Teses / dissertações sobre o tema "Composites à fibres – Matériaux – Fatigue"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Veja os 50 melhores trabalhos (teses / dissertações) para estudos sobre o assunto "Composites à fibres – Matériaux – Fatigue".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Veja as teses / dissertações das mais diversas áreas científicas e compile uma bibliografia correta.
Coutand, Bernard. "Etude de la déformabilité à haute température de matériaux composites à matrice d'alliage léger renforcée par des fibres courtes". Bordeaux 1, 1991. http://www.theses.fr/1991BOR10508.
Texto completo da fonteLegrand, Nicolas. "Fatigue de composites à matrice métallique base titane à renfort unidirectionnel de fibres SiC". ENSMP, 1997. http://www.theses.fr/1997ENMP0844.
Texto completo da fonteThe primary objective of this work is to understand the physical origin of fatigue fracture at high temperature of metal matrix composites SCS6/Ti6-4, SM1140+/Ti6242 and SCS6/Ti6242. The fatigue behaviour of the material is studied in longitudinal (loading parallel to the fiber axis) and transverse (loading perpendicular to the fiber axis) orientations. In longitudinal fatigue, performed at 450 and 550°C on SCS6/Ti6-4 and SM1140+/Ti6242, three major damage mechanisms were identified : the global load transfer from matrix to fibers due to matrix cyclic softening (mechanism n°1), the local interfacial degradation close to broken (mechanim n°2) and the infuence of environment on mechanical fiber properties (mechanism n°3). Damage kinetics of these different mechanisms were identified experimentally using microscopic observations and acoustic emisson technic. A micromechanical modelling, taking into account of the statistical behaviour of fibers has confirmed and quantified influence of these mechanisms on fatigue fracture of the composite : with this model, it was demonstrated that for sufficiently high fatigue loadings (stress up to 1000 MPa), the local interfacial degradation near fiber failures may control fatigue life of the composite. At last, based on experimental acoustic emissions results, this modeling enables to predict both damage kinetics and rupture in fatigue. It is thus an interesting numerical tool to improve and optimize composite fatigue properties. As far as the transverse fatigue is concerned, it was determined in isothermal (at 600°C) and in non isothermal (between 200 and 600°C) conditions. In that orientation, damage mechanisms are due to interfacial debondings and slidings and oxidation of the carbon interface. A simple one dimensionnal "3 bars" model has been formulated (taking into account matrix viscoplasticity). It has demonstrated that cyclic viscoplasticity plays a key role in fatigue fracture along this orientation
Hunault, Patrick. "Contribution à l'évaluation de l'endommagement par fatigue de composites unidirectionnels carbone-époxy". Toulouse, INPT, 1990. http://www.theses.fr/1990INPT022G.
Texto completo da fonteGoumghar, Amirouche. "Élaboration et étude des performances dynamiques de composite bio-sourcés à architecture hybride lin—verre". Electronic Thesis or Diss., Reims, 2023. http://www.theses.fr/2023REIMS002.
Texto completo da fonteThe use of natural fibre-reinforced composite materials is growing in various sectors such as automotive and packaging. However, the problem of their sensitivity to humidity still hinders their use in applications exposed to extreme environmental conditions. Therefore, the hybridization of natural fibres with synthetic fibres can constitute a promising way to improve some properties of natural fibre-reinforced composites. It is in this context that the present doctoral work is situated. It presents an experimental analysis of the tensile-tensile fatigue and low-energy impact fatigue behaviour of non-hybrid and hybrid flax-glass/epoxy laminates. An investigation of their durability after water aging until saturation is also presented. To this end, several plates of non-hybrid and hybrid flax-glass/epoxy composites have been fabricated by the vacuum infusion process. First, we carried out a monotonic tensile characterization of the studied composites and evaluated the kinetics of moisture diffusion within these materials. The results of these tests show that the addition of glass layers to the flax/epoxy laminate improves its mechanical properties and also reduces its mass of water absorbed at saturation. Then, cyclic fatigue tests were performed on unaged and aged composite specimens. These fatigue tests were coupled with the acoustic emission technique in order to identify the damage mechanisms and their chronology of appearance. To evaluate the effect of fatigue loading on the loss of stiffness, hysteresis loops and the damping factor of non-hybrid and hybrid composites were investigated. The analysis of the acoustic signals makes it possible to identify three classes of acoustic signals in all the studied composites. These three classes are attributed to the main damage mechanisms such as matrix cracking, fibre/matrix decohesion and fibre breakage. This attribution is supported by microscopic observations obtained using a scanning electron microscope. Finally, low-energy impact fatigue tests were performed on unaged and aged composite samples. The obtained results clearly show that the flax/epoxy composite absorbs a large part of the impact energy and transforms it into elastic energy. However, the glass/epoxy laminate consumes this energy in damage and breakage. In addition, water aging weakens all the studied composites and reduces their resistance to impact fatigue
Al-Maghribi, Abir. "Comportement des matériaux composites à fibres courtes : applications à l'impact basse vitesse". Toulouse 3, 2008. http://thesesups.ups-tlse.fr/337/.
Texto completo da fonteThe objective of this work is to investigate the behaviour of a short fiber composite material subjected to low speed impacts. The studied material is a SMC composite material realized by compressive moulding. A first part of the study gives elastoplastic with damage behaviour of this type of material. These laws were coded into the user defined material subroutine of (LS-DYNA3D and EUROPLEXUS). Characterizations tests of the SMC-R were realized in order to identify non linear behaviour. The tests realized are tensile test, compressive test, shearing test and dynamic compressive test. The tests have allowed us to identify damage behaviour. The obtained behaviour is necessary for the study of impact. The second part of the study presents the experimental analysis of the impact. The impacts were realized for various energies (4, 8, 12, 16 J). The defects after impact tests are controlled by RX testing, US control, and microscopic observation, in the aim to analyze and quantify the defects create during the impacts. These analyses showed a conical defect in the thickness of plates. Finally a comparison is made between the results obtained experimentally and those obtained from an explicit numerical simulation. This comparison shows that the numerical simulations of impact behaviour are in good agreement with the experimental results. The results globally show a global correlation for the load-displacement behaviour and a local correlation for the defect size
Dalmaz, Anne. "Etude du comportement en fatigue cyclique a hautes températures du composite tisse fibre de carbone/matrice carbure de silicium 2,5D C/SiC". Lyon, INSA, 1997. http://www.theses.fr/1997ISAL0085.
Texto completo da fonteThis study investigates the mechanical behavior of a 2. 5D woven multi-layered carbon fiber composite with a silicon carbide matrix, manufactured by the SEP. This material is used in the aerospace industry for the manufacture of parts operating under extreme conditions (very high temperature, high loading stress and a strongly oxidizing atmosphere). It is, therefore, essential to establish it is mechanical behavior under cyclic loading at elevated temperature. The aim of this study is therefore to define the damage mechanism of the 2. 5D C/SiC composite controlling the mechanical behavior of the material subjected to cyclic loading over a range of temperatures, under an inert atmosphere. A finite element model was developed to explain the crack networks operating during loading at various temperatures. A new technique, based on the method of homogenization, was established to model the Young's modulus of composite ceramic/ceramic weaves. This technique was employed, along with our other results, to improve the understanding of the damage sequence during cyclic fatigue. The evaluation of the mechanical behavior of the composite with increasing temperature was found to change significantly at the manufacturing temperature of the composite (1000°C). For temperatures below 1000°C, the mechanical behavior is controlled by the residual thermal stresses and crack closing behavior. The composite shows improved toughness, modulus, and cycles to failure, as the temperature increases. The increase in modulus observed during cyclic loading at elevated temperature results from crack closing caused by localized deformation of the material. For temperatures above 1000°C the mechanical behavior is controlled by temperature dependent mechanisms, as yet, not well understood
Nouri, Hedi. "Modélisation et identification de lois de comportement avec endommagement en fatigue polycyclique de matériaux composites à matrice thermoplastique". Paris, ENSAM, 2008. http://www.theses.fr/2008ENAMA015.
Texto completo da fonteThe present work is a contribution to the phenomenological modelling of fatigue non-linear cumulative diffuse damage in short glass fibre reinforced thermoplastic matrix composites. In such materials, fatigue damage kinetic exhibits three stages, namely: i) material softening and damage initiation, ii) coalescence and propagation of micro-cracks, iii) macroscopic cracks propagation and material failure. The proposed model is built in the framework of the continuum damage mechanics and aims at predicting these three stages of the damage evolution. It extends the previous approach and takes into account the important stiffness reduction observed during the first damage stage. The above is modelled by the integration of a combined Norton-like power law and an exponential law expressing the damage rates as a function of the associated thermodynamic dual forces. The model has been formulated in terms of strain energy, so that makes easy its numerical implementation into the finite element code Abaqus/Standard through a user defined material subroutine UMAT. Damage evolutions predicted by the developed model reproduce well those observed for this kind of composites under cyclic loading. Two identification strategies are developed. The first identification strategy based on homogeneous tensile fatigue tests performed in the longitudinal and transversal directions of a PA6-GF30 and a PP-GFL40. A second identification strategy based on the use of optical whole-field displacement/strain measurements by digital image correlation coupled to an inverse method from one single coupon
Duboquet, Emilie. "Vers une approche locale du phénomène de fatigue mécanique. Application aux matériaux et aux structures en composites à fibres continues". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK021/document.
Texto completo da fonteThe original concept of mechanical fatigue was linked to the failure of structures and was treated at first within the framework of Fracture Mechanics. Models developed to explain this phenomenon must therefore be able to be applied to structures: changing the structure means changes to the model and its identification. It is therefore judicious to develop models capable of treating both the damage processes and also able to be used within a local framework: to this end a method based on Damage Mechanics seems appropriate. This approach has long been employed and requires only the identification of damage processes at the level of the RVE (Representative Volume Element) to be used for any structural geometry. However incoherencies can be encountered such as when the number of load cycles applied to the macroscopic structure does not reflect the internal loading kinetics, leading, for example to effects due to the frequency of loading. This can be found to influence the laws governing the evolution of damage phenomena at the local level, leading to wrong conclusions. Nevertheless this is not inevitable if precautions are taken. This goal of this study has been to introduce rigorous concepts of mechanical fatigue in the local framework of Damage Mechanics and to carry out a local approach to fatigue. The ultimate aim has been to be able to carry out calculations on structures subjected to fatigue loading with the same degree of finesse as under quasi-static conditions.An initial step has been to reveal the shortcomings of existing models and show that at present no model of a structure subjected to fatigue using Damage Mechanics is perfectly satisfactory.As a result the notion of the fatigue problem has been formulated and used as a base for defining a suitable framework for developing a local approach to fatigue.A deliberate goal has been to avoid constructing incremental fatigue laws but to introduce the real effects of loading cycles deduced from the evolution of behavioural laws obtained in quasi-static tests, requiring rules of linearization and a clear definition of the adopted approach.Benefiting from specific problems involving fatigue damage and applying them to this approach, a rigorous description of the phenomena and the identification of a fatigue damage model applied to intra-laminar cracking has been developed. The laws governing the local approach have been described for the case of a structure subjected to fatigue. It has been shown that for a given case of a material and damage processes the proposed approach applied to a structure subjected to fatigue loading can be modelled with the same ease as resolving the effects of quasi-static loading.This study has created very general foundations for a new approach to understanding the fatigue of structures. It clarifies the fatigue concept by defining it within a tightly defined framework with the goal of formulating a local approach to fatigue applied to the calculation of structures subjected to fatigue loading. It has been successfully used for a particular configuration. However for the present it is difficult to assert that it can be used as a local approach for all fatigue phenomena, in all materials and for the most general types of loading. The study has not had the ambition of providing a solution to all these cases but rather to open a new approach to resolve other cases and possibly to provide a guideline to achieving a truly local approach to a general solution of the fatigue of structures
Pires, Isabelle. "Vieillissement dans l'antigel de matériaux composites polyamide-6,6 renforcé par des fibres de verre courtes". Montpellier 2, 2000. http://www.theses.fr/2000MON20124.
Texto completo da fonteDespringre, Nicolas. "Analyse et modélisation des mécanismes d'endommagement et de déformation en fatigue multiaxiale de matériaux composites : polyamide renforcé par des fibres courtes". Thesis, Paris, ENSAM, 2015. http://www.theses.fr/2015ENAM0058/document.
Texto completo da fonteThe current work focuses on a new micromechanical high cycle fatigue visco-damage model for short glass fiber reinforced thermoplastic composites, namely: PA66/GF30. This material, extensively used for automotive applications, has a specific microstructure which is induced by the injection process. The multi-scale developed approach is a modified Mori-Tanaka method that includes coated reinforcements and the evolution of micro-scale damage processes. Their description is based on the experimental investigations of damage mechanisms previously performed by the team. Damage chronologies have been proposed involving three different local degradation processes: fiber-matrix interface debonding/coating degradation, matrix microcracking and fiber breakage. Their occurrence strongly depends on the microstructure. The developed model integrates these damage kinetics and accounts for the complex matrix viscoelasticity and the reinforcement orientation distributions induced by the process. Each damage mechanism is introduced through an evolution law involving local stress fields computed at the microscale. The developed constitutive law at the representative volume element scale is implemented into a C++ scientific library, SMART+, and is designed to work with Finite Element Methods. The model identification is performed via reverse engineering, taking advantage of the multiscale experimental results: in-situ SEM tests as well as quantitative and qualitative μCT investigations
Gilmore, Richard. "La friction des composites carbone-carbone : étude des mécanismes contrôlant le comportement tribologique des matériaux carbonés dans les freins d'avion". Mulhouse, 1994. http://www.theses.fr/1994MULH0330.
Texto completo da fonteBen, Toumi Rim. "Endommagement par fatigue et durée de vie de structures en matériaux composites à fibres continues pour application liaison au sol". Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0064.
Texto completo da fonteThe reduction of fuel consumption and greenhouse gas emissions is one of the most important challenges facing the automotive industry. An efficient strategy to meet these targets is by reducing the weight of vehicle. In this work, we are interested in introducing composite materials in automotive structural parts and especially in suspensions which are subjected in service to high-cycle fatigue loadings. Therefore, a good prediction of fatigue life is required. As continuous fibre-reinforced composites provide good mechanical properties combined with a low density, they have been increasingly used in many lightweight structures. However, the fatigue behaviour of composites has not been widely investigated. This work aims at developing an approach to predict the lifetime in service of structural automotive components, made with woven glass / epoxy composite. This approach has to be easy to use by design engineers at the scale of the structure. The first step is the characterization of the material. Then, the processes involved in degradation of the composite subjected to both monotonic and cyclic loadings were identified.Given the experimental results and the existing approaches, a multiaxial fatigue criterion is proposed. An optimization of the identification protocol is also performed to reduce the quantity of needed experimental data. Finally, the fatigue life prediction model criterion is validated by tests on notched coupons and on composite vehicle's suspension
Muller, Laura. "Estimation accélérée des performances en fatigue de matériaux et structures composites thermoplastiques par le suivi de leur auto-échauffement". Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0035/document.
Texto completo da fonteThis thesis is part of the study on the fatigue of composite materials. It consists in estimating the fatigue performance of a thermoplastic composite woven material, made of carbon fibres and PA66 matrix, by self-heating tests. Following a characterization of the damage to the material under monotonous loading by acoustic, thermal and optical monitoring, a fatigue test campaign is carried out on two material configurations, at 0° and 45°. Several methods for modelling the S-N curve are proposed to determine the fatigue limit of the material. It is shown that the estimation of this limit and its confidence interval is complicated by the large dispersion of experimental data. Self-heating tests are then carried out, consisting of applying a fatigue load over a limited number of cycles, increasing the maximum stress applied step by step. Signal processing tools are developed to determine a threshold stress and its confidence interval at which the heating accelerates. However, this threshold stress remains conservative in comparison to the fatigue limit. Another approach is then developed, consisting in monitoring the amplitudes of the thermal signal. New signal processing tools are being developed to map the specimen from the harmonic amplitudes. It is then shown that it is possible to obtain the same curves as the selfheating curves by monitoring the amplitudes of the harmonics, and this for only a hundred cycles. A new self-heating test protocol is then implemented, based on a hundred steps of only a few hundred cycles, allowing harmonics to be monitored with almost continuous final curves in a minimum of time
Vauthier, Emmanuelle. "Durabilité et vieillissement hygrothermique de composites verre-expoxy soumis à des sollicitations de fatigue". Ecully, Ecole centrale de Lyon, 1996. http://www.theses.fr/1996ECDL0043.
Texto completo da fonteLu, Fang. "Caractérisation et modélisation du comportement cyclique en fatigue uniaxiale/multiaxiale des composites à fibres courtes : Thermoplastiques (PA66) renforcés de fibres de verre". Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM072.
Texto completo da fonteAimed at better understanding the mechanical behavior of short fiber reinforced thermoplastics (SFRP), our study focused on the characterization and modeling of the cyclic fatigue behavior of polyamide 6,6 reinforced by 30 wt% of short glassfibers (PA66GF30). From the experimental point of view, uniaxial/biaxial tension-tension fatigue tests and 3-point bending fatigue tests were carried out, in order to extend the fatigue lifetime criterion based on the restored strain energy and validated in uniaxialcase. The mechanical analyses of these tests show that, this criterion accounts not only for the effects of fiber orientation,temperature and water content, but also for the type of loading. From the numerical modeling point of view, the behavior of PA66GF30 in linear regime is modeled by the homogenization model of Mori-Tanaka and Advani-Tucker for the elastic case, and is modeled by the generalized Maxwell model extended to the anisotropic case for the viscoelastic case. In addition, the triple equivalence Time-Temperature-Humidity is introduced into the model. For nonlinear regime behavior, a damageable anisotropic visco-elasto-plastic phenomenology model is proposed to caracterize the cyclical fatigue behavior. The identified parameters of new anisotropic visco-elasto-plastic damage model are validated on these 3 types of specimen and the industrial structural parts. By applying the fatigue lifetime criterion via a post-processing, the mapping of energy and lifetime allows us to locate the fracture area and to estimate the lifetime of structural parts. A conservative factor lower than 5 for estimated lifetime shows the accuracy of prediction for these first validations. As a result, our study provided a fatigue design tool for the dimensioning of SFRPs, which makes it possible to optimize the geometry of the parts or their process-induced microstructure in relation to their stiffness and fatigue behavior
Pagano, Fabrizio. "Mécanismes de fatigue dominés par les fibres dans les composites stratifiés d’unidirectionnels". Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM039/document.
Texto completo da fonteUnder quasi-static and fatigue tension loads, the failure of a carbon fibre reinforced polymer laminate (CFRP) is usually driven by 0° plies. Carbon fibres give most of the stiffness and strength of these plies. In this work, the fatigue behaviour of 0° plies inside unidirectional (UD) and multidirectional laminates is analysed via multi-instrumented tension-tension fatigue tests. A numerical and experimental study is addressed to perform fatigue tests without the typical premature failures of the UD laminates. The acoustic emissions technique is used to identify the evolution law of fibre breaks. A finite element model is developed at the microscale (fibres and matrix) to analyse the fibre-driven fatigue mechanisms
Berthelot, Hélène. "Comportement sous sollicitations dynamiques de composites à âme mousse : Mécanismes d'endommagement". Ecully, Ecole centrale de Lyon, 1997. http://www.theses.fr/1997ECDL0002.
Texto completo da fonteSubagio, Bambang Sugeng. "Contribution à la modélisation de l'endommagement de fatigue en flexion dans les matériaux composites unidirectionnels". Ecully, Ecole centrale de Lyon, 1987. http://www.theses.fr/1987ECDLA008.
Texto completo da fonteCadu, Thomas. "Contribution au développement de l'utilisation des fibres naturelles dans les composites structuraux. Étude du comportement d'un composite Lin/Epoxy lors d'un vieillissement hygrothermique". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK055/document.
Texto completo da fonteIn recent years there is renewed interest for bio-sourced composites, including those based on flax fibers, and especially in the field of transport, mobility and leisure. In fact, the lower energy cost and environmental impact of flax fiber give it an advantage over glass fiber, while competing with its specific mechanical properties. However, flax fibers based composites long-term behavior remains poorly known in damp environments and constitutes an obstacle to a wider use. This work aims to provide adapted parameters to produce a high-grade flax/epoxy composite and to contribute to improve the durability knowledge of these materials. First, the influence of many processing parameters [(i) conditioning of the reinforcements, (ii) curing temperature, (iii) curing pressure, (iv) cooling speed, (v) exit temperature, (vi) post curing temperature and (vii) post curing duration] on the composites’ mechanical properties have been studied in order to manufacture high-grade materials. Then a “realistic” ageing method has been developed to study the durability of this kind of composites when exposed to water. Thus cyclic hygrothermal ageing has been applied to composite, resin and fiber bundles in the laboratory. Then multi-scale analyzes based on physicochemical, microstructural and morphological characterizations of the flax/epoxy composites helped to better understand the mechanisms responsible for the longitudinal and transverse mechanical properties’ evolutions over time
Bourbita, Faten. "Comportement en fatigue anisotherme des composites unidirectionnels à matrice titane renforcée par des fibres de carbure de silicium". Phd thesis, École Nationale Supérieure des Mines de Paris, 2011. http://pastel.archives-ouvertes.fr/pastel-00712981.
Texto completo da fonteSeghini, Maria Carolina. "Mechanical Analysis and Fibre/Matrix Interface Optimization for Next Generation of Basalt-Plant Fibre Hybrid Composites". Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0003.
Texto completo da fonteGlobal awareness of environmental issues has resulted in the emergence of “green” composites, in which natural fibres are used to replace synthetic ones. However, in semi-or structural applications, it can be inconvenient to use composites based on natural fibres. A possible solution to this problem is the development of hybrid composite materials, combining together plies of natural and synthetic fibres. In this framework, the aim of this research project was to develop basalt-flax fibre hybrid composites with a view to obtaining more environmentally friendly composites for semi-structural applications. Hybrid composites were produced through vacuum infusion molding with epoxy matrix.For comparison purposes, 100% flax fibre composites and 100% basalt fibre composites were also manufactured. A quasi-static and dynamic mechanical characterization showed that the hybridization allows the production of a composite with intermediate mechanical performances compared to those possessed by flax and basalt composites. However, the damage analysis has revealed the need to optimize the fibre/matrix interface adhesion quality, in order to increase the mechanical properties of the resulting hybrid composites. For this reason, different surface modification treatments have been specifically designed and investigated for flax and basalt fibres. Flax and basalt fibres were treated by the physical process of Plasma Enhanced Chemical Vapor Deposition. Flax fibres were also subjected to two chemical treatments using enzymatic species and supercritical CO2. The effects of the surface modification treatments on the thermal stability, morphology and mechanical properties of flax and basalt fibres have been investigated. The degree and extent of fibre/matrix adhesion were analyzed by micromechanical fragmentation tests on monofilament composites. The adhesion quality between fibres and both epoxy and vinylester matrices has been assessed in terms of critical fragment length, debonding length and interfacial shear strength. High-resolution μ-CT has been used to support the analysis of the damage mechanisms during fragmentation tests. For both flax and basalt fibres, the best results were obtained after the plasma polymer deposition process. This process was able to produce a homogeneous tetravinylsilane coating on the surface of basalt and flax fibres, which resulted in a significant increase in the fibre/matrix adhesion, thus paving the way for the next generation of more environmentally friendly hybrid composites for semi-structural applications
Alia, Adem. "Comportement à la rupture d'un composite à fibres végétales". Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI016.
Texto completo da fonteThe objective of this thesis is the characterization of the mechanical behavior and the damage of a woven jute / polyester composite. natural fibers are indeed an interesting ecological alternative to synthetic fibers, in particular glass fibers which are the most used for composite manufacturing. The studied composite is developed in the LMNM laboratory at IOMP, Sétif, Algeria. Two fibre orientations ([0] 8 and [+ 45 / -45] 2S) are considered. The mechanical characterization is carried out in monotonic tensile and compression as well as in cyclic fatigue. Mechanical and microstructural characterizations are carried out in the MATEIS laboratory. The study of the damage is carried out by combining five techniques: the evolution of mechanical parameters via cyclic and fatigue tests, microscopy, acoustic emission (EA), image correlation and micro- RX tomography. The study of the evolution of the mechanical parameters combined with the global analysis of the AE provides first indicators concerning the development of the damage during the tests. Microstructural analyzes allow to finely identify the damage mechanisms that occur during mechanical tests (fiber / matrix decohesions, matrix cracks and fiber breakage). For the segmentation of acoustic emission signals in monotonic tests, an unsupervised classification is used, emphasizing the choice of descriptors and the labeling of the classes obtained. Tensile tests instrumented by image correlation as well as in situ tensile tests under tomography allow to identify the chronology of appearance of the damage. These results are also used to label the obtained classes . The labeled signals are then used to create a library to identify the chronology of evolution of the modes of damage in cyclic fatigue achieved by supervised classification. Finally, all these analyzes made it possible to establish damage scenarios for the different damage modes and for the two orientations. It is thus possible to reconsider the development to optimize the mechanical properties
Redjel, Bachir. "Mécanique et mécanismes de rupture dans les matériaux composites SMC (Sheet Molding Compound)". Compiègne, 1987. http://www.theses.fr/1987COMPD067.
Texto completo da fonteAlbouy, William. "De la contribution de la visco-élasto-plasticité au comportement en fatigue de composites à matrice thermoplastique et thermodurcissable". Phd thesis, INSA de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00942294.
Texto completo da fonteKlimkeit, Bert. "Etude expérimentale et modélisation du comportement en fatigue multiaxiale d'un polymère renforcé pour application automobile". Phd thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aéronautique, 2009. http://tel.archives-ouvertes.fr/tel-00464186.
Texto completo da fonteFrançois-Brazier, Joël. "Caractérisation de la tolérance à l'endommagement et de la durabilité des composites ciment-verre par des essais de flexion avec des cycles de chargement-déchargement". Lyon 1, 1991. http://www.theses.fr/1991LYO10093.
Texto completo da fonteNony, Clément. "Modélisation multi-échelles de l'endommagement d'un composite à résine thermodurcissable renforcé de fibres courtes de carbones". Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0021/document.
Texto completo da fonteThe evolution of the industrial context is pushing the transport industry, and more specifically the automotive sector, toward better energy efficiency. This objective is partly achieved by the development of new composite material solutions. The current work is devoted to the mechanical characterization and the multiscale modeling of a new SMC composite material reinforced with short carbon fibers bundles. The objective is to build a first knowledge base on the behavior of this SMC under fatigue loading. Experimental investigations include the analysis of the microstructure, the characterization of the mechanical behavior under quasi-static and fatigue loading, as well as the analysis of the damage mechanisms. The proposed multiscale approach takes into account the microstructure of the composite at the two scales highlighted through two successive homogenizations by the means of a Mori-Tanaka based method. Such modelling strategy makes it possible to relate elasto-plastic behavior of the matrix through dedicated local constitutive laws and the behavior of the fibers to that of the composite material, and to integrate the orientation distribution of the bundles induced by the manufacturing process... The multiscale model was identified by the mean of an inverse computation method applied on the experimental results taken from the databases created during the works.The global constitutive law, computed at the scale of a representative elementary volume, has been implemented in the SMART+ scientific library in C++ language in such a manner to be compatible in a finite element analysis (FEA) framework
Pauchard, Vincent. "Etude des mécanismes de rupture des fibres dans les composites UD verre/epoxy sous sollicitation de fatigue longitudinale en milieu humide : application d'un modèle de corrosion sous contraintes". Ecully, Ecole centrale de Lyon, 2001. http://bibli.ec-lyon.fr/exl-doc/TH_T1868_vpauchard.pdf.
Texto completo da fonteThe fatigue behaviour of unidirectional glass/epoxy composites under longitudinal bending or tensile loading is known to be largely dominated by the delayed fracture of the fibre reinforcement. Often refereed as stress corrosion cracking (SCC), these processes are controlled by the sub-critical growth of glass surface defects under the combined action of stress and moisture. On this basis we have conducted a multi-scale analysis on the early stages of damage development: (i) a statistical model of Stress Corrosion Cracking have been validated during tensile tests on dry fibres bundles by means of Acoustic Emission; (ii) the same model have been applied to an elementary volume within a flexural beam by means of in situ optical observations; (iii) an empirical relationship between the number of fibre breaks on the tensile side in front of the loading nose and the relative stiffness of the specimen allowed us to propose an analytical approximation of the stiffness loss of flexural beams under static or quasi-static loading; (iv) potential and limitations of this approach for dynamic fatigue were investigated in immersion in hot water. It appeared that our model allowed to take into account of thermal activation, strain level, solicitation ratio and frequency
Ben, ameur Mariem. "Caractérisation mécanique et suivi par émission acoustique des mécanismes d’endommagement des composites à fibres hybrides lin/carbone". Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1039.
Texto completo da fonteThe use of natural fibers as reinforcement makes it possible to improve the environmental performance of the composite materials as well as their damping properties. Nevertheless, these natural fiber composites have lower mechanical performance than synthetic fiber composites. In this context, this study proposes to develop composite structures with hybrid reinforcement made of flax and carbon fibers. The objective of this hybridization is to find a compromise between the mechanical and dissipative properties. First, the static behavior of flax fiber, carbon fiber and flax/carbon hybrid composites was analyzed. The principal elastic characteristics of a UD ply in plane stresses are thus determined. Moreover, a monitoring and an analysis of the mechanisms of damage were carried out by means of the technique of acoustic emission associated with microscopic observations. In order to better meet industrial needs, the behavior of composites subjected to cyclic fatigue tests must be studied. In fact, the fatigue behavior of these materials with non-hybrid and hybrid reinforcements was analyzed under tensile stress and three-point bending. The influence of hybridization on the fatigue life of these composites has been established. Finally, an experimental study and a finite element modeling of the vibratory behavior of non-hybrid and hybrid composites were carried out. Thus, the role of different fibers, fiber orientations, stacking sequences in vibration damping has been discussed
Monti, Arthur. "Élaboration et caractérisation mécanique d'une structure composite sandwiche à base de constituants naturels". Thesis, Le Mans, 2016. http://www.theses.fr/2016LEMA1023/document.
Texto completo da fonteBio-based composites appear to be very promising alternatives to traditional composites. The use of natural fibres as reinforcement reduces the environmental impact of these materials and their specific properties are significantly increased. In this context, this work focuses on the manufacturing and the mechanical characterization of a bio-based sandwich structure. The skins are made of an innovative thermoplastic resin associated with flax fibres. The core is made of balsa wood. First, quasi-static analyses are performed on the different components. Then, the tensile properties of the composite skins are studied. Moreover, the main damage mechanisms are identified and described by means of the acoustic emission technique. Next, the flexural behavior of the whole sandwich structure is studied. Particular attention is paid to the detection and prediction of the main fracture modes. Moreover, the statistical spreads of the material properties of the balsa core are taken into account. In addition, cyclic fatigue and impact tests are performed to investigate the behavior of this structure under dynamic loads, and to discuss whether or not this material could be suitable for potential semi-structural applications. Finally, experimental analyses of the vibration behavior of composite and sandwich beams are performed. The contributions of the different components to the global damping properties of the sandwich structure are analyzed by means of a finite elements model. This work also compares the properties of this bio-based sandwich to those of traditional materials, in order to benchmark its mechanical performances with a view to further industrial usage
Tamiatto, Cyril. "Conception et analyse du comportement d'un composite à capteur intégré en fibres de carbone pour la détection in-situ des endommagements d'une structure verre-résine". Lille 1, 1998. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1998/50376-1998-419.pdf.
Texto completo da fonteTang, Sui. "Étude de l'endommagement sous sollicitations monotone et cyclique de matériaux composites à matrices 2024 A1 et 2124 A1 renforcées par des fibres SiCw". Compiègne, 1989. http://www.theses.fr/1989COMPI284.
Texto completo da fonteBale, Jefri Semuel. "The damage observation of composite using non destructive testing (NDT) method". Thesis, Paris 10, 2014. http://www.theses.fr/2015PA100067/document.
Texto completo da fonteThe aim of this study is to investigate the damage behaviour of composite material in static and fatigue condition with non destructive testing (NDT) thermography method and supported by acoustic emission and also computed tomography (CT) scan. Thermography and acoustic emission are used in real-time monitoring techniques during the test. On the other hand, NDT observation of tomography is used for a post-failure analysis. In order to achive this, continuous glass fiber composite (GFRP) and discontinuous carbon fiber composite (DCFC) have been used as the test specimens which supplied by PSA Company, France. A series of mechanical testing was carried out to determine the damage behaviour under static and fatigue loading. During all the mechanical testing, thermography was used in real-time observation to follow the temperature change on specimen surface and supported by acoustic emission in certain condition. This study used rectangular shape and consist of specimen with and without circular notches (hole) at the center. The constant displacement rate is applied to observe the effect on damage behaviour under tensile static loading. Under fatigue testing, the constant parameter of frequency and amplitude of stress was explored for each load level to have the fatigue properties and damage evolution of specimen. The tomography was used to confirm the appearance of damage and material condition after fatigue testing. The analysis from the experiment results and NDT observation shown the good agreement between mechnical results and NDT thermography with supported by acoustic emission observation in detect the appearance and propagation of damage for GFRP and DCFC under static loading. Fatigue testing shows that thermal dissipation is related to the damage evolution and also thermography and can be successfully used to determine high cycle fatigue strength (HCFS) and S-N curve of fiber composite material. From post failure analysis, CT scan analysis successfully measured and evaluated damage and material condition after fatigue test for fiber composite material. v
Manaii, Racha. "Étude du comportement mécanique en fatigue et à l'impact du composite lin/ Elium". Electronic Thesis or Diss., Paris, HESAM, 2021. http://www.theses.fr/2021HESAE027.
Texto completo da fonteThe advantages brought by natural fibers in the composite materials sector are multiple: lightness, good specific mechanical properties, competitive cost and reduced environmental impact. In view of these advantages, the interest for these fibers has multiplied the scientific studies concerning them, in particular with regard to the objectives of a sustainable development. However, the use of these materials in structural parts is subject to the knowledge of their long-term behavior and in front of the various dynamic and repetitive loads. In this context, the objective of this thesis is to study the mechanical behavior of a flax fiber composite and Elium® matrix in fatigue and impact. In a first step, this study allowed to determine the mechanical properties of the material in traction and to follow the induced damage by means of microscopic observations and acoustic emission analysis. Then, in order to answer the problem related to the resistance and endurance in fatigue, the experimental campaign carried out allowed an estimation of the LCF/HCF limit and to study the damage in repetitive loading of the material. Finally, the response to low speed impact was studied. Different tools were used to study the impact response. The results also showed a strong potential of repair after impact of the composite, in the absence of fiber rupture, and this thanks to the thermoplastic resin Elium®
Michaux, Aurore. "Amélioration de la durée de vie de composites à matrice céramique à renfort carboné". Bordeaux 1, 2003. http://www.theses.fr/2003BOR12676.
Texto completo da fonteThe goal of this work was to study the influence of parameters characterizing self-healing and layered matrices, which are used to improve lifetime of carbon fiber-reinforced composites. These parameters are the composition, microstructure, as well as the thermomechanical and thermochemical characteristics of each layer constitutive of the layered matrix. The first part of this work deals with (i) the characterization of the reactivity towards oxygen and (ii) the determination of the thermoelastic properties of all the constituants of the composite, including carbon fibers. In the second part, an optimization of the architecture of the layered matrix is proposed from the modelling of the internal stresses distribution and from the elaboration and characterization of model 1D composites. Finally, the last part deals with thermomechanical characterizations of 3D composites constituted by an interlocked carbon fiber preform and a self-healing and layered matrix. An optimization of the matrix architecture is more particularly studied, thanks to lifetime tests performed at high temperature in an oxidizing environment
Chateauminois, Antoine. "Comportement viscoélastique et tenue en fatigue statique de composites verre-époxy : influence du vieillissement hygrothermique". Lyon 1, 1991. http://www.theses.fr/1991LYO10242.
Texto completo da fonteAboissière, Jacky. "Propagation de dommages d'impact dans un matériau composite stratifié à fibres de carbone et résine époxyde". Toulouse 3, 2003. http://www.theses.fr/2003TOU30027.
Texto completo da fonteFoti, Federico. "Effect of the Environment on the Fatigue Behaviour of Textile Organic Matrix Composite Materials for Aircraft Applications". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2017. http://www.theses.fr/2017ESMA0031/document.
Texto completo da fonteIn the next future, the employment of organic matrix/carbon fibre composites (OMC) is foreseen for the realization of “hot” structures: these parts may be subjected, in service, to mechanical fatigue (e.g. fan blades turbo-engines), thermal cycling and thermo-mechanical fatigue (e.g. aircraft structural parts). Though there is a consistent literature concerning the fatigue behaviour of woven composites, the interaction between fatigue and environmental degradation at high temperature has been poorly explored. Coupling between thermo-oxidation effects, mechanical (viscoelastic, viscoplastic) behaviour of the polymer matrix at high temperatures and degradation due to fatigue may be highly detrimental for the material. This work aims at characterizing and modelling - for carbon fibre/organic matrix (polyimide) textile composites – the thermomechanical behaviour, the onset and the development of damage related to cyclic mechanical mechanisms (fatigue) under controlled (temperature and gas) environment.A preliminary study on a cross-ply laminate [02/902]s has been carried out in order to analyse the environmental effect on a model sample. Digital Image Correlation (DIC) and μ-Computed Tomography (μCT) have been used to monitor and characterize the fatigue damage of 2D woven composites for aeronautical applications. The environmental effect on fatigue degradation have been also explored.The long-term aim of the study is to provide experimental and numerical tools to strengthen the understanding and the modelling of mechanics/damage/environment coupling for durability prediction
Ben, Kahla Hiba. "Microfissures et délaminations des composites stratifiés soumis à des chargements quasi-statiques et cycliques". Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0333.
Texto completo da fonteAerospace industry is devoted to improving the aircraft performance while reducing its weight and limiting the emissions. Part of this objective can be accomplished with the use of high-performance long fibre reinforced polymer laminated composites. Being the first mode of damage under loading, intralaminar cracks initiate at the free edge of the off-axis plies and propagate along the respective fibre orientation. While these cracks grow as tunnels and increase in number, at some point two close cracks in plies of different off-axis orientation could intersect forming an envelope with the free edge. As loading continues, local delamination is expected within this envelope. The evolution and interactions of the different damage modes and the accumulation of damage under a specific loading are crucial in order to have a good understanding of the mechanisms and hence an accurate prediction of the mechanical properties´ degradation. This thesis is devoted to initiation and evolution of intralaminar cracking in plies and interlayer delamination in composite laminates. In the first part, quasi-isotropic Carbon Fibre/ Epoxy non-crimp fabric (NCF) laminates were studied under both quasi-static and cyclic loadings. The objective was to develop an efficient testing methodology for statistical damage evolution determination in Fatigue. The sequence of damage occurrences (intralaminar cracks in the different layers, delaminations at the different interfaces) loaded under quasi-static and tension-tension fatigue is first captured. To save characterisation time and costs, a simple model for predicting intralaminar cracking in laminates under cyclic loads was proposed and validated under low stress cyclic loads and low crack density. The model is based on Weibull distribution for the probability of cracking where part of parameters is obtained in quasi-static tests and part in a limited number of cyclic tests. The predictions of dependency of the cracking on the stress and number of cycles are validated against experimental observations of cracking in the 90-plies of quasi-isotropic NCF laminates as well as in tape based cross-ply laminates. In position where intralaminar cracks meet the specimen edge, local delaminations initiate due to the high 3D stress state. The delamination is further assisted by cracks in other off-axis plies, usually linking them. The average delamination length dependence on loading parameters is characterized and linked with the extent of the laminate stiffness reduction, showing using a simple ply-discount analysis that delaminations are the main reason for very large axial modulus reduction. In the second part, local delaminations and their effect on laminate stiffness are analysed using FEM. Expressions for the crack opening displacement (COD) determined using FEM are obtained and a modelling approach based on GLOB-LOC is performed for intralaminar crack case with local delaminations starting from the intralaminar crack. The delamination length is used as a parameter and studies are performed for different materials. Strong effect of delaminations on COD and on the axial modulus of the laminate is found. Finally, the last findings are used to simulate the damaged composite laminate behaviour in 4-point bending test. The bending stiffness of the laminate is significantly reduced by intralaminar cracks with delaminations. An approach, using the concept of the effective stiffness of the damaged ply is used. The so obtained effective stiffness matrix is a function of intralaminar crack density in the ply and the delamination length. The effective stiffness is used to calculate the bending stiffness of the damaged laminate. The laminate curvature calculated in this way is in a very good agreement with the curvature obtained in 3-D FEM simulations of the test with explicitly including cracks and delaminations in the model
Martinez, Figueroa Jésus. "Ténacité dynamique comme indicateur de dommage en fatigue". Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10142/document.
Texto completo da fonteDamage evaluation and safety assessment of the structural integrity of vehicles and civil structures have been subject of increased attention in recent years. Nowadays the precise knowledge of dynamic fracture parameters is essential for safe design of components. The special arrangement of Three Point Bending Split Hopkinson Bar has been adopted as a convenient means of measuring the dynamic fracture toughness. In this work, an analysis of this arrangement is presented by means of Finite Element Analysis whose results are compared with the theoretical background and the experimental results. A number of important aspects are approached. Among them, the history of the mechanical force actually transmitted from the bars to the specimen and the evolution of the dynamic Stress Intensity Factor (SIF) during the tests. Instead of obtaining the force, the velocity on the bar’s end is proposed to feed the Finite Element model. Experimentally, the arrangement is used to measure the dynamic fracture toughness of AISI 304 TIG welding specimens. The results of a number of fatigue damage-free specimens are compared with those of specimens previously subject to fatigue damage. The technique is also used to measure the dynamic fracture toughness of a carbon-epoxy woven composite material, considered as transversely isotropic media. Simplified formulae to obtain this parameter compared with isotropic materials are proposed along with the precise follow of the SIF evolution during the tests
Gauthier, Catherine. "Composites unidirectionnels PET-Verre : relations morphologie, mise en œuvre, propriétés mécaniques". Lyon 1, 1992. http://www.theses.fr/1992LYO10046.
Texto completo da fonteDorvaux, Mariette Moevus. "Mécanismes d'endommagement, émission acoustique et durées de vie en fatigue statique du composite SiCf/[Si-B-C] aux températures intermédiaires (<800 °C)". Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0114/these.pdf.
Texto completo da fonteThe SiC/[Si-B-C]] composite has been developed for specific applications under high temperatures and corrosive environments. The envisioned applications in civil aircraft engine is require very long lifetimes (20 000 h), which cannot be measured experimental y. New methods are thus necessary to predict lifetimes of this composite. This study aims at determining the damage mechanisms limiting the composite's lifetime at intermediate temperatures. The acoustic emission (AE) technique was used to measure the damage kinetics during Static fatigue experiments. A methodology for AE signals clustering has been developed, in order to separate the signals coming from different damage mechanisms: matrix cracking, interfacial deboning sliding fiber failure. This methodology was first drawn up with ae data recorded during experiments on model materials. Then it has been applied and validated in the case of the 3d composite tested at room temperature. Static fatigue experiments were performed at temperatures in the range [450•c-750•c], in order to Determine short lifetimes and to plot a lifetime diagram as a function of the applied stress. The Degradation mechanisms were analyzed. Several damage indicators were measured during the tests: The strain, the elastic modulus and the number of AE signals. A basic criterion has been proposed for Lifetime prediction: it is possible to detect minimum of the acoustic activity, during a static fatigue experiment, at nearly 60% of the time to failure. The AE signals of fiber failures have been successfully identified. The kinetics of fiber failures could be used to model the composite's degradation and to predict lifetimes
Esmaeillou, Bardia. "Approche cinétique du comportement en fatigue du Polyamide 66 renforcé par 30% de fibres de verre". Phd thesis, Paris, ENSAM, 2011. http://pastel.archives-ouvertes.fr/pastel-00603374.
Texto completo da fonteGoutal, Caroline. "Dimensionnement en fatigue en présence de singularités macroscopiques dans un thermoplastique renforcé fibres de verre courtes (PA66GF50) sous chargements uni- et multi-axiaux". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0008.
Texto completo da fonteIn the current environmental context, the automotive industry looks for reducing CO2 emissions while keeping vehicles power. To this aim, a solution is to lighten the vehicles. In this context, this Ph.D. thesis, supported by Solvay Engineering Plastics in collaboration with Vibracoustic, deals with fatigue resistance of injected parts in Polyamide 6.6reinforced by 50% wt. of short glass fibers, and attempts to take into account the effects of multiaxial loadings and geometrical singularities into a fatigue design methodology. The study is conducted for a given conditioning(RH50%,T80°C) representative of the atmospheric conditions experienced by motor mounts. A fully integrated numerical approach from injection simulation to lifetime prediction by a fatigue criterion, named Through Process Modelling (TPM), is used. One TPM specificity lies in the calculation of the local mechanical response at each point of the part from a multi-scale approach considering the matrix viscoelasticity and the fibers orientation due to the injection process. The fatigue criterion selected is a dissipated energy one. It is based on a “Fatigue Indicator Parameter” (FIP) assimilated to the stress-strain loop area in the stationary regime and obtained by post-treatment of mechanical fields at each point of the part.First, the matrix constitutive law is identified by reverse engineering. Then, the question of the discretization to be adopted in the thickness of an injected part is addressed on smooth samples, and the identification strategy of the fatigue criterion is defined. Subsequently, TPM is applied to a large fatigue database, specifically built for the study, and involving samples and loadings with increasing complexity. Uniaxial tension loadings are studied, firstly on smooth samples (with different fibers orientations), then on pipes, and finally on notched samples. Shear loadings on butterfly samples and torsion loadings on pipes are studied. At last, pipes under combined tension-torsion are considered. For each loading and each singularity level, attention is paid to the definition of a volume around the singularity onwhich the FIP should be spatially averaged. The definition relies on the mechanical gradients analysis. The TPM provides thus lifetimes predictions close to experimental ones in most of the studied configurations
Roudet, Francine. "Comportement en flexion trois points avec cisaillement prépondérant de composites verre-époxyde unidirectionnels : sous chargements monotone et cyclique". Lille 1, 1998. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1998/50376-1998-439.pdf.
Texto completo da fonteLaforet, Adrien. "Rupture différée en fatigue statique aux très hautes températures (800° - 1300°) des fils Hi-Nicalon, des composites Hi-Nicalon/Type PyC/SiC et des composites Hi-Nicalon/Type PyC/B4C". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13783/document.
Texto completo da fonteDelayed failure of SiC Hi-Nicalon multifilament tows (500 fibers), minicomposites Hi-Nicalon/type PyC/SiC and Hi-Nicalon/type PyC/B4C was investigated in static fatigue, in air, at high temperatures (900°C – 1300°C) using specific and innovative devices. Static fatigue tests with measure of strain were performed on these materials. The experimental results (lifetime, strain, tensile behavior) have helped to understand and model the mechanisms responsible for the delayed failure at the different scales: - Hi-Nicalon tows rupture is caused by subcritical crack growth mechanism activated by oxidation of free carbon in the fibres. This phenomenon is disrupted by fast oxide SiO2 formation over 900°C: subcritical crack growth kinetic slows down for low stresses because of protective oxide formation which prevents the cracks from oxygen; For high stresses, the lifetime of Hi-Nicalon tows is weaker because of fibers interactions (fiber-oxide-fiber). At last, creep seems to cause the rupture of the tows for stresses over 200 MPa at 1200°C. - Hi-Nicalon/type PyC/SiC minicomposites break by subcritical crack growth slowed down by the SiC matrix and by the SiO2 formation which limit the access of the oxygen to the fibers. Creep occurs at 1200°C but it isn’t responsible of the rupture. - Hi-Nicalon/type PyC/B4C minicomposites break by subcritical crack growth slowed down by the formation of B2O3 oxide at 900°C for high stresses. The rupture is caused by the fast decrease of the diameter of the fibers at the other temperatures and for low stresses at 900°C. The oxidation kinetic of the fibers increases because of the dissolution of silica coating by B2O3 oxide. Analytical modeling was performed to schedule the lifetime of these materials and the variability of the experimental results is studied
Ivanova, Ivelina. "Comportement mécanique de console courte en béton armé renforcée ou réparée par collage des matériaux composites". Thesis, Reims, 2013. http://www.theses.fr/2013REIMS033/document.
Texto completo da fonteThis study deals with mechanical behaviour of strengthening reinforced concrete corbel by bonding carbon fibre sheet and in particular the influence of the number of layers of carbon fiber fabric, the type of strengthening, the orientation of the composite fabric and the type of carbon fiber fabrics .The results show that the performance of the corbel does not increase linearly with the thickness of the composite plate. There is an optimum thickness of the carbon fiber fabrics. In the case of strengthening on both sides of the concrete, there are an optimum number of layers. In the case of fully wrapped strengthening, the most interesting thickness of the composite is three layers. However, the resistance of the strengthening reinforced concrete corbel depends strongly on the bonded surface.The results also show that the behavior of strengthening corbel can be presented in three phases: the overall elastic phase, the phase of crack propagation and the phase of the opening of diagonal cracks. Strengthening the corbel can significantly increase the ultimate strength from 20% to 82 % and the stiffness of the corbel. The failure of the strengthening corbel can be summarized in five modes.Based on the results obtained and the existing models, the ultimate strength of the strengthening corbel or without strengthening, was estimated and analyzed. A model based on damage theory has been developed in this work. The effect of fatigue on the behavior and ultimate strength of the reinforced concrete corbel has also been studied
Barbière, Romain. "Comportement en fatigue et optimisation de l’interface d’un composite tissé chanvre/époxy : effet de l’humidité Influence of moisture and drying on fatigue damage mechanisms in a woven hemp/epoxy composite : acoustic emission and micro-CT analysis". Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0016.
Texto completo da fontePlant fibre composites are an environmentally friendly alternative to traditional composite materials such as fibreglass composites. However, plant fibres are highly hydrophilic in comparison with the polymer matrix. It is therefore necessary to study the influence of moisture on the mechanical behaviour of these eco-materials.In this work, three conditionings were applied. “Ambient” samples were stored and tested in ambient environment. “Wet” samples were immersed in water until saturation and tested in a climatic chamber at RH97. The objective of the “Wet/Dry” conditioning was to study the role of desorption on the mechanical properties of the composite. Woven hemp/epoxy composite samples with two orientations, [(0/90)]7 and [(± 45)]7, were tested in tension and fatigue according to the three conditionings. In situ analyses by acoustic emission and post-mortem analyses by SEM and micro-CT were carried out.Fatigue tests allowed to determine the Wöhler curves for the two orientations and the three conditionings. A phenomenological model was used to simulate the fatigue life of the composite in all configurations. The comparisons showed that the Wet samples exhibit a lower tensile strength than the Ambient specimens and a lower fatigue sensitivity, while the behaviour of the Wet/dry samples is similar to the Wet conditioning one concerning the tensile strength and similar to the Ambient one concerning the fatigue sensitivity. The classification of acoustic events allowed the identification of three clusters, each cluster corresponding to a type of damage (matrix damage, interfacial damage and fibre breakage). For the two orientations, the results showed that the proportion in number and the kinetics of development of each type of damage depend on the level of the maximum applied stress and on the conditioning. Matrix and interfacial damages are largely the most numerous acoustic events for all the configurations. Micro-CT analysis showed that the damage is different depending on the orientation. However, for each orientation, the same type of damage is observed for the three conditionings, at different stages of development: more advanced for the Wet conditioning, intermediate for the Wet/Dry one and the least developed for the Ambient one.The analysis of the yarn/matrix interface adhesion was performed through fragmentation tests realised on monofilament hemp/epoxy specimens. A specific mould was designed and developed to produce these specimens by casting. Acoustic emission monitoring and observations in polarized light allowed a better understanding of the fragmentation phenomenon in this type of material. The Interfacial Shear Strength (IFSS) values were calculated and the interfacial debonding lengths were measured. The results show that the yarn/matrix interface is weakened after drying, with a decrease in IFSS of 33%. To improve adhesion at the interface, treatments with hydrogen peroxide and non-thermal plasma were applied to the hemp yarns. Fragmentation tests showed that IFSS is almost twice as high with the peroxide treatment and three times higher with plasma, compared to untreated specimens. An upscale was made by applying the hydrogen peroxide treatment to the hemp fabric. The tensile and fatigue behaviour of hemp/epoxy composites produced with this treated fabric was studied. The results obtained at this scale are disappointing. Therefore, the non-thermal plasma treatment remains the most promising solution, but applying this technique at the fabric scale is complex and requires the development of a new reactor
Loqmane, Hicham. "Études des champs cinématique et thermique pour l’analyse des effets dissipatifs associés à l’endommagement sous des sollicitations statiques et dynamiques simples et multiaxiales des matériaux composites stratifiés". Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10095.
Texto completo da fonteIn this thesis the original approach for laminated composite materials (glass / epoxy) of developing experimental protocols adapted to test conventional fatigue and self-heating tests in multiaxial for three types of loading: traction, pure shear and combined tensile shear using Arcan mounting. This method has been adapted to rapid determination of damage threshold of laminate composites. These protocols allow to deal with local energy balance and are based on qualitative and quantitative image processing techniques. It combines two image processing techniques: Infrared thermography method and digital image correlation. The Infrared thermography method through 2D smoothing allowsstudying separately dissipative effects which are related to for fatigue damage of the structure and thermoelastic effects accompanying self-heating tests. While the digital image correlation gives access to kinematic fields and estimation of the strain energy locally into play on a loading cycle, and compare it to the energy dissipated. A qualitative study was made under tomography to characterize the mechanisms of damage during fatigue testing for the three types of stress
El, Khoury Rouphaël Samer. "Étude comparative du comportement à l'impact et en fatigue avant et après impact de stratifiés à plis unidirectionnels de type lin/époxy et verre/époxy". Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2024. http://www.theses.fr/2024ESMA0006.
Texto completo da fonteThis study is conducted in an ecological context with the aim of developing new biocomposites. The flax reinforcements used in this work were prepared with a process inspired by the paper industry. Each ply of the composite consisted of a layer of continuous flax yarns maintained by a thin layer of flax mat used as binder. The centrifugal projection of short flax fibres onto the layer of continuous yarns enabled the yarns to be maintained parallel to each other without the need for sewing or weaving. In addition, for some samples, the surface fibrillation process, which is also a process used in the paper industry, was applied to the short flax fibres before they were projected.The objective of this thesis is to study the impact and fatigue behaviour before and after impact of the flax/epoxy composite laminates made of the reinforcement described above. A systematic comparison with glass/epoxy laminates was also carried out. Two stacking sequences were tested: unidirectional [0]8 and cross-ply [0/90]2S. Low velocity impact tests at several energy levels were first applied on the different materials. Post-mortem damage analyses were performed by visual inspections and by microtomography. The results showed that the two stacking sequences of flax/epoxy laminates had a slightly different impact resistance and absorbed more energy than their glass/epoxy counterparts. A finite-element impact model was also developed, enabling, in a preliminary approach, to retrieve the damage distribution across the thickness of the laminate.Subsequently, tensile tests and cyclic (tension-tension) fatigue tests were carried out on non-impacted and impacted samples at 5J. It was shown that impacted flax/epoxy laminates exhibited a decrease in their ultimate tensile strength of 25% for the [0]8 and 28% for the [0/90]2S, while it remained almost unchanged for glass/epoxy laminates. The Wöhler (S-N) curves characterising the fatigue behaviour showed that the [0/90]2S flax/epoxy laminate performed better than the unidirectional one. However, for a given stress value, the fatigue life is longer for the [0]8 composite. A phenomenological fatigue model was applied, enabling a satisfying prediction of the fatigue life of the laminates after impact. Moreover, damage monitoring through interrupted tests coupled with microtomography enabled the analysis of the damage mechanisms involved. Finally, tensile tests up to fracture were conducted on specimens that had undergone one million fatigue cycles without failure. The post-fatigue tensile properties of the impacted cross-ply flax/epoxy laminates were found to be similar to their initial tensile properties just after impact