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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
581

SÍNTESE E CARACTERIZAÇÃO DE ESPUMAS VÍTREAS CONTENDO TiO2 E UTILIZANDO HIDRÓXIDO DE SÓDIO COMO AGENTE ESPUMANTE

Bento, André César 10 April 2012 (has links)
Made available in DSpace on 2017-07-21T20:42:36Z (GMT). No. of bitstreams: 1 Andre Cesar Bento.pdf: 1732687 bytes, checksum: 53eb9d5eb1ee3aca52e7d78b1169f466 (MD5) Previous issue date: 2012-04-10 / In this work, the effect of sodium hydroxide as a glass foaming agent using glass waste in the foam formulation was performed. During the synthesis process, the variation of temperature, heating rate and sintering time was investigated. Sample density and average pore sizes were estimated using mercury porosimetry. The morphology of the glass foams were evaluated using scanning electron microscopy, phase formation was studied using X-ray diffraction, and chemical composition was estimated using X-ray fluorescence. As a result, glass foam with hierarchical density. / Neste trabalho foi realizado um estudo sobre a ação do hidróxido de sódio como agente formador de espuma vítrea usando resíduos de vidro em sua composição. Para a síntese, investigou-se a variação da temperatura, da taxa de aquecimento e do tempo de sinterização. Utilizando-se a técnica de porosimetria de mercúrio, para estimar a densidade e o tamanho médio de poros. A morfologia das espumas vítreas foi avaliada através da microscopia eletrônica de varredura de alta resolução (FEG) e as fases das espumas vítreas foram caracterizadas pelas técnicas de difração de raios X e a composição química estimada usando fluorescência de raios X.
582

Effects of radiation damage and composition on phase separation in borosilicate nuclear waste glasses

Patel, Karishma Bhavini January 2018 (has links)
In order to increase the waste loading efficiency of nuclear waste glasses, alternative composite structures are sought that trap molybdenum in a water-durable CaMoO4 phase. In this thesis, the formation and stability of CaMoO4 in a borosilicate glass against the attack of internal radiation was investigated. It is a fundamental study that simplified the composition to known contributors of molybdate speciation, and further splits the com- ponents of α and β-decay into integral parts that replicated both nuclear and electronic interactions. Irradiation experiments using 2.5 MeV β, 7 MeV Au, and 92 MeV Xe ions were enlisted to test the hypotheses of whether 100−1000 years of radiation damage given current waste loading standards would: (i) induce phase separation in homogeneous re- gions, (ii) increase the extent of existing phase separation, (iii) induce local annealing that could cause amorphisation of crystalline phases or increase mixing between amorphous phases, or (iv) cause some combination of the above. Results from XRD, SEM, EPR, and Raman spectroscopy suggest that powellite is stable against replicated radiation damage with only minor modifications observed. The main mechanisms of alteration involved: (i) thermal and defect-assisted diffusion, (ii) relaxation from the added ion’s energy, (iii) localised damage recovery from ion tracks, and (iv) the accumulation of point defects or the formation of voids that created significant strain, and led to longer-range modifications. It can be further concluded that no precip- itation or increased phase separation was observed in single-phased glasses. In isolated cases, radiation-induced precipitation of CaMoO4 occurred, but these crystallites were reamorphised at higher doses. At high SHI fluences, minor amorphisation of powellite was also observed, but this occurred alongside bulk-to-surface reprecipitation of CaMo- species. Overall, the components of internal radiation were often found to have opposing effects on the alteration of Si−O−B mixing in the glass, ion migration, and crystallite size. This led to the prediction that a steady-state damage structure could form from cumulative decay processes. These results suggest that CaMoO4 containing borosilicate GCs are resistant to radiation, and that excess molybdenum from increased waste loading can be successfully incorporated into these structures without altering the overall dura- bility of the wasteform. Furthermore, the identified saturation in modifications occurring around 8 x 10¹⁴ Xe ions/cm² can be used as a benchmark in future investigations on more complex systems where the maximum damage state is required.
583

L’activité verrière dans le quart sud-ouest de la France du XIVe au XVIIe siècle : production, consommation, commercialisation / Glass activity in the South-West of France from the 14th to the 17th century : production, use and marketing

Hébrard-Salivas, Catherine 16 December 2014 (has links)
Si la présence d’une activité verrière ne semble être connue qu’à partir du XIVème siècle dans le quart sud ouest de la France, c’est véritablement au XVIème siècle qu’elle prend toute son ampleur et atteint son apogée, au vu des nombreux ateliers établis à cette période. En confrontant les archives écrites et les « archives du sol », cette étude vise à apporter un éclairage sur l’évolution de la production du verre entre la période médiévale et la période moderne, et sur les relations qui régissent les maitres verriers, les marchands et les producteurs de matières premières entrant dans la composition du verre. Les flux d’échanges issus de cette activité verrière mettent en relief l’activité économique importante générée au départ d’installations ancrées localement à proximité des ressources forestières indispensables au fonctionnement des fours des verriers, et qui pourtant irriguent l’économie régionale en favorisant les échanges commerciaux et en développant un écosystème autour du transport, de l’activité bancaire, et du troc de marchandises. L’une des caractéristiques fortes de ces échanges commerciaux est qu’ils allient deux espaces maritimes, mer méditerranée et océan atlantique, sur un axe reliant La Rochelle à Narbonne. L’étude des objets en verre fabriqués dans cette zone géographique tend plutôt à montrer que la fabrication est diversifiée, tant vis-à-vis des types d’objets que dans les formes réalisées. Seules quelques productions locales particulières semblent s’adresser à un marché local ou régional. / If the presence of a glass activity seems known only from the 14th century on in the South-West of France, it's truly in the 16th century that it spread and reached its peak, given the numerous workshops established at this time. Comparing the written archives and « ground archives », this study aims to shed light on the evolution of glass production between medieval times and modern times, and on the connections between glass-blowers, merchants and producers of raw materials necessary to the production of glass. The trade flows springing from this glass activity highlight the significant economic activity generated from local plants near forest ressources necessary for the working of glass ovens. These local plants supply regional economy favouring trade and developing an ecosystem based around transport, banking and bartering. One of the main characteristics of this trade is that it linked up two maritime areas, the Mediterranean sea and the Atlantic Ocean, on an axis from La Rochelle to Narbonne. The study of the glass objects made in this geographical area tends to show that the production is varied, both in terms of the types of objects and of the shapes created. Only a few particular local productions seem to be destined to a local or regional market.
584

Multifunctionalities Of Ceramics And Glass Nanocrystal Composites Of V2O5 Doped Aurivillius Family Of Ferroelectric Oxides

Venkataraman, B Harihara 10 1900 (has links) (PDF)
In recent years bismuth-based, layer-structured perovskites such as SrBi2Nb2O9 (SBN) and SrBi2Ta2O9 (SBT) have been investigated extensively, because of their potential use in ferroelectric random access memories (FeRAMs). In comparison with non-layered perovskite ferroelectrics such as Pb(Zr,Ti)O3 (PZT), these offer several advantages such as fatigue free, lead free, low operating voltages and most importantly their ferroelectric properties are independent of film thickness in the 90 to 500 nm range. For FeRAM device applications, large remnant polarization (Pr), low coercive field (Ec) accompanied by high Curie temperature (Tc) are required for better performance and reliable operation. Much effort has been made to improve the ferroelectric properties of SBN and SBT ceramics by doping on A or B sites. It was known in the literature that partial substitution of Sr2+ by Bi3+ ions in SBN and SBT would increase the Curie temperature and improve the dielectric properties. The focus of the investigations that were taken up was to improve the electrical, dielectric and ferroelectric characteristics of SrBi2Nb2O9 ceramics. It was reported that the ferroelectric and nonlinear optical properties of LiNbO3 and LiTaO3 could be improved when vanadium, the lightest element in group V of the periodic table is substituted for Nb or Ta along with Li and three oxygens. It is with this background the investigations have been taken up to see whether one can extend the same argument to the Aurivillius family of oxides. Therefore, the central theme of the present investigations aimed at substituting Nb5+ by a smaller cation V5+ in SBN and study its influence on the formation temperature, sinterability, structural and microstructural characteristics apart from its physical properties. Recently the optical properties of this material have been recognized to be important from the optical device point of view. Unfortunately single crystal growth of vanadium doped SBN was hampered because of the bismuth and vanadium loss (high volatility) observed in the process of growth. One of the routes that attracted our attention has been the glass-ceramic. It would be interesting to visualize the behavior of crystallites of nano/micrometer size embedded in a glass matrix as these crystals were known to give rise to exotic properties. One of the crucial steps in the process of fabrication of a glass nanocrystalcomposite system in which crystalline phases have symmetries that would eventually give rise to basic non - centrosymmetric properties such as piezoelectric, pyroelectric and Pockels effects, has been to choose a compatible matrix material associated with easy glass forming capability and the ability to evenly disperse dipolar defects within itself. Recent investigations into strontium borate SrB4O7 (SBO), lithium borate Li2B4O7 (LBO) glasses indicated that LBO by virtue of its favorable structure, thermal and optical properties would form a suitable host glass matrix for dispersing layer structured ferroelectric oxides belonging to the Aurivillius family of oxides. Since lithium borate has wide transmission window, it was worth making an attempt to fabricate optical composite of Li2B4O7 (LBO) and vanadium doped SrBi2Nb2O9 (SBVN) and to study its structural, dielectric, pyroelectric, ferroelectric and optical properties. Therefore the present thesis reports detailed investigations into the effect of vanadium doping on the structural and various physical properties of an n = 2 member of the Aurivillius family of oxides in the polycrystalline form and novel glass composites comprising nano/microcrystallites of this phase. Chapter 1 comprises a brief introduction to the dielectric, pyroelectric, ferroelectric and nonlinear optical properties of materials. In addition to the principles and phenomena, the material aspects of these important branches of physics are discussed. It also forms a preamble to the glasses, criteria for glass formation, glass – ceramics and subsequently ferroelectric and nonlinear optical effects that were observed in glasses and glass - ceramics. Chapter 2 describes the material fabrication techniques adopted to prepare polycrystalline and grain – oriented ceramics, glasses and glass nanocrystalcomposites. The details of various structural, dielectric, pyroelectric, ferroelectric and optical measurement techniques employed to characterize these materials are also included. Chapter 3 discloses the fabrication of strontium bismuth niobate ceramics and their characterization for dielectric and impedance properties. The dielectric properties of strontium bismuth niobate ceramics have been modeled based on Jonscher’s Universal formalism. The coefficients of the Jonscher’s expression, exponent n(T) undergoes a minimum and A(T) exhibits a peak at the Curie temperature, Tc (723K). A strong low frequency dielectric dispersion (LFDD) associated with an impedance relaxation has been found to exist in these ceramics in the temperature range 573 - 823K. The Z′′ of the AC complex impedance showed two distinct slopes in the frequency range 100Hz-1MHz suggesting the existence of two dispersion mechanisms. The exponents m and n were obtained from the curve fitting. The exponent n was found to exhibit a minimum at the Curie temperature, Tc (723K) whereas the m was temperature independent. Chapter 4 deals with the fabrication of vanadium doped SrBi2Nb2O9 ceramics and their characterization for microstructural, dielectric, pyroelectric and ferroelectric properties. The average grain size of the SrBi2Nb2O9 (SBN) ceramic containing V2O5 was found to increase with increase in V2O5 content. The dielectric constant (εr) as well as the dielectric loss (D) increased with increase in grain size (6µm-17µm). The pyroelectric coefficient was found to be positive at 300K and showed an increasing trend with increasing grain size. Interestingly, the SrBi2(Nb0.7V0.3)2O9-δ ceramics consisting of 17µm sized grains showed higher remnant polarization (Pr) and lower coercive field (Ec) than those with grains of 7µm. Chapter 5 deals with the dielectric properties which were studied in detail in the 100Hz to 1MHz frequency range at various temperatures (300 – 823 K) for undoped and vanadium (10 mol%) doped SrBi2Nb2O9 (SBVN10) ferroelectric ceramics. A strong low frequency dielectric dispersion was encountered in these ceramics in the 573 – 823 K temperature range. The dielectric constants measured in the wide frequency and temperature ranges for both the samples were found to fit well to the Jonscher’s dielectric dispersion relations. The dielectric behavior of SBN and SBVN10 ceramics was rationalized using the impedance and modulus data. The electrical conductivity studies of layered SrBi2(Nb1-xVx)2O9-δ ceramics with x lying in the range 0 to 0.3 (30 mol%) were centered in the 573 – 823K temperature range as the Curie temperature lies in this range. The concentration of mobile charge carriers (n), the diffusion constant (D0) and the mean free path (a) were calculated using Rice and Roth formalism. The conductivity parameters such as ion hopping rate (ωp) and the charge carrier concentration (K′) term have been calculated using Almond and West formalism. The afore mentioned microscopic parameters were found to be V2O5 content dependent in SrBi2(Nb1-xVx)2O9-δceramics. Chapter 6 describes the fabrication of partially grain – oriented SrBi2(Nb1-xVx)2O9-δ (0 ≤x≤3.0 in molar ratio) ceramics and characterization for their structural, microstructural, dielectric, pyroelectric and ferroelectric properties. The grain – orientation factor and the microstructural features were studied by XRD and scanning electron microscopy as a fuction of sintering temperature and V2O5 content. The dielectric constant measured along the direction parallel and perpendicular to the pressing axis has shown a significant anisotropy. The pyroelectric and ferroelectric properties were superior in the direction perpendicular to the pressing axis (polar) to that in the parallel direction. The fabrication and characterization details of (100 – x) (Li2B4O7) – x (SrO - Bi2O3 - 0.7 Nb2O5 – 0.3 V2O5) (10 ≤ x ≤ 60, in molar ratio) glasses and glass nanocrystal composites are dealt within Chapter 7. The nanocrystallization of strontium bismuth niobate doped with vanadium (SrBi2(Nb0.7V0.3)2O9-δ(SBVN)) has been demonstrated in Li2B4O7 glasses. The glassy nature of the as – quenched samples was established by differential thermal analyses (DTA). The amorphous nature of the as – quenched glasses and crystallinity of glass nanocrystal composites were confirmed by X – ray powder diffraction studies. High resolution transmission electron microscopy (HRTEM) of the glass nanocrystal composites (heat – treated at 783K/6h) confirm the presence of nano rods of SBVN embedded in Li2B4O7 glass matrix. Chapter 8 presents the physical properties of the glasses and glass nanocrystal composites. Dielectric constant of both the as – quenched and glass nanocrystal composites was found to increase with increase in the composition, whereas the loss was observed to decrease with increasing SBVN composition. Different dielectric mixture formulae were employed to analyze the dielectric properties of the glass nanocrystal composite. The electrical behaviour of the glasses and glass nanocrystal composites was rationalized using impedance spectroscopy. The observed pyroelectric response and ferroelectric hysteresis of these composites confirmed the polar nature. Various optical parameters such as optical band gap (Eopt), Urbach energy (∆E), refractive index (n), optical dielectric constant (ε′∞) and ratio of carrier concentration to the effective mass (N/m*) were determined. The effects of composition of the glasses and glass nanocrystal composites on these parameters were studied. Transparent glasses embedded with nanocrystallites of SBVN exhibited intense second harmonic signals in transmission mode when exposed to IR laser light at λ = 1064 nm. The thesis ends with a summary of the important findings and conclusions.
585

Borate Based Glasses, Transparent Glass-Microcrystal Composites And Their Physical Properties

Vaish, Rahul 12 1900 (has links) (PDF)
Transparent glasses embedded with ferroelectric/nonlinear optic crystallites have been in increasing demand as these exhibit promising physical properties. These could be fabricated in large sizes and shapes with high optical homogeneity accompanied by high degree of transparency over a wide range of wavelengths of light. Amongst a variety of glasses that are known, borate-based glasses are of particular interest owing to their greater transparency, good chemical and mechanical stability, low materials cost, and useful electrical and dielectric properties. Keeping the potential multifarious applications of transparent glass-microcrystal composites in view, BaO-0.5Na2O-4.5B2O3, BaO-0.5Li2O-4.5B2O3, SrO-0.5Li2O-4.5B2O3, 3BaO-3TiO2-B2O3 and Li2O-3B2O3 glasses and glass-microcrystal composites were fabricated. These glasses on controlled heat treatment at appropriate temperatures yielded BaNaB9O15, BaLiB9O15, SrLiB9O15, Ba3Ti3B2O12 and LiB3O5 crystalline phases, respectively. Further transparent surface crystallized BaO-0.5Na2O-4.5B2O3 glasses were fabricated using ultrasonic treatment and their thermal properties have been investigated in detail using differential scanning calorimetry. It is observed that these glasses were homogeneously crystallizing on the surfaces after Ultrasonic treatment which can be exploited for planner wave-guide applications. Glass forming ability, thermal stability, glass-transition behavior, crystallization kinetics and viscosity of these glasses were studied extensively using various methods and rationalized by invoking various models. The above glasses have been characterized for their dielectric and electrical relaxation properties (as these properties are related to their electro-optic and non-linear optical properties) over 30- 600oC temperature range and frequencies (100 Hz -10 MHz) that are normally of interest in the applications of these materials. Several interesting features such as high ionic conductivity, marginally low dielectric loss and high dielectric constant behavior along with low thermal coefficient of dielectric constant were observed in these glasses and were rationalized using various models. The combination of these dielectric characteristics suggests that these are potential candidates for electrical energy storage device applications.
586

Comportement à l'indentation et à la rayure de verres métalliques et silicatés / Mechanical behaviors of metallic and silicate glasses from indentation to scratch

Hin, Raveth 21 November 2017 (has links)
Le comportement mécanique du verre silico-sodo-calcique soumis à un contact ponctuel peut être amélioré par trempe. Les effets de trempe se manifestent par des gradients de propriétés sur le comportement du verre rendant la modélisation plus complexe. Ce travail a porté sur la modélisation et la simulation des verres non trempés et trempés soumis aux essais de nano-indentation et de nano-rayage. Les outils de simulation par éléments finis ont été développé et validés sur le verre métallique, choisi en raison de son comportement plastique connu. En comparant avec les données expérimentales, nous avons observé que les paramètres du matériau et les conditions expérimentales pouvaient donner la même réponse sur la courbe force-déplacement et l'empreinte. L’identification des propriétés du matériau doit être basée sur des comparaisons avec des simulations considérant la géométrie réelle de l'indenteur, la souplesse de la machine et le tilt de surface de l'échantillon. Les stratégies développées permettent de faire des identifications sur le comportement du verre silico-sodo-calcique. Dans la famille du verre silicaté, le verre silico-sodo-calcique a un comportement plastique semblable au verre de silice qui est affecté non seulement par le mécanisme de cisaillement mais aussi par la densification. Il est essentiel donc d'étudier le comportement densification/cisaillement du verre de silice car il est largement discuté dans la littérature. La comparaison des résultats de simulation par plusieurs modèles avec les courbes force-déplacement et les images d'empreinte a montré que la modélisation de la densification, en prenant en compte l'écrouissage et la modification des modules élastiques, est suffisante pour décrire le comportement des verres silicatés. Enfin, les connaissances sur les simulations des essais à chargement ponctuel et la modélisation du comportement du verre ont guidé une étude sur les effets du gradient de propriétés dans les verres trempées thermiquement et chimiquement. / The mechanical behavior of soda-lime-silica glass subjected to contact damage can be improved by tempering. The effects of tempering created tailor properties and the glass behavior more complicated. Therefore, this work studied the modeling and simulation of non-tempered and tempered glasses subjected to the nano-indentation and nano-scratch tests. The finite element simulation tools have been primarily validated and the metallic glass was chosen for the studies because of its known plastic behavior. By comparing with the experimental data, we have observed that the parameters of material model and the experimental conditions could give the same response on load displacement curve and imprint. The evaluation of material properties must be based on the comparisons with fully modeled simulation considering the real geometry of the indenter, the compliance of the instrument and the tilting of the sample surface. The developed strategies allow identification of soda-lime-silica glass behavior. Similar to that of silica glass, the plastic behavior of soda-lime-silica glass is not only affected by the shear mechanism but also the densification. Hence, it is essential to study the shear/densification behavior of silica glass as it is widely discussed in the literature. The comparison of simulation results by several models with the load displacement data and the images of imprint showed that the modeling of densification by taking into account the hardening and the change in elastic moduli is sufficient for describing the behavior of silicate glasses. Finally, the knowledge about the simulation of the contact loading tests and the modeling of glass behavior guided a study on the coupling of tailored properties effects in the thermally and chemically tempered glasses.
587

Beteende hos laminerade glasbalkar med och utan sprickor / Behaviour of laminated glass beams with and without cracks

Basim, Weaam, Abdul Khader, Nour, Rehsid, Vijan January 2020 (has links)
Det blir allt vanligare att använda laminerat glas som ett konstruktionsmaterial. Men glas är ett känsligt och genomskinligt material som kan ge en obehaglig känsla om det spricker. Särskilt om det handlar sig om en glaskonstruktion som ska hålla en stor del av en byggnad. En glaskonstruktion bör upplevas trygg att vistas i. Idag är det svårt att ersätta bärande konstruktionsdelar med glas i Sverige  eftersom det inte finns några särskilda dimensioneringsregler för glas. I det här examensarbetet genomförs en undersökning om hur laminerat glas böjer sig när det utsätts för belastning och varierande temperaturer under en kort tid. Det studeras hur tjockleken på mellanskiktet påverkar spänningen samt skjuvstyvheten i glasen. För att få relevanta jämförelser studeras även beteendet hos en osprucken och en sprucken laminerad balk. Med hjälp av litteraturstudier och teoretiska beräkningar har beteendet hos laminerade glasbalkar med olika förutsättningar undersökts. Resultatet visar att belastningar som verkar på en laminerad balk under en kort tid leder till ett varierande beteende och deformationer beroende på temperatur, skjuvstyvhet och tjocklek hos laminatet. Det upptäcktes ett gränsvärde vid temperaturen 50 °C där en förändring sker i sambandet mellan laminatets tjocklek, temperatur och nedböjningen. Beteendet och deformationen hos en laminerad balk varierar också beroende på om balken är sprucken eller inte. / It is becoming increasingly common to use laminated glass as a construction material. But glass is a sensitive and translucent material that can give an unpleasant feeling if it cracks. Especially if it is a glass structure that will hold a large part of a building. A glass structure should be considered safe to stay in. Today, it is difficult to replace supporting structural parts with glass in Sweden due to the lack of design rules. In this thesis, a study is conducted on how laminated glass bends when exposed to mechanical loads and varying temperatures for a short time. It is studied how the thickness of the middle layer plays a role, how the tension and the shear stiffness vary in the glass. In order to obtain relevant comparisons, the behavior of an unbroken and a cracked laminated beam is also studied. With the help of literature studies and theoretical calculations, the behavior of laminated beams under different conditions was examined. The results show that loads that act on a laminated beam for a short time lead to varying behavior and deformations depending on temperature, shear stiffness and interlayer thickness. A limit value was detected at the temperature of 50 °C where a change in the relation between interlayer thickness, temperature and deformation occurs. The behavior and deformation of a laminated beam also varies whether the laminate is cracked or not cracked.
588

The American Studio Glass Movement: A Regional Study of its Birth in Northwest Ohio

Harrington, Kaysie Marie 26 November 2018 (has links)
No description available.
589

Entwicklung von Dünnglas-Kunststoff-Hybridplatten für das Bauwesen

Hänig, Julian 19 July 2023 (has links)
Moderne architektonische Fassadengestaltungen und Ganzglaskonstruktionen fordern immer häufiger entmaterialisiert wirkende Ansichten mit maximaler Transparenz für eine edle Erscheinung und einen hohen Grad an natürlicher Belichtung. Damit gehen große Spannweiten einher. Diese führen zu stark dimensionierten Glasaufbauten und bringen hohes Eigengewicht in die Konstruktion ein. Die Verfügbarkeit von Dünnglas in bautechnisch relevanten Abmessungen ermöglicht neue gewichtssparende Konstruktionsprinzipien und innovative Materialkombinationen. Dünnglas-Kunststoff-Hybridplatten bestehen aus einem leichten transparenten Kunststoffkern mit außenliegenden kratzbeständigen und dauerhaften Deckschichten aus Dünnglas. Sie bieten eine hohe Steifigkeit, Dauerhaftigkeit und volle Transparenz bei geringem Eigengewicht. Die Aushärtung der Ausgangskomponenten des Kunststoffkerns erfolgt direkt zwischen den Deckschichten und erzeugt dadurch einen vollflächigen Verbund zwischen Glas und Kunststoff ohne zusätzliche Zwischenschichten. Im Bauwesen sind Dünnglas-Kunststoff-Hybridplatten bislang unbekannt. Es liegen weder ausreichend Kenntnisse zu den Material- und Verbundeigenschaften vor noch sind die Eigenschaften als Bauprodukt entsprechend den hohen strukturellen und sicherheitstechnischen Anforderungen sowie den Ansprüchen an die Dauerhaftigkeit und an die optischen Eigenschaften nachgewiesen. Darüber hinaus fehlen konkrete Verbindungskonzepte zur Integration in das Bauwesen, um das Leichtbaupotenzial für entmaterialisiert wirkende transparente Konstruktionen auszunutzen. Im Rahmen dieser Arbeit werden erstmals Dünnglas-Kunststoff-Hybridplatten als innovatives Leichtbauprodukt systematisch untersucht und in das Bauwesen eingeordnet. Experimentelle und numerische Untersuchungen charakterisieren die Material- und Verbundeigenschaften mit zwei, am Markt verfügbaren, Kunststoffkernmaterialien – Polymethylmethacrylat (PMMA) und Polyurethan (PU), die jeweils für ein unterschiedliches Eigenschaftsspektrum stehen. Darüber hinaus wird zur Umsetzung maximaler Transparenz eine materialgerechte Verbindungstechnik entwickelt und deren mechanische Tragfähigkeiten charakterisiert. Zunächst werden in experimentellen Kleinteilprüfungen die thermophysikalischen und mechanischen Kennwerte der reinen Kunststoffkernmaterialien für die Beschreibung des Tragverhaltens im Verbund ermittelt. Anhand der Ergebnisse werden das PMMA als steifes, dauerhaftes, aber sprödes Material und das PU als vergleichsweise flexibles, zähes Material charakterisiert. Die experimentellen Untersuchungen zum Verbundverhalten fokussieren sich auf die Anforderungen für den Einsatz im Bauwesen. Eine numerische Strukturanalyse erweitert die Ergebnisse zum Tragverhalten und klärt offengebliebene Fragestellungen zum thermischen Ausdehnungsverhalten. Die Ergebnisse zeigen, dass mit Dünnglas-Kunststoff-Hybridplatten ein effizientes Tragverhalten und eine signifikante Gewichtsreduktion gegenüber herkömmlichem monolithischem Glas und Verbundglas erreicht wird. Anhand der spezifizierten Verbundeigenschaften werden resultierende Anwendungspotenziale entsprechend der Materialkombination abgeleitet. Die weiterführende Entwicklung einer tragfähig in den Kunststoffkern integrierten Verbindungstechnik bietet innovative Anbindungsmöglichkeiten für Dünnglas-Kunststoff-Hybridplatten im Strukturleichtbau. Die Funktionsweise wurde anhand eines Konstruktionsbeispiels auf der „glasstec 2022“ demonstriert. Die vorliegende Arbeit beinhaltet eine strukturierte Kennwertsammlung zur erstmaligen ingenieurmäßigen Beschreibung des Material- und Verbundverhaltens von Dünnglas-Kunststoff-Hybridplatten mit zwei unterschiedlichen Kunststoffkernmaterialien. Die Materialkombination aus Dünnglas und PMMA-Kunststoffkern erzielt die größte Materialeffizienz für eine effektive Gewichtsreduktion und erfüllt die grundlegenden Anforderungen aus dem Bauwesen. Anhand der weiterführend entwickelten konstruktiven Verbindungstechnik wird ein breiter Anwendungsbereich erschlossen. Mit den Ergebnissen dieser Arbeit werden somit die Grundlagen für die Einführung als Bauprodukt und für eine gewichtssparende Konstruktionsweise zur Umsetzung maximaler Transparenz geschaffen.:1 Einleitung 2 Grundlagen 3 Dünnglas-Kunststoff-Hybridplatten 4 Materialcharakterisierung Kunststoffkern 5 Verbundverhalten 6 Numerische Strukturanalyse 7 Einordnung in das Bauwesen 8 Konstruktive Verbindungstechnik 9 Konstruktionsbeispiel und Empfehlungen 10 Zusammenfassung und Ausblick 11 Literatur / Modern façade designs and all-glass construction are increasingly calling for dematerialisation and maximum transparency for a sophisticated appearance and a high degree of natural lighting. This is accompanied by large glass spans leading to increasing thickness of glass panels that introduce a high dead load into the supporting structure. The availability of thin glass in architecturally relevant dimensions permits new lightweight design principles and innovative material combinations. Innovative thin glass-plastic-composite panels consist of a lightweight and transparent polymeric interlayer core with scratch-resistant and durable cover layers of thin glass. They offer high stiffness, durability and full transparency at a low specific weight. The raw components of the polymer core are directly cured between the cover layers resulting in a chemical bond between glass and polymer over the entire surface without the need for additional interlayers. The thin glass-plastic-composite panels are currently unknown in the building industry. There is a lack of knowledge about the material and its composite behaviour. It has not been verified as a building product in accordance with the high structural and safety requirements as well as the requirements for durability and optical properties. In order to employ the lightweight design potential for dematerialised and transparent construction suitable for the building industry, there is a need for specific and material-appropriate connection techniques. In the context of this thesis, the novel thin glass-plastic-composite panels are systematically investigated in order to assess them as an innovative lightweight product. For the first time, they are classified in detail for application in the building industry. Material and composite properties using two different polymeric interlayer core materials – polymethyl methacrylate (PMMA) and polyurethane (PU) – are characterised by means of experimental and numerical investigations. Moreover, to achieve maximum transparency, a material-specific connection technique is developed and a wide range of mechanical load-bearing capacities are specified. First of all, the thermophysical and mechanical parameters of the pure polymer core materials are determined in experimental small part tests for the description of the composite load-bearing behaviour. The results identify the PMMA as a stiff, durable but brittle material and the PU as a fairly flexible, viscoelastic material. The investigations on the composite behaviour focus on the demands for use in the building industry and include experimental tests on the durability, the adhesion, the composite load-bearing behaviour as well as the response to hard and soft body impacts. A numerical analysis extends the results of experimental investigations on the structural load-bearing behaviour and examines the thermal expansion behaviour. The results indicate that the new material combination achieves a highly efficient structural load-bearing behaviour and a significant weight reduction compared to conventional monolithic and laminated glass. Application possibilities are derived based on the observed interlayer core material and composite characteristics. Further development of a connection technique as an integrated design into the polymeric interlayer core offers wide-ranging concepts of connecting thin glass-plastic-composite panels. Its functionality and practicability have been demonstrated in a construction prototype exhibited at “glasstec 2022” fair. The present work contains a well-structured material dataset to describe the material and composite behaviour of thin glass-plastic-composite panels comprehensively with two different polymeric interlayer core materials in engineering methodology. The material combination of thin glass and PMMA interlayer core achieves outstanding material efficiency with an effective weight reduction and fulfils the general requirements for application in building industry. A wide range of applications is facilitated thanks to the further development of a slim and integrated structural connection technique. The results of this work provide the framework for the introduction of a new lightweight building product with an innovative structural design to realise maximum transparency of façades and all-glass structures.:1 Einleitung 2 Grundlagen 3 Dünnglas-Kunststoff-Hybridplatten 4 Materialcharakterisierung Kunststoffkern 5 Verbundverhalten 6 Numerische Strukturanalyse 7 Einordnung in das Bauwesen 8 Konstruktive Verbindungstechnik 9 Konstruktionsbeispiel und Empfehlungen 10 Zusammenfassung und Ausblick 11 Literatur
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Comparison of Computational Modeling of Precision Glass Molding of Infrared Lenses

Moghaddas, Mohamad Amin 09 July 2014 (has links)
No description available.

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