Este trabalho propõe uma análise sistemática das demandas mecânicas instrumentais básicas do violão, visando, assim, uma aquisição consciente de determinadas movimentações. A base teórica foi composta por autores que abordam questões essencialmente práticas do fazer instrumental do violão, destacando-se Abel Carlevaro e Eduardo Fernandez; este último diferencia claramente os termos mecânica e técnica, aspecto fundamental neste trabalho. As movimentações de cada mão são divididas entre horizontais (no sentido das cordas) e verticais (entre as cordas) e entre os aspectos mecânicos relacionados à localização das mãos no instrumento (chamados por nós de parâmetros e suas expansões) e os relacionados às referências ou movimentações auxiliares na mudança entre duas localizações (chamados de recursos). A partir da ordenação proposta e das notações desenvolvidas, concebemos uma sistemática de estudo, visando à aquisição de tais movimentos, aplicada nos 25 Etudes Mélodiques et Progressives Op.60, de Matteo Carcassi. Foram realizadas propostas de caráter vocabular e elementos pouco ou não debatidos foram tratados, fornecendo material para discussões futuras dentro do amplo campo temático da mecânica instrumental. A organização sistemática dos elementos mecânicos proposta, aplicados na obra de Carcassi, procurou uma maior eficiência no processo de aprendizagem, buscando melhorias em relação à efetividade técnica e à maior consciência das demandas instrumentais. / This project proposes a systematic analysis of the basic mechanical demands of the guitar to assist a conscious development of certain gestures. The theoretical basis in this work is compound mainly by the ideas of authors that dealt with practical issues of the instrumental making of the guitar, such as Abel Carlevaro and Eduardo Fernandez; the last one clearly differentiates the terms mechanical and technical, fundamental aspects in this work. The gestures of each hand are divided between horizontal (in the direction of the strings) and vertical (between the strings) and between the mechanical aspects related to the location of the hands in the instrument (called by us of parameters and their expansions) and those related to the reference or auxiliary gestures in the change between two locations (called resources). From the proposed ordering and the developed notations, we designed a systematic study aimed at the developing of such gestures, applied in the 25 Etudes Mélodiques et Progressives Op.60, by Matteo Carcassi. The proposal of a vocabulary was made and often ignored elements were approached, providing content for future discussions within the wide topic of instrumental mechanics. The systematic organization of the mechanical elements proposed, applied in Carcassi\'s music, sought greater efficiency in the learning process, seeking improvements in relation to the technical effectiveness and awareness of the instrumental demands.

Many studies of the fire induced thermal and structural behaviour in large compartments, carried out over the past two decades, show a great deal of non-uniformity, unlike the homogeneous compartment temperature assumption in the current fire safety engineering practice. Furthermore, some large compartment fires may burn locally and they tend to move across entire floor plates over a period of time as the fuel is consumed. This kind of fire scenario is beginning to be idealized as 'travelling fires' in the context of performance‐based structural and fire safety engineering. However, the previous research of travelling fires still relies on highly simplified travelling fire models (i.e. Clifton's model and Rein's model); and no equivalent numerical tools can perform such simulations, which involves analysis of realistic fire, heat transfer and thermo-mechanical response in one single software package with an automatic coupled manner. Both of these hinder the advance of the research on performance‐based structural fire engineering. The author develops an extended travelling fire method (ETFM) framework and an integrated comprehensive tool with high computational expediency in this research, to address the above‐mentioned issues. The experiments conducted for characterizing travelling fires over the past two decades are reviewed, in conjunction with the current available travelling fire models. It is found that no performed travelling fire experiment records both the structural response and the mass loss rate of the fuel (to estimate the fire heat release rate) in a single test, which further implies closer collaboration between the structural and the fire engineers' teams are needed, especially for the travelling fire research topic. In addition, an overview of the development of OpenSees software framework for modelling structures in fire is presented, addressing its theoretical background, fundamental assumptions, and inherent limitations. After a decade of development, OpenSees has modules including fire, heat transfer, and thermo‐mechanical analysis. Meanwhile, it is one of the few structural fire modelling software which is open source and free to the entire community, allowing interested researchers to use and contribute with no expense. An OpenSees‐based integrated tool called SIFBuilder is developed by the author and co‐workers, which can perform fire modelling, heat transfer analysis, and thermo-mechanical analysis in one single software with an automatic coupled manner. This manner would facilitate structural engineers to apply fire loading on their design structures like other mechanical loading types (e.g. seismic loading, gravity loading, etc.), without transferring the fire and heat transfer modelling results to each structural element manually and further assemble them to the entire structure. This feature would largely free the structural engineers' efforts to focus on the structural response for performance-based design under different fire scenarios, without investigating the modelling details of fire and heat transfer analysis. Moreover, the efficiency due to this automatic coupled manner would become more superior, for modelling larger structures under more realistic fire scenarios (e.g. travelling fires). This advantage has been confirmed by the studies carried out in this research, including 29 travelling fire scenarios containing total number of 696 heat transfer analysis for the structural members, which were undertaken at very modest computational costs. In addition, a set of benchmark problems for verification and validation of OpenSees/SIFBuilder are investigated, which demonstrates good agreement against analytical solutions, ABAQUS, SAFIR, and the experimental data. These benchmark problems can also be used for interested researchers to verify their own numerical or analytical models for other purposes, and can be also used as an induction guide of OpenSees/SIFBuilder. Significantly, an extended travelling fire method (ETFM) framework is put forward in this research, which can predict the fire severity considering a travelling fire concept with an upper bound. This framework considers the energy and mass conservation, rather than simply forcing other independent models to 'travel' in the compartment (i.e. modified parametric fire curves in Clifton's model, 800°C‐1200°C temperature block and the Alpert's ceiling jet in Rein's model). It is developed based on combining Hasemi's localized fire model for the fire plume, and a simple smoke layer calculation by utilising the FIRM zone model for the areas of the compartment away from the fire. Different from mainly investigating the thermal impact due to various ratios of the fire size to the compartment size (e.g. 5%, 10%, 25%, 75%, etc.), as in Rein's model, this research investigates the travelling fire thermal impact through explicit representation of the various fire spread rates and fuel load densities, which are the key input parameters in the ETFM framework. To represent the far field thermal exposures, two zone models (i.e. ASET zone model & FIRM zone model) and the ETFM framework are implemented in SIFBuilder, in order to provide the community a 'vehicle' to try, test, and further improve this ETFM framework, and also the SIFBuilder itself. It is found that for 'slow' travelling fires (i.e. low fire spread rates), the near‐field fire plume brings more dominant thermal impact compared with the impact from far‐field smoke. In contrast, for 'fast' travelling fires (i.e. high fire spread rates), the far‐field smoke brings more dominant thermal impact. Furthermore, the through depth thermal gradients due to different travelling fire scenarios were explored, especially with regards to the 'thermal gradient reversal' due to the near‐field fire plume approaching and leaving the design structural member. This 'thermal gradient reversal' would fundamentally reverse the thermally‐induced bending moment from hogging to sagging. The modelling results suggest that the peak thermal gradient due to near‐field approaching is more sensitive to the fuel load density than fire spread rate, where larger peak values are captured with lower fuel load densities. Moreover, the reverse peak thermal gradient due to near‐field leaving is also sensitive to the fuel load density rather than the fire spread rate, but this reverse peak value is inversely proportional to the fuel load densities. Finally, the key assumptions of the ETFM framework are rationalised and its limitations are emphasized. Design instructions with relevant information which can be readily used by the structural fire engineers for the ETFM framework are also included. Hence more optimised and robust structural design under such fire threat can be generated and guaranteed, where we believe these efforts will advance the performance‐based structural and fire safety engineering.

No description available.

Made available in DSpace on 2016-06-02T19:19:58Z (GMT). No. of bitstreams: 1 OLIVEIRA_Robson_2013.pdf: 4428066 bytes, checksum: aefeb43146df9afeba619c532fb8d2f6 (MD5) Previous issue date: 2013-09-13 / Composite technology of a polymer matrix reinforced with artificial fibers, like fiberglass, Kevlar, carbon, etc., has become specialty in recent times moved by advances in technology in some sectors such as automotive and aerospace. The composites already have come a long way in replacing conventional materials like metals and Woods. However with the goal to reduce costs and provide a sustainable growth, science has directed his attention in reinforced compounds with renewable material such as natural fibers. In this work, a study was conducted of the dynamic behavior-mechanical and thermodynamic transitions of second order, as is the case of the glass transition temperature, matrix composite polyurethane elastomers with jute fiber reinforcement. The relaxation that occurs in glassy transition region, also called primary relaxation or relaxation α to amorphous polymers, molecular movements resulting from long distances, involving the main polymer chain segments. The matrix was formed by a MDI-BDO system provided by the company Metso Brazil, PU Division. Metso Brazil manufactures PU screens used in crushing sieves in the mining industry, and this work studied replacing the pure PU fiber by composite reinforced with jute. The material was prepared in an open heated to 100º C with controlled temperature, the system was synthesized in a mixer pre-polymer ratio automatic PU of Baulé on following conditions: MDI, 45º C to 9.5 bar; BDO, 45 C 5.7 bar and D20, 69 C a11 .2 bar. For the characterization of mechanical properties of composite dynamic-mechanical analysis was performed in tension in a temperature range of 35 to 160° C and bending creep. The results showed that the composite had formed showed lower creep deformation in bending test compared to pure polyurethane, but higher strain compared to the composite fiberglass. The flexural modulus (E ') of jute fiber composite showed a higher value at higher temperatures than the unreinforced material. The composi / A tecnologia de compósitos de uma matriz polimérica reforçada com fibras artificiais, com fibra de vidro, Kevlar, carbono, etc., tornou-se de grande interesse nos últimos tempos com os avanços da tecnologia em alguns setores como automobilístico e aeroespacial. Os compósitos já percorreram um longo caminho na substituição dos materiais convencionais como metais e madeiras, no entanto com o objetivo de reduzir custos e proporcionar um crescimento sustentável, a ciência tem direcionado sua atenção em compostos reforçados com material de fontes renováveis como as fibras naturais. No presente trabalho, foi realizado um estudo do comportamento dinâmico-mecânico e transições termodinâmicas de segunda ordem, como é o caso da transição vítrea, em compósito de matriz poliuretana elastomérica com reforço de fibra de juta. A matriz foi formada por um sistema MDI/BDO (reação entre um diisocianato de 4-4'-difenilmetano (MDI) e o 1,4-butanodiol (BDO), fornecida pela empresa Metso Brasil, divisão PU. A Metso Brasil fabrica telas de PU usadas em peneiras de britagem na indústria de mineração, sendo que o presente trabalho estudou a substituição do PU puro pelo compósito com fibra de juta. O material foi vazado em molde aberto na empresa em mesa aquecida a 100ºC com temperatura controlada. O sistema prepolímero foi sintetizado em um misturador automático de PU da Baulé nas seguintes condições: MDI 45ºC a 9,5 bar; BDO, 45ºC a 5,7 bar e D20, 69ºC a11,2 bar. Para a caracterização das propriedades mecânicas desse compósito foi realizada análise dinâmico-mecânica (DMA) em ensaios de tensão no intervalo de temperatura de 35 a 160 ºC. Os principais resultados mostraram que o compósito formado apresentou menor deformação de fluência em ensaio de flexão em relação ao poliuretano puro, porém maior deformação quando comparado com o compósito com fibra de vidro. O módulo flexural (E ) do compósito de fibra de juta apresentou um maior valor em temperaturas mais elevadas que o do material sem reforço. O compósito de fibra de juta foi solicitado no modo de tração e teve um comportamento de material menos dúctil.

Made available in DSpace on 2014-12-17T14:58:13Z (GMT). No. of bitstreams: 1 AlcioneOG_DISSERT.pdf: 4986234 bytes, checksum: d81c2eeeb91a55690b1f5b9671a9a5e3 (MD5) Previous issue date: 2011-08-26 / Use of natural fibres as a reinforcement material in the manufacture of composites show a series of advantages: availability, biodegradability, low weight and regeneration in relation to synthetic fibres, thus justifying its utilization. In the present research work, composites were developed with chicken feathers (KF), using unsaturated polyester resin as matrix, for diversified applications, mainly in the furniture/timber industry.At present, in Brazil the chicken feathers are used as part of the animal feed, even though this material possesses low aggregated value. The chicken feathers are hollow, light and resistant. After washing with water at room temperature, a part of the chicken feathers were treated with 2% NaOH. Composites were manufactured using treated and untreated chicken feathers with unsaturated orthothalic polyester resin and 1% peroxide as catalyser, obtained in the commerce. Samples with size 150x25x3 mm for mechanical tests were cut by laser in the composite plate. Mechanical analyses were carried out in the Laborat?rio de Metais e Ensaios Mec?nicos UFRN. All the analyses were in accordance with ASTM standards. SEM analyses were also carried out on the samples.In the analyses of the results obtained, it was observed that the composites made with untreated chicken feathers showed better results (Traction 11.406 MPa and 9.107 MPa Bending 34.947 and 20.918 MPa for samples with and without treatment respectively) compared to the composite with treated feathers. Very low values of the water absorption results, evidenced the impermeability characteristic of the feathers. From the SEM images, the structure, fracture and the fibre/matrix adsorption can be evidenced. In the flammability test, it was observed that despite the feathers having sulfur as a constituent, natural inhibitor of flame, no burning support of the composites, because the manufacturing process of the composite / O uso de fibras naturais como refor?o em comp?sitos apresenta uma s?rie de vantagens: abund?ncia, biodegradabilidade, baixo peso e regenerabilidade em rela??o ?s fibras sint?ticas, justificando sua utiliza??o. Na presente pesquisa foram desenvolvidos comp?sitos com penas de frango (KF), utilizando resina de poli?ster n?o-saturado como matriz. Atualmente, no Brasil, as penas de frango s?o utilizadas como parte de ra??o animal, por?m este produto possui um baixo valor agregado. As penas s?o um material oco, leve e resistente. Ap?s a lavagem com ?gua em temperatura ambiente uma parte das penas foi tratada com 2% de NaOH. Foram fabricados dois comp?sitos, um com as penas tratadas e outro sem tratamento, usando o processo de molde fechado por compress?o, utilizando a resina de poli?ster ortoft?lica e 1% de per?xido MEK (per?xido de metil etil cetona) como iniciador, adquiridos no com?rcio local. As amostras com 150x25x3 mm de tamanho para os ensaios mec?nicos foram cortadas a laser na placa do comp?sito. Os ensaios de tra??o e flex?o em tr?s pontos foram realizados no Laborat?rio de Metais e Ensaios Mec?nicos - UFRN. Todas as an?lises estavam de acordo com as normas da ASTM. As amostras resultantes dos ensaios mec?nicas foram avaliadas no MEV. Com base nas observa??es dos resultados nos ensaios mec?nicos, (Tra??o 11,2 Mpa e 8,3 Mpa; Flex?o 34,9 Mpa e 22,9 MPa para as amostras sem e com tratamento respectivamente) observou-se que os comp?sitos refor?ados com as penas sem tratamento apresentaram um melhor comportamento quando foram expostos a carregamentos tanto de tra??o quanto de flex?o. O ensaio de absor??o evidenciou nos valores de absor??o de ?gua, uma das caracter?sticas da prote?na existente nas penas, a queratina, a sua capaciade de impermiabiliza??o a ?gua. Nas imagens do MEV foi poss?vel verificar a estrutura da pena, as regi?es de ruptura do comp?sito e a ades?o fibra/matriz. No ensaio de inflamabilidade, observou-se que apesar das penas terem como constituinte o enxofre, inibidor natural de chama, n?o houve a susten??o da queima nos comp?sitos, devido o processo de fabrica??o do comp?sito

Made available in DSpace on 2014-12-17T14:58:14Z (GMT). No. of bitstreams: 1 JoaoPMS_DISSERT.pdf: 2368005 bytes, checksum: d7875a294c5267dc99db89f3b20a7106 (MD5) Previous issue date: 2012-03-14 / In the present work, three composites with distinct reinforcements (polyester, modal e polyester + modal), all if a unsaturated orthophthalic polyester resin as matrix were used, in order to conduct a comparative study by mechanical tests and water absorption. The fibre mats were prepared in a mat preparatory by immersion developed in the Textile Engineering Laboratory. The composites were manufactured using a closed mould process by compression using an unsaturated orthophthalic polyester resin as matrix and 1% MEK (methyl ethyl ketone peroxide) as an initiator. In each composite twelve samples with the dimensions of 150x25x3 mm were cut randomly for the mechanical analysis (tension x extension, three points bending and water absorption and Scanning Electron Micsroscopy). The mechanical tests were carried out in the Laborat?rio de Metais e Ensaios Mec?nicos UFRN . All the analyses were carried out according to the ASTM norms. The resultant samples from the mechanical analysis were subjected for the Scanning Electron Microscopy analysis. Based on the results obtained, it was observed that the reinforced composite with two fibres (modal + polyester) presented better results in comparison to the other two composites both in the tension/extension as well on the three point bending tests. In the water absorption test, it was possible to observe an equilibrium in the water absorption by the modal and polyester composite, due to the union of the two fibres. In the SEM images, the regions of rupture in the composites as well as the adsorption between the fiber and the matrix could be observed / No presente trabalho foram fabricados tr?s comp?sitos com refor?os distintos (poli?ster, modal e poli?ster + modal), todos com uma matriz de resina de poli?ster ortofit?lico n?o saturado, com o objetivo de realizar um estudo comparativo atrav?s de ensaios mec?nicos e absor??o d ?gua. As mantas de fibras foram preparadas num preparador de manta por imers?o desenvolvido no Laborat?rio de Engenharia T?xtil da UFRN. Os comp?sitos foram fabricados usando o processo de molde fechado por compress?o, utilizando a resina de poli?ster ortoft?lica e 1% de per?xido MEK (per?xido de metil etil cetona) como iniciador. Em cada comp?sito foram cortadas doze amostras aleatoriamente, com as dimens?es 150x25x3 mm, para avalia??o atrav?s de ensaios mec?nicos (resist?ncia ? tra??o e ? flex?o, absor??o d agua e microscopia eletr?nica de varredura). Os ensaios de tra??o e flex?o em tr?s pontos foram realizados no Laborat?rio de Metais e Ensaios Mec?nicos - UFRN. Todas as an?lises estavam de acordo com as normas da ASTM. As amostras resultantes dos ensaios mec?nicas foram avaliadas no MEV. Com base nos resultados dos ensaios mec?nicos, observou-se que o comp?sito refor?ado com as duas fibras em conjunto (poli?ster+modal) apresentou um melhor comportamento quando foram expostos a carregamentos tanto de tra??o quanto de flex?o. No ensaio de absor??o d agua foi poss?vel observar um equilibribio na absor??o de umidade do comp?sito com modal e poli?ster, devido a uni?o das duas fibras. Nas imagens do MEV foi poss?vel ver as regi?es de ruptura do comp?sito e a ades?o entre a fibra e a matriz

Submitted by Biblioteca da Faculdade de Farmácia (bff@ndc.uff.br) on 2018-01-16T14:11:34Z No. of bitstreams: 1 HINGRED BOSCH.pdf: 3018248 bytes, checksum: 606ae06709470089da6bd43d30cd5b37 (MD5) / Made available in DSpace on 2018-01-16T14:11:34Z (GMT). No. of bitstreams: 1 HINGRED BOSCH.pdf: 3018248 bytes, checksum: 606ae06709470089da6bd43d30cd5b37 (MD5) / Este trabalho teve como objetivo estudar a produção e as características de filmes poliméricos constituídos por poli(álcool vinílico) (PVA) e carboximetilcelulose (CMC) a serem utilizados posteriormente na produção de curativos primários para tratamento de feridas. Os polímeros escolhidos apresentam grau farmacêutico e suas misturas foram preparadas na proporção de PVA/CMC 9:1. Os polímeros inicialmente foram misturados em câmara fechada de mistura Haake Rheomix na intenção de promover misturas físicas. Nesta etapa foram estabelecidas 6 condições de mistura variando-se a temperatura da câmara e a velocidade de mistura. Esperava-se que ocorresse a fusão dos componentes durante o processo, o que não ocorreu. Para a formação dos filmes poliméricos foi testado o processo de prensagem em prensa hidráulica a quente e o processo de vazamento de soluções poliméricas em placas de vidro com posterior secagem. Não foram obtidos filmes adequados aos ensaios com a técnica de prensagem a quente, porém com técnica de vazamento se conseguiu a formação de bons filmes; com isso os filmes obtidos por esta técnica foram caracterizados quanto a propriedades físico-químicas, térmicas e mecânicas. Pode-se concluir que os filmes de PVA/CMC, obtidos pela técnica de vazamento, apresentaram características físicas, como a alta capacidade de inchamento em água e PBS, e mecânicas, como a resistência a ruptura e ao rasgamento, adequadas à utilização destes filmes como curativos para feridas / This work aimed to study the production and characteristics of poly(vinyl alcohol) (PVA) and carboxymethylcellulose (CMC) polymer films to be used later in the production of primary dressings for wound treatment. The polymers chosen were pharmaceutical grade and mixtures thereof were prepared in the ratio of 9:1 PVA / CMC. The polymers were initially mixed in a closed Haake Rheomix blend chamber in order to promote physical blends. In this step, 6 mixing conditions were established by varying the chamber temperature and the mixing speed. The melting of the components was expected to occur during the process, which did not occur. For the formation of the polymer films the pressing process was tested in a hot hydraulic press and the process of casting polymer solutions into glass plates with subsequent drying. It was not obtained films suitable for the tests with the technique of hot pressing, but with casting technique the formation of good films was achieved; and the films obtained by this technique are characterized by physical, chemical, thermal and mechanical properties. It can be concluded that the PVA/CMC films, obtained by the casting technique, presented physical characteristics, such as high swelling capacity in water and PBS, and mechanical, such as tear strength and tear resistance, suitable for the use of these films as wound dressings

Grâce à leur géométrie spécifique, faite d’une superposition de couches unidirectionnelles de fibres continues, liées par des coutures plus ou moins complexes, les renforts NCF (Non-Crimp Fabric) possèdent une combinaison de propriétés intéressantes. Ces propriétés permettent l'utilisation de procédés de production tels que le procédé RTM (Resin Transfer Moulding) et permettent l’utilisation des caractéristiques de rigidité élevée des fibres dans la pièce finale. Ainsi, ces renforts trouvent des applications dans différents secteurs de l'industrie des composites et notamment en aéronautique. Les couches, formées de fibres parallèles juxtaposées, sont liées par différents types de coutures. Ce lien conduit à des propriétés différentes de celles observées sur un renfort tissé où les mèches de chaîne et de trame sont liées par entrelacement. Par conséquent, la cinématique de déformation des renforts NCF secs lors de la mise en forme peut être différente. Dans ce travail de recherche, nous menons d'abord une étude expérimentale sur les mécanismes de déformation se produisant lors de tests élémentaires et lors d’une expérience d’emboutissage. Plusieurs renforts NCF et un renfort interlock sont étudiés. Ensuite, nous introduisons un nouveau modèle pour la simulation de la mise en forme du renfort de composite NCF sec. Cette approche implique l’utilisation d’éléments finis lagrangien semi-discrets pour représenter les couches et d’éléments de barres pour représenter les coutures. Ce modèle nécessite un algorithme de contact spécifique pour gérer la relation entre les éléments finis. Une loi de frottement de Coulomb avec seuil de glissement est utilisée. Enfin, le modèle est validé par l’intermédiaire de l’essai de bias test puis la mise en forme sur un hémisphère est simulée et comparée à l'expérience. / Due to their specific geometry, made of overlapping layers of unidirectional plies of continuous fibres, linked by more or less complex stitching, non-crimp fabric (NCF) reinforcements have advantageous combination of properties. These properties enable the use of process in production such as RTM process and allow the full use of stiffness characteristics of the fibres in the final part. Thus, these reinforcements find applications in different areas of composites industry. The plies of juxtaposed parallel fibres are bound by a tricot or a chain stitching with a lead. This link leads to different properties of the NCF compared to those of a woven reinforcement where the warp and weft yarns are linked by the interweaving. Therefore, deformation kinematics of dry NCF reinforcements might be different. In this research work, we first carry out an experimental study on deformation mechanisms occurring during elementary tests and a drawing experiment. Several non-crimp fabrics and an interlock fabric are studied. Then, we introduce a new model for the simulation of the dry composite reinforcement preforming. This approach involves a semi discrete Lagrangian finite element to represent the plies and a truss element to represent the stitching. This model requires a specific contact algorithm to handle the relation between the finite elements. A Coulomb law with a friction threshold is used. Finally, the model is validated using the bias extension test and the preforming on a hemisphere is simulated and compared to the experiment.

Fibre Reinforced Polymer Composites are extensively used in aircraft structures because of its high specific stiffness, high specific strength and tailorability. Though Fibre Reinforced Polymers offer many advantages, they are not free from problems. The damage of different nature, e.g., service mechanical damages, fatigue damage or environmental damage can be observed during operating conditions. Among all the damages, manufacturing or service induced, delamination related damage is the most important failure mechanisms of aircraft-composite structures and can be detrimental for safety. Delamination growth under fatigue loading may take place due to local buckling, growth from free edges and notches such as holes, growth from ply-drops and impact damaged composites containing considerable delamination. Delamination growth can also occur due to interlaminar stresses, which can arise in complex structures due to unanticipated loading. The complex nature of composite failure, involving different failure modes and their interactions, makes it necessary to characterize/identify the relevant parameters for fatigue damage resistance, accumulation and life prediction. An effort has been made in this thesis to understand the fatigue behavior of carbon fibre reinforced epoxy laminates under aircraft wing service loading conditions. The study was made on laminates with different lay-up sequences (quasi-isotropic and fibre dominated) and different geometries (plain specimen, specimen with a hole and ply-drop specimen). The fatigue behaviour of the composite was analyzed by following methods: . Ultrasonic C-Scan was used to characterize the delamination growth. . Dynamic Mechanical Analysis (DMA) was done to study the interfacial degradation due to fatigue loading. In this analysis, the interfacial strength indicator and interfacial damping were calculated. The DMA also provides the storage modulus degradation under fatigue loading. . Scanning electron microscope examination was carried out to understand the fatigue damage mechanisms. . A semi-empirical phenomenological model was also used to estimate the residual fatigue life. This research work reveals that the Carbon Fibre Reinforced Polymer laminates are in the safe limit under service loading conditions, except the specimen with a hole. The specimen with a hole showed delaminations around the hole due to stress concentration and higher interlaminar stresses at the hole edges and this delamination is found to be associated with fibre breakage and fibre pullout. The quasi-isotropic laminate is found to show poorer fatigue behaviour when compared to fibre dominated laminate and ply-drop also shows poor performance due to high stress concentration in the ply-drop region.

[EN] The development of new and more complex polymeric materials involves challenging problems to basic sciences. The relationship between structure and molecular dynamics assumes great importance for the future development of novel technologies based on such polymers. Thus, the understanding of how small changes in the chemical structure affect the properties of the material is essential to progress in the technological and scientific area. An in-depth analysis of the molecular mobility leads to establish the structure-properties relationships. On this basis, the main aim of the present work is to study the molecular mobility of two different families of polymeric materials. For this purpose, the experimental techniques mainly used were Differential Scanning Calorimetry (DSC) and Dielectric Relaxation Spectroscopy (DRS). The first family of polymers characterized was a series of chemically cross-linked copolymers composed by Vinylpyrrolidone (VP) and Butyl Acrylate (BA) monomers. In the first place, the influence of the monomer molar ratio (XVP/YBA) on the copolymer properties was studied. Thus, a Fourier Transform Infrared Spectroscopy (FTIR) analysis verified dipole-dipole interactions between amide groups. The influence of these interactions on several parameters related to the molecular mobility was evidenced by the DSC, DRS and Dynamic Mechanical Analysis (DMA) techniques. Secondly, the effect of the cross-link density on the molecular dynamics of 60VP/40BA copolymers was analyzed using DSC and DRS. One single glass transition was detected by DSC measurements. The DRS analysis showed that an increase of the cross-linking produced a typical effect on the alpha process dynamics. However, the beta process, which possessed typical features of pure JG relaxation, unexpectedly lost the intermolecular character for the highest cross-linker content. The fastest gamma process was relatively unaffected. The second family of polymeric materials studied was a series of segmented polycarbonatediol polyurethane (PUPH) modified with different amounts of expanded graphite (EG) conductive filler. Scanning Electron Microscopy (SEM), X-ray diffraction measurements and FTIR analysis demonstrated a homogeneous dispersion of the EG filler in the matrix. DRS was used to study the dielectric properties of the PUPH/EG composites. The dielectric permittivity of the composites showed an insulator to conductor percolation transition with the increase of the EG content (2030 wt%). The addition of expanded graphite to the matrix caused a dramatic increase in the electrical conductivity of ten orders of magnitude, which is an indication of percolative behavior. / [ES] El desarrollo de nuevos materiales poliméricos de mayor complejidad produce un desafío cada vez mayor en el área de las ciencias básicas. La relación entre la estructura y la dinámica molecular resulta de gran importancia para el desarrollo de nuevas tecnologías basadas en estos materiales poliméricos. Así, una mayor comprensión de cómo pequeños cambios en la estructura química afectan a las propiedades de los materiales resulta esencial para el progreso científico y tecnológico. Un análisis en profundidad de la movilidad molecular permite establecer las relaciones estructura-propiedades. Partiendo de esta base, el principal objetivo del presente trabajo es el estudio de la movilidad molecular de dos familias diferentes de materiales poliméricos. Para ello, las técnicas experimentales utilizadas fueron principalmente la Calorimetría Diferencial de Barrido (DSC) y la Espectroscopia de Relajación Dieléctrica (DRS). La primera familia de polímeros caracterizada fue una serie de copolímeros entrecruzados químicamente compuestos por los monómeros Vinilpirrolidona (VP) y Acrilato de Butilo (BA). En primer lugar, se estudió la influencia de la proporción molar de monómero (XVP/YBA) en las propiedades del copolímero. A través de un análisis por Espectroscopia de Infrarrojo por Transformada de Fourier (FTIR), se verificó la existencia de interacciones dipolo-dipolo entre los grupos amida. Mediante el análisis por DSC, DRS y Análisis Dinamomecánico (DMA), se evidenció la influencia de estas interacciones en diferentes parámetros relacionados con la movilidad molecular. En segundo lugar, se analizó el efecto de la densidad de entrecruzamiento en la dinámica molecular de los copolímeros 60VP/40BA usando DSC y DRS. A través de las medidas de DSC se observó una única transición vítrea para todos los entrecruzamientos. El análisis por DRS mostró como el incremento en entrecruzante produjo el típico efecto en la dinámica del proceso alpha, pero sin embargo, el proceso beta, que tenía las características típicas de una relajación JG, perdió de forma inesperada su carácter intermolecular para el mayor contenido en entrecruzante. El proceso gamma no se vio afectado. La segunda familia de materiales poliméricos estudiada fue una serie de poliuretanos segmentados (PUPH) modificados con diferentes cantidades de grafito expandido (EG), utilizado como relleno conductivo (desde 0 a 50% en peso). El análisis de los resultados obtenidos mediante Microscopía Electrónica de Barrido (SEM), Difracción de Rayos X y FTIR demostró la homogénea dispersión del relleno de EG en la matriz de PUPH. La técnica DRS se usó para estudiar las propiedades dieléctricas de los materiales compuestos PUPH/EG. La permitividad dieléctrica de los materiales mostró una transición de percolación desde aislante a conductor al incrementarse el contenido en EG (rango de 20-30% en peso). La adición de grafito expandido a la matriz de PUPH causó un incremento significativo en la conductividad dieléctrica de diez órdenes de magnitud, lo que indica el comportamiento de percolación. / [CAT] El desenvolupament de nous materials polimèrics de major complexitat produeix un desafiament cada vegada major en l'àrea de les ciències bàsiques. La relació entre l'estructura i la dinàmica molecular resulta de gran importància per al desenrotllament de noves tecnologies basades en aquests materials polimèrics. Així, una major comprensió de com petits canvis en l'estructura química afecten a les propietats dels materials, resulta essencial per al progrés científic i tecnològic. Un anàlisis en profunditat de la mobilitat molecular permet establir les relacions estructura-propietats. Partint d'aquesta base, el principal objectiu del present treball és l'estudi de la mobilitat molecular de dues famílies diferents de materials polimèrics. Per a això, les tècniques experimentals utilitzades van ser principalment la Calorimetria Diferencial de Rastreig (DSC) i l'Espectroscòpia de Relaxació Dielèctrica (DRS). La primera família de polímers caracteritzada va ser una sèrie de copolímers entrecreuats químicament compostos pels monòmers Vinilpirrolidona (VP) i Acrilat de Butilo (BA) . En primer lloc, es va estudiar la influència de la proporció molar de monòmer (XVP/YBA) en les propietats del copolímer. A través d'una anàlisi per Espectroscòpia d'Infraroig per Transformada de Fourier (FTIR), es va verificar l'existència d'interaccions dipol-dipol entre els grups amida. Mitjançant l'anàlisi per DSC, DRS i Anàlisi Dinamomecánico (DMA), es va evidenciar la influència d'aquestes interaccions en diferents paràmetres relacionats amb la mobilitat molecular. En segon lloc, es va analitzar l'efecte de la densitat d'entrecreuament en la dinàmica molecular dels copolímers 60VP/40BA mitjançant DSC i DRS. A través de les mesures de DSC es va observar una única transició vítria per a tots els continguts d'agent entrecreuant . L'anàlisi per DRS va mostrar com l'increment en agent entrecreuant va produir l'efecte esperat en la dinàmica del procés alfa. En canvi, el procés beta, que tenia les característiques típiques d'una relaxació JG, va perdre de forma inesperada el seu caràcter intermolecular per al major contingut en agent entrecreuant. El procés més ràpid gamma no es va veure afectat. La segona família de materials polimèrics estudiada va ser una sèrie de poliuretans segmentats (PUPH) modificats amb diferents quantitats de grafit expandit (EG) , utilitzat com a farcit conductiu (des de 0 a 50% en pes). L'anàlisi dels resultats obtinguts per mitjà de Microscòpia Electrònica de Rastreig (SEM), Difracció de Rajos X i FTIR va mostrar la dispersió homogènia del EG en la matriu de PUPH. La tècnica DRS es va utilitzar per a estudiar les propietats dielèctriques dels materials compostos PUPH/EG. La permitivitat dielèctrica dels materials va mostrar una transició de percolació des d'aïllant a conductor amb l'increment de contingut en EG (20-30% en pes). L'addició d'EG a la matriu de PUPH va causar un increment significatiu en la conductivitat dielèctrica, de deu ordes de magnitud. / Redondo Foj, MB. (2015). A contribution to the study of the molecular mobility in polymeric materials by Thermal and Dielectric Analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59457 / TESIS