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To protect against decay and fungal invasion into the wood, the micronized copper, copper carbonate particles, has been applied in the wood treatment in recent years; however, there is little information on the health risk associated with sanding micronized copper-treated lumber. In this study, wood dust from the sanding of micronized copper azole-treated lumber (MCA) was compared to sanding dust from solubilized copper azole-treated wood (CA-C) and untreated yellow pine (UYP). The test found that sanding MCA released a much higher concentration of nanoparticles than sanding CA-C and UYP, and the particles between about 0.4-2 µm from sanding MCA had the highest percentage of copper. The percentage of copper in the airborne dust from sanding CA-C had a weak dependency on particle size and was lower than that from sanding MCA. Nanoparticles were seen in the MCA PM 2.5 particles, while none were detected in the UYP or CA-C. Inductively coupled plasma mass spectrometry (ICP-MS) analysis found that the bulk lumber for MCA and CA-C had relatively equal copper content; however, the PM 2.5 particles from sanding the MCA had a higher copper concentration when compared to the PM 2.5 particles from sanding UYP or CA-C. The cellular toxicity assays show that exposure of RAW 264.7 macrophages (RAW) to MCA and CA-C wood dust suspensions did not induce cellular toxicity even at the concentration of 200 µg PM 2.5 wood dust/mL. Since the copper from the treated wood dust can leach into the wood dust supernatant, the supernatants of MCA, CA-C and UYP wood dusts were subjected to the cellular toxicity assays. The data showed that at the higher concentrations of copper (≥5 µg/ml), both MCA and CA-C supernatants induced cellular toxicity. This study suggests that sanding MCA-treated lumber releases copper nanoparticles and both the MCA and CA-C-treated lumber can release copper, which are potentially related to the observed in vitro toxicity.

This work deals with the determination of some properties of laminated veneer lumber (LVL) made from tropical hardwoods, specifically focusing on Cameroonian woods. The LVL samples are manufactured using veneer from three tropical wood species: Ayous, Ilomba, and Bete. Two types of adhesives are used: a neoprene contact adhesive (Magpow) and a white vinyl adhesive (Nemo). The specimens have undergone multiple drying cycles, and hundreds of samples from each species have been selected with dimensions of 1 cm × 1 cm × 1 cm. These samples are then machined according to the specific wood grain of each species. The experiments conducted aim to determine properties such as moisture content, densities, volume swelling, shrinkage coefficients, and the hygroscopic point of equilibrium of the samples. Swelling and shrinkage measurements allow for the visualization of sample dimensions in relation to humidity levels, and the hysteresis of the adsorption phenomenon of the LVL is also obtained. The results show that regardless of the type of adhesive or veneer used, LVLs are denser than the wood they are made from. For each type of LVL, the ratio between the mass of a sample saturated in water and the mass of the dried sample remains constant. The rule of mixture is investigated, and the density properties of materials and the vacuum rates of LVL samples are compared with experimental data. [ABSTRACT FROM AUTHOR]

Among the many benefits of implementing numerical analysis on real objects, economic and environmental considerations are likely the most important ones. Nonetheless, it is also crucial to constrain the duration and space necessary for conducting experimental investigations. Although these benefits are clear, the applicability of such models must be appropriately verified. This research subjected validation of numerical models depicting the behavior of unstrengthened and strengthened laminated veneer lumber (LVL) beams. As a reinforcement, a carbon fiber reinforced polymer (CFRP) sheet and laminates were used. Experiments were conducted on full-scale members within the framework of the so-called four-point bending testing method. Numerical simulations were performed using the Abaqus software. Two types of material models were examined for laminated veneer lumber: linearly elastic and linearly elastic–perfectly plastic with Hill's yield criterion. A distinction was made in the material properties of carbon composites based on their location on the height of the cross-section. The outlined numerical models accurately depict the behavior of real structural elements. The precision of predicting load-bearing capacity amounts to a few percent for strengthened beams and a maximum of eleven percent for unstrengthened beams. The relative deviation between numerical and experimental values of bending stiffness was at a maximum of seven percent. Applying the elastic–plastic model enables accurate representation of the load versus deflection relation and the distribution of stress and deformation of strengthened beams. Based on the findings, directives were provided for further optimization of the positioning of composite reinforcement along the span of the beam. Reinforcement design of existing laminated veneer lumber members can be made using presented methodology. [ABSTRACT FROM AUTHOR]

Deformation and surface-checking defects in wood are closely related to the drying stress caused by shrinkage and moisture content (MC) gradients throughout the drying process. In this study, 50-mm-thick Masson pine (Pinus massoniana Lamb.) lumber was used as the research object. The drying stress caused by shrinkage behavior and MC changes was monitored, and the development of surface checks was observed during the drying process. Results showed that when the average MC was 60%, the free water in the surface layer of lumber evaporated completely, causing the MC to decrease below the fiber saturation point (FSP). The surface layer was subjected to tension stresses, resulting in surface checks which primarily distributed in the latewood area and propagated longitudinally. When the average MC was between 30% and 40%, the combined effects of the high MC gradient and anisotropic shrinkage of the wood resulted in further expansion of the checks. As the average MC decreased to less than 20%, the MC of the core layer lumber decreased below the FSP, resulting in the closure or even disappearance of most surface checks. The critical point (average MC of 60%) of drying stress was obtained, which can benefit the fine-tuning of kiln-drying schedules and improve the drying quality of Masson pine wood. [ABSTRACT FROM AUTHOR]

In this study, the rotating welding process of Chinese fir (Keteleeriafortunei) in Guizhou, China, was systematically analyzed. The effects of rotating welding conditions, including the dowel-to-guide hole diameter ratio, welding time, depth, base surface, angle, and dowel type, on the performance of welded Chinese fir were explored. Moreover, the physical and chemical changes oftheChinese fir interface during welding were revealed by Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The results indicated the following: (1) The rotating welding technology can quickly achieve a strong connection between wood through friction heat without chemical adhesives and compared with traditional wood connection technology such as gluing or mechanical fixing;it has the advantages of simple operation, high production efficiency; and environmental friendliness. (2) Aftertherotating welding, the wood underwent significant pyrolysis, especially the degradation of hemicellulose. The heat generated in the welding process caused good melting and mechanical interlocking between the dowel and the wall of the guide hole, but it was also accompanied by afriction loss of the dowel and the substrate. (3) The welding parameters affected the wood's connection strength and stability by altering heat production, distribution, transfer, and frictional losses. The impact of the dowel-to-guide hole diameter ratio had a great influence on the connection strength. When the diameter ratio was 1:0.7, the tensile strength was the highest, reaching 2.27 MPa. (4) The analyses of XPS, FTIR, XRD, and SEM proved thatthechemical composition changes at the interface, leading to a more structured crystalline bond and enhanced connection strength due to fiber entanglement and interlocking. This research providesatheoretical and experimental basis forthefurther innovation and development of wood processing technology and provides a new technical path forthegreen manufacturing of wood structure buildings. [ABSTRACT FROM AUTHOR]

Engineered wood products, such as oriented strand board (OSB), are widely used as the primary structural component in both residential and commercial lumber construction, primarily due to their renewability, aesthetic appeal, and excellent mechanical properties. Unfortunately, the inherent flammability of these wood-based composites poses an ongoing risk to society and the environment. In an effort to reduce its flammability, a polyelectrolyte complex (PEC) coating consisting of sodium polyborate (SPB) and polyethylenimine (PEI) was deposited on OSB using a simple two-dip process. This PEC treatment imparts self-extinguishing behavior to OSB and reduces the total heat release by 21% and total smoke release by 79%, while increasing the time to ignition by 18% relative to untreated OSB. Furthermore, the PEI/SPB coating adds little additional weight (5.8 wt%) to the oriented strand board, preserving visual aesthetics and maintaining mechanical properties. The main flame-retardant effect occurs by condensed phase action via a combination of intumescence and thermal barrier mechanisms. Improving the fire protection of OSB and other engineered wood materials through a simple and environmentally benign treatment will increase their potential as a largely renewable building material, promoting a sustainable bioeconomy. [ABSTRACT FROM AUTHOR]

This study was conducted to determine the correlation between the mass loss (ML) of wood due to thermal modification and the equilibrium moisture content (EMC) of thermally modified wood. After thermal modification of larch lumber under various temperature and time conditions, ML according to treatment temperature and time was measured, and the (EMC) of the thermally modified wood was evaluated for each treatment condition. As the treatment temperature increased and the treatment time became longer, the ML of wood due to thermal modification increased. In addition, as the treatment temperature increased, the difference in EMC between the non-treated wood and the thermally modified wood tended to increase. Finally, a robust logarithmic correlation was observed between the ML due to thermal modification and the EMC of the thermally modified wood. These results suggest that the EMC of thermally modified wood can be predicted by simply measuring the weight of wood before and after thermal modification. [ABSTRACT FROM AUTHOR]

In this study, the influence of the diameter of round steel nails, the guiding bores, and the wood sections on the nail holding performance of Pinus massoniana and Cunninghamia lanceolata dimension lumber was explored. The results showed that the nail-holding power of round steel nails mainly came from their friction with wood fibers, while the radial and tangential sections were also affected by the shearing action of wood fibers. The tangential section reached the largest nail-holding power, followed by the radial section and cross section. Greater wood density was associated with higher nail holding power. Under a large nail diameter, however, high-density wood was prone to plastic cracking, which influenced the nail holding power greatly. Prefabricated guiding bores could prevent plastic cracking in wood to some extent and improve the nail holding power of Pinus massoniana and Cunninghamia lanceolata dimension lumber when diameter of round steel nails was more than 3.0 mm. For Cunninghamia lanceolata characterized by low density and rigidity, the wood fiber was in close contact with the round steel nail and internal cracking could not be easily generated under a large diameter of round steel nails. [ABSTRACT FROM AUTHOR]

Laminated veneer lumber (LVL) and laminated veneer board (LVB) panels from jabon wood (Neolamarckia cadamba) were impregnated with fire retardation substances, namely diammonium phosphate (DAP) and sodium silicate (SS). Prior to testing, the boards were conditioned in relative humidity (RH) of 65% and a temperature of 25 °C. The moisture content (MC), bending strength tests in flat wise position, and bonding tests were conducted in accordance with the Japanese Agricultural Standard (JAS:2008). Density tests and hardness tests were conducted in accordance with ASTM D143 standard (2003) in 50 mm x 50 mm. Thickness-swell shrinkage tests were conducted in accordance with the standard BS EN 317:1993, and fire resistance was tested under PS 1-19 standard. The use of 20% DAP and SS solution on jabon wood using impregnation methods affected some of the properties of the panels, especially the moisture content, density, and bonding strength of LVL and LVB compared to the control panels. Both DAP and SS impregnation increased the density. The treatments showed promise for resisting fire, as well as increasing the moisture content and increasing the density compared to the control. [ABSTRACT FROM AUTHOR]

Ebony wood is often defective, showing severe cracks and deformations during manufacturing processes, and requires ample times for drying. The continuous drying has been proved to result in enormous collapses during the entire drying stage. In order to control the extent of collapses and further prevent these defects, a low temperature pre-freezing procedure was projected and followed by a cyclic drying program. This cyclic (intermittent) drying schedule was proposed based upon a so-called "mechano-sorptive creep gradient" (MSCG) strategy and elaborated by a "corresponding temperature differentia" (CTD) concept. The MSCG and CTD variables provided the theoretical explanation and the operational instruction to the cyclic drying test, respectively. The overall evolutions of collapse and transversal shrinkage of the ebony lumber boards were quantitatively investigated during the entire period of a cyclic drying process. Furthermore, the relationships between collapse and moisture content as well as cross section orientation were determined quantitatively. Under this specified pre-freezing plus cyclic drying method, the averaged collapse deformations were significantly decreased, with the maximum collapse variables accounting for 20 ∼ 30% of those under continuous cases, fully achieving the collapse controlling objective. [ABSTRACT FROM AUTHOR]

South Africa is a water scarce country with minimal natural forests. Plantation forest species such as the Mexican tropical hard pine, Pinus patula Schiede & Deppe ex Schltdl. & Cham., was introduced into the country to satisfy local fibre demand. Today, the majority of pine plantations in South Africa are found in the Mpumalanga province. The province has diverse growing conditions in relation to climate and soil properties. Sample plots were established in even-aged P. patula plantations and stratified according to soil parent material and altitude. Growing conditions of each sample plot were characterised according to climate and soil properties. A total of 540 sample trees were measured for height, diameter, density, and latewood content. The sample trees were harvested to produce 2690 logs. The logs were milled, and the resultant lumber was graded according to density, dynamic modulus of elasticity, and modulus of rupture. Annual maximum temperature had the most significant impact on tree growth, while rainfall correlated with wood density and latewood content of standing trees. However, annual maximum temperature and tree height had a negative relationship with the recovered lumber properties and dimensional stability. Spring rainfall appeared to be the most important factor influencing lumber twist and this was possibly due to the associated larger juvenile core present in the trees. [ABSTRACT FROM AUTHOR]

Due to the high growth rates of the forests planted in Brazil and the variations of the mechanical properties within a tree, this study aimed to evaluate the strength (MOR) and stiffness (MOE) in static bending according to the juvenile and adult wood, and the grown-rings inclination at the transversal area of clean specimens of Pinus taeda. Subsequently, the woods were classified in its structural gradings. Pinus taeda logs with 30 years old had the growth rings delimited at every six years on the transversal area. The juvenile wood was represented by the zone of 0 to 6 years of growth (marked with red), and 6.1-12 years (blue). The zone of 12.1-18 (orange) was considered as transition wood and from 18.1-24 (green) and 24.1-30 years (yellow), adult wood. After the sawing, 25 boards were selected to the sawing of the specimens (n = 104) for the static bending test. Growthring inclination was measured as a function of the direction of the load applied at the bending test. Statistical tests were performed in a factorial scheme with the MOR and MOE to static bending. Factors were independent (mechanical properties and growth-rings inclination). The 0-6-year-old wood was not indicated for structural use. Woods between 12-30 years old showed a minimum compatible result to be classified for structural use. The inclination did not influence at the modulus of elasticity and strength at bending. [ABSTRACT FROM AUTHOR]

The effects of laminate configuration on mechanical properties were investigated for model glued-laminated timber (GLT) composed of single and mixed fast-growing tree species (Acacia mangium Willd., Maesopsis eminii Engl., and Melia azedarach L.), which were grown in community forests in Indonesia. The simulation of lamina yield was decreased in graded GLT compared with that in GLT with randomly designed, while the mean values of simulated dynamic Young's modulus (DMOE) in graded GLT were higher than those of GLT with randomly designed in each species. Graded GLT with mixed species should be produced to effectively utilize wood resources from fast-growing tree species. All mechanical properties showed higher values in single-species GLT especially for graded GLT, compared with solid lumber, suggesting that laminate configuration was effective for increasing mechanical properties. However, the factors that increase mechanical properties in single-species GLT differed among species. These factors can be evaluated by load-deflection curves. In GLT composed of single and mixed species produced with the same DMOE, almost all other mechanical properties were similar among laminate configurations. It is concluded that laminate configurations with different species and grades are useful for efficiently producing GLT with higher mechanical properties from multiple fast-growing tree species. [ABSTRACT FROM AUTHOR]

Climate change is one of the main factors influencing the research of environmentally friendly materials. This is why the use of engineering fibers as a reinforcement technique in wood, in order to increase its mechanical properties, has recently been investigated. This research presents the results obtained from the use of carbon and basalt fiber fabrics as a reinforcement for microlaminated Radiata Pine wood panels at a laboratory scale using the adhesives epoxy resin and polyvinyl acetate. Tests were carried out in comparison to the control boards, relating the physical properties obtained in terms of thickness swelling by 48 h-water immersion with a decrease of 19% for the polyvinyl acetate and carbon fiber matrix reinforcement, about the mechanical properties evaluated, a better performance was obtained for the epoxy resin and carbon fiber matrix reinforcement and in terms of flexural stiffness and strength (in flatwise), tensile strength and Janka hardness, with an increment of 31%, 38%, 56% and 41%, respectively. [ABSTRACT FROM AUTHOR]

Acoustics is a field with significant application in wood science and technology for the classification and grading, through non-destructive tests, of a large variety of products from standing trees to building structural elements and musical instruments. In this review article the following aspects are treated: (1) The theoretical background related to acoustical characterization of wood as an orthotropic material. We refer to the wave propagation in anisotropic media, to the wood anatomic structure and propagation phenomena, to the velocity of ultrasonic waves and the elastic constants of an orthotropic solid. The acoustic methods for the determination of the elastic constants of wood range from the low frequency domain to the ultrasonic domain using direct contact techniques or ultrasonic spectroscopy. (2) The acoustic and ultrasonic methods for quality assessment of trees, logs, lumber and structural timber products. Scattering-based techniques and ultrasonic tomography are used for quality assessment of standing trees and green logs. The methods are based on scanning stress waves using dry-point-contact ultrasound or air-coupled ultrasound and are discussed for quality assessment of structural composite timber products and for delamination detection in wood-based composite boards. (3) The high-power ultrasound as a field with important potential for industrial applications such as wood drying and other applications. (4) The methods for the characterization of acoustical properties of the wood species used for musical instrument manufacturing, wood anisotropy, the quality of wood for musical instruments and the factors of influence related to the environmental conditions, the natural aging of wood and the effects of long-term loading by static or dynamic regimes on wood properties. Today, the acoustics of wood is a branch of wood science with huge applications in industry. [ABSTRACT FROM AUTHOR]

Laminated veneer lumber (LVL) and modified grain orientation of LVL (LVB) are composite products made from veneer that are predicted to replace construction timber. The purpose of this study was to determine the physical and mechanical properties of LVL and LVB of mahoni (Swietenia macrophylla), manglid (Manglietia glauca), and gmelina (Gmelina moluccana) and to compare their characteristics. The results showed that the physical and mechanical properties of LVL and LVB generally meet the standards for use in construction. Differences in the properties of LVL and LVB occurred in the properties of hardness and screw tests, while the other properties were similar. The parallel fiber direction was better in terms of adhesive strength, while the compaction density was slightly higher than LVL. The LVL flexural strength was better than LVB in flat and edge test directions. This difference correlates with the adhesive strength in the shear strength test due to the different orientation of the fiber directions. [ABSTRACT FROM AUTHOR]

To promote the performance of fast-growing poplar wood for furniture applications, this study proposes and investigates the feasibility of modifying fast-growing poplar wood with a urea-formaldehyde resin impregnating agent by adding nano-SiO2 as a way to improve its physical and mechanical properties. By observing the solubility of nano-SiO2 addition in urea-formaldehyde resin, determine the optimal ratio of nano-SiO2 addition to the solid content of the urea-formaldehyde resin solution. After the fast-growing poplar specimens were treated with nano-SiO2/UF resin, the water absorption, wet swelling, dry shrinkage, nail grip, flexural strength, and modulus of flexural elasticity of the fast-growing poplar specimens were compared and analyzed to determine the effect of impregnation modification and the optimal impregnation ratio. The results showed that the physical and mechanical properties of fast-growing poplar wood were significantly improved by impregnating the fast-growing poplar wood with urea-formaldehyde resin with SiO2, and the impregnation modification was beneficial to reducing the wet swelling and dry shrinkage of poplar wood, increasing its dimensional stability, improve the grip nail strength, and increase the flexural strength and flexural modulus of elasticity with the increase in nano-SiO2 concentration. [ABSTRACT FROM AUTHOR]

The Japanese longhorn beetle, Anaglyptus subfasciatus, infests coniferous trees resulting in stained wood and low-value discolored lumber. In this study, the discolored Hinoki (Chamaecyparis obtusa) wood was analysed by GC-MS for n-hexane extract, and laboratory wood block tests against termite was carried out. Stained wood had anti-termitic resistance similar to normal heartwood, and it had about twice the n-hexane extract by weight than obtained from heartwood. One compound, nerolidol, was characteristically found in the stained wood. The results suggest that the stained wood may have produced some bioactive components due to damage by wood decay organisms. [ABSTRACT FROM AUTHOR]

One of the goals of the European Union's agroforestry plans is to alleviate the shortage of timber in Europe caused by the growing demand for hardwoods and the declining import of tropical timber. The study shows which tree species can be considered in agroforestry systems in Europe, and which of them can be used as raw material for the wood industry and what quality of wood can be produced in agroforestry systems. Since 2005, the European Union has been officially encouraging farmers to plant the crops in an agroforestry system and parallel try to produce trunks for high quality timber. By analysing the current economic developments of the European Union, especially Horizon 2020, our study provides an overview of what can be expected by the participants of the agroforestry sector and the related primary wood industry in the European Union now and in the future. In addition to the distribution analysis, indices describing projects have also been created. Rank correlation was used to examine the relationship between them. Possible decision mechanisms were also outlined using a custom-built expert software system. [ABSTRACT FROM AUTHOR]

The wood industry faces challenges due to rising prices and limited wood availability, putting pressure on material efficiency in wood processing. This justifies the analysis of the relationship between efficiency and economy in pine wood processing. The study aimed to measure the impact of variations in the thickness of logs, changes in the technology of their further processing, and changes in prices of raw materials and products on the material efficiency in the context of large-scale production of furniture elements made of pinewood. The raw material input consisted of three categories of log sizes, from which the specialized purpose lumber was produced. The lumber was then processed into semi-finished furniture elements with three technologies: without detecting natural wood defects, with human detection, and with automatic detection. The study was conducted in Poland from 2020 to 2022. The material efficiencies in every stage of the analyzed wood processing and the cost efficiencies were calculated and analyzed based on the results obtained under real industrial conditions. The main findings are as follows: (1) when comparing the logs in the three tested diameter ranges (14–23 cm, 23–30 cm, and more than 30 cm), it can be observed that the overall material efficiency of sawing is in the range of 70%–85% and increases with the thickness of the log; (2) the share of 38 mm specialized sawn timber in the total amount of sawn timber was 41%–58% and increased with increasing log diameter; (3) the economic efficiency of the technological process is 170%–290%, based on the log size and the technology of further processing employed. The determining factor affecting cost efficiencies is unexpected changes in raw material prices and product demand in 2022. The findings suggest that while improvements in processing technology can boost efficiency, they cannot fully offset the rise in raw wood material prices. [ABSTRACT FROM AUTHOR]

Due to the high cost of laboratory testing, many researchers are considering developing methods to predict the behavior of unreinforced and reinforced wood beams. This work aims to create either numerical or analytical models useful for extrapolating already conducted tests to other schemes/materials used as reinforcement. In the case of timber structures, due to the complexity of timber, this task is difficult. The first part of the article presents an analysis of the suitability of using a simplified mathematical model based on the equivalent cross-section method to describe the behavior of unreinforced and reinforced with carbon-fibre-reinforced polymer (CFRP) composite full-size laminated veneer lumber (LVL) beams. The theoretical results were compared with the results of conducted experimental tests. The scope of the analysis includes the estimation of modulus of rupture, bending stiffness, and determination of the neutral axis position. The equivalent cross-section method showed good agreement in determining the bending stiffness and neutral axis position of the strengthened sections. However, the suitability of using the equivalent cross-section method to estimate the load-carrying capacity of a cross-section reinforced with fiber composites still needs to be confirmed, which, according to the authors, is due to the differences between the assumed (linear) and actual (nonlinear) strain distribution in the compression zone. The second part uses the equivalent cross-section method to estimate the predicted bending stiffness of LVL beams strengthened with aramid-fibre-reinforced polymer (AFRP), glass-fibre-reinforced polymer (GFRP), and ultra-high modulus carbon-fibre-reinforced polymer (CFRP UHM) sheets. The proposed method can be used for preliminary evaluation of strengthening effectiveness of LVL beams. [ABSTRACT FROM AUTHOR]

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This study demonstrates acetylation with acetic anhydride, one of the few industrial wood modification techniques on the market, to increase the dimensional stability and durability of laminated veneer lumber (LVL) made from beech wood (Fagus sylvatica L.). After being acetylated, veneers were hot-bonded to LVL using phenol-formaldehyde resin (PF) or phenol-resorcinol-formaldehyde resin (PRF). The bonding performance (bonding shear strength (BSS) and wood failure (WF)) was tested under the following three conditions: 20°C and 65% RH, water immersion, and rigorous boiling-drying-boiling cycle. Additionally, using the same specimen sizes on a second sample set, the moisture content (MC) and dimensional stability were determined. Results indicate that the PRF resin provided the strongest bonding performance on acetylated LVL and references. Acetylated LVL had higher BSS in wet conditions than untreated controls, especially after boiling in water, which could be attributed to less wood-water interaction at the cell wall level after acetylation. [ABSTRACT FROM AUTHOR]

Evaluation of the acoustic properties of objects using the results as an informative parameter in determining the physical and mechanical characteristics of a material, is widely used in modern science and technology, as well as in the field of nondestructive testing. In the present paper the possibility of using this approach is considered in relation to the woodworking industry in order to estimate the characteristics of sawn timber modified by the ultrasonic method. The results of previous studies have shown the effectiveness of this technology for increasing the surface density and hardness of wood; therefore, one urgent task is to find criteria that allow evaluating the achieved modification parameters, as well as optimizing the settings of the corresponding technological equipment. In this paper the research results of the acoustic properties of ultrasonic modified aspen wood (Populus tremula) are presented and their applicability as a criterion for estimating the degree of lumber modification is determined. [ABSTRACT FROM AUTHOR]

Drying is a fundamental step in the lumber production process. The definition of variables that affect the quality of the process, such as initial and final temperatures as well as drying potential, depends on the known technological knowledge of the wood, as well as on the experience of the drying process developed for a particular species. With this in mind, we developed an experiment using wood from four genetic materials (three clones and one seminal) of the species Tectona grandis cultivated with and without fertilization. This was done to estimate and evaluate the parameters used in the explanation of drying programs. The values of the initial and final temperatures, and those of the drying potentials, were estimated using the drastic drying methodology, which evaluates the drying rate and defect score (cracks and collapse). In addition to the drying parameters, the physical properties that affect the drying performance were also evaluated. The results show that origin and fertilization did not affect the initial and final temperatures. However, the potential drying parameters were significantly affected by the combination of treatments. Furthermore, the wood drying potential of certain genetic materials was positively affected by fertilization. Finally, the material from the fertilized areas had the lowest basic densities, the highest initial moisture content, and the highest drying rates. [ABSTRACT FROM AUTHOR]

In this paper, two kinds of laminated bamboo lumber specimens with 7 groups of fiber angles on plane A and B were designed. The effects of different angles on the compressive strength and stiffness of laminated bamboo lumber were analyzed. According to the test results, the load displacement curves, ultimate strength values and initial stiffness of all specimens were obtained. The compressive strength test values of pin groove based on American Standard 5% diameter offset method were obtained. The results demonstrated that the compressive strength of the pin groove of laminated bamboo lumber obtained by 5% diameter offset method was relatively uniform. The compressive strength of class A pin groove decreased with the increase of angle. The coefficient of variation was within 9.42%, and the standard deviation within 6.33. The compressive strength of class B pin groove first decreased and then increased with the increase of angle. The coefficient of variation was within 12.10%, and the standard deviation within 6.67. The relationship between different fiber angles and the compressive performance of laminated bamboo lumber were analyzed, and the test results were compared with the theoretical formula calculated in the European wood structure and American wood structure design standards. The calculation model of pin groove compressive strength with different fiber angles was put forward. [ABSTRACT FROM AUTHOR]

The relaxation of growth stress in trees from plantation forests of tropical areas is manifested in the quality of wood after the sawing and the relaxation of drying stress is expressed during the drying process, producing low wood quality. The present study aims to evaluate the lumber quality in logs by heating and steaming application before sawing as pretreatment to reduce growth stress and the application of steaming step during drying of Dipteryx panamensis (almendro) and Hieronyma alchorneoides (pilón) wood. The results showed that the variation of moisture content and drying rate concerning drying time in wood from logs steamed before or during drying led to a quick increase in the drying rate and a decrease in the moisture content. The steaming application to the logs or during drying decreased the incidence and magnitude of drying defects and increased the quality of dried lumber, especially bow, split, crook, and check defects. [ABSTRACT FROM AUTHOR]

Wood is a viable alternative to traditional steel, cement, and concrete as a structural material for building applications, utilizing renewable resources and addressing the challenges of high energy consumption and environmental pollution in the construction industry. However, the vast supply of fast-growing poplar wood has bottlenecks in terms of low strength and dimensional stability, making it difficult to use as a structural material. An environmentally friendly acrylic resin system was designed and cured in this study to fill the poplar cell cavities, resulting in a new type of poplar laminated veneer lumber with improved mechanical strength and dimensional stability. The optimized acrylic resin system had a solid content of 25% and a curing agent content of 10% of the resin solid content. The cured filled poplar veneer gained 81.36% of its weight and had a density of 0.69 g/cm3. The static flexural strength and modulus of elasticity of the further prepared laminated veneer lumber were 123.12 MPa and 12,944.76 MPa, respectively, exceeding the highest flexural strength required for wood structural timber for construction (modulus of elasticity 12,500 MPa and static flexural strength 35 MPa). Its tensile strength, impact toughness, hardness, attrition value, water absorption, water absorption thickness expansion, and water absorption width expansion were 58.81%, 19.50%, 419.18%, 76.83%, 44.38%, 13.90%, and 37.60% higher than untreated laminated veneer lumber, demonstrating improved mechanical strength and dimensional stability, significantly. This method provides a novel approach to encouraging the use of low-value-added poplar wood in high-value-added structural building material applications. [ABSTRACT FROM AUTHOR]

Assisted gene flow according to expected climate gradients is considered as a forest management strategy to mitigate impacts of environmental change on forest growth. However, the effects of seed translocation on wood properties and lumber quality remain unknown. This study evaluated the effect of provenance origin on lumber production and quality at rotation age in two white spruce provenance trials established in contrasting environments in eastern Canada. Based on 108 sample trees, which resulted in 943 pieces of lumber, average volume production per tree at the southernmost site was twice that of the production at the northern site. Provenance had a significant influence on growth and lumber strength in the first sawlog but had no effect on lumber stiffness and wood density. Although visual grade yields of No. 2 and better were high in both trials (over 86%), the machine stress rated (MSR) grade potential and percentage of lumber that met the bending stiffness design values of the visual grades were generally low (12%–26%). Hence, plantation-grown lumber should preferably be machine stress rated to ensure its fitness for structural applications in buildings. Management strategies aiming to efficiently sequester carbon should primarily maximize volume productivity in northern sites, as moving seed sources north still reduces provenance productivity, while breeding programs should aim to prevent decrease in lumber stiffness due to augmented productivity and shortened rotation cycles. [ABSTRACT FROM AUTHOR]

Asymmetrical internal stress profile within the kiln-dried lumber assessed using the restoring force technique on the half-split specimen has been investigated. Unlike the symmetrical internal stress profile in which the measured restoring force is completely described by an elastic beam theory, the asymmetrical internal stress profile also induces a so-called remnant force. By using the released strain and the elastic modulus data across the entire thickness obtained from the McMillen slice test, a numerical result based on the finite element model successfully simulates the restoring force profile for an entire range of both symmetric and asymmetric stress profiles. The finite element model is leveraged to evaluate the effect of asymmetry of stress profile on the remnant force. The value of the remnant force linearly depends on the stress profile deviation which is inferred to the level of asymmetric stress profile. [ABSTRACT FROM AUTHOR]

Indonesian Wooden Building Code (SNI 7973-2013) has adopted the National Design Specification (NDS) for Wood Construction since 2013. A periodic harmonization of the building-code-designated values (i.e., reference design values and adjustment factors) with the experimental data of commercial wood species is necessary. This study aimed to compare the building code's wet service factors (CM) with the laboratory test of some commercial wood species. Since wood is weaker when its moisture content is high, the wet service factor (CM) must adjust the sawn lumber reference design values if the building serves in wet or aquatic environments. Four commercial wood species, namely pine (Pinus merkusii), agathis (Agathis dammara), red meranti (Shorea leprosula), and mahogany (Swietenia mahagoni), were subjected to mechanical property tests. To calculate the empirical CM values, the mechanical properties tests were conducted on air-dry and wet wood. Instead of testing the full-sized timber, which contains the growth characteristics and defects, this study chose clear-wood specimens to resemble the boundary condition of the ceteris paribus (other things being equal). The wet (water-saturated) specimens were immersed in water for 65 days, and the test was carried out when the specimen was still immersed. The test arrangement imitated the submerged wood as the worst-case scenario of the wet environment where the construction serves, rather than green or partially immersed timber. As many as 40 specimens were tested to compare each mechanical property's wet service factor; thus, this study reported 200 specimens' laboratory test results. The empirical CM values to adjust the modulus of elasticity, modulus of rupture, shear strength parallel-to-grain, tensile strength parallel-to-grain, and maximum crushing strength (CM = 0.59, 0.76, 0.65, 0.73, and 0.67, respectively) were significantly lower than SNI 7973-2013 designated values (CM = 0.9, 0.85, 0.97, 1, and 0.8, respectively). The empirical CM for the compression stress perpendicular-to-grain at the proportional limit and that at the 0.04″ deformation (CM = 0.66) were slightly lower than the designated values (CM = 0.67), although they were not significantly different. This study resulted in lower empirical CM values than the designated ones, which found that the building code lacked conservativeness. The lacked conservativeness is mainly attributed to the building code's recent choices, e.g., (1) the wet service environment basis is the green timber rather than the fully water-saturated one, and (2) the ratio of near minimum (5% lower) distribution value is chosen as the CM value rather than the average of wet timber's mechanical property divided by the air-dry one. This study proposes changing both recent choices to alternative ones to develop more safe and reliable designated CM values. [ABSTRACT FROM AUTHOR]

In this paper, a symbiotic experimental and numerical approach is used to determine the structural performance parameters and analyse the failure behaviour of a novel high-performance hybrid steel-grout connector for cross-laminated timber (CLT) panels. The connector is composed of a steel rod, which is embedded into a 3-ply CLT panel with the aid of a thick layer of epoxy-based grout. Material tests on wood from the two lumber grades present in the CLT panels, and on the epoxy-based grout were conducted to provide an insight into their mechanical behaviour. Forty-two monotonic push-out shear tests were conducted on connectors, varying the grout layer diameter thrice and the loading direction twice. A finite-elements (F.E.) model for the connector was developed in the F.E. software ANSYS and calibrated based on experimental observations on materials and connectors. The tested connectors proved to be strong and stiff in both loading directions, with a maximum slip modulus of 111 kN/mm, yield resistance of 177 kN, and maximum resistance of 192 kN. The diameter of the grout was found to significantly influence all three performance parameters, and much so when the connector was loaded in the direction perpendicular to the CLT face layers. The developed F.E model was able to capture the slip modulus, yield resistance, and maximum resistance with an accuracy above 95 %. The F.E. model also sheds light on the structural performance, yield mechanism, and failure propagation for connectors. • The grout diameter positively influences the slip modulus, yield, and ultimate resistance of connectors • The effect of the load orientation on the structural performance of connectors decreases as the grout diameter increases • The finite-element model developed is able to capture the load-slip behaviour and failure mode of connectors with an error below 5 % [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the mechanical properties determined in a 4-point bending test of beams made of lumber from which knots had been locally removed and the resulting loss replaced with sound wood. Three sets of beams were prepared, which differed in the number of layers/lamellas and the position of the lamellas from which edge knots were removed. All the lamellas used in the tests were subjected to a modulus of elasticity assessment. In addition to the distribution of defects, it determined the position of a given piece in the beam structure. The tests showed that high mechanical properties could characterise the beams produced in this way, i.e., a modulus of elasticity close to 12 kN/mm2 and a strength above 40 N/mm2, if the lamellas without knots were located below the outer tension lamella. Significantly better results were obtained when PUR glue was used in the inserts rather than MUF. In this case, beams with an improved outer lamella in the tension zone using semi-circular inserts glued with PUR glue had an average strength of 34.6 N/mm2. [ABSTRACT FROM AUTHOR]

Due to wood moisture sensitivity, shrinkage cracks tend to present wooden structures. These failures are caused by moisture-related shrinkage behavior. In order to avoid it, it is necessary to have a better understanding of shrinkage behavior. In this respect, studying the dimension changes in wood at different scales is of utmost significance for a better understanding of the shrinkage properties. Herein, the shrinkage behavior of Masson pines (Pinus massoniana) wood was investigated at macroscopic and cellular levels during moisture loss via digital image correlation using VIC-3D and digital microscopic systems, respectively. According to the full-field strain maps, shrinkage strain near the external face was higher than that at the internal face, which increased susceptibility to cracking at the external face of lumber. Additionally, the anisotropic shrinkage of wood was explored. The shrinkage ratio at the end of drying was about 5.5% in the tangential (T) direction and 3.5% in the radial (R) direction. However, at a cellular level, the shrinkage ratios in the T and R directions of earlywood tracheids were 7.13% and 2.46%, whereas the corresponding values for latewood tracheid were 9.27% and 5.52%, respectively. Furthermore, the maximum T/R shrinkage ratio at the macroscopic level (1.7) was found to be similar to the value of latewood tracheid (1.72). The earlywood showed high anisotropic, its T/R shrinkage ratio was 2.75. The macroscopic shrinkage was the result of the interaction of the tracheids of earlywood and latewood and was mainly dominated by latewood tracheids. [ABSTRACT FROM AUTHOR]

This review critically examines the various ways in which the mechanical properties of wood have been understood. Despite the immense global importance of wood in construction, most understanding of its elastic and inelastic properties is based on models developed for other materials. Such models neglect wood's cellular and fibrous nature. This review thus questions how well models that were originally developed for homogeneous and effectively continuous materials can describe wood's mechanical properties. For example, the elastic moduli of wood have been found by many authors to depend on the size of the test specimen. Such observations are incompatible with classical elasticity theory. There is also much uncertainty about how well elastic moduli can be defined for wood. An analysis of different models for size effects of various inelastic properties of wood shows that these models only approximate the observed behaviour, and do not predict or explain the scatter in the results. A more complete understanding of wood's mechanical properties must take account of it being in some sense intermediate between a material and a structure. [ABSTRACT FROM AUTHOR]

This review aimed to analyze plastic lumber manufacturing in Brazil, a country with a large amount of natural wood, and devise strategies to boost production. No studies were found on the development and application of plastic wood in a natural wood producing country that has been significantly affected by deforestation. Wood-plastic composite lumber was used in the present study. The methodology consisted of a bibliographic review, questionnaire, SWOT and TOWS analyses. The questionnaire was completed by plastic lumber manufacturers in order to better understand the positive and negative points of the plastic wood market and production. Information on environmental, economic and technical aspects was collected to support analyses. Brazil has 11 plastic lumber producers with a production capacity of 11 × 103 metric tons, a very small amount when compared to the natural wood market. Established companies are seeking to expand domestic and foreign markets for plastic lumber, which is largely composed of polyethylene with several lignocellulosic fibers, especially wood residue for civil construction applications. According to SWOT analysis, Brazil is developing plastic lumber with several strengths (opportunities). TOWS analysis showed that in order to boost plastic lumber production, make it more competitive and reach international markets, wood and plastic residue should be aimed at manufacturing WPC. Brazil produced around 37 × 106 metric tons of wood residue and discarded approximately 16 × 106 metric tons of plastic waste in landfills, materials that could potentially be used to produce plastic lumber. There are other raw material alternatives for plastic lumber production in the agricultural sector, such as straws and grain husks. However, the country urgently needs to develop a reverse a logistics network and residue collection, as well as conduct research to channel residues to plastic lumber production. Thus, there is a greater likelihood of continued development and, consequently, attracting new markets. There is an attempt to overcome weaknesses (plastic lumber is not used for structural applications), demonstrating the need for strategies that foster technical development for structural applications. Threats (high prices and lack of fiscal incentives) require coping strategies to increase production, thereby reducing its cost. These measures could increase plastic lumber production, making it competitive enough to replace natural wood, and lead to a decline in deforestation. [ABSTRACT FROM AUTHOR]

Partially threaded screws are essential fasteners in timber structures, and their use in combination with hardwoods is promising in order to obtain high-performance connections. Depending on the used wood species, the load-displacement behaviour and failure mechanisms of connections change, and, in particular for high-density species, brittle failures may occur more frequently with rather low ductility of the connection. Consequently, a good understanding of the mechanical behaviour of connections at different displacement levels helps to assess where previous rules reach their limits for hardwoods. The determination of all input parameters serves as a basis for a subsequent test programme on single-shear timber-to-timber connections using beech laminated veneer lumber, birch, spruce glulam and predrilled and non-predrilled partially threaded screws. Tests on connections with one screw and groups of screws are conducted, stopped at predefined displacement stages of 5, 10 and 25 mm, and opened. A comparison of the screw deformation at the different displacement stages reveals that non-linear connection behaviour is quite different in softwood and hardwood. Essential aspects of the analysis are particularities of the load-displacement behaviour, fastener spacing, ductility of connections and the progressive plasticising of the fasteners. [ABSTRACT FROM AUTHOR]

Although small solar photovoltaic (PV) systems avoid most soft costs, they still have a relatively high $/W value due to racking costs. In order to fulfill the promise of small-scale plug-and-play solar, a do-it-yourself PV rack design is provided and analyzed here for six criteria: (1) made from locally-accessible renewable materials, (2) 25-year lifetime to match PV warranties, (3) able to be fabricated by average consumers, (4) able to meet Canadian structural building codes, (5) low cost and (6) that it is shared using an open-source license. The open-source wood-based fixed-tilt ground-mounted bifacial photovoltaic rack design evaluated here was found to be appropriate throughout North America. Economic analysis of the bill of materials showed the racking system ranges from 49% to 77% less expensive compared to commercial proprietary racking in Canada. The racking design, however, is highly dependent on the cost of lumber that varies widely throughout the world. Even for an absolute lower-cost design in Togo due to a lower fixed tilt angle and lower loads from lack of snow, it was not found to be economic because of the relatively high cost of wood. The recent volatile lumber market warrants local evaluation from those considering the use of the open-source design. This design, however, provides for a PV rack that can be manufactured with distributed means throughout most of the world enabling more equitable access to solar energy to support a circular bioeconomy. [ABSTRACT FROM AUTHOR]

Pilot-scale oil heat treatment was conducted to enhance the quality of poplar wood obtained from a fast-growing plantation. Three target temperatures, namely 180, 190, and 200 ˚C, were chosen for the oil heat treatment process. Clear, small specimens were cut from the lumber, following the prescribed standards for assessing wood quality. Light microscopy revealed the ruptures and deformation of the wood cell wall as the treatment temperature increased. The volumetric swelling of the treated specimen decreased proportionally with the increase in treatment temperature. The impact of oil heat treatment on the mechanical properties of wood varied depending on the specific type of mechanical strength and processing temperature. The modulus of rupture, toughness, and hardness of the treated specimens drastically decreased at 200°C. However, the specimens treated at 200°C exhibited much lower mass loss during the fungal decay test. The results of the analytical test showed an increase in the crystalline cellulose content and thermal stability of the treated wood, due to the thermal degradation of hemicelluloses and amorphous regions of cellulose. Overall, it is concluded that oil heat treatment of poplar wood in the optimal temperature is an efficient approach to upgrade its quality with minimal reduction in mechanical strength. [Display omitted] • The potential of a pilot - scale oil heat treatment (OHT) was evaluated to upgrade the quality of poplar wood. • Higher treatment temperature resulted in higher durability and hydrophobicity. • Mechanical properties differed depending on the heating temperature. • Hemicellulose degradation was identified as a key factor driving changes in wood characteristics during soybean oil heat treatment. [ABSTRACT FROM AUTHOR]

Wood properties, including Young's modulus, differ among clones in Larix kaempferi; however, available information is still limited on among-clonal variations of lumber qualities in L. kaempferi. The objectives of this study were to clarify the clonal variations in lumber quality and to identify the effects of juvenile wood on lumber quality in L. kaempferi. A total of 21 logs of 2.5 m in length were obtained from the trees of nine different plus clones of 57-year-old L. kaempferi trees. The logs were sawn into lumber, and the lumber was kiln-dried and planed into 38 × 89 mm in a cross-section. Lumber quality, such as bending properties, was determined. Significant differences were found in wood density, dynamic Young's modulus, modulus of elasticity, and modulus of rupture of the lumber among the nine clones. The highest repeatability was recorded in wood density. The lumber consisting of juvenile wood showed a lower lumber quality compared to the lumber consisting of mature wood. To produce lumber with a high quality from L. kaempferi, the clonal variation of lumber quality and the existence of juvenile wood should be considered. [ABSTRACT FROM AUTHOR]