Orientador: Paulo Sollero / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-26T08:57:24Z (GMT). No. of bitstreams: 1 Moraes_DiogoHenrique_M.pdf: 3925862 bytes, checksum: 0c710a62aec995319f0a11e957f58a83 (MD5) Previous issue date: 2014 / Resumo: Este trabalho apresenta uma análise numérica de falha em laminados unidirecionais de materiais compósitos baseado na modelagem multiescala de materiais heterogêneos. A abordagem empregada considera o material em duas escalas, nas quais os problemas elásticos de cada uma são resolvidos para descrever o comportamento mecânico do laminado. Na macroescala (escala global), formulações de elasticidade plana anisotrópica do Método dos Elementos de Contorno (MEC) foram utilizadas para calcular os campos de deformação e de tensão no domínio da lâmina. Esses campos representam os tensores macroscópicas da estrutura, dos quais são usados para calcular as condições de contorno na microescala (escala local). Nesta escala, equivalente a um ponto material da estrutura (técnica de localização), um Elemento de Volume Representativo (EVR) é tomado para dar satisfatoriamente o comportamento constitutivo global. A solução do problema elástico do EVR, composta por uma matriz isotrópica e uma fibra transversalmente isotrópica, e a aplicação da teoria dos Campos Médios, também foram realizadas utilizando o MEC através da formulação de sub-regiões. A avaliação da falha nos microconstituintes foi feita utilizando o critério de Tsai-Hill para a matriz e o critério da máxima deformação para a fibra. Os resultados para exemplos numéricos são apresentados, discutidos e comparados com resultados numéricos obtidos pelo critério de falha de LARC03 realizando análise apenas na escala estrutural / Abstract: This work presents a numerical analysis of failure in unidirectional laminates of composite materials based in multiscale modelling of heteregeneous materials. The approach assumes the material in two scales, in which the elastic problems are solved to describe the mechanical behavior of the laminate. In the macroscale (global scale), the Boundary Element Method (BEM) for anisotropic plane elasticity was used to evaluate strain and stress fields in the domain of the lamina. These fields represent the macroscopic tensor of the structure, which is used to evaluate the boundary conditions in the microscale (local scale). This scale, equivalent to a material point of the structure (localization technic), a Representative Volume Element (RVE) is taken to satisfy the constitutive overall behavior. The solution of the elastic problem of the RVE, is composed by an isotropic matrix and a transversely isotropic fiber, and the application of the Mean Fields theory, have been realized by BEM through the multi-region formulation. The evaluation of failure in the microconstituents was made using failure criteria of Tsai-Hill for matrix and the maximum deformation criterion for fiber. The results for numerical examples are presented, discussed and compared with numerical results obtained by the LARC03 failure criterion performing the analysis only on the structural scale / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Orientador: Maria Helena Robert / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T10:48:15Z (GMT). No. of bitstreams: 1 Ferreira_LygiaMariaPolicarpio_M.pdf: 14529538 bytes, checksum: f34c04de7772ea86ea3d164ba7a34c41 (MD5) Previous issue date: 2013 / Resumo: Este trabalho explora a aplicação da tecnologia de metais semi-sólidos para a fabricação de compósitos de matriz metálica (CMM), e ainda a possibilidade de reciclagem de cavacos de usinagem para a produção destes materiais, buscando o desenvolvimento de uma engenharia de baixo custo. São empregados como matriz a liga AA7075, dada a grande geração de cavacos de usinagem na indústria aeronáutica, e SiC ou NiAl2O4 particulados como reforços. O processo é baseado na tixoconformação de misturas de cavacos e partículas de reforço; é esperada a penetração destas últimas em contornos de glóbulos, contendo líquido, no interior do cavaco no estado semi-sólido. São avaliados parâmetros de processo e sua influência na qualidade do produto, em particular na distribuição de reforço na matriz e interação matriz/reforço. Compósitos tixoconformados contendo 10, 20 e 30% em peso de SiC são avaliados mecanicamente através de ensaios de microindentação instrumentada e desgaste micro-abrasivo. Os resultados mostraram, de modo geral, a viabilidade do processo proposto para a fabricação de diferentes tipos de compósitos, o qual envolve procedimento simples e de reduzido custo, além de mostrar a possibilidade de produção de materiais com boas propriedades mecânicas a partir da reciclagem de cavacos, particularmente importante em uma indústria que envolve elevada demanda de energia, como a do Al. Os resultados indicaram que a qualidade geral do produto, em termos de distribuição do reforço e interação reforço/matriz dependem da adequada seleção dos parâmetros de processo: temperatura, tempo de aquecimento, pressão de tixoconformação. Entre as várias condições estudadas, as composições nas quais foi utilizado NiAl2O4 como reforço apresentaram melhores características microestruturais, com melhor interface entre matriz e reforço e baixa porosidade. Boa dispersão das partículas de reforço e baixa porosidade também foram observados para compósitos reforçados com SiC nos quais foram adicionadas partículas finas de silício e alumina / Abstract: This work explores the application of semi-solid technology to produce metal matrix composites, and also the possibility of using machining chips as raw material. The main aim is to develop a process inserted in a low cost engineering concept. To achieve this general objective, the alloy AA7075 is used as matrix, once a significant amount of rejected chips of this high resistance, low weight alloy is generated in the aeronautical industry. As reinforcing material, SiC or NiAl2O4 particles are used. The proposed process is based on the thixoforming of pre-compacted mixtures of chips and reinforcing particles; it is expected the penetration of reinforcing particles within the semi-solid, thixotropic material. It is analyzed the influence of processing parameters in the final quality of products, particularly in the reinforcement dispersion in the matrix and matrix/reinforcement interface. Thixoformed composites containing 10, 20 and 30% weight SiC are produced and evaluated concerning mechanical properties through indentation tests and micro wear. Results showed the general viability of producing composites by the proposed technique, based on a simple and low cost procedure. It was also shown the possibility of producing materials with good mechanical properties from recycled chips, which is particularly important in the high energy demanding Aluminium industry. Results showed the importance of choosing appropriate processing parameters (temperature, heating rate / soaking time and thixoforming pressure), to achieve desired product quality. Among the various conditions studied, the compositions in which NiAl2O4 was used as reinforcement showed better microstructural characteristics with better interface between matrix and reinforcement, and lower porosity. Good dispersion of the reinforcement particles and low porosity were also observed for SiC reinforced composites in which fine particles of silicon and alumina were added / Mestrado / Materiais e Processos de Fabricação / Mestra em Engenharia Mecânica

Orientador: Newton de Oliveira Pinto Júnior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-20T18:06:18Z (GMT). No. of bitstreams: 1 Carvalho_Eduardo_M.pdf: 25185254 bytes, checksum: 7474c91f52a8871bcfb855ccfe3c27b7 (MD5) Previous issue date: 2012 / Resumo: O concreto reforçado com fibras de aço (CRFA) tem seu principal campo de aplicação nos pisos industriais e pavimentos. Em função das características de redistribuição de esforços que apresentam tais estruturas - placas apoiadas sobre uma base elástica - é possível a substituição total das armaduras convencionais pelas fibras de aço, acelerando o processo executivo e garantindo sua segurança e durabilidade. A introdução das fibras de aço nos concretos tem como principal função modificar o comportamento do compósito quando solicitado a esforços de flexão, transformando um material de natureza frágil em dúctil, ou seja, com capacidade de absorção de energia. A ductilidade desse compósito é usualmente quantificada pela medida de tenacidade do material em ensaios de tração na flexão, obtida com velocidade de deformação controlada, condição fundamental para avaliação do comportamento do compósito após sua fissuração. É importante salientar que a tenacidade do CRFA é fortemente influenciada pela distribuição das fibras na matriz de concreto, distribuição esta que é sensivelmente diferente em corpos de prova prismáticos moldados, utilizados para o controle de qualidade da obra, do que a encontrada nas estruturas dos pisos ou pavimentos. As propriedades do CRFA são expressas assumindo essa distribuição randomizada das fibras. Não obstante, em corpos de prova de tamanhos padronizados, ocorrem os efeitos de parede, também chamados de efeitos de borda. Esses efeitos consistem no alinhamento das fibras junto ao fundo e às laterais do corpo de prova, tornando o arranjo das fibras de aço nesses locais comprometido em virtude desses efeitos de parede. Com isto ocorre um aumento induzido no desempenho do compósito dado o alinhamento das fibras à direção principal de tensão durante a flexão. Buscando analisar a influência que a distribuição das fibras tem sobre a tenacidade do material, foram moldadas placas com dimensões que simulem os pisos e pavimentos (com três distintos teores de fibras: 20, 30 e 40 kg/m³), das quais foram extraídos prismas para determinação da suas tenacidades, que serão comparadas com as obtidas em prismas moldados. Os resultados foram cotejados estatisticamente, através da análise de variância, para estabelecimento das correlações existentes e suas influências sobre a tenacidade do compósito. Não há norma nacional para ensaios e utilização do CRFA que especifiquem e normatizem o seu uso. Dessa maneira, em virtude dos resultados dos valores de tenacidade terem sido com grande variabilidade, propusemos valores característicos para serem utilizados no controle executivo de obra / Abstract: The steel fiber reinforced concrete (SFRC) has in the industrial slabs-on-ground and the pavements its main field of application. Regarding the features of such structures and the redistribution of the resulting forces - slabs supported on elastic base - the complete substitution of the conventional armors for steel fibers has been possible saving time of the executive process, nevertheless security and durability also guaranteed. The introduction of steel fibers in the concrete has the mainly feature of modifying the behavior of the composite when requested the flexural efforts, transforming a material of fragile nature into ductile, which means; with capacity of energy absorption. The ductility of this composite usually is quantified by the measurement of the thoughness of the material in tensile stress in the flexural tests, obtained by controlled speed deformation, basic condition for evaluation of the behavior of the composite afterwards fissuration. It is important to point out that the toughness of the SFRC is mainly influenced by the distribution of fibers in the concrete matrix, distribution that is significantly different in prismatic specimen molded, used for the control of the quality of the construction, of what found in the structures of the slabs-on-ground and the pavements. The properties of the SFRC are express assuming this randomly distribution of the fibers. However, in specimen of standard sizes the wall effect occurs, also calls of edge effect. These effects consist in the alignment of the fibers next to botton and to the laterals of the specimen. This occurs with an induced increase in the performance of the composite given the alignment of fibers on the main direction of tension during flexion. In this way, an induced increase in the performance of the composite given the alignment of staple fibers to the main direction of tension occurs during the flexural test, becoming the arrangement of steel fibers in these places compromised due to these wall effects. Searching to analyze the influence that the distribution of staple fibers has on the toughness of the material, plates with dimensions were molded that simulate the slabs-onground and pavements (with three distinct staple fiber texts: 20, 30 and 40 kg/m³), of which prisms for determination of its toughness will be extracted, that will be compared with the gotten ones in molded specimen. The results will be statistically analyzed through the analysis of variance for establishment of the existing correlations and its influences on the toughness of the composite. There is no national standard for testing and use of the SFRC that specify and regulate their use. Thus, given the results of toughness values have been with great variability, we propose characteristic values for the application in executive control of building works / Mestrado / Arquitetura e Construção / Mestre em Engenharia Civil

Orientador: Cecilia Amalia de Carvalho Zavaglia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-24T19:52:40Z (GMT). No. of bitstreams: 1 LopezPalacio_RaulErnesto_M.pdf: 4817935 bytes, checksum: b634da0ffd4f08cb1716f7bfe6bbf6c5 (MD5) Previous issue date: 1998 / Resumo: Este trabalho teve comoobjetivoprincipala otimizaçãoda formulaçãoe a caracterizaçãode compósitosde matriz polimérica,reforçadoscom partículasde quartzo, para uso em odontologia com cura fotoquímica e química.Na otímízação da formulação foi determinada a relação par iniciador-monômero,relação misturaíniciadora-cargae a distribuiçãodo tamanho das partículas de carga. No processo de avaliação foram determinadas s propriedades fisico-mecânicas,segundo a metodologia descrita na norma I.S.O. 4049(1),e a dependência dessas determinações com as condições experimentais. Realizou-se um estudo complementar para determinar a relação microestrutura-propriedades mecânicas fazendo uso da Microscopia Eletrônica de Varredura. Os resultados obtidos permitem afirmar que os compósitos obtidos cumprem com todos os requisitos fisico-mecânicos exigidospara ser utilizados como obturantes dentários. Além disto concluiu-seque os valores obtidosdo comportamento mecânico dos compósitos são relativos, pois os mesmos dependem das condições experimentais.O estudo microestrutural demostrou que, além da dureza da carga, as variações no comportamento mecânico destes materiais com a porcentagem de carga dependem da interface monômero-carga formada no compósito / Abstract: This paper presents the characterization and evaluation of light and chemical cured composites. In the optimizationformulation a initiator-monomer relationship, a monomer-filler relationship and a distribution of size of the filler particles were determinate . In the evaluation process the mechanical and physical properties were obtained, along with result the dependence of those results with the experimental conditions. The methodology used was the one detined in 1. S. O 4049. A supplemental study to obtain the microstructural-mechanical properties relationship by making use of the Scanning Electronic Microscopy was accomplished. The results showed that the obtained composite complied with alI the physicalmechanical requirements, demanded for the dental resin-based restorative materials. Another conclusion was that the mechanical behavior of the composites are relative, because the same ones depend on the experimental conditions. The micro-structural study proved that the variations in the mechanicalproperties with the filler concentration depend on the hardness of the filler and the monomer-fillerinterface formed in the composite / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Ph.D. (Chemistry) / This study focuses on the morphology and crystal-growth behaviour of polyactide (PLA)-based blends and blends modified with organoclay thin films. The study further examined the effect of blending and the incorporation of organoclays on the enzymatic degradation behaviour. Thin films of unmodified and nanoclay-modified PLA/poly(butylene succinate) (PBS) blends were cast on a glass substrate by a spin coater, while thin films of biodegradable PLA/poly[(butylene succinate)-coadipate] PBSA blends and blends containing organoclays were cast on a silicon (100) wafer substrate. The morphology and crystal growth behaviour of the thin films crystallized at different temperatures were examined with an atomic force microscopy (AFM) equipped with a hot-stage scanner. In PLA/PBS blend thin films, AFM images showed that the size of the dispersed PBS phase was influenced by C30B clay loading on the blends. The dispersed size reduced on the addition of C30B clay up to 2 wt%, beyond which, dispersed size began to increase. Transmission electron microscopy studies indicated that this behaviour was due to the preferential location of silicates in the PBS phase than in the PLA phase. For thin films annealed at 60 °C, the additi on of organoclays to the blend quenched the growth of edge-on lamellae. The crystalline morphologies at 120 °C were dominated by edge-on lamellae grown, around the PBS phase to form spherulites. Morphologies of thin films crystallized at 120 °C from melt were dominated by the flat-on lamellae, while those crystallized at 70 °C from melt were dominated by the edge-on lamellae. In the case of PLA/PBSA blend thin films, the results indicated that the size and distribution of the dispersed phase were directly related to the blend composition. The crystal growth behaviours indicated the presence of homogeneous and heterogeneous nucleations, and the nature of nucleation was directly related to the blend ratio and the temperature at which crystallization occurred. Therefore, this study will facilitate the understanding of crystal growth behaviour in a confined environment and will enable the modulation of the blend properties.

En mécanique des matériaux et des structures, l’interface entre deux composants matériels ou deux éléments structuraux est traditionnellement et le plus souvent supposé parfaite. Au sens mécanique, une interface parfaite est une surface à travers laquelle le vecteur de déplacement et le vecteur de contrainte sont tous les deux continus. L’hypothèse des interfaces parfaites est inappropriée dans de nombreuses situations en mécanique. En effet, l’interface entre deux corps ou deux parties d’un corps est un endroit propice aux réactions physico-chimiques complexes et favorable à l’endommagement mécanique. L’intérêt pour les interfaces imparfaites devient depuis quelques années grandissant avec le développement des matériaux et structures nanométriques dans lesquels les interfaces et surfaces jouent un rôle prépondérant. A partir de la configuration de base où une interphase de faible épaisseur sépare deux phases, ce travail établit trois modèles d’interface imparfaite généraux qui permettent de remplacer l’interphase par une interface imparfaite dans les cas de la conduction thermique, de l’élasticité linéaire et de la piézoélectricité sans perturber les champs en questions à une erreur fixée près. La dérivation de ces modèles est basée sur le développement de Taylor et sur une approche originale de géométrie différentielle indépendante de tout système de coordonnées. Les trois modèles généraux permettent non seulement de mieux appréhender certains modèles phénoménologiques d’interface imparfaite mais aussi de décrire les effets d’interface que les modèles existants ne sont pas en mesure de prendre en compte. Les modèles d’interface imparfaite établis sont appliqués dans la détermination des propriétés effectives thermiques, élastiques et piézoélectriques d’un matériau composite constitué d’une matrice renforcée par des particules ou fibres enrobées d’une interphase. La méthode utilisée pour rendre compte des effets des interfaces imparfaites sur les propriétés effectives repose sur une condition d’équivalence énergétique qui ramène un matériau hétérogène avec interfaces imparfaites à un matériau hétérogène avec interfaces parfaites / In mechanics of materials and structures, the interface between two material components or two structural elements is traditionally and the most often assumed to be perfect. In mechanics, a perfect interface is a surface through which the displacement and stress vectors are continuous. The assumption of the perfect interfaces is inappropriate in many situations in mechanics. Indeed, the interface between two bodies or two parts of a body is a place propitious to complex physicochemical reactions and vulnerable to mechanical damage. The interest in imperfect interfaces has become for a few years growing with the development of nanometric materials and structures in which the interfaces and surfaces play a preponderant role. Starting from the basic configuration where an interphase of thin thickness separates two phases, this work establishes three general models of imperfect interface which make it possible to replace the interphase by an imperfect interface in the cases of thermal conduction, linear elasticity and piezoelectricity without disturbing the fields in questions to within a fixed error. The derivation of these models is based on the development of Taylor and an original coordinate-free approach of differential geometry. The three general models make it possible not only to get a better understanding of certain phenomenological models of imperfect interface but also to describe the effects of interface which the existing models are not able to take into account. The established models of imperfect interface are applied to determining the thermal, elastic and piezoelectric effective properties of composite materials consisting of a matrix reinforced by particles or fibers coated with an interphase. The method used to account for the effects of imperfect interfaces on the effective properties rests on an energy equivalency which brings back a heterogeneous material with imperfect interfaces to a heterogeneous material with perfect interfaces

L'objectif des travaux exposés dans cette thèse est d'identifier les différentes propriétés des constituants du sandwich cousu in-situ. Cette identification est indispensable pour simuler le comportement de ce type de matériau composite à différentes sollicitations statiques ou dynamiques. Nous proposons dans cette thèse de faire Une identification dynamique faite sur un échantillon représentatif (une plaque) qui prend en compte l'hétérogénéité et complexité de la structure. Cette identification est basée sur la corrélation ent.re un essai vibratoire et un calcul par éléments finis. La corrélation se fait en minimisant une fonction coût qui porte sur le décalage entre fréquences propres expérimentales et numériques. Cette minimisation est précédée par une identification du couple (fréquence propre/mode propre) numérique et expérimental en utilisant le MAC (Modal Assurance Criterion). Pour optimiser, nous passons, dans un premier temps; par une analyse de sensibilité qui permet de classifier les paramètres en fonction de• leur importance et ainsi ne lancer le processus d'identification que sur un nombre réduit de paramètres. Nous avons appliqué cette approche sur une poutre sandwich cousue et une plaque sandwich cousue. Dans une deuxième partie de ce travail de thèse, nous avons pu mettre au profil l'aspect périodique de ces structures composites sandwichs cousues, en utilisant le théorème de Floquet­-Bloch, et cela sur deux plans : l'aspect numérique pour la réduction du modèle et du temps de calcul et sur le plan physique par l'étude des bandes d'arrêt ('stopband') qui ont un intérêt applicatif assez intéressant. / The sandwich structures are well known for their high bending stiffness. This type of structure is also capable of including acoustic and thermal functionalities. However, they also have weaknesses such as the connection between the faceplate and the core and the weakness in the transverse direction due to the property of the core. The core is usually made of soft materials like foam for acoustic functionality. To overcome these weaknesses, it is possible to connect the different layers of the sandwich by transverse stitches. This is the concept of ‘stitched sandwich’. The stitch will deeply change the behavior of the structure and complicate the determination of its properties. The objective of this thesis is to identify the properties of the constituents of the stitched sandwich in situ. These properties are essential to simulate the behavior of this type of composite material under static or dynamic excitation. The identification of the properties of the constituents by mechanical tests is difficult for various reasons: the heterogeneity makes it complex to extract representative specimen; the behaviors of the constituents may change in non-in-situ tests; several different types of mechanical test, such as tensile-compression and torsion, are necessary to determine all the engineering constants in the case of orthotropic material which is common for composite materials. To overcome all these difficulties, we propose in this thesis a dynamic identification method conducted on the structure (the whole plate for example). Compared to mechanical test which is based on a sample, this method takes into account the heterogeneity and complexity of the structure. This method is based on the correlation between the vibration test and a finite element model of stitched sandwich. The parameters are identified by minimizing a cost function which can measure the gap between the experimental frequencies and the calculated frequencies. The correspondence of experimental mode and calculated mode is guaranteed by MAC (Modal Assurance Criterion). Before the optimization, we propose firstly a sensitivity analysis to classify the parameters according to their importance. Then the identification process is only conducted on a reduced number of parameters. We have applied this dynamic identification method to both a stitched sandwich beam and a stitched sandwich plate. 9 parameters of different constituents are identified in the case of plate. In the second part of this thesis, based on the theorem of Floquet-Bloch, we have profited from the periodic characteristic of the stitched sandwich structures in two aspects: in the numerical aspect, the periodicity has served to reduce the calculation of forced response of periodic structure; in the physical aspect, we have studied the stop band of stitched structures.

Thesis submitted in compliance with the requirements for the Master's Degree in Technology: Department of Mechanical Engineering, Durban University of Technology, 2008. / The development of an evolutionary optimisation method and its application to the design of an advanced composite structure is discussed in this study. Composite materials are increasingly being used in various fields, and so optimisation of such structures would be advantageous. From among the various methods available, one particular method, known as Evolutionary Structural Optimisation (ESO), is shown here. ESO is an empirical method, based on the concept of removing and adding material from a structure, in order to create an optimum shape. The objective of the research is to create an ESO method, utilising MSC.Patran/Nastran, to optimise composite structures. The creation of the ESO algorithm is shown, and the results of the development of the ESO algorithm are presented. A tailfin of an aircraft was used as an application example. The aim was to reduce weight and create an optimised design for manufacture. The criterion for the analyses undertaken was stress based. Two models of the tailfin are used to demonstrate the effectiveness of the developed ESO algorithm. The results of this research are presented in the study. / M

M.Tech. / In this study, ethylene vinyl acetate-fly ash (EVA-FA) composites were explored for the removal of phenols from water. The composites were prepared from EVA and untreated and acid treated fly ash via the melt-mixing technique using a rheomixer. The fly ash was characterised by X-ray fluorescence (XRF), X-ray diffraction (XRD) scanning electron microscopy (SEM) and Brunauer, Emmett and Teller (BET) surface area measurement. Fly ash is composed mainly of SiO2, Al2O3, CaO and Fe2O3. Modified fly ash gave a better specific surface area of 0.4180 m2/g, while 0.0710 m2/g was obtained for unmodified fly-ash due to the disintegration of the outer layer which resulted in smaller particles, hence a larger surface area. EVA-FA composites were prepared from fly ash loadings of 3 to 20% and further characterised by XRD, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and SEM. XRD showed successful incorporation of fly ash into the EVA matrix through the appearance of fly ash diffraction peaks on the EVA-FA composite diffraction pattern. The incorporation of fly ash into the EVA matrix resulted in an improvement in the thermal stability of EVA, but did not have an effect on the melting temperature of the composites. However, a decrease in crystallisation temperature was observed. SEM micrographs revealed uniform dispersion of fly ash particles in the polymer matrix. Adsorption studies were performed using p-chlorophenol (PCP), 2,4,6-trichlorophenol (TCP) and p-nitrophenol (PNP) as model pollutants. An increase in adsorption efficiency of EVA-FA composites was observed as fly ash loading was increased from 3 to 10%. Between 10 and 20% fly-ash loading the removal efficiencies remained constant. The effect of contact time, pH and initial concentration was investigated. Polymer composites prepared from unmodified fly ash resulted in a higher adsorption capacity of phenols. The maximum uptake of PCP was 0.18 mg/g and that for TCP was 0.19 mg/g over a pH range of pH 3 to 5 and after contact time of 8 h. However, the adsorption capacity of 0.30 mg/g for PNP was achieved at pH 5 after a period of 10 h. Equilibrium adsorption data were evaluated using Langmuir and Freundlich adsorption isotherm models. There was no significant difference in the correlation coefficients (R2) from both models for the adsorption of PCP and TCP. However, the equilibrium adsorption data for PNP were better described by the Langmuir adsorption isotherm model. The kinetics data were analysed by pseudo-first-order and pseudo-second-order kinetic models. The pseudo-second-order kinetics model gave better correlation coefficients (> 0.9) for the adsorption of the phenols and the amount adsorbed at equilibrium was comparable to that calculated from the pseudo-second-order equation. Desorption studies were performed using NaOH solution with varying concentrations (0.1 to 0.3 M) and the studies revealed that PNP was the most difficult to be desorbed. Approximately 75% of PNP was recovered while 82% of PCP and 84% of TCP were recovered.

[pt] Este trabalho tem como finalidade a apresentação de um método novo e eficiente para a análise e separação de tensões em materiais compostos (conjugados). O método híbrido consiste no acoplamento da lei ótica para materiais ortotrópicos com as equações de compatibilidade e equilíbrio para corpos anisotrópicos. As soluções destas equações são representadas por funções analíticas de variáveis complexas. O método propõe que se aproximem as funções analíticas por funções polinomiais. Estas funções aproximadas são determinadas através do acoplamento das equações de equilíbrio e compatibilidade com dados experimentais, obtidos da resposta fotoelástica, e com métodos numéricos (Newton-Raphson e mínimos quadrados), possibilitando a determinação dos coeficientes integrantes das funções polinomiais. O método apresenta como principal vantagem a capacidade de separar as tensões, com precisão, em pequenas ou mesmo em grandes regiões de modelos fotoelásticos planos, sem requerer a leitura de franjas isoclínicas. São apresentados excelentes resultados obtidos com a aplicação do método desenvolvido em alguns casos específicos, envolvendo um material composto por uma matriz de resina reforçada por fibras de vidro com arranjo unidirecional. Três casos são objetos de estudo: A) Barra retangular submetida à tração, com a direção do reforço paralela a direção da carga aplicada. B) Barra retangular submetida à tração. com direção do reforço fazendo um ângulo qualquer com a direção da carga aplicada. C) Plano semi-infinito submetido à carga concentrada atuando perpendicularmente à direção do reforço. / [en] The objective of this paper is to present a new and efficient method to analyse and separate stresses in composite materials. The hybrid method associates the stress-optic law for orthotropic materials with the compatibility and equlibrium equations for anisotropic bodies. The solutions of these equatios are represented by analytical functions of complex variables. The method proposes that these analytical functions be approximate by polynomial functions. These aapproximate functions are determined by the association of the compatibility equilibrium equatios with experimental data (obtained from the photoelastic response) and numerical methods (Newton-Raphson and least squares method). The method presents as a major advantage the capacity to separate stresses precisely in small or even in large regions of photoelastic plane models, without needign to collect isoclinic fringe data. The thesis presents excellent results obtained by the application of the developed method in some specific cases, where a fiber glass reinforced epoxy resin is used as a model material, will be shown. Three cases are studied: A) Rectangular bar in tension with the fiber reinforcement axis parallel to the applied load direction B) Rectangular bar in tension with the fiber reinforcement axis making a known angle with the applied load direction C) Semi-infinite plane subjected to a concentrated edge load which is perpendicular to the fiber reinforcement axis.