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Hybrid Blends of Recycled Plastics
Černý, Miroslav ; Lehocký, Marián (referee) ; Balgová,, Vendula (referee) ; Jančář, Josef (advisor)
Work describes the relationship between structure and mechanical properties in case of hybrid mixtures. They are composed from polyurethane matrices (eventually polyurethane-urea or polyurethane-inorganic filler mixtures), different rubber fractions as filler and eventually reinforcement made from PET monofilaments. Mechanical behaviour was studied by tensile testing. Studied mechanical properties include tensile modulus, ultimate strength and strain and also specific energy need neccessary for ultimate strength achievement. Prepared materials are naturally porous. Therefore their mechanical behaviour has to be described generally for porous composites. The porosity occurence means, that it is difficult to describe them by models valid for mechanical behaviour (mainly elastic modulus) of nonporous composites. Models are also based on idealized structures on microscopic level. In case of porous composites, it is very difficult to create any idealized structure. The structure is changed with modifications of composition (change of components or their rates). These conditions have lead to utilizing of different approach how to describe the relationship between structure and mentioned mechanical properties. The chosen approach comes from knewledge about structural parametres coming from porosity. Structural parameters describe the structure on macroscopic level. They include interspace volume (volume lying between filler particles), interspace filling (how the matrix fills the interspace volume) and matrix volume fraction. Proposed parameters are used in relations, where they are fitted by exponents to interlay values of chosen mechanical properties for composites containing discrete matrix and filler. Found exponents are then described by properties of matrices to obtain relations describing properties of filled porous materials. Very similar approach was chosen for description in the case of reinforced composites. Proposed relation are potentially valid for materials containing binding matrix, infinity count of fillers and one kind of reinforcement.
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Comparison of selected parameters of tensile strength of concrete
Rozsypalová, Iva ; Žítt, Petr (referee) ; Daněk, Petr (advisor)
The thesis deals with a comparison of the selected strength tension properties of the hardened concrete and finding relationships between them. This is essentially a simple tensile strength, tensile flexural strength and tensile splitting strength. The text describe the testing procedures to determine the tensile strength of concrete. Furthermore, there are presented the results of testing on different types of concrete (plain concrete, lightweight concrete, steel-fiber concrete, polymer-fibre concrete and high strength concrete). The conclusion deals with the derivation of dependancy between concrete strengths and comparing the values obtained from the available relations with the results of the tests.
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Optimisation of fibre-matrix interface in ceramic matrix composite
Halasová, Martina ; Černý,, Martin (referee) ; Chlup, Zdeněk (advisor)
This thesis is concerned to the study of behaviour of fibre composites with ceramics matrix. The composite consists of pyrolysed polysiloxane matrix reinforced by ceramic fibre Nextel 720. Main aim of this work is optimisation of fibre matrix interface through the selection of suitable precursor of the matrix with respect to temperature stability, sufficient strength and reasonable fracture toughness. Samples of matrices were exposed to the long term heat treatment in the range 1100 – 1500 °C. The mechanical properties as hardness and indentation elastic modulus were determined after heat treatment. Selected precursors of matrices were used for composite fabrication. Elastic modulus and fracture toughness at room and elevated temperatures were studied. Discussion is dedicated to the description of changes in mechanical properties with respect to chemical processes taking place during high temperature exposition. Further, reasons of fracture behaviour of composite materials are discussed, and finally, gained knowledge and outlined possibilities of subsequent development are summarised.
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Performance tests of the recycled aggregates to roads
Karásková, Romana ; Valentin,, Jan (referee) ; Stehlík, Dušan (advisor)
The work is divided into two parts. The practical part deals with the testing properties of soils which are using in new road in Nové Město na Moravě and the testing of recycled materials which could replace this soils from road. The aim this part is to obtain values of elastic modulus which are then inserted into the computational model. In the second part of work the track road is modeled in the software which uses the Finite Element Method to calculate and respect physical properties of different materials and a load. The result of work will be studies with comparison of displacement and stress generated to using existing soils and recycled materials.
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Effect of aggregate type on lime mortar rheology
Vozák, Rastislav ; Rovnaník, Pavel (referee) ; Vyšvařil, Martin (advisor)
The subject of this bachelor thesis is examining the effect of aggregate type on lime mortar rheology. In the theoretical part, the thesis describes types of liquids and basic rheological quantities. Afterwards there are described some of the rheological behaviour models of non-Newtonian fluids. Furthermore, the theoretical part characterizes measurement of the flow, devices used for the measurement including the oscillatory measurement and its individual modes. Scientific literature was used to describe the rheology of the lime mortars and it covers the effect of different additives on the rheological behaviour. There is also characterized the effect of aggregate on the properties of lime mortars. The experimental part talks about the effect of three various kinds of aggregate on rheological prop-erties of the fresh lime mortar. The chemical composition of aggregates and their granulometry was determined. Subsequently, flow measurements were carried out and evaluated into flow curves. The yield stress, coefficient of consistency and flow index were assayed. In the oscillatory measurement there were measured complex, elastic and viscous modulus and loss factor.
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Study of influence of input parameters for the numerical modeling of the compression test
Polách, Marek ; Keršner, Zbyněk (referee) ; Lehký, David (advisor)
The thesis analyses influence of input parametres of the 3D Non Linear Cementitious 2 material model for the numerical modeling of compression test performed in ATENA 2D and ATENA 3D software. The aim is to identify parametres with considerable influence and subsequently replicate the load-deflection curve obtained from laboratory compression test by numerical modeling. The effects of selected model and material model settings are studied on three kind of models in total. As tools for analyzing the effects, deterministic and statistic sensitivity analyses were chosen. Parametres with significant influence will be highlighted and added to the group of parametres obtained from numerical modeling of three-point bending test. This will create a set of parametres of considerable influence when it comes to modeling advanced structures with different types of stresses.
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The use of the secondary aggregates to pavement
Hurtiš, Maroš ; Hrbek, Kamil (referee) ; Stehlík, Dušan (advisor)
The master thesis deals with the possibilities of using waste aggregate from main rock production to hydraulically bound mixtures, witch are used in base and sub base pavement. The theoretical part describes conditions and properties of bound mixtures, aggregates and cement. The practical part describes the process of design, mixture preparing and laboratory test carried out on them. The bound mixtures are testing in compressive strength, frost and water resistace and resilient modulus.
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The usage of the quarried aggregates to base layers of pavements
Borkesz, Michael ; Mondschein,, Petr (referee) ; Stehlík, Dušan (advisor)
The work deals with the possibilities of using fine crushed and quarried aggregate to base layers of roads. The introduction of the theoretical part explains the origin of this type of aggregate. There are also described the tests, which were used to verify the attributes and features of these mixtures and their use in cemented base layers of roads. In a brief way, the work also deals with foreign research and the possibilities that arise from it. In the practical part is then described the process of mixture preparing and laboratory tests carried out on them, the production of test specimens, load tests of these specimens and interpretation of the results. The conclusion summarizes the findings. Here are also discussed ways to apply them in practice.
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Advanced techniques in nanoindentation testing
Břečka, Jan ; Tkachenko, Serhii (referee) ; Čížek, Jan (advisor)
The aim of this thesis is to determine the suitability of using advanced indentation methods for various materials. These advanced measurement methods are described in detail and subsequently compared in terms of time complexity and accuracy of the elastic modulus and the hardness measurement. The tested materials were copper and silica. The comparison of the methods is carried out at different views and gives a general overview of advantages of these methods.
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