Wood Science and Technology最新文献

Effective utilization of small-diameter hardwood, including large-diameter branches, has become increasingly important for sustainability. These materials consist of small-diameter logs with irregular shapes; consequently, the timber products contain both sapwood and heartwood and frequently exhibit tension wood (TW). Therefore, the continuous variation from pith to bark, and from TW to opposite wood (OW) must be considered when using these logs for timber. However, there is limited information on the radial heterogeneity of physical properties from the pith to the bark, particularly regarding TW formation. In this study, an inclined thick branch of a keyaki tree (Zelkova serrata Makino) was used to measure the radial distribution of wood physical properties—such as hygrothermal recovery (HTR) strain, drying strain, cellulose crystallinity index (C.I.), and microfibril angle (MFA) related to G-layer proportion—from the pith to the bark. On the upper half of the inclined branch, the G-layer was formed, and its proportion remained nearly uniform. Higher C.I., smaller MFA, and greater drying strain were observed in this region, primarily influenced by the G-layer proportion. The HTR strain exhibited behavior characteristic of TW near the bark on the upper side. However, as it approached the pith, the HTR strain displayed behavior distinct from that of TW. This suggests that the HTR strain reflects not only the G-layer proportion but also other factors related to the distance from the pith, such as the history of residual growth stress accumulation in the xylem during secondary growth.

Illegal logging poses a significant threat to ecosystems and undermines legal timber markets. Efforts to combat the issue are often hindered by the lack of robust tools for species-level wood authentication. Traditional methods such as anatomical observations and DNA analysis frequently struggle to achieve accurate species-level identification. Chemical profiling of wood metabolites has emerged as a promising alternative. Two powerful techniques, Direct Analysis in Real Time Time-of-Flight Mass Spectrometry (DART-TOFMS) and Comprehensive Two-Dimensional Gas Chromatography Time-of-Flight Mass Spectrometry (GC×GC-TOFMS) offer unique strengths for wood identification. DART-TOFMS enables rapid chemical analysis with minimal sample preparation. GC×GC-TOFMS, known for its exceptional separation capabilities, allows for detailed chemical profiling that may enhance species-level discrimination. Despite their potential, direct comparisons of these two techniques for species-level classification have not been done yet. In this study, we present a comparative analysis using 60 wood core samples from two Quercus (Oak) species and 60 stemwood samples from three Picea (Spruce) species. Each sample was analyzed using both DART-TOFMS and GC×GC-TOFMS. Partial Least Squares Discriminant Analysis (PLS-DA) was employed for classification modeling, with feature selection based on VIP scores. Our results show that both techniques demonstrated strong classification performance in differentiating both Quercus and Picea species. Notably, GC×GC-TOFMS yielded slightly higher classification accuracy in this study, which may be attributed to its enhanced separation capabilities and ability to resolve structurally similar compounds such as isomers. The findings from this work will contribute to a deeper understanding of the capabilities of both techniques in wood metabolomics, with applications in forensic science and efforts to combat illegal logging.

Experimental characterization of wood fracture properties raises a number of challenges: crack tip location or the application of equivalent linear elastic fracture mechanics theory to a heterogeneous and anisotropic material. This article presents the application of the Localized Spectrum Analysis, a full-field measurement method, to obtain high-resolution strain maps for the analysis of three mode I crack propagation tests on TDCB silver fir wood specimens. The strain maps presented enabled us to identify annual rings through stiffness variations, to observe internal cracks through abnormal compression zones, and to determine the material’s resistance-curves, therefore its critical energy release rate. This work opens up interesting prospects for the use of new measurement methods in the characterization of wood fracture properties.

Thermal treatment has become an important approach to improve the dimensional stability and durability of wood, owing to its environmental friendliness and sustainability. During thermal treatment, the hydrophilic functional groups and pore structure of wood undergo significant changes, thereby affecting its hygroscopicity; however, the dynamic coupling relationship and quantitative contributions of these factors under varying relative humidity (RH) remain insufficiently clarified, and the characterization of cell wall pores at different RH levels is still challenging. To address these issues, this study refined the Horikawa-Do (H-D) model to quantify the contents of hydroxyl-bound water and pore-confined free-bound water in heat-treated wood under different RH levels, and further developed cell wall pore prediction model based on sorption isotherms. The results showed that both hydroxyl-bound water and pore-confined free-bound water coexist at any RH. At low to medium RH, hydroxyl-bound water adsorption predominates, whereas at high RH, pore-confined free-bound water adsorption dominates. Thermal treatment reduced the hydroxyl content of wood and enhanced hydroxyl binding energy, thereby significantly decreasing hydroxyl-bound water content, while increasing the hygroscopic ratio of pore-confined free-bound water (from 2.02 to 4.15 at 90% RH). This caused the “equilibrium point” between the two hygroscopic mechanisms to shift toward lower RH with increasing treatment temperature, indicating that thermal treatment primarily reduced wood hygroscopicity by decreasing hydroxyl-bound water. In addition, the average size of water clusters associated with moisture sorption was positively correlated with RH but negatively correlated with treatment temperature. The pore size prediction model revealed that the dominant hygroscopic pore size range in wood treated at 230 °C (1.58–2.36 nm) was significantly narrower than that in untreated wood (1.93–3.07 nm), with reductions of 22.2% and 34.1% in the minimum and maximum pore sizes, respectively. These findings systematically elucidate the microscopic mechanisms underlying the improvement of wood dimensional stability by thermal treatment.

The high-value utilization of thinning residues from plantation forests has long been a key focus for sustainable forestry development. The critical challenge lies in the green and value-added utilization of forestry waste and the enhancement of its performance. In this study, thinning Chinese fir wood was used as a carbon source to synthesize carbon dots via a hydrothermal method. Polyethylene glycol was employed to modify the carbon dots, forming PEG-CDs, and their synergistic effect in modifying the cell walls of thinning Chinese fir wood was investigated. The results show that PEG modification successfully introduced hydroxyl and ether hydrophilic groups onto the surface of the carbon dots, enabling their interaction with lignin and cellulose through hydrogen bonding and ether linkages. The PEG-CDs were uniformly distributed within the cell walls and pores of the wood. Furthermore, the modified wood exhibited 14% increase in thermal stability and a 17% improvement in cell wall modulus. Through a ‘strengthening wood with wood’ strategy, this study elucidated the nanoscale reinforcement mechanism of PEG-modified CDs via multiscale characterization. A low-energy, fully biomass-based wood functionalization approach was developed, offering a novel strategy for the green valorization of forestry waste and the design of high-performance eco-friendly wood materials.

We studied the suitability of forest management residues as feedstock for bioenergy production. We focused on the variability of their chemical and physical properties that are most likely to influence the efficiency of thermochemical conversion and the factors underlying this variability, namely wood species, stage of wood decomposition, and the site characteristics of the source location. We used wood from leftover logs and large branches of birch (Betula papyrifera and Betula alleghaniensis) and balsam fir (Abies balsamea), which are abundant in the boreal and mixedwood forests of Quebec (Eastern Canada) and likely to be found as residues on cutblocks. We used factor analysis of mixed data and linear mixed models to explore the relationships among wood species, decomposition class, chemical concentrations and density, and site characteristics such as bioclimatic conditions and soil cation exchange capacity. Model results showed significant impacts of species interacting with bioclimatic domains, notably on net calorific value, wood base cations (calcium, magnesium and potassium) and carbon concentrations. Balsam fir had the highest net calorific value (ranging from 17.0 to 17.4 MJ kg⁻¹) compared with birch (16.3 to 17.0 MJ kg⁻¹) in two of the three studied bioclimatic domains. However, balsam fir potassium concentration was doubled compared to birch (593 vs 245 ppm respectively) in one bioclimatic domain, which can be undesirable for thermochemical conversion. The wood decomposition class was effective at predicting significant decreases in wood chemical components (potassium, cellulose and hemicellulose concentrations). Our results suggest that forest management residues from balsam fir and birch could be suitable for biomass procurement, providing insights into their potential for bioenergy production in eastern Canada.

High-strength joints are increasingly used in timber structures to take advantage of the shear properties of wood. Therefore, understanding the long-term shear performance is essential. In this study, the long-term shear behavior of timber was evaluated using the tensile-shear test method. A duration of load (DOL) test was conducted to assess shear performance parallel to the grain under sustained loading. The test was carried out at loading levels ranging from 70% to 90%. The obtained strength modification factors as well as duration of load coefficients were greater than those specified in the current Japanese timber design standards, indicating that the code-specified values are conservative. In other words, the existing provisions ensure safety margins relative to the actual performance observed in the test. These results satisfy the requirements of the Japanese design code and are considered applicable to international design frame works, demonstrating the global relevance of the findings. The results indicate that the deformation at failure tends to converge at approximately 0.3 mm. A correlation was observed between deformation and environmental conditions, with the specimens loaded in April (n = 2) demonstrating greater deformation than the loaded in October (n = 4). The strength modification factor was determined to be 0.67, which is considered a safe value compared to the current standard of 0.55. This result is consistent with values reported in the previous study involving creep limit test study.

Densified delignified wood (DW) is a novel engineering material with ideal specific strength based on the delignification and densification of natural wood (NW). However, the dependence of mechanical performance on structural characteristics (e.g. density, ρ) of DW has not been systematically elucidated, which limits the practical application of DW in engineering fields. To bridge this gap, this work investigates the strength, ductility and fracture toughness of DW with various ρ under tension parallel and perpendicular to the grain. The elastic modulus (E) and tensile strength (S) increased as ρ increased in both longitudinal (L) and tangential (T) directions. Fracture strain (ε_f) increased as density increased in the T direction, while a first decreasing and then increasing trend occurred in the L direction. This trend is the opposite in the work of fracture (W). A first decreasing and then increasing trend is observed of W in the T direction due to the coupling effect of delignification and densification. The mechanical performance of DW is found to be governed by the two-stage densification process during the preparation of DW. A transition density (ρ_n) is proposed herein to distinguish the two densification stages. When ρ is less than ρ_n, void collapse restricts gains in E, S and W while reducing ε_f due to loss of pore cushioning. When ρ is larger than ρ_n, cell-wall densification enhances fiber packing and hydrogen bonding, simultaneously improving all four mechanical properties. This work is expected to develop a deeper understanding of the multiscale mechanical design and mechanical behavior of cellulosic and wooden materials.

The outer bark of Betula pendula (silver birch), a lignocellulosic byproduct of wood processing, offers valuable opportunities for the recovery of high-value bioactive compounds. betulin, a triterpenoid responsible for the white coloration of silver birch bark, has attracted considerable attention due to its pharmacological properties, including antioxidant, anti-inflammatory, and anticancer effects. In this study, a green ultrasound-assisted extraction (UAE) method was developed and optimized for the selective extraction of betulin from Betula pendula outer bark. In order to evaluate the effects of ethanol concentration, temperature, sonication amplitude, and cycle on betulin yield, a Box–Behnken design was employed in combination with response surface methodology. Optimal conditions were identified at 92% ethanol, 57 °C, 70% amplitude, and 0.3 Hz^− 1 cycle for 15 min of extraction. The process demonstrated excellent repeatability (C.V. < 5%). A positive correlation was identified between betulin concentration and antioxidant capacity, thereby confirming the efficacy of the employed methodology. This work constitutes a significant UAE protocol for B. pendula outer bark, delivering 34.63 mg·g^− 1 betulin and outperforming conventional techniques in terms of time and solvent usage, thus contributing to the development of circular biorefinery approaches within the wood industry.

Failure of mortise-and-tenon (M-T) joints used in wooden furniture construction is primarily attributed to long-term cyclic loading. Therefore, understanding how cyclic load alters the physical and mechanical properties of M-T joint components and leads to fatigue damage is essential. This study examined the effects of four cyclic load amplitudes (CLA: 150, 200, 250, 300 N) and four cyclic load count ratios (CLCR: 0, 25%, 50%, 75%) on the fatigue damage progression (FDP) in non-glued beech M-T joints. The assessment was conducted by quantifying changes of M-T porosity, fit, friction coefficient and the joints’ direct withdrawal load resistance (DWLR). Experimental analysis revealed that the porosities at the end section (5 mm, 20% of the T length) and the middle section (8 mm, 30% of the T length) of fatigued Ts decline linearly as functions of CLCR and CLA, respectively. The end section exhibits lower porosity than the middle section, and its porosity decreases at a higher rate as CLCR increases from 0 to 75%. The damage factor of M-T joints increases with CLCR and CLA. Across all tested CLA levels (150, 200, 250, 300 N), the ends section of fatigued Ts consistently exhibited higher damage factors than the middle section. The friction coefficients of fatigued M-T joints were found to follow a power function relationship with CLCR. The M-T fit decreased significantly as CLCR increased from 25% to 75% and showed a further decline with increasing CLA from 150 to 300 N. The reduction of M-T fit also showed a power function relationship with CLCR. Within each of the four CLA levels, the DWLRs of fatigued M-T joints decreased linearly with CLCR, and the slopes of these linear relationships increased as CLA increased from 150 to 300 N. Furthermore, the DWLRs can be estimated using the derived regression model, which incorporates the friction coefficients of the M-T materials, the M-T fit, the CLA level, and the initial DWLR.