Rozprawy doktorskie: „Fibre durability”

1

Fisher, Alex K. "Durability design parameters for cellulose fibre reinforced concrete pipes in aggressive environments." Thesis, Queensland University of Technology, 2003.

Znajdź pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

2

Levin, Klas. "Durability of Embedded Fibre Optic Sensors in Composites." Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3145.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

3

Gurusamy, K. "The marine durability of steel fibre reinforced concrete." Thesis, University of Aberdeen, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234802.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

4

Nordström, Erik. "Durability of sprayed concrete : steel fibre corrosion in cracks /." Luleå, 2005. http://epubl.luth.se/1402-1544/2005/02.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

5

Nordström, Erik. "Steel fibre corrosion in cracks : durability of sprayed concrete." Licentiate thesis, Luleå tekniska universitet, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18249.

Pełny tekst źródła

Streszczenie:

Steel fibre reinforced sprayed concrete is common practice for permanent linings in underground construction. Today there is a demand on "expected technical service life" of 120 years. Thin steel fibres could be expected to discontinue carrying load fast with a decrease of fibre diameter caused by corrosion, especially in cracks. The thesis contains results from inspections on existing sprayed concrete structures and a literature review on corrosion of steel fibres in cracked concrete. To study the mechanisms ruling inititation and propagation of corrosion both field exposure tests and accelerated laboratory exposure tests with cracked steel fibre reinforced sprayed concrete have been performed. Parameters tested are type of spraying method, exposure environment, fibre length, usage of accelerators, crack width and time of exposure. A discussion on how the influence of corrosion on load bearing capacity should be considered in a service-life model is also presented. Godkänd; 2000; 20070317 (ysko)

Style APA, Harvard, Vancouver, ISO itp.

6

Homam, Sayed Mukhtar. "Durability of fibre-reinforced polymers (FRP) used in concrete structures." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0023/MQ50345.pdf.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

7

De, Klerk Marthinus David. "The durability of natural sisal fibre reinforced cement-based composites." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96895.

Pełny tekst źródła

Streszczenie:

Thesis (MEng)--Stellenbosch University, 2015. ENGLISH ABSTRACT: The building industry is responsible for a substantial contribution to pollution. The production of building materials, as well as the operation and maintenance of structures leads to large amounts of carbon-dioxide (CO2) being release in the atmosphere. The use of renewable resources and construction materials is just one of the ways in which the carbon footprint of the building industry can be reduced. Sisal fibre is one such renewable material. Sisal fibre is a natural fibre from the Agave Sisalana plant. The possibility of incorporating sisal fibre in a cement-based matrix to replace conventional steel and synthetic fibres has been brought to the attention of researchers. Sisal fibre has a high tensile strength in excess of polypropylene fibre and comparable to PVA fibre. Sisal fibre consists mainly of cellulose, hemi-cellulose and lignin. The disadvantage of incorporating sisal fibre in a cement-based matrix is the degradation of the composite. Sisal fibres tend to degrade in an alkaline environment due to changes in the morphology of the fibre. The pore water in a cement base matrix is highly alkaline which leads to the degradation of the fibres and reduced strength of the composite over time. Sisal fibre reinforced cement-based composites (SFRCC) were investigated to evaluate the durability of the composites. Two chemical treatments, alkaline treatment and acetylation, were performed on the fibre at different concentrations to improve the resistance of the fibre to alkaline attack. Alkaline treatment was performed by using sodium hydroxide (NaOH), while acetylation was performed by using acetic acid or acetic anhydride. Single fibre pull-out (SFP) tests were performed to evaluate the influence of chemical treatment on fibre strength, to study the fibre-matrix interaction and to determine a critical fibre length. A matrix consisting of ordinary Portland cement (OPC), sand and water were used for the SFP tests. This matrix, as well as alternative matrices containing fly ash (FA) and condensed silica fume (CSF) as supplementary cementitious material, were reinforced with 1% sisal fibre (by volume) cut to a length of 20 mm. The OPC matrix was reinforced with untreated- and treated fibre while the alternative matrices were reinforced with untreated fibre. Alternative matrices containing varying fibre volumes and lengths were also produced. Three-point bending- (indirect), direct tensile- and compression tests were performed on specimens at an age of 28 days to determine the strength of the matrix. The remainder of the specimens were subjected to ageing by extended curing in water at 24˚C and 70˚C respectively and by alternate cycles of wetting and drying, after which it was tested at an age of 90 days from production to evaluate the durability of the fibre. An increase in fibre volume led to a decrease in compressive strength and peak tensile strength. The optimum fibre length at a volume of 1% was 20 mm for which the highest compression strength was recorded. The combination of alkali treatment and acetylation was the most effective treatment condition, followed by alkali treatment at low concentrations of sodium hydroxide. At higher concentrations of sodium hydroxide, a significant reduction in strength was recorded. The addition of supplementary cementitious materials also proved to be effective in mitigating degradation, especially in the cases where CSF was used. FA proved to be less effective in reducing the alkalinity of the matrix. However, the use of FA as fine filler resulted in higher strengths. Specimens manufactured by extrusion did not have superior mechanical properties to cast specimens. The conclusion was made that the use of sisal fibre in a cement-based matrix is effective in providing ductile failure. Chemical treatment and the addition of supplementary cementitious materials did improve the durability of the specimens, although degradation still took place. AFRIKAANSE OPSOMMING: Die boubedryf is verantwoordelik vir 'n aansienlike bydrae tot besoedeling. Die produksie van boumateriale, sowel as die bedryf en instandhouding van strukture lei tot groot hoeveelhede koolstof dioksied (CO2) wat in die atmosfeer vrygestel word. Die gebruik van hernubare hulpbronne en boumateriale is maar net een van die maniere waarop die koolstof voetspoor van die boubedryf verminder kan word. Sisal vesels is 'n voorbeeld van 'n hernubare materiaal. Sisal vesel is 'n natuurlike vesel afkomstig vanaf die Agave Sisalana plant. Die moontlikheid om sisal vesels in 'n sement gebasseerde matriks te gebruik om konvensionele staal en sintetiese vesels te vervang, is tot die aandag van navorsers gebring. Sisal vesel het 'n hoër treksterkte as polipropileen vesels en die treksterkte vergelyk goed met die van PVA vesels. Sisal vesel bestaan hoofsaaklik uit sellulose, hemi-sellulose en lignien. Die nadeel verbonde aan die gebruik van sisal vesels in 'n sement gebasseerde matriks is die degradasie van die komposiet. Sisal vesels is geneig om af te breek in 'n alkaliese omgewing as gevolg van veranderinge wat in die morfologie van die vesel plaasvind. Die water in die porieë van 'n sement gebasseerde matriks is hoogs alkalies wat lei daartoe dat die vesel afgebreek word en die sterkte van die komposiet afneem oor tyd. Sisal vesel versterkte sement gebasseerde komposiete is ondersoek om die duursaamheid van die komposiete te evalueer. Twee chemiese behandelings, alkaliese behandeling en asetilering, is uitgevoer op die vesels teen verskillende konsentrasies om die weerstand van die vesels teen alkaliese aanslag te verbeter. Alkaliese behandeling was uitgevoer met natrium-hidroksied (NaOH) terwyl asetilering met asynsuur en asynsuurhidried uitgevoer is. Enkel vesel uittrek toetse is uitgevoer om die invloed van chemiese behandeling op veselsterkte te evalueer, om die vesel/matriks interaksie te bestudeer en om die kritiese vesellengte te bepaal. 'n Matriks wat uit gewone Portland sement (OPC), sand en water bestaan, is gebruik vir die enkel vesel uittrek toetse. Dieselfde matriks, sowel as alternatiewe matrikse wat vliegas (FA) en gekondenseerde silika dampe (CSF) as aanvullende sementagtige materiaal bevat, is versterk met 1% vesel (by volume) wat 20 mm lank gesny is. Die OPC matriks was versterk met onbehandelde- en behandelde vesels, terwyl die alternatiewe matrikse met onbehandelde vesels versterk is. Matrikse wat wisselende vesel volumes en lengtes bevat het is ook vervaardig. Drie-punt buigtoetse (indirek), direkte trek toetse en druktoetse is uitgevoer op proefstukke teen 'n ouderdom van 28 dae om die sterkte van die matriks te bepaal. Die oorblywende proefstukke is onderwerp aan veroudering deur verlengde nabehandeling in water teen 24˚C en 70˚C onderskeidelik en deur afwissilende siklusse van nat- en droogmaak waarna dit op 'n ouderdom van 90 dae vanaf vervaardiging getoets is om die duursaamheid van die matriks te evalueer. 'n Toename in vesel volume het tot 'n afname in druksterkte en piek treksterkte gelei. Die optimum vesel lengte teen 'n volume van 1% was 20 mm, waarvoor die hoogste druksterkte opgeteken is. Die kombinasie van alkaliese behandeling en asetilering was die mees effektiewe behandeling, gevolg deur alkaliese behandeling by lae konsentrasies natrium-hidroksied. Vir hoë konsentrasies natrium-hidroksied is 'n aansienlike afname in sterkte opgeteken. Die toevoeging van aanvullende sementagtige materiale was ook effektief om die degradadering van die vesels te verminder, veral in die gevalle waar CSF gebruik is. FA was minder effektief om die alkaliniteit van die matriks te verminder. Die gebruik van FA as fyn vuller het nietemin hoër sterkte tot gevolg gehad. Proefstukke wat deur ekstrusie vervaardig is, het nie beter meganiese eienskappe gehad as proefstukke wat gegiet is nie. Daar is tot die gevolgtrekking gekom dat sisal vesel in 'n sement gebasseerde matriks wel effektief is om 'n duktiele falingsmode te voorsien. Chemiese behandeling en die toevoeging van aanvullende sementagtige materiale het die duursaamheid van die proefstukke verbeter, alhoewel degradering steeds plaasgevind het.

Style APA, Harvard, Vancouver, ISO itp.

8

Zhang, J. "The performance and environmental durability of pultruded glass fibre composite rebars." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/7354.

Pełny tekst źródła

Streszczenie:

The work reported is a study of the performance of pultruded unidirectional glass fibre composite rebars, in order to understand and quantify the environmental degradation of the materials in water and alkali solution with, and without, stress. The rebars have been proposed as possible candidates for replacing reinforcing steel in concrete structures. Firstly, the interfacial strength, mechanical properties and dynamic mechanical properties of the rebar composites were investigated using ILSS and a three point bending test, in conjunction with SEM and dynamic mechanical thermal analysis (DMTA). It was concluded that the surface treatments on glass fibres played a major role in the ILSS of the composites. Likewise, the flexural properties and failure behaviour of the rebars were also affected and all were related to the ILSS values. With increasing ILSS, the flexural strength and modulus increased and the failure features varied from compressive, to mixed compressive-tensile, to tensile. This was because higher interphase strengths delayed the occurrence of fibre microbuckling and increased the instability of glass fibres in the matrix. It was found that the glass transition temperature (Tg), as measured by DMTA, can be used to assess interfacial strength. A strong interphase resulted in a relatively higher Tg (and vice versa). This appears to have been caused by the more efficient transfer of the "restraining effect of glass fibres" on polymer chain mobility. The rate and magnitude of flexural property degradation in alkali solution was similar to that in water, except that at 80°C, the modulus was considerably reduced. This was caused by the corrosion of defect inclusions introduced during rebar manufacturing process. The results suggest that the hydroxyl ions in the alkali solution do not diffuse into the polymer matrix. Addition of alkali into water did not lead to a significant difference in water absorption dynamics and DMTA behaviour of pure Atlac 580 vinylester resin. Thirdly, fractured glass rebars, subjected to stress and water or alkali solution at 40°C, were studied. It was observed that low stresses resulted in relatively planar cracks normal to the applied tensile stress but did not pose significant damage to the interphase. The opposite was true for rebars under high-levels of stress. Alkali solutions accelerated the occurrence of stress corrosion in terms of failure times. It was found that crosslinked vinylester resin exhibited a diphasic structure as detected by modulated temperature differential scanning calorimetry (MDSC). Based on these results, it is proposed that microcracks form in the polymer matrix of the composite (under low stresses) due to the different responses of the two phases to the stress field at crack tips. Microcracking then allows transport of aqueous media into the composite by a percolation process.

Style APA, Harvard, Vancouver, ISO itp.

9

Purnell, Philip. "The durability of glass fibre reinforced cements made with new cementitious matrices." Thesis, Aston University, 1998. http://publications.aston.ac.uk/13285/.

Pełny tekst źródła

Streszczenie:

Matrices with reduced alkalinities and Ca(OH)2 contents are being developed; the aim of this study was to investigate their hydration and interaction with alkali-resistant fibres to determine the factors controlling their long-term durability, and assess the relevancy of accelerated ageing. The matrices studied were: OPC/calcium-sulphoaluminate cement plus metakaolin (C); OPC plus metakaolin (M); blast-furnace slag cement plus a micro-silica based additive (D); and OPC (O). Accelerated ageing included hot water and cyclic regimes prior to tensile testing. Investigations included pore solution expression, XRD, DTA/TG, SEM and optical petrography. Bond strength was determined from crack spacings using microstructural parameters obtained from a unique image analysis technique. It was found that, for the new matrices - pore solution alkalinities were lower; Ca(OH)2 was absent or quickly consumed; different hydrates were formed at higher immersion temperatures; degradation under 65°C immersion was an order of magnitude slower, and no interfilamental Ca(OH)2 was observed. It was concluded that: fibre weakening caused by flaw growth was the primary degradation mechanism and was successfully modelled on stress corrosion/static fatigue principles. OPC inferiority was attributed partly to its higher alkalinity but chiefly to the growth of Ca(OH)2 aggravating the degradation; and hot water ageing although useful in model formulation and contrasting the matrices, changed the intrinsic nature of the composites rather than simply accelerating the degradation mechanisms.

Style APA, Harvard, Vancouver, ISO itp.

10

Henault, Jean-Marie. "Approche méthodologique pour l’évaluation des performances et de la durabilité des systèmes de mesure répartie de déformation : application à un câble à fibre optique noyé dans le béton." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1113/document.

Pełny tekst źródła

Streszczenie:

La surveillance des structures de génie civil, afin d'en estimer l'état de santé, est un enjeu majeur pour les maîtres d'ouvrages. Les systèmes de mesures réparties par fibre optique, composés d'un interrogateur connecté à une fibre optique intégrée dans un câble, permettent de mesurer le profil de déformation avec un pas de mesure centimétrique et une portée kilométrique. Ils sont donc adaptés aux structures présentant de grands linéaires ou de grandes surfaces. Mais, avant tout déploiement industriel, il est nécessaire d'en évaluer leurs performances. Du fait de la déformation par cisaillement du revêtement du câble, le profil de déformation mesuré le long de la fibre optique n'est pas strictement identique à celui du matériau environnant. Une méthode, basée sur la mise en œuvre d'essais et de simulations numériques, a été développée afin de caractériser les mécanismes de transfert d'effort du milieu hôte à la fibre optique à travers le revêtement du câble. Cette méthode a été appliquée pour déterminer la réponse mécanique d'un câble particulier noyé dans le béton. Les performances métrologiques d'un système de mesure donné ont été évaluées sur la base d'une analyse d'essais « du laboratoire au terrain ». Cette étude a permis de quantifier les différentes composantes d'incertitude et d'estimer les performances du système de mesure complet. Enfin, le câble, noyé dans le béton, ne peut être remplacé. La connaissance de l'impact du vieillissement sur la réponse mécanique du câble est donc primordiale. Une étude spécifique est menée dont le but est d'estimer la durabilité du câble face aux sollicitations chimique, thermique et mécanique correspondant à une application donnée Structural Health Monitoring is a key factor in life-cycle management of civil structures. Truly distributed fiber optic sensors, composed by an optoelectronic device paired with an optical fiber in a cable, provide strain profiles over several kilometers with a centimeter resolution. They are thus able to provide relevant information on large structures. However, a preliminary performance assessment is required prior to any industrial application. Due to shear deformation of the cable's protective coating, strain measurements provided by the measuring system may differ from actual strains in the embedding medium. A methodology, based on mechanical tests and modelling, was thus developed to determine the relationship between measured/actual strains. It was applied to determine the mechanical response of a specific cable embedded in concrete. Performance assessment method was applied to a specific measuring system. Tests were carried out under laboratory conditions on the fiber optic cable, out of the concrete medium in a first stage, and then embedded in concrete structures. It enabled to evaluate its components and standard uncertainties. The cable could not be replaced after being embedded in concrete. It is necessary to evaluate the ageing effects on its mechanical properties to use it for a long term period. A specific study was carried out to determine the cable durability under chemical, thermal and mechanical solicitations

Style APA, Harvard, Vancouver, ISO itp.

11

Ammar, Mohamed Amine. "Bond durability of basalt fibre-reinforced polymers (BFRP) bars under freeze-and-thaw conditions." Thesis, Université Laval, 2014. http://www.theses.ulaval.ca/2014/30559/30559.pdf.

Pełny tekst źródła

Streszczenie:

Ce mémoire présente les résultats de l’étude de l’adhérence entre les barres en polymères renforcés de fibres de Basalte (PRFB) et le béton. Cinquante-quatre cylindres renforcés par des barres en PRFB et dix-huit cylindres renforcés par des barres en polymères renforcés de fibres de fibres de Verre (PRFV) ont été testés par le test d’arrachement. Les paramètres des tests incluent le type de la barre utilisée, le diamètre de la barre, la longueur d’ancrage et le nombre de cycles de gel-dégel (100 et 200 cycles). Les courbes adhérence-glissement des barres en PRFB et PRFV révèlent la même tendance. Les influences des différents paramètres sur l’adhérence ont été analysées. Les modèles analytiques BPE, BPE-modifié et CMR ont été calibrés pour décrire la relation adhérence-glissement des barres en PRFB. Les résultats montrent la capacité des barres en PRFB à remplacer les barres en PRFV dans le renforcement des structures. This thesis presents the test results of a study on the bond behavior of basalt fiber-reinforced polymers (BFRP) bars in concrete. Forty-five cylinders reinforced with BFRP bars and eighteen cylinders reinforced with glass fiber-reinforced polymer (GFRP) bars were tested in direct pullout conditions. Test parameters included the FRP material, the bar diameter, the bar’s embedment length in concrete and the number of freeze-and-thaw cycles (100 and 200 cycles). Bond-slip curves of BFRP and GFRP bars revealed similar trend. All BFRP specimens failed in a pullout mode at the bar-epoxy interface. The influence of various parameters on the overall bond performance of BFRP bars is analyzed. The BPE, modified-BPE, and CMR analytical models were calibrated to describe the bond-slip relationships of BFRP bars. Results demonstrate the promise of using BFRP bars as an alternative to GFRP bars in reinforcing concrete elements.

Style APA, Harvard, Vancouver, ISO itp.

12

Zhu, Wenzhong. "Effect of ageing on durability and micro-fracture mechanism of fibre reinforced cement composites." Thesis, University of the West of Scotland, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259743.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

13

Etches, J. A. "Interfacial and durability aspects of extrinsic Fabry-Perot interferometric sensors in carbon fibre composites." Thesis, Cranfield University, 2003. http://hdl.handle.net/1826/779.

Pełny tekst źródła

Streszczenie:

This thesis is concerned with the interfacial and durability aspects of Extrinsic Fabry- Perot Interferometric (EFPI) sensors embedded in carbon fibre reinforced composites. Fibre optic sensors are being used in many long term applications and, as is the case for all sensor types, the ability of the EFPI sensors to monitor accurately the measurands of interest over the lifetime of the structure must be proved. Therefore, the aim of this work was to examine the interface between the EFPI sensors and the structures, and then to evaluate the durability of that interface and the sensors. The first stage was an examination of the EFPI sensors including the method of manufacture, interrogation option and inherent strength of the sensors. It was found that the sensors have a very low tensile load to failure (~0.5 N). This was improved by using a resin reinforcement, which was applied to the capillary ends. However, this had implications for the overall sensor size and that influenced their embedment suitability. The second stage was interfacial characterisation; this was achieved through the examination of the surface energy of the sensors, carried out by contact angle measurements; and the interfacial shear strength of the sensors to matrix, using a new variation on the single fibre pull-out technique that involved the use of optical fibres and composite prepreg. Overall, it was found that the silane treatment of the fibres increased the surface energy but for the interfacial shear results the data was less conclusive due to the scatter present within the results. The durability of the sensors was examined through their embedment into carbon fibre composite samples and exposure to tension/compression fatigue loading. From initial quasi-static work it was found that the embedment of the sensors had no significant effect on the composite samples. However, the sensors failed at a strain levels of 0.4% in tension and at 1.1% in compression; the compression strain level was at the point of composite failure. Under fatigue loading the sensors could survive a million cycles at R=-1 at a max stress level of 156 MPa and maintain their reliability. If the tensile loading was increased then the sensors would fail within a few thousand cycles. However, if the compressive stress was increased the sensors survived but the reliability was affected. Overall, it was felt that with some improvements to the sensor design they should be able to survive and provided useful data when exposed to axial tension/compression fatigue regimes.

Style APA, Harvard, Vancouver, ISO itp.

14

Page, Jonathan. "Formulation et caractérisation d'un composite cimentaire biofibré pour des procédés de construction préfabriquée." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC244/document.

Pełny tekst źródła

Streszczenie:

Les enjeux économiques liés à la hausse des coûts des ressources fossiles, leur raréfaction, et les impacts environnementaux inhérents à leur fabrication et à leur utilisation, conduisent les acteurs de la construction à s’orienter vers des matériaux biosourcés. Les ressources issues de la biomasse sont alors au premier plan, celles agricoles notamment, dont les fibres provenant des tiges des plantes. Parmi ces fibres, le lin se démarque en raison de ses propriétés mécaniques élevées et sa faible densité, et sa disponibilité en Normandie. L’objectif de cette étude est de développer un matériau composite innovant par l’association des fibres de lin à une matrice cimentaire, qui sera utilisé dans des procédés de construction préfabriquée. Après la caractérisation fine des constituants de départ, nous avons d’abord décrit en détail l’élaboration des mortiers et bétons biofibrés avec un focus sur la méthodologie de formulation. Puis nous avons analysé l’influence de l’incorporation des fibres de lin sur les propriétés rhéologiques (air occlus, consistance, ouvrabilité et fluidité) et physico-chimiques (pH, ATG). Les propriétés physiques (porosité, module d’élasticité) et mécaniques (contraintes à la rupture, indice de ténacité) ont été mesurées par des essais de flexion et de compression à l’état durci. Ces résultats montrent nettement que la présence des fibres de lin réduit de façon importante les propriétés technologiques des pâtes cimentaires, du fait la sensibilité des fibres au milieu très alcalin et de leur caractère fortement hydrophile. Bien que les traitements de surface des fibres expérimentés (plasma atmosphérique, enrobage coulis de ciment et laitier de hauts fourneaux ou à l’huile de lin) aient permis d’améliorer certaines propriétés des mortiers, ils n’ont pas permis de réduire dans le temps la dégradation des fibres au sein de la matrice cimentaire (hydrolyse alcaline des fibres et leur minéralisation sous l’action de l’hydroxyde de calcium). Il apparaît donc nécessaire de recourir à des liants alternatifs pour tenter d’améliorer la durabilité de ces biocomposites à fibres végétales. Ainsi, de nouvelles formulations de mortiers et bétons sont proposées, dans lesquelles le ciment Portland est remplacé partiellement par le métakaolin / le laitier de hauts fourneaux ou totalement par un ciment sulfo-alumineux, sans préjudices pour le comportement rhéologique. L’étude des nouveaux composites formulés avec le métakaolin ou le ciment sulfo-alumineux indique des niveaux de résistance mécanique et de ténacité élevés. Leurs résistances au gel supérieures au béton classique ou celui incorporant des fibres de verre tient à la forte teneur en air (les fibres jouent un rôle d’agent entraîneur d’air) The economic issues linked to the rising costs of fossil resources, their scarcity, and the environmental impacts inherent in their manufacture and use, are leading the construction industry to move towards bio-based materials. The resources from biomass are then in the foreground, especially agricultural ones, including fibres from plants stems. Among these fibres, flax stands out because of its high mechanical properties and low density, and its availability in Normandy. The objective of this study is to develop an innovative composite material by combining flax fibres with a cement matrix, which will be used in prefabricated construction processes. After the fine characterization of the initial constituents, we first described in detail the development of plant fibre-reinforced mortars and concretes with a focus on the formulation methodology. Then we analysed the influence of the incorporation of flax fibres on the rheological properties (entrapped air, consistency, workability) and physico-chemical properties (pH, ATG). The physical properties (porosity, modulus of elasticity) and mechanical properties (compressive and tensile strength, toughness index) were measured by bending and compressive tests in the hardened state. These results clearly show that the presence of flax fibres significantly reduces the technological properties of cementitious pastes, because of the sensitivity of the fibres to the highly alkaline medium and their highly hydrophilic nature. The surface treatments of the experimental fibres (by using atmospheric plasma, cement grout coating, blast furnace slag or linseed oil) have effectively improved some properties of mortars, the degradation of the fibres within the cement matrix remain active over the long term (alkaline hydrolysis of the fibres and their mineralization under the action of calcium hydroxide). It therefore appears necessary to use alternative binders in an attempt to improve the durability of these plant fibre biocomposites. Thus, new formulations of mortars and concretes are proposed, in which the Portland cement is partially replaced by metakaolin / blast furnace slag or totally by sulfoaluminate cement, without prejudice to the rheological behaviour. The study of the new composites formulated with metakaolin or sulfoaluminate cement indicates high levels of mechanical strength and toughness. Their resistance to frost superior to conventional concrete or concrete incorporating glass fibres is due to the high air content (the fibres act as an air-entraining admixture)

Style APA, Harvard, Vancouver, ISO itp.

15

Jia, Yunlong [Verfasser], and Bodo [Akademischer Betreuer] Fiedler. "Durability of flax fibre/bio-epoxy sustainable composites for structural application / Yunlong Jia ; Betreuer: Bodo Fiedler." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2020. http://d-nb.info/1205370765/34.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

16

Batuwitage, Chamila Rajeev Jayanath. "Evaluation of environmental durability and bond characteristics of carbon fibre reinforced polymer (CFRP) strengthened steel structures." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/106775/1/Chamila%20Rajeev%20Jayanath_Batuwitage_Thesis.pdf.

Pełny tekst źródła

Streszczenie:

This thesis evaluates the environmental durability and bond characteristics of carbon fibre reinforced polymer (CFRP)-strengthened steel structures. The findings of this research provide a valuable contribution to the knowledge of CFRP-steel strengthening systems which can be used to evaluate the durability performance of CFRP-steel strengthening systems. Various parameters which related to the durability of CFRP-steel strengthening systems were investigated and evaluated. The outcomes of this research will be beneficial to the structural engineers when designing and assessing CFRP-steel systems.

Style APA, Harvard, Vancouver, ISO itp.

17

Sato, Taijiro. "An AC impedance spectroscopy study of the freezing-thawing durability of Wollastonite micro-fibre reinforced cement paste." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6357.

Pełny tekst źródła

Streszczenie:

The AC impedance spectroscopy (ACIS) is an electrochemical technique used to characterize materials in various research fields owing to its non-destructive nature. The ACIS, accordingly, appears to have a potential as a non-destructive technique to investigate the durability of cement paste. An understanding of the mechanism of frost action occurring within cement paste, a key binding component of concrete, is necessary to improve the durability of concrete with respect to freezing and thawing, particularly where the winter is severe. In addition, the research on the effectiveness of the wollastonite micro-fibres, a cost-effective naturally occurring calcium silicate, as a reinforcing material to improve the durability of cement paste is demanded due to worldwide concerns of material shortages. Three primary objectives in this study are to further the understanding of the mechanism of frost action within cement paste subjected to freezing and thawing, to investigate the potential of the ACIS as a new technique to determine the durability of cement paste with respect to freezing and thawing and to investigate the durability of the wollastonite micro-fibre reinforced cement paste to freezing and thawing. (Abstract shortened by UMI.)

Style APA, Harvard, Vancouver, ISO itp.

18

Chilali, Abderrazak. "Étude expérimentale et modélisation de la durabilité des biocomposites à fibres de lin." Thesis, Reims, 2017. http://www.theses.fr/2017REIMS003/document.

Pełny tekst źródła

Streszczenie:

Dans cette étude doctorale, nous proposons d’étudier la durabilité de deux matériaux composites à matrices thermodurcissable et thermoplastique renforcées par des tissus sergé de lin. Nous analysons d’abord la cinétique de diffusion d'eau dans les deux composites par identification de leurs paramètres de diffusion 3D, via une approche d’optimisation basée sur les modèles de Fick et de Langmuir 3D. Nous étudions ensuite l’effet de plusieurs paramètres géométriques et l’orientation des fibres sur la cinétique de diffusion d’eau au sein des deux composites. Nous analysons par la suite l'effet du vieillissement hydrique sur leurs propriétés élastiques et à la rupture. Enfin, nous proposons une analyse numérique par éléments finis de la diffusion d’eau au sein des deux composites et de leur comportement hydro-élastique. Nous estimons ainsi les paramètres de diffusion de la fibre de lin et des matrices à travers une approche numérique inverse, en décrivant la section et l’ondulation des mèches de lin au sein des deux matériaux. Nous montrons en particulier que les composites non vieillis présentent un comportement mécanique proche de l'effet Kaiser. Cependant, les composites vieillis présentent clairement un effet Felicity, ce qui indique la présence significative d’endommagements induits par l’absorption d'eau. Nous affirmons enfin que l’analyse numérique permet d’identifier d’importantes concentrations de contraintes pouvant induire des endommagements microstructuraux au sein des composites étudiés In this thesis work, we study the durability of two twill flax fabrics reinforced thermosetting and thermoplastic composites. Firstly, the diffusion behaviour of these composites is investigated by identifying their 3D Fick’s and Langmuir’s diffusion parameters using an optimization algorithm. The influence of several geometric parameters and fibre orientation on their 3D moisture diffusion is also studied. Then, we analyse the effect of water ageing on their elastic and failure properties. Finally, a numerical finite element analysis is performed in order to study their diffusive and hydro-mechanical behaviour. The water diffusion parameters of the flax fibre and the used resins are estimated by a numerical inverse analysis exploiting experimental water uptake data. The heterogeneity of the studied composites is considered by modelling the twill weave fabrics undulation of their unit-cell. In particular, the mechanical behaviour of the unaged composites is found to exhibit a Kaiser effect contrary to the aged materials which exhibit a significant Felicity effect synonymous of substantial damage induced by water ageing. Besides, it is found that high mechanical stress concentrations are developed at the fibre-matrix interface, which could cause damage initiation and lead to the final composite failure

Style APA, Harvard, Vancouver, ISO itp.

19

Poussines, Laurence. "Développement de nouveaux matériaux pour l'infusion de composites." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0132/document.

Pełny tekst źródła

Streszczenie:

Ce travail de thèse vise à adapter un système polymère au procédé d’élaboration par infusion d’une structure en matériaux composite pour fuselage d’avion. Ce système doit répondre à certaines exigences de viscosité, de température d’infusion, de stockage mais également de prix. La méthodologie mise en place consiste à s’approprier le procédé de mise en oeuvre afin de valider le choix des résines, de les caractériser à l’état initial et enfin d’étudier leur durabilité vis-à-vis d’un vieillissement hygrothermique. La caractérisation des propriétés a mis en évidence des comportements différents à l’état initial en termes de transition vitreuse, résilience et viscosité. L’étude du vieillissement hygrothermique montre une chute des propriétés fortement liée à l’évolution chimique des réseaux polymères qui a pour origine majeure l’hydrolyse de plusieurs liaisons. Enfin, un test d’adhérence est mis en place afin d’évaluer l’interface fibre/résine. Ce test a permis d’estimer les différents traitements de surface effectués sur les fibres The work presented in this thesis was done to adapt a polymer to selected elaboration process by infusion of a composite material structure for an aircraft fuselage. The polymer system must meet certain requirements such as viscosity, infusion temperature, storage but also the price. Our methodology is to understand the process putting into practice in order to validate the resins choice, to characterize the initial state and the study their sustainability towards a hydrothermal ageing. Properties characterization showed different behaviours in initial state, in terms of glass transition, resilience and viscosity. The study of hydrothermal ageing reveals a drop properties closely related to the chemical evolution of polymer networks which has for major origin multiple links hydrolysis. At least an adherence test is carried out to assess the interface fiber/resin. This test was used to estimate the different surface treatments on the fiber

Style APA, Harvard, Vancouver, ISO itp.

20

Römhild, Stefanie. "Transport Properties and Durability of LCP and FRP materials for process equipment." Doctoral thesis, KTH, Polymera material, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-13221.

Pełny tekst źródła

Streszczenie:

This thesis focuses on transport properties and durability of liquid crystalline polymers (LCP)and fibre reinforced plastics (FRP) with regard to application in industrial process equipment.In the first part of the study the possibility of using a thermotropic LCP of type Vectra A950as lining material for FRP process equipment was investigated. Its performance wascompared to that of a fluorinated ethylene propylene copolymer (FEP) with respect tochemical and permeation resistance. Transport property and chemical resistance data wereestablished for different types of LCP film (compression molded, uniaxially and biaxiallyoriented film) exposed to selected chemicals chosen to represent typical industrial processenvironments. Annealing of the LCP, which may reduce the disclination density and henceimprove the barrier properties, induced a crystallinity increase, but did not significantlyimprove the barrier and chemical resistance properties. Different surface treatments toincrease the bonding between the LCP and FRP were explored. The conclusion was that LCPhas potential to serve as lining material for FRP in contact with water, organic solvents andnon-oxidizing acid environments, although certain issues, such as jointing techniques, stillhave to be evaluated. The second part of the study focused on transport and long-termproperties of commercial thermoset and FRP materials for industrial process equipment inaqueous environments (50 – 95 °C, water activity 0.78 – 1, exposure time ≤ 1000 days). Thewater transport properties in different thermosets were related to their chemical structureusing the solubility parameter concept. The transport of water in the thermosets with differentchemical structures could be predicted from the water activity, regardless of the actual type ofionic or non-ionic solute in the solution. An empirical relationship, independent of boththermoset chemistry and temperature, was established to describe the water concentration inthe thermoset as a function of water activity and the water concentration in pure water. Inlong-term, the water concentration in the thermosets increased with exposure time. Thisseemed to be primarily related to stress relaxation processes induced by water absorption andcertain leaching effects. The effects of hydrolysis seemed to be small. The glass fibrereinforcement may to various extents affect the water transport properties by capillarydiffusion and additional absorption around fibre bundles. The extent of such processesseemed to depend on temperature, water activity and the type of thermoset and reinforcement.The present work may be a useful contribution to an increased understanding of water effectsand durability of FRP process equipment. However, open questions still remain for a morecomprehensive durability analysis. QC20100629

Style APA, Harvard, Vancouver, ISO itp.

21

Sinicropi, Daniela [Verfasser], and Prof Dr Ing Harald [Akademischer Betreuer] Budelmann. "Experimental Investigation on the Durability of Fibre Reinforced Cementitious Materials for Strengthening of Masonry / Daniela Sinicropi ; Betreuer: Prof. Dr.-Ing. Harald Budelmann." Braunschweig : Technische Universität Braunschweig, 2015. http://d-nb.info/1175819085/34.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

22

Hazra, Kalyan. "The influence of stitch architecture in multiaxial warp-knit fabrics on the damage tolerance and environmental durability of carbon fibre-reinforced composites." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/34825.

Pełny tekst źródła

Streszczenie:

Among all the 3D textile reinforcements, Multiaxial Warp Knit (MWK) fabrics have brought together the advantages of textile technology: high deposition rates, unlimited shelf-life, lower cost and finally an improvement in the damage tolerance by the use of stitching. However, the stitching in MWKs is slightly different from that traditionally used, i.e. overstitching. The effect of this type of stitching has been investigated and is reported in this work. Three different variants of stitch architectures of carbon MWK, used in an epoxy matrix, were considered. Interlaminar shear strength, low energy impact, through penetration impact and compression strength testing were carried out on dry samples, while interlaminar shear strength, compression strength, DMTA, FTIR, Raman spectroscopic analysis were carried out on aged samples.

Style APA, Harvard, Vancouver, ISO itp.

23

Hallonet, Anne. "Développement et caractérisation d'un matériau composite à base de fibres de lin : application au renforcement de structures en béton par collage externe." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1111/document.

Pełny tekst źródła

Streszczenie:

Afin de prolonger leur durée de vie et d'assurer la sécurité des usagers, les structures en béton peuvent nécessiter un renforcement au cours de leur durée de service. La technique de renforcement par collage externe, en surface, de composites renforcés de fibres de carbone, de verre ou d'aramide à l'aide de résines durcissant à température ambiante est largement employée pour son efficacité et sa facilité de mise oeuvre. Toutefois l'utilisation à la fois de fibres synthétiques et de matrices polymères produit un impact écologique non négligeable. L'objectif de ce travail de recherche est d'examiner la possibilité d'utiliser des fibres de lin pour le renforcement externe de structures en béton. Les propriétés mécaniques spécifiques et le bilan environnemental avantageux des fibres de lin en font une alternative intéressante aux fibres de verre. Cependant leur origine naturelle conduit à une plus grande variabilité des propriétés, à un comportement en traction non linéaire et une sensibilité accrue à l'humidité. Les principaux objectifs du travail de thèse portent ainsi sur la sélection des matériaux et la mise en oeuvre les plus adaptés, sur l'évaluation des performances du matériau et de son adhérence au support béton et sur une évaluation de la durabilité des propriétés du système. Dans une première partie expérimentale deux méthodes de mise en oeuvre du renfort à fibres de lin (stratification au contact et collage de lamelles rigides) sont développées et caractérisées. Des observations tomographies X confirment la bonne imprégnation des fibres et la cohésion des composites. Les essais de traction révèlent un comportement en traction bilinéaire comme décrit dans la littérature, avec des propriétés d'effort par largeur de bande comparables aux composites de renfort à fibres de verre. La caractérisation des interfaces composite/béton menée par tests de cisaillement à double recouvrement confirme une bonne adhérence qui se traduit par une rupture cohésive dans le substrat béton. La nature des fibres ne semble pas influencer le comportement de l'interface. Les systèmes de renforcement à fibres de lin sont donc capables de reprendre des efforts transmis par cisaillement de façon comparable aux matériaux de renfort à fibres de verre. Dans une deuxième partie des essais exploratoires de durabilité ont ensuite été menés pour vérifier la pérennité des propriétés de ces deux composites de renfort dans un environnement de service. Un vieillissement accéléré artificiel en enceinte climatique est mis en place tandis que des composites à fibres de lin stratifié au contact sont exposés pendant un an à l'environnement extérieur. Un second vieillissement hygrothermique à 70°C est mené pendant 4 semaines. Les dégradations des propriétés des composites à fibres de lin sont comparables à celles de certains composites de renfort à fibres de verre. Malgré la nature hydrophile des fibres de lin, les premiers essais ne montrent pas de dégradations des propriétés qui rendraient le composite impropre à une utilisation comme renfort extérieur de structures en béton To extend their life and ensure the safety of users, concrete structures may need strengthening during their service life. The technique of strengthening by external bonding of composites carbon, glass or aramid composites using polymer that are cured at room temperature is widely used for its effectiveness and ease of implementation. Yet the uses of both synthetic fibers and polymer matrices have a significant environmental impact. The objective of this research is to examine the possibility of using flax fibers for the external strengthening of concrete structures. Their high specific mechanical properties and positive environmental balance make them an interesting alternative to the glass fibers. However, they also present a larger variability in properties, a non-linear tensile behavior and high sensitivity to humidity. The main objectives of this thesis involve the selection of the materials and the most suitable implementation, the evaluation of the materials’ performances and adherence to concrete support and a sustainability assessment of those properties. In a first experimental section, two methods of implementation of the flax fiber reinforcement are developed and characterized: by wet lay-up and by bonding of pre-hardened. Tomography observations confirm the good fiber impregnation and cohesion of the composites. The tensile tests show a bilinear tensile behavior as described in the literature, with stress per width at failure comparable to glass fibres strengthening systems. The characterization of composite/concrete interfaces is conducted by double overlap shear tests and confirms a good adhesion which results in concrete failure before the failure of the reinforcement system. The nature of the fibers does not appear to influence the shear behavior of the interface. For glass or flax wet lay-up systems, failure can occur with failure of the composite. Flax fiber reinforcement systems can take up the forces transmitted by shear in a manner comparable to glass composites. In the second part, sustainability tests were conducted to ensure the sustainability of the properties of these two composite reinforcements in a service environment. An artificial accelerated aging test in a climatic chamber is set up while wet lay-up flax fiber composites are exposed to the external environment during a year. A second hydrothermal aging test is conducted for 4 weeks at 70°C. The degradations of the properties of the flax composites are comparable to those of some glass reinforcement composites. Despite the hydrophilic nature of the flax fibers the first tests show no degradation of properties that would make the composite unsuitable for an external reinforcement of concrete structures

Style APA, Harvard, Vancouver, ISO itp.

24

Estoup, Jean-Marie. "Etude de la carbonatation endogene du beton et de ses applications a l'industrie du beton manufacture." Paris 6, 1987. http://www.theses.fr/1987PA066362.

Pełny tekst źródła

Streszczenie:

Etude bibliographique et experimentale de l'hydratation et de la carbonation du beton en dispersant dans la masse des polyisocyanates (hmdi ou mdi, qui accelerent l'hydratation, et ipdi, qui la retardent). Analyse des reactions. Resultats prometteurs de l'application de la technique pour ameliorer la stabilite de la teinte des betons colores, les resistances mecaniques a court terme, la tenue aux agents agressifs et la durabilite des fibres de verre dans une matrice de ciment

Style APA, Harvard, Vancouver, ISO itp.

25

Seghini, Maria Carolina. "Mechanical Analysis and Fibre/Matrix Interface Optimization for Next Generation of Basalt-Plant Fibre Hybrid Composites." Electronic Thesis or Diss., Chasseneuil-du-Poitou, Ecole nationale supérieure de mécanique et d'aérotechnique, 2020. http://www.theses.fr/2020ESMA0003.

Pełny tekst źródła

Streszczenie:

La prise de conscience mondiale des enjeux environnementaux a conduit à l’émergence de composites«verts», dans lesquels les fibres naturelles sont amenées à remplacer les fibres synthétiques. Ces nouveaux matériaux offrent des alternatives écologiques aux composites synthétiques traditionnels mais sont difficilement utilisables pour des applications semi-structurales ou structurales. Une solution possible à ce problème est le développement des composites hybrides, en combinant ensemble fibres naturelles et synthétiques. Dans ce cadre, l'objectif de cette étude était de développer des composites hybrides à base de fibres de basalte et de lin. Les composites hybrides ont été élaborés par moulage par infusion sous vide avec une matrice époxy. À des fins de comparaison,des composites 100% à fibres de lin et100%à fibres de basalte ont également été produits. Une caractérisation mécanique quasi-statique et dynamique amontré que l'hybridation permet d’obtenir un composite avec des propriétés mécaniques intermédiaires comparées à celles des composites à fibres de lin ou de basalte. Cependant, l’analyse approfondie des dommages a montré la nécessité d'optimiser la qualité d'adhésion de l'interface fibre/matrice afin d'accroître les performances mécaniques des composites hybrides obtenus. Pour cette raison, différents traitements de modification de surface ont été développés et étudiés pour les fibres de lin et de basalte. Un traitement physique par plasma (Plasma Enhanced Chemical Vapor Deposition) a été appliqué aux fibres de lin et de basalte. Les fibres de lin ont également été soumises à deux traitements chimiques utilisant des espèces enzymatiques et du CO2supercritique. Les effets des traitements sur la stabilité thermique, la morphologie et les propriétés mécaniques des fibres de lin et de basalte ont été étudiés. L’adhérence fibre/matrice a été analysée en réalisant des tests de fragmentation sur des composites monofilamentaires. La qualité de l'adhésion entre les fibres et les matrices époxy et vinylester a été évaluée en termes de longueur critique de fragment, de longueur de décohésion interfaciale et de résistance au cisaillement interfacial. La micto-tomographie haute résolution a été utilisée pour analyser les mécanismes d'endommagement lors des tests de fragmentation. Pour les deux types de fibres, les meilleurs résultat sont été obtenus grâce au traitement par plasma. Ce traitement a consisté à déposer un revêtement homogène de tétravinylsilane à la surface des fibres de basalte et de lin, ce qui a permis une augmentation significative de l’adhérence fibre/matrice, ouvrant ainsi la voie à la prochaine génération de composites hybrides plus respectueux de l’environnement et utilisables pour des applications semi-structurales Global awareness of environmental issues has resulted in the emergence of “green” composites, in which natural fibres are used to replace synthetic ones. However, in semi-or structural applications, it can be inconvenient to use composites based on natural fibres. A possible solution to this problem is the development of hybrid composite materials, combining together plies of natural and synthetic fibres. In this framework, the aim of this research project was to develop basalt-flax fibre hybrid composites with a view to obtaining more environmentally friendly composites for semi-structural applications. Hybrid composites were produced through vacuum infusion molding with epoxy matrix.For comparison purposes, 100% flax fibre composites and 100% basalt fibre composites were also manufactured. A quasi-static and dynamic mechanical characterization showed that the hybridization allows the production of a composite with intermediate mechanical performances compared to those possessed by flax and basalt composites. However, the damage analysis has revealed the need to optimize the fibre/matrix interface adhesion quality, in order to increase the mechanical properties of the resulting hybrid composites. For this reason, different surface modification treatments have been specifically designed and investigated for flax and basalt fibres. Flax and basalt fibres were treated by the physical process of Plasma Enhanced Chemical Vapor Deposition. Flax fibres were also subjected to two chemical treatments using enzymatic species and supercritical CO2. The effects of the surface modification treatments on the thermal stability, morphology and mechanical properties of flax and basalt fibres have been investigated. The degree and extent of fibre/matrix adhesion were analyzed by micromechanical fragmentation tests on monofilament composites. The adhesion quality between fibres and both epoxy and vinylester matrices has been assessed in terms of critical fragment length, debonding length and interfacial shear strength. High-resolution μ-CT has been used to support the analysis of the damage mechanisms during fragmentation tests. For both flax and basalt fibres, the best results were obtained after the plasma polymer deposition process. This process was able to produce a homogeneous tetravinylsilane coating on the surface of basalt and flax fibres, which resulted in a significant increase in the fibre/matrix adhesion, thus paving the way for the next generation of more environmentally friendly hybrid composites for semi-structural applications

Style APA, Harvard, Vancouver, ISO itp.

26

Méchin, Pierre-Yves. "Contribution à l’étude de la résistance à la compression de stratifiés composites à fibres de carbone haut module : cas de chargements statiques et cycliques." Thesis, Lorient, 2017. http://www.theses.fr/2017LORIS434.

Pełny tekst źródła

Streszczenie:

Cette thèse est une contribution à la compréhension du comportement des composites carbone-époxy en compression par l’étude de l’influence des constituants (fibres et matrices). L’incidence d’un chargement mécanique d’amplitude constante ou variable sur la durabilité est étudiée et un modèle numérique permettant la prédiction de la résistance résiduelle est proposé. Une première partie des travaux s’intéresse aux mécanismes spécifiques engagés dans la résistance en compression. Un modèle analytique est retenu pour une confrontation expérimentale. Ce modèle propose de considérer d’une part le micro-flambage de la fibre comme contenu par le comportement en cisaillement de la matrice (Budiansky et Fleck, 1993). En complément, une partie supplémentaire de structure considérant, entre autres, l’influence du gradient de déformation induit dans une sollicitation en flexion 4 points est étudiée (Grandidier, 2002). Afin de valider la pertinence du modèle, une campagne expérimentale est menée sur six matrices époxy différentes (de fragile à ductile) dans des empilements stratifiés monolithiques identiques réalisés en cuisson autoclave. Ces résultats ont permis de valider la capacité du modèle à prédire l’influence de la rigidité de la matrice sur la résistance en compression. Le partie micro-flambage est validée pour la prise en compte de la matrice. La partie effet de structure (gradient ici) est validée par une comparaison avec des résultats supplémentaires obtenus sur des éprouvettes sandwich sollicitées en flexion. Ces dernières éprouvettes ont fait l’objet d’une conception spécifique afin de favoriser la rupture en compression pure (sans gradient de déformation). Une seconde partie est consacrée à l’étude de la durabilité en compression. Une campagne expérimentale d’essais de fatigue est menée en flexion 4 points sur les éprouvettes sandwich précédemment conçues. Les essais sont conduits à une fréquence de 10 Hz et différents rapports de charge dans une optique de dégager l’évolution de la résistance résiduelle. Un modèle numérique de changement d’échelles (stratifié, plis, constituants) est parallèlement développé, basé sur la dégradation et la plasticité de la matrice. On fait l’hypothèse de simplicité thermo-rhéologique de la matrice pour établir des courbes de maitresses à partir d’une série d’essais identifiés (fluage, relaxation, fatigue…). On utilise les propriétés résiduelles du pli (rigidité, résistance) pour estimer un indicateur d’endommagement. Ce dommage est répercuté dans les propriétés de la matrice au moyen d’une loi de dégradation linéaire. Une loi de cumul de dommage de type Miner est alors introduite pour tenir compte de la variabilité des chargements appliqués. Un solveur micro- mécanique est développé pour extraire le comportement non-linéaire du pli en cisaillement tenant compte de la dégradation. Ce comportement est paramétré par une loi de Ramberg-Osgood utilisée dans le modèle analytique validé précédemment. Les travaux des deux parties permettent donc la mise en place d’un outil de prédiction de la résistance résiduelle des plis sollicités dans un chargement biaxial plan, avec en particulier le traitement de la compression This PhD dissertation is a contribution to the modelling of Carbon-Fiber-Epoxy-Polymer laminates, undergoing specifically compression loadings, according to components. The aim is to build a design tool for composites structures taking into account this compression specificity for dimensioning racing yachts parts (masts, daggerboards, foils), which is the expertise of HDS/GSea-Design, the company associated to this work. Emphasis was put on the influence of linear or non-linear properties of each phase by varying the type of fibre (from high stiffness to high strength) and the type of matrix (from brittle to ductile). The effect of a mechanical loading, static, constant (creep, relaxation) or variable (fatigue) on durability is studied and a numerical model for predicting the residual strength is proposed. The first part of this work deals with the mechanisms involved in compressive strength. An analytical model is used for an experimental validation. It considers a contribution linked to the micro-buckling of the fibre as contained by the shear behaviour of the matrix (Budiansky et Fleck [1993]). It considers also a contribution of the deformation gradient induced for instance in a bending loading (Gardin et al. [2002]). To validate this model, an experimental campaign was conducted on six different epoxy matrices (from brittle to ductile) on identical monolithic stackings processed in autoclave. The results allowed the validation of the model capability to predict the influence of the matrix stiffness on the compressive strength of unidirectional laminas. Taking into account the matrix behaviour validates the micro-buckling contribution. Regarding the deformation gradient contribution, it is validated through a comparison using additional experimental results on sandwich samples in bending. The latter samples were specifically designed to favour a pure compression fracture (without any deformation gradient). The second part examines durability in compression. Another experimental campaign with fatigue tests was conducted with four points bending tests on the same sandwich samples. Experiments were carried out at 10 Hz and different load ratios were used to study their influence on the compressive residual strength. A numerical model involving different scales (laminate, laminas, fibres and matrix) is developed in parallel (Huang et al. [2012a]), based on the degradation and the plasticity of the matrix. The assumption of thermo-rheological simplicity of the matrix is made to build master curves from dedicated experiments (creep, relaxation). We then use the residual properties (stiffness, strength) of the ply to estimate a damage level. This latter parameter is used to modify the elastic stiffness of the matrix with a linear law. A Miner-type cumulative law is used in fatigue to take into account the different possible loadings. A micro-mechanical solver is developed to extract the non-linear shear behaviour of the ply accounting for this degradation. This behaviour is described by a Ramberg-Osgood law used in the analytical model described in the first part of this work. The joint contributions of these two parts allowed us to program a numerical tool for predicting the residual strength of plies undergoing a biaxial in- plane loading, being monotonous, constant or with a variable amplitude, with emphasis on the particular case of compression loading

Style APA, Harvard, Vancouver, ISO itp.

27

Ponsot, Bernard. "Influence de la matrice sur le comportement a long terme de composites carbone-epoxyde." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0058.

Pełny tekst źródła

Streszczenie:

Etat de degradation en fonction du temps d'un materiau soumis a des sollicitations thermomecaniques sur des plaques unidirectionnelles et des tubes (esais, traction, fluage, eclatement, flexion). Utilisation d'emission acoustique pour suivre l'evolution de la structure. Cinetique d'endommagement

Style APA, Harvard, Vancouver, ISO itp.

28

Butler, Marko, Simone Hempel, and Viktor Mechtcherine. "Zeitliche Entwicklung des Verbundes von AR-Glas- und Kohlenstofffaser- Multifilamentgarnen in zementgebundenen Matrices." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244045698955-31655.

Pełny tekst źródła

Streszczenie:

Mit zunehmendem Alter zeigt das Verbundverhalten von Multifilamentgarnen aus alkaliresistentem Glas (AR-Glas) oder Kohlenstoff in Abhängigkeit von der Zusammensetzung der zementgebundenen Matrix eine sehr unterschiedliche Entwicklung. Während bei AR-Glas teilweise drastische Verluste des Leistungsvermögens zu verzeichnen sind, treten diese bei Kohlefasern nicht auf. Zur Untersuchung der Phänomene wurden beidseitige Garnauszugversuche durchgeführt und die Interphase zwischen Filamenten und Matrix im Rasterelektronenmikroskop (ESEM) untersucht. Die unterschiedlichen mechanischen Eigenschaften stehen in Zusammenhang mit verschieden ausgeprägten Mikrostrukturen der Interphasen. Welche Ursachen die unterschiedliche morphologische Entwicklung der Interphasen hat, ist Gegenstand aktueller Arbeiten.

Style APA, Harvard, Vancouver, ISO itp.

29

Vève, Jean-Christophe. "Interpretation microstructurale de l'endommagement par fatigue mecanique des fibres de polyester pour le renforcement des elastomeres." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0065.

Pełny tekst źródła

Streszczenie:

Analyse de l'evolution microstructurale des monofilaments de polyester 1) au cours de la fatigue par microspectrometrie laser a effet raman, diffusion rx aux petits angles et analyse viscoelastique dynamique et 2)avant sollicitation par diffusion rx aux grands angles et spectrometrie ir. Modele microstructural a 4 phases. Relation microstructures durabilite

Style APA, Harvard, Vancouver, ISO itp.

30

Raman, Venkadesh. "A smart composite based on carbon fiber and epoxy matrix for new offshore wind-turbines. Multi-scale numerical and analytical modelings." Thesis, Ecole centrale de Nantes, 2017. http://www.theses.fr/2017ECDN0016.

Pełny tekst źródła

Streszczenie:

Les structures intelligentes fondées sur des matériaux composites ont été développées pour surveiller les structures qui doivent fonctionner dans des applications industrielles exigeantes, dans des environnements difficiles comme c’est le cas de l’aéronautique, de l’aérospatiale, du génie civil, des centrales nucléaires et chimiques ...). L'étude actuelle est axée sur la suggestion d’un nouveau matériau composite intelligent qui peut être utilisé avec succès dans les pâles d’éoliennes offshore de nouvelle génération. En effet, pour accentuer leur rendement, les pales de nouvelle génération doivent dépasser une longueur de 100m, ce qui représente actuellement une cible hors d’atteinte étant donné que les matériaux composites constitutifs sont fondés sur des fibres de verre, notamment connues pour être lourdes et dépourvues de rigidité significative. Par conséquent, le passage aux fibres de carbone (plus légères et 3 fois plus rigides) devient obligatoire. Dans cette thèse, nous proposons la mise en place d'un matériau composite intelligent à base de fibres de carbone et de matrice époxy (ici appeler matériau parent). Les capteurs à fibre optique (FOS) et les capteurs à résistance quantique (QRS) seront utilisés pour la détection de déformation dans toute la structure. Ce choix devrait permettre une documentation précise et un envoi instantané d'informations critiques aux ingénieurs. Pour atteindre cet objectif de développement d'un nouveau matériau intelligent pour une application critique dans la production d’énergie éolienne offshore, nous avons choisi de proposer un document de recherche regroupant plusieurs aspects du sujet, résumés en 5 chapitres. La thèse est fondée sur des modélisations numériques et analytiques. Le document n'a pas l'ambition d'être exhaustif. Il est destiné à présenter une recherche pragmatique qui met l'accent sur la façon dont les domaines de faiblesse mécanique peuvent être diagnostiqués, quelles sont les solutions qui peuvent être suggérées et comment nous pouvons les soutenir, quelles sont les questions relatives à l'utilisation de capteurs intégrés et les résultats expérimentaux qui permettent l'évaluation du statut actuel de la performance du matériau et les moyens d’en améliorer les performances Smart structures have been developed as to monitor structures that have to operate in demanding industrial applications with includes harsh environments (Aeronautics and aerospace, Civil engineering, nuclear and chemical power plants…), too. Current study is focused on the suggestion of new smart composite materials that can be successfully used for wind blade structures in offshore energy generation farms. Indeed, to bring expectable energy-generation performances, new generation wind blades have to exceed 100m length, which is a hardly achievable target given that actual constitutive composite materials are based on glass-fibers, that are notably known to be very heavy and lacking stiffness. Therefore, the switch to carbon fibers (lighter and stiffer) becomes mandatory. In this thesis, we propose the implementation of a smart composite material that is based on carbon fibers and epoxy matrix (here called parent material). Fiber Optic Sensors (FOS) and Quantum-Resistive Sensors (QRS) will be used for detection of over-strained areas all over the structure. This choice is expected to enable for accurate documentation and instant sending of critical information to engineers. To achieve this goal of development of a new smart material for a critical application in offshore wind generation, we have chosen to illustrate it in a research document that is grouping several aspects, summarized in 5 chapters. The thesis is conducted using numerical and analytical modelings. The document is not having the ambition to be exhaustive. It is intended to present a pragmatic research that emphasize how areas of mechanical weakness can be diagnosed, what are the solutions that can be suggested and how we can support them, what are the issues pertaining to the use of embedded sensors and some experimental results that give appraisal of current performance status and what could be future trends

Style APA, Harvard, Vancouver, ISO itp.

31

Mazáč, Jan. "Využití kevlarových vláken v asfaltových směsích." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240054.

Pełny tekst źródła

Streszczenie:

Diploma thesis deals with topic of using aramid (Kevlar) fibres in road engineering in asphalt mixtures. Theoretical part of thesis is describing characteristics of aramid fibres and their technical usage. Thesis deals with research and application of aramid fibres abroad and also in Czech Republic. Practical part deals with influence of aramid fibres, namely FORTA FI fibres in mixture with modified binder for wearing course. An integral part of this thesis is a description of all methods that were used during the processing of the practical part. In the end of the thesis there are outcomes of tests and theoretical research.

Style APA, Harvard, Vancouver, ISO itp.

32

Godoy, Vinícius Batista. "Desempenho de misturas de distintos materiais com cinza volante e cal submetidas a condições climáticas severas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/178361.

Pełny tekst źródła

Streszczenie:

A aplicação prática de resíduos industriais, como cinza volante proveniente da queima de carvão, em bases e sub-bases de rodovias, é de grande interesse para engenheiros geotécnicos, uma vez que reduz o consumo de recursos naturais e oferece um destino a esses resíduos. Nesse sentido, esta dissertação de mestrado avalia o desempenho de misturas cinza volante-cal submetidas a condições climáticas extremas. Foram analisadas as propriedades resistência, rigidez e durabilidade de misturas de cinza volante (25%) com areia de Osório, comparando-se ciclos de molhagem-secagem com ciclos de congelamento-degelo. Para isso variou-se: o teor de cal hidratada (3%, 5%, 7%), o grau de compactação (14,0 kN/m³, 15,0 kN/m³, 16,0 kN/m³), a adição de 0,5% de cloreto de sódio (NaCl) como catalisador e a adição de 0,5% de fibras de polipropileno. Foi estudada a influência da temperatura (23°C e 40°C) em um período de 7 dias de cura, chegando-se à conclusão que o aumento de temperatura proporciona elevados ganhos de durabilidade por congelamento e degelo, resistência e rigidez, assim como a adição de sal e fibras de polipropileno Visando ampliar esta pesquisa foi proposta a troca da matriz da mistura (areia de Osório) por fresado (RAP) e a cal hidratada pela cal de carbureto. Para esse novo tipo de mistura, também foi realizado ensaios triaxiais para análise do comportamento tensão-deformação em relação a adição de 0,5% de NaCl, onde percebeu-se um aumento de 3,4° no ângulo de atrito e de 42,8 kPa no intercepto coesivo. As misturas de RAP e cal de carbureto obtiveram melhores resultados de resistência por compressão e durabilidade do que as misturas com areia de Osório e cal dolomítica, para a mesma temperatura de cura. Posteriormente constatou-se que a perda de massa acumulada após os referidos tipos de ciclos é controlada pelo índice porosidade (η)/teor volumétrico de cal (Liv), para ambas as misturas. Além disso, percebeu-se que menores perdas de massa acumulada foram obtidas para os ciclos de molhagem e secagem comparados aos ciclos de congelamento e degelo, tanto para as misturas com areia quanto para as misturas com RAP. The practical application of industrial residues, such as coal fly ash, on bases and sub-bases of highways, is of great interest to geotechnical engineers, since it reduces the consumption of natural resources and gives a destination to these residues. In this sense, this master's thesis evaluates the performance of coal fly ash-lime mixtures under extreme climatic conditions. Was analysed the impact of the hydrated lime content (3%, 5%, 7%), the degree of compaction (14.0 kN/m³, 15.0 kN/m³, 16.0 kN/m³), the addition of 0.5% sodium chloride (NaCl) as a catalyst and the addition of 0.5% polypropylene fibers, on strength, stiffness and durability (comparing freezing-thawing to wetting-drying cycles), in fly ash mixtures (25%) with Osório sand. The influence of temperature (23 °C and 40 °C) in a period of 7 days of cure was also studied, this increase in temperature has been shown to provide high durability (for freezeing-thawing cycles), strength and stiffness gains, as well as addition of salt and polypropylene fibers. In order to extend this research, it was propose the exchange of the matrix’s mixture (Osório sand) by reclaimed asphalt paving (RAP) and lime hydrated by carbide lime For this new type of mixture, triaxial tests are also performed to analyze the stress-strain behavior in relation to the addition of 0.5% NaCl, where a 3.4° increase in the friction angle was observed, and 42.8 kPa in the cohesive intercept. The mixtures of RAP and carbide lime obtained better strength and durability results than mixtures with Osório sand and dolomitic lime, for the same cure temperature. Subsequently, It was verified that the accumulated loss of after these kinds of cycles is controlled by the index of porosity (η) / volumetric content of lime (Liv), for both mixtures. Besides that, lower losses of accumulated mass was observed for the wetting and drying cycles, compared to the freezing and thawing cycles.

Style APA, Harvard, Vancouver, ISO itp.

33

Phéron, Xavier. "Durabilité des capteurs à fibres optiques sous environnement radiatif." Phd thesis, Université Jean Monnet - Saint-Etienne, 2013. http://tel.archives-ouvertes.fr/tel-01058775.

Pełny tekst źródła

Streszczenie:

Nous avons étudié le comportement de capteurs répartis par rétrodiffusion Brillouin dans des fibres optiques soumises à des environnements radiatifs pour la mesure de contraintes thermomécaniques. Le premier chapitre présente le besoin de mesure répartie par fibre optique pour le stockage sur site géologique des déchets radioactifs de moyennes et hautes activités vie longue (MA-VL et HA-VL) envisagé par l'Andra. Le second chapitre précise la méthodologie utilisée durant la thèse. Le choix de fibres optiques utilisées ainsi que les moyens de caractérisation exploités pour étudier l'évolution de la réponse des fibres optiques y sont présentés. Dans la troisième partie, nous montrerons l'influence de l'exposition aux rayonnements UV sur le spectre Brillouin de certaines fibres optiques. La réponse de la fibre optique fortement dopées au Germanium montre une grande sensibilité de l'atténuation et des changements sur la fréquence Brillouin induits par des rayonnements UV. Dans la quatrième partie, nous montrerons les résultats de la méthodologie appliquée pour la caractérisation de la réponse capteurs répartis par rétrodiffusion Brillouin dans diverses fibres optiques au cours des irradiations gamma. Ces études ont permis de converger vers la conception d'une fibre optique spéciale dopée au Fluor qui est adaptée l'application de surveillance d'alvéole de stockage de déchets radioactifs de type HA-VL et MA-VL pendant une échelle séculaire

Style APA, Harvard, Vancouver, ISO itp.

34

Mohr, Benjamin J. "Durability of Pulp Fiber-Cement Composites." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7222.

Pełny tekst źródła

Streszczenie:

Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers. Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness losses) during wet/dry cycling. SCMs have been found to be effective in mitigating composite degradation through several processes, including a reduction in the calcium hydroxide content, stabilization of monosulfate by maintaining pore solution pH, and a decrease in ettringite reprecipitation accomplished by increased binding of aluminum in calcium aluminate phases and calcium in the calcium silicate hydrate (C-S-H) phase.

Style APA, Harvard, Vancouver, ISO itp.

35

Krishnaswamy, Vijayarajan. "Durability of nanoclay FRP bars for concrete members." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4568.

Pełny tekst źródła

Streszczenie:

Thesis (M.S.)--West Virginia University, 2006. Title from document title page. Document formatted into pages; contains xvi, 204 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 155-158).

Style APA, Harvard, Vancouver, ISO itp.

36

Chlela, Robert. "Durabilité d'un système composite biosourcé (matrice époxy-fibres de lin) pour applications de renforcement structural : approches expérimentale et fiabiliste." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2076.

Pełny tekst źródła

Streszczenie:

En France, le patrimoine bâti des ouvrages d’art et bâtiments est vaste et vieillissant. Des rapports récents établis par des experts dressent un constat alarmant de la situation et pointent la nécessité d’augmenter significativement les moyens alloués à la réhabilitation de ce patrimoine. Dans ce contexte, le renforcement structural par collage externe de matériaux composites s’est imposé depuis une vingtaine d’années comme une solution de choix pour la remise à niveau des ouvrages et l’extension de leur durée de vie. Cette thèse, financée par l'ANR, vise, en premier lieu à développer un système de renforcement composite inédit à empreinte environnementale réduite, et d’autre part, à construire d’une démarche fiabiliste permettant d’estimer la durée de vie des systèmes de renforcement et leur probabilité de défaillance à tout instant. Dans le présent manuscrit, les principales phases de développement du système bio-sourcé sont tout d’abord rappelées. On y rappelle notamment que la matrice époxy bio-sourcée a été formulée sur la base d’un cahier des charges établi à partir des caractéristiques de la matrice associée au procédé de renforcement Foreva® TFC, ainsi que les critères ayant guidé le choix du tissu de renforcement unidirectionnel en fibres de lin. Une seconde partie du manuscrit présente l’ensemble des résultats expérimentaux obtenus dans le cadre de la campagne de durabilité sur le système de renforcement bio-sourcé. Cette campagne s’appuie sur un plan d’expériences optimisé par la matrice de Hoke. Des plaques de composite stratifié ainsi que des dallettes de béton renforcées par ce composite ont ainsi été soumis à des vieillissements accélérés en conditions hygrothermiques ainsi qu’à un vieillissement naturel. Dans une première étape, les résultats de différentes caractérisations physico-chimiques réalisées sur le composite bio-sourcé à différentes échéances de vieillissement, mettent en évidence l’importance respective et les effets parfois antagonistes des mécanismes d’évolution microstructurale et des phénomènes de dégradation dans les différentes conditions de vieillissement. Dans une seconde étape, les évolutions des principaux indicateurs des performances mécaniques du composite et de l’interface béton-composite dans les différents milieux de vieillissement sont présentées et interprétées à la lumière des caractérisations physico-chimiques précédentes. Dans une troisième étape, des éléments de comparaison sont apportés entre le système composite bio-sourcé et un système traditionnel à fibres de carbone. La dernière partie du manuscrit est consacrée à la mise en œuvre de la démarche fiabiliste à partir de la base de données expérimentale collectée précédemment pour le système bio-sourcé. Une analyse statistique par la méthode ANOVA (analyse de la variance) est d’abord réalisée sur l’ensemble des données expérimentales. Deux modèles de dégradation ont ensuite été élaborés en vue de décrire l’évolution des indicateurs de performance dans le temps pour toute condition de vieillissement hygrothermique : un modèle analytique incluant de manière explicite les effets quadratiques et le couplage entre la température et l’humidité relative, et un modèle physique basé sur la loi d’Eyring. L’étape suivante a ensuite consisté à utiliser ces modèles pour estimer des durées de vie du système de renforcement bio-sourcé dans les conditions de vieillissement accéléré. Des critères de fin de vie du système ont été définis à partir des recommandations de dimensionnement proposées notamment par les guides ACI et AFGC. En vue d’évaluer la durée de vie en condition de service, une procédure spécifique a ensuite été proposée pour appliquer le modèle analytique dans le cas du vieillissement naturel. Enfin, une probabilisation du modèle analytique est réalisée de manière à déterminer la probabilité de défaillance du système de renforcement bio-sourcé à tout instant de sa durée de vie In France, the built heritage of civil engineering and building structures is vast and ageing. Recent reports prepared by experts highlight this alarming situation and point out the need to significantly increase the resources allocated to the rehabilitation of this heritage. In this context, structural reinforcement by externally bonded composites has become an attractive solution for the rehabilitation of structures and the extension of their lifespan. This thesis, funded by the French Research Agency (ANR), aims to develop a new composite reinforcement system with a reduced environmental footprint, on one hand, and to build an original reliability approach to estimate the lifetime of reinforcement systems and their failure probability at any time, on the other hand. In this manuscript, the main phases of development of the bio-based system are first recalled. In particular, it is recalled that the formulation of the bio-sourced epoxy matrix was based upon the specifications and characteristics of the Foreva® TFC matrix, and the criteria that guided the choice of the unidirectional flax fibre reinforcement fabric are also presented. The second part of the manuscript presents all the experimental results obtained within the framework of the durability study on the bio-based strengthening system. This test campaign relies on a Design of Experiment optimized by Hoke’s matrix. Laminated composite plates and concrete slabs reinforced with these composites were subjected to accelerated ageing under hygrothermal conditions, and to natural ageing on an outdoor exposure site in Lyon as well, for a total duration of 24 months. In a first step, the results of various physico-chemical characterizations that were periodically conducted on the bio-based composites, highlighted the relative contributions of mechanisms involved in microstructural evolutions and degradation phenomena of both the polymer matrix and fiber/matrix interfaces. In a second step, the changes in the main performance indicators related to the composite and the concrete-composite interface subjected to the various ageing environments, are presented and interpreted in the light of the previous physico-chemical characterizations. In a third step, a comparison is made between the bio-based composite system and a traditional carbon fibre strengthening system. The last part of the manuscript is devoted to the implementation of the reliability approach, relying on the experimental database previously collected for the bio-based system. A statistical analysis by the ANOVA method is first carried out on all experimental data. Two degradation models were then developed to describe the evolutions of performance indicators over time for any hygrothermal ageing condition: an analytical model with explicit terms related to quadratic effects and coupling between temperature and relative humidity, and a physical model based on Eyring's law.In a next step, these models were used to estimate the lifetime of the bio-based strengthening system under accelerated ageing conditions. End-of-life criteria were first defined based on specifications proposed by different design guidelines, in particular by ACI and AFGC reports.In order to evaluate the lifetime under actual service conditions, a specific procedure was then proposed to apply the analytical model in the case of natural ageing. Finally, a probabilization of the analytical model is carried out in order to determine the probability of failure of the bio-based strengthening system at any time during its lifetime

Style APA, Harvard, Vancouver, ISO itp.

37

Gilani, Adel Mohamed. "Various Durability Aspects Of Slurry Infiltrated Fiber Concrete." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608753/index.pdf.

Pełny tekst źródła

Streszczenie:

Slurry infiltrated fiber concrete (SIFCON) was first produced in 1979 in the USA, by incorporating large amounts of steel fiber in molds to form very dense network of fibers. The network is then infiltrated by a fine liquid cement-based slurry or mortar. The steel fiber content can be as high as 30 % by volume. This percentage usually does not exceed 2 % in normal fiber reinforced concrete (FRC) for reasons related to mixing and workability. Due to its high fiber content, SIFCON demonstrates unique and superior mechanical properties in the areas of both strength and ductility. Most of previous research work on SIFCON has focused mainly on investigating the mechanical properties of this material. On the other hand, the studies carried out in the field of durability of SIFCON are quite limited. v Therefore, it seemed that it would be worth to study the various durability aspects of SIFCON. In view of the above, the objectives of this study are to investigate and provide information about durability of SIFCON, mainly permeability, resistance to chloride penetration, freezing and thawing and drying shrinkage. This information will help in providing the necessary database and knowledge about the ability of SIFCON to withstand the conditions for which it has been designed without deterioration, especially when it is intended to be used in aggressive environments The investigations included studying the effects of the following on durability of SIFCON: (i) matrix type (slurry or mortar), (ii) fiber contents (7%, 9.5%, and 12% by volume), and (iii) steel fiber geometry (hooked or crimped). The results obtained indicated that SIFCON, especially when prepared using mortar not slurry, has shown good durability characteristics in spite of its apparent high water absorption. The SIFCON made with the highest possible fiber volume fractions showed the best results. However, it was concluded that SIFCON needs to be protected with suitable low permeability overlays to ensure ideal improved performance by protecting the steel fibers exposed on the surfaces especially against chloride attack.

Style APA, Harvard, Vancouver, ISO itp.

38

Kodkani, Shilpa. "Interface durability of externally bonded GFRP to normal and high-performance concrete." Morgantown, W. Va. : [West Virginia University Libraries], 2004. https://etd.wvu.edu/etd/controller.jsp?moduleName=documentdata&jsp%5FetdId=3601.

Pełny tekst źródła

Streszczenie:

Thesis (M.S.)--West Virginia University, 2004. Title from document title page. Document formatted into pages; contains xiii, 147 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 141-147).

Style APA, Harvard, Vancouver, ISO itp.

39

Bouhet, Jean-Charles. "Étude de l'impact de l'humidité et de l'alcalinité sur des armatures de polymères renforcés de fibres (PRF)." Mémoire, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/8054.

Pełny tekst źródła

Streszczenie:

Résumé : La technologie des armatures en matériaux composites de polymères renforcés de fibre (PRF) reste relativement récente (moins de 20 ans) et souffre d’une moins bonne réputation en termes de durabilité, ce qui tend à freiner son acceptation par les professionnels du secteur. Les travaux présentés dans ce mémoire ont pour but d’étudier les effets de l’humidité et de l’alcalinité sur les performances mécaniques et thermomécaniques de barres d’armature en PRF. Si de nos jours l’évolution des propriétés des armatures de PRF a été largement étudiée par différents chercheurs, nous n’avons que peu d’informations sur les modes de dégradation qui entrainent ces pertes de performances. Le but des travaux entrepris dans ce mémoire est de trouver des pistes d’investigation pour la compréhension de ces mécanismes de dégradation qui pourraient éventuellement par la suite être reprises dans le cadre de travaux de thèse. Les travaux qui ont été entrepris s’articulent autour de deux projets. Le premier s’intéresse à l’étude du vieillissement accéléré de barres de polymère renforcé de fibres de verre (PRFV) de différents diamètres et soumis à un environnement humide. Le second s’intéresse à l’étude de barres de PRFV et de polymère renforcé de fibres de basalte (PRFB) de même diamètre soumis à un environnement alcalin qui simule le milieu interstitiel du béton. Abstract : The FRP rebars technology remains relatively recent and suffers from a bad reputation in terms of durability which slows its acceptation among the professionals of the construction field. The aim of the work presented in this essay is to study the effects of moisture and alkalinity on the mechanical and thermo mechanical performances of FRP rebars. Nowadays, the progressions of FRP performances have been widely studied by different researchers but we still have few knowledge about the modes of degradation which lead to performance losses. The final goal of this work is to find investigation trails for the understanding of those degradation mechanisms which could possibly be taken over as part of a thesis work. The work is divided into two projects. The first one is the study of accelerated aging of glass fibers reinforced polymer (GFRP) rebars, of different diameters, conditioned in a moist environment. The second one concerns the behavior of GFRP and basalt fibers reinforced polymer (BFRP) rebars, of same diameter, conditioned in an alkaline environment which simulates the interstitial solution of concrete.

Style APA, Harvard, Vancouver, ISO itp.

40

Conroy, Paul James. "Durability of glass and ceramic fibres within the lung." Thesis, Sheffield Hallam University, 1990. http://shura.shu.ac.uk/19497/.

Pełny tekst źródła

Streszczenie:

The durability in the lung of inorganic fibrous materials, such as asbestos and man-made mineral fibres, appears to be a major determinant of their pathogenic potential. However, studies have been inadequate in explaining differences in the physiological durability of such inorganic fibres. This study used an iterative approach to determine key factors affecting physiological durability of a soda-lime silicate bulk glass, A-glass, E-glass, Lead-glass, Cemfil and alumino-silicate ceramic fibres. The aims were to develop a) the current theoretical understanding of durability and b) a suitable in-vitro screening test for durability. Materials were exposed to simulations of the lung environment, which included a) exposure to Gamble's fluid, water, serum and other simulated fluids, b) long-term exposure to the intra-macrophage environment and c) exposure to rat lung. Durability was characterised by scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray microanalysis (EDXA). The use of secondary ion mass spectrometry (SIMS) was also explored, though further development was required in this area. Fibre behaviour depended on fibre composition and thenature of the exposure environment. The ceramic was durable in all environments, whilst A-glass, Lead-glass and the soda-lime silicate were prone to nucleophilic attack and leaching. The effects of in-vivo exposure were consistent with the response in-vitro. However, exposure to the intramacrophage environment in-vitro did not affect fibre durability and this surprising result should be investigated. Physiological durability was related to the ability of the fibre to resist nucleophilic attack and a hybridization bonding model was examined in order to explain the behaviour of some silicate glasses. It was recommended that models based on the molecular bonding were developed to encompass a wider range of materials. Occupational exposure and inhalation of asbestos fibre can cause lung disease and although the mechanisms of asbestos pathogenicity remain uncertain, attention has also focussed on the potential effects of other inorganic fibres. Comparative studies on behaviour of these materials in the lung have strongly implicated the durability and hence lifetime of the fibre to be a major determinant of the pathogenic potential. However, durability studies have generally been inadequate in explaining differences in physiological durability of inorganic fibres and hence provision of theoretical models. This study used a novel iterative approach to determine key factors affecting physiological durability of a range of glass and ceramic materials. The objective was to develop the theoretical understanding of the durability of inorganic fibrous materials in the lung and appraise in-vitro methods for determination of fibre durability to validate a suitable screening test. The durability of a range of glass and ceramic materials has been characterised using in-vitro and in-vivo simulations of the human lung environment; novel exposure systems have been developed and durability behaviour has been characterised by application of traditional analytical methods and by development and application of secondary ion mass spectrometry (SIMS) techniques. Appraisal of in-vitro simulations revealed that fibre behaviour depended upon fibre composition and exposure conditions' durability of the fibres in-vitro was related to model fluid pH. Fibre response in-vivo was rationalised by assuming localised pH variation. This work supports the use of a range of in-vitro exposure conditions to identify key determinants of fibre durability and to characterise chemical behaviour, and is critical of the use of single in-vitro screening tests which will reflect fibre behaviour under specific conditions. Resistance of the inorganic fibre network to hydrolytic attack was suggested as a key determinant of durability and a theoretical model was developed to predict this.

Style APA, Harvard, Vancouver, ISO itp.

41

Huang, Xinyu. "Mechanics and Durability of Fiber Reinforced Porous Ceramic Composites." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26063.

Pełny tekst źródła

Streszczenie:

Porous ceramics and porous ceramic composites are emerging functional materials that have found numerous industrial applications, especially in energy conversion processes. They are characterized by random microstructure and high porosity. Examples are ceramic candle filters used in coal-fired power plants, gas-fired infrared burners, anode and cathode materials of solid oxide fuel cells, etc. In this research, both experimental and theoretical work have been conducted to characterize and to model the mechanical behavior and durability of this novel class of functional material. Extensive experiments were performed on a hot gas candle filter material provided by the McDermott Technologies Inc (MTI). Models at micro-/meso-/macro- geometric scales were established to model the porous ceramic material and fiber reinforced porous ceramic material. The effective mechanical properties are of great technical interest in many applications. Based on the average field formalism, a computational micromechanics approach was developed to estimate the effective elastic properties of a highly porous material with random microstructure. A meso-level analytical model based on the energy principles was developed to estimate the global elastic properties of the MTI filament-wound ceramic composite tube. To deal with complex geometry, a finite element scheme was developed for porous material with strong fiber reinforcements. Some of the model-predicted elastic properties were compared with experimental values. The long-term performance of ceramic composite hot gas candle filter materials was discussed. Built upon the stress analysis models, a coupled damage mechanics and finite element approach was presented to assess the durability and to predict the service life of the porous ceramic composite candle filter material. Ph. D.

Style APA, Harvard, Vancouver, ISO itp.

42

Avena-Barthelemy, Anne. "Comportement a long terme de materiaux composites immerges a grande profondeur." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0049.

Pełny tekst źródła

Streszczenie:

Etude du vieillissement de polymeres renforces ou non de fibres de verre ou de mousses syntactiques immerges dans l'eau sous des pressions de 0 a 300 bars. Adsorption d'eau, proprietes mecaniques, eclatement des microspheres dans les mesures syntactiques

Style APA, Harvard, Vancouver, ISO itp.

43

Albrektsson, Joakim. "Durability of fire exposed concrete : Experimental Studies Focusing on Stiffness & Transport Properties." Licentiate thesis, KTH, Betongbyggnad, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168386.

Pełny tekst źródła

Streszczenie:

Road and rail tunnels are important parts of the modern infrastructure. High strength concrete (HSC) is commonly used for tunnels and other civil engineering structures, since it allows high load carrying capacity and long service life. In general, Swedish road and rail tunnels should be designed for a service life of 120 years. However, HSC has shown to be sensitive to severe fires in the moist tunnel environment, i.e., fire spalling may occur. Extensive research shows that addition of polypropylene (PP) fibres in the fresh concrete mix significantly reduces the risk of fire spalling. The durability of a concrete structure is mainly governed by the transport properties. Further, experimental studies aimed at understanding the protective mechanism of PP fibres indicate that fluid transport increases in connection with the melting temperature of such fibres. This might reduce the durability of fire exposed concrete with addition of PP fibres. This study aims to investigate whether the use of PP fibres has any significant effect on the durability of moderate fire exposed concrete structures. The experimental study focused on transport properties related to durability and stiffness reduction of fire exposed civil engineering concrete with and without addition of PP fibres. The study consists of three parts; (i) unilateral fire exposure in accordance with the standard time-temperature curve (Std) and a slow heating curve (SH), (ii) uniformly heating of non-restrained samples to 250oC, and (iii) moderate unilateral fire exposure, 350oC, of restrained samples. Changes in material properties caused by the fire exposure were studied by means of ultrasonic pulse velocity, full field-strain measurements during uniaxial compression core tests, polarization and fluorescence microscopy (PFM), water absorption and non-steady state chloride migration. The study shows that fire exposure influences different properties of importance for load carrying capacity and durability. To get a clear image of the fire damage one has to combine different test methods during damage assessments. Transport properties of concrete both with and without addition of PP fibres were considerably affected even at moderate fire exposure. Hence, the service life might be reduced. All series with addition of PP fibres exhibited higher water absorption compared to the series without PP fibres. The practical importance of this might, however, be small since also the water absorption of concrete without PP fibres was considerably affected for the fire scenarios considered in this study. Behind the fire exposed surface, i.e., between 30 and 60 mm, no change in water absorption was observed for concrete without PP fibres. However, higher water absorption of the series with addition of PP fibres was observed. Indicative fire tests aimed to evaluate the resistance to fire spalling during a subsequent severe fire was also conducted. The concretes with addition of PP fibres showed no signs of fire spalling, while progressive spalling was observed for the concrete without PP fibres. QC 20150603

Style APA, Harvard, Vancouver, ISO itp.

44

Rolland, Arnaud. "Comportement mécanique et durabilité de structures en béton renforcées par des armatures composites internes." Thesis, Paris Est, 2015. http://www.theses.fr/2015PEST1065/document.

Pełny tekst źródła

Streszczenie:

La corrosion des armatures constitue la principale cause de dégradation des ouvrages en béton armé, et occasionne des coûts élevés de maintenance/réparation. Pour prévenir ce problème sur ouvrages neufs, une solution consiste à renforcer les structures en béton par des armatures non-métalliques de type Polymère Renforcé de Fibres (PRF), généralement à base de fibres de verre, de carbone ou d'aramide. Il existe aujourd'hui plusieurs textes réglementaires consacrés aux armatures PRF, notamment aux USA, au Canada et au Japon, et de nombreux ouvrages en béton armé par barres en PRF ont d'ailleurs été construits dans ces pays. Cependant, si l'utilisation de ces nouvelles armatures semble à priori prometteuse, elle suscite encore des réserves de la part des maîtres d'ouvrages, notamment en France. Il subsiste en effet des incertitudes sur le comportement à long terme des structures renforcées par PRF, et plus particulièrement sur la durabilité en milieu alcalin des armatures à matrice vinylester ou époxy renforcée par des fibres de verre (PRFV), qui sont actuellement les plus utilisées, ou encore sur le vieillissement de l'interface PRF/béton. Dans ce contexte, la présente étude vise à développer pour la première fois en France, un ensemble de méthodologies permettant, d'une part, de caractériser les principales propriétés physiques, mécaniques et d'interface des différentes armatures en PRF disponibles sur le marché, mais également d'évaluer la durabilité d'armatures en PRFV (les plus représentatives du marché) et de l'interface PRFV/béton à travers des procédures pertinentes de vieillissements accélérés. La première partie de l'étude a donc été consacrée à la caractérisation physique et mécanique d'une sélection d'armatures du commerce, confectionnées à base de fibres de verre, de carbone ou d'aramide, et au comportement mécanique de l'interface entre ces PRF et le béton. Outre la caractérisation microstructurale des PRF par techniques de microscopie et d'analyse thermique, la mise en place de dispositifs d'essais de traction et de flexion 3 points à appuis rapprochés (Short-beam test) a permis d'accéder respectivement aux propriétés mécaniques en traction (module d'élasticité, résistance) et à la résistance au cisaillement inter-laminaire des armatures. Des essais spécifiques d'arrachement (Pull-out) ont ensuite permis d'évaluer l'influence de différents paramètres (type de fibre, diamètre et géométrie de surface des barres) sur le mécanisme de transfert d'effort à l'interface armature/béton. Une grande originalité de l'approche proposée réside dans l'instrumentation d'une partie des corps d'épreuve par des capteurs de déformation à fibre optique disposés au niveau de l'interface armature/béton ; ce dispositif de mesures réparties permet d'accéder à des informations locales comme le profil des déformations de traction de l'armature, et d'en déduire la longueur d'ancrage des différentes armatures dans le béton. En complément de l'étude expérimentale précédente, un travail de modélisation analytique et numérique a été initié en vue de simuler les essais d'arrachement et d'appréhender plus finement les mécanismes d'interface mis en jeu entre l'armature et le béton lors de ces essais. Dans cette optique, un modèle analytique d'interface a tout d'abord été proposé, puis introduit dans un modèle aux éléments finis (modèle d'endommagement de zones cohésives). Enfin, un protocole de vieillissement accéléré a été appliqué à des barres en PRFV seules ou noyées dans un milieu cimentaire. Les caractéristiques résiduelles des armatures et des interfaces ont été évaluées à différentes échéances de vieillissement (jusqu'à 240 jours). Hormis une diminution des propriétés mécaniques des barres soumises à une immersion directe en solution alcaline, cette condition pouvant être considérée comme très sévère par rapport aux conditions de service, il n'a pas été observé de dégradation des propriétés d'adhérence PRF/béton par rapport à l'état initial Corrosion of the steel reinforcing bars (rebars) is the main process involved in the degradation of reinforced concrete (RC) structures, and has large repercussions on the maintenance/reparation expenses. To prevent such degradations on new infrastructures, the use of corrosion-free reinforcements, such as Fiber Reinforced Polymer (FRP) bars based on glass, carbon or aramid fibers, is gaining interest. Specific guidelines are already available in several countries (USA, Canada or Japan for instance), that define the design principles and good practices for this type of internal rebars; beside, many FRP RC structures have been built and are in service in these countries. Although the development of these new reinforcing bars is quite promising, infrastructures owners are still reluctant for their wide-scale use, especially in France. There are still major concerns regarding the long term behavior of FRP RC structures, and more particularly, the durability of glass fibers reinforced polymers (GFRP) when subjected to an alkaline environment, and the ageing behavior of the GFRP/concrete bonding as well. In this context, the present study aims at developing for the first time in France, a set of methodologies that allows : to characterize the main physical/mechanical properties of different types of FRP bars from the marketto assess the durability of GFRP bars (the most common type of bar) and their interface with concrete through relevant accelerated ageing procedures. The first part of this study was thus devoted to the physical/mechanical characterization of a selection of commercially available FRP rebars, based on glass, carbon or aramid fibers, and to the mechanical behavior of corresponding FRP/concrete interfaces. Beside the microstructural characterization of the various FRP materials by microscopy and thermal analysis techniques, tensile and short beam tests were developed in order to determine the tensile properties (Young's modulus and strength) and the interlaminar shear strength (ILSS) of the bars. Specific pull-out tests then made it possible to evaluate the influence of several parameters (type of fibers, diameter and surface geometry of the bars) on the mechanism of load transfer at the bar/concrete interface. A main originality of the proposed approach relied on the instrumentation of several test bodies by optical fiber strain sensors, which were installed along the bar/concrete interface. Such a distributed measurement system provided local information in the form of tensile strain profiles of the bars along the interface, and made it possible to determine the effective transfer length of the various types of FRP bars. As a complement to the previous experimental study, an analytical and numerical modeling work was initiated to simulate the pull-out tests and investigate more closely the interfacial mechanisms involved in the FRP bar/concrete bond behavior. In this line, an improved interface model was first proposed, which was then implemented in a finite element model (cohesive zone model formulated in the context of damage mechanics).Finally, an accelerated ageing protocol was developed and applied to the GFRP bars, either alone or embedded in a concrete medium. The retention properties of both bars and interfaces were determined after various periods of exposure (up to 240 days). Except a drop of tensile properties observed for GFRP bars that were directly immersed in an alkaline solution, which is considered as a very severe environment compared to actual service conditions, no significant loss of interfacial properties was detected on aged specimens compared to the initial state

Style APA, Harvard, Vancouver, ISO itp.

45

Akhtarkhavari, Afsaneh. "Adhesion and durability of latex paint on wood fiber reinforced polyethylene." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0015/MQ53339.pdf.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

46

Darmawangsa, Darmadi. "Optical fiber sensors embedded in concrete structures : feasibility and durability studies." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40154.

Pełny tekst źródła

Streszczenie:

Thesis (Civ. E.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1996. Includes bibliographical references (leaves 292-295). by Darmadi Darmawangsa. Civ.E.

Style APA, Harvard, Vancouver, ISO itp.

47

Deng, Jiangang. "Durability of carbon fiber reinforced polymer (CFRP) repair/strengthening concrete beams." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663060011&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

48

Haskell, Adam Benjamin. "A Durability and Utility Analysis of EFPI Fiber Optic Strain Sensors Embedded in Composite Materials for Structural Health Monitoring." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/HaskellAB2006.pdf.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

49

Rabii, Hajer. "Étude du vieillissement de composites renforcés par des fibres naturelles : application bâtiment." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1147/document.

Pełny tekst źródła

Streszczenie:

L'utilisation des composites biosourcés dans des applications extérieures pour le génie civil pose le problème de leur durabilité dans les conditions d'utilisation, en raison de la forte hydrophilie des fibres naturelles. En effet, le comportement de ces composites en présence d’eau et d’humidité ou face aux contraintes thermiques et agressions biologiques est mal connu. L’objectif de cette thèse est d’étudier, par des analyses multi-échelles, la réversibilité des évolutions des propriétés de composites à matrice polyéthylène renforcée par des fibres courtes de lin. Pour ce faire, des cycles humidification/séchage ont été réalisés lors de vieillissement hydro et hygrothermiques, à 30 et 80°C. L’influence du taux de fibres et de la qualité de l'interface sur l’évolution de ces propriétés a été évaluée. De même, une étude de l’impact du développement microbien sur les composites a été réalisée pendant 6 mois. Après une caractérisation initiale des matériaux, les évolutions des caractéristiques cinétiques de coefficients de diffusion et de prise de masse au cours des vieillissements ont été évaluées. Ainsi, deux phénomènes antagonistes semblent gouverner l'évolution du coefficient de diffusion des composites. Dans un second temps, la caractérisation mécanique de ces composites au cours du vieillissement a permis d'identifier les phénomènes mis en jeu. Les évolutions du module mécanique à 30°C sont réversibles après séchage et sont attribuées à une plastification des microfibrilles de cellulose. Ces chutes s'accentuent et deviennent irréversibles à 80°C, mettant en évidence des dégradations plus importantes des matériaux. Dans un troisième temps, le phénomène de dégradation biologique de ces matériaux a été étudié. Il a été vérifié que les microorganismes sont responsables de consommation sélective de composants de fibres de lin et que leur croissance est favorisée par le taux de fibres dans le composite The use of bio-based composites in outdoor applications for civil engineering raises the issue of their sustainability in service. This is mainly due to the highly hydrophilic character of natural fibers. Indeed, the behavior of these composites in a wet environment or under thermal and biological constraints is not well known. The main objective of this study is to get a better understanding of the reversibility of bio-based composites properties. Therefore, wetting/ drying cycles were performed on polyethylene/short flax fibre composites under hydro and hygrothermal ageing at 30 and 80°C. The influence of the fiber content and the interface quality on the mechanical properties was monitored. Moreover, a 6 months study of a microbial growth impact on these composites was carried out. A characterization of the non-aged materials was conducted first. Then, the kinetic parameters such as the water diffusion coefficient and the weight changes due to ageing were determined. Two competing mechanisms seem to affect the diffusion coefficient. The mechanical characterization of these composites during aging has enabled the identification of the aging mechanisms. Changes in the mechanical modulus at 30°C were mostly reversible after a drying cycle and were associated with a plasticizing effect of the water molecules on the cellulose microfibrils. The property losses increase and become irreversible at 80°C, which indicates a higher degradation of the composites. Finally, the biological degradation of these materials has been studied. It was verified that selective consumption of flax fiber components by microorganisms occurs, and that their growth is favored by the fiber content in the composite

Style APA, Harvard, Vancouver, ISO itp.

50

Jackson, Nicole Danielle. "Reliability-based durability assessment of GFRP bars for reinforced concrete." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/35825.

Pełny tekst źródła

Streszczenie:

The American Concrete Institute (ACI) has developed guidelines for the design of fiber reinforced polymer (FRP) reinforced concrete structures. Current guidelines require the application of environmental and flexural strength reduction factors, which have minimal experimental validation. Our goal in this research is the development of a Monte Carlo simulation to assess the durability of glass fiber reinforced polymer (GFRP) reinforced concrete designed for flexure. The results of this simulation can be used to determine appropriate flexural strength reduction factors. Prior to conducting the simulation, long-term GFRP tensile strength values needed to be ascertained. Existing FRP tensile strength models are limited to short-term predictions. This study successfully developed a power law based-FRP tensile strength retention model using currently available tensile strength data for GFRP exposed to variable temperatures and relative humidity. GFRP tensile strength retention results are projected at 0, 1, 3, 10, 30, and 60-year intervals. The Monte Carlo simulation technique is then used to assess the influence beam geometry, concrete strength, fractions of balanced reinforcement ratio, reinforcing bar tensile strength, and environmental reduction factors on the flexural capacity of GFRP reinforced concrete beams. Reliability analysis was successfully used to determine an environmental reduction factor of 0.5 for concrete exposed to earth and weather. For simulations with higher GFRP bar tensile strength as well as larger beam geometry and fractions of the balanced reinforcement ratio, larger moment capacities were produced. A strength reduction factor of approximately 0.8 is calculated for all fractions of balanced reinforcement ratio. The inclusion of more long-term moisture data for GFRP is necessary to develop a more cohesive tensile strength retention model. It is also recommended that longer life cycles of the GFRP reinforced concrete beams be simulated. This research was conducted thanks to support from the National Science Foundation Division of Graduate Educationâ s Interdisciplinary Graduate Education Research and Traineeship (Award # DGE-0114342) Note: The opinions expressed herein are the views of the authors and should not be interpreted as the views of the National Science Foundation. Master of Science

Style APA, Harvard, Vancouver, ISO itp.

Rozprawy doktorskie na temat „Fibre durability”

Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych