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Preparation of MDF composites of increased moisture resistance
Žůrová, Marcela ; Šiler, Pavel (referee) ; Šoukal, František (advisor)
The subject of the thesis is to improve the moisture resistance of MDF (macro-defect-free) composites prepared on the basis of aluminous cement and polyvinyl alcohol. These materials are characterized by the absence of defects in the structure and high mechanical performance. These features make MDF composites a promising type of material that could be used in the future for construction purposes. The basic deficiency of MDF composites is insufficient resistance to water or moisture, accompanied by a significant decrease in strength. Therefore, this work deals with increasing of moisture resistance using organotitanate agent and modification of the polymer. Two types of polyvinyl alcohols differing in hydrolysis degree and degree of the polymerization has been modified. Based on the results of the measurement the effect of storage conditions on the properties and structure of prepared MDF composites was observed. The characterization of MDF composites were realized by measurement of flexural strength in bending, scanning electron microscopy with EDS analysis, TG-DTA-EGA, water absorption and consequently the porosity of all prepared MDF composites.
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Wing structure
Kaňák, Ondřej ; Weis, Martin (referee) ; Jebáček, Ivo (advisor)
This bachelor’s thesis deal with the wing structure of small aeroplanes. Step by step we are discovering different kinds of constructions and their usage in aerospace industry. Characteristic signs (shape, geometric,load), advantages and disadvantages construction types are shown in this work.
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A comparative study of ultimate load and stiffness of metal-to-composite joints
Tchír, Michal ; Šebek, František (referee) ; Vrbka, Jan (advisor)
V současnosti jedna z metod spojování zejména tlustých a vysoce zatížených kompozitních komponent je šroubový spoj, který je možné rozebrat pro případ opravy na rozdíl od lepeného spoje. Kompozitní konstrukce se tradičně dimenzují tak, aby během provozu nedošlo k porušení první vrstvy laminátu, nicméně důležité je taky poznat chování laminátu po porušení první vrstvy. Pro strukturální analýzu nejenom spojů, ale také dalších komponent se používá metoda konečných prvků a protože moderní nelineání řešiče jsou schopné modelovat chování laminátu po porušení první vrstvy, tato schopnost jednoho z nich byla využita v této práci při zkoumaní chování sklolaminátu spojeného s hliníkovou částí šrouby. Konečno-prvkové modely dvou spojů kovové a kompozitní části konstrukce schopné popsat progresivní porušování laminátu byly postaveny s využitím tří různých poruchových kritérií – kritéria maximálního napětí, kritéria Hill a kritéria Tsai-Wu. Problém byl řešen s využitím řešiče Nastran. Křivky síla-posuv, tuhost-posuv a hodnoty zatížení při hraničním posuvu byly porov-nány s výsledky experimentů. Jelikož faktor zbytkové tuhosti ovlivňuje výsledky ana-lýzy progresivního porušování, byly provedeny citlivostní studie zkoumajíci vliv faktoru na přesnost a stabilitu výpočtu. Shoda výpočtu s experimentem v případe prvního šroubového spoje je méně uspokojivá, nicméně shoda v případě druhého spoje, který má zesilující tenkou ocelovou destičku na spodní straně, je podstatně lepší. Vý-borná shoda je zejména při použití interaktivních kritérií Hill a Tsai-Wu.
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The use of Electrical Properties of Composites with Modified Cement Matrix
Macháň, Ladislav ; Husák, Miroslav (referee) ; Sýkora, Jiří (referee) ; Šteffan, Pavel (advisor)
The dissertation thesis is focused on practical use of composite material with modified cement matrix. Especially the area of electrical behavior of composite materials in use has been examined, for strain sensing material. The experimental part solves the problematics of corrosion of carbon and metallic materials in alkaline environment of the cement matrix. The physical design of the sensor and its fabrication using functional composite cement material have been described here. The thesis has also discussed defining the influence of temperature change and humidity change on the change of electrical parameters of integrated sensors. An important part of the thesis is the area of evaluating a series of measurements of electrical parameters under dynamic loading. The thesis analyzes designed measurement method in detail, being suitable to determine electrical properties of cement composite materials including the construction of a monitoring system that enables practical application of sensors in complex structures.
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Study of inorganic matrix composites for FRP
Svora, Petr ; Rovnaník, Pavel (referee) ; Puliš,, Pavel (referee) ; Šubrt,, Jan (referee) ; Bodnárová, Lenka (advisor)
During a whole period of time which fibre-reinforced polymers have been used in the building industry, in dominating bonding agent has been the organic resins. There is no doubt about their advantages, but at the same time, they have two weaknesses: they are not fire resistant and they have no resistance to high temperature. Those are the reasons why the research on alternative materials which could replace organic matrix has been undertaken. The goal of the work is to maintain mechanical properties of fibre-reinforced polymer with organic matrix. Of course, an emphasis is placed to fulfilling ecological standards which are required from ecological material. An aluminosilicate inorganic matrix can meet them all. It is non-flammable, does not produce any toxic matter in contact with fire and the energy consumption during production process is lower than in case of the organic matrix. This work includes study and analysis of selected raw materials as well as their influence and impact on final reaction products which are created in inorganic matrix. A part of this work is also a design of the inorganic matrix recipe.
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Phosphate binders
Kalina, Lukáš ; Ptáček, Petr (referee) ; Šoukal, František (advisor)
The work deals with the preparation and study of polyphosphate composites. Aluminum phosphates provide some unusual properties like high-heat resistance in terms of inorganic binders. The addition of chromium in the form of Cr2O3 or directly the bond with the aluminum-chromium-phosphate can improve the properties of this binder. Highly viscous Al2Cr(H2PO4)9 and Al3Cr(H2PO4)12 binders were prepared by dissolving Al(OH)3 and CrO3 in 85% phosphoric acid, and mixed with Al2O3 and Cr2O3 fillers. The composites were cured in the furnace at 150 °C for 24 h under pressure of 10 MPa. During the annealing at temperatures up to 1 500 °C changes in chemical structure of the cured composites were observed, leading to the understanding of the creation of crystalline phases and their eventual changes. The characterization of binders was mainly based on FT-IR, EDAX, TG-DTA and optical microscopy analyses.
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Preparation and characterization of highly filled composite materials for dental applications
Gavroňová, Ivana ; Bystřický, Zdeněk (referee) ; Poláček, Petr (advisor)
Master thesis deals with highly filled particulate composite materials for dental applications. In the practical part, the dimetacrylate matrix was filled with a mixture of particles of different types and different sizes to achieve the maximum possible packing. Moreover, filler content and the influence of filler on composite material was studied. Hydrolytic stability was also tested on composite materials. The methods used to characterize composite materials were bending test, thermogravimetric analysis (TGA), differential scanning photocalorimetry (DPC), dynamic-mechanical analysis (DMA) and scanning electron microscopy (SEM). Curing of the matrix was characterized by the degree of conversion, the heat of polymerization and the polymerization rate. Furthermore the polymerization shrinkage was measured. The glass transition temperature, the dynamic modulus at 40 °C and 100 °C, the modulus of elasticity, the strength, the critical value of the stress factor and the critical energy release rate were found in the tested samples.
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Composite materials used in the manufacture of cars
Rendek, Marek ; Juliš, Martin (referee) ; Němec, Karel (advisor)
Bachelor’s thesis deals with various types of composites used in the spheres of automotive industry. In the first section, it’s focused on the introduction to issues of composite materials, methods of production, their advantages and disadvantages. The second part of thesis focuses on specific applications in the automotive industry. In the final part there is a future evaluation and an overall view of the composite materials in the automotive field.
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Analysis of composite sandwich panel under conditions simulating placement on a rocket carrier
Král, Martin ; Horníková, Jana (referee) ; Majer, Zdeněk (advisor)
This work deals with composite sandwich panels, which are currently used as supporting structures for satellites. This type of panel contains an aluminum honeycomb core and two thin laminate coatings, reinforced with carbon fibers. Laminate sandwich panel coatings offer an alternative to conventional aluminum coatings, which is advantageous mainly due to the reduction of weight and increase of the flexural stiffness of the panels. The work is a parametric study of mechanical properties for several variants of the coating of sandwich panels. These are laminate coatings, differing in the orientation of the fibers in the individual layers, as well as an aluminum alloy coating. The study is divided into two parts. The first part examines the deformation-stress response of a sandwich panel, which is simply supported at the edges and loaded with pressure. The response calculation is performed using FEM and verified by the method of sum of an infinite series. The second part investigates the deformation-stress response of the joint, (node) of two sandwich panels, which is loaded by random vibrations, aimed at simulating the mechanical environment of the rocket carrier during the takeoff of the launch vehicle. The response is calculated using FEM and verified by an experiment on a vibrating stool for a selected variant of the laminate coating of sandwich panels. The results of the work can be used for the design of baffle of the X-ray imaging device (SXI), which is part of the equipment of the space satellite of the SMILE project.
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