La mise en œuvre des préimprégnés unidirectionnels à fibre de carbone et résine époxyde est une étape fondamentale pour la conception de pièces structurales aéronautiques. Elle influe directement sur la qualité de la pièce et notamment sur la quantité de défauts poreux qu’elle renferme. Ainsi, deux phénomènes de création de la porosité ont été identifiés expérimentalement : l’un mécanique, l’autre thermodynamique. Une fois créés, ces défauts peuvent être extraits hors de la pièce si le marouflage et le cycle de polymérisation favorisent cette évacuation gazeuse. Les effets sur la porosité de la température et de la pression imposées pendant la réticulation de la résine sont modélisés en prenant en compte les phénomènes thermo-diffuso-mécaniques entre la résine et la bulle de gaz. Un protocole expérimental reposant sur l’analyse d’image a été développé afin de quantifier le plus précisément possible le taux volumique de porosité, ainsi que leurs tailles et leurs localisations. / Long fiber reinforced epoxy matrix composite laminate manufacturing process is divided into several stages. The most critical one is the polymerization stage. If not optimized, defects in the bulk material such as voids can occur. The aim of this work is to investigate the void formation and evolution processes in order to improve the thermoset laminates quality in minimizing the void ratio. Two phenomena causing void formation have been identified. The first is the mechanical entrapment of gas bubbles between prepreg plies during the lay up. Second is a thermodynamical one. Solvents and humidity absorbed by the prepreg during its manufacturing can be evaporated by increasing the temperature. Then, it has been shown that the vaccum bag lay up permeability in combination with the vaccum pressure could favour the gas washing out. In parallel, thermo-mechanical and diffusion models are coupled to obtain an accurate void size prediction along temperature and pressure applied during the polymerisation. In fact, these two parameters induce variations of the gas bubble radius inside resin. The first experimental results seem to validate qualitatively the calculated void size behaviour. Indeed, hydrostatic pressure imposed during polymerization plays a very important role on gas bubble shrinkage. Finally, a new experimental setup using image analyses has been developed to measure as accurate as possible the volume void ratio. Under specific conditions, stereology allows to extrapolate 2D results to 3D ones. Void ratios obtained with this method are in good agreement with acid digestion results. Complementary morphometric studies on void shapes have given new information about the heterogeneous void distribution in the specimen and also on the statistical void size distribution versus polymerization conditions.

Zeolites were used in this study to remove two types of non-radioactive ions (Cobalt-59 and Strontium-89) from wastewater. This was designed to model the use of ion-exchange technique to remove radioactive Co-60 and Sr-90 from low level wastewater from Al-Tuwaitha site. Al-Tuwaitha site is a nuclear research in Iraq was used for radio-medical and radio-chemical purposes before 1990. In this study, hierarchical microporous/macroporous structures were developed to overcome the diffusivity problem using zeolite. Diatomite and carbon were used to prepare the composite adsorbents by incorporating them with three types of zeolites (A, Y and clinoptilolite). From the XRD, SEM and EDAX measurement it was confirmed that successfully prepared of Iraqi palm tree leafs-Clinoptlolite (IPClinp) and Tamarind stones-Clinoptilolite (TSClinp) composites were obtained in this study as there is no evidence in literature of this being carried out before. The carbons were prepared successfully through the Pyrolysis method for 2h at 900°C in an inert atmosphere from two types of raw waste plant materials of Iraqi Palm Tree leafs (IP) and Tamarind stones (TS). For both types of carbons, the SEM images show organised porosities in different shapes. A third material used as a zeolite scaffold was diatomite (Celatom FW-14) a readily available natural material (dead algae).A hydrothermal treatment was used to build the hierarchical structure of zeolite onto carbon and diatomite materials, the scaffolds were seeded with nano-zeolite crystals prior to the treatment and thereafter mixed with the zeolite gel composition mixture in a stainless steel autoclave. Zeolite seeds were prepared using ball mill method to reduce the particle size of the commercial zeolite to sub-micron range for each type of zeolite. The surface area, morphology, element compositions and structure for each type of zeolite and composite material were characterised using BET method, SEM, EDAX and XRD. The amounts of each type of zeolite on the carbon composites were determined using TGA while that of the diatomite composite was determined by gravimetric analysis. The results show that each type of zeolite was successfully deposited and uniformly organised onto the surface of all support materials. All pure zeolites and composite materials were successfully tested to remove Co2+ and Sr2+ ions from aqueous solutions. It was found that the composite materials had higher ability to remove both ions relative to the pure zeolites. This increase is attributed to the deposition of zeolite (microporous) onto the macroporous structure (carbon and diatomite) which increased the flow accessibility within zeolite in the hierarchical structured composites. Comparison of the removal between the two metal ions indicates that all of the materials had higher uptake for Sr2+ than Co2+ ions. The highest adsorption capacities were realised with Tamarind Stone–ZeoliteA (TSA) in the order 120mg.gz-1and 290mg.gz-1 for Co2+ and Sr2+ ions, respectively. The effect of the experimental variables shows increasing uptake with increasing pH and initial ion concentrations while it decreased with increasing the solution temperature. The Co2+ loaded composites was subjected to vitrification process at 12000C for 2h. The encapsulated composites were leached for 90 and 120 days and no significant Co2+ was recorded in the leached solution. The results show that the composite materials can be used effectively to remove the radioactive ion of Co-60 and Sr-90 ion as they display the same chemical behaviour as Co-59 and Sr-89 studied in this work.

No description available.

Les systèmes de communication à bord de certains navires ou véhicules terrestres peuvent être très nombreux. Il en résulte des architectures de systèmes rayonnants particulièrement élaborées. La compacité de ces systèmes et leur compatibilité radioélectrique représentent des enjeux importants. Dans le cadre du projet SAMCOM, les partenaires de projet s'attachent à exploiter l'avantage des parois porteuses en composite en termes d’intégration des antennes en paroi et de découplage électromagnétique entre éléments rayonnants. Cette thèse porte essentiellement sur deux volets. La première partie porte sur la question d'intégration des antennes en paroi. Il s'agit pour l'essentiel de s'assurer que les caractéristiques de fonctionnement intrinsèque de l'antenne associée à la paroi puissent être maintenues lorsque celle-ci est fixée sur une paroi composite. Le second volet de cette thèse concerne le découplage d'antennes associées à une même paroi composite. Il s'agit de rechercher les moyens qui permettraient d'augmenter les performances de découplage entre antennes et par conséquent de limiter l’espacement entre elles. Les solutions d'intégration examinées dans la thèse concernent la mise en oeuvre de matériaux de type ferrite, d’absorbants ou encore l’utilisation de surfaces haute impédance (SHI). Dans le premier cas, nous nous sommes attachés à optimiser la localisation de ferrites de sorte à minimiser leur volume pour des questions de coût et de poids. Les surface artificielles de type SHI ont été examinées et une procédure de dimensionnement adaptée à la paroi composite de la surface SHI a été élaborée. Nous abordons ensuite les solutions de découplage d'antennes hébergées sur une même paroi composite. La première solution de découplage étudiée concerne l'utilisation d'absorbants électromagnétiques. Nous montrons qu'il s'agit d'une solution très adaptée si nous disposons d’un absorbant dont le contraste d’impédance avec l’onde incidente est faible sur toute la bande de fréquence sous peine de subir les effets de bord. La deuxième solution envisagée concerne les surfaces à bande interdite électromagnétique (BIE). Nous montrons en particulier qu’une surface de type BIE peut présenter d’excellentes performances de découplage si toutefois cette surface est adaptée suivant sa hauteur. Une partie importante de ce travail a été consacrée à l'évaluation de solutions de découplages originales basées sur l'emploi d'une simple tige conductrice cylindrique puis d'un ensemble de tiges cylindriques. Nous montrons en particulier qu'une simple tige peut apporter un découplage significatif en bande étroite tandis qu'une forêt de tige contribue à assurer un découplage sur une plus large bande de fréquence. / Communication systems on board modern military ships or land vehicles can be numerous. This results in particularly developed radiating systems. The compacity of these systems and radio compatibility are major challenges. Under the Samcom project, the project partners are working to exploit the advantage of composite structural walls in terms of integration of antennas wall and electromagnetic decoupling between radiating elements. This thesis focuses on two parts. The first part consists in the study of integration of antennas on wall made up of composite materials. This is essentially to ensure that the operating characteristics of the antenna associated with the supporting structure can be maintained when it is fixed to a composite wall. The second part of this thesis is related to antenna decoupling mounted on the same ground plane. The aim is to find techniques to reduce antenna coupling and thus the separation between them. Integration solutions examined in the thesis concern the implementation of ferrite materials, absorbent and high impedance surfaces. In the first case, we attempted to optimize the location of ferrites so as to minimize their volume, thus saving cost and weight. Artificial higher impedance surface (HIS) have been examined and a design procedure adapted to the wall of the composite of the SHI surface has been developed. We then discuss on the solutions of antenna decoupling on a composite wall. The first decoupling solution investigated concerns the use of electromagnetic absorbers. We show that this is a very suitable solution if we have an absorbent whose impedance contrasts with that of the incidence wave is weak on full band frequency under penalty of sides effects. The second option concerns the surfaces electromagnetic bandgap. To ensure adequate decoupling performance, BIE surface must be adjusted in height. An important part of this work is dedicated to the assessment of some innovative decoupling solutions based on the use of a single cylindrical conducting rod. Indeed, we show on the one hand a single rod can lead to significant decoupling in a narrow band while on the other hand, a set of cylindrical rods contribute to ensure a rather broadband decoupling.

M.Sc. / The addition of lignocellulosic fibres to thermoplastic polymers is known to increase the toughness of the polymers but it compromises the tensile strength. On the other hand, inorganic fillers like TiO2 are known to improve the tensile strength of polymers. These plant fibres have been used as adsorbents of metal pollutants in water. Best results were obtained when such materials were ground to fine powder but due to low density, the fibres float and form aggregates in water. Being highly biodegradable in nature makes plant fibres unsuitable for water treatment over lengthy periods of time. They cannot be used as standalone materials. Mixing these adsorbents with polymers, which cannot only act as support for the adsorbents but also disperse the fibres within it thus preventing leaching, is a cause for concern. This study was aimed at fabricating plant fibre-polymer composites that will have improved mechanical and thermal properties. These composites were to be tested for their ability to be used as metal ion adsorbents. The composites were fabricated using a melt-mix compounding method. Two thermoplastic polymers, EVA and PCL were each mixed with either lignin or SCB and TiO2 in different ratios. A rheomex mixer coupled with a single screw extruder which was attached to a sheet die was used to synthesise the composites. TGA and DSC were used for thermal propagation while the mechanical properties were investigated using an instron. Metal ion adsorption measurements were analysed using an atomic absorption spectrometer (AAS). These adsorbents were used to remove Cr(VI), Cr(III) and Pb(II), varying different environmental parameters like pH, concentration, time and adsorbent at constant temperature. The reinforcing effect of both lignin and SCB resulted to poor thermal and mechanical properties. This was shown by a decrease in onset degradation temperature and the tensile and toughness of the composites compared to the neat polymers. The incorporation of TiO2 on SCB-EVA composites, however, improved the mechanical strength and resulted in a thermally stable composite compared to counterpart composites without TiO2. This observation was surpassed at high filler loading as the addition of TiO2 resulted in a decrease of the properties. For the tensile strength, neat EVA recorded 11.35 MPa while 2% TiO2-EVA registered 12.49 MPa for example. For the same composite, the onset degradation temperature for EVA was 353 oC but shifted to 368 oC after the addition of TiO2. At higher filler loading, no effect was observed when adding TiO2.

Ph.D. (Chemistry) / Phosphorus in the form of phosphate needs to be removed from the aqueous environment as it is primarily responsible for eutrophication of water bodies. In an attempt to limit the discharged of phosphorus into the aqueous environment, the phosphate discharge limits for wastewater treatment plants have been decreased. These limits are not easily or economically met by current phosphorus removal technologies. In addition phosphorus is a non-renewable resource. To ensure the ongoing quality of water bodies and security of food production it is vital that phosphate in water be removed and recovered. In order to address these issues, novel hybrid metal oxide ion exchange resins based on Fe(III), Cu(II), Mn(IV and Ti(IV) oxides have been prepared and their phosphate adsorption characteristics determined.

L’étude porte sur l’élaboration et la caractérisation des propriétés mécaniques de composites architecturés alumine / acier inoxydable 316L. Les matériaux obtenus sont doublement composites dans le sens où ils sont constitués d’un empilement de couches successives (architecture), chacune de ces strates étant elle-même un composite métal/céramique dispersé. Les différents aspects abordés concernent l'élaboration de monolithes composites dispersés par métallurgie des poudres, la détermination des propriétés mécaniques des architectures par mesure et simulation numérique, et la problématique de la réalisation de composites architecturés. L'observation des monolithes a mis en évidence un effet inhibiteur du carbone sur la densification de l'alumine lors du frittage. Des interactions complexes relient le carbone (issu d'un déliantage incomplet), l'acier (et sa microstructure) et le chrome, agissant sur la densité de ce type de matériau, et rendant l'élaboration délicate. Des lois de comportement ont pu être obtenues pour ces composites dispersés, par une approche double mêlant calculs d'homogénéisation (pour l'élasticité) et modèle analytique basé sur des mesures expérimentales (pour la plasticité). Ces lois ont permis la modélisation par éléments finis d'un choc plan à faible énergie sur différentes architectures composites en couches. La comparaison de ces résultats avec des essais expérimentaux a mis en évidence que la présence d'une architecture améliore la résistance au choc par rapport aux monolithes, ainsi que certains paramètres agissant sur la tenue au choc, comme l'épaisseur globale du matériau. / This study deals with forming and mechanical properties characterization of structured composites constituted from alumina and 316L stainless steel. Materials obtained can be considered twice composites, as they are made successive layers (structure), each one being a dispersed ceramic/metal composite by itself. The different aspects of this work cover monolithic dispersed composites elaboration through powder metallurgy, architectures mechanical properties determination through both measurements and numerical simulation, and problems linked to layered composites production. Experiments on monolithic composites have evidenced an inhibiting effect linked with carbon presence on alumina densification during sintering. Complex interactions happen between carbon (residues from imperfect debinding), steel (and microstructures thereof) and chromium, resulting in altered densification, which renders elaboration difficult. Mechanical behaviour laws could be obtained for these dispersed composites, using both behaviour homogenization (for plasticity) and analytic models based on experiments (for plasticity). These laws allowed finite elements modelisation of low energy plane versus plane impact tests for varying layered architectures. Comparison with experimental tests showed that layered structures increase impact resistance compared to monolithic composites, and allowed to determine some parameters, like parts thickness, susceptible to improve it. In spite of imperfect connexion between experimental data and numerical simulation, the latter is sufficient in order to optimize architecture choice.

Orientador: Mauro Augusto Demarzo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-14T15:26:19Z (GMT). No. of bitstreams: 1 Melo_FranciscaJuliaFrancaFerreirade_M.pdf: 10381131 bytes, checksum: cd6f132a8a110fdd0413f1ddfacae796 (MD5) Previous issue date: 2007 / Resumo: O presente trabalho se propõe desenvolver uma argamassa para nivelamento de contra piso modificada com partículas vegetais de Pinus caribaea e avaliar suas características físicas e mecânicas. Os resíduos de Pinus utilizados são provenientes do processo de fabricação de lápis. Os traços tiveram seu fator água/cimento determinado pela trabalhabilidade. As misturas foram elaboradas com Cimento Portland CPII-E 32, areia, adição de partículas vegetais de Pinus e água proporcional ao traço da mistura. Foram avaliadas a resistência à compressão, resistência à tração na flexão e absorção capilar da argamassa modificada com partícula vegetal no estado endurecido. / Abstract: The present work considers to develop a mortar for counter-floor levelling modified with vegetal particles of Pinus caribaea and to evaluate its physical and mechanical characteristics. The used residues of Pinus are proceeding from the process of manufacture of pencil. The traces had its factor water/cement determined by workability. The mixtures were elaborated with Cement Portland CPII-E 32, sand, addition of vegetal particles of pinus and proportional water to the trace of the mixture. It was evaluated the Compressive Strength, Tensile Strength in bending and Hair Absorption of the hard mortar modified with vegetal particle. / Mestrado / Arquitetura e Construção / Mestre em Engenharia Civil

L’industrie des matériaux composites ne cesse d’évoluer et de croître en mettant en place de nouveaux matériaux et de nouvelles technologies. En substitution des matériaux d’origine fossile que les matériaux d’origine naturelles (et surtout végétales) commencent à voir le jour. C’est dans ce contexte que notre travail de recherche est proposé. Il s’intéresse à la caractérisation du comportement mécanique d’un composite à matrice Polypropylène, renforcé avec des fibres de Chanvre et du bois de Chanvre (Chènevotte). Les différents moyens et techniques de caractérisation, utilisés par la présente étude, ont montré que ces nouveaux matériaux sont dotés de propriétés, en particulier mécaniques, de haut niveau, qui viennent rivaliser avec celles des autres composites classiques à base de fibres de verre et de carbone.Les essais expérimentaux en statique et de fatigue, ont révélé beaucoup de détails en comparaison avec d’autres matériaux composites. Ces informations ont permis de créer une sorte de base de données qui pourra servir de référence pour d’autres composites de la même famille à base de fibres végétales. Ainsi, des mécanismes d’endommagement ont été mis en évidence grâce aux essais mécaniques (traction monotone, charge-décharge, …) associés à des observations microscopiques (Microscope Electronique à Balayage), et à des outils de détection du dommage basés sur l’émission acoustique. Par le biais de cette technique, nous avons pu apprécier la qualité et l’importance de l’interface fibre/matrice qui est un paramètre fondamental pour la présente étude et pour la détermination de la loi de comportement du composite.La modélisation micromécanique a été intégrée dans ce travail de thèse, grâce au modèle de Mori-Tanaka. Le comportement des matériaux à l’endommagement n’a pas été pris en considération ; seule l’élasticité a été étudiée. A l’aide de ce modèle, nous avons pu remonter aux propriétés intrinsèques des constituants (le module d’élasticité longitudinale des renforts: Chanvre et Chènevotte). / The composites industry continues to evolve and grow by developing new materials and new technologies. Replacing fossil materials by materials with natural origin (especially vegetable) seems to be one of the most promising. In this context our research is proposed. It is interested to characterize the mechanical behavior of a polypropylene matrix composite reinforced with fibers of Hemp and Wood of Hemp (Chenevotte). The various means and characterization techniques used in this study showed that these new materials have interesting mechanical properties, coming rival those of other conventional composites based on carbon and glass fibers.The experimental static and fatigue tests have revealed many details in comparison with other composite materials. The information help creates a database that can serve as reference for other composites of the same family and vegetable fibers. Mechanisms of damage have been highlighted through mechanical tests (tensile monotonous charge-discharge …) associated with microscopic observations (Scanning Electron Microscope), and tools for damage detection based on emission acoustics. Thanks to this technique, we could improve the quality of the interface fiber / matrix which is a basic parameter for this study and for determining the behavior of composite.Micromechanical modeling has been integrated in this thesis, through the Mori-Tanaka model. The behavior of materials during damage has not been taken into account: only the elasticity has been studied. Using this model, we were able to trace the intrinsic properties of the constituents (the longitudinal modulus of elasticity of the reinforcements: Hemp and Chenevotte).

The effect of incorporation two clays; layered double hydroxides (LDH) and montmorillonite layered silicates (MLS) in linear low density polyethylene (PE) matrix was investigated. MLS and LDH were added of 5, 15, 30 and 60 weight percent in the PE and compounded using a Brabender. Ground pellets were subsequently compression molded. Dispersion of the clays was analyzed using optical microscopy, SEM and XRD. Both the layered clays were immiscible with the PE matrix and agglomerates formed with increased clay concentration. The thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Both clays served as nucleation enhancers increasing recrystallization temperatures in the composites. Flame retarding properties were determined by using the flammability HVUL-94 system. LDH indicated better flame retarding properties than MLS for PE. The char structure was analyzed by environmental scanning electron microscopy. Mechanical properties were studied by tensile testing and Vickers microhardness testing apparatus.