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Rozprawy doktorskie na temat „Polypropylene fibrous”

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Data publikacji: 6 września 2023

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1

Biyana, Nobuhle Yvonne. "Studies on flax/polypropylene-reinforced composites for automotive applications". Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/d1021150.

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The use of natural fibers as reinforcement in thermoplastics presents an interesting alternative for the production of low cost and ecologically friendly composites. One of the advantages of using natural fibres is their low specific weight, resulting in higher specific strength and stiffness when compared to glass reinforced composites. Natural fibres also present safer handling and working conditions. They are non-abrasive to mixing and can contribute to significant cost reduction. This work is divided into two phases: Phase 1 deals with developing nonwoven mats composites from flax/polypropylene (PP) and evaluating their properties. Flax/polypropylene fibres (at different weight ratios) were processed by needle-punching technique in order to form nonwoven mats. The mats were compression-molded at a temperature of 180oC to form composite materials. The mechanical, thermal and viscoelastic properties of the composites were analyzed. Composites (untreated and silane-treated) were also subjected to varying conditions of temperature and humidity and the tensile properties of the conditioned and unconditioned composites were investigated. The mechanical properties (tensile, flexural and impact) of flax/PP composites were found to increase and reach maximum values at 30 per cent fibre loading and then decrease at higher fibre content. Thermal studies revealed that the composites were stable up to 320oC and samples containing 40 per cent flax fibres were found to exhibit greater thermal stability than neat PP. The dynamic mechanical analyses of the composites showed that the incorporation of flax in the composites resulted in an increase of the storage modulus with a maximum value exhibited by composite containing 40 per cent fibre loading. Composites containing chemically modified fibres exhibited low tensile modulus after conditioning. Phase 2 is based on the investigation of the effect of nano-calcium carbonate (CaCO3) on the properties of two types of polymer matrices: recycled PP and virgin PP. In this case, composites were prepared by melt-mixing and injection molding. The mechanical and thermal properties of the composites were characterized. The tensile modulus of the nano-CaCO3 filled PP (virgin and recycled) composites were found to increase and reach maximum at 30 per cent nano-CaCO3 loading, while the tensile strength decreased with increasing filler content. Thermal studies showed that the nano-CaCO3 filled PP samples exhibited a one-step degradation pattern and are thermally stable up to 450oC. The thermal stability of the samples was found to decrease following the addition of nano-CaCO3. SEM micrographs of the tensile fractured surfaces of composites of the nano-CaCO3 filled virgin and recycled PP revealed the presence of nano-CaCO3 agglomeration.
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2

Jia, Jun. "Melt spinning of continuous filaments by cold air attenuation". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37276.

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Traditionally ultrafine fibers below 1 dpf are produced by extrusion followed by mechanical drawing. A modified melt spinning apparatus with high-speed air nozzle was designed and fabricated to produce continuous polypropylene filaments by cold air drawing only. With this setup, the fiber is quenched and simultaneously attenuated by a symmetric cold air jet. Since the formation of fiber structure is highly dependent on the processing conditions, the new process will provide a unique operation window to study fiber attenuation and structural formation under high-speed cold air drawing. Based on computational fluid dynamics simulation results, a parametric study was carried out under different process conditions which include processing temperature, air velocity and polymer volume flow rate. Effects of changes in processing variables on the fiber diameter, molecular orientation, crystallinity, tensile strength and other properties were studied. Furthermore, a theoretical model was developed to analyze the non-isothermal fiber attenuation mechanisms. The new knowledge obtained in this study would likely yield a new process for producing innovative fiber products.
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3

Kalyankar, Rahul R. "Natural fiber reinforced structural insulated panels for panelized construction". Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2010r/kalyankar.pdf.

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4

Slánská, Petra. "Aplikace termochromních látek v polymerních materiálech". Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216383.

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V textilním průmyslu je v dnešní době veliká konkurence. Každá novinka může znamenat velký zisk. Tato diplomová práce se bude zabývat aplikací termochromních přísad (látka reagující na teplotu změnou své barvy) do polymerní matrice, konkrétně polypropylenu, a jeho další zpracování u výrobce technického polotovaru - výroba vláken. Po výrobě vzorků bude provedeno jejich testování. Porovnají se vlastnosti polypropylenu s a bez termochromních přísad a zhodnotí se, nakolik tyto přísady ovlivňují vlastnosti polypropylenu. Ze získaných výsledků se stanoví možnost využití termochromních přísad v textilním průmyslu.
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5

Badji, Célia. "Vieillissement de matériaux composites renforcés de fibres naturelles : étude de l’impact sur les propriétés d’aspect et sur les émissions dans l’air intérieur". Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3022/document.

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Les biocomposites sont des matériaux renforcés de fibres issues de ressources renouvelables. Ces matériaux sont une solution alternative aux composites renforcés de fibres de verre ou de carbone. En effet, leur légèreté et leurs propriétés mécaniques intéressantes leur confèrent un intérêt grandissant dans les secteurs tels que la construction (terrasse, meubles de jardin) ou l’automobile (panneaux de porte, tableaux de bord). Toutefois, les milieux humides, la température et le rayonnement UV sont des paramètres pouvant compromettre la stabilité physico-chimique des biocomposites. L’objectif principal de cette thèse a été d’évaluer la durabilité des biocomposites sous leurs conditions d’usage principales. Pour cela, ces matériaux ont été exposés pendant une année à l’extérieur (lames de terrasse) et sous vitre pare-brise (tableaux de bord). Les résultats ont montré que, bien que la performance mécanique des biocomposites ait été affectée, celle-ci n’a pas été grandement influencée par le type d’exposition. Par contre, les différences de variations de couleur et de cristallinité différant entre les deux expositions suggèrent des mécanismes de dégradation différents et très dépendants des conditions d’usage.Puisque les biocomposites peuvent être utilisés dans des environnements clos tels que les habitacles d’automobile, ils peuvent être également des sources de polluants dans l’air intérieur. L’étude des émissions de composés organiques volatils (COV) par les biocomposites au cours de leur vieillissement sous vitre pare-brise, a permis de générer des données nécessaires à l’évaluation de l’impact sur la qualité de l’air intérieur de véhicule de ces nouveaux matériaux. Cependant, l’augmentation drastique de la concentration de surface en COV au cours du vieillissement suggère que l’exposition a fortement affecté les biocomposites à cause de la sensibilité des composants structurant les fibres végétales face aux conditions d’exposition.La compréhension des mécanismes de dégradation peut s’effectuer à travers l’interprétation des liens de causalité entre les propriétés mécaniques et de microstructure, les émissions de COV, et l’apparence visuelle. Un traitement statistique par analyse en composantes principales (ACP) a ainsi permis de dégager les relations entre les paramètres quantitatifs.Le vieillissement naturel nécessite souvent une durée d’exposition longue pour apercevoir une dégradation effective des matériaux. De ce fait, le vieillissement accéléré en enceinte de laboratoire est de plus en plus réalisé en industrie permettant un gain de temps. Afin de vérifier la représentativité des mécanismes de dégradation en environnement extérieur par l’enceinte, une étude comparative entre le vieillissement naturel extérieur et un vieillissement accéléré en enceinte a été menée
Biocomposites are fiber-reinforced materials from renewable resources. These materials are an alternative to fiberglass or carbon reinforced composites. Indeed, their lightweight and interesting mechanical properties give them a growing interest in sectors such as building (decking, garden furniture) or automobile (door panels, dashboards). However, humidity, temperature and UV radiation are parameters that can compromise the physicochemical stability of biocomposites.The main objective of this thesis is to assess the biocomposites durability in their main conditions of use. For this purpose, these materials have been exposed for one year outdoors (deck boards) and under windshield glass (dashboards). The results showed that the mechanical performance of biocomposites was affected and greatly influenced by the type of exposure. On the other hand, the differences in color and crystallinity variations that differ between the two exposures suggest different degradation mechanisms that are very dependent on the conditions of use.Since biocomposites can be used in environments such as the passenger cabin, they can also be sources of pollutants in indoor air. The study of emissions of volatile organic compounds (VOCs) by biocomposites during their ageing under windshield glass allowed generating data necessary for the evaluation of the impact on the car indoor air quality of these new materials. However, the drastic increase of VOCs surface concentration during exposure suggests that weathering strongly affected biocomposites due to the sensitivity of the structural components of plant fibers to exposure conditions.Understanding of the degradation mechanisms can be carried out through the interpretation of the causal links between mechanical and microstructural properties, VOC emissions and visual appearance. Statistical treatment by Principal Component Analysis (PCA) revealed the links and relationships existing between the quantitative parameters.Natural weathering often requires long time of exposure for an efficient perception of the materials degradation. Thus, accelerated ageing in laboratory is more and more carried out in industry for time saving. In order to verify the representativeness of the degradation mechanisms occurring during exterior weathering by weathering chambers, a comparative study between the exterior aging and the artificial aging was carried out
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6

Pliya, Bidossessi amen prosper. "Contribution des fibres de polypropylène et métalliques à l'amélioration du comportement du béton soumis à une température élevée". Thesis, Cergy-Pontoise, 2010. http://www.theses.fr/2010CERG0479/document.

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Le but de ce travail de recherche est d'étudier l'effet de fibres de polypropylène et de fibres métalliques sur le comportement du béton soumis à une température élevée. D'une part, les fibres de polypropylène ont été ajoutées au béton pour améliorer sa stabilité thermique, et d'autre part les fibres métalliques ont été ajoutées au béton pour améliorer ses propriétés mécaniques résiduelles. De nouvelles formulations de béton ont ensuite été définies, en utilisant un cocktail de fibres de polypropylène et métalliques, afin d'améliorer à la fois la stabilité thermique et les propriétés mécaniques résiduelles du béton. Quatre familles de bétons ont été étudiées : - bétons témoins sans fibres, - bétons contenant des fibres de polypropylène, - bétons contenant des fibres métalliques, et – bétons contenant un cocktail de fibres de polypropylène et métalliques. Trois rapports eau/ciment sont utilisés : 0.30, 0.45 et 0.61. Les éprouvettes de béton, issues de ces compositions, ont été soumises à des cycles de chauffage – refroidissement de la température ambiante à une température de consigne de 150°C, 300°C, 450°C et 600 °C. La vitesse de chauffage a été fixée à 1 °C.min-1. Les teneurs en fibres étaient de 0.11, 0.17 ou 0.22 % en proportion volumique pour les fibres de polypropylène et de 0.25, 0.38 ou 0.51 % pour les fibres métalliques. Les proportions volumiques de cocktail de fibres étaient de 0.49, 0.60, 0.62 et 0.73%. La stabilité thermique, les propriétés mécaniques (résistance en compression, résistance en traction, module d'élasticité), la porosité initiale et résiduelle des bétons formulés ont été analysées. La perte de masse des éprouvettes lors des différents chauffages a été aussi mesurée.Cette étude expérimentale aboutit à la formulation de bétons dont à la fois la stabilité à haute température et le comportement mécanique après refroidissement sont améliorés
The aim of this study was to investigate the effect of polypropylene and steel fibres on the behaviour of concrete subjected to high temperature. Polypropylene fibres were added to the studied concrete mixes in order to improve the concrete thermal stability. Steel fibres were added to the studied concrete mixes in order to improve the concrete residual mechanical properties. News concretes mixes were then designed by adding a cocktail of polypropylene fibres and steel fibres in order to improve both the thermal stability and the residual mechanical properties of the studied concrete. Four groups of concrete mixes were studied: - concretes without fibres, - concretes with polypropylene fibres, - concretes with steel fibres, and - concretes with a cocktail of polypropylene and steel fibres. Three water/cement ratios were used: 0.30, 0.45 and 0.61. The concrete specimens were subjected to various heating – cooling cycles from the room temperature to 150°C, 300°C, 450°C and 600 °C. The heating rate was fixed at 1 °C.min-1. The amounts of fibres in the concrete were 0.11%, 0.17% or 0.22% in volume for polypropylene fibres and 0.25%, 0.38% or 0.51% in volume for steel fibres. The amounts of fibres in concrete with a cocktail of polypropylene and steel fibres were 0.49, 0.60, 0.62 and 0.73%, in volume. The thermal stability, the initial and residual mechanical properties (compressive strength, tensile strength, modulus of elasticity), the porosity and the mass loss of the studied concrete mixes were investigated.This experimental study shows a way to design a concrete mix in order to improve both the thermal stability and the residual mechanical properties
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7

Haczycki, S. J. "The behaviour of polypropylene fibres in aggressive environments". Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236516.

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8

Soccalingame, Lata. "Étude des scénarios de fin de vie des biocomposites : vieillissement et retransformation de biocomposites PP/farine de bois et PLA/fibres de lin". Thesis, Montpellier 2, 2014. http://www.theses.fr/2014MON20082/document.

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Les matériaux biocomposites, en particulier les composites matrice thermoplastique biosourcée ou non renforcée de charges ou de fibres végétales, connaissent actuellement un essor significatif et présentent pour l'avenir un gisement grandissant de matières en fin de vie. En conséquence, l'étude du comportement de ces matériaux au regard de différents scénarios de fin de vie que sont le recyclage mécanique, le compostage et l'incinération constitue un enjeu scientifique et technologique important. Le premier objectif de cette thèse est d'étudier la fin de vie par retransformation (cycles successifs d'injection et de broyage) de biocomposites à matrice polypropylène (PP) chargé de farine de bois. L'impact de la taille des particules de bois et d'un agent de couplage a été évalué. Une très bonne stabilité mécanique jusqu'à 7 cycles de retransformation a été observée malgré des dégradations des différents composants du matériau. Le comportement face à la retransformation après vieillissement artificiel accéléré ou après une exposition naturelle en extérieur a été étudié. La tendance majeure dégagée est un phénomène de « régénération » des propriétés mécaniques par retransformation, et cela malgré des dégradations importantes après vieillissement. Il a été également été observé que l'ajout de bois a tendance à limiter la photodégradation du PP. Le second objectif est d'étudier la fin de vie de biocomposites à matrice acide polylactique (PLA) renforcé de fibres de lin. L'impact de différents paramètres de formulation, de la technique de mise en œuvre et d'un vieillissement hygrothermique sur la retransformation de ces matériaux a été évalué. Les mêmes phénomènes de « régénération » sont observés, ce qui montre l'effet bénéfique de la retransformation. La fin de vie par compostage et par biodégradation est traitée. Des mesures d'énergies de combustion ont enfin permis d'estimer le potentiel de valorisation par incinération qui serait en lien avec le niveau de dégradation du PLA
Nowadays, biocomposite materials are booming and will be a growing end-of-life issue for the future. They are based on a thermoplastic matrix (oil-based or bio-based) reinforced with vegetable fillers or fibers. Consequently, the study of their end of life through recycling, composting and incineration is a scientific and technologic challenge.The first goal of this thesis is to study the reprocessing end of life (successive injection and grinding cycles) of polypropylene (PP) based biocomposites filled with wood flour. The impact of the wood particle size and a coupling agent was assessed. Thus, a very good mechanical stability was observed up to 7 reprocessing cycles despite some degradation from the material components. Then, the reprocessing after artificial or natural UV weathering was carried out. The major trend is a “regeneration” phenomenon of mechanical properties after reprocessing in spite of strong degradations after UV weathering. Moreover, the addition of wood filler tends to restrain the PP photochemical degradation.The second goal is to study the end of life of polylactic acid (PLA) based biocomposites reinforced with flax fibers. The impact of the composition, the processing technic and humidity weathering on the reprocessing was assessed. Similar “regeneration” phenomena were observed leading to conclude to the beneficial effect of reprocessing. Then composting and biodegradation aspects were investigated. Heat release rate measurements enabled to estimate the incineration potential which could be linked to the PLA degradation rate
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Espert, Ana. "Natural fibres/polypropylene composites from residual and recycled materials". Licentiate thesis, KTH, Fibre and Polymer Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1667.

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Natural fibres fulfil all the requirements in order toreplace inorganic fillers in thermoplastic composites. Naturalfibres are inexpensive, renewable, biodegradable, present lowerdensity and their mechanical properties can be compared tothose of inorganic fillers. However, several disadvantagesappear when natural fibres are used for composites. First ofall, the poor compatibility between the hydrophilic fibres withthe hydrophobic thermoplastic matrix leads to a weak interface,which results in poor mechanical properties. On the other hand,the hydrophilic nature of the fibres makes them very sensitivetowards water absorption, which leads also to the loss ofproperties and the swelling and dimensional instability.

In order to enhance the compatibility fibre-matrix, thefibres were chemically surface modified by five differentmethods: a) graft copolymerisation withpolypropylene-graftedmaleic anhydride copolymer (PPgMA), b)modification by PPgMA during processing, c) modification byorganosilanes, d) acetylation, e) modification with peroxideoligomers. Modified fibres led to improved mechanicalproperties and thermal behaviour when used in composites withpost-industrial polypropylene (PP) containing ethylene vinylacetate copolymer (EVA). Modification with peroxide oligomersshowed very promising results, but modification with PPgMA waschosen for further preparation of composites due to itssimplicity.

Two sets of composites were prepared using two differentpolypropylene types as matrix: virgin polypropylene (PP) andthe above mentioned post-industrial polypropylene (PP/EVA).Four different types of cellulosic fibres were used as fillers:cellulose fibres from pulping, sisal fibres, coir fibres andLuffa sponge fibres. The mechanical properties of thecomposites were dependent mostly on the fibre loading andslightly on the type of fibre. The fibers changed thecharacteristics of the material leading a higher stiffness buta lower toughness.

Water absorption of composites was studied at threedifferent temperatures: 23°C, 50°C and 70°C. Thewater absorption kinetics were studied and it was found thatwater is absorbed in composites following the kineticsdescribed by the Fickian diffusion theory. After absorption, animportant loss of properties was observed, due to thedestruction of the fibre structure due to the waterabsorbed.

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10

Doan, Thi Thu Loan. "Investigation on jute fibres and their composites based on polypropylene and epoxy matrices". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1149143661135-69962.

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- Matrix modification of jute/polypropylene composites with MAHgPP - Fibre surface modification for epoxy/jute composites, including: NaOH treatment, silane coupling agents, epoxy dispersion and their combinations - Investigation the influence of modification on the performance of jute fibre and jute compostites
Untersuchungen zum mechanischen und thermischen Verhalten sowie zur Benetzung von Jute­fasern im Ausgangszustand, nach Entwachsen und nach Oberflächenmodifikation, mit dem Ziel einer Verwendung als Verstärkungsfasern in Verbundwerkstoffen. Untersuchungen zum mechanischen und thermischen Verhalten sowie zur hygrothermischen Alterung von Jute/Polypropylen (PP) Verbunden. Einfluss des PP-Typs, der Modifizierung der Matrix mit Maleinsäureanhydrid gepfropftem PP und des Faservolumengehalts.Untersuchung der Grenzschicht in Jute/Epoxidharz Verbunden in Hinblick auf die mechanischen Eigenschaften nach Alkalibehandlung und Oberflächenmodifikation der Jutefasern. Jutefasern haben gute spezifische mechanische Eigenschaften. Die Einzelfasereigenschaften unterliegen der bei Naturfasern üblichen Streuung der mechanischen Eigenschaften. Im Gegensatz zu konventionellen Verstärkungsfasern (Glas, Carbon) nimmt wachstumsbedingt mit zunehmendem Faserquerschnitt die Festigkeit tendenziell zu. Faseroberflächenbehandlungen verbessern die Benetzbarkeit, erhöhen die thermische Stabilität und reduzieren die Feuchteaufnahme sowie den Diffusionskoeffizient. Jute/Polypropylen-Verbunde Chemische und physikalische Wechselwirkungen zwischen Faser und MAHgPP nach optimierter Kopplerauswahl verbessern in Abhängigkeit vom PP-Typ die Grenzflächenscherfestigkeit und die mechanischen Eigenschaften. Durch Einbeziehen der Grenzflächeneigenschaften können mit einer modifizierten Mischungsregel die Zugfestigkeiten der Verbunde beschrieben werden. Jute/Epoxidharz-Verbunde Faseroberflächenbehandlungen mit Natronlauge, Organosilanen, Epoxiddispersionen und deren Kombinationen führen zu verbesserter Benetzung, reduzierter Wasseraufnahme und verbesserter Haftung sowie verbesserten mechanischen Eigenschaften in Jute/Epoxidharz-Verbunden
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Spear, Morwenna Jane. "Compatibilisation of natural fibres for use in polypropylene matrix composites". Thesis, Bangor University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393546.

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Rols, Sébastien. "Conception d'un composite ciment-fibres de polypropylène ductile et durable". Lyon, INSA, 1996. http://www.theses.fr/1996ISAL0116.

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L'objectif de ce travail est l'élaboration d'un Composite Ciment-Fibres de Polypropylène présentant un comportement mécanique ductile et durable. La première étape est consacrée à la définition de la matrice du composite. Elle montre l'intérêt de l'emploi de polymères synthétiques pour diminuer la sensibilité des composites vis-à-vis de la dessiccation. La comparaison du renfort par des fibres de polypropylène à celui par des fibres de verre justifie le choix des fibres de polypropylène pour obtenir un composite ductile durable. Les mécanismes de renfort avec ce type de fibres sont régis par un mode frictionnel et uniquement influencés par les propriétés intrinsèques de la fibre. Les fibres de polypropylène amènent au composite un comportement mécanique en flexion d'un matériau élastique plastique parfait voire écrouissable. Ce comportement mécanique peut être modélisé par une méthode basée sur la détermination de la loi moment - courbure obtenue à partir des caractéristiques mécaniques du composite en traction et en compression pures, et des équations d'équilibre de la section
The aim of this research program was to develop a Polypropylene Fibre Reinforced-Cement Composite (PFRCC) exhibiting both ductility and durability. The first step focused on the matrix mixture proportioning. This highlighted the potential use of synthetic polymers in order to reduce the composites sensibility to desiccation. An examination of the relative performances of polypropylene and glass as reinforcing fibres showed that polypropylene-based composites presented the best combination of ductility and durability. The bond between the fibre and the matrix is essentially controlled by friction and therefore is only influenced by the intrinsic properties of the fibre. The PFRCC behavior in flexure is that of an elastic-plastic material, showing some strain-hardening. This mechanical behavior can be modelled using a technique based on the moment-curvature law obtained from the mechanical properties of the composite in pure tension and compression, and the equilibrium equations of the section
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Doan, Thi Thu Loan. "Investigation on jute fibres and their composites based on polypropylene and epoxy matrices". Doctoral thesis, Technische Universität Dresden, 2005. https://tud.qucosa.de/id/qucosa%3A24708.

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- Matrix modification of jute/polypropylene composites with MAHgPP - Fibre surface modification for epoxy/jute composites, including: NaOH treatment, silane coupling agents, epoxy dispersion and their combinations - Investigation the influence of modification on the performance of jute fibre and jute compostites.
Untersuchungen zum mechanischen und thermischen Verhalten sowie zur Benetzung von Jute­fasern im Ausgangszustand, nach Entwachsen und nach Oberflächenmodifikation, mit dem Ziel einer Verwendung als Verstärkungsfasern in Verbundwerkstoffen. Untersuchungen zum mechanischen und thermischen Verhalten sowie zur hygrothermischen Alterung von Jute/Polypropylen (PP) Verbunden. Einfluss des PP-Typs, der Modifizierung der Matrix mit Maleinsäureanhydrid gepfropftem PP und des Faservolumengehalts.Untersuchung der Grenzschicht in Jute/Epoxidharz Verbunden in Hinblick auf die mechanischen Eigenschaften nach Alkalibehandlung und Oberflächenmodifikation der Jutefasern. Jutefasern haben gute spezifische mechanische Eigenschaften. Die Einzelfasereigenschaften unterliegen der bei Naturfasern üblichen Streuung der mechanischen Eigenschaften. Im Gegensatz zu konventionellen Verstärkungsfasern (Glas, Carbon) nimmt wachstumsbedingt mit zunehmendem Faserquerschnitt die Festigkeit tendenziell zu. Faseroberflächenbehandlungen verbessern die Benetzbarkeit, erhöhen die thermische Stabilität und reduzieren die Feuchteaufnahme sowie den Diffusionskoeffizient. Jute/Polypropylen-Verbunde Chemische und physikalische Wechselwirkungen zwischen Faser und MAHgPP nach optimierter Kopplerauswahl verbessern in Abhängigkeit vom PP-Typ die Grenzflächenscherfestigkeit und die mechanischen Eigenschaften. Durch Einbeziehen der Grenzflächeneigenschaften können mit einer modifizierten Mischungsregel die Zugfestigkeiten der Verbunde beschrieben werden. Jute/Epoxidharz-Verbunde Faseroberflächenbehandlungen mit Natronlauge, Organosilanen, Epoxiddispersionen und deren Kombinationen führen zu verbesserter Benetzung, reduzierter Wasseraufnahme und verbesserter Haftung sowie verbesserten mechanischen Eigenschaften in Jute/Epoxidharz-Verbunden.
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14

Ismail, Yob Saed Bin. "Structure/property relationships associated with woven glass fibres reinforced polypropylene composites". Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/11902.

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The objective of this work was to examine the effect of thermal history during cooling from the melt on the degree of crystallinity, morphology and as well as the relationship between morphology/thermal history and mechanical properties of a 60:40 weight % mixture of woven glass fibres/PP composites. Mechanical properties studied include low velocity falling weight impact strength, flexural properties (modulus and strength) and interlaminar shear strength (ILSS). However the main focus was low velocity impact strength. The composite laminates were manufactured within a flat mould using a compression moulding press. Three thermal treatments were employed: isothermal crystallization from the melt in the range 106 to 156°C for 10, 30, 60 and 240 minutes in an oven; non-isothermal crystallization from the melt at rates varying from 0.67°C/Min. to 62.4°C/Min; and quenching from 190°C to rzooc and then annealing at 155, 160 and 165°C for one hour. The degree of crystallinity developed in the matrix polymer was determine using differential scanning calorimetry (DSC) and the matrix morphology was examined by reflected light microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). TEM was used for quenched and annealed specimens.
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15

Do, Thi Vi Vi. "Matériaux composites à fibres naturelles / polymère biodégradables ou non". Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENA012/document.

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Les fibres naturelles ont récemment attiré l'attention des scientifiques en raison de leurs propriétés : faible coût, faible densité, renouvelables, biodégradables et non abrasives. Dans cette étude, trois types de fibres de bambou sont étudiées. La modification chimique des fibres par la soude est utilisée pour enlever l'hémicellulose et la lignine. Puis, la surface de la fibre est modifiée par acétylation ou silane avant élaboration de composites PP. Les propriétés mécaniques des composites augmentent avec le diamètre des fibres et avec l'utilisation d'un agent d'ensimage. Des mélanges amidon/PVA/plastifiant/agent de couplage sont également étudiés. Les composites préparés par réticulation avec l'acide citrique ont d'excellentes propriétés mécaniques. La résistance à la traction et la déformation à rupture de ces composite augmentent avec la teneur en PVA. La présence d'argile et de fibres ont toutes deux un effet considérable sur les propriétés mécaniques des composites
Natural fibers have recently attracted the attention of scientists because of their properties of low-cost, low density, renewable, biodegradable and nonabrasive. In this study, three types of bamboo fibers are prepared. Chemical modification of fibers by alkali is used to remove hemicellulose and lignin. Then, fiber surface is modified by acetylation and silane before processing composite materials with polypropylene. As expected, the mechanical properties of the composites increase with the average fibre diameter. Tensile strength and Young's modulus increase when using a coupling agent. Starch/PVA blends are also prepared with glycerol and water as plasticizer. The composite prepared by citric acid crosslinking has excellent mechanical properties. Tensile strength and elongation at break of starch/ PVA composite increase with the content of PVA. The presence of clay and fiber are both found to have considerable effect on the mechanical properties of the composites
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16

Taylor, Mark. "Characterisation of normal and high-strength plain and fibre-reinforced concretes by means of strength, fracture and combined fracture/relaxation tests". Thesis, Cardiff University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365107.

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The main objective of this study was the application of strength, fracture and creep/relaxation tests to plain and fibre-reinforced high-strength concretes. Initially, five grades of concrete were developed and evaluated. Target 28 day compressive strengths were 40,60,80 100 and 120 N/mm2, the latter three being high-strength concretes (HSCs) containing a süperplasticiser and 10% silica fume. The others were normal-strength mixes used for comparison purposes. Each grade was made with 10 mm maximum-sized crushed limestone and gravel coarse aggregates making ten mixes in total. All were required to have sufficiently high workability and stability to accept reasonable amounts of fibre reinforcement. The data reported allows estimates of mix proportions for a range of HSC mixes to be determined. Various amounts of steel and polypropylene fibres were then added to the ten mixes to determine their optimum and maximum practical concentrations. The traditional type of toughness test based on un-notched beams in four-point loading was not employed. Instead, notched beams in three-point loading (equivalent to the RILEM work-of-fracture arrangement) and compact compression specimens were used. Both were tested under closed-loop conditions using crack-mouth opening displacement (CMOD) control. Post-cracking toughness was determined by means of the 15a nd 110to ughness indices given in ASTM C 1018. It was found that though fracture-based tests under CMOD control were an improvement on more traditional techniques, 15 and 110 were too insensitive to allow fibre type and volume to be differentiated. Next, work-of-fracture tests to measure the fracture energy, GF, were carried out on the plain concretes, initially under quasi-static loading. Both load/deflection and load/CMOD curves were recorded. GF showed little change with strength for a given aggregate type. Even though similar grades of crushed limestone and gravel HSCs had different GF values, the measure was still considered unsuitable for characterising the fracture properties of concrete. Similar experiments were then carried out on all ten mixes at five orders of magnitude of test duration (30 seconds to 2 days). GF appeared to be independent of strain rate. Both types of test highlighted the greater suitability of load/CMOD rather than load/deflection curves when evaluating GF. Finally, combined fracture and relaxation tests were undertaken in an attempt to obtain medium term fracture parameters. Though the CMOD was locked at 90,70 and 50% of the peak load in the strain-softening region, the deflection, when measured, showed a noticeable reduction over the seven days of each experiment, suggesting that significant cracking and stress redistribution within the fracture process zone was taking place. This finding has opened up a major area of important future research by confirming that the use of quasi-static fracture parameters in finite element studies is suspect.
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17

Abdennadher, Ahmed. "Injection de Polypropylène Renforcé de Fibres Naturelles : Procédé, Microstructure et Propriétés". Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0045/document.

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Les fibres naturelles sont une alternative aux fibres de verre pour renforcer les polymères. Lors de la mise en œuvre par injection, la taille, l'orientation et la distribution de fibres évoluent en fonction de l'écoulement, et cela conditionne les propriétés des pièces injectées. L'objectif de cette thèse est de caractériser la microstructure de composites à base de deux types de fibres, le lin et Tencel®, et d'établir une corrélation avec leurs propriétés. Les fibres et matrice ont été mélangées en extrusion bivis et les composites obtenus injectés. La rupture de fibres est plus importante lorsque leur concentration augmente. La casse est principalement pendant la phase de mélange. Une nouvelle approche de caractérisation permettant la quantification des orientation, distribution et courbure de fibres a été développée. Les composites présentent une structure cœur-peau dans l'épaisseur de la pièce injectée. Les propriétés rhéologiques des composites ont été étudiées en modes dynamique et capillaire. Les fibres Tencel®, qui sont les plus flexibles, conduisent à une augmentation plus grande des viscosités, modules et seuil d'écoulement. Les propriétés mécaniques en traction et au choc ont été déterminées dans des éprouvettes prélevées dans des boites injectées avec différentes orientations par rapport à l'axe d'écoulement. Les propriétés d'impact des composites à fibres Tencel® sont supérieures à celles à base de lin et de verre. Des modèles ont été testés en prenant en compte l'orientation de fibres. Lors des campagnes d'injection, les pressions sur des capteurs situés dans la cavité ont été mesurées. Les pressions calculées avec le logiciel Rem3D sont en assez bon accord avec la mesure. Le modèle d'orientation de fibre rigide utilisé dans Rem3D donne des résultats corrects pour les fibres de lin, mais il s'est avéré inapproprié pour prédire l'orientation des fibres Tencel® extrêmement flexibles. Ce travail est réalisé dans le cadre de la Chaire Industrielle Bioplastiques financée par Mines ParisTech et Arkema, l'Oréal, Nestlé, PSA et Schneider Electric
Natural fibres are an alternative to glass fibres for reinforcing polymers. During injection, fibre size, orientation and distribution evolve as a function of flow and determine composite properties. The goal of this thesis is to characterize the microstructure of composites based on two types of fibres, flax and Tencel®, and to correlate with composite properties.The composites were prepared by extrusion and injection. Fibre rupture was higher at higher fibre concentrations. There was practically no breakage during injection. A new approach allowing quantification of fibre orientation, distribution and curvature was developed. The composites with cellulosic fibres have core-skin structure along the part thickness. The rheological properties of composites were studied in dynamic and capillary modes. Tencel® fibres, which are the most flexible, showed the highest viscosity, moduli and yield stress. Tension and impact were measured for samples cut from the moulded part at different orientations towards the main flow direction. Impact properties of Tencel®-based composites were the highest compared to flax and glass fibre composites. Models taking into account fibre orientation were tested. Pressure in the mould during injection was recorded. Pressure calculated with Rem3D software showed a reasonable agreement with the experiment. Modelling of fibre orientation with Rem3D gave results comparable with experiment for flax but turned out to be not applicable for Tencel® which are flexible.The work was performed within the Industrial Chair in Bioplastics supported by MINES ParisTech and Arkema, L'Oréal, Nestlé, PSA and Schneider Electric
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18

Richardson, Alan Elliott. "An investigation into the effect of polypropylene fibres on the durability of concrete". Thesis, University of Newcastle Upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500949.

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The problem with understanding the properties of polypropylene fibres in concrete is that there are many types of fibre, with many suggested properties and conflicting claims made by both manufacturers of polypropylene fibres and researchers in the field of material science as to the effects of fibres on compressive strength, flexural strength, post crack performance, absorption reduction and freeze/thaw durability of concrete. From an initial pilot study, utilising standard BSI and ASTM tests and devised non-standard tests, including measurement of grout resistivity an extensive test programme was conductec to determine the effect of polypropylene fibres on the freeze/thaw behaviour of concrete.
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19

Gérard, Pierre. "Maîtrise et optimisation de l'anisotropie et de l'hétérogénéité des composites à matrices thermoplastiques, renforcés de fibres de verre courtes et moules par injection". Lille 1, 1998. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1998/50376-1998-405.pdf.

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L'etude realisee concerne des composites a matrices polypropylene renforces par des fibres de verre courtes ou longues et moules par injection. Il a ete constate que l'anisotropie et l'heterogeneite de ces materiaux sont deux proprietes qu'il est important de prendre en compte lors de la conception de la piece et du moule afin de permettre une meilleure optimisation des potentialites du composite. L'etude parametrique a permis de montrer qu'il est possible par un choix precis des parametres d'injection d'obtenir un materiau dont l'orientation des fibres est parfaitement maitrisee. En retour, l'orientation des fibres perturbe l'ecoulement et modifie le profil d'orientation moleculaire. Ce couplage a pu etre mis en evidence experimentalement par une methode de mesures du rapport dichroique par spectroscopie infrarouge en reflexions internes multiples. Deux modeles micromecaniques ont ensuite ete developpes et permettent de predire avec une precision acceptable, les proprietes mecaniques locales, rigidite et resistance, a partir de la connaissance experimentale ou theorique de l'etat d'orientation des fibres. La mecanique de la rupture en mode i a permis de mettre en evidence l'influence importante de l'orientation des fibres sur les phenomenes de creation et de developpement de fissures, qui se traduit par des variations du facteur d'intensite de contraintes a l'amorcage et pendant la propagation de fissures, et de l'emission acoustique, reflet de l'endommagement du materiau.
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20

Al-Kahtani, Salah Msfir. "The effects of hemp fibres on the mechanical and physical properties of E-glass fibres reinforced polypropylene (Twintex) composites". Thesis, University of Portsmouth, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.530113.

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The main aim of this research is to investigate the mechanical and environmental properties of E-glass/polypropylene (Twintex) composite with and without natural fibres (Hemp) reinforcementA. serieso f lab testsw ere done to explain the impact damage characteristics of the composites were evaluated. The impact of mass applied started with 3.6 Kg and was incremented 3 Kg at a time to a maximum mass of 18.6 Kg. The effect of the impact damage and velocity was found to be significant- within the range of the velocities used. The absorbed impact energy significantly affected the impact performance of the Twintex panels. On the other hand, Twintex panels showed an ability to confine the damage zone and hence, to increase the damage tolerance of the panels. The results of impact were analysed using C-Scan. They significantly show that with the increase of mass the area of damage increases accordingly. The flexural properties of composite samples were evaluated by 3-point bending test methods. In contrast, the loads for sample's deformation in three-point bending test proved to be less when high-impact loaded samples were used. For the samples without hemp, the highest flexural stress was 317.616 MPa and the lowest was 116.552 MPa. The highest flexural modulus was 9937.63 MPa and the lowest was 4439.898 MPa. The effect of the flexural percentage of the load decreases with the increase of mass. The load decrease from sample 1 to sample 7, which indicated a loss in flexural strength by 63.03% and a loss in flexural modulus by 55.32%. With hemp reinforcement the highest flexural stress was found 189.092 MPa and the lowest was 101.763 MPa. The highest flexural modulus was found 10299.37 MPa and the lowest was 2437.73 MPa. The effect of the flexural percentage of the load decreases with the increase of mass. Twintex plus hemp retained 85.81 % of the original flexural strength it means that adding of hemp into the Twintex reduces the strength of the sample by 2.01 %. IV Abstract Tensile test results show the tangent modulus for the Twintex has reach to 1967.79 MPa, however adding hemp into the Twintex decrease the tangent modulus by 1.465% times. This is meant that the Twintex plus hemp makes the material weaker and softer. The Twintex plus hemp will be weaker by 30.765%. The SEM evaluation also shows that by increasing the impact load the state of the damage becomes more severe. There arc more instances of brittle and catastrophic fibre damages with high impact load. The Twintex plus hemp samples gained in weight, as expected, by an average of 2.64%. This 2.64% increase, assuming that the hemp absorbs all the water and not the polypropylene, means that the fibres increased weight by approximately 8.2%. Along with this increase in weight, the fibres also expanded due to the water absorption. After the water bath the samples lost only 2.5% of their flexural strength and an insignificant loss in flexural modulus. The addition of hemp caused a 35.4% reduction in the flexural modulus of the samples. This means that the samples with hemp became more elastic, deforming more than samples without the hemp layers. The effect of water absorption seemed to have little effect on any of the samples, with the largest effect being a 5.4% reduction in water boiled Twintex and hemp samples. Twintex obtains its highest flexural modulus properties from the glass fibres in the matrix. A reduction (35.4%) suggests that the reinforcement properties of the glass fibres are being reduced due to the incorporation of the hemp. This could be due to the hemp fibres taking away matrix material from the glass fibres in the centre of the sample. Creep and Stress relaxation properties of the sandwich panels with and without natural reinforcements were investigated and compared under different temperatures such as 30 °C, 40 °C, 50 °C, 60 °C. Melting point of both materials was determined. These qualitative and quantitative conclusions can be drawn regarding the use of hemp as reinforcement in Twintex sandwich panel.
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21

Renard, Henri. "Etude de l'influence d'un ensimage à base de polypropylène modifié chimiquement sur les propriétés mécaniques des matériaux composites polypropylène - fibres de verre". Lyon 1, 1985. http://www.theses.fr/1985LYO10507.

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Greffage radicalaire du methacrylate de glycidyle apportant des fonctions oxiranne sur du polypropylene. Adaptation de la granulometrie du copolymere obtenu. Proprietes mecaniques de polypropylenes renforces de fibre de verre dont on modifie l'interface solide solide par le copolymere
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22

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.

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Dans les matériaux composites, la substitution des renforts minéraux ou synthétiques par des fibres végétales est possible pour de nombreuses applications industrielles, automobile ou non. Cependant, l'origine naturelle des fibres végétales, leurs structures complexes et multi composants rendent leur utilisation plus difficile à maîtriser que dans le cas des renforts usuels. Ces travaux de thèse ont donc pour objectif de contribuer à la compréhension des paramètres clés pour profiter de la capacité de renforcement des fibres végétales courtes dans une matrice thermoplastique (PP). Dans un premier temps, nous avons étudié le rôle des éléments constituant un composite renforcé par des fibres courtes et transformé par injection. Ceci a mis en évidence l 'intérêt de l'utilisation des fibres de lin comme renfort de composites. L'influence de leur fraction volumique et de la compatibilisation fibre / matrice a aussi été étudiée. La comparaison entre procédé d'extrusion et d'injection a souligné l'effet de la mise en œuvre sur la microstructure et sur les propriétés mécaniques des composites. Nous avons ensuite montré qu'il était possible d'extruder un polypropylène renforcé par des fibres de lin qui réponde au cahier des charges de l 'automobile, avec cependant des limitations au niveau de la stabilité du process. L'étude des composites hybrides lin / talc extrudés, a montré que l'ajout de particules de talc apportait une amélioration des propriétés mécaniques et une diminution des défauts d'extrusion. Enfin, nous avons mis en évidence, pour les fibres courtes ou longues, que la division et la dispersion des renforts étaient les paramètres clés à contrôler pour bénéficier de leur capacité de renforcement
Natural 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
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Han, Hongchang. "Study of agro-composite hemp/polypropylene : treatment of fibers, morphological and mechanical characterization". Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0002/document.

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L’utilisation des fibres végétales dans les polymères composites suscite de nombreuses investigations. Avant de mélanger les fibres végétales dans le polymère, un traitement chimique peut être effectué permettant de réduire l’hydrophilicité des fibres et d’améliorer l'adhérence à l’interface fibre/matrice. Dans cette thèse, l'eau et l'alcali sont utilisés d'abord pour traiter les fibres de chanvre, puis trois agents silane : 3-(triméthoxysilyl)propyl méthacrylate (MPS), N-[3- (triméthoxysilyl)propyl] aniline (PAPS) et (3-Aminopropyl)-triéthoxysilane (APS), sont utilisés pour modifier plus ou moins la surface des fibres de chanvre. Ces fibres traitées ou modifiées sont ensuite mélangées avec le polypropylène (PP) pour la fabrication des composites. Les effets de ces différents traitements sur la structure, les composants et l’hydrophilicité des fibres, et les propriétés mécaniques de ces composites sont mis en évidence. Nous avons étudié ensuite l’effet de vieillissement sur leurs comportements mécaniques, notamment l'humidité, la température et le rayonnement ultraviolet. Les résultats ont montré que le traitement de fibres par l'eau et l’alcali a des effets considérables sur la structure de fibres, les propriétés mécaniques et la durabilité des composites renforcés. La modification par l'agent de silane a une influence moins importante sur la structure des fibres, pourtant son groupe fonctionnel a une influence significative sur les propriétés mécaniques et la résistance au vieillissement des composites renforcés
Using agro fiber as reinforcement of polymer com-posites attracts numerous investigations due to the good mechanical properties and environmental benefits. Prior to blend agro fiber with polymer, chemical treatment can be employed to treat agro fiber for the purpose of reducing the hydrophilicity of fiber and improving the interfacial adhesion fi-ber/polymer matrix. In this thesis, water and alkali are utilized to treat hemp fiber firstly and then three silane agent as 3-(Trimethoxysilyl)propyl methacry-late (MPS), N-[3-(Trimethoxysilyl)propyl]aniline (PAPS) and (3-Aminopropyl)-triethoxysilane (APS) are employed to modify the hemp fiber surface. These treated or modified fibers are blended respectively with polypropylene (PP) to fabricate the hemp fiber/PP composites. The effects of these different treatments on the structure, components and hydro-philicity of fiber, and the mechanical properties of the reinforced PP composites are studied. Moreover, the accelerated ageing experiments including humidity, temperature and ultraviolet of the reinforced PP composites are conducted. The results showed that the fiber treatment of water and alkali has a considerable effect on fiber structure, mechanical properties and durability of the reinforced compo-sites. The silane agent modification of fiber has less influence on the fiber structure but its functional group has great influence on the mechanical proper-ties and ageing resistance of the reinforced compo-sites
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Perrin, Florence. "Rupture interlaminaire en mode I dans les composites unidirectionnels polypropylène/fibres de verre". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0012/MQ60912.pdf.

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25

Puech, Laurent. "Développement de composites polypropylène renforcés par des fibres de chanvre pour application automobile". Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT144.

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Face à la nécessité de trouver des alternatives aux ressources d’origine fossile et de limiter les impacts environnementaux de l’activité humaine, un important effort de recherche est actuellement en cours pour favoriser et accroître l’utilisation de produits issus de ressources renouvelables, comme les fibres végétales, dans la conception de pièces industrielles. Toutefois, de nombreux verrous scientifiques et technologiques restent encore à lever avant de pouvoir valoriser de façon fiable et durable ces fibres dans un contexte technique exigeant tel que celui du secteur l’automobile. Ainsi, l’amélioration de la qualité de l’interface fibres végétales / matrice polymère est un enjeu de taille car elle constitue une condition permettant de satisfaire les performances mécaniques requises telles que la rigidité, la résistance ou la tenue au choc. Dans ce contexte, l’objectif de la thèse a été le développement de fibres courtes de chanvre à propriétés de surface maitrisées et ciblées. Des solutions de fonctionnalisation de surface applicables par des procédés industrialisables ont été développées dans le but d’incorporer ces fibres dans une matrice polypropylène (PP). Les fibres de chanvre ont ainsi été traitées selon différentes stratégies de fonctionnalisation incluant l’utilisant du polypropylène greffé anhydride maléique (PP-g-MA), d’organosilanes, d’un acide aminé, d’isocyanates et d’un polyuréthane. Deux procédés de traitement à faible impact environnemental ont été comparés : le sprayage direct des fibres par les molécules de fonctionnalisation et l’incorporation de ces molécules par extrusion réactive. Les traitements en extrusion réactive se sont montrés plus efficaces que ceux réalisés par sprayage dans le cas du PP-g-MA. Trois voies de fonctionnalisation se sont avérées pertinentes au regard des propriétés mécaniques visées : i) l’utilisation de PP-g-MA seul en extrusion réactive ; ii) la fonctionnalisation par sprayage d’un aminosilane ou d’un acide aminé couplée à l’incorporation du PP-g-MA en extrusion réactive. S’appuyant sur le développement de moyens expérimentaux et d’analyses spécifiques, l’étude du comportement au choc des biocomposites a montré que les composites renforcés fibres de chanvre permettent d’absorber d’avantage d’énergie que les composites PP / verre (à taux volumique de renfort identique) pour une longueur de fissuration similaire. Une modélisation par éléments finis du comportement au choc des composites étudiés est également proposée
Due 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
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Tonoli, Gustavo Henrique Denzin. "Aspectos produtivos e análise do desempenho do fibrocimento sem amianto no desenvolvimento de tecnologia para telhas onduladas". Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/74/74131/tde-11052006-145210/.

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Estudos anteriores utilizando matriz cimentícia reforçada exclusivamente com fibras vegetais propiciaram a produção de telhas com desempenho aceitável nas idades iniciais. Porém, com o envelhecimento natural, as telhas apresentaram significativa redução do desempenho mecânico, fato este atribuído principalmente ao ataque alcalino da matriz cimentícia. A presente pesquisa teve como objetivo o aprimoramento de telhas onduladas de fibrocimento sem amianto, a partir de processo automatizado. A primeira etapa do trabalho consistiu na avaliação do efeito da intensidade de refino da polpa Kraft de sisal (Agave sisalana) nas propriedades mecânicas e físicas de placas planas baseadas em matriz de cimento Portland, e o uso conjunto com fibras de poliproprileno (PP). Esta etapa envolveu também a caracterização dos principais atributos das polpas celulósicas refinadas, bem como a caracterização microestrutural (microscopia eletrônica de varredura e porosimetria por intrusão de mercúrio) do material resultante após envelhecimento acelerado e em ambiente natural. Na segunda etapa, séries de telhas onduladas de fibrocimento foram produzidas por técnica de sucção do excesso de água e prensagem, utilizando os melhores parâmetros definidos na etapa anterior. Os efeitos da cura acelerada em autoclave e dos envelhecimentos acelerados (carbonatação acelerada, imersão-secagem e calor-chuva) nas propriedades mecânicas e físicas das telhas foram avaliados. Os resultados obtidos mostraram a grande contribuição do refino da polpa celulósica na melhoria da resistência dos compósitos. Altas intensidades de refino apresentaram os melhores resultados para compósitos reforçados somente com polpa celulósica, mesmo após os envelhecimentos, porém intensidades intermediárias em compósitos híbridos mostraram-se suficientes. A adição das fibras de polipropileno como reforço híbrido teve como ponto forte a manutenção da resistência ao impacto, propriedade esta fortemente afetada pelo envelhecimento acelerado nos compósitos reforçados somente com polpa de sisal. As telhas produzidas mostraram-se mais eficientes no amortecimento térmico do que telhas comerciais de fibrocimento amianto. Melhorias no processo de produção das telhas mostraram efetiva contribuição no desempenho mecânico em relação aos trabalhos anteriores, tanto no curto como no longo prazo. Os resultados também indicaram a utilização da carbonatação acelerada como um procedimento eficiente na mitigação da degradação sofrida pelas fibras celulósicas em meios menos agressivos, no caminho para tornar viáveis os materiais reforçados com fibras vegetais.
Previous studies using exclusively vegetal fibres as the sole reinforcement of cement matrix have propitiated the production of roofing tiles with acceptable performance at the first ages. However, with the natural ageing, the roofing tiles have presented significant reduction in the mechanical performance, attributed to the alkaline attack of the cimentitious matrix mainly. The present research had as objective the improvement of undulate fibrecement roofing tiles without asbestos with automated equipment for production. The study also evaluated the physical, mechanical and microstructural behaviour of the obtained composites. The first stage consisted of evaluating the refinement effect of sisal Kraft pulp on mechanical and physical properties of flat pads based on Ordinay Portland cement and the jointly use of polypropylene fibres (PP). This stage also involved the characterization of the main attributes of refined cellulosic pulps, as well as the microstructural characterization (scanning electron microscopy and mercury intrusion porosimetry) of the resultant material after the accelerated and natural ageing. In the second stage, series of fibrecement roofing tiles were produced by slurry dewatering technique and pressing, using the best parameters of the first stage. Efects of autoclaved curing and accelerated ageing (accelerated carbonation, soak-dry and heat-rain) on mechanical and physical properties of tiles were evaluated. Results showed the great contribution of pulp refinement on mechanical strengh improvement. Higher intensities of refinement provided the best results for composites only reinforced with sisal pulp, despite ageing mechanism. Intermediate refinement revealed to be enough for hybrid composites. Adition of polypropylene fibres as hybrid reinforcement provided toughness maintenance after ageing, which was strongly affected only in sisal reinforced composites. Asbestos free tiles showed to be more efficient on thermal insulating properties than commercial asbestos cement. Improvements on tiles production process showed effective contribution on mechanical performance in relation to the previous works, both at initial ages and after ageing. The results have also indicated the utilization of accelerated carbonation as an effective procedure to mitigate the degradation suffered by the cellulosic fibres in the less aggressive medium, in way of the viability of the cement based materials reinforced by vegetal fibres.
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27

Vasconcelos, Raimundo Expedito. "Fratura do concreto reforçado com fibras de aço e de polipropileno em meios normal e agressivo". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265241.

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Orientador: Itamar Ferreira
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
Made available in DSpace on 2018-08-20T13:36:03Z (GMT). No. of bitstreams: 1 Vasconcelos_RaimundoExpedito_D.pdf: 8931585 bytes, checksum: 2702f0165d8fe9827be26136404cc3d5 (MD5) Previous issue date: 2012
Resumo: O concreto convencional, não armado, apesar de suas vantagens é frágil, detendo reduzida resistência a deformações e baixa capacidade de suportar cargas de tração. A forma de atenuar esses inconvenientes pode ser a introdução de fibras descontínuas para melhorar este comportamento. Assim, quando o concreto é reforçado com fibras tende a melhorar o comportamento quando submetido a esforços de tração, flexão e choque. Microfibras de polipropileno reduzem danos devidos à fissuração da retração plástica antes do endurecimento do concreto e as fibras de aço trabalham como reforço estrutural. O trabalho que foi desenvolvido tem por objetivo analisar as propriedades mecânicas (compressão axial, tração na flexão e tenacidade na flexão) do concreto reforçado com fibras de aço nas dosagens 20, 30 e 40kg/m³ e fibras de polipropileno nas dosagens 3, 4,5 e 6kg/m³, utilizando-se o cimento CP V - ARI, em meios normal (ao ar) e agressivo (em solução aquosa de 3% em peso de cloreto de sódio). Os agregados utilizados na composição do concreto foram a areia média e brita nº 2. Para comparação entre os compósitos, foram confeccionados 126 corpos-de-prova. Os ensaios tiveram o suporte das normas técnicas da ABNT para determinação da resistência à compressão axial, características físicas do cimento e dos agregados. Quanto à determinação da tenacidade foram utilizadas as normas ASTM C 1609/C 1609M-10 e JSCE-FS4/1994. Os resultados mostraram que os teores de fibras de aço e polipropileno contribuiram para melhorar a tenacidade, mas com relação à exposição nos meios normal e agressivo, não houve variação expressiva de comportamento para os vários tipos de compósitos estudados
Abstract: The conventional concrete, unarmed, despite advantages is brittle and has reduced resistance to deformation and low ability to withstand tensile loads. The form to attenuate these inconveniences can be the introduction of discontinuous fibers improves this behavior. Thus, when the concrete is reinforced with fibers there is a tendency of improving its performance when subjected to tensile loads, bending and shock. Polypropylene microfibers reduce damage due to plastic shrinkage cracking, before the hardening of concrete, steel fibers work as structural reinforcement. The work was developed aims to analyze the mechanical properties (axial compression, bending and tensile toughness) of reinforced concrete with steel fibers at doses 20, 30 and 40kg/m³ and polypropylene fibers at doses 3, 4.5 and 6 kg/m³ cement using the CP V - ARI in normal (air) and aggressive (in aqueous solution of 3 % sodium chloride) environments. The aggregates used in the composition of the concrete were medium sand and crushed aggregate no. 2. For comparison between the composites were made 126 specimens. The trials had the orientation of the ABNT standards for determination of compressive strength, physical characteristics of cement and aggregates. For determination of the toughness was used the ASTM C 1609/10 and C-1609M JSCE-FS4/1994. The results showed that the contents of steel fibers and polypropylene contributed to improve toughness, but in terms of environment, normal and aggressive, there was no significant change of behavior, for the several studied types of composites
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
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28

Pelissou, Olivier. "Le comportement en flexion : Un critère de faisabilité de matériaux composites verre/polypropylène". Ecully, Ecole centrale de Lyon, 1993. http://www.theses.fr/1993ECDL0020.

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L'étude du comportement en flexion de composites unidirectionnels à matrice polypropylène renforcée de fibres de verre continues est utilisée comme critère de faisabilité de ces matériaux. L’élaboration a fait l'objet du développement d'un procédé de fabrication de composites à base de fils hybrides verre/polypropylène. Les cycles de mise en œuvre ont été optimisés en fonction de critères basés sur la microstructure et les propriétés élastiques des produits moulés. La caractérisation mécanique est axée sur la compréhension des modes de rupture sous sollicitation monotone. Les composites verre/polypropylène réalisés se caractérisent par des ruptures catastrophiques en compression sous sollicitation de flexion. Afin de s'affranchir des phénomènes de concentrations de contraintes dus aux appuis lors des essais de flexion trois points, un essai original de flexion par flambement post-critique a été développé. Cet essai, qui permet de générer une sollicitation de flexion pure, s'avère particulièrement adapté à la caractérisation de composite a matrice ductile. L'analyse détaillée du comportement en flexion induit a l'identification de deux mécanismes de dégradation: microflambage et glissement de fibres (essais de flexion trois points) et flambement/délaminage (essai de flexion par flambement. L'étude paramétrique des propriétés a rupture envisage l'influence de paramètres lies au matériau (matrice, microstructure, interface) et a la mise en œuvre (semi-produit verre/thermoplastique, tissu, conditions de moulage). Une modélisation des mécanismes de dégradation, mettant l'accent sur la microstructure spécifique des composites verre/polypropylène induite par le procédé de transformation, est proposée
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29

Leterrier, Yves. "Evolution rhéologique et structurale d'un composite polypropylène/fibres de verre lors de son estampage". Vandoeuvre-les-Nancy, INPL, 1991. http://www.theses.fr/1991INPL105N.

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En vue d'optimiser le procédé industriel d'estampage des thermoplastiques renforcés (TRE), la rhéologie et l'évolution microstructurale d'un composite polypropylène/fibres de verre ont été étudiées lors de compressions isothermes à 200c ou non-isothermes a 50c. Les essais ont été réalisés à l'aide de deux rhéomètres originaux, qui permettent d'appliquer des écoulements purs (axisymétrique ou unidirectionnel), de mesurer avec précision la force d'estampage et de tremper le matériau à tout instant pendant la période d'écoulement. La distribution d'orientation des fibres a été analysée par un nouveau système automatique d'analyse d'images microscopiques (vidéofibres). Les résultats expérimentaux ont permis d'identifier les mécanismes essentiels de déformation du matériau TRE. Dans le domaine des grandes vitesses, c'est l'élongation visqueuse de strates fibreuses parallèles et leur glissement relatif qui contrôle le processus d'écoulement macroscopique. Dans le domaine des petites vitesses c'est l'exsudation du polypropylène au travers de la structure de fibres qui joue le rôle prépondérant. L'élimination des cavités résiduelles sous l'effet de la pression d'estampage se produit par dissolution du gaz dans la matrice polymère. Les fibres des couches superficielles, soumises à d'intenses cisaillements, présentent de fortes courbures et une orientation préférentielle dans la direction de l'écoulement, tandis que les fibres des couches profondes pivotent selon la direction d'extension. Compte tenu de l'échec des modèles classiques d'écoulement fluide entre plaques parallèles, nous avons développé un modèle original d'évolution de la force de compression du TRE, ou apparait un terme de résistance élongationnelle et une composante de frottement inter laminaire. Cette approche ajuste correctement la plupart des courbes expérimentales. Un second modèle, qui décrit les instabilités de glissement, rend compte des cas critiques rencontrés dans la géométrie unidirectionnelle
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30

Odendaal, Courtney Megan. "Establishment of performance-based specifications for the structural use of locally available macro-synthetic fibres". Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96678.

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Thesis (MEng)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: FRC (Fibre-reinforced concrete) has become a common form of secondary and even primary reinforcing in some applications throughout the world. In South Africa, the structural applications are limited primarily to steel fibres while cheaper, lighter and more durable synthetic fibres have been side-lined due to low stiffnesses. The purpose of this research project is to investigate the behaviour of synthetic fibre-reinforced concrete (SynFRC) using fibres which are locally available in South Africa, and to propose a performance-based specification and test method for the use of these fibres. In order to achieve this, single fibre pull-out tests were performed on four locally available polypropylene fibres. It was found that the average bond stresses of the fibres are influenced primarily by the fibre cross sectional shape, longitudinal geometry and surface treatment, and secondarily by the aspect ratio. The W/C ratio had little effect on the single fibre performance of non-treated fibres, but appeared to have a slight effect on the single fibre performance of the surface treated fibre. From the experimental results, the highest fibre bond stress will be generated by using a fibre with an X-shaped cross section, longitudinal crimping and applying a surface treatment to this fibre. It also appears that the bond stress distribution for flat fibres is close to uniform, while the bond stress distribution for non-flat crimped fibres has a high mechanical interlock component at the surface end. Macro-mechanical performance tests were performed by means of the BS EN 14651 (2007) three point beam bending test and the ASTM C1550 (2012) Round Determinate Panel Test (RDPT). These tests were selected following a thorough literature review. The RDPT was found to be more consistent and able to identify trends which the three point beam bending test could not. In addition, the three point beam bending test’s most popular output, the Re,3 value tended to be misleading with varying W/C ratios, and it is recommended that the equivalent flexural tensile strength be used instead if the three point beam bending test is used. The macro-mechanical testing showed that increasing the fibre dosage did increase post-cracking performance. The flat fibres’ performance was significantly better than that of the non-flat fibres, and also increased at a faster rate with increasing fibre dosage. The post-cracking performance decreased with increasing W/C ratios and increasing aggregate sizes. The macro-mechanical performance was inversely proportionate to the single fibre performance. The macro-mechanical performance decreased with increasing fibre bond stress, and increased with increasing equivalent diameter, which equates to fewer fibres in a set volume of fibres. Finally, basic principles were developed from the data. These principles were used to predict the RDPT and three point beam bending test performance parameters based on fibre dosage, single fibre properties (bond stress and equivalent diameter), W/C ratio and aggregate size from the available data. The principles can be further refined with more experimental data.
AFRIKAANSE OPSOMMING: Vesel-gewapende beton word regoor die wêreld as ’n algemene vorm van sekondêre en selfs primêre versterking gebruik. In Suid-Afrika is die strukturele toepassings hoofsaaklik tot staal vesels beperk, terwyl goedkoper, ligter en meer duursame sintetiese vesels vermy word as gevolg van lae styfhede. Die doel van hierdie navorsingsprojek is om die gedrag van sintetiese-veselversterktebeton (SynFRC) te ondersoek deur gebruik te maak van vesels wat in Suid-Afrika beskikbaar is, en 'n prestasie-gebaseerdespesifikasie en toetsmetode vir die gebruik van sintetiese vesels voor te stel. Enkelveseluittrektoetse is op vier plaaslik beskikbare polipropileen vesels uitgevoer. Daar is gevind dat die gemiddelde verbandspanning van die vesel hoofsaaklik deur die vesel deursnee vorm, lengte meetkunde en oppervlak behandeling beïnvloed word, en tweedens deur die aspek verhouding beïnvloed. Die W/C-verhouding het min effek op die enkelveselprestasie van nie-behandelde vesels, maar het 'n effek op die enkeleveselprestasie van die oppervlak-behandelde vesel gehad. Die eksperimentele resultate wys dat die hoogste vesel verbandspanning deur 'n vesel met 'n X-vormige deursnit, lengte krimping en toepassing van 'n oppervlak behandeling gegenereer sal word. Dit blyk ook dat die verbandspanningverspreiding vir ’n plat vesel naby aan uniform is, terwyl die verbandspanningverspreiding vir ’n nie-plat gekrimpde vesel 'n hoë meganiese grendeling komponent op die oppervlak ente het. Makro-meganiese prestasietoetse is uitgevoer deur middel van die BS EN 14651 (2007) driepuntbalkbuigtoets en die ASTM C1550 (2012) RDPT. Hierdie toetse is ná ’n deeglike literatuuroorsig gekies. Die RDPT is meer konsekwent en is in staat om neigings te identifiseer wat die driepuntbalkbuigingtoets nie kan nie. Daarbenewens, met wisselende W/C verhoudings, is die driepuntbalkbuigtoets se gewildste resultaat, die Re,3-waarde geneig om misleidend te wees. Dit word aanbeveel dat die ekwivalentebuigtreksterkte in plaas van die Re,3-waarde as die drie punt balk buig toets resultaat gebruik word. Die makro-meganiesetoets het getoon dat die verhoging van die veseldosis ’n toename in na-krakingprestasie veroorsaak. Die plat vesels se prestasie was aansienlik beter as die van nie-plat vesels, en het met 'n toenemende veseldosis teen 'n vinniger koers verhoog. Die na-krakingprestasie het met toenemende W/C en die verhoging van die klip grootte afgeneem. Die makro-meganieseprestasie was omgekeerd eweredig aan die enkelveselprestasie. Die makro-meganieseprestasie het met toenemende vesel band stres verminder, en het met 'n toenemende gelykstaande deursnee (wat gelykstaande is aan minder vesel in 'n stel volume van vesel) vergroot. Ten slotte is basiese beginsels uit die data ontwikkel. Hierdie beginsels is gebruik om die RDPT en driepuntbalkbuigtoets prestasieparameters gebaseer op veseldosis, enkelveseleienskappe (verbandspanning en ekwivalentediameter), W/C-verhouding en klip grootte van die beskikbare data te voorspel. Die beginsels kan met meer eksperimentele data verder verfyn word.
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31

Moeiri-Farsi, M. H. "Effects of autoclave temperatures on properties of cementitious based matrices reinforced with randomly orientated polypropylene fibres". Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336075.

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32

Thevenin, Philippe. "Etude rheologique d'un composite polypropylene/fibres de verre estampe : couplage entre l'orientation et l'ecoulement visqueux anisotrope". Besançon, 1995. http://www.theses.fr/1995BESA2056.

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Ce memoire rapporte une etude experimentale et theorique de la rheologie d'un materiau composite a matrice thermoplastique renforcee de fibres discontinues lors de sa phase de mise en forme par estampage. A l'oppose des materiaux techniques traditionnels, le composite doit au niveau de sa specificite s'adapter aux exigences de conception alors que celle-ci decoule habituellement des proprietes des materiaux constitutifs. En cherchant a realiser simultanement le materiau et le produit, le procede devient indissociable des composants puisque les performances de la structure en dependent etroitement. Un des buts a atteindre est ainsi de disposer les renforts de maniere optimale en fonction des efforts ou des contraintes auxquelles la structure est en mesure d'etre soumise, c'est-a-dire de placer le cout dans les zones les plus sollicitees et non partout ailleurs, comme cela est communement opere en presence de materiaux homogenes et isotropes. Il s'agit en quelque sorte de realiser une anisotropie controlee generatrice de proprietes adequates. Or la fabrication d'un materiau composite a matrice polymere est en general un procede rendu complexe par la nature heterogene de la structure. Et, dans la majeure partie des cas, les proprietes mecaniques et physico-chimiques du materiau objet de la mise en forme presentent un degre d'anisotropie plus ou moins prononce mais dont il serait inopportun de negliger les effets. C'est dans ce contexte que s'inscrit cette etude dont l'objectif est de materialiser le couplage entre l'ecoulement gouverne par une loi de type fluide visqueux anisotrope non-newtonien et l'etat local d'orientation du renfort interagissant et evoluant tout au long de la transformation. Des lois de comportement et d'orientation sont developpees et identifiees sur des ecoulements experimentaux isothermes de type plaque. Puis, la description de l'etat local est integree dans un code de calculs par elements finis permettant de simuler l'ecoulement de maniere globale et de confronter le modele a l'experience. L'interet est d'une part de predire l'evolution de l'anisotropie et ses repercussions sur l'ecoulement, notamment la deformee du front de matiere en presence de bords libres, et d'autre part de pouvoir quantifier l'etat d'orientation final responsable des proprietes mecaniques et physiques de la structure
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33

Dubouloz-Monnet, Fabrice. "Etude des relations entre microstructure, morphologie et propriétés mécaniques de composites comêlés à matrice poly(propylène) renforcée par des fibres de verre unidimensionnelles". Chambéry, 2003. http://www.theses.fr/2003CHAMS034.

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L'objectif de ce travail est de comprendre les relations liant l'architecture de composites comêlés à leurs propriétés mécaniques macroscopiques. Dans cette optique, des fibres de verre unidirectionnelles ont été comêlées avec des filaments de polypropylène, puis les semi-produits ont été consolidés à chaud sous pression afin d'́élaborer les composites étudiés. Tout d'abord, l'analyse microstructurale des composites n'a révélé aucune modification de la structure cristalline de la matrice polymère lors des différentes étapes de leur élaboration. Le taux de cristallinité du polymère est insensible au procédé et est peu influencé par la présence des fibres de verre. Cependant, ces fibres jouent le rôle d'agent de germination du polymère, sans toutefois favoriser la formation de phase transcristalline à proximité de leur surface. La seconde patie a consisté à définir et à quantifier l'état de dispersion des fibres de verre dans la matrice à différentes échelles d'analyse. Une analyse morphologique en 2D a montré que plus de 86 % des fibres étaient assemblées sous forme d'ágrégats dispersés dans la matrice. De plus, le taux d'agrégats augmente linéairement avec le taux de fibres. Une approche théorique, soulignant les morphologies auto-similaires des composites, a été ensuite confrontée avec succès aux résultats expérimentaux pour tous les taux de renforts. La dernière partie a permis de prédire le comportement mécanique dynamique des composites aux basses températures en prenant en compte la morphologie réelle de ces matériaux et en utilisant des techniques d'homogénéisation. Les différences révélées aux hautes températures ont été attribuées à des changements microstructuraux de la matrice. L'analyse du comportement mécanique aux grandes déformations a montré que l'endommagement des composites était principalement gouverné par la distance entre les agrégats, alors que leur rupture dépendait essentiellement de la déformation de la matrice polymère
The aim of this work is to understand the relations connecting the structure of commingled composites to their macroscopic mechanical properties. Accordingly, unidirectional glass fibres were commingled with polypropylene filaments, and then hot consolidated under pressure in order to manufacture the studied composites. The rate of crystallinity of polymer is insensitive to the process and is not influenced by the presence of glass fibres. However, these fibres act as nucleating agents for the polymer, without generating the formation of a transcrystalline phase in the vicinity of their surface. The second part of this study involved the definition and the quantification of the state of dispersion of glass fibres in the matrix at various scales of analysis. A 2D morphological analysis has shown that more than 86 % of fibres were assembled in the form of aggregates dispersed within the matrix. In addition, the rate of aggregates increases linearly with the fibre content. A theoretical approach, highlighting the self-similar morphologies of the composites, was then confronted successfully with the experimental results for all the filler contents. The last part of this study allowed us to predict the dynamic mechanical behaviour of the composites at the low temperatures by taking into account the actual morphology of these materials and using methods of homogenisation. The differences revealed at the high temperatures were attributed to microstructural changes of the matrix. The analysis of the mechanical behaviour at large deformations showed that the damage of the composites was mainly governed by the distance between the aggregates, whereas their failure depended essentially on the deformation of the polymer matrix
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34

Tancrez, Jean-Pierre. "Contribution à l'étude dela fragilité de composites polypropylène-fibres de verre courtes moulés par injection". Lille 1, 1994. http://www.theses.fr/1994LIL10028.

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L'addition de fibres de verre courtes (pvc) a une matrice polypropylene (pp) permet d'augmenter tres sensiblement le module, la resistance ainsi que la stabilite dimensionnelle apres moulage mais elle provoque egalement une dramatique reduction de la capacite de deformation et donc une fragilisation des composites pp+fvc. Les objectifs de ce travail etaient: l'identification des micromecanismes de deformation et de rupture responsables du comportement fragile des composites pp+fvc; dans le cas particulier des pieces moulees par injection, la recherche des microstructures et des parametres (compositions de la matrice et de l'ensimage, conditions d'injection et d'essai) susceptibles de faciliter l'activation de tels mecanismes de fragilisation; l'etude de l'influence des parametres precedents sur les caracteristiques mecaniques a la rupture. Nous avons, entre autres, montre dans cette etude que: la presence de fibres de verre n'induit pas de modification microstructurales de la matrice susceptibles d'expliquer a elles-seules sa fragilisation mais elle provoque l'apparition de defauts, de concentrations de contraintes et d'une triaxialite de contraintes qui jouent un role de premier plan dans l'initiation et la propagation de la rupture, en particulier dans la zone de cur; - les parametres les plus influents au niveau du comportement a la rupture des composites et des caracteristiques mecaniques resultantes, sont ceux qui sont lies aux fibres: orientations et distributions de longueur de fibres et adhesion fibres-matrice a l'interface.
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35

Desbordes, Bruno. "Etude du comportement rhéologique et de l'injection du polypropylène renforcé de fibres de verre courtes". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37604482m.

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36

COPPONNEX, THIERRY. "Nouveaux developpements dans l'analyse du test de fragmentation appliques aux composites modeles fibres de verre e-polypropylene". Paris, ENMP, 1996. http://www.theses.fr/1996ENMP0606.

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La determination des caracteristiques micromecaniques de l'interface fibre-matrice dans un composite sert d'une part a evaluer les effets des modifications chimiques apportees a la matrice ainsi que des traitements de surface des fibres dont les buts sont d'optimiser les performances de l'interface. D'autre part, elle fournit des donnees necessaires a la modelisation micromecanique des proprietes macromecaniques des composites. Pour ces deux raisons, les tests micromecaniques d'adhesion sont d'une certaine importance autant d'un point de vue industriel que fondamental. L'objectif du present travail est l'etude, d'un point de vue pratique et theorique du test de fragmentation, appliquee aux systemes fibre de verre-polypropylene. Outre les aspects pratiques d'elaboration et de mise en uvre du test, la demarche theorique suivie est double: d'un point de vue industriel, une analyse qualitative du test, en utilisant des analyses en contraintes unidimensionnelles peut s'averer suffisante sous reserve de certaines modifications, que sont entre autres une determination adequate de la resistance a la rupture des fibres ainsi qu'une definition differente du concept fondamental de longueur critique inherent a ce test. Les elements necessaires a de telles modifications ainsi que leurs consequences sont etudies en detail. D'un point de vue theorique et quantitatif maintenant, les hypotheses simplificatrices des analyses unidimensionnelles occultent les mecanismes reels qui menent a l'endommagement interfacial. En particulier, l'utilisation d'un critere en cisaillement maximum pour l'amorcage de la decohesion fibre-matrice n'apparait pas comme le plus adapte. Une analyse tridimensionnelle par contre, basee sur des calculs variationnels permet l'utilisation d'un critere energetique de decohesion qui reste en accord avec les mecanismes d'endommagement rencontres experimentalement. L'analyse permet ainsi une mesure quantitative des proprietes interfaciales en termes d'energies interfaciales de decohesion. Ces developpements bases sur les concepts de la mecanique de la fracture presentent une reelle alternative aux methodes d'analyses existantes du test de fragmentation
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37

Paris, Agnès. "Etude de l'influence des conditions de filage sur les proprietes physiques et mecaniques de fibres de polypropylene". Paris, ENMP, 1992. http://www.theses.fr/1992ENMP0362.

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Notre travail a porte sur l'etude de l'influence des conditions de filage, c'est-a-dire de la temperature d'extrusion, de la vitesse de tirage et de la quantite de refroidissement, sur les proprietes physiques (orientation et cristallinite) et mecaniques des fibres de polypropylene. Dans la premiere partie est presentee une etude bibliographique portant sur l'influence des parametres moleculaires du polypropylene sur sa rheologie et sa filabilite et sur l'influence des parametres du procede sur les cinetiques de cristallisation et les proprietes morphologiques des fibres. Les fibres a frisure potentielle, fibres possedant la particularite de boucler lorsqu'elles subissent un apporte d'energie, y sont etudiees. Le deuxieme chapitre decrit la ligne de filage pilote, son instrumentation et les moyens de caracterisation des fibres (diffraction des rayons x, analyse enthalpique differentielle et dynamometrie). Les resultats, discutes au troisieme chapitre, mettent en evidence l'importance de la quantite de refroidissement sur les proprietes des fibres en se basant sur la visualisation de la birefringence en ligne. En particulier, il est montre que le taux d'elongation moyen et les facteurs d'orientation des phases cristalline et amorphe augmentent lorsque le refroidissement est plus important. Les etudes en microscopie optique a balayage mettent en evidence une structure fibrillaire des fibres. Leur analyse par diffraction des rayons x montre que leur morphologie presente une double texture: l'une parallele a l'axe de la fibre et l'autre perpendiculaire a cet axe. Cette double texture est favorisee par un faible taux de tirage. La simulation du procede de filage, developpee au quatrieme chapitre, permet de constater que les cinetiques globales de cristallisation sous elongation ne peuvent etre decrites par une loi de type ozawa qu'en reliant ses coefficients au taux d'elongation. Enfin, la derniere partie est consacree a l'etude des fibres a frisure potentielle. En nous appuyant sur les resultats precedents, nous montrons que les parametres de la frisure dependent de la quantite et de l'asymetrie du refroidissement, et qu'il est possible de predire cette frisure mathematiquement
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38

Silva, Celso de Araujo Duarte. "Compósitos de polipropileno reforçados com fibras de sisal para uso na indústria automobilística". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3149/tde-30122014-162204/.

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O polipropileno com carga ou reforço de fibras de sisal (PP Sisal) é um composto desenvolvido para ser aplicado no processo de injeção de peças plásticas automotivas. Compósitos de polipropileno reforçados com cargas minerais (talco) ou fibras de vidro têm sido largamente aplicados nesse segmento. Porém, fibras naturais são uma importante alternativa considerando-se os aspectos de sustentabilidade, reciclabilidade, abundância e baixo custo, se comparadas a fibras de vidro e ao talco industrial. Neste trabalho escolheu-se o sisal como reforço em função dos resultados obtidos em testes de tração, impacto, homogeneidade, resistência a riscos, a não formação de pontas quando fraturado e ao menor peso específico da peça final. Este trabalho conduziu ensaios e testes para comparar o desempenho do novo composto aos compostos atualmente em uso. Resultados mostraram que o PP - sisal apresenta melhor rigidez e maior resistência do que os seus concorrentes, ainda contando com o apelo natural e ecológico do composto. Outro aspecto muito importante neste estudo foi o uso de polipropileno reciclado, o que transformou o resultado final num produto ainda mais ecológico e rentável.
Reinforced with sisal fibers, polypropylene (PP - Sisal) is a compound developed to be applied in the injection process of plastic automotive parts. Polypropylene compounds reinforced with mineral fillers (talc) or fiber glass have been widely applied in this segment. However, natural fibers are an important alternative considering the following aspects: sustainability, recyclability, abundant availability and low cost, if compared with fiber glass and mineral fillers. This work chose sisal as reinforcement in function of the results achieved in the tests of traction, impact, homogeneity and scratch resistance. Besides that, no sharp is formed when broken and specific weight is light in the final part. We conducted try-outs and test to compare the performance of the new composition with that of current ones, and results have shown that the PP - sisal presents better rigidity and greater resistance than its competitors, still counting with natural and ecological appeal. Another very important aspect in this study was the use of recycled polypropylene, which made final results more ecological and profitable.
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39

Rivera, Jésus Emilio. "Comportement en flexion-compression des poteaux en béton ordinaire renforcés avec fibres synthétiques de polypropylène/polyéthylène". Mémoire, Université de Sherbrooke, 2009. http://savoirs.usherbrooke.ca/handle/11143/1516.

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The goal of this research project is to analyze the behavior of columns made with plain concrete and synthetic polypropylene/polyethylene fiber addition. In order to supplement the current data base, an experimental study was carried out on six columns of real size and ordinary concrete resistance confined by circular stirrups and subjected to constant axial loads and cyclic flexure. Three columns were built with concrete of normal resistance with 0% of synthetic fibers and three columns were built of concrete with 1% by volume of synthetic fibers.The used concrete strength varied from 25 to 42 MPa, the resistance of longitudinal steel was 510 MPa, that of the stirrups of 468 and 510 MPa and the axial factor load around 25% Ag f'c . Today, it is possible to explore the behavior in the plastic range of the structural elements under seismic loading. Predictions of behaviour of moment vs curvature as well as predictions of force vs displacement relationship were accomplished. Indeed, the comparison between the experimental results and the prediction made for the specimens with and without fibers shows a very good agreement. In the case of the prediction of the moment vs curvature relationship, the MNPHi software developed by [PAULTRE, 1996] was used and in the case of the prediction of force vs displacement relationship, software DISP96 developed by [LÉGERON, 1998] was used. Finally, the influence of tie spacement as well as addition of fibers were clearly observed.The results show that the presence of polypropylene/polyethylene fibers in the concrete matrix improves ductility, tenacity, and the capacity to dissipate energy. Also, they help to retain the cover concrete.
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40

Drevelle, Christophe Delobel René Le Bras Michel. "Conception et développement de systèmes retardateurs de flamme pour fibres synthétiques". Villeneuve d'Ascq : Université des sciences et technologies de Lille, 2007. https://iris.univ-lille1.fr/dspace/handle/1908/553.

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Reproduction de : Thèse de doctorat : Structure et dynamique des systèmes réactifs : Lille 1 : 2005.
N° d'ordre (Lille 1) : 3721. Résumé en français et en anglais. Titre provenant de la page de titre du document numérisé. Bibliogr. à la suite de chaque chapitre.
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41

Nguyen, Duy Cuong. "Caractérisation de l'interface fibre/matrice : application aux composites polypropylène/chanvre". Thesis, Troyes, 2016. http://www.theses.fr/2016TROY0009/document.

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Les agro-composites font l'objet de nombreuses études et applications industrielles en raison des multiples propriétés mécaniques qu'ils présentent. Ces propriétés présentent de grandes perspectives comparées à celles des composites traditionnels. Cependant les connaissances sur le comportement mécanique de l'interface fibre/matrice restent limitées. De plus, la différence de propriété entre la fibre hydrophile et la matrice hydrophobe peut causer des défauts au niveau de l’interface. Il est donc important de caractériser finement la décohésion à l'interface au cours d'une sollicitation. Plusieurs méthodes ont été proposées dans la littérature, elles sont généralement très complexes à mettre en œuvre et sont coûteuses. Dans cette étude, nous avons développé une méthode de caractérisation en se basant sur l'essai de « pull-out ». La géométrie de la fibre a été prise en compte dans le calcul des propriétés mécaniques de l'interface par la mise à profit d'une approche inspirée de la tomographie. L'influence de la température d'élaboration sur les propriétés mécaniques de l'interface a été étudiée de manière à définir la température optimale. L'évolution des propriétés interfaciales a été suivie au cours d'un vieillissement en humidité relative. Après quatre semaines, la résistance au cisaillement et la rigidité au cisaillement de l'interface sont diminuées fortement alors que la déformation à la rupture est augmentée
Agro-composites are increasingly studied and applied to various industries over recent years due to good mechanical properties compared to conventional composites especially in terms of specific values. However, since low adhesion between the hydrophilic fiber and hydrophobic matrix, which occurs one of the main breaks modes in this kind of material, the characterization of the interface becomes a key problem. For investigation of this issue, existing methods show limitation for reasons of complexity (in preparation, in principle) and of cost. In this study, we developed a « pull-out ». In particular, the real fiber geometry of the plant fiber was taken into the calculation of mechanical properties of interface using a tomography inspired method. By checking the effective temperature of the molding then varying it, we studied the effect of this processing parameter to mechanical properties of fibre/matrix interface and determined the optimal conditions. The developed experimental protocol is applied to aged interfaces in order to clarifying the evolution of interfacial properties during the aging time to relative humidity. After four weeks, the interfacial shear strength and the shear modulus of the interface were greatly reduced while the shear deformation at the rupture was greatly increased
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42

Girardello, Vinícius. "Ensaios de placa em areia não saturada reforçada com fibras". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/29984.

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O objetivo do presente trabalho foi estudar o comportamento mecânico de uma areia não saturada, com e sem reforço de fibras, através de ensaios de placa realizados em densidade relativa de 50% e 90%. Para o reforço da areia foi acrescentada a quantidade de 0,5% de fibra de polipropileno em relação ao peso seco de solo. A análise dos resultados dos ensaios de placa indica que a inclusão de fibras influencia significativamente no comportamento carga-recalque do material. O melhor resultado foi obtido para o ensaio realizado na maior densidade relativa (DR = 90%) com adição de fibras, apresentando uma mudança significativa no comportamento carga-recalque. Ensaios triaxiais também foram realizados a fim de obter os parâmetros de resistência e deformação dos materiais estudados. Além disso, ensaios de sucção foram realizados para avaliar a sua influência sobre os parâmetros de resistência do solo não saturado, com e sem reforço.
The aim of present research was to study the mechanical behavior of unreinforced and fiber-reinforced unsaturated sand through plate load tests carried out at relative densities of 50% and 90%. For the reinforced sand, 50 mm long polypropylene fibers were added at a concentration of 0.5% by dry weight. The analysis of the plate test results indicates that the soil load-settlement behavior is significantly influenced by the fiber inclusion. The best performance was obtained for the densest (DR=90%) fiber-sand mixture, where a significant change in the load-settlement behavior was observed. Triaxial tests were also carried out in order to establish the strength and deformation parameters of the materials studied. Furthermore, suction tests were carried out to investigate its potential influence on the strength parameters of the unsaturated fiber-reinforced and unreinforced materials.
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43

Rodríguez, Monteagudo Manuel. "Evaluación de materiales compuestos por inyección a partir de fibras procedentes de la biomasa de maíz (Zea mays L.) y polipropileno". Doctoral thesis, Universitat de Girona, 2015. http://hdl.handle.net/10803/482219.

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The present PhD work has been done within the research topics of the Laboratory of Paper Engineering and Polymer Materials (LEPAMAP) at the University of Girona. Composite materials from high yield corn biomass fibers reinforced polypropylene homopolymer matrix had been prepared. The composites were formulated with up to 50wt% fiber contents. The main interest was to determine the mechanical properties of composite materials, micromechanics of the fibers and the composites and the application of the materials on the industrial design of products.
Aquest treball ha estat realitzat dintre el marc i les línies de treball del Laboratori d’Enginyeria Paperera i Materials Polímers (LEPAMAP) de la Universitat de Girona. Partint de fibres de biomassa de blat de moro s’han formulat materials compostos amb fins a un 50% en pes, amb i sense agents d’acoblament, i un polipropilè homopolímer com a matriu polimèrica. El principal interès ha estat conèixer les propietats mecàniques dels materials compostos, la micromecànica de les fibres i dels compostos y la aplicació dels materials al disseny industrial de nous productes.
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44

Liang, Hua. "The in-situ formation and management of fibres in moulded composites of polypropylene and a thermotropic liquid crystalline polymer". Thesis, Brunel University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241574.

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45

Krishnaiah, Prakash. "Development of polylactide and polypropylene composites reinforced with sisal fibres and halloysite nanotubes for automotive and structural engineering applications". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/43498/.

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In recent decades, scientific research giving more attention to the development of bio-based polymer composites due to the extensive usage of petroleum based fillers as well as polymer matrices for the generation of polymer composites. It is a well-known fact that the petroleum derived polymer composites raise inevitable issues such as environmental pollution, waste management and depletion of petroleum resources etc. So it is important to develop fully or partially biodegradable polymer composites without compromising the mechanical, physical and thermal properties which are required for the end use applications. In this investigation, two different types of filler materials such as sisal fibres and halloysite nanotubes were used to prepare PLA polymer composites and their morphology, physical, mechanical, dynamic mechanical, thermal, water absorption and biodegradable properties were studied. This work also involves the preparation and properties of polypropylene composites reinforced with sisal fibres and halloysite nanotubes to compare the mechanical and thermal properties with PLA composites. First, surface treatment was performed for sisal fibres in order to remove the amorphous materials such as hemicellulose, lignin and pectin from the surface of the fibres which enhances the fibre-matrix interfacial strength and mechanical properties of the fibres and their polymer composites. Sisal fibres were subjected to different surface treatments such as alkali, high intensity ultrasound (HIU), and the combination of alkali and HIU and their effects on the morphology, fibre diameter, moisture absorption, mechanical and thermal properties of untreated and surface treated sisal fibres were studied. Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FE-SEM) results confirmed the removal of amorphous materials after the combined treatments of alkali and ultrasound. Moisture absorption and diameter of the sisal fibres were significantly reduced by 40 and 200% respectively after the combination of alkali and HIU treatment as compared to untreated sisal fibres. TGA results revealed that the thermal stability of sisal fibres obtained with the combination of alkali and HIU treatment significantly increased by 38.5 oC as compared to the untreated fibres. Tensile properties of single fibre showed a reduction in the tensile strength and modulus by 25% and 26% respectively as compared to the untreated sisal fibre owing to surface treatments. A reduction in the tensile properties is mainly due to the removal of amorphous materials from the surface of sisal fibres which act as binding materials for cellulose. Second, the effect of different surface treatments on the morphology, mechanical, thermal, water absorption and biodegradable properties of sisal fibres reinforced PLA (SF/PLA) composites has been investigated. For this, different ratio of untreated and surface treated sisal fibres was mixed with PLA polymer matrix by using an internal mixer. Compounded materials from the internal mixer were subjected to compression moulding to prepare the test specimens. FE-SEM analysis confirmed the good dispersion of different surface treated SF in the PLA composites. The tensile strength and modulus increased by 10 and 75.4% for 15 wt% and 30 wt% of fibre loading respectively with the combined treatment of alkali and HIU PLA composites as compared to the untreated fibre reinforced PLA composites. Young’s modulus of the composites has also been predicted by using the theoretical models which fit well to the obtained experimental values. Dynamic-mechanical analysis (DMA) revealed that the combination of alkali and HIU treated SF/PLA composites showed an increase in the storage modulus by 15% and 30% as compared to the untreated fibre composites and pure PLA respectively. TGA and DSC analysis revealed that the thermal stability and crystallinity increased significantly for the PLA composites reinforced with sisal fibres of combined treatment of alkali and HIU. Water absorption study showed a considerable reduction in the water absorption and coefficient of diffusion by 136% and 130% respectively for the combination of alkali and HIU treated SF/PLA composites as compared to untreated SF/PLA composites. The degradation of SF/PLA composites was studied by composting the samples into the soil. A significant weight loss of 17.87% could be observed for the addition of 30 wt% of untreated SF/PLA composites after soil composting for 120 days. Apart from sisal fibres, halloysite (Hal) nanotubes were also used as reinforcement fillers to study their effectiveness in improving the mechanical and thermal properties of PLA nanocomposites. Hal nanotubes were surface modified with 3-aminopropyltriethoxysilane (APTES) to enhance the surface interaction of Hal nanotubes with PLA and to achieve good dispersion of Hal nanotubes across the PLA matrix. Nitrogen adsorption-desorption, FTIR and TGA analysis results were confirmed the successful modification of Hal nanotubes surface with APTES. The different wt% of unmodified and APTES modified Hal-PLA nanocomposites were prepared by using internal mixer and compression moulding machine. The resultant Hal-PLA nanocomposites were characterized for their morphology, thermal, mechanical and dynamic-mechanical properties. Tensile strength increased to 62.6 MPa with the addition of 4 wt% of APTES modified Hal-PLA nanocomposites which is 26.5% higher than pure PLA and 15% higher than unmodified (4 wt%) Hal-PLA nanocomposites. Impact strength of 4 wt% APTES modified Hal-PLA nanocomposites increased by 20% and 40% as compared to unmodified Hal-PLA nanocomposites and the pure PLA respectively. TGA analysis revealed that the thermal stability increased significantly by 17 oC with the addition of 4 wt % of APTES modified Hal nanotubes onto PLA. Storage modulus increased by more than 10% with the addition of 4 wt% of APTES modified Hal nanotubes as compared to pure PLA. To compare the PLA composites with conventional polymer matrix composites, composites of polypropylene (PP) were prepared by reinforcing with sisal fibres and Hal nanotubes and the effect of surface treatment of sisal fibres and surface modification of Hal nanotubes on the mechanical and thermal properties of SF/PP and Hal-PP nanocomposites were studied. Tensile properties were increased for the combined treated SF/PP composites as compared to the untreated and pure PP. Tensile modulus and strength increased by more than 50% and 10% respectively as compared to the untreated SF/PP composites. TGA and DSC results revealed that the combination of alkali and HIU treatments increased the thermal stability and crystallinity by 8 oC and 8% respectively as compared to untreated SF/PP composites. DMA analysis confirmed the significant enhancement of storage modulus for the combined treated SF/PP composites by 50% as compared to pure PP. Mechanical and thermal properties were studied for unmodified and APTES modified Hal nanotubes reinforced PP nanocomposites. The investigations suggest that the mechanical properties of APTES modified Hal-PP nanocomposites were found to be superior to the unmodified Hal-PP nanocomposites. The tensile strength and modulus increased by 31 and 72% with the addition of 6 wt% of APTES modified Hal-PP nanocomposites as compared to pure PP. Impact strength also increased by 44% than pure PP with 6 wt% loading of APTES modified Hal nanotubes. Thermal analysis revealed that the thermal stability and percentage crystallinity increased by 15 oC and 22% respectively for the Hal-PP nanocomposites with surface modification by APTES. DMA analysis shows the improved storage modulus by 28% as compared to pure PP. Based on the present work, it can be said that the sisal fibres and Hal nanotubes have potential as reinforcing materials in the generation of fully bio-based polymer composites.
However, surface treatments and/or modification were playing an important role in order to tune the required mechanical and thermal properties of the polymer composites. This study also proved that in comparison to the conventional polymer matrix materials such as PP, PLA is a strong competitor with respect to its good mechanical properties and improved thermal stability apart from the fact that PLA is one of the best known biodegradable and biocompatible polymer matrices in the current market to use not only in medical application, but also in various commercial applications such as packaging, automotive and home appliances.
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46

Spadetti, Carolini. "Preparação e caracterização de compósitos de polipropileno pós-consumo reforçados com fibras de celulose". reponame:Repositório Institucional da UFES, 2015. http://repositorio.ufes.br/handle/10/1849.

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CAPES
Compósitos de polipropileno reforçados com fibras naturais são uma importante alternativa considerando-se aspectos como sustentabilidade, reciclabilidade, abundância e baixo custo, se comparadas às fibras sintéticas. Este trabalho foi realizado com o objetivo de incentivar o uso de materiais reciclados, tendo no resultado final um produto ainda mais ecológico e rentável, através da associação do polipropileno reciclado e das fibras naturais. Foram investigadas as propriedades térmicas, mecânicas e morfológicas de compósitos de polipropileno reciclado e virgem, reforçados com até 40% em massa de fibras de celulose tratadas pelo método alcalino, branqueadas (FB), sem branqueamento (FNB) e tratadas com o tensoativo catiônico brometo de hexadeciltrimetilamonio (CTAB), (FCTAB), com concentração de 0,01 mol/L. Para obtenção dos dados, foram utilizadas as técnicas de Análise Térmica Dinâmico-Mecânica (DMTA), Calorimetria Exploratória Diferencial (DSC), Microscopia Eletrônica de Varredura (MEV) e Ressonância Magnética Nuclear (RMN). Os resultados mostraram que, compósitos de polipropileno reciclado, com as fibras branqueadas e não-branqueadas, possuem módulo de armazenamento (E’), inferior, quando comparados aos compósitos preparados com o PP virgem, no entanto com valores bem próximos. Essa redução para os compósitos com FNB foi de 577 MPa, para os compósitos com FB de 567 MPa e para os compósitos com FCTAB, ocorreu um aumento de 256 MPa. Houve uma redução do grau de cristalinidade (χc), de todos os compósitos produzidos. Já sobre a temperatura de cristalização, a inserção de fibras acarretou na diminuição de em média 3°C nas amostras com matriz reciclada e um aumento de em média 8°C, para as amostras com matriz virgem. Ocorreu um pequeno aumento na temperatura de fusão cristalina (Tm), com a inserção de fibras para os compósitos com as duas matrizes e uma redução em torno de 6°C na temperatura de transição vítrea (Tg) para os compósitos com FCTAB, e em torno de 3°C para os com FNB e FB.
Polypropylene composites reinforced with natural fibers are an important alternative considering aspects such as sustainability, recyclability, abundance and low cost, compared to synthetic fibers. This work was carried out in order to encourage the use of recycled materials, and the end result is a product even greener and profitable, through the association of recycled polypropylene and natural fibers. Thermal, mechanical and morphological composite recycled and virgin polypropylene were investigated, reinforced with up to 40% by weight of pulp fibers treated by alkaline method, bleached (FB) without bleaching (FNB) and treated with cationic surfactant bromide hexadecyltrimethylammonium bromide (CTAB) (FCTAB) with concentration of 0.01 mol / L. To obtain the data, we used the techniques of Dynamic-Mechanical Thermal Analysis (DMTA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and nuclear magnetic resonance (NMR). The results showed that recycled polypropylene composites with non-bleached and bleached fibers have a storage modulus (E '), lower compared to composites prepared with virgin PP, but with very close values. This reduction for composites FNB was 577 MPa for the composites FB 567 MPa and the composites FCTAB, an increase of 256 MPa. There was a reduction in the degree of crystallinity (χc) of the generated composite. Already on the crystallization temperature, the fiber insertion resulted in decreased an average of 3° C in samples with recycled mother and an increase of an average 8 ° C for the samples with virgin matrix. There was a small increase in the crystalline melting temperature (Tm), with the insertion of fibers for composites with two arrays and a decrease of about 6°C in glass transition temperature (Tg) for composites FCTAB, and around 3°C for at FNB and FB.
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47

Teodoro, Janice Mesquita. "Resistência ao cisalhamento de solos reforçados com fibras plásticas". Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-14062018-144401/.

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Este trabalho aborda o comportamento de dois solos (uma argila e uma areia), reforçados com fibras plásticas de polipropileno. Os solos foram compactados no teor de umidade ótimo e peso específico seco máximo e foram misturados com fibras de diferentes teores e comprimentos. Os resultados dos ensaios de compressão simples foram usados para selecionar os teores e comprimentos ótimos de fibras. Os resultados mostraram que a resistência do solo arenoso cresceu com o aumento do teor e comprimento das fibras e o solo argiloso apresentou acréscimo de resistência, com o aumento do teor até o comprimento de fibra de 10 mm. As curvas tensão-deformação dos ensaios triaxiais, para solos com e sem reforço foram similares, com uma resistência de pico definida e pequena redução de queda de tensão pós pico. As amostras de solo arenoso apresentaram considerável aumento de resistência, com o aumento do teor e comprimento das fibras. Pequenos painéis, fabricados com o solo argiloso (300 x 300 x 100) mm, mostraram que a presença da fibra pode reduzir a magnitude das trincas quando comparados com o solo sem reforço.
This work presents the behavior of two soils (clay and sandy) reinforced with polypropylene plastic fibers. The soils were compacted at the optimum moisture content and maximum dry unit weight and were mixed with fibers of different lengths and contents. Unconfined compressive tests results were used to select the optimum fiber length and content. The results showed that the granular soil strength increased with increasing fiber length and content. The cohesive soil, on the other hand, showed strength up to fiber length of 10 mm. Stress - strain curves from triaxial tests for both reinforced and unreinforced cohesive soil were similar with a defined peak strength and small post peak reduction. Granular soil samples presented considerable strength increases with the increases of length and fiber content. Small panels fabricated with the reinforced cohesive soil (300 x 300 x 100) mm, showed that the presence of fiber can reduce crack magnitude when compared with the unreinforced soil.
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48

Festugato, Lucas. "Comportamento de hidratação e resposta cisalhante cíclica de resíduo de mineração cimentado reforçado com fibras". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/35605.

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As propriedades do solo cotidianamente podem não ser adequadas às características e às necessidades de projeto. É apresentada, como alternativa, a técnica de reforço com inclusão de elementos fibrosos à matriz de solo cimentado e não cimentado. Ainda, embora comuns, o comportamento do solo frente a solicitações cíclicas não é completamente conhecido. Nesse sentido, o estudo do comportamento de hidratação e da resposta cisalhante cíclica de um resíduo de mineração cimentado reforçado com fibras é objetivado. Para tanto, medidas de retração química, medidas de rigidez ao longo da hidratação e ensaios simple shear monotônicos e cíclicos foram realizados com resíduo de mineração cimentado e não cimentado, reforçado com fibras e não reforçado. O resíduo, oriundo da mineração de ouro, um silte arenoso com traços de argila, foi cimentado com diferentes teores de cimento Portland, entre 0% e 10% em relação à massa de solo seco, e reforçado com 0% e 0,5%, em relação à massa de sólidos secos, de fibras de polipropileno de 50mm de comprimento e 0,1mm de espessura, equivalentes a um índice aspecto de 500. Os resultados demonstraram que as fibras não afetaram o processo de hidratação das misturas de resíduo de mineração cimentadas, que apresentam tendência de atenuação logarítmica da retração química com o tempo. Quanto maiores as relações água/cimento, maior o nível de retração química. A inclusão de fibras a misturas de resíduo de mineração cimentadas, da mesma forma, não afetou a evolução dos valores de rigidez inicial, que crescem com tendência logarítmica em função do tempo e aumentam com o acréscimo do nível de cimentação. Sob condições monotônicas de cisalhamento, a adição de fibras conferiu ao material cimentado e não cimentado comportamento de endurecimento. Sob condições cíclicas de deformação cisalhante controlada, as fibras não afetaram a resposta cisalhante das amostras não cimentadas e provocaram aumento dos valores da tensão cisalhante das amostras cimentadas após sucessivos ciclos de esforços. Sob condições cíclicas de tensão cisalhante controlada, a adição de fibras às misturas não cimentadas proporcionou o aumento da resistência aos ciclos de esforços e às misturas cimentadas provocou aumento dos níveis de deformação cisalhante. A concordância das mesmas envoltórias de resistência tanto às trajetórias de tensões dos ensaios monotonônicos quanto às trajetórias dos ensaios cíclicos sob diferentes condições de carregamento possibilitou a obtenção dos mesmos parâmetros de resistência das misturas analisadas sob diferentes condições de carregamento.
The soil properties commonly may not suit the project characteristics and requirements. It is presented, as alternative, the improvement technique of fibrous elements inclusion to the cemented and uncemented soil matrix. Moreover, although common, the behaviour of soil under cyclic loads is not completely known. In this sense, the study of the hydration behaviour and the cyclic shear response of fibre reinforced cemented mine tailings is the main objective of this research. Therefore, chemical shrinkage measurements, stiffness measurements during hydration and monotonic and cyclic simple shear tests were conducted on fibre reinforced and unreinforced cemented and uncemented mine tailings. The tailings, produced from gold mining, are classified as a sandy silt with traces of clay and were cemented with different amounts of Portland cement, ranging from 0% to 10% by dry weigh of soil, and reinforced with 0% and 0.5% by dry weigh of solids of polypropylene fibers 50mm long and 0.1mm thick, equivalent to an aspect ratio of 500. The results showed fibres did not affect the hydration process of cemented mine tailings mixtures, which presents logarithmic attenuation of chemical shrinkage over time. The greater the water / cement ratio, the higher the level of chemical shrinkage. The inclusion of fibers to cemented mine tailings, likewise, did not affect the evolution of initial stiffness values, that raise logarithmic over time and increase with the increase of the cementation level. Under monotonic shear conditions, the addition of fibers confers hardening behaviour to the uncemented and cemented materials. Under shear strain controlled cyclic conditions, fibres did not affect the shear response of uncemented samples and increased shear stress values of cemented samples after successive load cycles. Under shear stress controlled cyclic conditions, the fibres addition to the uncemented mixtures increased the resistance to load cycles and to the cemented mixtures increased levels of shearing strain. The agreement of the same strength envelopes to both monotonic and cyclic stress paths, under different cyclic loading conditions, allows the use of the same strength parameters of mixtures analyzed under different loading conditions.
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49

Araújo, Cícero Thiago Figueiredo de. "Estudo do comportamento de juntas de argamassa reforçadas com fibras de polipropileno". Universidade Federal de Alagoas, 2005. http://repositorio.ufal.br/handle/riufal/375.

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In this work the connection behavior between precast elements using cement mortar with polypropylene fibers addition is studied to evaluate its performance when compression loads is applied. A numerical analysis with the finite elements program ANSYS 7.1® was made considering mortars range from 0% to 50% of polypropylene fibers addition. The numerical model considered in the analysis was composed of two reinforced concrete blocks with 10x10x20cm dimensions, joined between themselves by a cement mortar with marble and granite residue addition, developed in laboratory, which will receive polypropylene fibers addition. The numerical analysis was later validated by an experimental program. With the gotten results, it was evidenced that lower than 3% tax fibers propitiated better performance of the joint and, consequently, of the model. A profit in the horizontal and vertical deformation capacity was observed prorroguing the mortar splitting in the model, which makes high system strength capacity, resulting in an increase of the connection ductility. Between 4% and 10% the model kept any behavior alteration and from 15%, it started to lose strength and rigidity. The experimental models had presented load capacity profit with fibers addition and similar cracked ways of numerical model and the models observed in literature. However 2% fibers taxes higher were not possible to investigate because a lower workability performance had been gotten.
Fundação de Amparo a Pesquisa do Estado de Alagoas
Neste trabalho estuda-se o comportamento da ligação entre elementos pré-moldados através de juntas de argamassa com adição de fibras de polipropileno, avaliando o desempenho das mesmas quando solicitadas a tensões de compressão. O modelo proposto para análise do comportamento da ligação é composto de dois blocos de concreto armado com dimensões 10x10x20cm, unidos entre si por uma argamassa de cimento e areia com adição de resíduo oriundo do beneficiamento de mármore e granito, desenvolvida em laboratório em uma dissertação de mestrado, a qual recebeu adição de fibras de polipropileno. Faz-se uma avaliação numérica do modelo proposto através do programa de elementos finitos ANSYS 7.1® considerando argamassas com adição até 50% de fibras de polipropileno que é posteriormente validado em um programa experimental. Pelos dados obtidos numericamente, constata-se que o incremento de fibras até a taxa de 3% propicia um melhor desempenho da junta e, consequentemente, do modelo. Observa-se um ganho na capacidade de deformação horizontal e vertical da mesma, prorrogando, com isso, o descolamento do modelo, fazendo com que o sistema mantenha por mais tempo sua capacidade resistente, o que significa um aumento da ductilidade da ligação. Entre 4% e 10% o modelo mantém-se sem alteração no seu comportamento e a partir de 15%, começa a perder resistência e rigidez. Os modelos experimentais apresentam ganho de capacidade de carga com o acréscimo de fibras e modos de fissuração semelhantes ao modelo numérico e aos modelos propostos na literatura. Entretanto os teores práticos de fibras só atingem 2%, o que impossibilita os estudos para os demais teores.
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50

Bouzouita, Sofien. "Optimisation des interfaces fibre-matrice de composites à renfort naturel". Phd thesis, Ecole Centrale de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00769959.

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Les fibres naturelles ont réussi à acquérir un grand intérêt à l'échelle académique et industrielle. Ces fibres sont résistantes, possèdent des densités relativement basses, ont de faibles coûts et proviennent de ressources renouvelables abondantes. Les mêmes techniques classiques peuvent être utilisées pour la mise en œuvre des composites à base de fibres naturelles. Tous ces avantages ont fait que des constructeurs automobiles, par exemple, s'intéressent massivement à intégrer des pièces en ce type de composite dans plusieurs modèles de leurs véhicules. Cependant, les problèmes de compatibilité entre les fibres lignocellulosiques et les thermoplastiques limitent le transfert de charge entre fibre et matrice et ainsi les propriétés mécaniques des composites. La durabilité de ces matériaux en présence d'eau ou d'humidité est aussi problématique à cause de la haute hydrophilie des fibres naturelles. Le but de ce travail est de mieux comprendre les phénomènes relatifs à la mise en œuvre et à la l'utilisation de matériaux composites à base de polypropylène renforcé par des fibres de chanvre. L'influence d'un séchage préalable des fibres et d'une nouvelle technique de pré-imprégnation à sec, appelée Fibroline, ont été particulièrement étudiées. Cette dernière consiste à soumettre une poudre et un substrat fibreux à imprégner à un champ électrique de haute tension. Celui-ci provoque l'accélération des grains et crée une parfaite répartition de la résine dans le support fibreux. Au cours de ce traitement, des modifications chimiques et physiques peuvent se produire et entraîner l'amélioration de l'adhésion fibre/matrice. L'influence des techniques de préparation et de mise en œuvre sur les propriétés morphologiques, chimiques et mécaniques des fibres a été analysée. Des observations MEB ont permis de mettre en évidence des modifications de la surface par apparition de micro-craquelures après séchage, application du champ électrique et surtout après double traitement (séchage et Fibroline). Des analyses chimiques par XPS (spectroscopie photo-électronique aux rayons X) des fibres ont montré aussi des modifications de la chimie des surfaces. Principalement des phénomènes d'oxydation sont apparus. D'autre part, la caractérisation mécanique par traction sur mono-filaments dans différents états, a montré une dégradation des propriétés des fibres lors de leur préparation et lors de la phase d'imprégnation en utilisant la technique Fibroline, comparé au cas brut de réception. Les propriétés interfaciales ont été analysées en utilisant trois techniques. D'une part mécaniquement en utilisant le test de fragmentation et le test de déchaussement de micro-goutte, et d'autre part, par suivit de cristallisation isotherme à l'aide de platine chauffante et microscopie optique en lumière polarisée. Les essais mécaniques ont montré l'amélioration de la résistance interfaciale des fibres pré-séchées et celles traitées par la technique Fibroline. Celles doublement traitées ont vu leurs propriétés interfaciales chuter. L'analyse sous conditions isothermes des phénomènes de cristallisation ont permis d'observer l'apparition de zones transcristallines uniformes dans les deux cas ayant été imprégnés par la technique Fibroline. Ceci peut être expliqué par les modifications apportées par cette technique au niveau des surfaces des fibres. [...]
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