Influence of Veneer Density on Plywood Thickness and Some Mechanical Properties

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.

Interrelations of Wood Physical and Mechanical Properties and Patterns of Their Change within the Birch Stem

The physical and mechanical properties of standing wood are not constant along the tree height and diameter. They also differ depending on the tree species and conditions of its growth. So, the research purpose is to identify patterns of change and interrelations between the parameters of density, compressive strength and sound propagation velocity along the wood fibers inside the stem of a birch tree growing in the forests of the Middle Volga region of Russia, where such research had never been conducted before. The work was carried out on two sampling areas laid out by standard methods in birch forests of natural origin with average productive capacity on the territory of the Scientific-Experimental Forest District of the Volga State University of Technology in the Mari El Republic. The average age of the birch trees is about 70 yrs, breast height diameter is 30 cm, and height is 28.5 m; 14 sample trees were studied; 0.5 m long chucks were cut out from their stems at a height of 1.3 m from the butt end and at relative heights of 0.25H, 0.5H, and 0.75H. Experimental work was carried out in a laboratory environment with modern technical facilities using standard procedures. Mathematical models describing the changes in the parameters stated above and the interrelations between them with regard to the stem diameter at relative heights were obtained. The research results generally confirmed the findings of other researchers on densitograms and other physical and mechanical properties of wood within the tree stem. However, the features listed above were revealed for birch trees growing under such conditions; in particular, it concerns the ratio of strength and density, as well as the wood strength and the velocity of sound propagation through the fibers. The results obtained have both scientific and practical value as a basis for the development of a non-destructive method for predicting technical properties of standing wood as well as timber for producing assortments for special purposes. For citation: Fedyukov V.I., Chernov V.Yu., Chernova M.S., Tsoy O.V. Interrelations of Wood Physical and Mechanical Properties and Patterns of Their Change within the Birch Stem. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 6, pp. 150–159. DOI: 10.37482/0536-1036-2021-6-150-159

Effect of Perforation Volume on Acoustic Absorption of the 3D Printed Micro-Perforated Panels made of Polylactic Acid reinforced with Wood Fibers

In recent times, Additive Manufacturing (AM) has been applied rapidly in almost all fields. This study was conducted to apply the additive manufacturing into an acoustic application by 3D printing the Micro-Perforated Panels (MPP) through Fused Deposition Modelling (FDM) made of Polylactic Acid (PLA) reinforced with wood fibers. MPP were fabricated by altering its perforation volume. Later, the effect of perforation volume on acoustic absorption of the fabricated MPP was measured using the two-microphone impedance tube method as per ISO 10534-2 standard. The result shows altering the perforation volume affects the acoustic absorption of the MPP. MPP with a thickness of 2 mm and a perforation diameter of 0.2 mm shows the maximum sound absorption coefficient of 0.93 at 2173 Hz. It is made possible to absorb the 3D printed MPP made of natural fiber reinforced composite at different spectrums by altering the perforation volume.

Adsorption properties and mechanism of uranium by three biomass materials

Wood fibers, bamboo fibers and rice husk were applied to the adsorption of uranium from aqueous solution to understand the uranium adsorption behavior and mechanism by these natural sorbents. The effects of time, adsorbent particle size, pH, adsorbent dosage, temperature and initial concentration were studied using batch technique. The adsorption mechanism was discussed by isothermal adsorption models, adsorption kinetic models. The results suggested that the three biomass adsorbents showed great efficiency of adsorption for uranium. The adsorption capacity of biosorbents of comparatively small particle size and large dosage is quite high. Uranium adsorption achieved a maximum adsorption amount at around pH 3 for wood fibers and bamboo fibers, and around pH 5 for rice husk. All isotherms fitted well to the Langmuir Freundlich and D-R equation, indicating that the adsorption process is favorable and dominated by ion exchange. Rice husk had a highest adsorption capacity, followed by bamboo fibers, while wood fibers had little uranium adsorption under the studied conditions, and the adsorption capacity was 12.22, 11.27 and 11.04 mg/g, respectively. The equilibrium data was well represented by the pseudo-second-order kinetics, indicating that the adsorption rate was controlled by chemical adsorption. Ion exchange was the main adsorption mechanism, and the exchange ions were mainly Na+ and K+.

SHORT NOTES: APPLICATION OF MINERAL FILLER IN MEDIUM DENSITY FIBERBOARD (MDF) AND ITS EFFECT ON MATERIAL PROPERTIES AS A FUNCTION OF PARTICLE SIZE

The addition of inorganic filler material in medium density fiberboard (MDF) and the effect on material properties as a function of particle size was examined. Medium density fiberboard was manufactured in a laboratory scale environment to a target raw densityof 750 kgm-3. Wood fibers were replaced by using calcium carbonate at 3 and 10 wt.% using fillers with weighted median particle sizes of d50= 2.0 μm and d50= 30 μm, respectively. Urea formaldehyde resin was used as binder in all MDF. The influence of filler addition on the modulus of elasticity, bending and tensile strength, dimensional stability and liquid permeability was investigated. The results demonstrate the effect of filler content and its dependence on particle size. The addition of filler with d50= 30 μm does not have any influence on material properties up to a filler content of 10 wt.%. Using the finer filler with d50= 2.0 μm at 10 wt.% filler, the quantity significantly increases the water adsorption and swelling behavior and reduces the strength properties of the MDF.

Morphological properties of peroxidic pulp from hemp bonfire

The bonfire (Cannabis sativa) was delignified with the reaction mixture “acetic acid - hydrogen peroxide - sulfuric acid catalyst - water” at a sulfuric acid concentration of 0.45%, a liquid module of 6, and a temperature of 85 °C. The effect of cooking conditions (hydrogen peroxide concentration and process duration) and mass grinding up to 34 … 36 °SR on the morphological properties of technical cellulose fibers - length, width, degree of inhomogeneity (polydispersity) - has been studied. Hemp fibers are inferior in length to those of spruce wood and wheat straw, but more uniform. The widths of hemp and wood fibers are almost the same. Due to its high strength characteristics, peroxide cellulose from bonfire is suitable for use in composition with other fibrous semi-finished products in the production of mass types of paper and cardboard products.

Wood fiber-reinforced polylactic acid sheets enabled by papermaking

Polylactic acid is a biodegradable thermoplastic polyester derived from renewable polysaccharides. In this work, softwood fibers were used to reinforce the paper sheet made from polylactic acid fibers, thus addressing the challenges regarding low density, rough surface, and weak strength. The impact of wood fibers and calendering on the physical properties (density, roughness, tensile strength, and folding endurance) of the composite paper were identified. Furthermore, the morphology of papers with different fiber contents and those that had been calendered was characterized with a scanning electron microscope. The use of wood fibers resulted in the improvement of the physical properties of the polylactic acid paper, and the enhanced refining of wood fibers had a favorable role in improving paper density, smoothness, and mechanical strength. The tensile index increased 37.9% when the beating degree of wood fibers increased from 25 to 60 °SR. After calendering, the density, smoothness, tensile strength, folding endurance, and air barrier property of the paper were improved 60.2%, 45.8%, 15.5%, 148.1%, and 79.4%, respectively. The calendering-based papermaking process involving the combined use of wood fibers and polylactic acid fibers would be a promising strategy for designing composite materials for tailorable end-uses.