Дисертації з теми "Polypropylene fibrous"
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Biyana, Nobuhle Yvonne. "Studies on flax/polypropylene-reinforced composites for automotive applications." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/d1021150.
Повний текст джерелаJia, Jun. "Melt spinning of continuous filaments by cold air attenuation." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37276.
Повний текст джерелаKalyankar, 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.
Повний текст джерелаSlánská, 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.
Повний текст джерелаBadji, 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.
Повний текст джерелаBiocomposites 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
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.
Повний текст джерелаThe 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
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.
Повний текст джерелаSoccalingame, 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.
Повний текст джерелаNowadays, 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
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.
Повний текст джерелаNatural 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.
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.
Повний текст джерелаUntersuchungen 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
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.
Повний текст джерелаRols, Sébastien. "Conception d'un composite ciment-fibres de polypropylène ductile et durable." Lyon, INSA, 1996. http://www.theses.fr/1996ISAL0116.
Повний текст джерелаThe 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
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.
Повний текст джерелаUntersuchungen 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.
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.
Повний текст джерелаDo, Thi Vi Vi. "Matériaux composites à fibres naturelles / polymère biodégradables ou non." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENA012/document.
Повний текст джерелаNatural 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
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.
Повний текст джерелаAbdennadher, Ahmed. "Injection de Polypropylène Renforcé de Fibres Naturelles : Procédé, Microstructure et Propriétés." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0045/document.
Повний текст джерелаNatural 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
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.
Повний текст джерелаGérard, 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.
Повний текст джерелаAl-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.
Повний текст джерелаRenard, 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.
Повний текст джерелаCoroller, Guillaume. "Contribution à l'étude des matériaux composites renforcés par des fibres végétales : cas des composites extrudés à matrice polypropylène." Lorient, 2013. http://www.theses.fr/2013LORIS302.
Повний текст джерелаNatural fibers can replace mineral or synthetic reinforcements in many industrial applications, for automotive or not. Their complex and multi component structure as well as their natural origin lead to higher difficulties in this kind of reinforcement than the usual ones. The aim of this thesis work is give a better understanding of the key parameters to control to get the reinforcement capacity of natural fibers. In a first step we studied the influence of the components on the mechanical properties of an injected polypropylene. This has highlighted the interest in flax fibers for composite's reinforcement. It has also underlined the influence of fiber content and using coupling agent. The comparison between extrusion molding and injection molding bas showed the effect of molding process on microstructure and mechanical properties, injection molding showing a better efficiency. Then we focused on extrusion molding, and we have brought to light that it is possible to extrude polypropylene reinforced with flax fiber that is complying with automotive specifications, but it showed lack stability during extrusion process. The study of flax / talc hybrid composites extruded showed that adding talc particles to flax fibers help to increase mechanical properties and to troubleshoot extrusion issues. Finally, we highlighted that, for both short and long flax fibers, fiber's individualization and dispersion are one of the key parameters to control
Han, Hongchang. "Study of agro-composite hemp/polypropylene : treatment of fibers, morphological and mechanical characterization." Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0002/document.
Повний текст джерелаUsing 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
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.
Повний текст джерелаPuech, Laurent. "Développement de composites polypropylène renforcés par des fibres de chanvre pour application automobile." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT144.
Повний текст джерелаDue to the necessity to find alternatives to fossil resources and to reduce the environmental impacts of human activity, a major research effort is currently ongoing in order to develop and increase the use of biobased products from renewable resources, such as natural fibers, in the design of industrial parts. However, many scientific and technological hurdles have yet to be removed so as to promote these products before we can reliably and durably use these fibers in a demanding technical context as in automotive sector. Thus, improving the quality of the interface between natural fibers and polymer matrix is a major challenge, since it constitutes a condition for satisfying the required mechanical performances, such as stiffness, tensile or impact strengths. In this context, the thesis objective was to develop short hemp fibers with controlled and targeted surface properties. Surface-functionalization solutions have been developed, to be used by industrial processes, with the aim of incorporating these fibers in a polypropylene (PP) matrix. Therefore, hemp fibers have been treated according to various functionalization strategies including the use of grafted polypropylene maleic anhydride (PP-g-MA), organosilanes, an amino acid, isocyanates and a polyurethane. Two treatments processes, with low environmental impact, were compared: the direct spraying of functionalization molecules on fibers and reactive extrusion incorporation of these molecules. Reactive extrusion treatments were more efficient than those performed by spraying in the case of PP-g-MA. Three functionalization lanes have been found to be relevant regarding the mechanical properties targeted: i) using PP-g-MA alone in reactive extrusion; ii) spraying-functionalization of an aminosilane or of an amino acid coupled with the incorporation of PP-g-MA into the reactive extrusion. Based on the development of experimental means and specific analyzes, the study of the impact behavior of biocomposites has shown that hemp fiber reinforced composites allow to absorb more energy than PP / glass composites (at identical reinforcing volume rate) for a similar crack length. Also, a finite element modeling of the impact behavior of the studied composites is propounded
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/.
Повний текст джерелаPrevious 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.
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.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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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
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.
Повний текст джерелаLeterrier, 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.
Повний текст джерелаOdendaal, 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.
Повний текст джерелаENGLISH 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.
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.
Повний текст джерелаThevenin, 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.
Повний текст джерелаDubouloz-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.
Повний текст джерелаThe 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
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.
Повний текст джерелаDesbordes, 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.
Повний текст джерелаCOPPONNEX, 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.
Повний текст джерелаParis, 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.
Повний текст джерелаSilva, 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/.
Повний текст джерелаReinforced 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.
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.
Повний текст джерелаDrevelle, 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.
Повний текст джерелаN° 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.
Nguyen, Duy Cuong. "Caractérisation de l'interface fibre/matrice : application aux composites polypropylène/chanvre." Thesis, Troyes, 2016. http://www.theses.fr/2016TROY0009/document.
Повний текст джерелаAgro-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
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.
Повний текст джерелаThe 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.
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.
Повний текст джерелаAquest 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.
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.
Повний текст джерелаKrishnaiah, 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/.
Повний текст джерелаHowever, 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.
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.
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/.
Повний текст джерелаThis 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.
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.
Повний текст джерелаThe 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.
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.
Повний текст джерелаFundação 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.
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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