Submitted by Jesiel Ferreira Gomes (jesielgomes@ufcg.edu.br) on 2018-04-17T23:15:52Z No. of bitstreams: 1 FELIPE DE OLIVEIRA APOLINÁRIO – DISSERTAÇÃO (PPGEPM) 2016.pdf: 5151929 bytes, checksum: f4706d54cb97c9b01a64299ddb28cd7d (MD5) / Made available in DSpace on 2018-04-17T23:15:52Z (GMT). No. of bitstreams: 1 FELIPE DE OLIVEIRA APOLINÁRIO – DISSERTAÇÃO (PPGEPM) 2016.pdf: 5151929 bytes, checksum: f4706d54cb97c9b01a64299ddb28cd7d (MD5) Previous issue date: 2016-09-06 / Capes / O presente trabalho teve como objetivo analisar a influência da saturação fluida nas propriedades elásticas de rochas carbonáticas, bem como a eficácia dos modelos de substituição de fluidos e de simulação computacional. Foram estudadas 9 amostras de rochas carbonáticas, sendo dois calcários laminados e sete tufas. As medições de velocidade foram realizadas em amostras secas, saturadas com água ou com óleo, sob diferentes pressões efetivas. A simulação de propagação de ondas foi feita no COMSOL Multiphysics 5.1, utilizando o Avizo Fire 8.1 para a criação das amostras digitais. Análise por difração de raios X (DRX) foi realizada para determinar a composição das amostras de rocha. Os resultados obtidos nos ensaios laboratoriais e nas simulações computacionais foram comparados com as estimativas dos modelos de substituição de fluidosGassmann, Biot e Brown & Korringa. Foi observado que a saturação das amostras com agua ou óleo geraram aumentos nas velocidades de propagação de onda P, porém sem apresentar um comportamento padrão. Para o caso das ondas S, a saturação por óleo predominantemente gerou aumentos nas velocidades, com exceção para os casos em que as amostras possuíam porosidade secundária do tipo vugular, devido à pouca influência que o óleo oferece para o módulo de cisalhamento nestes casos. A saturação por água resultou em diminuições das velocidades de propagação de onda S devido ao aumento da densidade total. Também foi constatado que o modelo de Gassmann foi o mais efetivo na estimativa de velocidades de onda P e S, enquanto que o de Biot mostrou-se eficaz apenas para a estimativa de velocidades de ondas S, sendo ineficiente para a estimativa de velocidades de ondas P, com erros de até 20%. A simulação computacional gerou resultados superdimensionados, porém que evidenciam que um aperfeiçoamento da metodologia, tal como o aumento do número de pontos de leitura pode gerar resultados mais próximos dos obtidos laboratorialmente e de maior confiabilidade. / This research aimed to analyze the influence of the saturating fluid in carbonate rocks, as well as verify the effectiveness of the fluid substitution models and computational simulations of wave propagation. To do so, nine carbonate rock samples were analyzed, which two of them were laminated limestones and seven were carbonate tufas. The measurement of velocities were made in dry, water saturated and oil saturated samples, under different effective pressures. The wave propagation simulations were made in COMSOL Multiphysics 5.1 using Avizo Fire 8.1 to generate the digital rock samples. The results obtained in lab procedures and in computer simulations were compared with the estimated velocities of the fluid substitution models of Gassmann, Biot and Brown & Korringa. It was observed that the saturation of the samples with water or oil resulted in an increasing of P-wave velocities, however without a pattern. The saturation with oil resulted in most cases in an increasing of S-wave velocities, the exceptions occurred in samples which had vugular porosity, due to the small influence of the oil in the shear modulus in this cases. T he saturation with water resulted in a decreasing of S-wave velocities due to the increment of the bulk density. It was found that the Gassmann’s model was more effective than the other two models in estimating P-wave and S-wave velocities. Biot’s model generated unsatisfying results to P-wave velocities, with errors up to 20%. However, this model had a good accuracy in estimating S-wave velocities. The computer simulations produced mainly overestimated results, though it was shown that an optimization of methodology, such as and addition in the number of the measure points, could improve the quality of the data, providing more representative results.

Le mécanisme d'endommagement le plus facilement observable lors d'un essai de traction est la micro-fissuration des plis. Ces fissures sont parallèles à la direction des fibres et s'étendent sur toute l'épaisseur du pli. L'apparition et la croissance du nombre de ces fissures engendrent une réduction progressive de la rigidité globale du composite. Lorsque le composite est sollicité mécaniquement, les concentrations de contraintes en pointe de fissures peuvent favoriser la création d'une zone où le pli fissuré et le pli adjacent sont décollés (phénomène de délamination). Il est évident que l'apparition de cette nouvelle forme d'endommagement modifiera la dépendance de l'ouverture et du glissement des lèvres des fissures avec le chargement appliqué. Il est donc nécessaire de trouver un moyen de mesure permettant l'estimation expérimentale des valeurs de l'ouverture moyenne et du glissement moyen des lèvres des fissures. L'objectif principal de cette thèse est de caractériser l'endommagement des matériaux composites (Fibre de carbone/époxy et fibre de verre/époxy) utilisés dans le domaine aéronautique. En utilisant l'interférométrie de speckle (ESPI), des mesures de plein champs de déplacements aux bords des échantillons et dans différentes couches du stratifié ainsi que des études par élément finis ont été effectuées dans le but de calculer l'ouverture et le glissement des lèvres des fissures. L'effet des propriétés élastiques des matériaux sur l'endommagement aussi bien que l'effet d'interaction entre les fissures ont été déterminés. Une discussion essais/calculs est enfin réalisée afin de juger la validité des hypothèses retenues / The macroscopic failure of composite laminates subjected to tensile increasing load is preceded by initiation and evolution of several microdamage modes. The most common damage mode and the one examined in this thesis is intralaminar cracking in layers. Due to this kind of microdamage the laminate undergoes stiffness reduction when loaded in tension. The degradation of the elastic properties of these materials is caused by reduced stress in the damaged layer which is mainly due to two parameters: crack opening displacement (COD) and crack sliding displacement (CSD). The first objective of this thesis is to investigate the effect of crack interaction on COD using FEM and to describe the identified dependence on crack density in a simple and accurate form by introducing an interaction function dependent on crack density. The application of this function to more complex laminate lay-ups is demonstrated. All these calculations are performed assuming that cracks are equidistant. Using FEM, we assume linear elastic material with ideal crack geometry. Fiber bridging over the crack surface is possible which can affect COD and CSD. The only correct way to validate these assumptions is through experiments. The second objective is to measure these parameters for different laminate lay-ups in this way providing models with valuable information for validation of used assumptions and for defining limits of their application. In particular, the displacement field on the edge of a [90/0]s and [903/0]s carbon fiber/epoxy laminates specimens with multiple intralaminar cracks in the surface layer is studied

Le comportement mécanique de films minces métalliques déposés sur des substrats souples joue un rôle déterminant dans les performances de l'électronique flexible et des micro- systèmes électromécaniques (MEMS).Dans un premier temps, une nouvelle méthode est présentée pour caractériser le module d'élasticité de films minces submicroniques. Avec deux couches déposées de chaque côté et sur la moitié du substrat polymère, la corrélation d'image numérique (CIN) a été utilisée pour mesurer simultanément la déformation du film et du substrat in situ au cours d'un essai de traction. La différence entre les déformations mesurées sur la partie vierge et le composite permet d'extraire les propriétés élastiques de films minces de manière simple et avec grande précision. Comme attendu, la distribution des déformations est uniforme au travers de l'épaisseur du film ce qui indique une adhésion parfaite entre le film et le substrat. Dans le cas de films minces de tungstène, de chrome, de nickel et de cuivre, les valeurs de module obtenues sont proches de celles des mêmes matériaux à l'état massif.Dans un deuxième temps, une nouvelle méthode expérimentale utilisant une machine de déformation uniaxiale est présentée pour étudier l'effet Bauschinger dans des films minces métalliques déposés sur des substrats étirables. Grâce à un dispositif original, les films minces sont déposés sur des substrats prétendus et peuvent donc être déformés alternativement en tension et en compression dans un large domaine de déformations. La déformation élastique intra granulaire des films minces polycristallins et la déformation macroscopique du substrat sont mesurées in situ par diffraction des rayons X et CIN respectivement. A partir des courbes « déformation élastique – déformation macroscopique », la réponse mécanique de l'ensemble film / substrat est analysée au vu de l'histoire complète du chargement et de la microstructure (contraintes résiduelles, texture) des films minces. / The mechanical behavior of metallic thin films deposited on soft substrates plays a crucial role in the performance of flexible electronics and MicroElectroMechanical Systems (MEMS).At first, a novel method is presented to characterize the in-plane elastic modulus of sub micrometer thin films. With two coating layers bonded symmetrically to half polyimide substrates, Digital Image Correlation (DIC) has been employed to measure time-resolved full-field strain maps of film and substrate during in situ tensile testing. The strain differences between virgin and composite parts allowed to extract the elastic properties of the thin films in a simple way with high precision. As expected, the strain distribution is uniform through the film thickness which indicates a perfect adhesion between the film and the substrate. In the case of tungsten, chromium, nickel and copper films, the values obtained are close to the bulk one.In a second step, a new experimental method using uniaxial tensile testing is presented to study Bauschinger effect in thin metallic films deposited on stretchable substrates. Thanks to our new pre-tensile setup (specific grips), the thin films were deposited on pre-stretched substrates and thus could be deformed alternately in tension and compression within a large strain domain. The elastic intra-granular strain of polycrystalline thin films and true strain of substrates are measured in situ by X-Ray Diffraction (XRD) and DIC. From lattice strain-true strain curves, the mechanical response of copper and nickel /substrate sets is analyzed in view of the complete loading history and the presence of residual stresses and crystallographic texture in thin films.

Knochen und Muskel sind die wichtigsten Gewebe im muskuloskelettalen System welche dem Körper die Bewegungen möglich machen. Beide Gewebetypen sind hochgradig strukturierter Extrazellulärmatrix zugrundegelegt, welche die mechanischen und biologischen Funktionen bestimmen. In dieser Studie wurden die räumliche Verteilung der anisotropen elastischen Eigenschaften und der Gewebemineralisation im humanen kortikalen Femur untersucht mit akustischer Mikroskopie und Synchrotron-µCT. Die homogenisierten elastischen Eigenschaften wurden aus einer Kombination der Porosität und der Gewebeelastizitätsmatrix mit Hilfe eines asymptotischen Homogenisierungsmodells ermittelt. Der Einfluss der Gewebemineralisierung und der Strukturparameter auf die mikroskopischen und mesoskopischen elastischen Koeffizienten wurde unter Berücksichtigung der anatomischen Position des Femurschaftes untersucht. Es wurde ein Modell entwickelt, mit welchem der intramuskuläre Fettgehalt des porcinen musculus longissimus nichtinvasiv mittels quantitativem Ultraschall und dessen spektraler Analyze des Echosignals bestimmt werden kann. Muskelspezifische Parameter wie Dämpfung, spectral slope, midband fit, apparent integrated backscatter und cepstrale Paramter wurden aus den RF-Signalen extrahiert. Die Einflüsse der Muskelkomposition und Strukturparameter auf die spektralen Ultraschallparameter wurden untersucht. Die akustischer Parameter werden durch die Muskelfaserorientierung beeinflusst und weisen höhere Werte parallel zur Faserlängsrichtung als senkrecht zur Faserorientierung auf. Die in dieser Studie gewonnenen detaillierten und lokal bestimmten Knochendaten können möglicherweise als Eingabeparameter für numerische 3D FE-Simulationen. Darüber hinaus kann die Untersuchung von Veränderungen der lokalen Gewebeanisotropie neue Einsichten in Studien über Knochenumbildung geben. Diese auf Gewebeebene bestimmten Daten von Muskelgewebe können in numerischen Simulationen von akustischer Rückstreuung genutzt werden um diagnostische Methoden und Geräte zu verbessern. / Bone and muscle are the most important tissues in the musculoskeletal system that gives the ability to move the body. Both tissues have the highly oriented underlying extracellular matrix structure for performing mechanical and biological functions. In this study, the spatial distribution of anisotropic elastic properties and tissue mineralization within a human femoral cortical bone shaft were investigated using scanning acoustic microscopy and synchrotron radiation µCT. The homogenized meoscopic elastic properties were determined by a combination of porosity and tissue elastic matrix using a asymptotic homogenization model. The impact on tissue mineralization and structural parameters of the microscopic and mesocopic elastic coefficients was analyzed with respect to the anatomical location of the femoral shaft. A model was developed to estimate intramuscular fat of porcine musculus longissimus non-invasively using a quantitative ultrasonic device by spectral analysis of ultrasonic echo signals. Muscle specific acoustic parameters, i.e. attenuation, spectral slope, midband fit, apparent integrated backscatter, and cepstral parameters were extracted from the measured RF echoes. The impact of muscle composition and structural properties on ultrasonic spectral parameters was analyzed. The ultrasound propagating parameters were affected by the muscle fiber orientation. The most dominant direction dependency was found for the attenuation. The detailed locally assessed bone data in this study may serve as a real-life input for numerical 3D FE simulation models. Moreover, the assessment of changes of local tissue anisotropy may provide new insights into the bone remodelling studies. The data provided at tissue level and investigated ultrasound backscattering from muscle tissue, can be used in numerical simulation FE models for acoustical backscattering from muscle for the further improvement of diagnostic methods and equipment.

This thesis primarily focused on the development of novel composite tubes by braiding. The objective was to use hierarchical scale technique, i.e., micro, meso and macro scales, with the transfer of information from one scale to another to develop novel braided composite tubes. This research was conducted and reported in three journal papers. The aim of the first paper was to predict plane elastic properties for E-glass/epoxy braided composite structures at different braid orientations, by analytical and finite element techniques. The lenticular shape has been used to describe the geometry of the tow. Modified lenticular geometric model was developed to improve an existing geometric model, in terms of tow parameters, thereafter, plane elastic properties from Chamis micromechanical model for E-glass fibre and epoxy matrix without any knockdown effects were used as benchmark to develop predictive models, namely; Lekhnitskii's methodology and braided unit cell meso-scale finite element model to account for the effects of tow geometry, undulations/crimp, cross-over and braid orientations on the plane elastic properties of E-glass/epoxy composite. The results showed agreement in trend between the predictive models, Chamis micromechanical model, and a similar existing model. However, the plane elastic properties were knocked down in predictive models by 30% in the E11 direction and 32% in the E22 direction, when compared with Chamis micro-mechanical model for largest ±65° braid angle, among the braid angles, considered. The aim of the second paper was to manufacture E-glass/epoxy braided tubes at different braid orientations by vacuum bag infusion technique, conduct internal pressure tests, and determine the hoop and axial moduli of the infused tubes. Lekhnitskii's methodology was also used to develop plane elastic moduli by experiment using microscopy results, and by calculation. The experimental elastic moduli of the infused tubes and the experimental elastic moduli from Lekhnitskii's methodology were used to compare the predictive elastic moduli for E-glass/epoxy braided structures by Chamis micro-mechanical model, and the braided unit cell meso-scale finite element model. The two were from another paper. Results showed a perfect agreement in trend between the experimental results and the predictive results. However, the values of the experimental results were close but lower than the predicted results. Optical microscopy was performed on braided tube cross-section to evaluate the level of crimp or undulation. This was done by the determination of tow centreline crimp angle and aspect ratio. Results show that when compared with the predicted crimp, there was an agreement in trend, although the experimental results were lower than the predicted. Also, the knockdown factor was evaluated and used to quantify the reduction in experimental elastic moduli when compared with the predicted. Results showed that the absences of crimp in the Chamis model caused a tremendous difference between it, other predicted models and the experiment results. The elastic moduli of Chamis were by far higher than all others, including other predictive models. The purpose of the third paper was to manufacture E-glass/epoxy braided tube at ±31°, ±45°, ±55°, ±65° braid orientations using vacuum bagging and resin infusion technique, to design and manufacture a rig for tube internal pressures experiment, to determine the hoop and axial stress performances of the tubes by internal pressure experiment, to compare experimental results with laminate analysis predictions to evaluate the effect of crimp on the internal pressure performance of the braided tubes. To use E-glass braided tow meso-scale unit cell finite element model to predict the tow critical stresses, and the optimum braided tube architecture, using tube hoop and axial failure stresses or strains. The tubes were manufactured and subjected to internal pressure test (2:1), to failure. Failure mode was by weeping and bursting. Hoop stress was twice the axial stress. The highest value of hoop stress was at the ±65° braid angle, higher than the hoop stresses at the ±31°, ±45°, and ±55 ° braid angles by 50%, 39%, and 28% respectively. Hoop stress increased with increase in braid angle. The experimental results were validated by laminate analysis predictions by Chamis micro-mechanical model and Lekhnitskii's methodology, and the trend of the laminate analysis prediction matched that of the experimental results. However, the predicted values were higher than the experimental results by 21%, 14%, 11%, 10% for the ±31°, ±45°, ±55°, ±65° braid angles for the Chamis micro-mechanical model and 5%, 7%, 7%, 5% for the ±31°, ±45°, ±55°, ±65 braid angles respectively for the Lekhnitskii's model, showing the severe effect of crimp in the experimental tube, mostly when compared with Chamis micro-mechanical model. Braided tow unit cell finite element model prediction, showed that tow axial stresses increased with increase in braid angle, while the tow transverse stresses decreased with increase in braid angle. The predictions showed that the tow critical stresses and the tube optimum braided architecture lie between the ±65° and 90° braid angles. The tow critical stresses are the stresses at which the tow decreasing transverse stress and the tow increasing axial stress causes the tube to fail.

Ces travaux de thèse portent sur la détermination des propriétés mécaniques à différentes échelles ainsi que les mécanismes d'endommagement des nitrures de silicium denses ou avec différents taux de porosités. Ces céramiques techniques présentent des propriétés mécaniques forte intéressantes : une faible densité, une dureté élevée, une bonne résistance à la corrosion et un faible coefficient de dilatation thermique. Elles sont notamment utilisées dans la fabrication des billes de roulement pour des applications dans les industries automobiles et aéronautiques. La caractérisation du comportement local sous un chargement de contact est donc un enjeu majeur. Les matériaux étudiés ont été obtenus par frittage flash d'une poudre de Nitrure de Silicium avec différents pourcentages d'oxide d'yttrium comme additif. Le contrôle de la température et de la pression de frittage a permis d'obtenir des matériaux denses avec différentes tailles de grain mais aussi avec une porosité résiduelle variable. La première partie de ce travail consistait à caractériser l'influence des conditions d'élaboration (température, pression, pourcentage d'additif) sur la microstructure (taille des grains, compositions ...) et les propriétés mécaniques à l'échelle macroscopique (module élastique, dureté Vickers, résistance à la flexion ...) des matériaux frittés. Des essais de contact de Hertz ont été ensuite réalisés afin d'identifier les mécanismes d'endommagement. L'utilisation de sphères de différents rayons a mis en évidence un important effet d'échelle : des fissures circonférentielles à échelle macroscopique (mode fragile) et des déformations plastique localisées à l'échelle mesoscopique avec des micro fissures distribuées aléatoirement (mode quasi-ductile). Les tests de nanoindentation permettent de solliciter localement les échantillons pour obtenir les propriétés élastiques des courbes force-déplacement. Des méthodes d'identification inverses permettent aussi d'extraire les paramètres d'écoulement. Le comportement non linéaire des céramiques a été modélisé en utilisant une loi bilinéaire où Sy est la limite d'élasticité et K un paramètre d'écrouissage. Afin d'identifier ces deux paramètres, un modèle éléments finis axisymétrique avec une pointe sphérique déformable a été construit sous Abaqus. Le modèle a été couplé à un module d'identification inverse fondé sur l'algorithme de Levemberg-Marquart pour minimiser l'écart (au sens des moindres carrés) entre les courbes expérimentales et numériques. Les simulations avec le code Isaac développé au sein du laboratoire LaMCoS ont permis de suivre d'évolution de la zone plastique lors d'un chargement de roulement. / This work deals with the mechanical properties and damage mechanisms under contact loading of dense and porous silicon nitrides materials. These technical ceramics exhibit a very interesting combination of mechanical properties: low density, high hardness and strength, good corrosion resistance and a low thermal coefficient. They are used in many applications including ball bearings for the automotive and aerospace industries. The characterization of the local behaviour under contact loading is then a crucial issue. Spark plasma sintering technique is used to process silicon nitride ceramics with addition of different amount of yttrium oxide as sintering aid. Controlling the sintering temperature and the applied pressure has permitted to obtain materials with fine, medium and coarse microstructures. In addition, materials with different porosity contents have been obtained. First, we have investigated the influence of processing conditions (temperature, pressure, amount of yttria on the microstructure and mechanical properties at the macroscopic scale (elastic parameters, Vickers hardness, flexural resistance ...). Hertzian contact tests were then performed to identify the damage mechanisms at the surface and subsurface of the sintered materials. The use of indenting spheres of different radii permitted to observe a significant size effect. Brittle mode consisting of surface ring cracks were observed at large scale (macroscopic scale) while localized plastic deformation with microcracks randomly distributed was observed at small scale (mesoscopic scale). Transmission electron microscopy observations of thin foils machined by ion milling were performed to investigate the subsurface damage. Numerical simulations with a code developed internally in LaMCoS laboratory enabled to follow the evolution of the plastic zone under pure rolling conditions. In these simulations, the nonlinear behaviour of ceramics was modelled using a bilinear law where Sy is the yield stress and K a hardening parameter of the ceramic specimen. Instrumented indentation tests were performed using a diamond spherical tip of radius 42 µm. Experimental load versus displacement curves were used as input data for an inverse identification purpose. Levemberg-Marquart algorithm was used to minimize the gap in the least squares sense.

Rammed earth is a technique of forming in-situ structural wall elements using rigid formwork. Advantages of rammed earth walls include flexibility in plan form, scope for adjusting strength and wall thickness, variety of textural finishes, lower embodied carbon and energy, etc. There is a growing interest in the construction of rammed earth buildings in the recent past. Well focused comprehensive studies in understanding the structural performance of rammed earth structures are scanty. Clear-cut guidelines on selecting soil grading and soil characteristics, assessing strength of rammed earth walls, density strength relationships, limits on shrinkage, standardised testing procedures, behaviour of rammed earth walls under in-plane and out of plane loads, etc are the areas needing attention. The thesis attempts to address some of these aspects of cement stabilized rammed earth for structural walls. Brief history and developments in rammed earth construction with illustrations of rammed earth buildings are presented. A review of the literature on rammed earth has been provided under two categories: (a) Unstabilised or pure rammed earth and (b) stabilised rammed earth. Review of the existing codes of practice on rammed earth has also been included. Summary of the literature on rammed earth along with points requiring attention for further R&D are discussed. Objectives and scope of the thesis are listed. The thesis deals with an extensive experimentation on cement stabilised rammed earth (CSRE) specimens and walls. Four varieties of specimens (cylindrical, prisms, wallettes and full scale walls) were used in the experiments. A natural soil and its reconstituted variants were used in the experimental work. Details of the experimental programme, characteristics of raw materials used in the experimental investigations, methods of preparing different types of specimens and their testing procedures are discussed in detail. Influence of soil grading, cement content, moulding water content, density and delayed compaction on compaction characteristics and strength of cement stabilised soil mixes were examined. Five different soil gradings with clay content ranging between 9 and 31.6% and three cement contents (5%, 8% and 12%) were considered. Effect of delayed compaction (time lag) on compaction characteristics and compressive strength of cement stabilised soils was examined by monitoring the results up to 10 hours of time lag. Influence of moulding water content and density on compressive strength and water absorption of cement stabilised soils was examined considering for a range of densities and water contents. The results indicate that (a) there is a considerable difference between dry and wet compressive strength of CSRE prisms, and the strength decreases as the moisture content at the time of testing increases, (b) wet strength is less than that of dry strength and the ratio between wet to dry strength depends upon the clay fraction of soil mix and cement content, (c) saturated moisture content depends upon the cement content and the clay content of the soil mix, (d) optimum clay percentage yielding maximum compressive strength is about 16%, (e) compressive strength of compacted cement stabilised soil increases with increase in density irrespective of cement content and moulding moisture content, and the strength increases by 300% for 20% increase in density from 15.70 kN/m3, (f) compressive strength of rammed earth is one - third higher than that of rammed earth brick masonry and (g) density decreases with increase in time lag and there is 50% decrease in strength with 10 hour time lag. Stress-strain relationships and elastic properties of cement stabilised rammed earth are essential for the analysis of CSRE structural elements and understanding the structural behaviour of CSRE walls. Influence of soil composition, density, cement content and moisture on stress-strain relationships of CSRE was studied. Three different densities (15.7 – 19.62 kN/m3) and three cement percentages (5%, 8% and 12% by weight) were considered for CSRE. Stress-strain characteristics of CSRE and rammed earth brick masonry were compared. The results reveal that (a) in dry condition the post peak response shows considerable deformation (strain hardening type behaviour) beyond the peak stress and ultimate strain values at failure (dry state) are as high as 3.5%, which is unusual for brittle materials, (b) modulus for CSRE increases with increase in density as well as cement content and there is 1 to 3 times increase as the cement content changes from 5% to 12%. Similarly the modulus increases by 2.5 to 5 times as the dry density increases from 15.7 to 19.62 kN/m3 and (c) the modulus of CSRE and masonry in dry state are nearly equal, whereas in wet state masonry has 20% less modulus. Compressive strength and behavior of storey height CSRE walls subjected to concentric compression was studied. The results of the wall strength were compared with those of wallette and prism strengths. The wall strength decreases with increase in slenderness ratio. There is nearly 30% reduction in strength as the height to thickness ratio increases from 4.65 to 19.74. It was attempted to calculate the ultimate compressive strength of CSRE walls using the tangent modulus theory. At higher slenderness ratios, there is a close agreement between the experimental and predicted values. The storey height walls show lateral deflections as the load approaches failure. The walls did not show visible buckling and the shear failure patterns indicate material failure. The shear failures noticed in the storey height walls resemble the shear failures of short height wallette specimens. The thesis ends with a summary of the results with concluding remarks in the last chapter.

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Объектом исследования являются 3 образца нанокерамики на основе Al2O3, и 4 образца кварцевых стекол: КИ, КВ, КУ, КС-4В. Цель данной работы – исследование акустических свойств, обусловленных особенностями микро- (нано)структуры двух категорий материалов микро- и оптоэлектроники – нанокерамики на основе Al2O3 и оптических кварцевых стекол. В процессе работы были: исследованы акустические свойства материалов микро- (нанокерамика на основе Al2O3) и оптоэлектроники (кварцевые стекла), исследованы оптические параметры кварцевых стекол и установлена корреляция между акустическими и оптическими параметрами. В результате исследования был создан оригинальный измерительный стенд и разработана методика измерения значений скоростей поперечных ультразвуковых волн, определены упругие характеристики нанокерамики на основе Al2O3 и кварцевых стекол, а также оптические параметры стекол. В данной работе удалось установить корреляцию между акустическими и оптическими параметрами. Используя измерения скоростей ультразвука и оптического поглощения, были определены фундаментальные характеристики образцов. Это способствует пониманию структурно-чувствительных свойств, а значит, в дальнейшем и влиять на них, создавая материалы с нужными параметрами для лучшей работы приборов микро- и оптоэлектроники. / Objects of research are 3 samples of nanoceramiсs based on Al2O3 and 4 samples of quartz glasses: KI, KU, KV, KS-4V. The aim of this work is the study of the acoustic properties due to the peculiarities of micro- (nano)structures of the two categories of micro- and optoelectronics materials: nanoceramics based on Al2O3 and optical quartz glass. The acoustic properties of materials micro- (nanoceramics based on Al2O3) and optoelectronics (quartz glass) were studied, the optical parameters of quartz glass were investigated, and a correlation between acoustic and optical parameters was found. The original test stand and the method of measuring the transverse ultrasonic waves velocities were created, the elastic characteristics of nanoceramics based on Al2O3 and optical quartz glass and the optical parameters of glass were determine. In this paper we determined a correlation between acoustic and optical parameters. Using measurements of the velocity of ultrasound and optical absorption fundamental characteristics of the samples were determined. This contributes to an understanding of structure-sensitive properties that will help create materials with the necessary parameters for the best performance of micro- and optoelectronics.

Dans cette étude, les propriétés mécanique et la microstructure du polyéthylène à haute densité (PEHD)/ fibres de bois (Pinmaritime) ont été caractérisés. Le comportement en traction et en flexion 4 points de composites fibres de bois/polyéthylène(WPC) avec et sans additif a été étudié en utilisant des mesures de champs par stéréo-corrélation d’image numériques. Nousavons tout d’abord comparé les mesures de déformation longitudinale par stéréo-corrélation d’image à celles mesurées parextensométrie mécanique au cours d’un essai de traction simple uni-axial. Les valeurs de déformation macroscopiquemesurées sont comparables à celles obtenues par extensométrie mécanique classique. Quatre formulations ont été testées(avec ou sans l'additif et avec 10% ou 30% de bois) au travers des essais de traction et flexion 4 points en utilisant laméthode par stéréo-corrélation d’image. Nous avons pu ainsi corréler la visualisation combinée des images enregistrées parles caméras au comportement mécanique ainsi qu’aux modifications des surfaces des composites. Les résultats ont montréque les singularités au niveau de la surface des échantillons ainsi que la présence des fibres de bois (dans les proportionsutilisées durant nos essais) n’ont pas d’effets sur la qualité du composite. La stéréo corrélation d’images nous permet d’avoirune information précise sur le cisaillement tant d’un point de vue quantitatif que qualitatif. L’essai cyclique a été utilisé pouranalyser l’endommagement du composite. Les courbes en traction et flexion ont montré un comportement global non linéaire. Le module d’élasticité (MOE) est évalué par la tangente à l’origine d’un modèle de Maxwell-Binhgam ajusté paroptimisation sur les courbes expérimentales. Les cartographies fausses couleurs du champ de déformation du WPC ont étéprésentées. D’autre part, on a analysé le comportement endommageable et le degré d’hétérogénéité pour différentspourcentages de bois à l’aide des valeurs de l’écart type spatial du champ de déformation longitudinale. Par cette technique,nous avons également pu étudier les propriétés mécaniques en traction et en compression à partir d’un essai de flexion 4points. Le second objectif était d’améliorer la performance des liaisons entre les fibres de bois hydrophiles polaires et lamatrice plastique de PEHD hydrophobe non polaire. Pour cette raison, la fibre de bois a été traitée par anhydride maléique depolyéthylène (MAPE) (greffage par copolymérisation) et acétylée (greffage de chaine de carbone). Dans cette partie, nousavons étudié l’effet de MAPE ainsi que la longueur de la chaine de carbone greffée sur les propriétés mécaniques du WPC.Par ailleurs, nous avons pu observer et caractériser la morphologie à l’interface fibre de bois/HDPE du WPC greffé enutilisant un microscope électronique à balayage (MEB). / Firstly we have compared longitudinal strenght obtained by stereo correlation with mechanical extensometer forthe same tests. It is shown that macroscopic values of the longitudinal strain are closed to those measured bymechanical extensometers using standard mechanical tests. Four injected WPC formulations (with or withoutadditive and with 10% or 30% of wood) are consider. WPC surface particularities and wood fibers distributionon samples have no effect on WPC mechanical performances. Also 3D digital image correlation givesinformations on Tensile performances (from quality and quantity point of view). Cyclic tensile tests have beenperformed in order to analyse the damage of material. A non-linear behaviour is shown. The Modulus ofElasticity (MOE) is provided by a Maxwell-Bingham model fitted to the experimental tensile curves. Color mapsof the spatial strain distribution are commented. Moreover, the damage behaviour and the degree ofheterogeneity for several percentages of fibre wood-based WPC are analysed thanks to the spatial standarddeviation of the longitudinal strain field. With this technology it was possible to study of the mechanicalproperties in tensile and compression during four bending test. The second objective was to improve the linkbetween PEHD matrix and wood fibres because of the incompatibility between the polar hydrophilic wood fibresand the non-polar hydrophobic polyethylene. For this reason, the wood fibre was treated by maleic polyethyleneanhydride (MAPE) (grafting by copolymerization) and was acetylated (grafting of carbon chain). In this part, theeffect on the mechanical properties, of maleic anhydride modified polyethylene (MAPE) and of the length of thecarbon chain graft (CCG) between a (HDPE) matrix and wood fiber is studied. Furthermore, Scanning ElectronMicroscope (SEM) is used to characterize the morphology of the wood fibre / HDPE matrix interface forspecimens with carbon chain grafted.