiO2 showed better characteristics for in vitro essays done and it can be recommended for in vivo essays where citotoxicity and bone cell growth in animals during 15 and 30 days, according to health standards / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

This thesis gives a comprehensive characterization of lightweight non-oxide ceramic materials for ballistic applications, an overview of production technologies and processing of boron carbide B4C and its ceramic-based composites. A framework for evaluating the ballistic resistance of the material based on mechanical properties is shown there. It can be used in experiments without normalized equipment. The experiments including B4C + Si, B4C + Ti composites, and application of Spark plasma sintering (SPS) were designed according to outputs from the theoretical part. The volume fractions of Si, Ti dopants were optimized based on ongoing chemical reactions during sintering. The obtained samples were subjects of mechanical testing which results were compared to identify the ideal ratio of matrix and reinforcement. As the best suited material for ballistic protection, B4C + 1,0 obj. % reaches these values of parameters; hardness = 3502 ± 122 HV1; fracture toughness KIC = 2,97 ± 0,03 MPam^0,5.

The role of an interfacial barrier at the fiber-matrix interface in the heat conduction behavior of an uniaxial silicon carbide fiber-reinforced reaction-bonded silicon nitride and the effect of fiber orientation on the heat conduction characteristics of carbon fiber-reinforced borosilicate glass was investigated. In the study of the effect of an interfacial thermal barrier, a composite with fibers having a carbon-rich coating of about 3 J.l m was chosen as the reference material. The fiber-matrix interface was then modified by preferential oxidation of the carbon coating on the fibers, using fibers with no carbon coating and using hotisostatic-pressing (HIP) after nitridation. The formation of an interfacial gap at the interface due to thermal expansion mismatch between the fiber and the matrix in reference and HIP'd composites, and removal of carbon coating for oxidized composites, resulted in the dependence of thermal diffusivity/conductivity on the surrounding . atmosphere. This effect was attributed to gaseous heat transfer at the interface. However, no atmospheric effects were observed for composites with fibers without the carbon coating due to very strong bonding between the fiber and the matrix. HIP'ing increased the thermal diffusivity/conductivity of the composites due to densification of the matrix, crystallization of the fibers and increased physical contact at the interface. Removal of the interfacial carbon layer by preferential oxidation lowered the interfacial conductance considerably, due to decrease in the direct thermal contact between the fibers and the matrix. Interfacial contact conductance determined from measurements made in vacuum for reference and HIP'd composites increased rapidly with increasing temperature in accordance with interfacial gap closure. These observations indicate that the heat conduction behavior of all the composites investigated was strongly affected by the existence of an interfacial thermal barrier, for heat transfer transverse to the fiber direction. / Ph. D.

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To achieve satisfactory levels of strength, fracture toughness, and reliability for man-rated systems such as jet engines, fiber reinforced ceramic matrix composites are needed. An elevated temperature axial testing system is developed to investigate and characterize fatigue behavior of Nicalon fiber reinforced enhanced silicon carbide matrix. composites at 1800 of under fully reversed cyclic loading. Notch effect on quasi-static tensile response is also considered. Quasi-static and fatigue damage mechanisms and failure modes are examined using various specimen geometries, load levels, fatigue ratios, and laminates stacking sequences by employing a number of NDE techniques. Issues such as damage tolerance and durability are addressed by conducting interrupted fatigue tests at various stages of life for different load levels. Results are compared to the predictions of remaining strength and life, obtained using a performance simulation code. Initial results indicate existence of a threshold stress value which limits the use of the material system. / Ph. D.

Les composites à matrice céramique sont utilisés dans les moteurs aéronautiques en raison de leur stabilité à haute température et de leurs propriétés mécaniques. Cependant, quand ils sont soumis à des environnements sévères (haute température, haute pression, environnement oxydant et humide), ils s'oxydent et se dégradent dû à la volatilisation de la silice protectrice formée en surface par oxydation du CMC. Par conséquent, pour augmenter la durée de vie de ces matériaux, il est nécessaire d'appliquer une protection externe contre la corrosion. Ceci constitue l'objectif de ma thèse. La démarche expérimentale a été la suivante : (i) identification des matériaux de revêtement à étudier ; (ii) validation du choix des matériaux par étude de leur stabilité structurale et de leurs compatibilités chimique et thermomécanique avec le substrat ; (iii) étude de la stabilité des matériaux de revêtement sous atmosphère corrosive et enfin (iv) comportement des revêtements sur composites. / The ceramic matrix composites can be used in aeronautic engines due to their high temperature stability and their mechanical properties. However, under a corrosive environment, an oxidation and then a recession of the CMC occured because of the volatilization of the silica scale formed at the surface of the composite. Consequently, in order to increase the lifetime of such materials, a external protection against corrosion is required. This is the aim of my Ph-D thesis. The experimental approach is the following : (i) identification of the coating materials ; (ii) validation of the selected materials by studying their structural stability and their chemical and thermomechanical compatibilities with the substrate ; (iii) determination of the thermal stability of the materials under a corrosive environment and (iv) behaviour of the coatings onto the CMC.

Cette thèse s‘inscrit dans le contexte de l‘étude de matériaux fibreux tissés et traite de l‘analyse morphologique de leur texture et de la simulation des arrangements des fibres dans un fil. Le volet « analyse » consiste à extraire des données caractérisant la géométrie des fibres et des fils composant le renfort tissé et s‘appuie sur des images tridimensionnelles issues de tomographies rayon X à haute résolution. Une chaine de traitement d‘images visant à séparer et identifier les fils et les fibres est proposée. Elle s‘appuie sur un algorithme de labellisation du fil et des fibres. Les caractéristiques telles que les diamètres et les orientations de fibres et la densité locale de fibres dans le fil sont ensuite calculées. Le volet « simulation » vise à générer un renfort fibreux « virtuel ». Un algorithme fondé sur la résolution de modèles dynamiques permet de placer au sein d‘un fil, des objets représentant les fibres tout en respectant des contraintes issues des paramètres issus du volet « analyse » ou choisis arbitrairement par l‘utilisateur. L‘ensemble des fibres composant le fil sont alors synthétisés en respect de ces contraintes. Ces deux volets sont appliqués avec succès à la caractérisation et à la synthèse de renforts fibreux de composites thermostructuraux. Les caractéristiques géométriques, estimées sur des tomographies à haute résolution, font ressortir des phénomènes tels que le cisaillement intra fils. La synthèse permet de simuler le placement de fibres à partir de paramètres géométriques obtenus à haute résolution, au sein d‘un fil dont l‘enveloppe est obtenue à basse résolution et donc sur une longueur plus représentative du tissage. / The aim of this work is to study fibrous woven materials and to develop morphological analysis of their texture enabling simulation of fibrous layout in yarns. The ―analysis‖ stage consists in data extraction to characterize the geometry of fibers and yarns constituting the woven material, based on tridimensional images generated by high resolution X-ray tomography. An image processing workflow to separate and identify fibers and yarn is proposed. Then, diameters, fiber orientations and local fiber density in yarns are computed. The ―simulation‖ stage targets to generate virtual fibrous materials. An algorithm based on the resolution of a dynamic model allows placing objects representing fibers into a yarn. It uses as input the characteristic parameters previously extracted in the analysis stage or arbitrarily chosen ones. Consequently, all fibers are synthesized according to these constraints. These two stages are successfully applied to characterize and synthesize woven ceramic matrix composites. Geometrical characteristics, extracted from the high-resolution tomographic images, highlight yarn phenomena like shearing planes. The synthesis simulates fibers placement, merging geometrical parameters extracted on high and low resolution. Indeed, using fiber parameters extracted from high resolution images and yarn envelopes from low resolution ones enable generating a result with a more representative woven length.

Les matériaux composites à matrice céramique (CMC) sont élaborés à partir de constituants fragiles. Le comportement mécanique et le développement de la fissuration dépendent des propriétés des constituants élémentaires des CMC. La connaissance de l’influence de ces propriétés sur l’évolution de la fissuration et du comportement mécanique fournit une aide au concepteur de matériaux composites.L’objectif de ce travail est de modéliser l’évolution du réseau de fissures au sein du CMC sollicité en traction, à l’échelle du fil et à l’échelle du composite tissé. L’approche proposée est une alternative aux principaux modèles de comportement des CMC.A l’échelle du fil, l’endommagement intervient d’abord sous forme de fissures matricielles accompagnées de décohésions à l’interface fibre/matrice. Les analyses de ces deux mécanismes ont permis d’exprimer leur évolution au sein du fil en traction. Le comportement en traction résultant de l’endommagement et l’ouverture de la fissure matricielle sont aussi exprimés semi-analytiquement.Les comparaisons avec un modèle numérique de zones cohésives et avec les essais expérimentaux montrent une bonne corrélation des résultats.Enfin ces expressions à l’échelle du fil sont utilisées pour modéliser l’endommagement du fil longitudinal au sein du composite tissé en traction. De plus, un outil numérique est développé pour modéliser la fissuration matricielle inter-fil dans le composite tissé. / Ceramic matrix composite materials (CMC) are elaborated from fragile constituents. Their mechanical behaviour and crack growing depend on the properties of the CMC elementary constituent. Knowing the influence of these properties on crack development and mechanical behaviour provides support to the composite material designer.This work aims at modelling the crack networks development within the CMC under axial tension, at the yarn scale as well as at the woven composite scale. The proposed approach is an alternative to the main CMC behaviour models.At the yarn scale, matrix cracking with interfacial debonding between fiber and matrix first happen. Both mechanisms are analysed and their development are expressed. The mechanical behaviour resulting from damage and the crack opening displacement are also described using semi-analytical equations. Comparisons with numerical cohesive zone model and also with experimental testing shows good correlation between results.These semi-analytical expressions are then used for modelling damage within each yarns at the woven composite scale. In addition, a numerical tool is developed for matrix cracking and interfacial debonding between yarns of the woven composite.