Дисертації з теми "Fiber Reinforced Ceramics (FRC)"
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1
Vazquez, Calnacasco Daniel. "All-Oxide Ceramic Matrix Composites : Thermal Stability during Tribological Interactions with Superalloys." Thesis, Luleå tekniska universitet, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-85513.
Анотація:
The challenges faced in today’s industry require materials capable of working in chemically aggressive environments at elevated temperature, which has fueled the development of oxidation resistant materials. All-Oxide Ceramic Matrix Composites (OCMC) are a promising material family due to their inherent chemical stability, moderate mechanical properties, and low weight. However, limited information exists regarding their behavior when in contact with other high-temperature materials such as superalloys. In this work three sets of tribological tests were performed: two at room temperature and one at elevated temperature (650 °C). The tests were performed in a pin-on-disk configuration testing Inconel 718 (IN-718) pins against disks made with an aluminosilicate geopolymeric matrix composite reinforced with alumina fibers (N610/GP). Two different loads were tested (85 and 425 kPa) to characterize the damage on both materials. Results showed that the pins experienced ~ 100 % wear increase when high temperature was involved, while their microstructure was not noticeably affected near the contact surface. After high temperature testing the OCMC exhibited mass losses two orders of magnitude higher than the pins and a sintering effect under its wear track, that led to brittle behavior. The debris generated consists of alumina and suggests a possible crystallization of the originally amorphous matrix which may destabilize the system. The data suggests that while the composite’s matrix is stable, wear will not develop uncontrollably. However, as soon as a critical load/temperature combination is attained the matrix is the first component to fail exposing the reinforcement to damage which drastically deteriorates the integrity of the component.
2
Verma, Ravi Kant. "A study of the damage accumulation process in poly(aryl ether ketone ketone) and it's [sic] AS4 carbon fiber reinforced composites /." This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-06112009-063316/.
3
Mingazzini, Claudio <1970>. "Fiber-reinforced ceramics for thermostructural applications, produced by polymer impregnation pyrolysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6349/.
Анотація:
Several CFCC (Continuous Fiber Composite Ceramics) production processes were tested, concluding that PIP (Polymer Impregnation, or Infiltration, Pyrolysis) and CBC (Chemically Bonded Ceramics) based procedures have interesting potential applications in the construction and transportation fields, thanks to low costs to get potentially useful thermomechanical performances.
Among the different processes considered during the Doctorate (from the synthesis of new preceramic polymers, to the PIP production of SiC / SiC composites) the more promising results came from the PIP process with poly-siloxanes on basalt fabrics preforms. Low processing time and costs, together with fairly good thermomechanical properties were demonstrated, even after only one or two PIP steps in nitrogen flow. In alternative, pyrolysis in vacuum was also tested, a procedure still not discussed in literature, but which could originate an interesting reduction of production costs, with only a moderate detrimental effect on the mechanical properties. The resulting CFCC is a basalt / SiCO composite that can be applied for continuous operation up to 600°C, also in oxidant environment, as TG and XRD demonstrated. The failure upon loading is generally pseudo-plastic, being interlaminar delamination the most probable rupture mechanism. . The strength depends on several different factors (microstructure, polymer curing and subsequent ceramic phase evolution, fiber pull-out, fiber strength, fiber percentage) and can only be optimized empirically.
In order to be open minded in selecting the best technology, also CBC (Chemically Bonded Ceramics) matrixes were considered during this Doctorate, making some preliminary investigations on fire-resistant phosphate cements. Our results on a commercial product evidenced some interesting thermomechanical capabilities, even after thermal treatments. However the experiments showed also phase change and possible cracking and deformations even on slow drying (at 130°C) and easy rehydration upon exposure to environmental humidity.
4
Yang, Kwan-Ho. "Development of impact testing procedure at elevated temperature /." Thesis, Connect to this title online; UW restricted, 1988. http://hdl.handle.net/1773/7038.
5
Ishtewi, Ahmad M. "Shear Capacity of Fiber-Reinforced Concrete Under Pure Shear." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1354725447.
6
Lam, Su Ki. "Design of tough, metal fibre reinforced ceramics for use at high temperatures." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708380.
7
Huang, Xinyu. "Mechanics and Durability of Fiber Reinforced Porous Ceramic Composites." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26063.
Анотація:
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.
8
Oh, Donghoon. "Vibration control and design of composite cantilevers taking into account structural uncertainties and damage." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-07282008-142024/.
9
Hasala, Robert. "Model dentálního můstku vyztuženého vláknovým kompozitem." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-217044.
Анотація:
The diploma thesis aimed to changes of mechanical properties in the influence the use of geometry reinforcement, time delay between cure and measurement. Mechanical properties of model dental bridge observed effect of hydrothermal stress. Dental bridges were reinforced two types of Fiber Reinforced Composites. The first reinforcement had straight unidirectional orientation. The second reinforcement had multidirectional orientation. Mechanical testing was realized in the dependence at the force to deformation model of the dental bridge. Conversion was counted pursuant photo DSC measurement. The character of break was observed at SEM pictures and macro photos. Type of material and reinforcement fibers and their combination had important role at the mechanical properties.
10
Shin, Hyunho. "Interface reactions and their influence on properties of SiC fiber-reinforced ceramic matrix composites." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/19122.
11
Mansour, Marwan. "Experimental tests on the effect of temperature on the short term behavior of FRC beams." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Анотація:
The effect of temperature under short term behavior on macro-synthetic polypropylene fibers reinforced concrete (MSFRC) was evaluated, to understand how this condition may affect the performance of this material. An experimental campaign of three-point bending, compressive tests and elastic modulus tests have been performed on prisms, cubes and cylinders cured at 6 temperatures, ranging from -30°C to +60°C. The results highlighted that, for the material tested, the increment of temperature causes a decrement of the peak and post-peak flexural strength. Further analysis have been done on the fibers number and failure type.
12
Depalma, Carlos Mariano A. "The role of the thermal contact conductance in the interpretation of laser flash data in fiber-reinforced composites." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10062009-020306/.
13
Fiadzo, Odile. "Evaluation of the densification behavior of chemically vapor infiltrated composites in correlation with their preform architecture." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19990.
14
Cox, Sarah. "Processing and Characterization of Continuous Basalt Fiber Reinforced Ceramic Matrix Composites Using Polymer Derived Ceramics." Master's thesis, University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6259.
Анотація:
The need for high performance vehicles in the aerospace industry requires materials which can withstand high loads and high temperatures. New developments in launch pads and infrastructure must also be made to handle this intense environment with lightweight, reusable, structural materials. By using more functional materials, better performance can be seen in the launch environment, and launch vehicle designs which have not been previously used can be considered. The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer matrix composites can be used for temperatures up to 260°C. Ceramics can take much higher temperatures, but they are difficult to produce and form in bulk volumes. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, allowing a shape to be formed and cured and then to be pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in the composites. In this study, continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material. The oxyacetylene torch testing and three point bend testing have been performed on test panels and the test results are presented.M.S.M.S.E.
Masters
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering
15
Texier, Anne. "The fabrication of carbon-fiber composites by aqueous suspension prepregging with larc-tpi and peek." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03172010-020638/.
16
Bhatt, Hemanshu D. "Effect of interfacial thermal conductance and fiber orientation on the thermal diffusivity/conductivity of unidirectional fiber-reinforced ceramic matrix composites." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07282008-135034/.
17
Rossi, Luca. "Caratterizzazione meccanica di calcestruzzi fibrorinforzati con fibre d'acciaio." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amslaurea.unibo.it/107/.
Анотація:
L’utilizzo di materiali compositi come i calcestruzzi fibrorinforzati sta diventando sempre più frequente e diffuso. Tuttavia la scelta di nuovi materiali richiede una approfondita analisi delle loro caratteristiche e dei loro comportamenti. I vantaggi forniti dall’aggiunta di fibre d’acciaio ad un materiale fragile, quale il calcestruzzo, sono legati al miglioramento della duttilità e all'aumento di assorbimento di energia. L’aggiunta di fibre permette quindi di migliorare il comportamento strutturale del composito, dando vita ad un nuovo materiale capace di lavorare non solo a compressione ma anche in piccola parte a trazione, ma soprattutto caratterizzato da una discreta duttilità ed una buona capacità plastica. Questa tesi ha avuto come fine l’analisi delle caratteristiche di questi compositi cementizi fibrorinforzati. Partendo da prove sperimentali classiche quali prove di trazione e compressione, si è arrivati alla caratterizzazione di questi materiali avvalendosi di una campagna sperimentale basata sull’applicazione della norma UNI 11039/2003. L’obiettivo principale di questo lavoro consiste nell’analizzare e nel confrontare calcestruzzi rinforzati con fibre di due diverse lunghezze e in diversi dosaggi. Studiando questi calcestruzzi si è cercato di comprendere meglio questi materiali e trovare un riscontro pratico ai comportamenti descritti in teorie ormai diffuse e consolidate. La comparazione dei risultati dei test condotti ha permesso di mettere in luce differenze tra i materiali rinforzati con l’aggiunta di fibre corte rispetto a quelli con fibre lunghe, ma ha anche permesso di mostrare e sottolineare le analogie che caratterizzano questi materiali fibrorinforzati.
Sono stati affrontati inoltre gli aspetti legati alle fasi della costituzione di questi materiali sia da un punto di vista teorico sia da un punto di vista pratico.
Infine è stato sviluppato un modello analitico basato sulla definizione di specifici diagrammi tensione-deformazione; i risultati di questo modello sono quindi stati confrontati con i dati sperimentali ottenuti in laboratorio.
18
Gonzalez-Ibarra, Alvaro. "The effects of polymeric binders on the processability and properties of composites made by suspension prepregging." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09192009-040513/.
19
Guo, Zihong. "Experimental and numerical analysis of abrasive waterjet drilling of brittle materials /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/7092.
20
Verma, Ravi Kant. "A study of the damage accumulation process in poly(aryl ether ketone ketone) and its AS4 carbon fiber reinforced composites." Thesis, Virginia Tech, 1992. http://hdl.handle.net/10919/43146.
Анотація:
This thesis presents the results of a study done on the damage accumulation process in poly(ether ketone ketone) and its AS4 carbon fiber reinforced composites. The damage accumulation process was studied as a function of applied heat treatment. This study is the result of a project funded by duPont and was done in part to explain the dramatic change in fatigue properties observed at duPont as the applied heat treatment is changed.
The mechanical properties were characterized using a battery of tests. The quenched composite systems have lower moduli, but higher toughness and elongations. The quenched systems also have the best fatigue performance and therefore, it can be concluded that the quenched composite systems have the best potential as far as industrial applications are concerned. Quenching has other advantages in industrial applications. These include decreased chances of operator error, and decreased processing times.
The damage accumulation process was characterized using the acoustic emission method and also the drop in stiffness during flexure testing. It has been observed that the ultimate mechanical properties show a weak dependence on the applied heat treatment, whereas the damage accumulation process changes dramatically. A model has been developed to simulate the damage accumulation process. This model has then been used to predict the fatigue S-N curve in stroke control and to qualitatively relate it to the available fatigue data in stress control.Master of Science
21
Lee, Shin Steven. "Damage analysis and mechanical response of as-received and heat-treated Nicalon/CAS-II glass-ceramic matrix composites." Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10032007-171633/.
22
Incerti, Andrea. "Steel and macro-synthetic self-compacting fibre reinforced concrete, experimental study on the long-term deformations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3265/.
Анотація:
Experimental study on the long-term deformations of the fibre reinforced concrete.
Steel and macro-synthetic fibers were used to evaluate the shrinkage, creep, mid-span deflection, cracking and rupture analysis of three different types of samples.
At the end the main topics of ACI guidelines were analyzed in order to perform an overview of design.
23
Yang, Fan. "Oxidation and mechanical damage in unidirectional SiC/Si#N# composite at elevated temperatures." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/19057.
24
Scrivener, Sandra Lynn. "In-plane vibrations of a transversely isotropic arch." Thesis, Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/50090.
Анотація:
A model for the dynamic response of a laminated composite arch is developed from classical shell theory. The problem is reduced from a shell to an arch by making an assumption that the variation of the field of variables in the direction of the width of the arch is small compared to those in other directions. Standard separation of variables is used to change from a system of partial differential equations to that of ordinary differential equations. Several methods of solution are explored, namely the Laplace transformation, the method of particular solutions, and the eigensolution. The eigensolution is chosen as the the most efficient in terms of computer time and is the easiest to modify. The free vibration of the arch is explored and the natural frequencies of the system are determined. The response of the arch to general forcing functions is also considered, by the use of the Fourier transformation technique. Damping through material viscoelasticity and use of the model in evaluation of experimental data are also discussed.Master of Science
incomplete_metadata
25
Osorio, Gomez Laura Isabel. "Behavior of synthetic fiber-reinforced concrete circular columns under cyclic flexure and constant axial load." Mémoire, Université de Sherbrooke, 2008. http://savoirs.usherbrooke.ca/handle/11143/1435.
Анотація:
La ductilité et la capacité à dissiper de l'énergie sont deux qualités très importantes pour les éléments structuraux des structures situées dans les régions sismiques comme l'est du Canada. Soulignons que Montréal occupe la deuxieme place en ce qui a trait au risque sismique au Canada. De plus, la réduction des coûts de maintenance des infrastructures est un sujet d'intérêt pour les propriétaries alors que ces derniers doivent en tout temps garantir la sécurité des usagers. Or, le béton renforcé avec des fibres synthétiques semble être un matériau qui remplit ces caractéristiques. Pourtant, son utilisation est actuellement limitée aux éléments non structuraux ou structuraux mais non principaux. Afin de généraliser l'utilisation du béton fibre dans le domaine structural, il faut continuer à produire et à analyser des données expérimentales qui permettront de valider et d'améliorer les prescriptions de design et les modèles analytiques actuels pour la conception des éléments en béton armé avec des fibres dans les zones sismiques. Dans ce contexte, six poteaux circulaires à grande-échelle ont été testés sous une charge axiale constante (25% de Agf'c) et en flexion cyclique. Trois poteaux ont été confectionnés en béton normal (BN) et les trois autres en béton renforcé avec des fibres synthétiques (BRFS). La résistance à la compression du béton spécifiée à 28 jours pour les spécimens était de 30 MPa. Le volume de fibres synthétiques en polypropylène-polyéthylène utilisé a été de 1%. Les trois poteaux en BN étaient renforcés par une armature transversale constituée d'une spirale ayant un pas de 42, 75 et 100 mm respectivement. Ces trois spécimens ont été comparés avec des spécimens similaires en BRFS. Les résultats montrent que la présence des fibres synthétiques dans la matrice de béton améliore le comportement ductile et la capacité a dissiper de l'énergie des spécimens. Il a été observé que cette amélioration n'est pas directement proportionnelle à la quantité d'armature transversale. Toutefois, l'utilisation du béton fibre semble rendre possible une réduction de l'armature transversale tout en conservant un aussi bon sinon un meilleur comportement.
26
Pickering, Elliot. "Chemical vapor deposition of Ti₃SiC₂." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/19463.
27
Yang, Yaping. "Development of SiC whisker/chopped SiC fiber reinforced (Ca0.6,Mg0.4)Zr₄(PO₄)₆ ceramic matrix composites." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/38557.
Анотація:
SiC whisker reinforced (Ca0.6,Mg0.4)Zr₄(PO₄)₆ (CMZP) matrix composites containing 10, 20, and 30 vol % whiskers were produced using a glass encapsulated hot isostatic pressing (HIPing) technique. The best HIPing temperature, pressure, and time conditions to optimize composite density and strength were determined to be 1050°C, 103 MPa, and 0.25 h.Ph. D.
28
Tiwari, Anil. "The development of an interpretive methodology for the application of real-time acousto-ultrasonic NDE technique for monitoring damage in ceramic composites under dynamic loads." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/39527.
29
Pereiro, Barceló Javier. "INESTABILIDAD DE BARRAS COMPRIMIDAS DE ACERO Y DE SMA EN ELEMENTOS DE HORMIGÓN FABRICADOS CON NUEVOS MATERIALES. RECOMENDACIONES DE DISEÑO." Doctoral thesis, Universitat Politècnica de València, 2017. http://hdl.handle.net/10251/90650.
Анотація:
The strain capacity of structures depends on the plastic hinge behaviour. There are different proposals in the scientific literature in order to improve this behaviour in reinforced concrete structures such as the following ones: proposals include the use of fiber reinforced concrete, very high performance concrete or replacing in the critical structure zone, the steel reinforcement with shape memory alloy and superelasticity bars (from this point forward SMA), among other solutions.
However, the strain capacity of hinges is dependent on the compressed reinforcement buckling, which means a drastic diminishing in the bearing capacity and ductility. This phenomenon happens due to the cover spalling or degradation, or due to an insufficient transverse reinforcement arrangement.
The design codes propose requirements related to the diameter of longitudinal bars and to the transverse reinforcement separation to assure the bearing capacity or to assure the hinge rotation without the compressed reinforcements buckle. Nevertheless, the aforementioned requirements are not valid in compressed elements made of new materials (fiber reinforced concrete, very high performance concrete or SMA bars).
This doctoral thesis analyzes the compressed steel or NiTi - SMA bars behaviour in elements made of conventional, high strength or very high performance concrete, with or without fibres.
Therefore, an experimental research has been carried out to study the local instability of the compressed bars (steel and NITI) in concrete elements. 32 columns subject to a bending-compression load have been analyzed.
An analytic model has been proposed to analyze the buckling critical stress and length in the compressed bars in concrete elements. This model has been calibrated based on experimental tests.
It has been performed an experimental and numerical research to analyze the behaviour of the NITI bars as isolated bars. It has been proposed an analytic model to calculate the relationship stress-strain of the compressed bars that includes the buckling effect. This model has been verified by both experimental and numerical results.
Finally, it has been proposed an expression to calculate the maximum separation of the transverse reinforcement according to the required limited stress, for both steel and SMA bars. In order to define that stress, two criteria have been proposed: one of them is based on stresses and the other one on strains. With respect to the concrete without fibres case, the proposed expression has been compared with the current code.La capacidad de deformación de las estructuras depende del comportamiento de las rótulas plásticas. Para mejorar dicho comportamiento en estructuras de hormigón armado, en la literatura técnica se propone utilizar hormigón con fibras de acero en su masa, hormigón de muy altas prestaciones o sustituir en la zona crítica de la estructura las armaduras de acero por barras de aleación con memoria de forma y superelasticidad (en adelante SMA) entre otras soluciones. Sin embargo, la capacidad de deformación de las rótulas está condicionada por el pandeo de la armadura comprimida, lo que supone una disminución drástica de la capacidad resistente y de la ductilidad. Este fenómeno se produce porque el recubrimiento del hormigón salta o se degrada, o por una insuficiente disposición de armadura transversal. En las normativas de diseño se proponen requisitos acerca del diámetro y de la separación de la armadura transversal para asegurar la capacidad resistente o la deformación de la rótula sin que las armaduras comprimidas pandeen. Sin embargo, dichas expresiones no son válidas en elementos comprimidos fabricados con nuevos materiales (hormigón con fibras en su masa, hormigones de muy altas prestaciones o barras de SMA). En esta tesis doctoral se analiza el comportamiento de barras comprimidas, de acero o de SMA en base NiTi, en elementos fabricados con hormigones convencionales, de alta resistencia o de muy altas prestaciones, con o sin fibras en su masa. A tal efecto, se ha ejecutado un programa experimental para estudiar la inestabilidad local de las barras comprimidas (acero y NiTi) en elementos de hormigón. Se han analizado un total de 32 soportes sometidos a una solicitación de flexo-compresión. Se ha propuesto un modelo analítico para determinar la tensión y la longitud crítica de pandeo de barras comprimidas en elementos de hormigón. Este modelo ha sido calibrado con los ensayos experimentales. Se ha realizado un estudio experimental y numérico para analizar el comportamiento de las barras de NiTi como barras aisladas. Se ha propuesto un modelo analítico para calcular la relación tensión - deformación de barras comprimidas que incluye el efecto del pandeo. Este modelo ha sido verificado tanto con los resultados experimentales como numéricos. Finalmente, se ha propuesto una expresión para el cálculo de la separación máxima de la armadura transversal en función de la tensión límite requerida, tanto para barras de acero como de SMA. Para la definición de dicha tensión se proponen dos criterios: uno basado en tensiones y otro en deformaciones. En el caso de hormigón sin fibras, la expresión propuesta se ha comparado con la normativa actual.
La capacitat de deformació de les estructures depén del comportament de les ròtules plàstiques. Per a millorar dit comportament en estructures de formigó armat, en la literatura tècnica es proposa utilitzar formigó amb fibres d'acer en la seua massa, formigó de molt altes prestacions o substituir en la zona crítica de l'estructura les armadures d'acer per barres d'aliatge amb memòria de forma i superelasticitat (d'ara endavant SMA) entre d'altres solucions. No obstant això, la capacitat de deformació de les ròtules està condicionada pel vinclament de l'armadura comprimida, la qual cosa suposa una disminució dràstica de la capacitat resistent i de la ductilitat. Este fenomen es produeix perquè el recobriment del formigó salta o es degrada, o per una insuficient disposició de l'armadura transversal. En les normatives de disseny es proposen requisits quant al diàmetre i a la separació de l'armadura transversal per assegurar la capacitat resistent o la deformació de la ròtula sense que les armadures comprimides vinclen. No obstant això, estes expressions no son vàlides en elements comprimits fabricats amb nous materiales (formigó amb fibres en la seua massa, formigons de molt altes prestacions o barres de SMA). En esta tesis doctoral s'analitza el comportament de barres comprimides, d'acer o de SMA compost per NiTi, en elements fabricats amb formigons convencionals, d'alta resistència o de molt altes prestacions, amb o sense fibres en la seua massa. A tal efecte, s'ha executat un programa experimental per estudiar la inestabilitat local de les barres comprimides (acer i NiTi) en elements de formigó. S'han analitzat un total de 32 soports somesos a una solicitació de flexo-compressió. S'ha proposat un model analític per determinar la tensió i longitud crítica de vinclament de barres comprimides en elements de formigó. Este model ha sigut calibrat amb els assajos experimentals. S'ha realitzat un estudi experimental i numéric per analitzar el comportament de les barres de NiTi com barres aïllades. S'ha proposat un model analític per calcular la relació tensió-deformació de barres comprimides que inclou l'efecte del vinclament. Este model ha sigut verificat tant amb els resultats experimentals com numérics. Finalment, s'ha proposat una expressió per al càlcul de la separació màxima de l'armadura transversal en funció de la tensió límit requerida., tant per a barres d'acer com de SMA. Per a la definició de dita tensió es proposen dos criteris: uno basat en tensions i l'altre en deformacions. En el cas del formigó amb fibres, l'expressió proposada s'ha comparat amb la normativa actual.
Pereiro Barceló, J. (2017). INESTABILIDAD DE BARRAS COMPRIMIDAS DE ACERO Y DE SMA EN ELEMENTOS DE HORMIGÓN FABRICADOS CON NUEVOS MATERIALES. RECOMENDACIONES DE DISEÑO [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90650
TESIS
30
Ibarra, Jonatanh José. "Vliv složení mezivrstvy na pevnost adhezního spoje mezi vláknovým a částicovým kompozitem." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2010. http://www.nusl.cz/ntk/nusl-216635.
Анотація:
Hlavním cílem této práce je studium aktuálního problému adheze mezi kompozitními materiály, a určení vlivu složení mezivrstvy v pevnosti adhezivního spoje mezi vláknové (FRC) a částicové (PFC) kompozity, používané ve stomatologii. FRC tyčinky byly vytvořené na bázi komerční dimetakrylatové pryskyřice a skleněných S vláken. PFC byl vytvořen ze směsi pryskyřic (bis-GMA a PEGDMA), plněných drceným barnatým sklem. Celkově bylo připraveno a vyzkoušeno 84 vzorků. Vzorky byly rozdělené do pěti hlavních skupin. První skupina byla vytvořena ze série vzorků bez mezivrstvy. Zbylé čtyři skupiny byly rozděleny dle složení mezivrstvy (tloušťky a druhu pryskyřic). Částicové kompozity vzorků se lišily obsahem plniva (0, 10, 40 hm %). FRC tyčinky byly stejné pro všechny vzorky. Univerzální testovací přístroj ZWICK Z010 byl použit k zjištění smykové pevnosti adhezivního spoje všech vzorků. Rastrovací elektronový mikroskop byl použít k pozorování místa porušení. Ze získaných výsledků vyplívá, že s přidáváním mezivrstvy mezi vláknovým a částicovým narůstá smyková pevnost spoje. Důležitost těchto výsledků je způsobená tím, že v posledních letech použití těchto materiálů ve stomatologii narůstá a adheze zůstává jeden z hlavních problémů při klinické praxi.
31
Silva, Marcelo Gomes da. "Distribuição de tensões em próteses parciais fixas posteriores livres de metal com retentores intracoronários: análise em elementos finitos." Universidade do Estado do Rio de Janeiro, 2011. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=2764.
Анотація:
Fundação de Amparo à Pesquisa do Estado do Rio de JaneiroPara reabilitar a ausência de um elemento dentário posterior, as próteses parciais fixas (PPF) com retentores intracoronários são uma alternativa aos implantes osseointegrados. O objetivo deste estudo foi avaliar a distribuição de tensões nessas próteses com três combinações de materiais: cerâmica de zircônia parcialmente estabilizada por ítria (ZPEI) revestida por cerâmica de fluorapatita (α), cerâmica de dissilicato de lítio (β) ou compósito fibrorreforçado (γ). Na composição α, foram analisadas a presença ou ausência da cerâmica de revestimento na parede cervical das caixas proximais e três variações na área total da seção transversal dos conectores (4 mm de largura x 3,2, 4,2 ou 5,2 mm de altura). Em 8 modelos bidimensionais de elementos finitos, uma carga vertical de 500 N foi aplicada na fossa central do pôntico e as tensões principais máximas (tração) e mínimas (compressão) foram apontadas em MPa. Inicialmente foram avaliados os 6 modelos com PPF de ZPEI e suas variações. Os maiores valores das tensões de tração foram encontrados no terço cervical dos conectores. Quando presente nestas regiões, a cerâmica de revestimento recebeu tensões acima do limite de sua resistência à flexão. Na comparação entre os modelos sem cerâmica de revestimento na parede cervical das caixas proximais, mesmo aquele com conectores de 3,2 x 4 mm, cuja infraestrutura apresentava 2,5 x 3 mm, poderia ser recomendado para uso clínico. Altos valores de tensões de compressão foram registrados entre o terço oclusal e médio dos conectores, correspondente à união entre as cerâmicas, o que poderia ocasionar, devido à flexão, falhas adesivas. Posteriormente, o modelo de ZPEI com a cerâmica de fluorapatita ausente da parede cervical das caixas proximais e área total dos conectores de 4,2 x 4 mm foi comparado aos dois outros materiais com conectores de mesma área. Na PPF de dissilicato de lítio, os valores representaram uma provável violação do limite de sua resistência à flexão. A PPF de compósito fibrorreforçado apresentou tensões bem abaixo do limite de resistência à flexão de sua infraestrutura, mas, como no modelo de ZPEI, tensões compressivas se concentraram com alto valor entre o terço oclusal e médio dos conectores, local de união entre a resina composta e a infraestrutura de fibras. Os resultados mostraram que a cerâmica de dissilicato de lítio e a presença da cerâmica de fluorapatita na parede cervical das caixas proximais deveriam ser contraindicadas para a condição proposta. Parece viável uma área de conectores na infraestrutura de ZPEI com no mínimo 2,5 x 3 mm. A PPF de compósito fibrorreforçado apresenta resistência estrutural para a situação estudada, mas, como também aquelas compostas de ZPEI, aparenta ter como pontos fracos a adesão entre a infraestrutura e o material de cobertura e a própria resistência deste último.
Inlay-retained fixed partial dentures (IRFPD) are an alternative to osseointegrated implants to replace a single missing posterior tooth. The aim of this study was to evaluate the stress distribution within these prostheses with three material combinations: yttria-tetragonal zirconia polycrystal (Y-TZP) ceramic veneered with fluorapatite ceramic (α), lithium-disilicate ceramic (β) or fiber-reinforced composite (γ). In composition α, an analysis was conducted on the presence or absence of the veneering ceramic on the cervical wall of the proximal boxes and three variations in the total area of the connectors cross-section (4 mm in width x 3.2, 4.2 or 5.2 mm in height). In 8 two-dimensional finite element models, a vertical load of 500 N was applied on the central fossa of the pontic. Maximum (tension) and minimum (compression) principal stresses were then shown in MPa. First, the 6 models with Y-TZP fixed partial dentures (FPD) and their variations were evaluated. The highest values of tensile stresses were found at the cervical third of the connectors. When present in these regions, the veneering ceramic received stresses beyond its flexural strength limit. In the comparison among models without veneering ceramic on the cervical wall of the proximal boxes, even the model with connectors of 3.2 x 4 mm, whose framework presented 2.5 x 3 mm, could be recommended for clinical use. High values of compressive stresses were recorded between the middle and occlusal thirds of the connectors, corresponding to the juncture of the ceramics. Owing to flexure, these stresses might lead to adhesive failures. Then, the Y-TZP model without fluorapatite ceramic on the cervical wall of the proximal boxes and total connector area of 4.2 x 4 mm was compared to the other two materials with connectors of the same area. For the lithium-disilicate FPD, the observed values would probably exceed its flexural strength limit. The fiber-reinforced composite FPD presented stresses far below the flexural strength limit of its framework, but, as observed in the Y-TZP model, high values of compressive stresses were concentrated between the middle and occlusal thirds of the connectors, where the juncture of the composite and the fiber framework is located. The results showed that the use of lithium-disilicate ceramics and the presence of fluorapatite ceramics on the cervical wall of the proximal boxes should be contraindicated for the condition proposed. A minimum of 2.5 x 3 mm for the connector area of the Y-TZP framework seems viable. The fiber-reinforced composite FPD presented structural resistance for the situation studied but, as was also the case of the Y-TZP fixed partial dentures, its weak points seem to be the adhesion between the framework and the veneering material, as well as the resistance of the veneering material itself.
32
Gasser, Alain. "Sur la modélisation et l'identification du comportement mécanique des composites céramique-céramique à température ambiante." Cachan, Ecole normale supérieure, 1994. http://www.theses.fr/1994DENS0024.
Анотація:
Une approche générale de l'endommagement des matériaux composites céramique-céramique à fibres est présentée. Des outils de modélisation du comportement jusqu'a rupture, sous chargements complexes, ont été mis en place et appliques aux deux composites étudies (sic-sic tisse et sic-masl stratifié), en tenant compte de la différence de comportement entre traction et compression (due a l'état des fissures, ouvertes ou fermées). Des essais de traction-compression a température ambiante ont été réalises sur ces deux composites, pour différents empilements. Pour le sic-sic tisse, un premier macro-modèle isotrope a montre ses limites dans la description des réseaux de fissures et des chargements complexes. Ainsi, il a été développé un modèle a endommagement anisotrope, qui inclue deux mécanismes de fissuration: le premier prend en compte les fissures perpendiculaires a la direction principale de chargement, le second les fissures perpendiculaires a la direction des fibres. La difficulté de ce modèle se situe dans son identification: les essais uni-axiaux ne sont pas suffisants. Une méthodologie d'identification, comportant un essai biaxial, a été mise en place. Cette loi de comportement a été incluse dans un logiciel permettant de simuler le comportement du matériau sous chargements complexes (comme par exemple un essai de pression interne sur tube), et d'en déterminer les valeurs a rupture. La comparaison avec des essais biaxiaux, réalises au LCTS bordeaux, a permis de vérifier le modèle qualitativement. Le sic-masl se présentant sous forme d'un stratifié, c'est la monocouche qui a été modélisée. Ce méso-modèle comprend trois variables scalaires d'endommagement. Une homogénéisation classique de type stratifie permet de retrouver le comportement global de tous les types d'empilements. L'identification et la vérification du modèle ont été effectuées à l'aide de plusieurs de ces empilements
33
Deü, Jean-François. "Rupture des composites stratifiés sous chargement dynamique : apport des méso-modèles avec endommagement retardé." Cachan, Ecole normale supérieure, 1997. http://www.theses.fr/1997DENS0012.
Анотація:
Cette étude est consacrée a la prévision de l'endommagement et de la rupture de composites stratifies. Pour cela, des méso-modèles de comportement, dans lesquels le stratifie est décrit comme un empilement de couches et d'interfaces interlaminaires, sont utilises en statique. Les effets de l'endommagement sont pris en compte par l'intermédiaire de variables internes supposées uniformes dans l'épaisseur des couches. Une extension de ces modèles aux cas de sollicitations dynamiques est proposée. Elle est basée sur l'utilisation de lois d'endommagement dépendantes du temps, lois appelées retardées. Ces lois introduisent la notion de vitesse maximale d'endommagement. Physiquement, elles sont fondées sur l'idée que la vitesse de propagation des microfissures est finie. Par rapport au cas de sollicitations statiques, le principal paramètre supplémentaire est la vitesse maximale d'endommagement, qui, combinée a la vitesse de propagation des ondes du milieu endommage, introduit une longueur caractéristique dans la modélisation. Les apports de ces modèles vis-à-vis des questions d'unicité, de localisation et de stabilité sont étudiés sur la base de travaux analogues en viscoplasticité. Concernant les problèmes de dépendance au maillage, le modèle développé présente l'intérêt de pouvoir estimer, a priori, la taille des éléments à utiliser. Une discussion sur l'identification des paramètres du modèle est également proposée. Elle est principalement basée sur l'analyse de simulations unidimensionnelles d'essais d'impact plaque-plaque. L'implantation des méso-modèles d'endommagement dans le code de calcul éléments finis de dynamique dyna3d permet de confirmer les apports dus a l'effet retard et de valider l'approche sur des simulations d'essais aux barres d'Hopkinson (essais de compression et flexion dynamique sur composite sic/sic) ainsi que sur un exemple d'impact sur plaque stratifiée sic/mas-l.
34
Gudapati, Vamshi Mohan. "Processing and characterization of continuous fiber ceramic nanocomposites by preceramic polymer pyrolysis." Thesis, 2005. http://hdl.handle.net/10125/20690.
35
Al-Qenaei, Nouri 1975. "Nano ceramic fiber reinforced silicone maxillofacial prosthesis." Thesis, 2010. http://hdl.handle.net/1805/2223.
Анотація:
Indiana University-Purdue University Indianapolis (IUPUI)The purpose of this study was to investigate the effect of nano ceramic fiber fillers on the physical properties of VST-50HD silicone maxillofacial prosthesis. Nano alumina fibers at 2 percent, 4-percent, and 6-percent wt were mixed into the VST-50HD silicone elastomer (Factor II Inc., Lakeside, AZ), a commercially-available poly(dimethylsiloxanes). Ten dumb-bell-shaped specimens were used to determine the tensile strength according to ISO 37:2005 and elongation at fracture. Ten trouser-shaped test pieces were used to determine the tear resistance according to ISO 34-1:2004. Shore A test method was used to measure the hardness of the material. The data collected from all quantitative studies of the modified silicones were analyzed using one-way ANOVA with concentration of nano ceramic fiber as the main variable. Specimens from VST- 50HD were also made and tested as control. Results: The mean values for tensile strength (MPa) of control group, 2-percent, 4-percent, and 6-percent reinforced nano ceramic fiber fillers were from 3.43 ± 0.12 to 5.48 ± 0.71. Tear strength (MPa) were from 2.34 ± 0.37 to 5.01 ± 0.39. Elongations at fracture were from 699.66 ± 43.69 to 793.51 ± 57.27. Shore A hardness were from 25.76 ± 2.18 to 38.76 ± 1.83. Conclusion: There was a significant difference (p < 0.001) in the mean tensile, tear and Shore A hardness strengths between the control group and 2-percent, 4-percent, and 6-percent percent reinforced nano ceramic fiber fillers; however, there was not a significant difference (p > 0.05) between 2-percent, 4-percent, and 6-percent reinforced nano ceramic fiber fillers. There was a significant difference (p < 0.001) in the mean elongation at fracture between the 2-percent and control group, 4-percent, and 6-percent reinforced nano ceramic fiber fillers; however, there was not a significant difference (p > 0.05) between control group, 4-percent, and 6-percent reinforced nano ceramic fiber fillers. The properties of the experiment were all lower than the control. Further research is needed to determine the appropriate material and amount of dispersing agent, coupling agent, and determination of the hydprophilicity of the nano ceramic fiber fillers with great emphasis on the dispersing agent.
36
Cameron, James. "Engineered Fibre-reinforced Concrete Systems for Bridge Deck Link Slab Applications." Thesis, 2014. http://hdl.handle.net/10012/8220.
Анотація:
Rehabilitation and maintenance of the aging transportation infrastructure are of major concern in the Province of Ontario. A large portion of this work is related to the durability of highway bridges around the province. One of the weakest points in a bridge structure from a durability aspect is the expansion joints that can allow harmful elements, such as road salts and contaminants to leak down from the road surface and attack the supporting structure of the bridge. Although expansion joints can be eliminated in the design of a new bridge, such as in an integral abutment bridge, this requires major changes to the supports and structure of the bridge, making it impractical for retrofitting existing bridges. One effective alternative is the replacement of a traditional expansion joint with a link slab. A link slab is a concrete slab used in place of an expansion joint to make the bridge deck continuous while keeping the supporting girders simply supported [1]. Link slabs must be able to resist large force effects both in bending and direct tension while minimizing cracking [2], one solution is to use the high tensile and flexural strength properties of an ultra-high performance fibre-reinforced concrete (UHPFRC) [3]. The UHPFRC mixtures are often proprietary and expensive. The purpose of this research was to evaluate the potential of using common fibre types with standard concrete ingredients in a fibre-reinforced concrete (FRC) as an alternative to UHPFRC in a link slab. Using a selection of macro fibres commonly used in slab on grade applications for crack control, an optimized FRC mixture was developed following the principals established by Rossi and Harrouche [4]. This mixture was then used with a variety of fibre types to evaluate the structural and durability properties of the FRC. Testing was conducted for fresh mixture properties, compressive, tensile and flexural strength as well as freezing and thawing resistance, linear shrinkage, environmental and salt exposure along with other durability tests. Results showed that the concrete mixture used for an FRC link slab should consist of; an equal ratio of fine and coarse aggregate by weight and a higher than normal percentage of cement paste, for optimal workability and a dosage of 1.5% by volume of macro steel fibres. Hooked-end steel fibres resulted in the best performance increase to the FRC of the six fibre types tested. Results also showed that reinforcing cage for an FRC link slab should be designed to ensure that fibres can evenly reach all areas of the link slab form to give homogeneous fibre distribution. Although the FRCs created did not perform to the high level of a UHPFRC, these results show a consistent and effective FRC can be created, for use in a link slab with common fibres and standard concrete materials to provide a less expensive and more widely available FRC link slab than UHPFRC.
37
"Development of Design Procedures for Fiber Reinforced Concrete (FRC) & Ultra-High-Performance Concrete (UHPC) Based on Experimental Evaluations." Master's thesis, 2018. http://hdl.handle.net/2286/R.I.51767.
Анотація:
abstract: A comprehensive study was performed on non-proprietary ultra-high-performance concrete (UHPC) material and several design methods were suggested based on numerous experimental results. Several sets of compression tests, direct tensile tests, and flexural tests were performed on UHPC to provide a better understanding of the mechanisms involved in the mechanical behavior of the fiber reinforced material. In addition to compressive tests, flexural tests, based on ASTM C1609 and EN 14651, were performed. The effect of the strain rate on the UHPC material was also investigated through the high-speed tensile tests at different strain rates. Alongside the usual measurement tools such as linear variable differential transformers (LVDT) and clip gages, digital image correlation (DIC) method was also used to capture the full-range deformations in the samples and localized crack propagations. Analytical approaches were suggested, based on the experimental results of the current research and other research groups, to provide design solutions for different applications and design approaches for UHPC and hybrid reinforced concrete (HRC) sections. The suggested methods can be used both in the ultimate limit state (ULS) and the serviceability limit state (SLS) design methods. Closed form relationships, based on the non-linear design of reinforced concrete, were used in the calculation of the load-deflection response of UHPC. The procedures were used in obtaining material properties from the flexural data using procedures that are based on back-calculation of material properties from the experimental results. Model simulations were compared with other results available in the literature. Performance of flexural reinforced UHPC concrete beam sections tested under different types of loading was addressed using a combination of fibers and rebars. The same analytical approach was suggested for the fiber reinforced concrete (FRC) sections strengthened (rehabilitated) by fiber reinforced polymers (FRP) and textile reinforced concrete (TRC). The objective is to validate the proper design procedures for flexural members as well as connection elements. The proposed solutions can be used to reduce total reinforcement by means of increasing the ductility of the FRC, HRC, and UHPC members in order to meet the required flexural reinforcement, which in some cases leads to total elimination of rebars.Dissertation/Thesis
Masters Thesis Civil, Environmental and Sustainable Engineering 2018
38
Silva, Gustavo Corrêa Alves da. "Topological optimization of structures produced through 3D printing of fiber reinforced cementitious materials." Master's thesis, 2021. http://hdl.handle.net/1822/71314.
Анотація:
Dissertação de mestrado integrado em Engenharia CivilTopology optimization can play an important role in the Architecture, Engineering and Construction (AEC) sector. This technology along with digital manufacturing can be a game changer in the future of civil construction, allowing to build, in a short time period, lighter constructions with very geometry complexity but keeping the same of even better structural functioning. These optimized structures when coupled with a material with high capacity efforts redistribution, e.g. fibre reinforced cementitious material (FRC), can partially or totally substitute the conventional reinforcement, consequently less raw material is use, contributing for a better sustainable development. Following this idea, this dissertation will focus on study topology optimization processes along with the use of FRC materials. Initially a comparison between some topology optimization software’s will be carried out, in order to proper evaluate to most suitable for the realization of the present work. In a second stage, considering only the linear behavior of the material, different topology optimization analyses will be done. These analyses will be based on the geometry and the intended structural application (support and load conditions), in addition to the optimization goal (design variable and constraint). This part aims to assess the influence of height / length ratio (H/L ratio) of the beam, in the optimization outcome. After that, a study of the influence of reinforcement amount in the optimization will be done. Afterwards, some finite element analysis (FEA) for one of the optimized structures will be performed and assessed using distinct approaches for obtaining the tensile stress – strain relationship, namely by adopting the ultimate limit state (USL) and service limit state (SLS) tensile diagrams according to the recommendations presented in FIB Model Code 2010. These simulations will serve to evaluate the nonlinear behavior of the FRC structure. For this study six FRC with different strength classes were considered. Finally, an optimized structural element obtained through the FEA was sliced for 3D printing and the influence of the nozzle dimensions, i.e. printing resolution was checked.
A otimização da topologia pode desempenhar um papel importante no setor de Arquitetura, Engenharia e Construção (AEC). Esta tecnologia aliada à manufatura digital pode completamente revolucionar o futuro da construção civil, permitindo construir, num curto espaço de tempo, construções mais leves, mas mantendo o mesmo ou ainda melhor funcionamento estrutural. Estas estruturas otimizadas quando conjugadas a um material com alta capacidade de redistribuição de esforços, por ex. materiais cimentícios reforçado com fibras (FRC), pode substituir parcial ou totalmente o reforço convencional, onde consequentemente menos matéria-prima será utilizada, contribuindo-se assim, para um melhor desenvolvimento sustentável. Seguindo essa ideia, esta dissertação terá como foco estudar processos de otimização de topológica juntamente com o uso de materiais FRC. Inicialmente será realizada uma comparação entre alguns softwares de otimização de topológica, a fim de avaliar adequadamente o mais adequado para a realização do presente trabalho. Em uma segunda etapa, considerando apenas o comportamento linear do material, serão realizados diferentes processos de otimização topológica. Essas otimizações serão baseadas na geometria e na aplicação estrutural pretendida e no objetivo da otimização. Esta parte visa avaliar a influencia da relação altura/comprimento da viga (relação H/L), no resultado da otimização. Posteriormente, algumas análises de elementos finitos (FEM) para uma das estruturas otimizadas serão realizadas e avaliadas usando duas abordagens distintas para a obtenção da relação tensão de tração – deformação, uma para estado limite último (ELU) e estado limite de serviço (ELS), seguindo as recomendações presentes no FIB Model Code 2010. Estas simulações servirão para avaliar o comportamento não linear da estrutura de FRC. Para este estudo foram considerados seis FRC com diferentes classes de força. Finalmente, para um elemento estrutural otimizado anteriormente, foi realizada uma simulação de impressão 3D, de modo a estudar a influencia do tamanho do bico de impressão, ou seja, a resolução de impressão foi verificada.
39
Hsu, CheChang, and 許哲彰. "The Analysis of Processing of Three-Dimensional SiC Fiber -Reinforced Two-Phase Ceramics." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/19320608101779134950.
Анотація:
碩士逢甲大學
機械工程學系
88
The goals of this research are to fabricate three-dimensional(3D) ceramic matrix composites (CMCs) by infiltrating silica sol and alumina particles into 3D SiC preform. Green body density, mechanical properties of 3D ceramic matrix composites were evaluated. Using sol-gel method and pressure infiltration method to produce composite green body usually causes serious crack die to strain recovery of alumina particles and the 3D fabric released from mold, and drying shrinkage. In this study, poly vinyl alcohol(PVA) was added into silica sol to restrain the crack. The effect of infiltration pressure and PVA addition on propreties of green body were investigated. It is shown that high infiltration pressure can fabricate ceramic matrix composites with high density, and the addition of PVA reduces cracks in the matrix after hot press. Mechanical properties of ceramic matrix composites are influenced by surface fracture, particle packing density and fiber/matrix bonding strength. Composites fabricated by medium infiltration pressure have high flexural strength. Their damage modes are debonding, fiber pull-out and crack bridging. But the high infiltration pressure causes stress concentration because of surface fracture, leading to the reduction of flexure strength. Impact energy is proportional to percentage theoretical density of composites. High impact energy depended on high density of composites with high infiltration pressure and increasing PVA content.
40
Chen, Yi-Ting, and 陳奕廷. "Preparation and Characterization of Glass Ceramics by Thermal Plasma Treatment of Fiber Reinforced Plastics." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/86077600466871994230.
Анотація:
碩士國立臺灣海洋大學
材料工程研究所
92
Mixing the fiber reinforced plastic (FRP), fishnet and waste glass to form vitrification slags by thermal plasma and the resultant slags were characterized for their physical and chemical properties. Using EDO (Experimental Design Optimizer) and MC (Multi-Correlation) programs, optimization of waste stream such as ratio and type of wastes is determined in order to achieve better slag properties. The plasma furnace built by the Institute of Nuclear Energy Research (INER), Taiwan exclusively for the vitrification testing of hazardous/radioactive waste surrogates was used for our present work. For the vitrification processing, we have employed the plasma as the heating source to treat wastes containing metals and organic complexes at temperatures in the range of 1250 to 1400° C. The average density of slag is around 2.5g/cm3, the hardness range of slag is 545~603Hv. This study is directed towards the optimization of waste stream for plasma vitrification treatment, in order to establish a better understanding of the feasibility of the plasma system in treating fishery wastes. Two stage heating treatment was used in this study and the wollastonite was formed with a suitable additive. Our wollastonite products exhibit better properties (such as hardness, bending strength, compressive strength and chemical resistance) than those of the commercial products. Keywords: vitrification slag, fiber reinforced plastic (FRP), wollastonite, plasma vitrification.
41
Seo, Sang Yeon. "Use of non-steel fiber reinforcement in concrete tunnel lining." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-08-1816.
Анотація:
Fiber reinforcement is being widely used in concrete tunnel linings these days. Using fiber reinforcement can save not only cost, but also labor and time spent on construction. However, many owners hesitate to incorporate fiber reinforcement in tunnel lining due to lack of experience with and knowledge of the behavior of fiber reinforced concrete (FRC)
In this study, fiber reinforced concrete was made with various kinds of fibers such as steel fiber, macro-synthetic fiber and hybrid fiber (a blend of macro-synthetic fiber and glass fiber). Many experimental tests were performed to investigate the compressive, flexural and shear behavior of fiber reinforced concrete. In addition to the structural capacity of FRC, the distribution of fiber reinforcement inside the concrete matrix was investigated. Test results of these experimental tests were thoroughly examined to compare and quantify the effects of fiber reinforcement. Next, the test results were used to generate axial force-bending moment interaction diagrams based on current design approaches. In addition, the current design approaches were modified to estimate the accurate and exact value of bending moment. Fiber reinforcement clearly improved the structural performance of tunnel lining. The post-peak flexural and shear strength was significantly influenced by the type and amount of fiber reinforcement.text