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영어

The study points to the effect of thermal modification on beech wood at various structure levels. Three temperature levels at temperatures of 160, 180, and 200 ° C were chosen. The duration of treatment was 1,5 and 3 hours, respectively. Selected properties were observed. At the nano-scale level, the DMT modulus of elasticity and adhesion were obtained using the atomic force microscope. Density and dynamic modulus of elasticity, strength, and modulus of elasticity were determined in clear wood loaded in compression and tension parallel to the grain, bending, and torsion. Structural-size timber treated at 190 °C for 3,5 hours was tested in bending according to EN 408. AFM showed that the structure of cell wall layers did not change after heat treatment. An increase in the DMT modulus of the compound middle lamella was observed after heat treatment. The adhesion of cell wall layers was not affected by thermal treatment. Density changes without practical implications. The dynamic modulus of elasticity given by the acoustic method was a good indicator for clear wood sorting before thermal treatment. Compression strength increased. Bending strength, tension strength, and torsion strength decreased in ascending order. A decrease of 20 % was observed in the average bending strength of structural wood. The 5th percentile of bending strength decreased 66 % from 58.9 MPa to 15,63 MPa. Interestingly, the 95th percentile of treated beech wood increased by 14 %, showing high-quality boards acting oppositely. Thermally treated wood behaves differently at each scale level depending on the type of loading mode. It is unique material compared to untreated wood and knowledge about its properties is essential for its utilization and design of biomimetic mechanisms into new wood products.