Дисертації з теми "Composites à fibres – Fibres végétales – Tuyaux"
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Maziz, Ammar. "Analyse des endommagements dans les pipes en matériaux composites." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2021. http://www.theses.fr/2021ENTA0019.
Повний текст джерелаDamage modelling of hybrid composite materials has played an important role in the design of composite structures. Although numerical models for the progressive damage of filament wound hybrid composite pipes such, matrix cracking, delamination, and fiber failure have been developed in the literature; there is still a need for improvement. This thesis aims to develop damage models suitable for predicting dynamic behaviour and intra-laminar and inter-laminar damage in hybrid composite tubes under internal pressure subjected to dynamic loading such as the impact of an external object. Fracture mechanics and continuum damage mechanics approaches were adopted to build the damage model. A detailed analysis was performed to have an overview of all the damage mechanisms until the final failure. Cohesive elements were inserted into the two-dimensional and three-dimensional models to simulate the initiation and propagation of matrix cracking and delamination in cross-layered laminates. The damage model was implemented in the FE code (Abaqus/Explicit) by a user-defined material subroutine (VUMAT). Subsequently, validations based on test/calculation correlations on real subsystems and/or parts were performed. Damage initiation was predicted based on the stress-strain failure criteria, while the damage evolution law was based on the dissipation of failure energy. The nonlinear behavior of the material in shear was also taken into account and validated against experimental/numerical results. The predictions show excellent agreement with the experimental observations
Coroller, Guillaume. "Contribution à l'étude des matériaux composites renforcés par des fibres végétales : cas des composites extrudés à matrice polypropylène." Lorient, 2013. http://www.theses.fr/2013LORIS302.
Повний текст джерелаNatural fibers can replace mineral or synthetic reinforcements in many industrial applications, for automotive or not. Their complex and multi component structure as well as their natural origin lead to higher difficulties in this kind of reinforcement than the usual ones. The aim of this thesis work is give a better understanding of the key parameters to control to get the reinforcement capacity of natural fibers. In a first step we studied the influence of the components on the mechanical properties of an injected polypropylene. This has highlighted the interest in flax fibers for composite's reinforcement. It has also underlined the influence of fiber content and using coupling agent. The comparison between extrusion molding and injection molding bas showed the effect of molding process on microstructure and mechanical properties, injection molding showing a better efficiency. Then we focused on extrusion molding, and we have brought to light that it is possible to extrude polypropylene reinforced with flax fiber that is complying with automotive specifications, but it showed lack stability during extrusion process. The study of flax / talc hybrid composites extruded showed that adding talc particles to flax fibers help to increase mechanical properties and to troubleshoot extrusion issues. Finally, we highlighted that, for both short and long flax fibers, fiber's individualization and dispersion are one of the key parameters to control
Alia, Adem. "Comportement à la rupture d'un composite à fibres végétales." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI016.
Повний текст джерелаThe 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
Cheour, Khouloud. "Analyse du comportement en vibration de matériaux composites à fibres végétales." Thesis, Reims, 2017. http://www.theses.fr/2017REIMS022/document.
Повний текст джерелаThis PhD research work aimed at analysing the free vibration behaviour of non-hybrid and hybrid flax-glass composites. First, a modal analysis approach was developed to study the mechanical and dynamic behaviour of these materials. Their elastic and damping properties were identified from their natural frequencies and a comparison with the traditional composites was carried out. In the second part, a finite element modelling of the damping of non-hybrid and hybrid composites was implemented by considering the classical laminate theory, taking into account the transverse shear effects. Different topics were studied such as the fibres orientation, the stacking sequence, the reinforcement architecture, the choice of the stacking sequence layers for the hybridisation. This analysis resulted in optimising both mechanical and damping performances of non-hybrid composites and hybrid flax-glass composites. In the last part of this work, the effect of water ageing on the dynamical and mechanical properties of non-hybrid and hybrid glass-flax composites was studied. To this end, these composites were subjected to free vibrations at different ageing durations in order to identify the effect of water ageing on their mechanical and damping properties and their evolution with ageing time. Finally, a cycle of ageing until saturation was reached followed by a drying operation, which was carried out to analyse the reversibility of their properties
Bourmaud, Alain Gilles. "Contribution à l'étude multi-échelles de fibres végétales et de biocomposites." Lorient, 2011. http://www.theses.fr/2011LORIS241.
Повний текст джерелаThe depletion of our natural resources as well as the increasing impacts of the society on our environment, involves a necessary modification of composite materials design. Thus, for many industrial products, vegetal fibres could be used to substitute synthetic fibres, as composite materials reinforcement. Due to their hierarchical and multi components structure, the vegetal fibres could be considered, at their scale, as complex composite materials. The purpose of this work is to contribute, at various scales, to the knowledge about the vegetal fibres and the associated composites. First of all, we evidenced the interest of nanoindentation and x-ray diffraction to obtain the mechanical and viscoelastic properties of the cell walls as well as their microfibrillar angles. The second experimental part highlights that the processing of soft water, or dopamine bio mimetic treatments, could significantly improve the division and manualy extraction of under retted flax fibres, or some mechanical properties of elaborated biocomposites. In the last section of this thesis report, we evidenced the influence of various manufacturing processes on the composites and fibres properties as well as those of the recycling on vegetal fibres reinforced composites. We showed a good stabilization of the composites mechanical properties after recycling and an important environmental interest to use a recycled matrix for their elaboration
Liu, Taiqu. "Caractérisation multi-échelle de l'amortissement des matériaux composites à fibres végétales." Thesis, Bourgogne Franche-Comté, 2021. http://indexation.univ-fcomte.fr/nuxeo/site/esupversions/7f465635-2b19-4a9c-8100-84b95d1c4521.
Повний текст джерелаVibration and noise are unavoidable problems in engineering products and daily life. Thus, the knowledge of the damping performances of engineering materials and the factors that affect these properties are highly required. Plant fiber composites (PFCs) have become a new option when considering the compromise between damping and stiffness. Current researches on damping are mainly work at the macroscale and the damping sources and mechanisms in plant fiber composites are complex and not fully revealed. Thus, the main objective of this thesis is to provide a better characterization and understanding of damping in PFCs using various experimental techniques at different scales and on a wide range of frequency. This thesis starts with the review of literature on the damping behavior of PFCs. Then, the influences of many parameters including matrix types, fiber architecture, woven pattern, temperature, frequency and moisture content on the damping properties of PFCs are investigated based on dynamic mechanical analysis (DMA) and modal analysis. Furthermore, a constant amplitude method as well as constant stiffness method are used to map the in situ damping properties at the microscale based on grid dynamic Nanoindentation (DNI). These results are then compared to those obtained from dynamic mechanical analysis and modal test methods. The results from DNI show the contribution of each component (fiber, matrix and interface) on energy dissipation. Finally, the damping properties measured using these three experimental techniques at the three different scales are plotted on a wide frequency and temperature range
Pomel, Catherine. "Contribution à l'étude de matériaux composites renforcés par des fibres de lin." Nantes, 2003. http://www.theses.fr/2003NANT2029.
Повний текст джерелаMerotte, Justin. "Contribution a l'étude des matériaux composites renforcés par des fibres végétales aiguilletées." Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS444.
Повний текст джерелаProposing solutions to produce more efficient and environmentally friendly automotive parts has become a major challenge for tier one suppliers. The work described in this thesis is about understanding and improving composite materials made with commingled plant fibre nonwovens. From the same initial nonwoven, it is possible to obtain very distinct material structures by controlling porosity content. One can then give to the material enhanced acoustic properties with high porosity content (50%) or in the contrary show good mechanical properties by limiting porosities. Material structure will evolve with porosity as well as its mechanical behavior. Thus, as function of porosity, interfacial adhesion of fibre mechanical properties will govern composite mechanical properties. Biocomposite automotive parts are exposed to a large range of climatic environments and their mechanical properties can vary significantly. Indeed, radial stresses are drastically influenced by the reinforcement hygroscopic state. Finally, the idea developing an innovative material structure from compression moulding wastes has helped enhancing material rigidity
Ilczyszyn, Florent. "Caractérisation expérimentale et numérique du comportement mécanique des agro-composites renforcés par des fibres de chanvre." Thesis, Troyes, 2013. http://www.theses.fr/2013TROY0016/document.
Повний текст джерелаIn this thesis, fibres extracted from hemp plant and bio-composites polypropylene reinforced by short hemp fibres was investigated. Experimental studies coupled to numerical modelling have enabled to understand and determined their mechanical behaviour taking into account the geometrical shape, the natural defects and the size of hemp fibres. Microscopic experimental method has enabled to characterize the unitary fibre behaviour independently of fibre bundles. Due to their vegetal origins, hemp unitary fibres and bundles present a complex morphology and structure which have an impact on the mechanical properties of composite. Studies carried out the effect of the growing conditions and hemp variety on the fibre behaviour.For the bio-composite material, optical and macroscopic experimental characterization methods were used in order to determine the behaviour of a polypropylene PP reinforced by hemp fibres. The imaging correlation method is also used to analyse the local behaviour showing the heterogeneity of PP/hemp fibres reinforced material. Moreover, complementary work showed the impact of the fibre distribution and the manufacturing process on the composite properties and the damage initiation and growth
Roussière, Fabrice. "Contribution à l'étude d'un non-tissé de fibres végétales pour le renforcement de matériaux composites." Lorient, 2010. http://www.theses.fr/2010LORIS171.
Повний текст джерелаMarrot, Laetitia. "Contribution au développement de matériaux composites à matrices thermodurcissables biosourcées et renforcées par des fibres végétales." Lorient, 2014. http://www.theses.fr/2014LORIS333.
Повний текст джерелаNowadays, depletion of fossil resources and climate change create a growing awareness of the limits of the environment. To be more respectful towards the environment, it is possible to replace glass fibers by vegetable fibers in the reinforcement of composite materials. Thermoset composite materials are well adapted for applications which require high performances. The purpose of this work is to help the development of thermoset composites reinforced with vegetable fibers. First, we highlighted hemp fibers characteristics and their main microstructural specificities, which make them different from flax. Consequences on hemp fibers of activities related to the harvesting steps like decorticating and retting have been investigated. Then, we found interesting results for the use of biobased epoxy and polyester resins in terms of mechanical performances and adhesion with flax fibers. It has been showed that the hardener nature of the epoxy matrix has an influence on the adhesion with a flax fiber. In the last section, we considered industrial composites reinforced with flax fibers with petrochemical and biobased epoxy matrices. We checked the specifications for the mechanical properties in automotive, railway transport and luxury furniture applications. In spite of several defects, especially porosities, the composites showed satisfying tensile and bending properties. Impact properties remained insufficient though
Saad, Houda. "Développement de bio-composites à base de fibres végétales et de colles écologiques." Thesis, Pau, 2013. http://www.theses.fr/2013PAUU3039/document.
Повний текст джерелаThe integration of natural cellulosic fibers from annual plants and agricultural residues and agro-industrial materials in the development of composite structures and the development of new bio-based adhesives, are now a research field with growing interest. The thesis was conducted within the framework of "Eco-panels" program, which its two main objectives were firstly, to enhance plant fibers of Tunisian origin as alfa, rush and palm leaflets and then to evaluate the potential of Tunisian plant species whose bark is rich in tannins (pomegranate fruit, sumac roots and Aleppo pine trunk). The characterization studies of fibers showed that their densities are less than 1. The calculation of the fiber saturation point (FSP) shows values mostly between 60 and 100 %. We were also able to characterize the impregnation kinetics of water for each of these fibers. The impregnation stabilizes after 24 h of immersion. Rich in minerals (concentrations greater than 1 %), the fibers showed levels of cellulose, lignin and hemicellulose comparable to those generally encountered with wood fibers. The thermogravimetric analysis (TGA) shows that the plant matrices are thermally stable for temperatures below 200 ° C. The colorimetric assay of the polyphenolic composition of tanniferous matrices, the infrared analysis and the structural study of the tannins extract, as well as the calculation of "Stiasny number" show the high content in hydrolysable tannins for pomegranate barks and richness of Aleppo pine trunk barks and sumac roots barks in condensed tannins. The study by TGA of the thermal properties of tannins extracts shows that Aleppo pine and sumac tannins are thermally more stable than those of pomegranate. The formulation made from hexamine and Aleppo pine tannins has the greatest elasticity modulus. While the formulation prepared from pomegranate tannins forms the least dense network. These results were confirmed by the study of the shear strength. The study conducted on fiber-plaster composites (implementation and physico-mechanical characterization of composites) showed that local fiber could be an alternative to imported fibers used currently. A first characterization of the thermal conductivity of insulation panels made from local plant fibers and tannins adhesives shows an average conductivity of 0,106 W / Km
Ringuette, Benoît. "Matériaux composites à base de fibres de chanvre." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28057/28057.pdf.
Повний текст джерелаDalmay, Pierre. "Etude physico-chimique et mécanique de composites à matrice plâtre contenant des fibres végétales." Limoges, 2009. https://aurore.unilim.fr/theses/nxfile/default/53a14d4c-4935-4176-9a4c-f7102d682e0b/blobholder:0/2009LIMO4071.pdf.
Повний текст джерелаThe aim of this work was to study the structural, chemical and mechanical properties of natural fibre reinforced plasters. The interactions at the interfaces between flax or hemp fibres and gypsum were investigated. Natural fibres, especially hemp, delayed the setting of plaster when they were used untreated. Some treatments, for exmple alkali ones, were found to be efficient to reduce the setting times of slurries. The analysis of the compounds washed from the fibres revealed mainly the presence of sugars characteristic of pectins, already known as retarder of hydraulic setting materials, like cement or plaster. Absorption kinetics of different fibres was also measured by NMR relaxometry. Regarding the mechanical properties of the composites, the best results for both elastic properties and flexural strength were obtained for 3%wt of 1 cm long flax fibres. The damaging of the composite was also studied using an acoustic emission technique
Dobircau, Larisa. "Relations structures-propriétés dans les composites 100 % naturels, bio-sourcés, renforcés par des fibres végétales." Rouen, 2011. http://www.theses.fr/2011ROUES016.
Повний текст джерелаOver the last decades the consumption of synthetic polymers and their products increased rapidly and the problems concerning the plastic wastages are now one of the most important limiting factors for its extensive usages. The research efforts are being harnessed in the development of fully biodegradable "green" materials. Among these new materials , plastics resulting from bio-resources in general, and starch in particular, seem to be able to replace polymers resulting from petro chemistry. Thus, the primary goal of this work was to study the effect of the composition of a wheat flour based matrix on the physical properties. By the mean of an extrusion process, we carried out films with different compositions and compared the structures, morphologies, the thermal and mechanical properties obtained. Then, we focused on the valorisation of natural fibres (cotton, flax and bamboo) by their incorporation in our matrix. These fibres were not chosen by hazard, indeed, cotton is resulting from the recycling of fabric cutting, the short flax fibres are a by-product of the production of long fibres and finally the bamboo because this plant can present very fast growths. We could show initially that the matrix composition initially established in a patent can be simplified and improved by the suppresion of certain components like silica, stearate of magnesium and partly the sorbitol. Then, "low-tech" 100 % natural composites (short life time) were carried out by varying the nature of the reinforcement used. In the future, these performances will make it possible to target quite specific markets
Tissandier, Cédric. "Composites microcellulaires : production et caractérisation de structures asymétriques." Doctoral thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25274.
Повний текст джерелаNicollin, Arnaud. "Développement de matériaux composites écologiques à base de résines de tannins et de renforts de fibres végétales." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0086/document.
Повний текст джерелаTannins are plant chemicals that show a good reactivity and so they can replace similar products from oil chemistry. This is the case for condensed tannins that have reactivity mechanism similar to that of the phenol. They have been used for several years in wood glues, but no in depth study have been carried out on their potential in composite manufacturing. The work presented here can be split into three projects aiming at the development of composite materials of high performances using both tannin based resins and natural fibers reinforcement. 1. The first project aims to develop a thermosetting composite based on the same tannin/hexamine resin already as glue for particleboards. A previous study shown that it was feasible but numerous problems needed to be solved in order to obtain a reliable and competitive manufacturing process. 2. The goal of the second project is the study and the development of composites which matrix is based on a copolymer of tannin and furfuryl alcohol. Furanic resins show good properties and their capability to react with phenolic compounds makes them potential candidates for the manufacturing of high performances composites. 3. The last project’s objective is the production of acetylated tannins by using similar methods than that used for lignin, to check if they present the same thermoplastic behavior and if yes, to test them in composite manufacturing
Teymoorzadeh, Hedieh. "Composites and foams based on polylactic acid (PLA)." Doctoral thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/27075.
Повний текст джерелаThis study reports on the production and characterization of natural fiber reinforced polylactic acid (PLA) composites. Foaming PLA and its composites was also undertaken to investigate the effect of injection molding conditions (shot size) and natural fiber (flax and wood flour) content on the final properties of the final products. In the first part, PLA was mixed with flax fiber via extrusion and further processed by injection molding to manufacture the final parts. The effect of flax fiber content (15, 25, and 40% wt.) on the morphological, mechanical, thermal, and rheological properties of the composites was evaluated. In the second step, wood flour (WF) was selected to reinforce PLA. Compounding of PLA and WF was carried out in a twin-screw extruder followed by injection molding to obtain the test specimens. A complete series of morphological, mechanical, thermal, and dynamic mechanical analysis was performed to get a complete evaluation of WF addition (15, 25, and 40% wt.) on the properties. Finally, the last step studied PLA composites with natural fibers for the purpose of foaming. Foaming was carried out using an exothermic foaming agent (azodicarbonamide) via injection molding. Injection foaming proceeded after mixing PLA and natural fibers by extrusion. In this case, the shot size (amount of material injected into the mold: 31, 33, 36, 38, and 43% of the machine capacity) and reinforcement content (15, 25, and 40% wt.) were varied. The characterization included mechanical and thermal properties. The results showed that both flax and wood flour led to increased mechanical properties including flexural modulus and impact strength. Moreover, foaming was also effective for neat PLA and PLA composites, i.e. the overall density of the parts was significantly reduced.
Le, Troedec Marianne. "Caractérisation des interactions physico-chimiques dans un matériau composite à base de phyllosilicates, de chaux et de fibres végétales." Limoges, 2009. https://aurore.unilim.fr/theses/nxfile/default/e24c28f9-a650-4203-a4d0-a9fe7302ca00/blobholder:0/2009LIMO4055.pdf.
Повний текст джерелаIn order to understand the physico-chemical mechanisms governing the interactions between hemp fibres and mineral matrices based on lime and on mixtures of lime and clay minerals, the influence of various chemical treatments of fibres on their surface properties and on macroscopic mechanical properties of mortars were evaluated. Treatment with sodium hydroxide (NaOH) removes various organic components from the surface of the fibres, increases the adhesion forces between the fibre and a colloid made of silica and improves the mechanical properties of the resulting composites for lime and lime/kaolin matrices. An explanation for this behaviour could be linked to an increase of the fibre surface roughness and homogeneity. Other chemical treatments, with Ethylene Diamine Tetra-acetic Acid (EDTA), Polythylene imine (PEI), a saturated lime solution and a calcium chloride solution have no impact on the mechanical properties of the composite material
Khelifi, Hamid. "Matériaux argileux stabilisés au ciment et renforcés de fibres végétales : formulation pour extrusion." Lorient, 2012. http://www.theses.fr/2012LORIS277.
Повний текст джерелаThe main aim of this thesis was to contribute to the study of the extrusion of cement-clay paste and the valorization of local materials in order to produce extruded building bricks. To do this, extrudable cement-stabilized argillaceous materials (kaolin) have been designed. These mix designs comply with actual requirements concerning environmental impacts (use of a significant proportion of clay) and they may be used as building materials. Bio-based fibers (flax fibers) have been incorporated. As for any other type of inclusions, flax fibers modify the rheological behavior of material at fresh state. Furthermore, their hydrophilic character amplifies the changes and has required a specific study. The mechanical perform-ances of the tested mix design and the positive effect of extrusion process as well as the addi-tion of fiber have been characterized. Such as for concrete, the Féret relationship is shown to be able to predict the compressive strength assuming that kaolin acts as a high water demand aggregate. A model for stiff paste ram extrusion incorporating the filtration phenomenon and the frictional behavior of the granular packing has been developed. This model is based on the soil mechanics approach and is able to predict the transition between pure plastic behavior and frictional plastic behavior. Finally, the mechanical and thermal performances of the cho-sen eco-friendly mix designs have been compared to those of traditional building products (concrete blocks, concrete, clay bricks, AAC. . . ). Environmental impacts of these mix design have also been evaluated and compared. It appears from this study that the extrudable cement-stabilized argillaceous materials comply with legislations concerning environmental impacts thermal comfort. They are also able to present an alternative to actual building products
Cuynet, Amélie. "Etude du comportement mécanique à l’impact et en post impact de matériaux composites à fibres végétales." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAA017/document.
Повний текст джерелаThe purpose of this PhD project is to study and analyze the mechanical behavior during the impact and post-impact of plant-fiber based composite materials. The conduct of this thesis requires: The manufacturing and characterization of the materials involved in the study : The materials are composed of plant-fiber fabrics (flax and/or hemp) impregnated with thermosetting resin (epoxy type) or thermoplastic resin (PP or PLA). These are manufactured using the vacuum infusion process or using thermocompression, depending on the resin. The materials are plate-shaped. The mechanical characterization will be performed using static mechanical testing and impact testing with a drop tower (over several energy levels). This will be first conducted on unmodified specimens (unimpacted and unaged, with and without fiber reinforcement) then on degraded specimens (impacted with a known energy and/or aged in humidity and temperature). The characterization of damage: It will, from the analysis of the images associated to the techniques of the acoustic emission, locate and identify the various damage mechanisms that intervene in these materials during different stresses. This study will lead to define the degree of harmfulness of such damage while associating to the approach the influence of microstructural parameters such as the nature of the fiber reinforcement and the components (resin and fibers). The identification of behavioral patterns: It consists in suggesting a method to identify the material parameters of behavioral patterns while taking into account the damage level of the material's microstructure (resin and fiber strands). This study will lead to the implementation of a finite element model updating-like method using experimental databases such as kinematic field measurements. The ultimate purpose is to have reliable and predictive models in order to calculate the structures of such materials in the industry
Fehri, Meriem. "Comportements mécanique et hydrique des composites renforcés par des fibres naturelles et/ou conventionnelles." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC215/document.
Повний текст джерелаThis work aims to study the mechanical behavior of composites reinforced by flax fibers as well as the mechanical and water behavior of hybrid composites. A high porosity rate observed in these materials leads to a degradation of the mechanical properties. Tensile and buckling tests with acoustic emission monitoring have identified the mechanisms of damage that reign in these materials and highlight their chronology appearance. Microscopic observations of fracture facies validated these results. An optimization of the mechanical properties particularly in terms of reducing the porosity rate has been tested by inserting carbon fibers in the structure. The results showed that the position of carbon fibers is essential in the improvement of water and mechanical properties
Ntenga, Richard. "Modélisation multi-échelles et caractérisation de l'anisotropie élastique de fibres végétales pour le renforcement de matériaux composites." Clermont-Ferrand 2, 2007. http://www.theses.fr/2007CLF21759.
Повний текст джерелаNtenga, Richard. "Modélisation multi-échelle et caractérisation de l'anisotropie élastique de fibres végétales pour le renforcement de matériaux composites." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2007. http://tel.archives-ouvertes.fr/tel-00718126.
Повний текст джерелаSurini, Thibaud. "Analyse dynamique de la biodégradation du bois et des composites à base de bois et fibres végétales." Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13848/document.
Повний текст джерелаWood biodegradation is studied in order to understand and quantify the mechanical damage. Wood, and especially maritime pine, is sensitive to a fungal attack that causes a decrease of its strength (compression or fracture resistance), before a weight loss occurs. This requires developing or ameliorating the tools of early detection, such as NMR relaxometry, in order to detect the appearance of a pathogen in wooden structures that are more and more appreciated. Besides, wooden composites are a good alternative to make the material more durable, and are ecologically interesting, as they permit to recycle some element, like plastics. This “green” effect is of main importance, which implies a development of new ways in wood preservation. This thesis, led in a short as well as in a long term scale, also studies the behaviour of wood, impregnated with anhydrides or oils from a vegetal origin, or even heat-treated wood. Not only mechanics is described, so that many phenomena are explained and perspectives are clarified
Barbulée, Antoine. "Compréhension des effets du défibrage sur la morphologie, les propriétés et le comportement mécanique des faisceaux de fibres de lin : étude d'un cοmposite dérivé lin/époxyde". Caen, 2015. http://www.theses.fr/2015CAEN2075.
Повний текст джерелаFlax fibers show interesting mechanical and environmental properties that can promote their utilization for biocomposites. However, the use of plant fibers in structural composite materials is hindered by the lack of knowledge about their composition and structure at nanoscale firstly and secondly by the poor understanding of the relationship between the mode of production of the fibers, the mechanical behavior of the fiber bundles and the mechanical properties of the derived composites. Considering the morphological and microstructural characteristics of flax fibers, new experimental tools and numerical modelling are proposed for analyzing the mechanical properties of ultimate fibers, and then extended to the study of bundles and strands. An essential element of this approach is the ultimate link which assembly, governed by the laws of mechanics, allows better understanding the mechanical behavior of the fiber, in relation to the morphology at different scales, and the composites. This latest advance allows connecting the hydric behavior of flax fiber to residual drying stresses and explaining the effects of decortication treatments, since scutching up to stretching
Charlet, Karine. "Contribution à l'étude de composites unidirectionnels renforcés par des fibres de lin : relation entre la microstructure de la fibre et ses propriétés mécaniques." Caen, 2008. http://www.theses.fr/2008CAEN2012.
Повний текст джерелаThis doctoral dissertation deals with morphological and mechanical characteristics of flax fibres. Indeed, due to their lightness and their good mechanical properties, these fibres are considered as good alternatives for the glass fibres commonly used as reinforcement in polymer composites. At first, sections and longitudinal profiles of flax fibres were observed in order to determine their mean sizes and their scattering and to draw up an internal organisation scheme. Then, tensile tests were then performed on elementary fibres. Their mechanical behaviour displays a typical elasto-visco-plasticity as well as an initial non-linearity which has been attributed to an internal rearrangement of the cell wall constituents. The comparison with other natural fibres and the observation of fibre rupture surfaces allowed to corroborate this hypothesis. The study of fibres issued from two varieties and from different parts of the stems led to the conclusion that the median fibres exhibited optimal dimensions as well as higher mechanical properties than the apical or the basal ones. Finally, unidirectional composites made of flax fibres and polyester were processed by hand lay-up or by compression moulding, with several fibre volume fractions. They were tensile and flexural tested in order to determine their mechanical properties and their damage modes. The results show that flax fibres reinforced composites, in addition to their ecological benefit, are mechanically competitive compared to glass fibres reinforced composites
Sadeghi, Vahid. "Effet des modifications de surface sur les propriétés morphologiques et mécaniques de composites à base de coquille de sarrasin et de polyéthylène." Master's thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/69130.
Повний текст джерелаThis project focuses on the production and characterization of composites based on a thermoplastic polymer (high density polyethylene) and a natural fiber (buckwheat shells) as a valorization of the latter. The samples were prepared with three different compounds. The first part deals with untreated shells used directly in the polymer matrix. The second part deals with the shells treated (mercerization) before their introduction into the polymer matrix, while the final part deals with the shells treated with the addition of a coupling agent(polyethylene grafted with maleic anhydride). All the samples were prepared at concentrations of 10, 20, 30 and 40% by weight of buckwheat shells to compare with the matrix alone (0%). Plates were then made by compression molding to prepare the test specimens. The morphological (scanning electron microscopy), physical (density and hardness) and mechanical (tension, bending and impact) characteristics were measured on the samples produced. Based on the results obtained, it was observed that some mechanical and physical properties were improved, but only by using the alkali treatment in combination with the coupling agent. In general, the best results were obtained for a concentration of 30% by weight.
Jin, Shuai. "Etude de vieillissement du comportement mécanique des agro-matériaux à base de fibres de chanvre." Troyes, 2013. http://www.theses.fr/2013TROY0006.
Повний текст джерелаThe main objective of this work consists to manufacturing the new composite materials based on hemp fibers and to characterizing their mechanical behavior with different aging effects. We started our study by characterizing the tensile behavior of the single hemp fiber, with original state and accelerated aging. Different aging conditions are chosen to study separately the influence of each climatic parameter (relative humidity, temperature and UV) on the mechanical behavior. The experimental results showed that the UV and humidity play a more important role than temperature on the mechanical properties of single fibers. Microscopic observations have allowed to analyzing the evolution of aging degradation of single fibers. The composites PP / Hemp are then manufactured, aged and characterized with different fibre volume fractions. Aging conditions are the same as those of single fibers. According to the results, UV and temperature are most penalizing to the mechanical properties of composite; it is clear that the PP polymer protects well the fibers and lessens greatly the effect of moisture on the fibers. The last part is devoted to the analytical and micromechanical modelling. The obtained results from Hashin-Shtrikman+ and Neerfeld Hill model showed a good correlation with the experimental results
Le, Hoang Tung. "Etude de caractérisation du comportement de composites cimentaires incorporant des fibres courtes de lin." Caen, 2013. http://www.theses.fr/2013CAEN2042.
Повний текст джерелаNowadays, a growing interest is focused on increasing the production of building materials incorporating vegetable fibers. In building material, flax is used in several forms: fibers, shives, etc. Their applications in the concrete are to improve the mechanical, thermal and sound insulation. Materials incorporating plant fibers are part of generic group called agro-materials. The production of cementitious composites with plant depends on a number of parameters such as the mixing ratios, mixing methods, manipulation techniques and mixtures which are very influential on the properties of the composites on the fresh and hardened state. This work, carried out in the Laboratory of Construction Material ESITC Caen and Laboratory of Crystallography of Materials (Crismat, UMR 6508) of Caen, involve in studying the role of flax fibers on the rheology of cement pastes, the microstructure and mechanical properties of composite. The parameters related to fibers are their morphology (length), their mechanical characteristics, their surface condition and their volume ratio. The thesis consists of five chapters. The first is a bibliographic study that present the characteristics of the most commonly used in eco-construction plant fibers with particular attention to the flax fiber. The properties of cement composites incorporating vegetable fibers are presented and discussed in terms of the nature and fiber ratio. Characterization of constituents of the cementitious matrix and fibers is presented in the second chapter. The formulation and preparation of cementitious composite materials are described in detail in order to give an overview on the methods of these materials in typical work. The third chapter focuses on the characterization of flax mortar. The analysis of consistency, setting time and dimensional variation was conducted in order to understand the effects of different mixing parameters and propose an optimization of the implementation. Physical characterization, mechanical and microstructural of flax fibers reinforced composite in the hardened state the subject of the fourth chapter. In the formulation of flax fibers reinforced concrete, the study of consistency on the fresh state and mechanical properties in the hardened state is presented in the fifth and final chapter. The conclusions recalls the main results of the study highlighting the complementarity of different methods and proposes investigation to complete the first work on building materials "flax fibers reinforced concrete. "
Manolas, Christos. "Fractionnement du sorgho à fibre. Extraction et caractérisation des hémicelluloses de la moe͏̈lle. Etude des matériaux composites." Toulouse, INPT, 1993. http://www.theses.fr/1993INPT040G.
Повний текст джерелаCapelle, Emilie. "Conception et fabrication de renforts tissés à base de fibres de lin pour la réalisation de pièces composites à géométries complexes." Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2065.
Повний текст джерелаThis work focuses on the weaving and forming of flax based reinforcements. Before being woven, naturalfibres on the form of finite length bundles (~ 30 mm in average for flax) need to be assembled together in a1D continuous product. The use of roving or slivers without twist is rather recommended for compositeapplications. In a first part, this study focuses on the manufacturing and the use of untwisted rovings treatedwith a bonding agent as well as on the weaving process parameters that may influence the mechanicalproperties and the textile characteristics of the woven fabric. Solutions to prevent roving defects duringweaving are proposed. In a second part, this study investigates the ability to develop composite parts with complex geometrieswithout defect. It focuses on the first step of RTM process which consists in forming dry fibrousreinforcements. An experimental approach is used to identify and quantify the defects. The buckling defectcaused by the bending of tows during the preforming step is particularly investigated. Solutions to realize acomplex shape such as a tetrahedron without any defect from flax based woven reinforcements areproposed. With optimized reinforcement architecture, buckling can be prevented. Another solutionconsisting in optimising the process parameters such as the blank holder geometry or the blank holderpressure to prevent the appearance of buckles from commercial fabrics was also investigated with success
Elouaer, Abdelmonem. "Contribution à la compréhension et à la modélisation du comportement mécanique de matériaux composites à renfort en fibres végétales." Thesis, Reims, 2011. http://www.theses.fr/2011REIMS003/document.
Повний текст джерелаThe composites industry continues to evolve and grow by developing new materials and new technologies. Replacing fossil materials by materials with natural origin (especially vegetable) seems to be one of the most promising. In this context our research is proposed. It is interested to characterize the mechanical behavior of a polypropylene matrix composite reinforced with fibers of Hemp and Wood of Hemp (Chenevotte). The various means and characterization techniques used in this study showed that these new materials have interesting mechanical properties, coming rival those of other conventional composites based on carbon and glass fibers.The experimental static and fatigue tests have revealed many details in comparison with other composite materials. The information help creates a database that can serve as reference for other composites of the same family and vegetable fibers. Mechanisms of damage have been highlighted through mechanical tests (tensile monotonous charge-discharge …) associated with microscopic observations (Scanning Electron Microscope), and tools for damage detection based on emission acoustics. Thanks to this technique, we could improve the quality of the interface fiber / matrix which is a basic parameter for this study and for determining the behavior of composite.Micromechanical modeling has been integrated in this thesis, through the Mori-Tanaka model. The behavior of materials during damage has not been taken into account: only the elasticity has been studied. Using this model, we were able to trace the intrinsic properties of the constituents (the longitudinal modulus of elasticity of the reinforcements: Hemp and Chenevotte)
Cherif, Zine Eddine. "Caractérisation et optimisation d’un pré-imprégné industriel fibre lin/résine époxy pour les matériaux composites." Caen, 2013. http://www.theses.fr/2013CAEN2004.
Повний текст джерелаThis thesis focuses on the characterization and optimization of a prepreg based on epoxy resin and flax fibres. The reinforcement consists of fabrics made by twisted flax yarn. The composites were manufactured by two methods: hot platen press and autoclave chamber. Each material was tested using tensile tests to determine its mechanical properties (elastic and at break). Sorption properties were studied by immersion aging tests. Finally, the damping capacity of the flax/epoxy composite was determined from vibration tests of free beams and was compared with carbon/epoxy, glass/epoxy and kevlar/epoxy composites. A systematic study of the influence of the prepreg manufacturing parameters has been performed. We have studied the effect of the type of reinforcement (woven or quasi-unidirectional), the weaving parameters (yarn diameter, filling rate) and the influence of various textile pretreatments (applied to yarn or fabric). Some models are proposed to overcome the rate of porosity on the mechanical properties as well as on the sorption properties. The aim of this work is to identify the main properties of a range of flax/epoxy prepregs with woven reinforcement, and to establish optimal manufacturing conditions to optimize their performances
Del, Masto Alessandra. "Transition d’échelle entre fibre végétale et composite UD : propagation de la variabilité et des non-linéarités." Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD022/document.
Повний текст джерелаAlthough plant-fiber reinforced composites (PFCs) represent an attractive solution for the design of lightweight, high performance and low environmental cost structures, their development requires in-depth studies of the mechanisms underlying their nonlinear tensile behavior, as well as variability of mechanical properties. Given their multi-scale nature, this thesis aims to contribute, using a numerical approach, to the study of the propagation of behavior across the scales of PFCs. Firstly, the study focuses on the fiber scale: a 3D model of the behavior of the wall is first implemented in an EF calculation, in order to establish the influence of fiber morphology on the tensile behavior. Once the non-negligible impact of the morphology has been determined, a study of the links between morphology, material and ultrastructure and tensile behavior is conducted via a sensitivity analysis in the case of flax and hemp. The second part of the work is dedicated to the composite ply scale. A new stochastic multi-scale approach is developed and implemented. It is based on the definition of an elementary volume (VE) with random microstructure to describe the behavior of the ply. The approach is then used to study the sensitivity of VE behavior to nano, micro and mesoscopic parameters. Sensitivity analysis, conducted via the development of the response on the basis of polynomial chaos, allows us to construct a metamodel of the tensile behavior of the ply
Liang, Shaoxiong. "Etude de comportement en fatigue des composites renforcés par fibres végétales : prise en compte de la variabilité des propriétés." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00841850.
Повний текст джерелаChafei, Sawsen. "Influence de différents traitements sur les comportements rhéologique et mécanique d'un composite cimentaire mortier-fibres de lin." Caen, 2014. http://www.theses.fr/2014CAEN2035.
Повний текст джерелаThe objective of this study is to avoid catastrophic failure of a cement mortar incorporating flax fibers by conferring it an increasing resistance rising with the crack length. The implemented strategy is to improve the fiber-matrix compatibility by adapting the formulation by different treatments applied to fibers and / or matrix. In the first part of this study the effects of these treatments on fiber properties are evaluated by chemical, physical and mechanical characterization of the treated flax fibers versus raw fibers. The treatments applied to the cement matrix are also evaluated. The formulated mixtures, composed of treated fibers and / or matrix with additive were characterized in the fresh state to assess the impact of treatments on the consistency and the setting of the mixture, and the cement hydration. The last part of the work is devoted to analyzing the effects of these treatments on the microstructure, physical and mechanical properties of the cement composites
Di, Mauro Chiara Domenica. "Développement durable des résines & composites biosourcées, recyclables, réparables et reprocessables (3r) à base d'huiles végétales époxydées." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4076.
Повний текст джерелаThe use of renewable biomass is a sustainable solution to replace petroleum resource. The vegetable oils (vo) have a wide availability, biodegradability, and low toxicity. Their functionalization, by epoxidation procedure, can produce cross-linkable monomers. The incorporation of dynamic covalent bonds, by dynamic hardeners, into crosslinked polymer networks is a powerful way to convert thermoset materials into reprocessable materials. The main purpose of this thesis is the synthesis and characterization of evos-based thermosets and bio-composites with recyclability properties. The copolymerization reactions of a series of 12 new evos with an aromatic diacid hardener were investigated through a series of studies starting with the nature of initiator influence, the epoxide/hardener ratio, the evos content in epoxy groups and finalizing with recyclability analysis. The influence of the initiator and the epoxy / hardener ratio were investigated as parameters affecting not only the copolymerization reactions but also the networks mechanical and chemical recycling. The twelve new evos homopolymers or copolymers showed a large variety of properties, from soft to brittle, in strong correlation with the epoxy content of the starting monomers. The synthetized thermosets displayed properties of recyclability, repairability, reshapability (3R) and shape memory. Finally, a selection of evos-based resins were reinforced with flax fibers and PLA woven for the production of reprocessable bio-composites. The synthetized bio-composites showed also recyclability properties, the flax fibers being recuperated after chemical recycling and reused for the production of a second-generation composite
Zhang, Xiaohui. "Manufacturing of hemp/PP composites and study of its residual stress and aging behavior." Thesis, Troyes, 2016. http://www.theses.fr/2016TROY0015/document.
Повний текст джерелаIn recent years composite materials based on natural fibers are more and more used for their new performances. Natural fibers propose attractive environmental, mechanical and thermal properties.In this work, we are firstly interested in hemp fibers. These fibers are already used in the automotive and construction industry. In Europe, these fibers are produced mainly in France and especially in Aube. To develop agro-composites with high performances, we have focused this thesis on hemp woven. We chose to elaborate the plates with hemp woven and a polypropylene matrix (PP) by compression molding. This work allows us to see the influence of elaboration conditions on the mechanical behavior of these agro-composites. This thesis also allows us to see the effect of aging conditions UV and humidity on the performance of these materials. Finally an analysis of residual stresses determined by the hole drilling method is proposed to see their effects on the agro-materials
Lefeuvre, Anaële. "Contribution à l'étude des propriétés des fibres de lin (Linum Usitatissimum L. , variétés Marylin et Andréa) en fonction des pratiques culturales sur le plateau du Neubourg. Fibres destinées au renforcement de matériaux composites." Rouen, 2014. http://www.theses.fr/2014ROUES024.
Повний текст джерелаThis thesis was done in collaboration with the Coopérative de Teillage de Lin du plateau du Neubourg (CTLN) which wants to sell some of their producted fibers for composite reinforcement. The aim was to develop knowledge about the variability of mechanical properties and cell wall composition of flax fibers in function of several cimatic scenarios (2009, 2010, 2011, 2012) and pedologic conditions (Nord/Sud/Est/Ouest) on a restricted geographical area (Plateau du Neubourg, Eure, Haute-Normandie) for two varieties (Marylin/Andréa). The study of mechanical properties and cell wall composition showed that pedo-climatic conditions are the most impactant factors. Nevertheless, an ANOVA statistical analysis revealed that their impacts were in a small range and that it is possible to garrantee minimal values of mechanical properties which are competitive with glass fibre’s one, what ever the year. The analysis of stress-strain curves highlighted the importance of the non-linear TIII behavior and permitted to modelize structural modifications happening inside the cell wall during tensile sollicitations
Thuault, Anthony. "Approche multi-échelle de la structure et du comportement mécanique d'une fibre de lin." Caen, 2011. http://www.theses.fr/2011CAEN2055.
Повний текст джерелаThis PhD thesis deals with the understanding of the flax fibres structure at different scales and the studying of its mechanical behaviour. Indeed, in the context of sustainable development, using plant resources covers several fields of industrial applications including structural eco-composites. At first, seven varieties of flax fibres were compared in terms of morphology (diameter), biochemical composition and mechanical properties. Then, the structural study of the flax fibre dealt with the cell wall layers (number, thickness) and the microfibrils orientation in these layers. The analysis of the stress-strain curves obtained by uniaxial tensile test was used to estimate the elastic, viscoelastic and "plastic" contributions to the global behaviour of the fibre. The orthotropy of its mechanical behaviour has been demonstrated by nanoindentation testing. Finally, these data were used to identify the principal parameters that define the mechanical behaviour of the flax fibre. Thus, simulations of the mechanical behaviour of the fibre have been initiated to propose a phenomenological description
Tephany, Christophe. "Analyse de la formabilité de renforts composites à base de fibres naturelles." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2051/document.
Повний текст джерелаThis study concerns the manufacturing process of composite material from woven flax reinforcement and specifically the preforming stage of the RTM (Resin Transfer Molding) process, with complex geometries. During the process several deformation modes take place and several defects may appear and it is therefore important to understand the mechanisms controlling their appearance. A specific sheet forming bench has been used to characterise the formed shapes at the macroscopic scale (global defects) as well as at the mesoscopic scale (tow strains). Various process parameters (blank holder pressures and reinforcement orientation) and the local tensile strains were measured using an optical method. From the observed defects, the tow buckling, out of plane bending of tows, was particularly investigated as this one is not very much described in the litterature. An experimental setup independent of the forming process was designed to specifically study this defect and to quantify the key parameters controlling its appearance. An interferometric method was proposed to measure the size of the buckles with accuracy and a parametric study (applied tensions, bending angles, orientation and architecture of the reinforcement) has been completed. Within the reinforcement, the tensile behaviour of tows presents strong non-linearities. A finite elements model at the macroscopic scale is proposed to highlight the impact of these non-linearities on the forming modeling results. A sensitivity study under several process conditions has been realized
Puech, Laurent. "Développement de composites polypropylène renforcés par des fibres de chanvre pour application automobile." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT144.
Повний текст джерелаDue to the necessity to find alternatives to fossil resources and to reduce the environmental impacts of human activity, a major research effort is currently ongoing in order to develop and increase the use of biobased products from renewable resources, such as natural fibers, in the design of industrial parts. However, many scientific and technological hurdles have yet to be removed so as to promote these products before we can reliably and durably use these fibers in a demanding technical context as in automotive sector. Thus, improving the quality of the interface between natural fibers and polymer matrix is a major challenge, since it constitutes a condition for satisfying the required mechanical performances, such as stiffness, tensile or impact strengths. In this context, the thesis objective was to develop short hemp fibers with controlled and targeted surface properties. Surface-functionalization solutions have been developed, to be used by industrial processes, with the aim of incorporating these fibers in a polypropylene (PP) matrix. Therefore, hemp fibers have been treated according to various functionalization strategies including the use of grafted polypropylene maleic anhydride (PP-g-MA), organosilanes, an amino acid, isocyanates and a polyurethane. Two treatments processes, with low environmental impact, were compared: the direct spraying of functionalization molecules on fibers and reactive extrusion incorporation of these molecules. Reactive extrusion treatments were more efficient than those performed by spraying in the case of PP-g-MA. Three functionalization lanes have been found to be relevant regarding the mechanical properties targeted: i) using PP-g-MA alone in reactive extrusion; ii) spraying-functionalization of an aminosilane or of an amino acid coupled with the incorporation of PP-g-MA into the reactive extrusion. Based on the development of experimental means and specific analyzes, the study of the impact behavior of biocomposites has shown that hemp fiber reinforced composites allow to absorb more energy than PP / glass composites (at identical reinforcing volume rate) for a similar crack length. Also, a finite element modeling of the impact behavior of the studied composites is propounded
Gouanvé, Fabrice. "Comportement à l’eau d’un composite à matrice polyester insaturé renforcée par des fibres de lin." Rouen, 2005. http://www.theses.fr/2005ROUES006.
Повний текст джерелаNatural fibers have been used as structural materials since prehistoric times. Environmental concerns such as global warming, energy consumption, and the desire to obtain products from renewable sources has led to a resurgence of interest in plant-derived products. Plant fibers are very attractive for composite materials because the fibers have some interesting characteristics. For example, they are cost-effective, renewable, and available in high quantity, have low fossil-fuel energy requirements and can offer good mechanical properties. Natural fibers as flax have attracted attention because of their low cost compared with synthetics fibers such as glass, carbon. The application of flax fibers as reinforcements in composite materials requires a strong adhesion between the fiber and the synthetic matrix. The properties of the fiber-matrix interface are of great importance for the macroscopic mechanical properties. Physical and chemical treatments can be used to optimize this interface. In this study, an autoclave treatment and a cold plasma treatment have been carried out on the reinforcing fibers in order to increase moisture resistance and improve adhesion with the matrix respectively. The analysis of the permeation and mechanical results has shown that plasma treatment improves fiber/matrix adhesion while autoclave treatment reduces water solubility in the fibers. For reinforced composites, therefore, autoclave treatment is more efficient in terms of water permeability and plasma treatment gives better stiffness in terms of mechanical properties. This phenomenon was highlighted by SEM micrographs
Gamon, Guillaume. "Incorporation de fibres végétales dans des matrices thermoplastiques biosourcées et biodégradables par extrusion bi-vis pour la production de matériaux biocomposites moulés par injection." Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0029.
Повний текст джерелаIncorporation of vegetal fibres, differing by their source, their chemical composition and their shape, have been performed by twin screw extrusion in two thermoplastic matrices: the poly(lactic acid) and the thermoplastified wheat flour. These two biobased and biodegradable matrices have also different chemical character and thermo-mechanical properties. Fibre incorporation up to 40 % in weight considerably modified both matrix properties and improved several weaknesses (thermal stability, lack of stiffness…). Miscanthus fibres have been selected as best improvers for properties of both matrices. Materials properties were adjusted with a formulating work (addition of plasticizers) and whole process optimization, until injection-molding. Fibre incorporation in a compatibilized blend of the two matrices was also tested and performed in a one step extrusion process, including flour thermoplasticization, polymer blending and fibre dispersion
Bassoumi, Amal. "Analyse et modélisation du choix des renforts pour optimiser la mise en forme de matériaux composites à base de fibres végétales." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2053.
Повний текст джерелаThis thesis is halfway between the study of the deformability of woven structures and the use of flax fibre as reinforcement of composite materials. The first aim of the study is the experimental characterization of the bending behaviour of tows with different structures made of flax fibres and fabrics with different weaves. Parameters such as relative humidity and the composition (100% flax and commingled tows) were also considered. The second aim of the study is to link the bending behaviour of the fabric to the bending behaviour of its constituent tows. This part starts with the geometric modelling of woven fabrics in order to follow the variation of its section in the bending direction. Mesoscopic modelling allows the analytical calculation of the geometric properties of the fabric in particular its moment of inertia. The results obtained were used in the simulation of the fabrics bending to see how far the behaviour depends on the tows bending behaviour and the moment of inertia. The bending behaviour of the fabric seems to be approached satisfactorily from these two factors. This is verified within the range of lengths considered except for high humidity (in this case, other phenomena must be considered). The study pointed out that the difference between two reinforcements tested experimentally can be predicted numerically. Thus, the fabrics designer will be able to anticipate the experimental bending stiffness of the fabric in order to adapt the weaving to the shape forming. A parametric study of the bending was also achieved in order to deduce the most influential parameters of the fabric for an appropriate weaving
Lam, Thuy Quynh. "Qualification mécanique de composites à base de polymères recyclés et de fibres végétales : caractérisation des mécanismes de rupture par imagerie numérique." Poitiers, 2004. http://www.theses.fr/2004POIT2339.
Повний текст джерелаIn this study, jointly supported by ADEME and Poitou-Charentes region, it is proposed to exploit a mechanical recycling method for plastic wastes by using them as matrices in natural composites. The studied materials are polypropylene (PP), high density polyethylene (PEhd) and spruce fibres. The polymers supplied by Valagro platform (Poitiers) have been recycled up to 20 times. Then, spruce fibres have been added to these polymers with different fibre weight fractions. The analysis of the so-obtained materials has been carried out along two main lines: the study of the microstructural evolution on one hand and the characterization of the mechanical behaviour on the other. The results have displayed the appearance of a ductile-brittle transition in PP during the mechanical recycling and a progressive appearance of crystalline phase with increasing fibre weight fraction. A coupling between strain maps obtained by the digital image correlation method at a crack tip and the simulation by the finite element method has enabled the evolution of some mechanical parameters of the studied materials to be characterized
Vasconcellos, Davi Silva de. "Comportement en fatigue avant et après impact de composites tissés chanvre/époxy." Thesis, Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2013. http://www.theses.fr/2013ESMA0017/document.
Повний текст джерелаThis study focuses on a woven hemp/epoxy composite. Tests were first conducted on its components. They showed that the behaviour of resin impregnated yarn is more representative of the yarn behaviour in the composite than the dry yarn usually studied. These tests were also used to determine the material parameters necessary for the development of a finite element model of a composite ply. This model is based on a simplified representation of the fabric. Variability of properties of the components was taken into account. Strain fields were compared with those measured by the DIC technique on the surface of the composites. Fatigue tests were conducted on composites [0°/90°]7 and [±45°]7. Heating was measured by IR camera; the damage was followed by AE and high resolution camera. Observations were made by microscopy and X-ray microtomography. A detailed analysis of damage mechanisms was performed. A model of S-N fatigue curve was adapted to the studied hemp/epoxy composite. The resistance to impact and the post-impact mechanical behaviour of the [0°/90°]7 hemp/epoxy composite were studied. The results showed the influence of a non-destructive impact on the fatigue life of the composite, and the evolution of the damage was analyzed. It has been shown that the model of S-N fatigue curve can be applied to impacted specimens. It is thus possible to predict the fatigue life of the impacted composite from the tensile strength and fatigue behaviour of the non-impacted material
Tanguy, Morgane. "Contribution à l’étude de matériaux composites à matrice polypropylène et renforcés par des fibres végétales : de la fibre à la pièce automobile." Thesis, Lorient, 2016. http://www.theses.fr/2016LORIS425.
Повний текст джерелаThis thesis was funded by the automotive supplier Cooper Standard to develop auto parts in polypropylene (PP) reinforced with plant fibers. Its major objective is to identify key parameters for obtaining high performance composites and then develop industrially. A great variety of plant cell walls was tested mechanically, critical step for the composite behavior analysis. The selected fibers were then mixed in PP and the study of compounding highlighted its impact on the properties of future composite and the difficulty of mixing plant fibers into a molten matrix. The compounds PP / vegetal fibers were then processed by extrusion and the work carried out has allowed the development of composite reinforced with wood fibers respecting the specifications of Cooper Standard. A comparison between extrusion molding and injection molding has showed the effect of molding process on mechanical properties and microstructure of composites. Unidirectional composites models reinforced with long fibers helped to understand the mechanisms of strengthening of a polypropylene matrix with jute and flax fibers, and highlighted the importance of constituents’ mechanical properties. Unlike injected composites and reinforced by short jute and flax fibers have them, showed the predominance of microstructure, compared with the performance of the fibers, on the mechanical properties of the parts
Corbin, Anne-Clémence. "Développement et analyse multi-échelle de renforts en chanvre pour applications biocomposites." Thesis, Lille 1, 2020. http://www.theses.fr/2020LIL1I021.
Повний текст джерелаThis PhD thesis is a part of the European SSUCHY project (H2020-BBI) which aims to develop 100% bio-based composite materials, in terms of reinforcements and matrices. The objective of this thesis is the development and the multi-scale characterization of textile reinforcement made of flax fibers and hemp fibers. These reinforcements have to meet the requirements of the industrial applications of SSUCHY project. First of all, the work focuses on the development of yarns and rovings with sufficient properties for the manufacturing of the reinforcements by weaving technology. For these yarns and rovings, textile and mechanical properties are studied. At the scale of the fibers, properties are obtained by the “Impregnated Fiber Bundle Test” (IFBT) method. Reinforcements are produced by weaving technology with different types of yarns. The influence of production parameters is analyzed on textiles properties, on bending properties in dry state, on uniaxial tensile properties, on plan shear properties and on shape forming capability. These characterization steps allow to build technical data sheets and to choose the reinforcement whose production parameters enables to meet the requirements of the final composite part in the best possible way. Finally, composite plates are manufactured with some of the reinforcements developed, and characterized with tensile tests. Properties of these biocomposites materials are compared with those of biocomposites reinforce by natural fibers from literature or already available on the market