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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.
51

Studium deformačních procesů perspektivních kompozitů na bázi hořčíku / Study of deformation processes of perspective magnesium-based composites

Farkas, Gergely January 2013 (has links)
The goal of the present work is investigation of deformation mechanisms in magnesium-based metal matrix composites and examination of the influence of morphology of strengthening phase on the mechanical properties. The microstructure of the specimen was studied by means of light optical and electron microscopy (SEM). Compression tests in the temperature range of 20řC-300řC were preformed. Acoustic emission measurements were performed during compression test at room temperature, whose help us elucidate the ongoing micromechanisms during the straining. Furthermore residual stress in the magnesium matrix at different strain levels was measured by neutron diffraction.
52

Studium vzájemné interakce trhlin šířících se v částicovém kompozitu s křehkou matricí za podmínek subkritického růstu / Mutual interaction of multiple cracks growing in the particulate composite with brittle matrix under conditions of sub-critical crack growth

Slávik, Ondrej January 2017 (has links)
In the first part of the submitted diploma thesis, the knowledge in the sphere of the fracture mechanics, related to the practice part of this thesis are summarized. In that the 2D parametrical numerical model of the particle composite with multiple cracks was created, using the finite elements method. Thanks to this model it is possible to find specific configurations which are showing the existance of multiple mutual interactions between these cracks, just by simple manipulation of the input data. In the calculations the influence of the residual stresses was considered which are formed during production of the material. The effect of the subcritical crack growth was taken into account as well in this thesis.
53

Polymerní kompozity s řízenou mezifází / Polymer composites with controlled interphase

Zvonek, Milan January 2018 (has links)
Cieľom diplomovej práce je príprava polymerných kompozitov vyztužených sklenenými vláknami s riadenou medzifázou za použitia metódy plazmochemickej depozície z plynnej fáze a monomeru tetravinylsilanu. Teoretická časť je zameraná na literárnu rešerš o plazme, plazmovej polymerácií, tenkých vrstvách a kompozitoch. Experimentálna časť popisuje použité materiály a aparaturu použitú na povrchovú modifikáciu sklenených vlákien a prípravu vláknom vyztužených kompozitov. Povrchová úprava sklenených vlákien prebiehala za rôznych depozičných podmienok. Chemické a mechanické analýzy vytvorenej medzivrstvy prebiehali za použitia FTIR spektrometrie a vrypového testu. Vliv povrchovej úpravy bol zistený pomocou získanej interlaminárnej šmykovej sily použítím testu krátkych trámečkov.
54

Využití čedičových vláken v alkalicky aktivovaných materiálech / Utilization of basalt fibers in alkali activated materials

Hrubý, Petr January 2018 (has links)
Alkali activated materials (AAMs) represent construction materials with a huge potential especially because of environmental and economic aspects but sufficient mechanical properties as well. A fibre or fabric reinforcement of the AAMs could support more widespread application potential due to the mechanical properties, fracture toughness or composite durability improvement. Various alkaline activators were used for a blast furnace slag (BFS) activation to produce a suitable matrix for basalt fibres (BF) implementation in this thesis. The BFs represent applicable reinforcing material because of its favourable mechanical and thermal properties. Still, the utilization of BFs in the AAMs is quite limited due to the fibres low chemical stability under the alkaline conditions. Accelerated leaching tests with a determination of basalt fibres chemical composition same as tensile strength change using various analytical techniques (XRD, XPS, SEM-EDX, ICP-OES) have confirmed these assumptions. An influence of basalt fabric reinforcement in one or more layers on the mechanical properties was determined with the meaning of the compressive and flexural strengths. The fibre/matrix adhesion and transition zone properties were studied using SEM-EDX and pull-out tests as well because they are crucial parameters for the composite material reinforcement efficiency.
55

Vliv parametrů MuCell technologie na mechanické vlastnosti polymerů pro vstřikování / Influence of the MuCell technology parameters on the mechanical properties of polymers for injection moulding

Suchánek, Matěj January 2018 (has links)
This master’s thesis deals with influence of gas content in structure of polymer materials to mechanical properties. Test specimens were prepared by MuCell technology from polyphthalamide reinforced by 50 % of glass fiber content. The theorethical part of this thesis is focused on polymer materials with attention to polyamides and injection moulding technology. In the experimental part, the dependence between the characteristics obtained from the tensile test and the Charpy impact test on the amount of gas in the polymer is examined.
56

Částicové kompozity v konstrukčních detailech obvodových plášťů / Particle Polymer Composite in structural details of the building envelope

Dostálová, Darina Unknown Date (has links)
Due to a European energy concept for reducing energy consumption and also the concept of sustainable development, there is a growing demand for reduced energy consumption during the operation of the building and hence increasing demands on the thermal and mechanical properties of the building envelope. For this reason, it is necessary to look for materials that could meet both thermal and mechanical properties, as well as mechanical resistance and loadability, especially for the application for the foundations of the house, the base of the house and for application to structural details for elimination of the thermal bridges between interior and exterior boundaries. The main motivation for choosing the topic of thesis was to find materials derived from recycled or secondary raw materials that would be suitable for manufacturing composite applicable for structural details in the envelope of the building and for insulating in humid environment. An economic and environmental aspect plays an important role in the choice of material. The main theme of the thesis is the laboratory manufacturing of a composite with a thermoplastic matrix derived from recycled plastic materials and waste foam as a phase. Has been developed a unique Waste-based Particle Polymer Composite (WPPC) made from recycled foam and polypropylene. However, before WPPC can be reliably used by construction designers, physical properties of WPPC must be accurately identified. Therefore, it was designed laboratory manufacturing system and sample testing system, it was studied thermal, mechanical, thermomechanical and moisture absorptivity of WPPC. Application of finished composite material with satisfying thermal insulation properties to structural details to eliminate the thermal bridge, was the next step. These are details of the unloaded, prefabricated balconies, windows, atics, as well as basement constructions and the heel of the central load-bearing wall, the terrain flooring and the staircase wall
57

Balisticky odolné betony / Ballistic-Proof Concretes

Koutný, Ondřej January 2019 (has links)
Doctoral thesis „Ballistic-proof concretes“ deals with description, design and development of material based on ultra-high performance fibre reinforced cementitious composite with increased ballistic resistance i.e. increased resistance against high-strain rate dynamic loading induced by interaction of high-velocity moving objects. High mechanical properties, essential for such a material, are reached especially by maximal reduction of water-to-binder coefficient using high-range water reducing agents, high-strength aggregates and dense structure by precise selection and dosage of raw materials in the recipe. The main goal is to prepare a methodology for design of such a materials, observation of material behaviour on ballistic loading and quantitative description of material response for protective structures design. Properties of designed materials within this thesis are comparing with properties of commercially available and commonly used cementitious composites in order to create a concept for material limits in the field of ballistic protection. This concept enables to estimate ballistic protection of present or newly-designed materials and structures.
58

Cílená příprava kompozitu na bázi PP + anorganické mikro resp. nano anorganické plnivo s různou adhezní mezivrstvou. / Targeted Preparation of Composite Based on PP with Inorganic Micro-, or Nanofiller with Different Adhesive Interlayer

Dombková, Julie January 2012 (has links)
The diploma thesis studies composite of PP and filler particle. As a particle filler was used commercially available CaCO3 (SOCAL 31). The submitted thesis had a goal to find new approaches and technologies of filler surface treatment in order to improve properties of composite materials. The plasma discharge behind static pressure was used for the surface treatment of the fillers. These fillers were afterwards analyzed by using of sedimentation analysis, turbidimetry, infra-red spectroscopy (FT-IR), X-ray diffraction analysis (XRD), scan electron microscopy (SEM), transmission electron microscopy and particle size distribution by laser diffraction. The composites with various volume parts of the fillers were prepared in PIB and studied by short-time tests. Furthermore, the influence of an adhesive layer on fracture mechanical properties of prepared composite was study. Regarding to experimental demand, there was not possible to realize long-term mechanical properties.
59

Vliv fyzikální úpravy sráženého CaCO3 na vlastnosti kompozitu na bázi PP / Influence of physical treatment of precipitated CaCO3 on the properties of PP composites

Huczala, Vít January 2014 (has links)
The diploma thesis deals with study of system of polypropylene and inorganic filler. As filler was used commercially available particulate filler CaCO3 termed NPCC 201. The objective of the study was a surface plasma treatment of filler in order to obtain composite based on polypropylene. Mechanical properties of this composite will show significantly greater value than basic matrix. The filler was treated in dielectric barrier plasma discharge by atmospheric pressure. The characterization of filler was performed before and after plasma treatment by x-ray photoelectron spectroscopy (XPS), electron microscope (SEM) and sedimentation analysis. The distribution of particle size was measured by laser diffraction and by dynamic light scattering. The composite materials with various weight concentration of filler were prepared in POLYMER INSTITUTE BRNO by using the twin-screw extruder and the test specimens were prepared by the injection molding technology. Their mechanical properties was studied by using of short and long-term tests. The uniaxial creep testing in tension was used for study of long-term behavior of composites.
60

Příprava MDF kompozitů se zvýšenou odolností proti vlhkosti / Preparation of MDF composites of increased moisture resistance

Žůrová, Marcela January 2015 (has links)
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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