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Fracture Toughness of Composite with Al-matrix and Carbon Fibres
Michalička, Jan ; Klement, Josef (referee) ; Molliková, Eva (advisor)
Abstract The objective of this study was a values evaluation of fracture toughness of fiber-metal laminates (FML) compounded from carbon fibers in epoxy matrix and aluminium plates of lay-up 6/5. Samples with unidirectional and bidirectional orientation were tested experimentally. In the case of unidirectionally oriented samples an effect of moisture absorption to epoxy matrix on the values of fracture toughness was reviewed. A fracture toughness calculation was realized by COD method firstly. A bigger pop-ins in F – COD diagram as critical moments for "delta"c evaluation were considered; it was determined by 5% tangential line. It was found out, that results of this measurement weren’t in agreement with plane deformation condition and for this the results couldn’t be rated as fracture toughness "delta"Ic. A method of J integral for fracture toughness evaluation was used consequently. A test of elastic compliance changes before J integral calculation by all of samples was performed. Beginning of stable grow of crack was determined by this method. A critical forces Fc from beginnings were established, which were used for calculation of Jc. A functional dependence of elastic compliance on crack opening had specific waved shape before its linear (up to exponential) grow. It was observed in all cases. The critical forces Fc from the end of “wave” preceding the continual grow of compliance were determined. Equations stated in standards for J integral calculation were used, which are for metal materials normally used. Despite this was found out all of results of Jc were in good agreement with plane deformation condition and could be rated as fracture toughness JIc. In this study were found out these pieces of knowledge about fracture toughness of FML CARE: Unidirectional CARE had fracture toughness JIc about 76 kJ/m^2 and the same type but with bigger amount of absorbed moisture had JIc about 4 % higher. In this case negative moisture influences on CARE weren’t found. Bidirectional CARE had fracture toughness JIc about 31 kJ/m^2; it was about 65 % less then in the case of unidirectional CARE
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Torrefaction of biomass for energy use
Sverkunová, Kristina ; Ivanova, Tatiana (advisor) ; Krepl, Vladimír (referee)
The Bachelor thesis is focused on torefaction of biomass for an energy use. It describes the technology including basic reactors, compares wet and dry torefaction and used materials that can be used for an agricultural waste. In the thesis I compared advantages and disadvantages of torefaction considering all hydrophobic, grindability and emission of greenhouse gasses.
Second and the important part of the thesis is the recent commercial use of biomass. Data are mainly taken from the SECTOR study, which was made in March 2016. So it can be considered as a recent data. This part is also concentrated on possibilities of faster development of this technology thanks to the commercial use. It is also explaining the importance of norms, which have not been regulated yet.
The conclusion refers to the main assets of this technology, when the usage of fossil fuels and its more ecological substitutes are discussed. I mentioned the problem of a carbon footprint is connected to a possible raise of wood materials import, that will be unavoidable in order to satisfy expected demand for year 2020.
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Comparison of organic carbon stocks in soils with different land use
Rašková, Renáta ; Borůvka, Luboš (advisor) ; Tomáš, Tomáš (referee)
The aim of this thesis was to determine and compare the carbon stocks in selected locations.
Three localities were selected in Vyškov region. In each locality four types of soil according to their use were examined - forest, arable land, grass land and urban soil. From each type of soil four samples were taken which were located 10 meters from each other. Samples were taken by soil auger from 0 to 40 cm depth in November 2015. All samples were dried, ground and sieved. Consequently humus content was determined in samples by the Tyurin method. From these results content and stocks of organic carbon were calculated in each locality and each type of land use and all results were compared with each other.
Contribution of this thesis was to confirm or disprove hypothesis and to provide helpful information on Vyškov region.
Hypothesis: The stock of carbon in forest soil is higher than in arable land. The stock of carbon in arable land is higher than in urban soils.
The highest content of SOC was in forest soils and the highest stock of organic carbon was in arable land. Results show that the stock of carbon in soil is affected by land use and also by the way of management.
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