Rapporten innefattar en jämförande studie mellan olika typer av membran och beläggningar.Främst sker en jämförelse mellan materialens förmåga att andas. Vattentäthet testas på nyamaterial och efter olika sorters nötning så som martindale, flexing och tvätt för att få en ökadförståelse för materialen. Verktyget som används i studien för att mätaånggenomsläppligheten är hudmodellen. Resultatet presenteras med ett Ret-värde vilket är enförkortning på Evaporative resistance of a textile. Metoden används för att på ett bra sättsimulera hur huden svettas.Projektet har utförts på Swerea IVF som är ett forskningsinstitut beläget i Mölndal.Hudmodellen är en av de senaste stora investeringarna på Swereas textil och plast avdelning.Resultatet av studien visar att laminat andas bättre än beläggningar, dock har bärarmaterialetstor inverkan på resultaten. Ett tydligt samband mellan grövre material och sämre andning harobserverats. Många av de material som testats i studien uppvisar god förmåga att andas, därbåde flera av de mikroporösa och hydrofila materialen uppvisar Ret-värden under 13, vilketinnebär mycket god andning. En delstudie har varit att testa hur materialens andande förmågaförändras vid lägre relativ fuktighet. Resultatet blev att mikroporösa material inte påverkaslika mycket som de hydrofila materialen som då får en sämre andning.Efter de resultat studien har visat kan slutsatsen dras att tunna laminat är att föredra då högånggenomsläpplighet är ett krav. Behövs däremot ett högt motstånd mot nötning kan etttjockare material med fördel användas, vilket dock kan leda till högre ångmotstånd.This report is a comparative study between different types of membranes and coatings, thebreathability of the fabrics being the main focus of research. The fabrics' waterproofness wastested on new materials and by abrasion including martindale, flexing and washing. The toolthat has been used to measure water-vapour resistance is the skin model. The result ispresented by a Ret-value, which is short for evaporative resistance of a textile. The method isused to simulate the sweating body in a realistic way. Swerea IVF is the research institutelocated in Mölndal where the project has been carried out. The skin model is one of the latestbig investments at Swereas textile and plastic department.The results of the study shows that laminates breath better than coatings. It is important topoint out, however, that the carrier has great influence on the fabric in question. In addition,the results indicate a relation between thick fabrics and less breathability. Many of thematerials that have been tested show good permeability to breath, including bothmicropourous and hydrophilic materials. Most of them demonstrate a Ret-value less than 13,which means very good breathability. Further tests also show how the breathability changeswith lower relative humidity, indicating that microporous materials are less affected thanhydrophilic materials, thus having a higher resistance to water vapour.The conclusion of the study is that thin laminates is to prefer when high breathability isrequired. If the demand is high resistance to abrasion, a thicker material is prefered, whichalso yields a higher resistance to water permability. / Program: Textilingenjörsutbildningen

Fiber reinforced composite materials are widely used in aerospace, mechanical, civil and other industries because of their high strength-to-weight and stiffness-to-weight ratios. However, composite structures are highly prone to impact damage. Possible types of defect or damage in composite include matrix cracking, fiber breakage, and delamination between plies. In addition, delamination in a laminated composite is usually invisible. It is very diffcult to detect it while the component is in service and this will eventually lead to catastrophic failure of the structure. Such damages may be caused by dropped tools and ground handling equipments. Damage in a composite structure normally starts as a tiny speckle and gradually grows with the increase in load to some degree. However, when such damage reaches a threshold level, serious accident can occur. Hence, it is important to have up-to-date information on the integrity of the structure to ensure the safety and reliability of composite components, which require frequent inspections to identify and quantify damage that might have occurred even during manufacturing, transportation or storage. How to identify a damage using the obtained information from a damaged composite structure is one of the most pivotal research objectives. Various forms of structural damage cause variations in structural mechanical characteristics, and this property is extensively employed for damage detection. Existing traditional non-destructive inspection techniques utilize a variety of methods such as acoustic emission, C-scan, thermography, shearography and Moir interferometry etc. Each of these techniques is limited in accuracy and applicability. Most of these methods require access to the structure.They also require a significant amount of equipment and expertise to perform inspection. The inspections are typically based on a schedule rather than based on the condition of the structure. Furthermore, the cost associated with these traditional non-destructive techniques can be rather prohibitive. Therefore, there is a need to develop a cost-effective, in-service, diagnostic system for monitoring structural integrity in composite structures. Structural health monitoring techniques based on dynamic response is being used for several years. Changes in lower natural frequencies and mode shapes with their special derivatives or stiffness/ exibility calculation from the measured displacement mode shapes are the most common parameters used in identification of damage. But the sensitivity of these parameters for incipient damage is not satisfactory. On the other hand, for in service structural health monitoring, direct use of structural response histories are more suitable. However, they are very few works reported in the literature on these aspects, especially for composite structures, where higher order modes are the ones that get normally excited due to the presence of flaws. Due to the absence of suitable direct procedure, damage identification from response histories needs inverse mapping; like artificial neural network. But, the main diffculty in such mapping using whole response histories is its high dimensionality. Different general purpose dimension reduction procedures; like principle component analysis or indepen- dent component analysis are available in the literature. As these dimensionally reduced spaces may loose the output uniqueness, which is an essential requirement for neural network mapping, suitable algorithms for extraction of damage signature from these re- sponse histories are not available. Alternatively, fusion of trained networks for different partitioning of the damage space or different number of dimension reduction technique, can overcome this issue efficiently. In addition, coordination of different networks trained with different partitioning for training and testing samples, training algorithms, initial conditions, learning and momentum rates, architectures and sequence of training etc., are some of the factors that improves the mapping efficiency of the networks. The applications of smart materials have drawn much attention in aerospace, civil, mechanical and even bioengineering. The emerging field of smart composite structures offers the promise of truly integrated health and usage monitoring, where a structure can sense and adapt to their environment, loading conditions and operational requirements, and materials can self-repair when damaged. The concept of structural health monitoring using smart materials relies on a network of sensors and actuators integrated with the structure. This area shows great promise as it will be possible to monitor the structural condition of a structure, throughout its service lifetime. Integrating intelligence into the structures using such networks is an interesting field of research in recent years. Some materials that are being used for this purpose include piezoelectric, magnetostrictive and fiber-optic sensors. Structural health monitoring using, piezoelectric or fiber-optic sensors are available in the literature. However, very few works have been reported in the literature on the use of magnetostrictive materials, especially for composite structures. Non contact sensing and actuation with high coupling factor, along with other prop- erties such as large bandwidth and less voltage requirement, make magnetostrictive materials increasingly popular as potential candidates for sensors and actuators in structural health monitoring. Constitutive relationships of magnetostrictive material are represented through two equations, one for actuation and other for sensing, both of which are coupled through magneto-mechanical coefficient. In existing finite element formulation, both the equations are decoupled assuming magnetic field as proportional to the applied current. This assumption neglects the stiffness contribution coming from the coupling between mechanical and magnetic domains, which can cause the response to deviate from the time response. In addition, due to different fabrication and curing difficulties, the actual properties of this material such as magneto-mechanical coupling coefficient or elastic modulus, may differ from results measured at laboratory conditions. Hence, identification of the material properties of these embedded sensor and actuator are essential at their in-situ condition. Although, finite element method still remains most versatile, accurate and generally applicable technique for numerical analysis, the method is computationally expensive for wave propagation analysis of large structures. This is because for accurate prediction, the finite element size should be of the order of the wavelength, which is very small due to high frequency loading. Even in health monitoring studies, when the flaw sizes are very small (of the order of few hundred microns), only higher order modes will get affected. This essentially leads to wave propagation problem. The requirement of cost-effective computation of wave propagation brings us to the necessity of spectral finite element method, which is suitable for the study of wave propagation problems. By virtue of its domain transfer formulation, it bypasses the large system size of finite element method. Further, inverse problem such as force identification problem can be performed most conveniently and efficiently, compared to any other existing methods. In addition, spectral element approach helps us to perform force identification directly from the response histories measured in the sensor. The spectral finite element is used widely for both elementary and higher order one or two dimensional waveguides. Higher order waveguides, normally gives a behavior, where a damping mode (evanescent) will start propagating beyond a certain frequency called the cut-off frequency. Hence, when the loading frequencies are much beyond their corresponding cut-off frequencies, higher order mo des start propagating along the structure and should be considered in the analysis of wave propagations. Based on these considerations, three main goals are identified to be pursued in this thesis. The first is to develop the constitutive relationship for magnetostrictive sensor and actuator suitable for structural analysis. The second is the development of different numerical tools for the modelling the damages. The third is the application of these developed elements towards solving inverse problems such as, material property identification, impact force identification, detection and identification of delamination in composite structure. The thesis consists of four parts spread over six chapters. In the first part, linear, nonlinear, coupled and uncoupled constitutive relationships of magnetostrictive materials are studied and the elastic modulus and magnetostrictive constant are evaluated from the experimental results reported in the literature. In uncoupled model, magnetic field for actuator is considered as coil constant times coil current. The coupled model is studied without assuming any explicit direct relationship with magnetic field. In linear coupled model, the elastic modulus, the permeability and magnetostrictive coupling are assumed as constant. In nonlinear-coupled model, the nonlinearity is decoupled and solved separately for the magnetic domain and mechanical domain using two nonlinear curves,’ namely the stress vs. strain curve and magnetic flux density vs. magnetic field curve. This is done by two different methods. In the first, the magnetic flux density is computed iteratively, while in the second, artificial neural network is used, where a trained network gives the necessary strain and magnetic flux density for a given magnetic field and stress level. In the second part, different finite element formulations for composite structures with embedded magnetostrictive patches, which can act both as sensors and actuators, is studied. Both mechanical and magnetic degrees of freedoms are considered in the formulation. One, two and three-dimensional finite element formulations for both coupled and uncoupled analysis is developed. These developed elements are then used to identify the errors in the overall response of the structure due to uncoupled assumption of the magnetostrictive patches and shown that this error is comparable with the sensitivity of the response due to different damage scenarios. These studies clearly bring out the requirement of coupled analysis for structural health monitoring when magnetostrictive sensor and actuator are used. For the specific cases of beam elements, super convergent finite element formulation for composite beam with embedded magnetostrictive patches is introduced for their specific advantages in having superior convergence and in addition, these elements are free from shear locking. A refined 2-node beam element is derived based on classical and first order shear deformation theory for axial-flexural-shear coupled deformation in asymmetrically stacked laminated composite beams with magnetostrictive patches. The element has an exact shape function matrix, which is derived by exactly solving the static part of the governing equations of motion, where a general ply stacking is considered. This makes the element super convergent for static analysis. The formulated consistent mass matrix, however, is approximate. Since the stiffness is exactly represented, the formulated element predicts natural frequency to greater level of accuracy with smaller discretization compared to other conventional finite elements. Finally, these elements are used for material property identification in conjunction with artificial neural network. In the third part, frequency domain analysis is performed using spectrally formulated beam elements. The formulated elements consider deformation due to both shear and lateral contraction, and numerical experiments are performed to highlight the higher order effects, especially at high frequencies. Spectral element is developed for modelling wave propagation in composite laminate in the presence of magnetostrictive patches. The element, by virtue of its frequency domain formulation, can analyze very large domain with nominal cost of computation and is suitable for studying wave propagation through composite materials. Further more, identification of impact force is performed form the magnetostrictive sensor response histories using these spectral elements. In the last part, different numerical examples for structural health monitoring are directed towards studying the responses due to the presence of the delamination in the structure; and the identification of the delamination from these responses using artificial neural network. Neural network is applied to get structural damage status from the finite element response using its mapping feature, which requires output uniqueness. To overcome the loss of output uniqueness due to the dimension reduction, damage space is divided into different overlapped zones and then different networks are trained for these zones. Committee machine is used to co ordinate among these networks. Next, a five-stage hierarchy of networks is used to consider partitioning of damage space, where different dimension reduction algorithms and different partitioning between training and testing samples are used for better mapping fro the identification procedure. The results of delamination detection for composite laminate show that the method developed in this thesis can be applied to structural damage detection and health monitoring for various industrial structures. This thesis collectively addresses all aspects pertaining to the solution of inverse problem and specially the health monitoring of composite structures using magnetostric tive sensor and actuator. In addition, the thesis discusses the necessity of higher order theory in the high frequency analysis of wavw propagation. The thesis ends with brief summary of the tasks accomplished, significant contribution made to the literature and the future applications where the proposed methods addressed in this thesis can be applied.

Aluminium matrix composites are among the most promising candidate materials for light weight and high strength applications such as transportation and armour. In a previous study 6061 aluminum matrix composites reinforced with plain weave carbon fiber preform (AS4 Hexcel) were successfully fabricated by squeeze casting using the laminate fabrication technique. This research aims at optimizing the fabrication process in order to achieve improved strength and mechanical properties. It focuses on the liquid infiltration squeeze casting method. Good mechanical bonding between fiber and aluminium is achieved thanks to improved infiltration and impregnation of the fabric by liquid aluminium. Oxidation products at fiber/aluminium interface and porosity are reduced. As a result, composites are produced with overall improved mechanical properties. The flexural strength is increased by up to 19.9% and 15.4% compared to the laminate approach and the reference 6061 aluminium alloy squeeze cast under identical conditions, respectively. Similarly, overall hardness is improved. However, the impact strength is reduced by 7.76% and 25.78% when compared to casts fabricated by the laminate method and the reference aluminium alloy, respectively. The thesis constitutes a good basis for further research on fiber and particle reinforced aluminium matrix composites with the goal of further improving fracture toughness, particularly for gradient materials used in armour applications.

Afin de pouvoir détecter un défaut dans un composite, plusieurs méthodes de contrôle non destructif ont été développées. Le but de ce travail est de localiser un délaminage dans un stratifié carbone / époxyde en utilisant deux méthodes : la thermosonique et la thermographie. La première méthode consiste en une excitation par ultrasons et une détection par caméra IR. Pour la seconde technique, le matériau est irradié par une onde thermique et la détection est aussi réalisée par une caméra IR. Afin de comparer les résultats obtenus, des tests par immersion ultrasons C-scan ont été réalisés sur les échantillons. Cette méthode permet d'obtenir une cartographie du délaminage présent dans le stratifié. Un algorithme de comparaison entre la détection du délaminage faite par les ultrasons C-scan et les deux méthodes a permis de révéler les différences de forme du défaut détecté. Différents traitements d'images ont été appliqués aux images IR obtenues : des analyses temporelles et des analyses spatiales/temporelles. L'étude de l'évolution instantanée ainsi que l'évolution globale de la température se sont révélées prometteuses pour la thermosonique. L'image la plus décorrélée obtenus par l'analyse en composante principales donne un résultat tout aussi satisfaisant pour cette méthode. Pour la méthode sans contact, la thermographie, l'étude de la phase a permis de révéler la forme du délaminage avec la même précision que la thermosonique.Une comparaison de ces deux méthodes a été réalisée afin de mettre en évidence leurs avantages et leurs inconvénients. / To detect a defect in a composite, several methods of non destructive testing have been developped. The aim of this work is to find a delamination in polymer matrix laminates thanks to two methods : thermosonics and thermography. The first method consists of an ultrasonic excitation and a detection by an IR camera. For the second technique, the plate is irradiated with a thermal wave and the detection is also performed by an IR camera. To compare the results, ultrasonic immersion tests were performed on the samples. This method provides a map of the delamination in the laminate. An algorithm for comparing the detection of delamination made by the ultrasonic C-scan and both methods revealed differences in the shape of the detected defect. Several image processing have been applied to the IR images recorded : temporal analysis and spatial / temporal analysis. The study of the instant evolution and the global evolution of the temperature are promissing for thermosonics. The most uncorrelated image obtained by principal component analysis gives is satisfactory for this method. For thermography, the non contact method, the phase study revealed the shape of delamination with the same precision as thermosonics.A comparison between the two methods was realised to highlight their advantages and their drawbacks.

Idag är de flesta kemiska industrier försedda med system för nivåreglering. Dessa system syftar till att kontrollera vätskenivån i en behållare, trots störningar i form av smuts och skum. För denna process finns olika modeller av nivågivare på marknaden, men de flesta är antingen dyra eller kräver mycket rengöring och underhåll. Denna studie syftar till att undersöka om det är möjligt att mäta vätskenivån i en behållare som kan produceras till låg kostnad, och har en tillräcklig precision för att kunna användas som ett larm för att skydda doppvärmaren mot överhettning. Därför har ett konceptprov av kapacitiva nivågivare utförts där två varianter av kapacitiva nivågivare, etsad och tråd, har konstruerats och verifierats. Etsade varianter innefattar ett kopparlaminat med konfiguration av två fingerelektroder som rullats i ett PVDF-rör. Trådvarianten består av en partvinnad teflontråd som dragits på ett PVDF-rör. I både varianter varieras kapacitans med vattennivån beroende av avståndet mellan fingerelektroder i den etsade varianten och avståndet mellan teflontrådar i trådvarianten. Kapacitansen har beräknats för avståndet mellan fingerelektroder och mellan teflontrådar i form av en urladdningstid korrelerad med vattennivån. För denna process används en generatorkrets för fyrkantsvåg som byggts på en PCB. Resultatet av nivåmätning med båda varianter blev inte det önskade, men nivåmätningsfelet ligger inom ett acceptabelt intervall. Intervallet ligger mellan [+0,80,-0,52] för den etsade varianten och mellan [+1,02,-1,10] för trådvarianten. Det visar att den etsade varianten ger ett mindre nivåmätningsfel än trådvarianten. Nivåmätningsfelet kan minimeras genom att välja en lämpligare krets. / Today, most chemical industries have systems for level control. These systems aim to control the fluid level in a tank, despite dirt and foam disturbances. For this process there are different models of level sensors on the market, but most are either expensive or require a lot of cleaning and maintenance. This study aims to investigate whether it is possible to measure the level of fluid in a tank which can be produced at low cost and has sufficient precision to be used as an alarm to protect the immersion heaters from overheating. Therefore, a conceptual level of capacitive level sensors has been performed in which two variants of capacitive level sensors, etch and wire have been designed and verified. Etched variants include a copper-laminate with two finger electrode configurations rolled in a PVDF tube. The wire variant consists of a twisted Teflon wire drawn on a PVDF pipe. In both variations, capacitance with the water level varies depending on the distance between finger electrodes in the etched variant and the distance between the Teflon wires in the wire variant. The capacitance has been calculated for the distance between finger electrodes and between Teflon threads in the form of a discharge time correlated with the water level. For this process, a square wave generator circuit is built on a PCB. The result of level measurement with both variants did not get the desired, but the level measurement error is within an acceptable range. The interval is between [+ 0.80, -0.52] for the etched variant and between [+ 1.02, -1.10] for the wire variant. It shows that the etched variant gives a smaller level measurement error than the wire variant. The level measurement error can be minimized by selecting a more appropriate circuit.

Sabe-se que materiais compostos laminados são, hoje em dia, geralmente usados nas indústrias aeronáutica, aeroespacial, naval e outras, principalmente por causa de suas atrativas propriedades se comparadas aos materiais isotrópicos, como alta rigidez/peso, alta resistência, alto amortecimento e boas propriedades relacionadas ao isolamento térmico e acústico, entre outras. Porém, o comportamento de estruturas feitas de materiais compostos pode ser aperfeiçoado através da utilização de materiais inteligentes. Dentre os diferentes tipos comercialmente disponíveis de materiais inteligentes, os materiais piezelétricos são amplamente usados como sensores e atuadores para o monitoramento e controle de estruturas. O efeito piezelétrico direto define que uma deformação mecânica aplicada ao material é convertida em uma carga elétrica. Por outro lado, o efeito piezelétrico inverso define que um potencial elétrico aplicado ao material é convertido em deformação mecânica. Estes efeitos governam a interação eletromecânica nos materiais piezelétricos. O Método dos Elementos Finitos, uma ferramenta amplamente reconhecida e poderosa para a análise de estruturas complexas, é capaz de realizar a integração dos componentes inteligentes e das partes estruturais clássicas. Sendo assim, o comportamento estático e dinâmico, linear e geometricamente não-linear, de estruturas compostas laminadas delgadas com lâminas piezelétricas incorporadas é analisado neste trabalho usando o Método dos Elementos Finitos (MEF). Elementos triangulares, chamados GPL-T9, com três nós e seis graus de liberdade por nó (três componentes de deslocamento e três de rotação) e um grau de liberdade por camada piezelétrica (potencial elétrico) são usados. Para a análise estática não-linear as equações de equilíbrio são solucionadas usando o Método do Controle de Deslocamentos Generalizados (MCDG) enquanto a solução dinâmica é obtida usando o Método de Newmark com Formulação Lagrangeana Atualizada (FLA). O sistema de equações é resolvido usando o Método dos Gradientes Conjugados (MGC) e nos casos não-lineares um esquema iterativo-incremental é empregado. Diversos exemplos numéricos são apresentados e comparados com resultados obtidos por outros autores com diferentes tipos de elementos e diferentes formulações. A concordância entre estes resultados demonstra a validade e a eficácia dos modelos desenvolvidos. / It is well known that laminate composite materials are nowadays commonly used in the aeronautical, aerospace, naval and other industries mainly because their attractive properties as compared to isotropic materials, such as higher stiffness/weight, higher strength, higher damping and good properties related to thermal or acoustic isolation, among others. However, the behavior of structures made of composite materials can be improved using smart materials. Among several kinds of commercially available smart materials, the piezoelectric materials are widely used as sensors and actuators for the monitoring and control of structures. The direct piezoelectric effect states that a mechanical strain applied to the material is converted to an electric charge. On the other hand, the converse piezoelectric effect states that an electric potential applied to the material is converted to mechanical strain. These effects govern the electromechanical interaction in piezoelectric materials. The finite element method, a widely accepted and powerful tool for analyzing complex structures, is capable of dealing with the integration of smart components and classic structural parts. So, linear and geometrically nonlinear static and dynamic behavior of thin laminate composite structures embedded with piezoelectric layers are analyzed in this work using the Finite Element Method (FEM). Triangular elements, called GPL-T9, with three nodes and six degrees of freedom per node (three displacement and three rotation components) and one degree of freedom per piezoelectric layer (electrical potential) are used. For static analysis the nonlinear equilibrium equations are solved using the Generalized Displacement Control Method (GDCM) while the dynamic solution is performed using the classical Newmark Method with an Updated Lagrangean Formulation (ULF). The system of equations is solved using the Gradient Cojugate Method (GCM) and in nonlinear cases an iterative-incremental scheme is employed. Several numerical examples are presented and compared with results obtained by other authors with different kind of elements and different schemes. The agreement among these results demonstrates the validity and effectiveness of the developed models.

The vision driving the work reported herein is to investigate the fluid-structure interac-tion (FSI) effects of the flexible laminated blades for tilt-body micro-air-vehicles (MAV)proprotors in hover and forward flight configurations. This is in order to exploit the po-tential of flexible-bladed proprotor over the rigid-bladed proprotor in the enhancementof proprotor performance during hovering and cruising at a target forward speed. Forthat, the FSI model taking into account the specific problems devoted to MAV-sizedproprotor made of laminate composite was developed. The FSI model combines aerody-namic model adapting Blade Element Momentum (BEM) theory and structural modeladapting Anisotropic Finite Element Beam (AFEM) theory. The aerodynamic model isdeveloped to be capable of adapting in the analysis on low Reynolds number proprotors.In the structural model, the blade is modeled as an elastic beam undergoing deflectionsin flap, lag, and torsion to capture the coupling effects in anisotropic materials, adaptsthe structural analysis on proprotor blades made of laminate composite. The reliabilityof the developed FSI model is verified through a validation on both aerodynamic andstructural models, separately, on several MAV-sized proprotors. As for a direction to theanalysis on passively-adaptive proprotor blades, an optimal design on actively-adaptiveproprotor was carried out. For this, a program for designing the optimum rigid blades atsingle-point (for either isolated cruise-point or isolated hover-point) and multiple-point(combined cruise and hover point) for proprotors have been developed. The proceduresin the optimal design program employs the numerical iterative inverse design method,based upon the minimum thrust induced losses (MIL). Even if the work in this thesiswas directed primarily towards the proprotor, however, the propulsion system from themotor part was not neglected since the propulsion efficiency is a crucial factor to the suc-cess of MAVs. A cheap and time-effective method of proposing the best motor from theselected commercial motors was developed, based on Taguchi’s method. The sensitivityof the total power consumption to the variation of value of each motor design variableswas also studied. The benefit of the use of tip body in the blade and the effect of bendingon the induced twist and on the thrust degradation, respectively, were also analyzed andidentified. Finally, the systematically designed passively-adaptive composite proprotors were evaluated under steady operating conditions. Hovering and cruise propulsive performance, characterized by total power Ptotal, were compared between the rigid-bladed and flexible-bladed proprotors. As a result of the comparison, the flexible-bladed proprotor with fixed system is found to be capable of slightly enhancing the performance through the reduction in Ptotal over its optimal rigid-bladed proprotor. / L’idée principale du travail rapporté ici est d’étudier les effets de l’intéraction fluide-structure (FSI) de pales laminées flexibles pour les proprotors de micro véhicules aériens(MAV) de type tilt-body dans les configurations de vol stationnaire et en avant. Eneffet, le but est d’exploiter les possibilités offertes par les proprotors à pales flexiblespar rapport aux proprotors à pales rigides pour améliorer leur performance dans cesphases de vol. Le modèle FSI a été développé à cet effet. Ce modèle tient compte desproblèmes spécifiques liés aux proprotors de MAV faits de composite laminé. Il com-bine l’adaptation de modèle aérodynamique par la théorie d’élement de pale (BEM) etl’adaptation de modèle structurel par la théorie des éléments finis de poutre anisotropes(AFEM). Le modèle aérodynamique est développé pour être capable de s’adapter àl’analyse des proprotors à bas nombres de Reynolds. Dans le modèle structural, la paleest modélisée comme une poutre élastique subissant des déviations dans la flexion, latraction et la torsion afin de capturer les effets de couplage de matériaux anisotropes.Il adapte l’analyse structurale des pales du proprotor faites de composite laminé. Lafiabilité du modèle FSI développé est vérifiée à travers une validation par modèles aéro-dynamique et structural, séparément, sur plusieurs proprotors de MAV. Afin de se dirigervers une analyse de pales de proprotors à adaptation passive , une recherche de designoptimal a été effectuée pour des proprotor à adaptation active. Pour cela, un programmepour la conception de pales rigides optimales à un unique point de fonctionnement (soitle vol de croisière soit le vol stationnaire) et à plusieurs points (combinant croisière etvol stationnaire) ont été développés. Les procédures du programme de design optimalemploient les mèthodes de design inverse par itération numérique, sur la base de pertesde poussée induites minimales (MIL). Même si le travail dans cette thèse a été dirigéprincipalement vers le proprotor, la partie moteur du système de propulsion n’a pasété négligée puisque l’efficacité de la propulsion est un facteur crucial pour le succès desMAVs. Une méthode simple et rapide de sélection du meilleur moteur parmi les moteurscommerciaux choisis est élaborée sur la base de la méthode de Taguchi. La sensibilitéde la consommation d’énergie totale à la variation de la valeur de chaque variable deconception du moteur a été étudiée. Le bénéfice de l’utilisation de la charge à la pointe de la pale et l’effet de la flexion sur la torsion induite et sur la dégradation de la poussée respectivement ont aussi été analysés et identifiés. Enfin, les proprotors à pales flexibles conçues systématiquement ont été évalués dans des conditions de fonctionnement stables. Performances en vol stationnaire et performances croisière propulsive, caractérisées par la puissance totale Ptotal ont été comparées entre les proprotors à pales rigides et à pales flexibles. En tant que résultat de la comparaison, les proprotors à pales flexibles s’avère capable d’améliorer légèrement les performances par la réduction de la Ptotal surson optimal proprotors à pales rigides.

Sabe-se que materiais compostos laminados são, hoje em dia, geralmente usados nas indústrias aeronáutica, aeroespacial, naval e outras, principalmente por causa de suas atrativas propriedades se comparadas aos materiais isotrópicos, como alta rigidez/peso, alta resistência, alto amortecimento e boas propriedades relacionadas ao isolamento térmico e acústico, entre outras. Porém, o comportamento de estruturas feitas de materiais compostos pode ser aperfeiçoado através da utilização de materiais inteligentes. Dentre os diferentes tipos comercialmente disponíveis de materiais inteligentes, os materiais piezelétricos são amplamente usados como sensores e atuadores para o monitoramento e controle de estruturas. O efeito piezelétrico direto define que uma deformação mecânica aplicada ao material é convertida em uma carga elétrica. Por outro lado, o efeito piezelétrico inverso define que um potencial elétrico aplicado ao material é convertido em deformação mecânica. Estes efeitos governam a interação eletromecânica nos materiais piezelétricos. O Método dos Elementos Finitos, uma ferramenta amplamente reconhecida e poderosa para a análise de estruturas complexas, é capaz de realizar a integração dos componentes inteligentes e das partes estruturais clássicas. Sendo assim, o comportamento estático e dinâmico, linear e geometricamente não-linear, de estruturas compostas laminadas delgadas com lâminas piezelétricas incorporadas é analisado neste trabalho usando o Método dos Elementos Finitos (MEF). Elementos triangulares, chamados GPL-T9, com três nós e seis graus de liberdade por nó (três componentes de deslocamento e três de rotação) e um grau de liberdade por camada piezelétrica (potencial elétrico) são usados. Para a análise estática não-linear as equações de equilíbrio são solucionadas usando o Método do Controle de Deslocamentos Generalizados (MCDG) enquanto a solução dinâmica é obtida usando o Método de Newmark com Formulação Lagrangeana Atualizada (FLA). O sistema de equações é resolvido usando o Método dos Gradientes Conjugados (MGC) e nos casos não-lineares um esquema iterativo-incremental é empregado. Diversos exemplos numéricos são apresentados e comparados com resultados obtidos por outros autores com diferentes tipos de elementos e diferentes formulações. A concordância entre estes resultados demonstra a validade e a eficácia dos modelos desenvolvidos. / It is well known that laminate composite materials are nowadays commonly used in the aeronautical, aerospace, naval and other industries mainly because their attractive properties as compared to isotropic materials, such as higher stiffness/weight, higher strength, higher damping and good properties related to thermal or acoustic isolation, among others. However, the behavior of structures made of composite materials can be improved using smart materials. Among several kinds of commercially available smart materials, the piezoelectric materials are widely used as sensors and actuators for the monitoring and control of structures. The direct piezoelectric effect states that a mechanical strain applied to the material is converted to an electric charge. On the other hand, the converse piezoelectric effect states that an electric potential applied to the material is converted to mechanical strain. These effects govern the electromechanical interaction in piezoelectric materials. The finite element method, a widely accepted and powerful tool for analyzing complex structures, is capable of dealing with the integration of smart components and classic structural parts. So, linear and geometrically nonlinear static and dynamic behavior of thin laminate composite structures embedded with piezoelectric layers are analyzed in this work using the Finite Element Method (FEM). Triangular elements, called GPL-T9, with three nodes and six degrees of freedom per node (three displacement and three rotation components) and one degree of freedom per piezoelectric layer (electrical potential) are used. For static analysis the nonlinear equilibrium equations are solved using the Generalized Displacement Control Method (GDCM) while the dynamic solution is performed using the classical Newmark Method with an Updated Lagrangean Formulation (ULF). The system of equations is solved using the Gradient Cojugate Method (GCM) and in nonlinear cases an iterative-incremental scheme is employed. Several numerical examples are presented and compared with results obtained by other authors with different kind of elements and different schemes. The agreement among these results demonstrates the validity and effectiveness of the developed models.

Submitted by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T17:05:25Z No. of bitstreams: 1 ALVES_Jose_2017.pdf: 5435239 bytes, checksum: 2763493f52fe9331545e1498f4c97f81 (MD5) / Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T17:08:12Z (GMT) No. of bitstreams: 1 ALVES_Jose_2017.pdf: 5435239 bytes, checksum: 2763493f52fe9331545e1498f4c97f81 (MD5) / Approved for entry into archive by Milena Rubi ( ri.bso@ufscar.br) on 2017-10-17T17:10:15Z (GMT) No. of bitstreams: 1 ALVES_Jose_2017.pdf: 5435239 bytes, checksum: 2763493f52fe9331545e1498f4c97f81 (MD5) / Made available in DSpace on 2017-10-17T17:11:44Z (GMT). No. of bitstreams: 1 ALVES_Jose_2017.pdf: 5435239 bytes, checksum: 2763493f52fe9331545e1498f4c97f81 (MD5) Previous issue date: 2017-05-29 / Não recebi financiamento / At last years due to increasing use of composite materials of synthetic fibers with thermosetting matrix, several alterative have been sought trying to minimize the impacts generated by both the dispose of this material at the end of their useful life and by its heavy dependency of non-renewable resources as petroleum based products for the production of raw materials. As alternative to introduce composites materials that have least environmentally impact natural fibers have drawn attention of researchers. In this work the aim is to manufacture by vacuum infusion process, composite laminates hybrid adding woven jute fiber in structural weaving fiberglass with epoxy resin matrix. The quality of laminate was analyzed by fiber weight fraction determining and thermal analysis by DSC (Differential Scanning Calorimetry) and DMTA (Dynamic Mechanical Thermal Analysis). It was possible to manufacture hybrids laminates by vacuum infusion with fiber fraction in about 60%. Hybrids laminates presented had a reduction of density of 20% with relation to the glass reinforced plastic. Regarding to mechanical properties, the laminates were characterized by tensile, compression and ILSS testing. With respect to hybrid laminates, the better results of tensile properties such as strength and young's modulus was achieved by the laminates with fiber oriented in 0/90° (H0/90) with maximum strength value near to 200 MPa, while for orientation ±45° (H45 e H45/0/90) the strength results were 68 MPa and 84 MPa, respectively. In this case can be highlighted the hybrid laminate H45, whose tensile strength (83,9 MPa) has not present significant changes with the introduction of jute fiber (with increase of 60% its thickness) compared with glass reinforced plastic (84,5 MPa) for the same fiber orientation. For compressive strength the best result was presented by the laminates H0/90 (fibers in 0/90°) as well, with values close to 150 MPa while the laminates to ±45° (H45 e H45/0/90) presented values of 90 MPa. Regarding to ILSS the variation of strength was smaller, 25 MPa to direction 0/90° and 23 MPa and 21 MPa to H45 and H45//0/90 laminates, respectively. Therefore, mechanical properties were significantly influenced by plies orientation in the laminates and by the hybridization with jute fibers. / Nos últimos anos, devido ao crescente consumo de compósitos de fibras sintéticas com matriz termorrígida, várias alternativas têm sido buscadas a fim de minimizar os impactos gerados tanto pelo descarte desse material ao fim de sua vida útil, quanto pela grande dependência de derivados de recursos não renováveis, como o petróleo para a produção das matérias-primas. Como uma das alternativas de introduzir na área de compósitos, materiais que tenham menores impactos ambientais, as fibras naturais têm recebido atenção de pesquisadores. Assim, neste trabalho foram moldados pelo processo de infusão à vácuo, compósitos de laminados híbridos através da utilização de tecidos de fibras de juta e tecidos estruturais de fibras de vidro com matriz de resina epóxi. A qualidade dos laminados foi analisada por meio da determinação da fração mássica de fibra e por análise térmica de DSC (Differential Scanning Calorimetry) e DMTA (Dynamic Mechanical Thermal Analysis. Foi possível moldar laminados híbridos pelo processo de infusão com fração de fibra em cerca de 60%. Os laminados híbridos apresentaram uma redução na densidade de 20% em relação aos compósitos contendo somente fibras de vidro. Em relação às propriedades mecânicas, os compósitos laminados foram caracterizados através dos ensaios de tração, compressão e cisalhamento interlaminar (ILSS). Entre os laminados híbridos, os melhores resultados de propriedades de tração, como resistência e módulo de elasticidade foram alcançados pelos laminados com ambas as fibras orientadas a 0/90° (H0/90), com valor de tensão máxima próximo a 200 MPa, enquanto que para as orientações ±45° (H45 e H45/0/90) os valores foram próximos de 68 e 84 MPa, respectivamente. No caso, pode ser destacado o laminado híbrido H45, cuja resistência a tração (83,9 MPa) não apresentou mudanças significativas com a introdução das fibras de juta (com acréscimo de 60% na espessura) quando comparado ao laminado de fibras de vidro (84,5 MPa) com mesma orientação. A melhor resistência à compressão também foi apresentada pelos laminados orientados a 0/90° (H0/90) com valores próximos a 150 MPa, enquanto os laminados a ±45° (H45 e H45/0/90) apresentaram os valores de 90 MPa. Em relação à resistência ao cisalhamento interlaminar, entre os laminados híbridos, a variação entre as orientações foi menor, 25 MPa para a direção 0/90° e, 23MPa e 21MPa para os laminados H45 e H45//0/90, respectivamente. Assim, as propriedades mecânicas foram influenciadas significativamente pela orientação das v camadas nos laminados e pela introdução das fibras de juta. Desta forma, conclui-se que a significativa redução de algumas propriedades possivelmente invalida a utilização das configurações híbridas estudadas para aplicações estruturais nas pás eólicas. No entanto, as configurações de laminados híbridos, desenvolvidas e analisadas neste trabalho podem ser aplicadas para moldar componentes em compósitos para peças não estruturais ou com menores requisitos de resistência, como para o segmento automotivo, e ainda com possibilidades de melhorias.

Foi realizado um estudo comparativo da capacidade de duas variantes do método de radiografia por raios- X em detectar trincas de fadiga em juntas sobrepostas rebitadas de laminado híbrido metal-fibra Glare® de uso aeronáutico. Durante os ensaios mecânicos de fadiga sob amplitude constante de tensão, diversos corpos de prova rebitados foram periodicamente inspecionados por raios-X, em ambas as modalidades convencional e digital. Raios-X em filmes convencionais digital. Raios-X em filmes convencionais proporcionaram ótimo detalhamento de trincas nas juntas mecânicas, enquanto que as imagens geradas pela modalidade digital apresentaram qualidade muito inferior, prejudicando ou até mesmo impedindo a avaliação do grau de integridade estrutural das juntas rebitadas. / A comparison is performed on the ability of two modalities of nondestructive X-ray radiography method in detecting fatigue cracks in riveted lap joints of aeronautical grade fiber-metal laminate Glare™. During constant amplitude loading in fatigue testing riveted specimens were periodically inspected using both the conventional and digital X-ray methodology. Conventional film X-ray modality provided high quality images of growing cracks in the mechanical joints, whereas digital radiography generated faulty images, which impaired or even prevented the structural integrity assessment of the riveted joints.