Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-04-08T12:32:34Z No. of bitstreams: 0 / Made available in DSpace on 2016-04-08T12:32:34Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2016-12-08T17:19:18Z (GMT). No. of bitstreams: 1 Daiara Floriano da Silva.pdf: 11387901 bytes, checksum: e3d70556e1953c972d75ee3c62835b4b (MD5) Previous issue date: 2012-06-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Research has demonstrated in recent decades, that calcium phosphate bioceramics and nanocomposite with calcium phosphate matrix may be the new generation of biomaterials to use in the repair of defects and reconstruction of bone tissue. This can be explained by new microstructural and nanostructural characteristics, interconnected microporosity, surface area of grains and differentiated micropores from conventional biomaterials. Among this class of ceramic biomaterials, we highlight the hydroxyapatite and calcium b-phosphate, by presenting crystallographic similarity with the bone tissue of the human skeleton. This work focused on optimizing the synthesis method to obtain a wet powder of calcium phosphate, the source calcium carbonate (CaCO3) extracted from calcareous fossilized shells and fossil phosphoric acid. Preparation of calcium phosphate biomaterials with microporosity and microstructure differentiated characteristics from conventional biomaterials. The powder recovered from the synthesis were calcined at a temperature of 900°C/2h, supplying the post nanostructured micro of calcium b-phosphate and hydroxyapatite. In cylindrical specimens with dimensions 10mm high 5mm in diameter, for different compositions were prepared. These were sintered at a temperature of 1200°C/2h providing biomaterials. The characterization studies were performed on the morphological, microstructural, nanostructural, mineralogical, physical, chemical, thermal behavior and mechanical properties levels. The results of this study have highlighted the different characteristics of microporosity, of the nanostructure and microstructure of calcium phosphate biomaterials, promising characteristics for cell adhesion and proliferation on the surface grain and micropores. These results indicate that the synthetic method from a natural source performed efficiently in the synthesis of calcium phosphate powders. / As pesquisas têm demonstrando nestas últimas décadas, que as biocerâmicas de fosfatos de cálcio e os nanocompósitos com matriz de fosfatos de cálcio, podem ser a nova geração de biomateriais para o uso na reparação de defeitos e na reconstrução de tecido ósseo. Isto pode ser explicado pelas novas características microestruturais, nanoestruturais, da microporosidade interconectada, da área superficial de grãos e de microporos diferenciadas dos biomateriais convencionais. Dentre esta classe de biomateriais cerâmicos, se destacam a hidroxiapatita, e o fosfato de cálcio-b, por apresentarem similaridade cristalográfica com os tecidos ósseos do esqueleto humano. O presente trabalho se concentrou na otimização do método de síntese via úmida para obtenção de pós de fosfato de cálcio, a partir do precursor carbonato de cálcio (CaCO3), proveniente de conchas calcárias fossilizadas e ácido fosfórico. Elaboração de biomateriais de fosfato de cálcio, com características de microporosidade e microestrutura diferenciadas dos biomateriais convencionais. Os pós recuperados da síntese, foram calcinados a temperatura de 900ºC/2h, fornecendo os pós micro nanoestruturados de fosfato de cálcio-b e hidroxiapatita. Foram elaborados corpos de prova cilíndricos nas dimensões 10mm de altura com 5mm de diâmetro, para as diferentes composições. Estes foram sinterizados a temperatura de 1200°C/2h, fornecendo os biomateriais. Os estudos de caracterização foram realizados em nível morfológico, microestrutural, nanoestrutural, mineralógico, físico, do comportamento térmico, químico, e das propriedades mecânicas. Os resultados obtidos neste estudo colocaram em evidência, as características diferenciadas de microporosidade, microestrutura e nanoestrutura dos biomateriais de fosfato de cálcio, características promissoras para adesão e proliferação celular na superfície de grãos e de microporos. Estes resultados indicam que o método de síntese a partir de um precursor natural se apresentou eficiente na síntese de pós de fosfato de cálcio.

A modelagem adequada da propagação de trincas por fadiga em fuselagens pressurizadas é complexa devido a uma série de fatores, tais como: o efeito geometricamente não-linear conhecido como bulging, o revestimento das fuselagens ser bastante delgado e a presença de reforçadores que alteram a distribuição de tensão na fuselagem. Uma metodologia para simular computacionalmente a propagação de trincas por fadiga em estruturas de casca pressurizadas baseada no método dos elementos finitos e em conceitos da Mecânica do Fraturamento Linear Elástica é apresentada. Como resultado dessa simulação, obtêm-se a trajetória de propagação da trinca e o número de ciclos para ocorrer a propagação. Um estudo paramétrico é realizado para avaliar a influência de diversos parâmetros, tais como: espessura do revestimento, nível de pressurização, comprimento de trinca, área da seção transversal e distância entre reforçadores, entre outros, no fator de bulging em estruturas de cascas pressurizadas com ou sem reforçadores. A metodologia apresentada é validada por meio da simulação de propagação de trinca em uma fuselagem de um Boeing 737, sendo que os resultados obtidos nessa simulação são comparados com resultados experimentais e com os obtidos por POTYONDY (1993). A influência do tamanho do incremento de trinca e do número de nós por elemento (4 ou 9 nós) nos resultados obtidos é investigada. / The modeling of fatigue crack growth in pressurized fuselages is very complex due to many factors, such as the nonlinear stiffening effect referred to as bulging, the fuselage skin being very thin and the presence of stiffeners which modifies the stress distribution on the fuselage. A methodology for the computational modeling of the fatigue crack growth in pressurized shell structures, based on the finite element method and concepts of Linear Elastic Fracture Mechanics, is presented. As a result of this numerical simulation, the crack trajectory and the fatigue propagation life are obtained. A parametric study is performed to investigate the influence of several parameters, such as skin thickness, pressurization level, crack length, structural area of the stiffeners, distance between stiffeners, on the bulging effect for unstiffened and stiffened pressurized shells. The methodology is validated by means of a fatigue crack propagation simulation in a Boeing 737 airplane fuselage. The results of this simulation are compared with experimental results and those obtained by POTYONDY (1993). Additionally, the influence of the crack increment and the number of nodes per element (8 or 9 nodes) on the simulation results are investigated.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Materiais compÃsitos vÃm sendo extensamente estudados, pois seu uso permite a obtenÃÃo de estruturas leves e resistentes, com bom isolamento tÃrmico e boa resistÃncia a fadiga. CompÃsitos laminados, foco do presente trabalho, sÃo compostos pelo empilhamento de um conjunto de lÃminas, cada uma composta de fibras unidirecionais imersas em uma matriz polimÃrica. Cascas laminadas sÃo utilizadas em muitas situaÃÃes prÃticas de interesse, como fuselagens de aeronaves, estruturas marÃtimas, dentre outras. Devido ao elevado nÃmero de variÃveis envolvidas no projeto de cascas laminadas, mÃtodos de otimizaÃÃo devem ser utilizados em seu projeto. Na anÃlise estrutural de tais cascas, devido ao seu complexo comportamento mecÃnico, mÃtodos numÃricos, como o MÃtodo dos Elementos Finitos (MEF), sÃo utilizados. De modo a determinar a capacidade Ãltima de carga em cascas laminadas, à necessÃrio considerar tanto a presenÃa de grandes deslocamentos (nÃo-linearidade geomÃtrica) quanto o comportamento nÃo- linear do material (nÃo-linearidade fÃsica). No presente trabalho, a nÃo-linearidade geomÃtrica foi introduzida utilizando a formulaÃÃo Lagrangiana Total aplicada a um elemento de casca abatida baseado na Teoria de Marguerre. O elemento foi implementado em um programa de cÃdigo-aberto e vÃrios exemplos com resposta analÃtica e numÃrica presentes na literatura foram tratados. Os resultados obtidos indicaram que o elemento à muito eficiente no tratamento de cascas com pequenas curvaturas iniciais sujeitas a deslocamentos moderadamente grandes. Jà a nÃo-linearidade fÃsica foi considerada por meio de modelos de falha progressiva, com a diminuiÃÃo instantÃnea das propriedades mecÃnicas das lÃminas que falham ao longo da anÃlise. TrÃs mÃtodos de falha progressiva distintos foram formulados e implementados em conjunto com a formulaÃÃo de anÃlise pelo MEF. Os resultados se mostraram promissores, com a correta obtenÃÃo das cargas de falha em laminados tanto submetidos a esforÃos axiais como de flexÃo, mostrando concordÃncia tanto com resultados numÃricos da literatura quanto com resultados experimentais. O desempenho mecÃnico da estrutura foi entÃo utilizado em um modelo de otimizaÃÃo com o objetivo de encontrar um esquema de laminaÃÃo Ãtimo. Neste trabalho, propÃe-se um Algoritmo GenÃtico com um esquema hÃbrido de computaÃÃo paralela para a otimizaÃÃo de laminados. Tal algoritmo utiliza uma configuraÃÃo em ilhas e pode ser executado tanto em clusters quanto em computadores pessoais. AlÃm disso, o algoritmo possui operadores especÃficos para a troca, adiÃÃo e eliminaÃÃo de camadas em laminados. As metodologias implementadas foram combinadas na otimizaÃÃo de placas e cascas laminadas tanto utilizando anÃlise linear quanto nÃo-linear. Nos exemplos lineares, o algoritmo foi verificado e os ganhos em eficiÃncia e tempo de execuÃÃo devidos à paralelizaÃÃo do algoritmo foram estudados. Mostrou-se que o algoritmo paralelo nÃo à somente mais rÃpido que o sequencial, mas tambÃm produz melhores resultados. Jà nos exemplos nÃo-lineares, foram obtidos projetos significativamente mais eficientes que aqueles obtidos utilizando anÃlise linear. / Composite materials are being extensively studied, as their use allows the design of structures that are lighter and stronger than their metal counterparts and feature good thermal insulation and fatigue resistance. Fiber Reinforced Composites (FRC), the focus of the present work, consist in stacking multiple laminae, each one consisting of unidirectional fibers embedded in a polymeric matrix. Laminated shells are used in many industrial applications, such as modern aircraft fuselages and wing systems, offshore structures, among others. Due to the many variables involved in the design of such structures, such as the number of layers (plies) and the mate- rial, thickness and fiber orientation of each layer, the traditional trial-and-error design procedure becomes arduous, which leads to the use of optimization techniques. In the structural analysis of laminated shells, numerical methods are commonly used, particularly the Finite Element Method (FEM), which is capable of modeling complex geometries, loads and boundary conditions. In order to determine the final load-carrying capacity of such shells, it is necessary to take into account not only the presence of large displacements (geometric non-linearity) but also its failure behavior (material non-linearity). In the present work, the geometric non-linearity was introduced by using the Total Lagrangian approach in a shallow shell finite element based on Marguerreâs Shell Theory. The element was implemented in an academic finite element software and multiple benchmark numerical examples were treated. The obtained results showed that the element is efficient when dealing with shells with small initial curvatures and moderately large displacements and rotations. The material non-linearity was considered by using progressive failure models, with the instantaneous degradation of the mechanical properties of layers that fail during the analysis. Three distinct progressive failure methods were formulated and implemented and the numerical examples yielded promissing results, with the correct determination of the ultimate failure load of laminates subjected to in-plane and bending loads, which were in good agreement with experimental and numerical results from the literature. The structural performance evaluated through the analysis procedure was then used in an optimization model in order to find the optimum stacking sequence for a given applied load. Here, a novel Genetic Algorithm with a hybrid computational parallelization scheme was proposed. The algorithm is based on the island model and can be executed in both clusters and personal computers alike. The algorithm was implemented and combined with the analysis procedures in the optimization of laminated shells considering both linear and non-linear analysis. In the linear examples, the algorithm was verified and the efficiency and execution time gains due to the parallel implementation were measured. The results show that the parallel algorithm not only runs faster than a sequential one, but also provides better results. In the non-linear examples, significant lighter and more efficient designs were obtained due to the consideration of the two types of non-linearities.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-04-08T12:32:34Z No. of bitstreams: 0 / Made available in DSpace on 2016-04-08T12:32:34Z (GMT). No. of bitstreams: 0 / A casca da castanha de caju (CCC), um resíduo agrícola da produção de castanha, proveniente da região nordeste do Brasil foi caracterizada e submetida ao processo de pirólise lenta. As propriedades do bio-carrvão, do bio-óleo e dos gases produzidos foram investigados e potenciais aplicações foram propostas. A CCC foi caracterizada pela seguintes técnicas: análise elementar CHNS, umidade total, conteúdo de cinzas, matérias voláteis, poder calorífico superior e por análise termogravimétrica. A análise termogravimétrica sob fluxo de nitrogênio mostrou que a decomposição é dominada pela degradação da hemicelulose e celulose na faixa de 250 a 350oC e pela decomposição da lignina na faixa de 400 a 500oC. Na presença de ar, o perfil de degradação é semelhante, porém observa-se uma maior degradação da lignina. A pirólise lenta da casca da castanha de caju foi realizada em um reator tipo batelada aquecido por chama ar-GLP sob diferentes fluxos (mL min-1) de nitrogênio ou ar. O sólido obtido (bio-carvão), líquido (fase aquosa + bio-óleo) e a fase gás foram quantificados e caracterizados por diferentes técnicas. Os experimentos realizados sob fluxo de nitrogênio apresentaram um rendimento de cerca de 30, 40 e 30% em massa paras as fases sólido, líquida e gás, respectivamente. Sob fluxo de ar ocorreu uma diminuição no rendimento da fase líquida, principalmente na produção de bio-óleo, e um aumento da fase gás. Os bio-carvões produzidos apresentaram elevados teores de carbono, na faixa de 70-75% em massa, poder calorífico na faixa de 25 a 28 MJ kg-1, características de carbono amorfo, sem morfologias definidas e ausência de poros. Os espectros FTIR de bio-óleos produzidos sob fluxo de nitrogênio apresentaram um aumento da intensidade relativa das bandas cerca de 1700 cm-1 (ν C=O) e 1230 cm-1 (ν C-O) em comparação com os produzidos sob fluxo de ar, o que sugere a presença de grandes quantidades de compostos oxigenados de carbono, como aldeídos, cetonas e ácidos carboxílicos. As análises das fases gás mostraram a predominância de CO2 e CO a temperaturas inferiores a 400ºC e a formação preferencial de H2 acima desta temperatura. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Yolk-shell nanostructures/yolk-shell nanoparticles are defined as a hybrid structure, a mixture of core/shell and hollow particles, where a core particle is encapsulated inside the hollow shell and may move freely inside the shell. Of the various classifications of yolk-shell nanostructures, a structure with an inorganic core and inorganic shell (inorganic/inorganic) has been studied widely due to their unique optical, magnetic, electrical, mechanical, and catalytic properties. In the work presented here, among the different inorganic/inorganic yolk-shell nanostructures noble metal@silica yolk-shell nanostructures has been chosen as the topic of interest. Silica shell possesses many advantages such as chemical inertness, tunable pore sizes, diverse surface morphologies, increasing suspension stability, no reduction in LSPR properties of noble metal nanoparticles when used as a coating for such particles. Noble metal nanoparticles such as AgNPs and AuNPs, on the other hand, possess unique structural, optical, catalytic, and quantum properties. Hence yolk-shell nanostructures with a combination of Ag or Au core and a silica shell (Ag@SiO2 and Au@SiO2) would open to endless possibilities. In this study, four areas were mainly explored: mechanism of silica shell formation over a given template, the synthetic modifications of Ag@SiO2 and Au@SiO2 yolk-shell nanostructures, their application as a potential catalyst, and devising of a flow type catalytic reactor. Despite the growing number of contributions on the topic of yolk-shell nanostructures, particularly Au@SiO2 and Ag@SiO2 yolk-shell nanostructures, a potential for improvement lies in all four aforementioned areas. As an initial study, the effect of different processing conditions as well as the mechanism of silica shell formation over reactive block copolymer templates was investigated. An asymmetric PS-b-P4VP block copolymer was chosen as a structure directing component to deposit silica shell. In order to deposit silica shell, PS-b-P4VP micelles with a collapsed PS core and a swollen P4VP corona was prepared via a solvent exchange method. The growth of silica shell over the PS-b-P4VP micelles (reactive template) was done using in-situ DLS and TEM. The experimental data obtained revealed the 4 distinct stages involved in the silica shell formation over the reactive BCP micellar template starting from the accumulation of silica precursor around the P4VP corona followed by a reactive template mediated hydrolysis-condensation reaction of the silica precursor which eventually lead to the shell densification and shell growth around the micelles. An understanding of the mechanism of silica shell formation over reactive templates provides a direct way to encapsulate various active species such as metal nanoparticles and quantum dots and paves the way for the template mediated synthesis of hybrid nanostructures such as yolk-shell nanoparticles. These studies also serve as a platform to fine-tune the properties of such hybrid nanostructures by varying the reaction parameters during silica shell deposition and reaction time. The next part of the work focused mainly on the synthesis, process optimisation and characterization of Ag@SiO2 and Au@SiO2 yolk-shell nanostructures, and their potential use as a nanocatalyst. A well-known soft template mediated synthesis of the yolk-shell nanostructure was adopted for the present work. For this PS-b-P4VP micelle was used as a dual template for both encapsulation of nanoparticle and the deposition of silica shell. The nanoparticles were entrapped selectively to the BCP micellar core and silica deposition was done by reacting the nanoparticle-loaded micelles with an acidic silica sol which lead to the formation of Ag@PS-b-P4VP@SiO2 or Au@PS-b-P4VP@SiO2 particles with respect to the nanoparticle used. In the case of Ag@PS-b-P4VP particles, upon silica deposition, a partial dissolution of AgNPs was observed whereas AuNPs were stable against dissolution. Hence yolk-shell nanostructures with AuNPs were studied further. As-prepared Au@PS-b-P4VP@SiO2 particles were then subjected to pyrolysis to remove the BCP template. The resulting yolk-shell nanostructures comprised of an AuNP core and a hollow mesoporous silica shell. Upon removal of the BCP template, the Au@SiO2 particles fused together and formed large aggregates. The catalytic properties of Au@SiO2 yolk-shell nanoparticles were explored using a model reaction of reduction of 4-nitrophenol and proved to have good catalytic activity and efficient recyclability. It was observed that catalytic efficiency was hindered by the particle aggregates formed after pyrolysis by creating an inhomogeneity in the system and inaccessibility of the catalytic surface for the reactants. Hence synthetic modifications were needed to overcome such drawbacks. Next part of the work deals with the synthetic modification of Au@SiO2 yolk-shell nanoparticles done by embedding them in a porous silica structure (PSS). Such structural morphology was attained by gelating the excess silica precursor while synthesising the Au@PS-b-P4VP@SiO2 particles. The pyrolytic removal of block copolymer results in the formation of Au@SiO2@PSS catalyst and the porous nature of both the shell and the silica structure provides an easy access for the reactants to the nanocatalyst surface located inside. The catalytic properties of Au@SiO2@PSS were studied using a model reaction of catalytic reduction of 4-nitrophenol (4-NP) and reductive degradation of different dyes. Kinetic studies show that Au@SiO2@PSS catalyst possesses enhanced catalytic activity as compared to other analogous systems reported in the literature so far. Furthermore, catalytic experiments on the reductive degradation of different dyes show that Au@SiO2@PSS catalyst can be considered as a very promising candidate for wastewater treatment. Another proposed direction of applying the Au@SiO2 yolk-shells is by devising a continuous flow catalytic system composed of Au@SiO2 yolk-shell nanoparticles for the effective degradation of azo dyes as a promising candidate for wastewater treatment. This was done by infiltrating the Au@PS-b-P4VP@SiO2 particles inside a porous glass substrate (frits) and the subsequent pyrolytic removal of the BCP template resulting in the formation of Au@SiO2 yolk-shell nanostructures sintered inside the frit pores. The flow catalytic reactor was exploited in terms of studying its catalytic activity in the degradation of azo dyes and 4-nitrophenol and proved to have a catalytic efficiency of ca. 99% in terms of reagent conversion and has a long-term stability under flow. Thus, with a few modifications, these flow type systems can open the doors to a very promising continuous flow catalytic reactor in the future.

Ces travaux de thèse sont basés principalement sur le phénomène de multistabilité des structures minces de type plaques et coques ainsi que quelques applications associées. Les travaux sont divisés en deux parties. La première partie a pour objet l’étude théorique, numérique et expérimentale de la multistabilité des coques minces orthotropes peu profondes à courbures uniformes. On montre notamment qu’une telle coque, lorsqu’elle est soumise à la combinaison d’une courbure initiale et d’une précontrainte suffisamment élevées, possède jusqu’à trois configurations stables vis-à-vis des propriétés matériaux. Dans un premier temps, nous proposons des critères de conception et fabrication de coques multistables allant jusqu’à la tristabilité, validés numériquement et expérimentalement. Ensuite, nous appliquons ces critères à la conception et à la fabrication de coques multistables cylindriques dont la différence de niveau énergétique entre les deux états stables est minime. Sur ce support, la deuxième partie est consacrée à des applications exploitant la bistabilité des coques cylindriques minces à faible différence énergétique. Nous effectuons tout d’abord une application au contrôle de forme via l’utilisation de matériaux actifs que l’on attache à la structure. Cela comprend une première phase théorique de conception de la structure et de la loi d’actionnement, et une seconde phase de mise en œuvre expérimentale. Ensuite, nous étudions théoriquement et expérimentalement les propriétés de dynamique non-linéaire de ce type de coques dans le but de mettre en évidence les modes d’oscillations intrinsèques à une source d’excitation externe. Enfin, nous proposons une application à la récupération d’énergie vibratoire non-linéaire de coques multistables cylindriques métalliques par voie piézoélectrique. / This work is essentially based on the phenomenon of multistability of thin structures as plates and shells and some associated applications. The work is divided in two parts. The first part aims to study theoretically, numerically and experimentally the multistability of thin orthotropic shallow shells with uniform curvature. We show notably that such a shell, when submitted to the combination of initial curvature and pre-stresses sufficiently high, possesses up to three stable states towards the choice of the material. First, we propose criteria to design and manufacture multistable shells up to tristability ; this work is validated by finit element simulations and experiments. After, we apply those criteria to the design and manufacture ofcylindrical multistable shells for which the energetic gap between stable states is minimal. The second part is dedicated to direct applications of bistability of thin cylindrical bistable shells with low energetic gap. We first propose an application on shape control via the use of active materials which we bond on the structure. This includes a first phase of theoretical design of both the structure and the actuation law, and a second phase of experimental demonstration. After, we study both theoretically and experimentally the non-linear dynamic properties of such structures with the aim to highlight the different modes of oscillations intrinsic to an external excitation source. Finally, we propose an application to non-linear broadband energy harvesting from vibrations based on multistable piezoelectric excited shells.

Distillation columns play a very important role in petrochemical industry. The requirements to their safety and lifetime are being constantly stepped up. Hence, they have to be designed very carefully and special attention is to be paid to strength analyses. The diploma thesis is focused on strength analysis of the distillation column carried out according to the ASME Code, Section VIII. Parts of the equipment and some nozzles were analyzed in operational and test conditions. One particular nozzle was analyzed more thoroughly by means of FEM, stress categories were considered. The work also includes worked out drawing documentation.

A recent trend in the development of renewable and biodegradable materials has led to the development of composites from renewal sources such as natural fibers. This agricultural activity generates a large amount of waste in the form of peanut shells. The motivation for this research is based on the utilization of peanut shells as a viable source for the manufacture of biocomposites. High-density polyethylene (HDPE) is a plastic largely used in the industry due to its durability, high strength to density ratio, and thermal stability. This research focuses in the mechanical and thermal properties of HDPE/peanut shell composites of different qualities and compositions. The samples obtained were subjected to dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and mechanical tensile strength tests. TO prepare the samples for analysis, the peanut shells were separated into different mesh sizes and then mixed with HDPE at different concentrations. The results showed that samples with fiber size number 10 exhibited superior strength modulus of 1.65 GPa versus results for HDPE alone at 1.32 GPa. The analysis from the previous experiments helped to determine that the fiber size number 10 at 5%wt. ratio in HDPE provides the most optimal mechanical and thermal results. From tensile tests the highest modulus of elasticity of 1.33 GPa was achieved from the samples of peanut shells size number 10 in HDPE at 20%wt. ratio, while the results for HDPE alone were only of 0.8 GPa. The results proved the hypothesis that the addition of peanut shells to HDPE enhances both the thermal and mechanical properties of the composite.

Au cours des processus de conception,l’optimisation de formes apporte aux industriels dessolutions pour l’amélioration des performances desproduits. En particulier, les structures minces quiconstituent environ 70% d’un véhicule, sont une préoccupationdans l’industrie automobile. La plupartdes méthodes d’optimisation pour ces structures surfaciquesprésentent certaines limites et nécessitent desexpertises à chaque niveau de la procédure d’optimisation.L’objectif de cette thèse est de proposer une nouvellestratégie d’optimisation de formes pour les coquesminces. L’approche présentée consiste à exploiter leséquations de coques du modèle de Koiter en se basantsur une analyse isogéométrique. Cette méthode permetde réaliser des simulations sur la géométrie exacteen définissant la forme à l’aide de patchs CAO. Lesvariables d’optimisation choisies sont alors les pointsde contrôle permettant de piloter leur forme. La définitiondes patchs permet également de dégager ungradient de forme pour l’optimisation à l’aide d’uneméthode adjointe.Cette méthode a été appliquée pour des critères mécaniquesissus des bureaux d’études Renault. Des résultatsd’optimisation pour un critère de compliance sontprésentés. La définition et l’implémentation de critèresvibro-acoustiques sont discutés à la fin de cette thèse.Les résultats obtenus témoignent de l’intérêt de la méthode.Toutefois, de nombreux développements serontnécessaires avant d’être en mesure de l’appliquer dansl’industrie. / During the design process, optimizationof shapes offers manufacturers solutions for improvingproducts performances. In particular, thin shellstructures that represent about 70 % of a vehicle, area concern in the automotive industry. Most optimizationmethods for surface structures have limitationsand require expertise at every level of the optimizationprocedure.The aim of this thesis is to propose a new strategyfor the shape optimization of thin shell structures.The approach presented rely on using the Koiter’sshell model based on an isogeometric analysis. Thismethod allows for simulations on the exact geometryby defining the shape using CAD patches. Selectedoptimization variables are the control points used tocontrol the shape of the CAD patches. Variations ofthese points allows to scan a wide design space withfew parameters. The definition of patchs also enablesto find a gradient with respect to the shape for theoptimization by using the adjoint state method.This method was applied to mechanical criteria fromthe Renault design offices. Optimization results for acompliance criterion are presented. The definition andimplementation of vibro-acoustic criteria are discussedat the end of this thesis. The results demonstratethe interest of the method. However, many developmentswill be needed before being able to apply it inthe industry.