Дисертації з теми "Composites variables et anisotropes"
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Chevalier, Romain. "Modélisation multi-échelles du comportement hygro-mécanique et étude de la stabilité dimensionnelle de structures composites lamellées collées aboutées en Pinus pinaster (Ait.)." Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0057.
Повний текст джерелаThis thesis focuses on the development of a multi-scale model of the hygro-mechanical behaviour and the study of the shape stability of glued laminated timber (GLT) made of Pinus pinaster (Ait.). Wooden structures are subject to dimensional variations due to changes in climatic conditions. In the case of GLT structures, shape stability can be achieved through systematic design based on the properties of the constituent lamellae. To this end, a multi-scale model based on an exhaustive bibliographic study of the properties of Pinus pinaster (Ait.) has been developed. Using a numerical homogenisation method and a metamodel based on Non-Uniform Rational Basis-Spline (NURBS) hypersurfaces, this model provides a spatial representation of the heterogeneous, variable, and anisotropic properties of Pinus pinaster (Ait.) lamellae. In addition, configurations of GLTs, based on laminate theory, have been proposed and experimentally subjected to variations in climatic conditions. The induced displacements are measured using a digital image correlation method. Finally, a comparison of the displacements is carried out, enabling the recommendation of GLT configurations that improve the shape stability of the GLTs produced by the Gascogne Bois company
Carpentier, Luc. "Caractérisation micromécanique de matériaux composites et anisotropes par indentation instrumentée." Ecully, Ecole centrale de Lyon, 1994. http://www.theses.fr/1994ECDL0034.
Повний текст джерелаTiteux, Isabelle. "Problemes de fracture et comportement local pour les plaques composites anisotropes." Paris 6, 1995. http://www.theses.fr/1995PA066478.
Повний текст джерелаBensaid, Samir. "Contribution à la caractérisation et à la modélisation électromagnétique et thermique des matériaux composites anisotropes." Nantes, 2006. http://www.theses.fr/2006NANT2107.
Повний текст джерелаThe carbon fibre composite materials cover a lot of manufacturing industries. To assemble parts of these composites several techniques are used. The technique using electromagnetic induction is very interesting; for his advantages such as the fast, without contact and localised transmission of energy to the assemblage interface. The goal of this thesis is to model in 3D, the induction heating of composite materials by taking into account of the anisotropy. Owing to the problem of the scale factor, these materials are replaced by homogeneous equivalent materials; so their electromagnetic and thermal properties are obtained either by using the homogenisation or experimental methods. In this work, to identifying the electric conductivity, one proposed an experimental method based on the impedance measurement. In addition, in our case, these materials are in the form of plate with very small thickness compared to the other dimensions. The shell elements associated to the nodal finite elements are then used. Two models have been developed, a monolayer anisotropic shell elements model applied to composites of unknown structures and a multi-layer model dedicated to the laminated composites with oriented structures. A confrontation between the simulation and experimental results (in induction heating) gave an acceptable difference. These models are applied to improve an industrial application of an induction assembly of composite materials
Bensaid, Samir. "CONTRIBUTION A LA CARACTERISATION ET A LA MODELISATION ELECTROMAGNETIQUE ET THERMIQUE DES MATERIAUX COMPOSITES ANISOTROPES." Phd thesis, Université de Nantes, 2006. http://tel.archives-ouvertes.fr/tel-00424804.
Повний текст джерелаPéron, Mael. "Mesure et modélisation des phénomènes de retraits anisotropes dans les matériaux composites durant leur mise en forme." Nantes, 2016. http://archive.bu.univ-nantes.fr/pollux/show.action?id=3eecb137-7a10-43b9-bc55-9ad8b87d3678.
Повний текст джерелаA fine thermo-chemo-mechanical modeling of the material behavior is necessary in order to predict composite parts final shape and properties. There are two options in order to feed these models: estimating the material effective properties thanks to the properties of its constituents, or directly measuring the composite material properties. At first, a multiphysics model of the thermosetting resins characterization device called PvTα was developed. It was validated compared to experimental results and suggested that temperature and degree of cure gradients had to be taken into account when measuring the resin bulk modulus. Then, asymptotic expansion homogenization method was used to model the heat transfers during the cure of composite materials. The upscaling possibility was discussed. This method was then applied to a linear elasticity model, allowing to estimate thermal expansion and chemical shrinkage tensors, as well as the mechanical properties evolution of a unidirectional material during cure. The coupling of these different physics was performed, leading to the prediction of the deformation of a part during cure. Finally, a new characterization device was developed. It allows for the simultaneous recording of the material deformations along two different directions, as well as the degree of cure and temperature. The first results are very promising and validated compared to other measurements and to numerical results from the homogenization method
Lamarre, Jean-Michel. "Propriétés optiques linéaires et non-linéaires de nanocomposites métal-diélectrique anisotropes." Phd thesis, Université Paul Cézanne - Aix-Marseille III, 2008. http://tel.archives-ouvertes.fr/tel-00471600.
Повний текст джерелаNeau, Guillaume. "Ondes de Lamb dans des plaques anisotropes viscoélastiques : étude des fronts d'onde et atténuation." Bordeaux 1, 2003. http://www.theses.fr/2003BOR12634.
Повний текст джерелаArif, Irwandy. "Modélisation des milieux anisotropes et fractures : application aux exploitations ardoisières." Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPL126N.
Повний текст джерелаMouchtachi, Ahmed. "Evaluation non destructive par ultrasons des propriétés d'élasticité des matériaux anisotropes : mesure de vitesses et résolution du problème inverse." Lyon, INSA, 1996. http://www.theses.fr/1996ISAL0034.
Повний текст джерелаThe main objective of this work is the full elastic characterization of anisotropic composite materials which are elaborated as thin plates of a few millimeters. The elastic properties are obtained from wave velocity measurements using two devices: an immersion bench with classical piezoelectric transducers, and a contactless device based on a Nd YAG pulsed laser for the generation of ultrasounds and an interferometer probe as a receiver. The immersion technique has appeared very efficient for the determination of anisotropic elastic properties. Thanks to an optimization process; the nine independent elastic constants of orthotropic composite materials have been successfully determined from phase velocity measurements using only one sample. Furthermore, we have developed an original approach based on a statistical method to evaluate the errors on the optimized elastic constants. Because of their possibilities of following the elastic properties of materials versus temperature, we have also been interested in contactless techniques. The preliminary tests have been realized at room temperature in order to evaluate the potentialities of this approach. We have studied the wave propagation in an aluminum matrix composite reinforced with unidirectional carbon fibers. With this technique, because of the point nature of both the acoustic source and the optical probe, only group velocities can be measured. The determination of elastic constants from these velocities is a difficult task, especially when we have no information about transverse modes. So, because it is difficult to measure the velocities of these modes, we have solved this inverse problem with numerical simulated data using a particular optimization process
Ruffio, Emmanuel. "Estimation de paramètres et de conditions limites thermiques en conduction instationnaire pour des matériaux anisotropes." Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2011. http://www.theses.fr/2011ESMA0019.
Повний текст джерелаThis study deals with the resolution of two types of inverse heat transfer problem: estimation of thermophysical parameters and estimation of thermal boundary conditions. A first part is devoted to the 3D-flash method which is used to estimate the three thermal diffusivities corresponding to the three principal directions of an anisotropic material. This work led to the realization of a experimental setup. The thermal excitation is provided by a CO2 laser and the temperature fields are acquired using infrared thermography. The thermal diffusivities are estimated by combining an estimator, an experiment and an analytical modeling. Different estimators are proposed and compared, based on their standard deviations. Moreover, a procedure to perform experiment design is presented to further reduce these standard deviations. In the second part, two studied cases consisting in estimating thermal boundary conditions are presented. Both underlying systems involve materials whose thermal properties are known. The thermal boundaries are estimated using temperature measurement provided by thermocouples. The first case deals with the evaluation of heat transfer between the gas and the inner-surface of a high pressure hydrogen tank. In the second case, the objective is to estimate the heat flux absorbed by a composite sample exposed to an oxygen-acetylene torch, in order to simulate the ablation phenomena under extreme conditions. Optimization algorithms are essential in this work. Gradient-based methods are used for parameters estimation and thermal boundary estimation problems. Stochastic algorithms appear to be well adapted in the framework of experiment design problems
Carminati, Paul. "Composites SiC/SiC à interphase de type BN de compositions variables et réactivité optimisée." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0248/document.
Повний текст джерелаSiC/SiC composites with SiC-based fibres and SiC matrix are developed for aeronautic applications. In order to improve their life time in an oxidizing atmosphere at high temperature, the use of BN interphase is recommended, as far as liquid boron oxide can protect the material. However, this glassy material is known to be very sensitive to moisture because boron oxide volatilizes quickly under high temperature. The aims of this work are (i) to maximise the structural organization of BN deposited by CVD/CVI to improve its oxidation resistance and (ii) to assess the interest of elemental addition to boron nitride allowing thermodynamic retention for B2O3 under wet air. Relationships between gas phase composition, deposition rates, and microstructure have been established in this work. Unfortunately, if the oxidation resistance of BN perpendicular to its (002) crystal planes increases with its structural organization, it appears to be hardly improved along the (002) planes. Nevertheless, aluminium addition to BN has led to Al4B2O9 crystals generation, asAl2O3 reacts together with B2O3 under high temperature. These materials therefore appear tobe able to seal SiC matrix cracks. As a result, the global oxidation resistance under wet air of SiC/SiC composites with B(Al)N interphases can been significantly improved. Additional oxidation tests, especially under thermal cycling, are needed to definitively conclude about this point
Enguehard, Franck. "Mesure de la diffusivité thermique radiale de matériaux anisotropes et détection de fractures transverses par la technique photothermique impulsionnelle de diffusion convergente." Châtenay-Malabry, Ecole centrale de Paris, 1991. http://www.theses.fr/1991ECAP0235.
Повний текст джерелаFerrand, Alain. "Interfaces alumine-fer : relations entre l'énergie, la structure et les variables thermodynamiques température et potentiel chimique d'oxygène." Paris 11, 2001. http://www.theses.fr/2001PA112276.
Повний текст джерелаMixed oxides polycrystals (Al,Fe)2O3 with differents doping levels obtained by hot pressing, as well as oligocrystals elaborated by the floating-zone method in the image furnace have been exposed to sufficiently reducing atmosphere to precipitate metallic iron. Thus, we could determine for the lowest oxygen activity, the dense alumina planes delimiting metallic iron precipitates, as well as interfacial distance ratios characterizing the equilibrium shape. At higher oxygen activity, we observe a modification of the equilibrium shape, connected to the oxygen activity change. This evolution might be described by a model of Gibb's adsorption at metal-oxide interfaces, that predict the evolution with oxygen activity of the excess concentration of different interfacial alumina planes, alowing us to evaluate the stabilization of interfacial energy arriving from bonds established between metallic iron and alumina at the ends of the coexistence field. .
Ketata, Lassaâd. "Etude et identification du comportement macroscopique de structures en matériaux anisotropes à l'aide d'essais d'optique cohérente." Rouen, 2000. http://www.theses.fr/2000ROUES050.
Повний текст джерелаMagnier, Vincent. "Modélisation tridimensionnelle par éléments finis enrichis pour le calcul de singularités de délaminage et à la jonction de matériaux anisotropes." Thesis, Lille 1, 2008. http://www.theses.fr/2008LIL10083/document.
Повний текст джерелаMaterial and/or geometry discontinuities can cause concentrations of stress. This stress can be harmful to the strength of the structure. Indeed, the state of stress in these areas can be singular. This kind of stress, called "overstress", can be modeled in practice by regular three-dimensional finite element, unless very finely meshed. To overcome this difficulty, we propose a numerical method in two steps. The first determines the singularity order and the mode fracture. The second step is to include these results in a description of the mechanical fields prevailing in the structure to obtain complete information on the initiation of the crack via a rule of connection. This connection was implemented in a finite element mixed formulation named "Metis" and a finite element displacement formulation. The proposed technique has been extended for all given singularity order. So, this technique can resolve any problems like free-edge or V-notch at the junction of several anisotropic materials with great precision. The dual analysis of a problem with these two types of formulations provides a posteriori error. Numerical applications for calculation of stress intensity factors and singularity order validate the proposed method on examples from literature. The results show a good consistency and good accuracy. Moreover, these methods require only low CPU time
Monnier, Thomas. "Ondes de Lamb dans les milieux stratifiés : application à la surveillance in situ et en temps réel de l'endommagement de structures composites." Phd thesis, INSA de Lyon, 2001. http://tel.archives-ouvertes.fr/tel-00573987.
Повний текст джерелаDe, Blasi Serge. "Étude modélisation et caractérisation de nano-composites piézoélectriques-magnétorestrictifs à permittivité et perméabilité variables par couplage mécanique : application aux dispositifs hyperfréquences accordables en fréquence." Brest, 2007. http://www.theses.fr/2007BRES2024.
Повний текст джерелаIn our world of telecommunications, making electronic devices able to work with different standards at the same time seems to be incompatible with the growing need for miniaturization. The fusion of many sub-systems into one working at different frequencies can be a way to contribute to expanding the market by lowering manufacturing costs and circuit size. One way to reach this goal is to make tunable devices whose properties are modified under the action of an external command like an electric or a magnetic field. The goal of this thesis is the study of piezoelectric/magnetostrictive composites (PMC’s) driven by an electric field. The properties of the PMC’s were studied and an electromagnetic characterization of those materials was performed. Theoretical and experimental tools were developed in order to allow a future insertion in microwave devices. A 140 nm-thin ferromagnetic FeCoSiB was deposited on a soft 100 pm-thick PZT substrate and a 25% variation of the magnetic layer permeability has been measured as a static electric field was polarizing the piezoelectric layer. The present study was also aimed at incorporating PMC’s inside microwave transmission lines for the design of magnetic-based tunable microwave functions to be biased by a dc electric field. A FEM-based environment, able to simulate any combination of physical processes that can be described with partial differential equations (PDE’s), was used to fulfill our ambitions
MANISCALCO, CYRIL. "Contribution a l'etablissement de lois de previsions du comportement electromagnetique de materiaux composites : applications de protocoles de caracterisation dielectrique (1mhz-18ghz) a des materiaux heterogenes et anisotropes d'origine industrielle. determination des permittivites intrinseques." Paris 6, 2000. http://www.theses.fr/2000PA066600.
Повний текст джерелаMujica, Randy. "Layer-by-Layer assembly of nanocellulose composite films with bio-inspired helicoidal superstructures." Thesis, Strasbourg, 2020. http://www.theses.fr/2020STRAE011.
Повний текст джерелаThe remarkable optical and mechanical properties of natural materials are often associated with the complexity of their hierarchical structures. One of the most complexes is the helical structure which consists of several layers of unidirectionally aligned fibers whose orientation rotates with respect to their neighboring layers. This so-called Bouligand microstructure is responsible for the enhanced impact resistance of the shell of some crustaceans as well as the preferential reflection of circularly polarized light of certain fruits and insects. Here, we fabricated complex bio-inspired thin films made of cellulose nanofibrils and poly(vinylamine) using the layer-by-layer (LbL) approach and grazing incidence spraying (GIS), a method allowing to control the in-plane alignment of anisotropic nano-objects like cellulose nanofibrils. We demonstrated the independent direction of alignment of each cellulose layer, which allowed the preparation of thin films with well-defined internal structures, namely, unidirectional, cross-ply or helical arrangement of the reinforcing nanofibrils, which is impossible to achieve by any other fabrication process. The optical properties of these films were characterized by circular dichroism (CD) and by Mueller matrix ellipsometry. The chirality observed for helicoidal films is controlled by the rotation direction, the pitch, and the number of layers. The mechanical properties of these cellulose-based films were studied by various nanoindentation methods. A nano-contact fatigue methodology showed an increased ductility of the unidirectional and helicoidal films, which can be indirectly related to enhanced absorption of energy of this material owing to their internal structure
Vacossin, Bruno. "Interaction d'un faisceau ultrasonore avec un défaut de dimension finie dans un matériau stratifié anisotrope." Compiègne, 2008. http://www.theses.fr/2008COMP1739.
Повний текст джерелаThe interaction between an acoustic ultrasonic bounded beam and a multilayered structure immersed in a fluid has been studied. The structure is composed of two anisotropic elastic layers. When the structure is sound, the real structure shows a bonded finite length crack, localised on this internal interface. The aim of this study is to propose a numerical simulation in order to estimate in what extend the analysis of the ultrasonic beam restored by the structure is able to detect the presence of the crack. The representation of the beam uses plane wave decomposition and requires fast Fourier transforms. Kirchhoff’s approximation is introduced. Then the crack is treated as a passive transducer. Numeral studies are proposed in order to estimate in what circumstances crack could be detected. Lamb wave generation could improve the detection
Longpré, Philippe. "Personnalité et compétences en emploi : comparaison de la capacité prévisionnelle de deux configurations de la personnalité." Thèse, 2013. http://hdl.handle.net/1866/10349.
Повний текст джерелаRecent studies confirm that personality tests are widely used for selection in North American organizations and that their frequency of use continues to grow (Boudrias, Pettersen, Longpre & Plunier 2008; Rothstein & Goffin, 2006 ). However, research shows that the predictive relationship between personality and overall job performance is generally weak and that it remains similar to the initial results on the subject (Morgeson et al, 2007b;. Dzieweczynski & Murphy, 2005). This thesis aims to determine whether an improvement in the predictive relationship between personality and job performance could be achieved by modifying the way data obtained from personality inventories is used and by specifying the criteria to predict. To do so, the predictive ability of an approach centered on the criterion, that is to say, the use of compound variables of personality, is compared with the traditional approach centered on the predictor, in this case, the five factors (Big five). Moreover, job performance is operationalized in terms of job competencies, which makes it possible to differentiate the criteria and to increase its specificity. Hypotheses specifying the personality factors that should predict each competency are tested. In addition, hypotheses specifying the personality traits used to create the compound variables are also tested. Finally, a hypothesis comparing the predictive power of the two approaches is tested. The sample consisted of 225 employees occupying various jobs in a large Quebec organization. These employees have completed a work-contextualized personality inventory through the selection process of the organization. Their immediate supervisor conducted an assessment of their competencies and of their performance at least six (6) months after being hired. Thus, the design of this research is predictive and the method used is based on a confirmatory strategy, which is similar to the normal practices of testing used by industrial and organizational psychologists. Results indicate that the competencies are better predicted by a predictor-centered approach. Indeed, only three hypotheses pertaining to the relationship between personality factors and competencies proved partially supported. The results of additional statistical analyzes, performed in order to better understand the initial results, suggest the presence of moderating variables, including, in particular, the situational characteristics. In conclusion, it seems, at this time, much more likely for researchers to find a structured method for creating compound variables that would provide stronger predictive relationship, than to discover new compound variables that would be predictive of performance in every job and every organization. In addition, we encourage practitioners to pay attention to the way they use personality data. For the moment, it seems that personality factors predict, in part, future job performance. However, empirical evidence on the effectiveness of alternative approaches is relatively rare, and insufficient to accurately guide practitioners through the choice necessary for their use.