Wood Fiber Direction Research Articles

REVIEW OF DYNAMIC PROPERTIES OF WOOD

This review considers the state of the art in the field of theoretical and experimental studies of dynamic deformation and destruction of wood materials. The orthogonal properties of wood, features of early and late wood are considered, the dynamic properties of wood are analyzed, as well as the influence of the strain rate during dynamic compression. It is noted that wood of different species is mainly used as one of the materials that dampen dynamic loads as a result of impacts or explosions. For example, it can mitigate the effects of high-velocity impacts on the contents of containers during the transport of hazardous materials by air, road and rail. It has been established that the cause of the effects of internal friction in wood are the areas of lignin, in which bundles of cellulose molecules (microfibrils) with a diameter of 25-30 nm are immersed, which are crystalline in their structure, which leads to viscoelastic behavior - internal damping. To improve the damping properties, it is recommended to choose wood with a low microfibril angle. It is noted that the stress-strain curve under dynamic compression of wood consists of three separate parts: the initial elastic region, the yield region and the compaction region. The main characteristics of compression, that is, the components of the stress-strain curve and the destruction of the fibers, do not depend on temperature. Young's modulus is much larger in the longitudinal direction than in the radial and tangential directions. The rate of deformation, temperature and humidity have a great influence on the strength properties of wood. The features of the mechanical behavior of the zones of early and late wood in the massif of a tree trunk are considered. Late wood is more rigid than early wood. As a result, differences in the mechanical properties of the wood fibers during compression may cause the early wood fibers to be destroyed while the late wood fibers remain intact. Due to the complexity of the wood structure, its reliable description by a numerical model requires complex models that take into account not only the influence of temperature, strain rate, and the type of stress-strain state, but also the angle between the direction of loading and the direction of wood fibers. Two main groups of wood material models are considered: micromechanical models simulating the details of the wood structure, and continuum models simulating the behavior of wood as a whole.

Potential Use of Transparent Wood in Spatial Folded Structures

Transparent wood is a relatively new material, the manufacturing starts with removing the lignin from wood veneer and infiltrating the delignified wood by a polymer thereafter. Transparent wood usually proves better mechanical properties than original wood and polymer. The article presents the potential use of transparent wood in bearing structures. The transparent wood could be used as I-beams structures, box beams, trusses, or folded structures. A spatial folded structure was numerically analyzed. Various types of transparent wood or transparent plywood were used. A comparison with commonly used materials, such as glass and other wood-based materials were made. The comparison shows that transparent wood has great potential in the use as a structural material. The plywood made from transparent wood veneer with the alternating direction of wood fibers acts as a laminate and allows a biaxial load transfer, which can be successfully used in a thin plate of the spatial folded structure while maintaining relatively good transparency.

Gloss of Varnished MDF Panels Veneered with Sanded and Thermally Compressed Veneer

The objective of this study was to investigate the gloss of different types of commercially manufactured varnish systems, including water-based (WB), polyurethane (PUR) and UV-cured (UV), applied on veneered MDF panels with sanded and thermally densified alder and birch wood veneers. The varnishes were applied at various numbers of layers on veneered panels. The gloss was measured at three angles of incident light: 20°, 60° and 85°. Statistical analysis showed that the type of varnish, the number of layers, the pre-treatment process, the wood species and direction of wood fibers significantly affect gloss of the coatings of veneered MDF panels. The type of varnish had a dominant effect on gloss. The highest gloss values were measured for the UV-varnished surface, and the lowest for WB- and PUR-varnished surfaces. Gloss was enhanced with an increase in the number of layers. Birch veneer provided higher gloss values compared to alder veneer. The gloss values measured along the wood fibers were higher than those measured across the fibers. No significant differences were found between the coatings created on sanded and thermally densified veneers for the average gloss values measured along the fibers at angles 60° and 85°. This study could have practical applications for producing value-added furniture elements using low-value wood species pre-treated by thermal compression.

Influence of Veneer Density on Plywood Thickness and Some Mechanical Properties

Abstract It has been common knowledge that as the density of wood increases, the mechanical properties also improve. In turn, the density of wood depends on many factors, including the wood moisture content, location and cross-section in the trunk, the type of treatment and the parameters of technological processes. There is a great deal of research reported in the scientific literature on the effect of solid wood density on mechanical properties for different wood species as well as for structural timber. However, no research data can be found related investigation of the influence of veneer density on the properties of the birch plywood. In the present study, researching the properties of 7-ply birch plywood (thickness 9 mm), it was concluded that as the density of veneers increases, the bending properties of plywood in the direction of wood fibers (covered veneers) increases. When determining the plywood gluing quality, similar tendencies have been observed. For plywood with a lower density in all veneer plies the gluing quality (tensile-shear test) for perpendicular wood fiber veneers increases in the direction from the symmetry axis or middle veneer to the plywood outer plies, which can be explained by the fact that the outer plies become denser at the time of the hot pressing process. The results of the study will allow birch plywood manufacturers in direct production, sort veneers by density, to produce plywood with very predictable gluing quality, plywood thickness and mechanical properties in bending.

Hardened wood as a renewable alternative to steel and plastic

Hardened wood as a renewable alternative to steel and plastic

Adaptive milling of solid wood furniture workpieces: analysis of the extended approach capabilities

An extended approach to improve adaptive milling of solid wood workpieces is described. It is based on the joint usage of two physically different methods: non-contact ultrasonic scanning of the workpiece body and optical recognition of the wood fibers direction on the workpiece surface. To implement the proposed approach, it is necessary to change the existing technological route of furniture workpieces processing. A stage before the milling operation should be included. This stage involves the sequential execution of ultrasonic scanning, computer processing, and optical recognition of the obtained data. It allows us to determine the wood density, the internal defects localization, and the direction of wood fibers. Computer processing involves the usage of a virtual orthogonal grid. This grid covers the workpiece surface, on which the trajectory of the milling cutter is projected. The projection of the milling path is represented by the set of cells. It defines the local processing area. The gathered information about the wood properties is suggested to use for the adaptive selection of the important equipment technological parameters, such as the feed rate and the cutter rotation frequency. Varying of these parameters values and considering the physicomechanical properties of wood at the processing area allow us to improve the milling quality.

Research of stability of geometric parameters of wood under the moisture action

The object of research is a promising structural material – modified wood. Extending the use of wood while maintaining structural characteristics is a promising area of research. Modification of wood in accordance with structural requirements, taking into account sanitary and other requirements, is an important task. The most common modification technologies are impregnation. Pressure autoclaving wood requires sophisticated equipment to create unprofitable pressure. Impregnation by the condensation method or the method of «cold and hot baths» significantly reduces the cost of obtaining modified wood. The study of the stability of the geometric dimensions of modified wood under the moisture influence makes it possible to evaluate the effectiveness of the modification (impregnation) process and, as a result, evaluate the service life. Samples from pine timber (DSTU ISO 738:2018) with a size of 300–70–15 mm are used. For research, three groups of samples are selected with radial (R), tangential (T) and mixed (M) direction of wood fibers. For impregnation modification, linseed oil and drying oil were used at a concentration of 25 g/l. In accordance with the modification technology, the samples are soaked in an aqueous solution with a desiccant, then immersed in linseed oil heated to 130±10 °С, and then immersed in linseed oil at a temperature of 20 °С. The obtained samples are dried under atmospheric conditions and soaked in water for 24 hours to study the stability of geometric dimensions. As a result of studies, it is found that the optimal temperature for heating the samples is the range 120–140 °C. It is also found that the most resistant to changes in geometric dimensions are samples with a mixed direction of the fibers (M), in which size changes are 0.5 % compared to dry samples. Regardless of the direction of the fibers, the moisture absorption of the modified samples is 0.07 vol. %, which is of great practical interest.

Simultaneous detection of density, moisture content and fiber direction of wood by THz time-domain spectroscopy

In the wood product-manufacturing process, the physical properties of wood must be monitored. The terahertz (THz) radiation has a high potential for sensing and imaging wood with a good spatial resolution. This study demonstrates the simultaneous prediction of the density, moisture content, and fiber direction of wood, which are important in determining the wood quality, using THz time-domain spectroscopy. We measured the spectra of 12 kinds of wood at various moisture contents while rotating the sample against the THz wave polarization. The fiber direction was predicted by observing the birefringence, which is the optical property of a material, in which the refractive index depends on the polarization direction. The density and the moisture content were predicted by multiple linear regression using the refractive indices and absorption coefficients obtained from the THz measurement. In a series of THz measurements, we successfully identified the wood fiber direction with an R2 of 0.90 and a root mean square error (RMSE) of 16.51° (total measured range = 0–170°), the density with an R2 of 0.97 and an RMSE of 0.022 (total measured range = 0.25–0.67 g/cm3), and the moisture content with an R2 of 0.78 and an RMSE of 4.06 (total measured range = 0.00–30.98%).

Dynamic Mechanical Analysis and Thermal Stability of Neem Wood Veneer Plastic Composites

The neem wood veneer is used as core materials in many of the wood structural applications. In this research work, neem wood polymer composite (NWPC) were prepared to understand the effect of weight fraction, stacking sequence, and interfacial bonding between neem wood veneer and epoxy material. NWPC were prepared conventional compression molding and Thermo-mechanical properties of wood epoxy composite samples were investigated by the dynamic mechanical analyzer over the temperature range from 30 to 180°C. Storage modulus (G’) and Loss modulus (G”) of NWPC samples exhibited significant effect with respect weight fraction of wood veneer. Similarly epoxy has good interfacial bonding agent to enhance the strength of multilayered wood polymer composites. However, the stacking sequence having major changes in dynamic mechanical properties, G’ & G” increases along the wood fiber direction with negligible load bearing capacity in transfers direction. By changing the orientation of the wood veneer properties improved in both the direction. Additionally, scanning electron microscopy (SEM) evidently shows the interfacial bonding efficiency

Lignocellulosic materials modification and engineering in relation to viscoelastic perspectives

By 2010, only 52% or 94 million ha of the total land area in Indonesia was forested. Therefore, we should develop forest plantation with fast growing species, or better efficiency and quality improvement for the utilization of forest products. The conventional method of fabricating curved wooden products is to cut wooden beams into a curved wood, and to connect them for the expected curve shape. However, the disadvantages of this conventional woodworking process are wasting of wood raw materials, decreasing the wood strength due to fiber cutting, and reducing the beauty of wood fiber direction. These problems can be overcomed by bending solid wood, as well as curving laminated veneer lumber (LVL). The bending method of solid wood requires special technique and equipment compared to curving method of LVL. The development of commercial products is required to understand basic knowledge of wood bending. This paper deals with lignocellulosic materials modification and engineering in relation to viscoelastic perspectives; describing viscoelastic property of wood and other lignocellulosic materials, and development of furnitures and bicycle frames from LVL curves. It is expected that more modified and engineered products can be made from lignocellulosic materials based on the knowledge of their viscoelastic properties.

Surface gloss of lacquered medium density fibreboard panels veneered with thermally compressed birch wood

Abstract Wood surfaces are typically sanded before the lacquer coatings technological processes. This article discusses the aesthetic properties of lacquer coatings formed on medium density fibreboard (MDF) panels, veneered with thermally compressed birch wood. The effect of thermal compression temperature, veneer side (loose vs. tight), the number of lacquer layers and spread rates on the gloss unit (GU) of lacquer coatings were determined. Rotary-cut birch veneer sheets were thermally compressed at various temperatures (150, 180 and 210 °C) and afterwards they were bonded to the surfaces of MDF panels. The lacquer was applied to the surface of veneered MDF panels in 1, 2 and 3 layers at the various spread rates, appropriate 50, 75 and 100 g/m 2 . The values of GU parameter were measured at three angles − 20, 60 and 85°. Statistical evaluation of GU parameter showed, that the number of layers, the amount of lacquer, the direction of wood fibers, the side of veneer and compression temperature significantly affect gloss of the surfaces of veneered MDF panels. Gloss increased with the number of layers and the amount of applied lacquer. Brightness decreases with the increase in temperature from 150 to 180 °C, while a further increase in temperature from 180 to 210 °C enhances GU. There is a significant difference between values of gloss (except for the 20° angle) measured along and across grain direction. The values of gloss measured along the wood fibers are higher than those measured across the grains. Thermal compression of veneer homogenises the surface and as a result the gloss of the loose and tight sides is uniform. Thermal compression of birch wood surface instead of its sanding before finishing improves aesthetic properties of wood, in particular surface gloss as well as reduces the required lacquer application rate. These findings make it possible to improve the technology of lacquer coatings of thermally compressed wood.

POROVNÁNÍ VLASTNOSTÍ DŘEVA BUKU LESNÍHO Fagus sylvatica (L.) V RŮZNÉM STAVU A STUPNI DEGRADACE DŘEVOKAZNÝMI HOUBAMI

This work focus on comparison of biological degradation of wood caused by wood-decay fungi (white and brown rot). Test samples were made of European Beech Fagus sylvatica (L.). As wood-decay fungi were used Trametes versicolor (L.) Lloyd (white rot) and Serpula lacrymans (Wulf. Ex Fr.) Schroet (brown rot). Aim of this work was comparison of rate of propagation of wood-decay fungus and degradation of wood in time. After termination of the test was made comparison of intensity of degradation between both fungi species. Weights of test samples were diminishing for both groups of wood-decay fungi during three months. Moisture content increased in direct proportion with time. Compression strength in direction of wood fibers of tested samples was diminishing. Samples tested by Serpula lacrymans had the fastest decrease of compression strength after first and second week of degradation. Samples tested by Trametes versicolor had different course. Compression strength significantly decreased after first month and third month of degradation. On the other hand module of elasticity of both tested groups was diminishing already during first and second week of degradation. Generally, it is possible to say that Trametes versicolor has more significant impact on changes of mechanical characteristic of wood, because it causes degradation of all chemical constituents of wood.

A Study on the Morphology, Mechanical, and Electrical Performance of Polyaniline-modified Wood - A Semiconducting Composite Material

This study investigated the morphology, electrochemical modification with respect to the wood fiber direction, and mechanical properties of wood modified by in situ polymerization with polyaniline (PANI). This polymerization formed a composite material with applications as an anti-static, electromagnetic, anti-corrosion, and heavy metal purifying materials. The polymer was found throughout the entire structure of the wood and was quantified within the wood cell wall and middle lamella by SEM-EDX. The presence of PANI affected the conductivity of the composite specimens, which was found to be higher in the fiber direction, indicating a more intact percolation pathway of connected PANI particles in this direction. The PANI modification resulted in a small reduction of the storage modulus, the maximum strength, and the ductility of the wood, with decreases in the properties of specimens conditioned in an environment above 66% relative humidity. The in situ-polymerized PANI strongly interacted with the lignin component of the veneers, according to the decrease in the lignin glass transition temperature (Tg) noted in DMA studies.

Preparation of Wood Plastic Composite Sheets by Lateral Extrusion of Solid Woods Using their Fluidity

During the course of our studies, we have learned that solid wood has significant deformability characteristics under specific conditions, resulting from slippage occurring among wood cells when wood treated with small-molecular resins is compressed under heat. Furthermore, the deformed shapes obtained are maintained when the resin introduced into the wood cells is cured.In this study, the lateral extrusion of thin discs of wood treated with thermosetting phenol resin is performed to apply this flowlike deformation behavior of wood to wood-forming techniques. Resin-treated thin discs of wood placed in a heating container were compressed by a punch, and under constant pressure the wood flowed into the cavity of a mold. Successful molding conditions were achieved by varying the pressure, temperature and wood fiber direction for the extrusion ratio of 42. The mechanical properties of the wood plastic composite (WPC) sheets obtained by this extrusion process are affected by the fiber direction of the wood in the extrudate, which is almost equivalent to the longitudinal direction of the cellulose crystals of wood. The maximum bending strength of the WPC sheets obtained was about 180MPa, which is suitable for engineering plastics.

Correlation between charring rate and oxygen permeability for 12 different wood species

The charring rates of 12 different wood species originating from Europe and the tropics with densities ranging from 350 to 750kg/m3 were investigated to obtain clues on their fire resistance behavior. This was done by measuring the thickness of the charred layer after a 30-min exposure to the standard fire ISO 834-1. No correlation was observed between charring rate and density. In search of another physical property that could be used as an indicator of fire resistance, the oxygen permeabilities of the selected wood types were measured. A strong correlation between oxygen permeability perpendicular to the wood fiber direction and charring rate was found, which is quite straightforward given that oxygen is the necessary component to enable smoldering and ignition, both affecting the charring rate. It seems that oxygen permeability is potentially more suitable as a parameter to evaluate the fire resistance of char-sensitive wooden constructions, rather than density. No general preference of the tree ring orientation from 0° (tangential) to 45° and 90° (radial) was found for these measurements.

The influence of wood fiber direction, feed rate, and cutting width on sound intensity during routing

This study examines the possibility of using sound intensity to monitor the wood routing process at different machining conditions. Sound intensity is defined as the rate of flow of acoustic energy per unit area in a specified direction. For this study, specimens of Japanese beech (Fagus crenata Blume) were routed on a CNC machine tool equipped with an automatic feed. The effect of wood grain angle on the sound intensity energy generated and surface roughness produced was determined. Maximum sound intensity during routing was generated at an inclination of 135° to the grain. A linear relationship between sound intensity output and workpiece feed rate was recognized. Sound intensity and surface roughness are also strongly correlated, irrespective of feed rate. In contrast, sound intensity more than doubled with doubling of cutting width, whereas surface roughness did not increase. The results suggest that the measurement of sound intensity is a promising method for monitoring surface roughness and determining optimum feed rates.

Wood construction and magnetic characteristics of impregnated type magnetic wood

The results of experiments involving the AC and DC magnetic characteristics of impregnated type magnetic wood were studied by taking into consideration the wood construction and fiber direction. The experimental results show that the sufficient amount of impregnated magnetic fluid varies depending on the fiber direction and length, and the grain face of the wood material. The impregnated type magnetic wood sample that is fully impregnated by magnetic fluid has a 60% saturation magnetization compared to the saturation magnetization of magnetic fluid. Samples for which the wood fiber direction was the same as the direction of the magnetic path had a higher magnetization intensity and permeability.

木材のイメージに与える色彩および光沢の影響

In this study, the correlation between image of wood and its color was investigated by using 16 groups of specimens (printed, decorative veneer overlaid and various colored transparent paper overlaid 123 panels). To calculate the correlation factor between hue and image, a new numerization method of hue was proposed, which made it clear that hue of wood especially near 7.5YR gave “warm” image, and clolor of near 10R and 2.5YR with a low brightness value gave “gorgeous” image. Brightness had correlation with “light” and “neat and clear”, and had negative correlation with “profound”, “heavy and thick”, “sober” and “calm”. Chroma had correlation with “showy” and negative with “sober”.The influence of clear coating on image was investigated on the adjacent sliced specimens of veneer overlaid plywood (8 species) with the same figures. Clear coating gave gloss and also contrast of wood grain figure, and consequently “showy” and “gorgeous” image increased but “elegant” and “fine” image decreased. In the case of species whose brightness value decreased by coating, “calm” image increased. Anisotropy of glossiness based on wood fiber direction was observed and the anisotropy did not disappear even if the specimen was clear-coated.