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Plastskräp har blivit ett global problem på grund av nedskräpning och otillräcklig avfallshantering. Användning av biologiskt nedbrytbart material kan underlätta problemet, även om det inte är en universallösning. Produkter gjorda av biologiskt nedbrytbart material skall ändå till avfallshantering eftersom nedbrytningen kan vara långvarig och variera mycket beroende av omgivningen. Därmed är användningen av biologiskt nedbrytbart material endast berättigat då det är svårt att samla in materialet eller avskilja det från organiskt material. Studiens mål var att undersöka biologiskt nedbrytbara material som kan användas i produkter som fungerar under många olika driftsförhållanden och inte kan återställas efter användning. I den litterära delen av denna studie definieras nedbrytning genom egenskaper och förhållanden som påverkar nedbrytningsprocessen. Nedbrytning av polyestrar och cellulosa och de standardprocessarna som används i nedbrytningsexperimenten betraktades. Standardprocesserna för nedbrytning studerades för att få en klarare inblick i den eftertraktade nedbrytningsgraden och de standardiserade förhållandena för nedbrytningen i olika miljöer. En sammanfattning av olika nedbrytningsexperiment och analysmetoder är också inkluderade för att försäkra att experimenten som utfördes är både giltiga och jämförbara med andra forskningsresultat inom fältet. I detta forskningsprojekt utfördes nedbrytningsexperiment i färskvatten- och hemkompostmiljöer. Målet med projektet var att bedöma ifall materialen kunde brytas ned i ett brett spektrum av miljöer, ifall de var mindre skadliga för naturen än konventionella material som används av dagens industri och för att uppskatta nedbrytningstakten. Nedbrytningstiden var 140 dagar och experimentet utfördes med 10 olika material: betecknade som A-J. Materialen analyserades 8 gånger under nedbrytningsperioden förutom materialen I och J som analyserades en gång efter 140 dagar. Materialen analyserades mekaniskt, strukturellt och termiskt med hjälp av dragprovning, FTIR och DSC. Provernas viktförändring bestämdes också. Nedbrytning observerades visuellt från provernas yta och genom mekaniska prover. Materialen som placerades i hemkomposten visade klara tecken på nedbrytning då färgen hade förändrats och förstärkningsfibrerna hade blivit synliga. Materialen som placerats i hemkompostmiljö visade också klara tecken på tillväxt av mikroorganismer och biomassa som uppstått på ytan av materialen. Sammanfattningsvist, visade materialen B, C och G de mest lovande resultaten med klara tecken på biologisk nedbrytning och de hade en snabbare nedbrytningstakt än de andra materialen som undersöktes. Material D visade klara tecken på biologisk nedbrytning på ytan men dess nedbrytningstakt var uppskattad att vara mycket långsammare. Därmed rekommenderas det att använda material A, B, D och G istället för konventionella icke biologiskt nedbrytbara material. Dessa material har potential att sänka den negativa inverkan och de långsiktiga riskerna av plastskräp för miljön. / Plastic debris has become a global crisis due to littering and misplaced waste management. The use of biodegradable materials can ease the problem, but it is not always the answer. Products made of biodegradable materials are still to be waste managed since biodegradation can be a long process and is highly dependent on the environment conditions. Hence, the use of biodegradable materials is justified only when retrieving the product after use is impossible or prohibitively expensive or separating it from organic matter is difficult. This study was made to investigate biodegradable materials that can be used in products that are operating in broad range of operational conditions and cannot be retrieved back after use in most cases. In the literature part of this study the biodegradation is defined along with properties and conditions that affect the biodegradation process. Biodegradation of polyesters and cellulose, and standards used in the biodegradation experiments were reviewed. Biodegradation standards were studied in order to have a clearer picture of the pursued degree of biodegradation and standardized properties in the biodegradation experiments. Review of different biodegradation tests and analysis methods are included as well to ensure that the experiments performed in this work are valid and comparable with other biodegradation studies.  In this study, the biodegradation experiment was conducted in freshwater and home compost environments. The aim was to determine if the materials were able to biodegrade in wide range of environments, to make sure they are less harmful than the conventional materials used in the industry and to estimate the rate of biodegradation. The duration of the experiments were 140 days with 10 different materials: A – J. The materials were analyzed 8 times during the aging period, except materials I and J, which were analyzed only once after 140 days. The samples were analyzed mechanically, structurally, and thermally using tensile test, FTIR and DSC measurements, respectively. Also, the samples weight changes were analyzed.  The degradation was visually observed from the surfaces of the samples and from mechanical testing in both experimental environments. Home compost environment showed clear signs of biodegradation where reinforcement fibers became visible and changed the color of some of the samples. Also, home compost samples had microorganisms growing on them, and biomass was developing around them. To conclude, material B, C and G had the most promising results with clear signs of biodegradation and had faster estimated biodegradation rate compared with the other studied materials. Material D had signs of biodegradation on the surface as well. However, the biodegradation rate was estimated to be much slower. In conclusion, it is recommended to use the studied materials A, B, D and G instead of the conventional non-biodegradable polymers. These materials have potential to lower the negative impact and long-term risks of plastic debris to the environment.

Ull är en populär fiber och förekommer ofta i mattproduktion. Med hjälp av livscykelanalyser visar ullen vara en av de fibrerna som ligger i toppen av de material som har högst koldioxidutsläpp. Dock finns det en problematik vid beräkning av miljöpåverkan inom ullproduktionen som kan bidra till ett orättvist resultat. Trots det kvarstår faktumet att det finns förbättringar inom ullproduktionen samt att det är viktigt att ta vara på den ullen som annars skulle gått till förbränning. I samarbete med mattföretaget Rugvista undersöker denna studie hur implementering av 60% återvunna fibrer i mattgarn påverkar kvalitén med en målsätting att få in ull i ett cirkulärt flöde. Genom att undersöka detta spanns ett garn med 60% återvunnen ull och 40% konventionell ull på en E-spinner. Syftet var att garnet skulle nå upp de krav som Rugvista ställer på deras garn. Båda garnerna handvävdes därefter i en tvåskaftsbindning med ett inslagsripsutseende och i samma struktur för de skulle kunna bli jämförda med varandra under samma förutsättningar. Garnerna gick därefter igenom ett dragprovstest och de vävda proverna utsattes för ett modifierad martindaletest. Utifrån dragprovstestet påvisade de tillverkade garnet att de krävdes högre kraft för att nå brottspunkten, då majoriteten av protoypgarnerna klarade en kraft på 3500 cN, vilket var max kraften för Rugvistas garn. Dock gick det att se en större variation på brottpunkten till skillnad från Rugvistas garn som var mer enhetligt i deras resultat. I det modifierade martindaletestet gjordes en visuell bedömning på det vävda proverna efter dem hade blivit utsatta för 15 000 varv. Där påvisades referensmaterialet ett bättre resultat då den bevarade sitt utgångs utseende medan prototypen fick noppbildning redan efter 3000 varv samt släppte ifrån sig betydligt mer fibrer. Slutsatsen av studien blev att utifrån testningen visade prototypen att den inte möter den kvalitén som Rugvista ställer på sina mattor. Utmaningen är den korta fiberlängden hos de återvunna ullfibrerna som lätt lossnar från garnet. Studien visar även att de möjligt att tillverka ett tillräckligt starkt garn för att väva mattor i men att det krävs ytterligare forskning för att produktanpassa det till garnets förutsättningar. / Wool is an admired fiber and is frequently utilized in carpet production. According to life cycle analyses (LCA), wool shows to be one of the fibers that ranks highest in carbon dioxide emissions. However, there are challenges when calculating the environmental impact of wool production that contributes to an unfair result. This does not negate the reality that there are some areas within the wool life cycle that needs enhancement, especially when it comes to the utilization of wool that would otherwise have gone to incineration. This study, conducted in collaboration with the carpet company Rugvista, examines how 60% recycled wool fibers in carpet yarn affects the quality with the aim of getting wool into a circular economy. By investigating this, a yarn with 60% recycled wool and 40% conventional wool was spun on an E-spinner. The objective was to produce a yarn that meets Rugvista's quality standards. Both yarns were later handwoven in a weft-faced plainweave structure to allow for a fair comparison. The yarns underwent a tensile strength test, and the woven samples were subjected to a modified Martindale abrasion test. The results from the tensile test, showed that the manufactured yarns required a higher force to reach the breaking point, as the majority of the prototype yarns could withstand a force of 3500 cN, which was the maximum force for Rugvista's yarns. However, the breaking points of the manufactured yarns had a greater variation, unlike Rugvista's yarn, which demonstrated a more consistent result. In the modified Martindale test, visual assessments of the woven samples were conducted after 15 000 cycles. The reference material, Rugvista’s material, retained its original appearance, while the prototype developed a pilling surface after only 3000 cycles and released a remarkable amount of more fibers. The study concluded that the prototype did not meet Rugvista's quality standards for carpets. The primary challenge is the short fiber length of the recycled wool, which tends to detach from the yarn. While the study demonstrates the possibility of producing sufficiently strong yarn for carpet weaving, further research is necessary to optimize the product according to the yarn's characteristics.

The PhD thesis deals with the possibility of performing dynamic tensile tests. For this purpose, Split Hopkinson Pressure Bar Test (hereinafter SHPBT) is used. The basic construction of SHPBT device is designed to perform dynamic compression tests on materials (metals, plastics, and ceramics). The obtained results are deformation stress – strain and strain rate – strain dependences. SHPBT is capable of testing materials at high strain rates up to 10^2 – 10^3 s-1. It was created a special device for dynamic tensile tests of materials at high strain rates. The created device uses the basic construction of SHPBT. The special device is used for testing flat specimens with 2 mm thickness. It was recognized by the Industrial Property Office of the Czech Republic as a utility model with number 23703. The specimens used for dynamic tensile testing were made of austenitic stainless steel (WNr. 1.4301) with 2 mm thickness. The verification of created device was carried out by numerical simulation. The numerical simulation was performed by ANSYS LS – Dyna software.

Notre étude a porté sur la compréhension microscopique des mécanismes de déformation du polyamide 6 (PA6) à l’état massif. Par des traitements thermiques appropriés, on a obtenu un jeu d’échantillons présentant des microstructures semi-cristallines variées, avec différentes formes cristallographiques (allotropes : α, γ ou β), différents taux de cristallinité (de 24 à 35%), différentes périodes de l’empilement des lamelles cristallines (de 7 à 12nm), ceci pour deux masses moléculaires différentes. Les propriétés mécaniques en traction ont été caractérisées au-dessus et au-dessous de la transition vitreuse de la phase amorphe (Tg). Les différents matériaux présentent des différences notables de comportements. Le taux de cristallinité semble être le facteur prédominant au-dessus de Tg, mais d’autres facteurs sont à prendre en compte en dessous de Tg, comme la forme cristalline et la morphologie lamellaire (épaisseur et facteur de forme). Grâce à un dispositif expérimental fabriqué sur mesure, des essais de traction ont été suivis par diffusion des rayons X aux petits (SAXS) et grands angles (WAXS) sur la ligne D2AM, ESRF, pour caractériser les déformations à l’échelle des empilements lamellaires et à l’échelle de la maille cristalline. Dans les échantillons présentant principalement de la phase cristalline β, les lamelles tendent à s’orienter perpendiculairement à la direction de traction (TD). Ce mécanisme d’orientation local (que nous appelons « modèle de réseau de chaînes ») est induit par la transmission des contraintes par les chaînes amorphes reliant les lamelles cristallines adjacentes. L’allongement local est plus faible que l’allongement macroscopique dans les lamelles perpendiculaire à TD, ce qui implique que les lamelles inclinées doivent être cisaillées. De plus, la phase β se transforme en phase α aux fortes extensions. Dans les échantillons présentant principalement de la phase α (la plus rigide), au-dessus de Tg, dans le régime élastique, les chaînes tendent d’abord à s’orienter perpendiculairement à TD, ce qui implique que les lamelles s’orientent parallèlement à TD (« modèle de lamelles rigides »). Ensuite, dans le régime plastique, une majeure partie des lamelles se réoriente perpendiculairement à TD, comme dans le « modèle de réseau de chaînes », tandis qu’une fraction mineure reste orientée parallèlement à TD. Une morphologie fibrillaire fortement orientée est finalement obtenue pour tous les échantillons quelle que soit la température. / Mechanical properties of bulk polyamide 6 (PA6) have been studied in relation to microscopic deformation mechanisms. By applying various thermal treatments, sets of samples with different semi-crystalline microstructures, namely various crystalline allotropic forms (denoted α, γ and β) and different values of the crystallinity index (from 24 to 35%) and of the long period of the lamellar stacks (from 7 to 12 nm), have been obtained, for two different molecular masses. Mechanical properties have been measured in the linear (viscoelastic) and nonlinear (plastic) regimes below and above the glass transition of the amorphous phase (Tg). Differences of behavior have been observed depending on the microstructure. While the crystallinity index seems to be the predominant factor affecting the mechanical behavior above Tg, other structural parameters such as the crystalline form and the lamellar morphology (thickness and aspect ratio) have to be taken into account below Tg. Deformations at the scales of lamellar stacks and of the crystalline unit cell have been characterized by small and wide angle X-ray scattering (SAXS and WAXS) performed in-situ during tensile tests. In samples with predominantly β phase, lamellae tend to orient perpendicular to the tensile direction (TD). This orientation mechanism (which we denote as ‘Chain Network model’) is driven by the amorphous chains which transmit the stress between adjacent lamellae. The tensile strain in lamellar stacks perpendicular to TD is lower than the macroscopic tensile strain, which must be compensated by increased shear in inclined stacks. Also, at high extension ratios, the β phase transforms into α phase. In samples with predominantly α phase and above Tg, morphology changes are more complex. In a first step, chains orient perpendicular to TD, which implies that lamellar planes tend to orient parallel to TD, possibly due to their high aspect ratio (denoted as ‘Rigid Lamella’ model). In a second step, beyond the yield, a major fraction of crystallites then reorients normal to TD, i.e. chains themselves become parallel to TD, while a minor fraction remains oriented along TD. A highly oriented fibrillar morphology is ultimately obtained in all cases.

Les verres métalliques ont commencé à être produit dans les années 1960 et sous forme massive dans les années 1980. De nombreuses études se sont intéressées à ces matériaux sous leur forme amorphe et ont conclu qu’ils avaient une forte résistance mécanique mais présentaient un comportement très fragile. Dans le cadre du projet EDDAM débuté en 2011, ces matériaux ont été introduits sous forme de petites sphères dans une matrice d’aluminium. Le premier objectif de notre étude est de voir si le verre métallique sous cette forme permet de le rendre peu fragile. Le second objectif est de trouver une alternative aux renforts céramique dans les composites à matrice métallique qui présentent une faible cohésion à l’interface matrice/inclusion. Dans le but de caractériser l’endommagement dans des nouveaux composites amorphe-cristallins métalliques, la tomographie aux rayons X a été utilisée. Cette technique permet de caractériser de manière non destructive l’endommagement des matériaux et de le visualiser en 3D. Cela apporte une contribution à l’étude des matériaux composites par rapport aux techniques classiques utilisées. L’objectif général de cette thèse a été d’étudier l’endommagement en termes d’amorçage, de croissance et de coales- cence des matériaux composites amorphe-cristallins métallique par tomographie aux rayons X lors d’essais de traction monotone in situ. Les matériaux sélectionnés sont constitués d’une matrice aluminium ("molle" de type 1070A ou "dure" de type 5083) et de renforts en verre métallique Zr57Cu20Al10Ni8Ti5 de taille peu dispersée et répartis de manière homogène, avec différentes fractions volumiques (1%, 4% et 10%). Les matériaux composites ont été élaborés par la voie de la métallurgie des poudres au Spark Plasma Sintering (SPS) suivi d’une étape d’extrusion à chaud. Une attention particulière a été portée sur la caractérisation microstructurale des constituants de base. L’analyse qualitative a permis de comparer l’ensemble des composites fabriqués au SPS et ceux extrudés à chaud après SPS. Les différents modes d’amorçage de l’endommagement ont été observés ainsi que la croissance et la coa- lescence amenant la rupture des composites. L’analyse quantitative a été essentiellement consacrée au premier stade de l’endommagement. La croissance et la coalescence étant très rapide, il a été difficile de les suivre lors des essais interrompus. La modélisation d’un composite amorphe-cristallin métallique à matrice molle a été introduite dans le but de reproduire l’endommagement observé lors des analyses expérimentales. Cette première approche nécessite d’être approfondie dans le but de prédire, compte tenu des propriétés mécaniques des différentes phases et de la fraction volumique des renforts, le mode d’endommagement préférentiel apparaissant dans les composites étudiés. Elle montre cependant les prémices d’une modélisation innovante basée sur la microstructure expérimentale. / Metallic glasses have been produced in the 1960s and bulk metallic glasses in the 1980s. Many studies, focused on these materials in their amorphous state, concluded that they had high mechanical strength but shown low ductility. As part of EDDAM project that started in 2011, these materials were introduced as small particles in an aluminum matrix. The first objective of this study is to see if the metallic glass is less brittle in this form. The second objective is to find an alternative of ceramic reinforcements in metal matrix composites. These materials have low cohesion at the matrix/inclusion interface. In order to characterize the damage in new amorphous-crystalline composite, X-ray tomography was used. This allows to characterize damage in materials and to obtain a 3D viewing. The main objective of this thesis was to study damage (nucleation, growth and coalescence) in composite materials using X-ray tomography during tensile tests. Selected materials are constituted of an aluminum matrix and small metallic glass reinforcements (Zr57Cu20Al_10Ni8Ti5). Composites with different volume fractions (from 1vol.% to 10vol.%) were prepared by Spark Plasma Sintering (SPS) and hot extrusion. A particular attention was paid to the microstructural characterization of the basic constituents. Qualitative analysis was used to compare SPS composites with SPS plus hot extrusion composites. Damage nucleation, growth and coalescence were observed. Quantitative analysis was mainly devoted to the first damage step. Growth and coalescence were difficult to follow due to fast rupture and interrupted tensile tests. The modeling of an amorphous-crystalline composite has been introduced in order to reproduce experimental damage analyses. The first approach requires further investigation to predict damage with different volume fractions. However, this part shows the beginning of an innovative model based on the experimental microstructure.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-25T15:51:00Z No. of bitstreams: 1 FRANCISCO GALDINO JÚNIOR - DISSERTAÇÃO PPGEM 2014..pdf: 6213176 bytes, checksum: 50d50ccb2736f335fb4e52475cb149f7 (MD5) / Made available in DSpace on 2018-04-25T15:51:00Z (GMT). No. of bitstreams: 1 FRANCISCO GALDINO JÚNIOR - DISSERTAÇÃO PPGEM 2014..pdf: 6213176 bytes, checksum: 50d50ccb2736f335fb4e52475cb149f7 (MD5) Previous issue date: 2014-08-28 / O crescente desenvolvimento de materiais compósitos reforçados nos últimos anos tem propiciado novas alternativas para solucionar diversos problemas acerca da necessidade de novos materiais com combinações de propriedades. Para utilizarmos tais materiais, devemos realizar vários ensaios mecânicos, como: tração, compressão, flexão e principalmente de impacto. Para isso, foram realizados estudos específicos sobre materiais compósitos e impactos em estruturas laminadas. Através desses estudos e de um levantamento do estado da arte acerca do projeto de diversas máquinas de impacto por queda de peso, foi projetada e fabricada uma máquina de impacto por queda de peso para materiais compósitos de simples concepção. A máquina desenvolvida possui um intervalo de energia de impacto entre 20J e 96J, obtida através de variação da massa de queda de impacto. Foi desenvolvido também um sistema instrumentação para aquisição da força de impacto e da energia absorvida pelo corpo de prova, além de um sistema anti rebote eletromecânico. Para a validação do equipamento foram realizados ensaios de impacto por queda de peso em placas compósitas de fibra de vidro com 8, 10, 12 e 14 camadas e analisado os danos causados nas mesmas, através de software de análise de imagem. A partir de um software de análise de vídeo foi possível calcular a velocidade de impacto e a energia de impacto nos ensaios e comparar com o método teórico e o instrumentado. / The increasing development of reinforced composite materials in recent years has provided new alternatives to solve various problems about the need for new materials with combinations of properties. For such materials we use, we conduct various mechanical tests, such as tensile, compression, bending and mainly impact. For this, specific studies on composite materials, and impact on laminate structures were performed. Through these studies and a survey of state of the art about the project in several of drop impact weight machines, is designed and manufactured a machine to drop impact weight for composites of simple design. The machine has developed a range of impact energy of 20J, and 96J, obtained by varying the mass of the drop impact. One instrumentation system for the acquisition of the impact force and energy absorbed by the specimen was also developed, and an anti rebound electromechanical system. To validate the equipment impact tests were performed by weight loss in composite plates with glass fiber 8, 10, 12 and 14 layers and analyzed the damage caused in the same via image analysis software. From a software video analysis it was possible to calculate the impact velocity and impact energy in the tests and compare with the theoretical method and instrumented.

Le dimensionnement des joints collés est une préoccupation majeure du CNES pour lesapplications spatiales des futurs lanceurs. Pour dimensionner une structure collée, il est nécessaire depouvoir apprécier les caractéristiques mécaniques du joint collé.Dans cette étude, trois adhésifs structuraux ont été sélectionnés (Hysol®EA 9321, Hysol®EA9394 et Hysol EA® 9395). Après leur caractérisation massique, une étude statistique pour mettre enévidence les effets des différents paramètres (vitesse d’essai, géométrie éprouvette, le degré depolymérisation…) a été entreprise.La deuxième étape a pour objectif de fiabiliser l’analyse des essais de fissuration etd’améliorer la compréhension des mécanismes d’endommagement et de propagation de fissure dansles liaisons collées. Trois types d’essai ont été utilisés, à savoir, l’essai Double Cantilever Beam(DCB), pour l’étude du mode I, l’essai End Notched Flexure (ENF), pour le mode II, et l’essai MixedMode Bending (MMB), pour les chargements en mode mixte I/II. Nous avons développé de nouvellesinstrumentations et méthodologies d’analyse. Pour affiner le protocole de test standard, la techniquedite de « backface strain monitoring » a été utilisée. Elle consiste à positionnées des jauges dedéformation sur les surfaces de l’éprouvette de façon à enregistrer l’évolution du signalextensométrique durant la propagation de la fissure. Cette méthode permet une meilleure estimation dela position front de fissure ainsi que l'étude de la répartition des contraintes le long du joint de colle.La corrélation d'images numériques (DIC) a également été utilisée afin de proposer un nouveauprotocole de calibrage de la longueur de fissure et pour comparer un modèle analytique (poutre deTimoshenko sur fondation élastique) avec les résultats expérimentaux. / Adhesive bonding is being strongly considered in space applications CNES as anadvantageous assembly technique for future launchers. Correct design of adhesive joints is of majorconcern. Aerospace adhesives are tough viscoelastic matrices (special epoxy resins) reinforced withnano-, or microparticles. Extended use of adhesive joints in structural applications is limited due to thedifficulties in predicting in-service performance, frequently leading to over-conservative design.Three structural adhesives (Hysol®EA 9321, Hysol®EA 9394 and Hysol®EA 9395) wereselected. After their bulk characterization, statistical studies to highlight effects of different parameterse.g. speed, test piece geometry, degree of polymerization were undertaken.In the second stage, fracture mechanics tests were effected employing: the double cantileverbeam (DCB) configuration (mode I characterisation), the three point bending end-notched flexure(ENF) (mode II) and the mixed-mode bending (MMB) (combined mode I/II loading). Crack growth inbonded joints was investigated in a novel way. To refine standard test protocol, the backface strainmonitoring technique was used. Strain gauges were used to measure the strain on the exposed skin ofthe adherends during crack onset and propagation. This method allows better estimation of the crackfront position as well as fine investigation of the stress distribution along the bondline and in the crackfront vicinity. Digital image correlation (DIC) was also used to compare analytical models, e.g.Timoshenko beam on elastic foundation model with experimental results.

Cette thèse s’inscrit dans le cadre d’un programme de recherche en collaboration avec l’industrie dont l’enjeu est d’utiliser des composites à matrice céramique (CMC) pour la réalisation d’arrière-corps de moteurs pour l’aviation civile.La première partie de ce travail est consacrée à l’étude des fibres de carbure de silicium (Si-C-O) de première génération. Diverses caractérisations physico-chimiques (analyse chimique élémentaire, MEB, MET, spectroscopie Raman, RMN du solide du 29Si et du 13C, DRX…) ont permis d’établir des relations entre la composition chimique, la structure et les propriétés mécaniques des différentes fibres (Nicalon NL série 100 et 200, et Tyranno LoxM, S, ZMI et AM). Une simulation thermodynamique de la phase amorphe intergranulaire SiCxOy a été proposée en s’appuyant sur des données calorimétriques de la littérature obtenues à partir de verres d’oxycarbure de silicium.La seconde partie de ce mémoire est consacrée à l’élaboration par dépôt chimique à partir d’une phase vapeur (CVD) et à la caractérisation de revêtements d’interphase B-C-N. L’influence des conditions d’élaboration (température, pression, composition initiale des gaz) sur la composition chimique des dépôts, leur structure et leur résistance à l’oxydation sous air sec et ambiant a été étudiée. Enfin, les propriétés mécaniques de ces interphases ont été évaluées et des essais de durée de vie ont été réalisés à l’échelle du microcomposite. / This thesis is a part of a research project in partnership with the industry. The aim of the overall project is to design, develop and manufacture exhaust components made of Ceramic Matrix Composites (CMC’s) for civil aircraft engines.The first part of the work deals with the study of first generation silicon carbide fibres (Si-C-O). Various physical and chemical characterizations (quantitative elemental analysis, SEM, TEM, Raman spectroscopy, solid NMR of 29Si and 13C, X-ray diffraction …) were carried out in order to understand the relation between the chemical composition, the structure and the mechanical properties of silicon oxycarbide fibres (Nicalon NL series 100 and 200, and Tyranno LoxM, S, ZMI and AM). Besides, a thermodynamic description of the amorphous SiCxOy phase based on high temperature calorimetry data from the literature is proposed.The second part is devoted to elaboration, by Low Pressure Chemical Vapour Deposition (LP-CVD), and characterization of hexagonal boron carbonitride (B-C-N) coatings. The chemical composition, structure and oxidation resistance (in dry or ambient air) of the coatings were investigated as a function of the deposition conditions (temperature, pressure, initial gas phase composition). Finally, the use of B-C-N coatings as interphases in CMC’s (i.e. their ability to deflect matrix cracks) was investigated by tensile tests on SiC/SiC microcomposites. Their lifetime in static fatigue was also evaluated at 550°C in room atmosphere.