Les structures aéronautiques peuvent être soumises à des sollicitations sévères telles que les collisions, les impacts de volatiles, etc … Sous l’effet de ces sollicitations rapides, qui du fait de leurs temps caractéristiques très courts limitent les transferts thermiques, le matériau peut dissiper l’énergie dans des zones de déformation localisée qui peuvent conduire à une ruine prématurée de la structure. Le travail de la thèse porte sur la définition d’une méthodologie expérimentale destinée à étudier les conditions de rupture de matériaux à haute résistance à vocation aéronautique consécutives à un endommagement dynamique. Ce travail comprend : •la mise au point d’essais rapides de cisaillement ; •des observations microstructurales des matériaux avant et après sollicitation ; •la simulation numérique des essais. / Aeronautical structures may be submitted to severe loading such as collisions, bird strike, etc. Under dynamic loading, involving quasi adiabatic conditions, the material may dissipate energy within zones of localised deformation wich may lead to the premature failure of the structure. The PhD work aims at defining an experimental methodology devoted to study the conditions of fracture of aeronautical, high strength materials intervening after dynamic damage. Tasks include notably: * definition of dynamic shear tests * microstructural observation of the material before and after loading * numerical simulation * Development of fracture criterion

A eficiência de antocianinas como inibidores de corrosão da liga de alumínio 2024-T3 foi avaliada através de medidas eletroquímicas como a espectroscopia de impedância eletroquímica e polarizações anódica e catódica. Soluções de NaCl 0,025 mol.L-1 contendo diferentes concentrações (800, 1000, 2000, 3000, 5000 e 7200 ppm) de antocianinas extraídas da uva foram preparadas para analisar o efeito da presença destas substâncias quando em contato com a liga de alumínio 2024-T3. Medidas de espectroscopia de impedância eletroquímica apresentaram uma diminuição sobre a dispersão dos pontos nas regiões de baixas frequências com o acréscimo do tempo de contato das antocianinas com a superfície da liga de alumínio 2024-T3 de 1 hora para 3 dias de imersão. Além disso, o comportamento indutivo nestas regiões decresceu após 3 dias de imersão com uma elevação considerável da resistência à polarização e da eficiência de inibição em 1000 ppm de antocianinas. Sob polarizações anódica e catódica, também foi verificado um melhoramento generalizado das propriedades anticorrosivas como potencial de corrosão, corrente de corrosão e eficiência de proteção contra a corrosão, para a concentração de 1000 ppm de antocianinas. Análises de microscopia eletrônica de varredura, microscopia de força atômica e espectroscopia por dispersão de energia, confirmam a adsorção de antocianinas na superfície da liga, assim como medidas de absorbância após 3 dias de imersão. / The efficiency of anthocyanins as corrosion inhibitor of the 2024-T3 aluminum alloy was evaluated by electrochemical measurements such as electrochemical impedance spectroscopy and anodic and cathodic polarizations. NaCl solutions 0.025 mol.L-1 containing different concentrations (800, 1000, 2000, 3000, 5000 and 7200 ppm) of anthocyanins extracted from grape were prepared to examine the effect of the presence of these substances when in contact with the 2024-T3 aluminum alloy. Electrochemical impedance spectroscopy measurements showed a decrease on the dispersion of points in the lower frequency regions with an increase of contact time of anthocyanins with the surface of the 2024-T3 aluminum alloy from 1 hour to 3 days of immersion. In addition, the inductive behavior in these regions decreased after 3 days of immersion with a considerable increase of the polarization resistance and inhibition efficiency of 1000 ppm of anthocyanins. Under cathodic and anodic polarizations, it was noted a general improvement in the anticorrosive properties such as corrosion potential, corrosion current and efficiency of protection against corrosion for the concentration of 1000 ppm of anthocyanins. Analyses of scanning electron microscopy, atomic force microscopy and energy dispersive spectroscopy confirm anthocyanins adsorption on to the surface alloy, as well as absorbance measurements in a spectrophotometer after 3 days of immersion.

Stationary (static) shoulder friction stir welding (SSFSW) is a variant of conventional friction stir welding (FSW) that was originally invented to improve the quality of welds produced with titanium alloys. Its predominant advantage is a reduction of the severe through thickness temperature gradients seen in conventional FSW, when welding low thermal conductivity alloy. However, SSFSW has rarely been utilised as a method to weld aluminium alloys because it is generally thought that in conventional FSW the rotating shoulder plays an essential role in the heat generation and, due to the high thermal conductivity of aluminium alloys, a rotating shoulder is beneficial for the welding process. In the work presented, the advantages of SSFSW have been examined when welding a typical high strength aluminium alloy AA7050-T7651. The process window for each approach has first been determined, and the optimum welding conditions were systematically evaluated, using power-rotation rate curves. Direct comparison of the two processes was subsequently carried out under these optimum conditions. It has been demonstrated that SSFSW can dramatically improve the quality of a weld's surface finish. Under optimum conditions it has also been shown that SSFSW was able to weld with approximately a 30% lower heat input than FSW and the stationary shoulder led to a narrower heat affected zone (HAZ). As a result, the through thickness properties of SSFSW were much better and more homogeneous than that for FSW, in terms of grain sizes, hardness and cross-weld mechanical properties. Uniaxial tensile tests proved that the average tensile strength of SSFSW samples was around 500 MPa, which was about 100 MPa larger than that of the FSW sample. Also, it was shown that during tensile testing the deformation zones, which correspond to minima in the hardness distribution of SSFSW welds, were about half the size of those found in FSW welds under the same traverse speed. The mechanisms that give rise to these advantages have been investigated systematically, focusing on directly comparing the SSFSW and FSW processes, and are discussed aided by finite element modelling (FEM) of the heat distribution in welds produced by each process and microstructural investigations.

Future nuclear fission reactors (GEN IV) are designed to include fast breeder reactor technologies, which can accept transuranics (elements heavier than uranium) as fuel. This has the potential of being more fuel efficient but requires the closing of the nuclear fuel cycle: full recycling of existing and newly generated nuclear waste to extract uranium and transuranic elements which can be reused as fuel. In the UK a system being investigated is electrochemical pyroprocessing which uses molten LiCl-KCl eutectic (LKE), which aims to recover uranium by electrodeposition on an inert (steel) electrode and the transuranics by electrodeposition as alloys with an active metal electrode (bismuth, cadmium or aluminium). Of the three active metal candidates, aluminium has the best separation efficiency of actinides and lanthanides, which is important as lanthanides are neutron poisons and so are not to be extracted. The development of pyroprocessing requires fundamental understandings of electrochemical alloy formation, as well as on-line monitoring tools to ensure the reprocessing occurs safely and efficiently. To that end, this thesis investigates cerium-aluminium alloying (a non-radioactive model system for plutonium-aluminium) on macro- and microelectrodes to understand the limiting factors during the alloying reaction at each electrode scale and also the circumstances under which the Ce3+ concentration can be reliably determined for on-line monitoring. On a bulk aluminium macroelectrode one cerium-aluminium alloying reaction was observed. This reaction was kinetically limited by the phase change from cerium insertion into the aluminium, and resulted in lattice expansion and progressive roughening of the electrode surface. These factors made it difficult to reliably calculate the Ce3+ concentration. Li+ from the solution was also able to reduce and form alloys with aluminium, approximately 0.3 V more negative than the first cerium-aluminium alloying peak. Since lithium atoms are smaller than cerium, and there is an abundance of Li+ in the salt, lithium-aluminium alloy was found to form preferentially to cerium-aluminium alloy at these more negative potentials. By co-depositing Al3+ and Ce3+ together on a tungsten electrode which is inert under these conditions (it does not alloy), the kinetic barrier to alloy formation by cerium insertion was decreased, which is beneficial to studying the thermodynamics of alloying. Studies of pure aluminium plating and pure cerium plating showed each individual reaction was diffusion limited, with an increased contribution of convection to the mass transport at slow scan rates. Co-deposition on macroelectrodes with a low ratio of [CeCl3]:[AlCl3] showed only one cerium-aluminium alloying peak. The co-deposition currents, and ratio of oxidation peaks charges, showed that co-deposition was occurring with both species under diffusion control, resulting in an amorphous alloy with a Ce:Al ratio that smoothly varied with the [CeCl3]:[AlCl3] ratio. This was in contrast to the alloying behaviour of cerium with liquid bismuth, in which co-deposition occurred at specific ratios determined by the crystal phases that could be formed at the applied potentials, with higher co-deposition ratios being achieved at more negative potentials. Co-deposition on macroelectrodes with a high ratio of [CeCl 3]:[AlCl3] could result in up to five cerium-aluminium alloy peaks, corresponding to all five CexAly crystalline phases predicted by the phase diagram. This phase change from amorphous to crystalline was promoted by the high Ce:Al ratio in the amorphous alloy resulting from the high [CeCl3]:[AlCl3] ratio and by plating pure cerium on the surface, which could then insert into the alloy. Charge analysis of these peaks confirmed the expected stoichiometries of the crystal phase from these in-situ measurements which is important for rapid analysis, whereas all previous literature has relied on ex-situ techniques which cooled the alloy, possibly changing its composition and structure. In all circumstances of alloy formation on macroelectrodes, the rate of reduction of Ce3+ was time dependent and sensitive to convection. This significantly complicated analysis of the electrochemical signal, making it very difficult to reliably calculate the concentration of Ce3+, which is required for on-line monitoring. Co-deposition on in-house microfabricated tungsten microelectrodes resulted in steady state currents for both pure aluminium deposition and cerium-aluminium co-deposition (up to the beginning of lithium-aluminium alloying). Thus, unlike on macroelectrodes, the deposition rate occurred at the flux ratio of each species from solution and only one oxidation peak was observed corresponding to the amorphous cerium-aluminium phase, even at high [CeCl3]:[AlCl3] ratios. The steady state alloying current meant that calculating the Ce3+ concentration was relatively simple from co-deposition on microelectrodes. Co-deposition was highly beneficial for studying alloying, however to avoid the addition of Al3+ to the molten salt, in-house microfabricated thin film aluminium microelectrodes were also used to study alloying. Alloying on microfabricated thin film aluminium microelectrodes was hampered by the formation of a native aluminium oxide layer, which prevented cerium insertion into the aluminium. The oxide layer could be disrupted by reduction of lithium, which showed steady state currents (albeit with significant capacitance) could be achieved for alloying by cerium insertion. However, the full surface area of the microelectrode could not be attained and all microelectrodes lost their aluminium layer after multiple lithiation/de-lithiation cycles. These devices need further development to overcome the oxide layer, or prevent its formation, in order to study alloying in greater detail with aluminium microelectrodes to fully realise their advantages for sensing and monitoring in pyroprocessing.

The comprehension of the viscoelastic behaviour of metals is of high interest as these materials are subjected to dynamic loads in most of their structural applications, and also because it enables a deeper understanding of several technologically essential properties, like mechanical damping and yielding. Thus, research on this field is needed not only because it may lead to new potential applications of metals, but also because predictability of the fatigue response may be greatly enhanced. Indeed, fatigue is the consequence of microstructural effects induced in a material under dynamic loading, while the viscoelastic behaviour is also intimately linked to the microstructure. Accordingly, the characterization of the viscoelastic response of a material offers an alternative method for analysing its microstructure and ultimately its fatigue behaviour. This research is aimed at the identification, characterization and modelling of the effects of temperature, excitation frequency and microstructure/phase transformations (when present) on the viscoelastic behaviour of aluminium alloys AA 7075-T6 and AA 2024-T3, and of pure aluminium in the H24 temper. The identification of the mechanical relaxation processes taking place and the relation between the viscoelastic response of AA 7075-T6 and AA 2024-T3 and the fatigue behaviour will be attempted for all these materials. Finally, we intend to investigate possible influences of the dynamic loading frequency on fatigue, and especially the existence of a threshold frequency marking the transition from a static-like response of the material to the advent of fatigue problems. AA 7075-T6 and AA 2024-T3 were selected for this study because these alloys are key representatives of their important families and are highly suitable to a number of industrial applications in the aerospace sector and transport industry. Pure aluminium was selected because of the inherent interest of this metal, for comparison purposes and for discussing the phenomena observed for the alloys. To accomplish the objectives, the viscoelastic response of the materials was measured experimentally with a Dynamic- Mechanical Analyser (DMA). The results were combined with Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC). An analytical model was proposed which fits the storage modulus up to 300 ºC. The model takes into account the effect of temperature, the excitation frequency and the concentration of some precipitates for the alloys. This allows us to test models proposed for the reaction rates of the associated microstructural transformations, to determine their kinetic parameters and to characterize their influence on the viscoelastic behaviour, showing that the DMA is a good tool for studying the material microstructure, phase transformation kinetics and the influence of transformations on the viscoelastic properties of materials. The Time-Temperature Superposition (TTS) principle has been successfully applied to the DMA data, providing master curves for the storage and loss moduli. Also, it is proposed that the decrease of yield and fatigue strength with temperature observed in some aluminium alloys may be due to the internal friction increase with temperature. Finally, the existence of a threshold frequency is suggested, below which materials subjected to dynamic loading exhibit a static-like, elastic response, such that creep mechanisms dominate and deterioration due to fatigue may be neglected. A procedure to estimate this transition frequency is proposed. / La comprensión del comportamiento visco-elástico de los metales es de gran interés ya que estos están sometidos a cargas dinámicas en la mayoría de sus aplicaciones estructurales, y también porque posibilita un conocimiento más profundo de varias propiedades esenciales tecnológicamente, como el amortiguamiento mecánico y el límite elástico. Así, la investigación en este campo es necesaria no sólo porque puede conducir hacia nuevas aplicaciones potenciales de los metales, sino también porque la capacidad de predecir el comportamiento en fatiga de los mismos puede verse ampliamente mejorada. De hecho, la fatiga de los metales es consecuencia de efectos microestructurales inducidos en el material bajo cargas dinámicas, y el comportamiento visco-elástico está también íntimamente relacionado con la microestructura. Así, la caracterización de la respuesta visco-elástica de un material ofrece un método alternativo para analizar su microestructura y, en último término, su respuesta en fatiga. Este trabajo tiene por objetivos la identificación, caracterización y modelización de los efectos de la temperatura, la frecuencia de excitación y la microestructura/transformaciones de fase en el comportamiento visco-elástico de las aleaciones de aluminio AA 7075-T6 y AA 2024-T3, y de aluminio puro en estado H24. Se aborda también la identificación de los procesos de relajación mecánicos que tienen lugar en estos materiales y la identificación de la relación entre el comportamiento visco-elástico de AA 7075-T6 y 2024-T3 y su respuesta en fatiga. Finalmente, se intentará investigar posibles influencias de la frecuencia de la carga dinámica en la fatiga, y en especial la existencia de una frecuencia umbral que marque la transición desde una respuesta cuasi-estática del material hacia la aparición de problemas de fatiga. AA 7075-T6 y AA 2024-T3 fueron seleccionadas porque son representantes clave de sus importantes familias de aleaciones, y son altamente adecuadas para un gran número de aplicaciones en los sectores aeroespacial y del transporte. El aluminio puro fue seleccionado para este estudio por su interés inherente, y para realizar comparaciones y discutir algunos de los fenómenos observados en las aleaciones. Para cumplir los objetivos, el comportamiento visco-elástico de los materiales fue medido experimentalmente con un Dynamic-Mechanical Analyser (DMA). Los resultados se combinaron con microscopía electrónica y calorimetría. Se propuso un modelo analítico que ajusta la componente real del módulo elástico dinámico (el storage modulus) hasta 300 ºC. El modelo toma en consideración los efectos de la temperatura, la frecuencia de la carga dinámica y la concentración de ciertos precipitados para el caso de las aleaciones. Esto permitió testear modelos propuestos para las velocidades de reacción de las transformaciones microestructurales asociadas, determinar sus parámetros cinéticos y caracterizar su influencia en el comportamiento visco-elástico, demostrando que el DMA es una buena herramienta para estudiar la microestructura del material, la cinética de las transformaciones de fase y la influencia de las transformaciones en las propiedades visco-elásticas de los materiales. El principio de superposición de tiempo y temperatura ha sido aplicado con éxito, proporcionando curvas maestras para las componentes del módulo elástico dinámico. Asimismo, se sugiere que el descenso en el límite elástico y la resistencia a fatiga con la temperatura observado en algunas aleaciones de aluminio puede ser debido al incremento de la fricción interna con la temperatura. Finalmente, se propone la existencia de una frecuencia umbral, por debajo de la cual los materiales sometidos a cargas dinámicas exhiben una respuesta cuasi-estática y elástica, de tal modo que mecanismos de termofluencia son dominantes y el deterioro del material debido a fatiga puede ser despreciado. Se propone un procedimiento para estimar esta frecuencia de transición.

A eficiência de antocianinas como inibidores de corrosão da liga de alumínio 2024-T3 foi avaliada através de medidas eletroquímicas como a espectroscopia de impedância eletroquímica e polarizações anódica e catódica. Soluções de NaCl 0,025 mol.L-1 contendo diferentes concentrações (800, 1000, 2000, 3000, 5000 e 7200 ppm) de antocianinas extraídas da uva foram preparadas para analisar o efeito da presença destas substâncias quando em contato com a liga de alumínio 2024-T3. Medidas de espectroscopia de impedância eletroquímica apresentaram uma diminuição sobre a dispersão dos pontos nas regiões de baixas frequências com o acréscimo do tempo de contato das antocianinas com a superfície da liga de alumínio 2024-T3 de 1 hora para 3 dias de imersão. Além disso, o comportamento indutivo nestas regiões decresceu após 3 dias de imersão com uma elevação considerável da resistência à polarização e da eficiência de inibição em 1000 ppm de antocianinas. Sob polarizações anódica e catódica, também foi verificado um melhoramento generalizado das propriedades anticorrosivas como potencial de corrosão, corrente de corrosão e eficiência de proteção contra a corrosão, para a concentração de 1000 ppm de antocianinas. Análises de microscopia eletrônica de varredura, microscopia de força atômica e espectroscopia por dispersão de energia, confirmam a adsorção de antocianinas na superfície da liga, assim como medidas de absorbância após 3 dias de imersão. / The efficiency of anthocyanins as corrosion inhibitor of the 2024-T3 aluminum alloy was evaluated by electrochemical measurements such as electrochemical impedance spectroscopy and anodic and cathodic polarizations. NaCl solutions 0.025 mol.L-1 containing different concentrations (800, 1000, 2000, 3000, 5000 and 7200 ppm) of anthocyanins extracted from grape were prepared to examine the effect of the presence of these substances when in contact with the 2024-T3 aluminum alloy. Electrochemical impedance spectroscopy measurements showed a decrease on the dispersion of points in the lower frequency regions with an increase of contact time of anthocyanins with the surface of the 2024-T3 aluminum alloy from 1 hour to 3 days of immersion. In addition, the inductive behavior in these regions decreased after 3 days of immersion with a considerable increase of the polarization resistance and inhibition efficiency of 1000 ppm of anthocyanins. Under cathodic and anodic polarizations, it was noted a general improvement in the anticorrosive properties such as corrosion potential, corrosion current and efficiency of protection against corrosion for the concentration of 1000 ppm of anthocyanins. Analyses of scanning electron microscopy, atomic force microscopy and energy dispersive spectroscopy confirm anthocyanins adsorption on to the surface alloy, as well as absorbance measurements in a spectrophotometer after 3 days of immersion.

Tato práce se zabývá problematikou nárůstku. Jde o řešení konkrétního průmyslového problému. Pro daný odlitek ze slitiny hliníku a řezný nástroj ze slinutého karbidu je studován výskyt nárůstku pro různé řezné podmínky. Nejprve se práce zabýva rozborem tématiky nárůstku, mechanismy jeho vzniku a parametry, které mají na jeho výskyt a růst největší vliv. Dále je věnována pozornost studiu materiálu odlitku, jeho nové koncepce a původního řešení. Během inovačního procesu došlo k obměně použitého materiálu. Tato změna se na procesu řezání projevila vznikem významného nárůstku, který vede až k úplné destrukci nástroje. Byly provedeny zkoušky tvrdosti a metalografické výbrusy pro detailní popis a srovnání vlastností obou slitin hliníku. Výsledky zkoušek prokazují rozdíly v metalografické struktuře (velikosti dendritů, množství precipitátů) a tvrdosti daných materiálů. Experimentální řešení problému spočívalo v testech vrtání do odlitků ze zkoušených slitin hliníku. Pro jednotlivé vrtací zkoušky byla měněna hodnota posuvu a řezné rychlosti. Za pomoci dynamometru byla měřena posuvová síla, dále byl použit wattmetr k určení příkonu stoje a synchroní funkce CN, jejichž výstupem byla aktuální poloha vřetene a řezný moment. Na zákldě naměřených hodnot byla vypočtena měrná řezná síla pro konkrétní testované řezné podmínky.Mimoto po každém pokusu byly pořízeny fotografie nástroje s daným nárůstkem. Z výsledků vyplývá, že měrná řezná síla má tendenci výrazně klesat se zvyšující se hodnotou posuvu, oproti tomu zvyšující se řezná rychlost nemá tak výrazný účinek na její snižování. Co se týče naměřené tloušťky nárůstku, tak se zvyšující se řeznou rychlostí dochází k jejímu poklesu. V případě růstu posuvu, má nárůstek taktéž tendenci klesat, ale menší měrou oproti předešlému případu. V závěru práce je uvedeno rozmezí řezných rychlostí a posuvů vymezující optimalizovanou zónu pro vrtání dané součásti. Následuje nabídka dalších možných experimentů vážících se k tématu studie.

A eficiência de antocianinas como inibidores de corrosão da liga de alumínio 2024-T3 foi avaliada através de medidas eletroquímicas como a espectroscopia de impedância eletroquímica e polarizações anódica e catódica. Soluções de NaCl 0,025 mol.L-1 contendo diferentes concentrações (800, 1000, 2000, 3000, 5000 e 7200 ppm) de antocianinas extraídas da uva foram preparadas para analisar o efeito da presença destas substâncias quando em contato com a liga de alumínio 2024-T3. Medidas de espectroscopia de impedância eletroquímica apresentaram uma diminuição sobre a dispersão dos pontos nas regiões de baixas frequências com o acréscimo do tempo de contato das antocianinas com a superfície da liga de alumínio 2024-T3 de 1 hora para 3 dias de imersão. Além disso, o comportamento indutivo nestas regiões decresceu após 3 dias de imersão com uma elevação considerável da resistência à polarização e da eficiência de inibição em 1000 ppm de antocianinas. Sob polarizações anódica e catódica, também foi verificado um melhoramento generalizado das propriedades anticorrosivas como potencial de corrosão, corrente de corrosão e eficiência de proteção contra a corrosão, para a concentração de 1000 ppm de antocianinas. Análises de microscopia eletrônica de varredura, microscopia de força atômica e espectroscopia por dispersão de energia, confirmam a adsorção de antocianinas na superfície da liga, assim como medidas de absorbância após 3 dias de imersão. / The efficiency of anthocyanins as corrosion inhibitor of the 2024-T3 aluminum alloy was evaluated by electrochemical measurements such as electrochemical impedance spectroscopy and anodic and cathodic polarizations. NaCl solutions 0.025 mol.L-1 containing different concentrations (800, 1000, 2000, 3000, 5000 and 7200 ppm) of anthocyanins extracted from grape were prepared to examine the effect of the presence of these substances when in contact with the 2024-T3 aluminum alloy. Electrochemical impedance spectroscopy measurements showed a decrease on the dispersion of points in the lower frequency regions with an increase of contact time of anthocyanins with the surface of the 2024-T3 aluminum alloy from 1 hour to 3 days of immersion. In addition, the inductive behavior in these regions decreased after 3 days of immersion with a considerable increase of the polarization resistance and inhibition efficiency of 1000 ppm of anthocyanins. Under cathodic and anodic polarizations, it was noted a general improvement in the anticorrosive properties such as corrosion potential, corrosion current and efficiency of protection against corrosion for the concentration of 1000 ppm of anthocyanins. Analyses of scanning electron microscopy, atomic force microscopy and energy dispersive spectroscopy confirm anthocyanins adsorption on to the surface alloy, as well as absorbance measurements in a spectrophotometer after 3 days of immersion.

Cette thèse s’inscrit dans le cadre d’un vaste programme visant à établir un premier retour d’expérience sur des structures aéronautiques en fin de vie. L’objectif des travaux présentés ici est donc de caractériser le vieillissement et les propriétés résiduelles de pièces provenant d’avions après démantèlement, et donc après service. Plus précisément, deux matériaux de nature différente sont considérés : un alliage d’aluminium 2024-T351, constitutif d’une voilure d’A320 ; et un composite carbone/époxy T300/914, prélevé sur les voilures d’un Falcon X et d’un ATR.Pour les voilures composites, les travaux ont porté sur les effets de l’eau des stratifiés. L’évolution de la température de transition vitreuse en DMA a été étudiée en fonction du taux d’humidité présente dans le stratifié. Les résultats d’essais de sorption set de désorption ont été confrontés à différents modèles de diffusion. Les propriétés résiduelles ont été évaluée au travers de divers essais mécaniques. Il ressort de cette étude un très bon comportement du composite après service.Les travaux concernant la voilure métallique se focalisent sur les propriétés résiduelles en fatigue de l’alliage de voilure. Les résultats montrent qu’un durcissement structural apparaît en service, et qu’un léger abattement de la durée de vie en fatigue est observable. Cependant, le comportement à la fissuration est inchangé en comparaison avec un matériau « neuf ».Au final, ce premier retour d’expérience est positif. Il peut maintenant permettre aux avionneurs de vérifier les règles utilisées lors de la conception ou d’optimiser certains dimensionnements, mais aussi de justifier des extensions de durée de vie des avions. / The thesis is part of a larger program aimed at establishing a first feedback on structural health of aeronautical structures at the end of life. The aim of the work presented here is to characterize the residual properties after aging of parts from aircraft after teardown, and therefore after service. Specifically, two different types of materials are considered: an aluminum alloy 2024 T351, constituting the underside of an A320 wing, and a composite carbon/epoxy T300/914, taken from the wing of a Falcon X and the wing of an ATR.Concerning the composite wings, the study focused on the effects of water on laminated composites. The evolution of the glass transition temperature by DMA has been studied as function of moisture present in the composite. The results of sorption and desorption tests were confronted to different diffusion models. Residual properties were evaluated through various mechanical tests. It is clear from this study a very good behavior of the composite after service.The work on the metal wing is focused on the residual fatigue properties of these alloys. The results show that hardening occurs in service, and a slight reduction of the fatigue life is observed, the number of cycles to failure ranging between 104 and 106. However, the fatigue crack growth resistance is unchanged in comparison with a “virgin” material.Finally, this initial feedback is positive: It can now enable manufacturers to check the design rules or to optimize the design, but also to justify aircraft life extensions.

The aluminium AA1050 alloy, known as commercially pure aluminium, contains 99.5% Al, together with Fe and Si as major alloying elements. During fabrication of aluminium substrates for lithographic printing plates in Bridgnorth Aluminium Ltd, the AA 1050 aluminium alloy proceeds through various stages of thermomechanical processing, with the conditions at each processing stage influencing the microstructure of the final coil. Because of its specific gravity, tensile strength, surface performance and coating adhesion behaviour, the AA 1050 aluminium alloy is one of the preferred materials for offset printing, which has been the dominant printing process for years. During manufacturing of the offset plate, the AA 1050 alloy is subjected to alkaline etching, electrograining and anodizing. Reactivity of the material to those chemical and electrochemical processes depends on various alloy properties, the thickness and composition of oxide film over the macroscopic alloy surface, cold work applied and the presence of second phase particles, which influence properties and quality of the final product.During the project, the main objectives were to understand the process in the production of the final product from slab to coil as well as to investigate some microstructural changes during the following stages of the production process and, finally, the performance behaviour of the final product.The set of experiments, including microstructural observation and electrochemical tests, has been developed to investigate the AA 1050 aluminium sheet in accordance with the objective of this study. Four homogenisation trials in the industry environment were performed to enable sample collection from the real production line; also, samples from each processing stage were examined with the special attention paid to those collected during the plant experimental homogenisation trials. It was found that the microstructure of the aluminium changed throughout the different production stages and influences the material response in the alkaline solution used for etching. Furthermore, the conditions of homogenisation (time and temperature) have impact on the properties like the electrochemical behaviour in alkaline and acid solutions, as well as the microstructure of the final aluminium sheet. Differentiation between the behaviour of final gauge samples was possible in terms of characterisation of the second phase particles characterisation (distribution and composition) present in the resultant alloy product.