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Pevnost vybraných konstrukčních spojů s použitím modifikovaného dřeva buku
Valíčková, Lenka
The thesis focuses on the influence of selected European beech wood modifications (Fagus sylvatica L.), i.e. acetylation and thermal modification at 200 °C and 220 °C, on the strength of structural joints used in the furniture industry. Based on the literature research, three types of structural joints were selected, which were subsequently tested. The strength of the glued joint was tested according to ČSN EN 205, withdrawal capacity of a screw according to ČSN 49 0135 and the corner screw joint. The results of the measurements were statistically evaluated using a one-way ANOVA and the measured groups were compared to each other. The results demonstrate that all types of modification lead to a decrease in mechanical strength. Wood acetylation lead to a statistically significant differences in the values for the glued joint. The thermal modification at 200 °C achieved statistically significant differences in the withdrawal capacity of a screw. The biggest drop in values came after a thermal modification at 220 °C, which were statistically significantly different when testing all selected joints. In the case of acetylation and heat modification up to 200 °C, it is not possible to unequivocally identify a method that showed significantly better results across all tests. Both metods of modyfying wood showed possibilities of use in furniture design. However, a decrease in the mechanical properties ofthe modifies material muse be taken into account when determining the dimensions of the structure.
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Rozměrová stabilizace lisovaných dřevěných dílců
Karásek, Lukáš
This diploma thesis deals with wood plasticization using microwave (MW) radiation for wood densification purposes. In this work, the literary sources of the investigated issue were summarized. The experiment was carried out on test samples of white poplar (Populus alba) with dimensions of 190 x 40 x 30 mm. Microwave plasticization was carried out by passing through a microwave laboratory line at a power of 1.5 kW and a conveyor speed of 0.1 m/min. After plasticization, the test samples were compacted in compression molds by a press by 50%. The compacted test samples were stabilized in compression molds at a temperature of 103°C for 7 days. Using heat modification at 180°C and 200°C improved moisture resistance and reduced swelling. The samples were subjected to density profile analysis to evaluate the plasticization quality.
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Stanovení koeficientů tepelné vodivosti modifikovaného dřeva buku
Stárek, Šimon
The bachelor thesis is dedicated to the influence of selected wood modifications on its thermal properties. For the experimental part of the work, European beech wood (Fagus sylvatica L.) was used, which was modified by acetylation (using acetic anhydride) and thermal modification at temperatures of 200 and 220 ˚C. Values of thermal conductivity coefficient, specific heat capacity, and thermal diffusivity were measured using the Thermophysical Tester RTB device. The obtained data were statistically evaluated and compared with available literature. Compared to control samples, a decrease in thermal conductivity of approximately 3 % was observed in samples thermally modified at 200 ˚C. Samples thermally modified at 220 ˚C showed much significant decrease in thermal conductivity, that being over 15 %, due to a more pronounced decrease in the density of the modified wood. Despite the fact that the density of acetylated samples increased, very similar results were achieved. This decrease in thermal conductivity was mainly caused by the different thermal properties of the chemical used for impregnation process. Modified wood with these thermal properties can find applications in the construction industry, where the priority is to achieve the best possible energy efficiency of components made of wood.
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Vliv tepelné a chemické modifikace na sorpční, difuzní a hygroexpazní vlastnosti dřeva
Imramovský, Pavel
This thesis dealed with the influence of heat and chemical modification on sorption, diffusion and hygroexpansion properties of wood. To this aim, a thermal modification of European beechwood was carried out at temperatures (180 °C, 200 °C, 220 °C) in the special modified chamber of Katres. Furthermore, chemical modification was required on individual samples using acetic acid anhydride. The individual samples had to be sliced in radial and tangential directions using microtoma. A dynamic vapour sorption (DVS) device was used to determine the sorption and diffuse properties of all these beech slices as well as the reference unmodified sample. In addition, dynamic swelling was determined for all groups studied in radial and tangential directions. In order to determine the rate of swelling, sample sizes were measured using a scaler in specified directions before and after the 24-hour period in the water. The results indicated that both heat- and chemically-treated beechwood scored better against moisture than reference untreated samples. The diffusion coefficient in the radial direction was also higher than in the tangential direction, which corresponds to the professional literature. The results indicate that heat- and chemically-treated beechwood resisted better moisture than the reference untreated samples. Within swelling, direction plays a large role, as measurements in the tangential direction are nearly twice as high as the radial. The possibilities of using modified wood in construction as well as from the perspective of the researched characteristic were considered. The statistics were performed in the ANOVA program.
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