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This study aimed to characterize the surface quality of beech wood (Fagus sylvatica L.) cut by a CO2-laser. Boards were conditioned to a low (about 8% moisture content), 12% and a high, (about 18% moisture content). Laser cutting was performed at varying processing parameters, i.e. cutting speed, gas pressure and focal-point position. A confocal microscope was used to determine the average surface roughness perpendicular to the grain. The anatomical structures of the laser-cut surfaces were examined with scanning electron microscope. The result showed that smoother surfaces were obtained at the low moisture content when processed at a gas pressure of 21 bar. Focal-point positioning did only have an effect on the surface roughness at 12% moisture content whereas the value was substantially lower for focal-point positioned on the surface. The surfaces cut at 18% moisture content, and at a cutting speed of 3.5 m/min generated a rougher surface than cut at low moisture content and at a lower speed. Laser cutting produced a rougher surface as compared to sawn surface (circular saw). The structural integrity of the laser-cut surface was more intact when the wood was having high moisture content and processed at a high cutting speed. [ABSTRACT FROM AUTHOR]

This article deals with the effects of various parameters on the shear bond strength (SBS) of glued wood. A four-factor analysis showed that the combination of only non-densified wood pieces achieves higher shear bond strength values than densified ones. In this case, only the piece combination was a significant factor. The other factors (glue type, wood species, and number of loading cycles) had no significant effect. Although the differences were not large, a higher SBS was achieved in beech wood glued with polyvinyl acetate (PVAc) glue. Glued wood consisting of the combination of densified and non-densified pieces had slightly lower SBS values. In this case, all the factors were statistically significant. Beech wood had a more significant impact on the SBS than aspen wood. The effect of the type of glue showed an opposite trend than that in the previous variant, i.e., a higher SBS was achieved with polyurethane (PUR) glue. Wood subjected to cyclic loading had slightly higher SBS values than non-cyclically loaded wood. The degree of densification had no significant effect. Glued wood composed entirely of densified pieces showed greater SBS variation between versions. [ABSTRACT FROM AUTHOR]

This paper deals with the change of roughness of compressed beech wood. Effects of temperature, pressure, and time on the results of pressing were examined. The surface roughness of beech wood in longitudinal and transversal directions was evaluated. Roughness was described by Ra. A contact method was applied. The results show that by increasing pressure, time, or temperature, the surface roughness of beech wood decreases. The highest roughness reduction occurred at the temperature of 150 °C, pressure 4 MPa, and time 20 min. [ABSTRACT FROM AUTHOR]

The objective of this research was to determine the influence of wood species (Fagus sylvatica L. and Populus tremula L.), thickness (4, 6, 10, 18 mm), and degree of densification (0%, 10%, and 20%) on the impact bending strength (IBS) and Brinell hardness (BH) in the radial direction. Three-factor analysis of variance confirmed that the difference in IBS was significantly related to the wood species and wood thickness. Wood densification did not have a significant effect on IBS. In addition, beech wood exhibited higher IBS values than aspen wood. The IBS values increased proportionally with increasing thickness. All factors affecting Brinell hardness were statistically significant, although thickness had the smallest influence overall. The Brinell hardness values were substantially higher in beech wood than aspen wood, and in some cases were more than three times greater. On the other hand, densification exhibited a more positive effect on increasing Brinell hardness for aspen wood than beech wood. [ABSTRACT FROM AUTHOR]

This article presents an investigation of the influence of selected factors (wood species, composition, and number of loading cycles) on the shear strength of laminated veneer lumber previously affected by cyclic loading. The monitored properties were determined on samples of European beech (Fagus sylvatica L.) and Eurasian aspen (Populus tremula L.). The laminated veneer lumber consisted of a combination of densified and nondensified veneers. Wood densification of up to 30% was carried out by means of rolling. The results show that each monitored factor significantly influenced the shear strength. The results also indicate a significant decrease in glued joint shear strength with increasing number of densified veneers in the laminated veneer lumber. [ABSTRACT FROM AUTHOR]

This paper deals with an analysis of the energy efficiency of the milling of thermally modified and unmodified beech wood, taking into consideration the angular geometry of the cutting tool (milling cutter). The analysis was made using the METREL Power Q plus MI2392 device to measure the cutting power of the machine during milling with predetermined technical and technological cutter settings. The results were compared with respect to electricity savings in industrial production. The electrical power of the milling cutter, when machining thermally modified wood, was 5% less on average compared with the machining of unmodified wood under identical technological conditions. [ABSTRACT FROM AUTHOR]

The influence of selected factors, such as wood species, veneer combinations, and loading cycles, on the bending strength and modulus of elasticity of glued laminated wood was investigated after cyclic loading of 0, 1000, 3000, and 7000 cycles with European beech (Fagus sylvatica (L.)) and Eurasian aspen (Populus tremula (L.)) The laminated woods were created by a combination of densified and non-densified veneers. The 30% densification was carried out by cold rolling. All factors and their interactions had statistically significant influence on the modulus of elasticity. Similarly, the influence of all factors on bending strength was statistically significant. However, the mutual interaction of all factors had no significant effect. [ABSTRACT FROM AUTHOR]

• Addition of nanocellulose (CNF and CNC) to PVAc adhesive improved the elastic stiffness of the joints as well as the bond quality. • The addition of nanocellulose stabilized the bond line against cyclic moisture exposure and thereby improved the mechanical properties. • The bonding ability of CNF and CNC reinforced PVAc adhesives is evident from the increased proportion of wood failure. • If CNF and CNC dispersion in PVAc can be achieved without dilution of the adhesive, then the reinforcing ability of CNF and CNC can be better realized. Cellulose nanofiber (CNF) and cellulose nanocrystals (CNC) are strong bio-based materials and have great potential in a reinforcement of the polymeric matrix. This study presents the effect of nanocellulose (CNF and CNC) reinforcement of polyvinyl acetate (PVAc) adhesive. Adhesive formulations with three different concentrations (0.5%, 1%, and 2% w/w) of nanocellulose were prepared by dispersing them in water and mixing the suspension with PVAc adhesive; the other percentages are omitted due to obvious adverse effect. The reinforced adhesive was then used to glue spruce (Picea abies L) and beech (Fagus sylvatica) wood joints to determine joint stiffness and shear strength under static load. Samples were tested at 12% moisture content and after cyclic moisture exposure. Bond line morphology was studied by SEM. FTIR analysis was performed to see the molecular interaction between nanocellulose and PVAc. The addition of nanocellulose to PVAc adhesive significantly improved the elastic stiffness and shear strength of the joints. Optimum elastic stiffness and shear strength values were achieved with a 1% addition of nanocellulose. The general trends are found to be valid for various kind of CNF and CNC. [ABSTRACT FROM AUTHOR]

This paper deals with the determination of the surface quality of both thermally treated and thermally untreated wood after the plane milling process. The milled surface quality was evaluated on the basis of the arithmetical mean deviation of the assessed profile, Ra. Surface quality measurements were carried out for various milling process parameters, such as tool clearance angles of 15°, 20°, and 25°, cutting speeds of 20, 30, and 40 m/s, and feed speeds of 4, 8, and 11 m/min. A splinter with a uniform thickness of 1 mm was removed from the wood through milling. Based on the results, it can be stated that thermal treatment of wood has no statistically significant impact on roughness. The most significant impact of the monitored factors were associated with feed speed, clearance angle, and cutting speed. The lowest average roughness values were found at 20° clearance angles, a feed speed of 4 m/min, and a cutting speed of 40 m/s. Increases in cutting speed led to a decrease in average roughness, while an increase in feed speed had the opposite effect. [ABSTRACT FROM AUTHOR]

The created surface irregularities, namely roughness profile Ra, after the sawing of spruce, beech, and oak wood on a sliding mitre saw with manual saw blade feeding were studied. The created surface roughness was monitored at a cut height, e, of 50 mm using three basic modes of solid wood transversal sawing (flatwise cross-cutting at φ2=90°, flatwise edge-mitre cross-cutting, and flatwise mitre cross-cutting at φ2=45°). The monitored surface was made using a sliding mitre saw with the gradual application of saw blades with 24, 40, or 60 teeth, and special saw blade with 24 teeth and a chip limiter (CL), respectively. The saw blades used had identical angle geometries. Three levels of feed force, Fp, of 15, 20, and 25 N corresponding to a range of feed forces used by different operators were used in the experiment. The roughness of sawn surfaces was significantly influenced by cutting model, wood species, type of saw blade, and feed force. The created surface roughness values were very close to the plane milling values. [ABSTRACT FROM AUTHOR]

This paper reports the influence of densification and cyclic loading on the bending strength of laminated beech (Fagus sylvatica L.). There have been many studies dealing with the bending strength of solid or laminated wood; however, densification is much less explored with respect to its use in the production of laminated wood. Laminated beech wood was loaded using three different numbers of cycles (1000, 2000, and 3000 cycles). Bending strength values of the cyclically loaded laminated wood were compared with that of laminated wood that was not cyclically loaded. The laminated wood was formed by a combination of densified and non-densified veneers, as well as polyvinyl cholride (PVC) fabric. The results show that the laminated wood consisting of densified and non-densified veneers, eventually with PVC film included, reached higher values of bending strength in comparison with the traditional composition consisting of non-densified veneers. Densification had a strong impact on the bending strength. Laminated wood composed solely with densified veneers achieved by 17.4% higher bending strength compared to the reference. On the other hand, the number of cycles did not influence the bending strength to a meaningful extent. [ABSTRACT FROM AUTHOR]

This study examined the influence of cyclic stress on the relaxation speed for native beech wood and laminated wood. Various sample thicknesses were evaluated, and a testing method, which consisted of bending via three-point loading, was developed. The relaxation speed was measured on samples that were cyclic loaded, and the results were compared with those gathered for test samples that were not cyclically loaded. The results show that thicker materials yield a higher relaxation speed. The type of material and the number of loading cycles did not appear to have a significant effect within the measured range of values. [ABSTRACT FROM AUTHOR]

This article deals with the determination of the cyclic loading effect on the elastic modulus (Em) of beech solid and laminated wood at various thicknesses while bent in the radial direction. To identify the modulus of elasticity, a three-point static bending test was carried out. The monitored characteristics were compared for the bodies under cyclic stress vs. bodies not subject to cyclic stress. Results showed no significant effect of cyclic loading on the laminated wood elastic modulus values. Conversely, cyclic loading significantly (95% confidence interval) affects the modulus of elasticity values for solid wood. A significant impact of thickness has been observed for both types of material. The results demonstrate that the elastic modulus values decrease with increasing thickness after cyclic loading. [ABSTRACT FROM AUTHOR]

This work analyzes the influence of the composition of laminated materials based on solid and thermo-mechanically densified beech wood and the application of reinforcing elements in the form of reinforcing fibers. The paper investigates the behavior of the elastic, plastic, and total bending work and their ratios concerning the composition of the material. These characteristics are essential in determining the appropriate application of these materials in structural systems concerning the deformation energy in the elastic and plastic stress–strain areas. From the material point of view, factors such as the input thickness of beech lamellas (5 and 9 mm), the degree of densification of lamellas (references, 10%, 20%, 30%, and 40%), and the application of reinforcing fibers (carbon and glass) were observed and distinguished. There are several approaches to evaluate elastic and plastic work in bending. This paper deals with a more accurate method by integrating the curve of the force–deflection diagram. The output of the article points to a more efficient choice of beech wood modifications by densification concerning the formation of internal cracks in conjunction with the reinforcing fibers. [ABSTRACT FROM AUTHOR]

• Spruce and beech wood dovetail joints bonded with PVAc and PUR adhesive were tested. • Joint stiffness was analyzed by both, experimental and numerical methods. • Numerical model provided information on stress distribution in the joints. • Numerical and experimental results are well aligned, with exception of tension load in beech wood. This study investigates the stiffness of dovetail joints by both numerical and experimental methods. Test specimens were made of Spruce (Picea abies L) and Beech (Fagus Silvatica L) wood, which were bonded with polyurethane (PUR) and polyvinyl acetate (PVAc) adhesives into dovetail joints. To determine the mechanical behavior, the joints were loaded according to grain direction under compressive and tensile load. The results of the experiment indicated that, under compression load, beech wood bonded with polyvinyl acetate (PVAc) adhesive had maximum elastic stiffness. Based on the experimental results, a numerical model using the finite element method (FEM) was developed by the Abaqus program to predict the stiffness of dovetail joints under compressive and tensile load. For numerical analysis, the assumption was made that arm deflection was caused by a displacement in the supports. The value of deflection corresponds to the limit of linear elasticity and the value of the force reduced stresses, which was determined on the basis of deflections. A cohesive zone was developed, which shows stress behavior under compressive and tensile load. A positive correlation was found between the numerical model and experimental study. [ABSTRACT FROM AUTHOR]