Tato diplomová práce se zaměřuje na stanovení geometrických a materiálových parametrů konstrukce slotu letadla B737-200. V této práci je vypracovaný návrh kompozitového slotu s ohledem na dané zatěžovací případy, včetně tzv. “bird strike”. Analytické výpočty jsou ověřené metodou konečných prvků (MKP) v programech MSC.Nastran/Patran, MSC.Dytran

Indiana University-Purdue University Indianapolis (IUPUI) / The design optimization of laminated composite structures is of relevance in automobile, naval, aerospace, construction and energy industry. While several optimization methods have been applied in the design of laminated composites, the majority of those methods are only applicable to linear or simplified nonlinear models that are unable to capture multi-body contact. Furthermore, approaches that consider composite failure still remain scarce. This work presents an optimization approach based on design and analysis of computer experiments (DACE) in which smart sampling and continuous metamodel enhancement drive the design process towards a global optimum. Kriging metamodel is used in the optimization algorithm. This metamodel enables the definition of an expected improvement function that is maximized at each iteration in order to locate new designs to update the metamodel and find optimal designs. This work uses explicit finite element analysis to study the crash behavior of composite parts that is available in the commercial code LS-DYNA. The optimization algorithm is implemented in MATLAB. Single and multi-objective optimization problems are solved in this work. The design variables considered in the optimization include the orientation of the plies as well as the size of zones that control the collapse of the composite parts. For the ease of manufacturing, the fiber orientation is defined as a discrete variable. Objective functions such as penetration, maximum displacement and maximum acceleration are defined in the optimization problems. Constraints are included in the optimization problem to guarantee the feasibility of the solutions provided by the optimization algorithm. The results of this study show that despite the brittle behavior of composite parts, they can be optimized to resist and absorb impact. In the case of single objective problems, the algorithm is able to find the global solution. When working with multi-objective problems, an enhanced Pareto is provided by the algorithm.

The thesis was focused on preparation of bioceramic composite materials containing Ca-phosphates and zirconia fibers using electrophoretic deposition. A series of experiments were aimed at determining the appropriate composition of the suspensions. High-energy milling was used for preparing deposits with good physical and mechanical properties using EPD. The influence of milling time, the amount of monochloroacetic acid in isopropanol slurry indifferent electrolyte LiCl and ZrO2 were evaluated on the course deposition and the resulting properties of the deposits. Influence of sintering temperature, the milling time and the fiber content of ZrO2 on the chemical and structural composition was determined by X-ray analysis, measurement of density and structural analysis using a scanning electron microscope. Mechanical and bioactive properties of sintered deposits were determined depending on the milling time and content of ZrO2 fibers.

The market is in great need of more environmentally friendly alternatives to fossil-based composite materials to obtain a more sustainable future. Lignin is the second most common biopolymer and is a byproduct in the pulping and paper industry. Fractionation of lignin has made it possible to receive lignin with narrow dispersity and low molecular weight, which is suitable for further applications. Modification of lignin structure yields new reactive sites that can be tailored for specific needs. Because of the aromatic structure of lignin, it is a promising renewable resource for production of thermosets. In this project Kraft lignin is sequentially solvent-fractionated and modified in an allylation process with allyl chloride. The allylated lignin is reacted with a cross-linking agent and used to impregnate carbon fibre mats. The resin-coated material is then cured at 125 oC to achieve a composite material. The project also encompasses characterization of the chemical structure of lignin in the different fractions. The morphology and adhesive properties of the lignin as well as the carbon fibres and the composite material was investigated. Although the production of composite material from lignin and carbon fibres were accomplished, bubble formation in the resin was a problem for all composite samples that were prepared, whether it was during solvent evaporation or during curing. By performing the addition of resin to carbon fibre mats in multiple steps, where pressure is added after the first applied layer, it is suggested that complete adhesion to the carbon fibre can be achieved, whilst maintaining adequate resin to carbon fibre ratio. / Marknaden är i stort behov av mer miljövänliga alternativ till fossilbaserade kompositmaterial för att kunna erhålla en mer hållbar framtid. Lignin är den näst vanligaste aromatiska biopolymeren och framställs som en biprodukt i pappersindustrin. Fraktionering av lignin har gjort det möjligt att erhålla lignin med låg dispersitet och molekylvikt vilket är lämpligt för vidare applikationer. Modifiering av lignins struktur ger upphov till nya reaktiva grupper som kan anpassas för ens behov. Den aromatiska strukturen som lignin besitter resulterar i en lovande förnybar resurs för produktion av härdplast. I detta projekt är Kraft lignin sekventiellt fraktionerat med lösningsmedel och modifierat med hjälp av en allyleringsprocess i närvaro av allylklorid. Det allylerade ligninet reagerar med en tvärbindare och används vidare för att impregnera kolfiber. De impregnerade kolfibermattorna härdades i ugn vid 125 oC för att erhålla kompositmaterial. Projektet omfattar även karaktärisering av den kemiska strukturen i lignin från de olika fraktionerna. Morfologin och vidhäftningsförmåga av lignin, kolfiber och likaså kompositmaterialet undersöktes. Ett kompositmaterial bestående av kolfiber och lignin erhölls med framgång under projektets gång, dock var bubbelbildning ett stort problem under förångningen av lösningsmedel och även under härdningsprocessen. Addition av harts till kolfibermattorna i flera steg, där tryck är adderat efter det första lagret har blivit applicerat, anses vara en lovande metod för att en hög vidhäftningsgrad ska kunna erhållas. Detta medan ett adekvat förhållande mellan harts och kolfiber upprätthålls.

<p>  </p> <p>Thermal shrinkage in advanced composite manufacturing causes residual stress in a cylindrical anisotropic segment. The residual stress later induces a spring-in angle when  the temperature change is negative. The superposition method in the finite element method (FEM) by ABAQUS©  proves that only the residual stress in the circumferential direction controls the spring-in angle and induces the radial residual stress. To predict the angle change, the residual stress is firstly determined by using the closed-loop geometry in FEM and then implemented into the cylindrical cross-ply symmetric laminate segment. Consequently, the geometry creates the spring-in angle under the traction-free surface. The angle change is in good agreement with the Radford equation and is found to depend on the coefficient of thermal expansion (CTE) in the circumferential and radial directions rather than other material properties and geometry dimensions. </p> <p>The study found a new limitation of the Radford equation, in that it is accurate when the part is anisotropic symmetric laminate, but not when it is unsymmetric. The accuracy of the Radford equation is further explored with the double curve geometry. Using the superposition method, the circumferential residual stress along the major curve is found to have an influence on the angle change not only of the major curve, but also of the minor curve. The negative temperature change produces the spring-in angle on the major curve, and both spring-in and -off angles on the minor curve, which rely on the radius ratio. In addition, the spring-in angle on the major curve is coincident with the Radford equation. In sum, knowing the spring-in angle is very helpful in designing a tool in advanced composite manufacturing, and the superposition method and the Radford equation are applicable to predict the spring-in angle.</p>

No description available.

A finite element based model for interrogation of the elastic and progressive failure response of textile based composite materials has been developed and implemented. The geometrically thorough textile geometry model is used as the basis for creation of the geometry used for the finite element analysis. A detailed assessment is made for the linear elastic response of a plain weave textile composite subjected to various boundary conditions and loadings. Hashin's failure criterion and a maximum stress criterion are employed to predict the failure of the yam and matrix material, respectively. A material degradation scheme is implemented to account for the decrease in the elastic constants of the material. The initiation and progression of failure within a plain weave textile composite has been predicted. / Ph. D.

Les ouvrages du génie civil ont une durée de vie limitée, et plusieurs d’entre eux nécessitent aujourd’hui une réparation, voire une reconstruction partielle. Ainsi le domaine des réparations et des renforcements en béton connaît depuis une dizaine d’années, une croissance importante dans le secteur du bâtiment et des travaux publics. Plusieurs études ont montré que le retrait et le fluage peuvent mener à de sévères problèmes liés à la durabilité. En effet, ces phénomènes peuvent être à l’origine de la fissuration, et même plus rarement de la ruine de l’ouvrage. Cette thèse a pour objectif d’étudier le comportement au retrait et au fluage d’éléments renforcés. Ce travail est divisé en deux parties principales. Dans la première partie, nous effectuons une étude expérimentale sur des éléments renforcés. Nous nous intéressons, dans la deuxième partie,à la modélisation du séchage afin de prévoir les transferts hydriques au sein du matériau, et le retrait de celui-ci. L’étude expérimentale vise à étudier l’effet du renforcement sur le comportement différé d’éprouvettes en mortier normalisé. L’approche théorique et numérique permet d’analyser les transferts hydriques et la diffusion de l’humidité au sein du matériau, et de calculer ainsi les déformations différées. Les essais expérimentaux montrent que le renforcement avec des matériaux composites réduit considérablement la déformation au fluage, mais n’apporte pas d’amélioration quant au retrait de séchage. / The works of civil engineering have one limited life span, and several of them require a repair today, even a partial rebuilding. Thus the field of the concrete repairs and strengthening knowssince ten years, a considerable growth in the sector of the building and public works. Several studies showed that the shrinkage and creep can lead to severe problems involved indurability. Indeed, these phenomena can be at the origin of cracking, and even more rarely of the ruin of the work. This thesis aims to study the shrinkage and creep behaviour of strengthened elements. This work is divided into two principal parts. In the first part, we carry out an experimental study on strengthened elements. We are interested, in the second part, to the modelling of drying in orderto envisage the hydrous transfers within material, and the shrinkage of this one. In the experimental study, we are interested to the strengthening effect on the differed behaviour of mortar specimens. The theoretical and numerical approach allows to analyze the hydrous transfers and the diffusion of humidity within material, and thus to calculate the differed deformations. The experimental tests show that the strengthening with composite materials reduced considerably the creep strain, but does not make improvement as for the shrinkage ofdrying.

Les structures de type gridshell élastique permettent de réaliser des enveloppes courbes par la déformation réversible d’une grille structurelle régulière initialement plane. Cette capacité à “former la forme” de façon efficiente prend tout son sens dans le contexte actuel où, d’une part la forme s’impose comme une composante prédominante de l’architecture moderne, et d’autre partl’enveloppe s’affirme comme le lieu névralgique de la performance des bâtiments. Fruit des recherches de l’architecte et ingénieur allemand Frei Otto dans les années 1960, elles ont été rendues populaires par la construction de la Multihalle de Mannheim en 1975. Cependant, en dépit de leur potentiel, très peu de projets de ce type ont vu le jour suite à cette réalisation emblématique qui en a pourtant démontré la faisabilité à grande échelle. Et pour cause, les moyens engagés à l’époque ne sauraient assurer la reproductibilité de cette expérience dans un contexte plus classique de projet, notamment sur le plan économique. Par ailleurs, les techniques et les méthodes développées alors sont pour la plus part tombées en désuétude ou reposent sur des disciplines scientifiques qui ont considérablement évoluées. Des matériaux nouveaux, composites, ont vu le jour. Ils repoussent les limitations intrinsèques des matériaux usuels tel que le bois et offrent des performances techniques bien plus intéressantes pour ce type d’application. Enfin, notons que le cadre réglementaire a lui aussi profondément muté, apportant une certaine rigidité vis-à-vis de la pénétration des innovations. Ainsi la conception des gridshells se pose-t-elle en des termes nouveaux aux architectes et ingénieurs actuels et se heurte à l’inadéquation des outils et méthodes existant. Dans cette thèse, qui marque une étape importante dans une aventure de recherche personnelle initiée en 2010, nous tentons d’embrasser la question de la conception des gridshells élastiques dans toute sa complexité, en abordant aussi bien les aspects théoriques que techniques et constructifs. Dans une première partie, nous livrons une revue approfondie de cette thématique et nous présentons de façon détaillée l’une de nos principales réalisation, la cathédrale éphémère de Créteil, construite en 2013 et toujours en service. Dans une seconde partie, nous développons un élément de poutre discret original avec un nombre minimal de degrés de liberté adapté à la modélisation de la flexion et de la torsion dans les gridshells constitués de poutres de section anisotrope. Enrichi d’un noeud fantôme, il permet de modéliser plus finement les phénomènes physiques au niveau des connexions et des appuis. Son implémentation numérique est présentée et validée sur quelques cas tests. Bien que cet élément ait été développé spécifiquement pour l’étude des gridshells élastiques, il pourra avantageusement être utilisé dans tout type de problème où la nécessité d’un calcul interactif avec des tiges élastiques prenant en compte les couplages flexion-torsion s’avère nécessaire / An elastic gridshell is a freeform structure, generally doubly curved, but formed out through the reversible deformation of a regular an initially flat structural grid. Building curved shapes that way seems to offer the best of both worlds : shell structures are amongst the most performant mechanically speaking while planar and orthogonal constructions are much more efficient and economic to produce than curved ones. This ability to “form a form” efficiently is of peculiar importance in the current context where morphology is a predominant component of modern architecture, and envelopes appear to be the neuralgic point for building performances. The concept was invented by Frei Otto, a German architect and structural engineer who devoted many years of research to gridshells. In 1975 he designed the Multihalle of Mannheim, a 7500 m2 wooden shell which demonstrated the feasibility of this technology and made it famous to a wide audience. However, despite their potential, very few projects of this kind were built after this major realization. And for good reason, the ressources committed at that time cannot guarantee the replicability of this experiment for more standard projects, especially on the economic level. Moreover, the technics and methods developed by Otto’s team in the 1960s have mostly fall into disuse or are based on disciplines that have considerably evolved. New materials, such as composite materials, have recently emerged. They go beyond the limitations of conventional materials such as timber and offer at all levels much better technical performances for this kind of application. Finally, it should be noted that the regulatory framework has also deeply changed, bringing a certain rigidity to the penetration of innovations in the building industry. Therefore, the design of gridshells arises in new terms for current architects and engineers and comes up against the inadequacy of existing tools and methods. In this thesis, which marks an important step in a personal research adventure initiated in 2010, we try to embrace the issue of the design of elastic gridshells in all its complexity, addressing both theoretical, technical and constructive aspects. In a first part, we deliver a thorough review of this topic and we present in detail one of our main achievements, the ephemeral cathedral of Créteil, built in 2013 and still in service. In a second part, we develop an original discrete beam element with a minimal number of degrees of freedom adapted to the modeling of bending and torsion inside gridshell members with anisotropic cross-section. Enriched with a ghost node, it allows to model more accurately physical phenomena that occur at connections or at supports. Its numerical implementation is presented and validated through several test cases. Although this element has been developed specifically for the study of elastic gridshells, it can advantageously be used in any type of problem where the need for an interactive computation with elastic rods taking into account flexion-torsion couplings is required

O advento dos veículos aéreos não tripulados (VANTs) representa uma quebra de paradigma no ramo aeronáutico. São revisados os conceitos de projeto envolvidos no desenvolvimento de VANTs e levantadas as suas potenciais aplicações. São também analisadas as características de sua operação e discutidas as questões regulatórias envolvidas na certificação e integração dos VANTs ao tráfego aéreo civil. Dentre as várias características singulares dos VANTs, enfatiza-se a sua necessidade de realizar vôos a grande altitude e com longa autonomia. Isso leva ao emprego de materiais mais leves e configurações com asas de grande alongamento, que provocam menor arrasto induzido. É feita uma revisão sobre materiais compósitos, que são materiais de uso crescente no ramo aeronáutico por sua leveza e resistência, e que por sua característica de anisotropia, são suscetíveis à otimização estrutural. Métodos e ferramentas de otimização estrutural de compósitos laminados ainda são pouco empregados, por suas características discretas e pelo grande número de parâmetros envolvidos. Um método eficiente e adequado à otimização de um problema desse tipo é o método dos algoritmos genéticos (AG). Assim foi desenvolvida uma sub-rotina de otimização baseada em algoritmos genéticos, usando a linguagem de programação Fortran. A sub-rotina desenvolvida trabalha em conjunto com um programa comercial de análise estrutural baseado no método dos elementos finitos, o Ansys. Foi também proposta uma configuração de asa de um VANT típico, de grande alongamento e fabricada com materiais compósitos reforçados com fibras (CRF). A asa proposta teve o número e a orientação das camadas do laminado otimizadas com o uso da sub-rotina desenvolvida, e resultados satisfatórios foram encontrados. Foram também analisados os efeitos da variação dos parâmetros dos operadores do AG, como probabilidades de mutação, cruzamento, tipo de escalonamento, entre outros, no desempenho do mesmo. Também foram feitas otimizações no mesmo modelo de asa proposto, empregando outros métodos disponíveis no próprio programa de análise estrutural. Os resultados das otimizações através desses métodos foram comparados com os resultados obtidos com a sub-rotina desenvolvida / The advent of the unmanned air vehicles (UAVs) represents a paradigm break in the aeronautical field. The project concepts involved in the development of UAVs are revised and its potential applications are rose. Also the issues related to UAVs operation are assessed and the regulatory questions involved in their certification and integration to the civil air space are argued. Amongst many singular characteristics of the UAV, its necessity of performing flights at high altitudes and with long endurance is emphasized. This leads to the employment of lighter materials and to configurations with high aspect ratio wings that cause minor induced drag. A revision on composite materials, which are of increasing use in the aeronautical field for their lightness and strength, and that are appropriate for being optimized due to their anisotropy characteristics, is made. Methods and tools of structural optimization of laminated composites are still seldom employed, due to their discrete nature and to the large number of parameters involved. An efficient and suitable method for the optimization of this kind of problem is the genetic algorithm (GA). Thus, an optimization sub-routine based on genetic algorithms was developed, using FORTRAN programming language. The developed sub-routine works in combination with Ansys, a structural analysis commercial program based on the finite elements method. A configuration of a typical UAV wing, made from composite reinforced plastics (CRP) was also proposed. The proposed wing had the number of plies and the orientations of its layers optimized using the developed sub-routine, and satisfactory results had been found. Also the effect of the variation of AG’s operator parameters in its performance, as mutation probabilities, crossover probabilities, fitness scaling, among others, have been assessed. The same wing model considered was also optimized using other build-in methods of the structural analysis program. The results of these optimizations have been compared with the results obtained with the developed sub-routine