Wood Science and Technology最新文献

Laminated veneer lumber panels (LVL) are engineered wood products suitable for application in construction contexts. However, LVL panels have some deficient elastic properties (e.g., ({E}_{22})) concerning other elastic properties (e.g., ({E}_{11}) and ({G}_{12})), which may cause problems in structural applications. Carbon and basalt fibers (CF and BF) are reinforcement alternatives for LVL panels, as they can be included in the interior or exterior wood veneer bonding process. This work aims to analyze the effect of incorporating CF and BF fibers in the orthotropic elastic properties of radiata pine LVL panels through a nondestructive method based on transverse vibration tests and model updating techniques. Accordingly, 20 LVL panels of 15 mm thickness were fabricated and tested with different reinforcing fibers and adhesives. Then, some relevant panels’ dynamic properties were identified through experimental modal analysis. Finally, three relevant panels’ orthotropic elastic properties were estimated simultaneously using finite-element model updating techniques and Python-based deterministic calibration scripts. The results suggest that the reinforced LVL panels obtained significant increases in their orthotropic elastic properties, in the order of 22%, 333%, and 27% for ({E}_{11}), ({E}_{22}), and ({G}_{12}), respectively. These results show the effectiveness of the type of reinforcement applied and the potential application of the nondestructive evaluation method in other contexts.

Accurate prediction of moisture distributions in wood is among the most critical challenges in timber engineering. Achieving this requires a well-coordinated comparison of experimental methods and simulation tools. While significant progress has been made in developing simulation tools in recent years, a lack of experience with and trust in these tools continues to hinder broader implementation, especially when it comes to free water and its absorption. Investigations and model advancements have allowed for the simulation of increasingly complex cases, including one-dimensional moisture transport above the fiber saturation point (FSP) in coated boards and below FSP in coated glued laminated timber (GLT). However, free water flow in coated GLT beams has not yet been addressed, which can become problematic in case of extreme scenarios, such as water infiltration. In this study, we demonstrate that the multi-Fickian free water transport model developed by some of the authors can successfully simulate three-dimensional coated cases. Uncoated and coated boards and GLT members were subjected to cyclic wetting and drying, both experimentally and numerically. To simplify the calibration process of the mass transfer coefficient of free water—identified as the most significant parameter for the simulation of free water transport—experiments previously conducted by some of the authors were simulated. Based on the simulation results, approaches for an initial estimation of the mass transfer coefficient were developed. If the water uptake of coated specimens is measured three days after continuous soaking in water and the result exceeds a specific limit, the coefficient can be sufficiently predicted. The simulation and experimental results show a good agreement.

Trees exhibit adaptability in response to external loads, which allows them to form an inosculated connection (self-growing connection) with a neighboring tree. Such connections have the mechanical potential to build living tree structures. Although qualitative studies have studied this phenomenon, quantitative analysis of its growth features remains limited. Self-growing connections fused by weeping figs (Ficus benjamina L.) are utilized to study growth features. X-ray scanning and optical microscopy techniques are employed to investigate parameters including density, geometry, fiber structures, and material compositions. Key findings demonstrate that the fused region of a connection has a larger volume and a higher density on the intersected surface. Microscopic analysis identifies that the enlarged wood in the fused area is tension wood characterized by G-layers. The key component that connects trees is referred to as merged fibers, and the pattern of their distribution is found to be mainly in the outer layer of the larger cross-angle of a connection. At the cellular level, crystals within cells are identified in the fused region, implying possible mechanical stresses the interface has experienced. The findings in self-growing connections can serve as inspiration for structural design in living structures, biomimicry, bioinspired structures, and advancements in bioeconomics.

Wood-steel hybrid (WSH) elements are gaining popularity in the construction industry due to their reduced environmental impact and high load capacity. However, fire resistance remains a crucial challenge for advancing wood as a construction material. The proposed WSH slab consists of a trapezoidal steel profile sandwiched between two laminated veneer lumber (LVL) beech panels. This research aims to numerically predict the fire performance of the proposed WSH slab element by generating heat transfer models that consider convection, radiation, and conduction. The objectives are to predict the temperature profile of the system's components, assess the charring rate of the LVL panels, and validate the results with experimental fire tests. Computed Tomography (CT) scanning was additionally used to detect the material density variation in the remaining LVL layers after fire tests. Simulations reveal that the size and shape of the internal cavity significantly influence heat flow within the system. Analysis of different thicknesses and heights of the steel sheet shows a substantial impact on the charring initiation time of the upper LVL layer. Temperature profiles of the components from numerical analysis exhibit similar behavior to that observed in the experiments. The experimental charring rate averages between 0.88—1.00 mm/min, while the numerical rate averages between 0.95—1.06 mm/min, with a 5–8% average deviation attributed to conduction interaction between LVL and the steel sheet. This variation may also be caused by the definition of generic thermal properties of wood according to EN1995-1-2, which may not accurately represent the behavior of the LVL element under fire.

When a loaded piece of wood is exposed to variable climatic conditions, the stress state depends on both the stress and moisture content change history due to the memory creep. To explore this complex time-dependent interaction, a new experimental device has been developed. Called the "fork" device, this simple setup allows the evolution of the memory creep of twin wood samples to be determined continuously under different loads. In this work, this device has been used at low temperature (i.e. 30 (^{circ })C) and with six different humidity cycles to focus on the mechanosorptive part of the memory creep. The test was performed with thin quartersawn and flatsawn samples of beech and oak originally at green state. periods were chosen to obtain a moisture content quickly close to the equilibrium moisture content for each plateau. With negligible moisture gradient, the dynamics of mechanosorption was measured and compared with moisture variations, species and load direction. The results highlight an increase in mechanosorptive strain with cumulative moisture content variations with an asymptotic behavior towards a limit. For oak and beech, a common compliance can be found for each grain direction.

Softwood branches develop compression wood (CW) in the lower parts of the branch, while opposite wood (OW) develops on the upper. These wood types differ in structure at several length scales, among others in the chemical composition of their lignin matrix. While OW mostly contains guaiacyl (G) units, CW is known to contain a substantial fraction of 4-hydroxyphenyl (H) lignin. In this study, the impact this difference has on lignin hygroexpansion and interaction with water is studied by the means of atomistic models and molecular dynamics computer simulations of lignin systems at different levels of hydration. It was found that, despite the minor difference in chemical composition, there are differences in swelling, structure and water dynamics. CW lignin is found to have a higher uniaxial swelling coefficient, since the phase separation between lignin and water is more pronounced. This behavior is linked to structural differences, where intermolecular ({pi -pi }) stacking is more common in CW lignin and hydrogen bonding to water more pronounced in OW lignin. These findings are of interest for understanding the role of lignin in CW, and general understanding of moisture interaction with lignin inside wood cell walls.

Consolidation has always been a major conservation issue for waterlogged archaeological wood (WAW), which aims to prevent shrinkage and cracking upon drying. Here we developed a new organic solvent-free consolidation method using water-soluble amino silanes and dialdehydes, which involves versatile cross-linking processes between wood components and polysiloxane. Evaluations by shrinkage measurements after air-drying, Fourier transform infrared spectroscopy, static thermal dynamic analysis, and dynamic vapour sorption suggest the combination of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and glutaraldehyde provides the most satisfying dimensional stability, mechanical strength and hygroscopicity. The anti-shrinkage efficiency reached as high as 96.9% for highly degraded WAW of Catalpa sp. after air-drying. The bending strength was increased to approximately 4 times and the elastic modulus was increased by around 10 times. The described method provides a new solution for the consolidation and dehydration of WAW, which produces excellent dimensional stability in lab-scale trials after air-drying without using organic solvents. However, studies are required on the long-term stability of the materials and durability of the treated WAW against microbial and chemical degradation before it can be applied in practice.

Wood density is a crucial property indicator for construction material selection, quality assessment, and modification. Spectral analysis techniques and chemometric models offer potential solutions for the rapid and non-destructive assessment of wood density. However, probe-contact spectroscopy has low efficiency in spectrum collection, and spectral models are highly specific to variations in instruments and samples. Traditional calibration transfer methods are diverse and struggle to adapt to domains with significant distributional differences. By simulating operations under natural light, this work aimed at exploring a deep transfer-learning strategy, facilitating the transfer of wood density prediction models between different instruments [from portable near-infrared (NIR) spectrometers to hyperspectral-imaging (HSI) imagers] and among tree species (two softwood and two hardwood species). A bidirectional gated recurrent unit plus attention layer (BiGRUattention) was employed as the basic topology for the deep network. The results indicated that the generalization ability and robustness of HSI model transferred by deep adversarial transfer-learning strategy, including domain-adversarial-neural Network (DANN) and dynamic-adversarial- adaptation network (DAAN), surpassed traditional calibration transfer and deep transfer-learning methods, achieving a level comparable to NIR-calibrated models. DAAN based on Wasserstein distance with gradient penalty (WgpDAAN) optimized model accuracy, convergence speed, and stability. The deep adversarial transfer-learning model could be adapted to wood spectral data from different instruments and tree species, where WgpDAAN significantly reduced modeling costs and enhanced productivity, and could be extended to detecting and characterizing other wood properties.

This study aimed to investigate the effects of mineral impregnation on fir wood using magnesium-based compounds. Two methods, combination and separate treatment, were used to impregnate heat-treated and non-treated samples. The Bethel method, involving vacuum and pressure, was employed for the impregnation process. The impregnated samples underwent assessments for weight gain, volumetric bulking, water soaking tests, water droplet contact angle, mechanical properties, and fire resistance. Additionally, SEM and EDAX analyses were conducted to evaluate the changes in the wood structure pre- and post-impregnation. The findings revealed the filling of pores and cavities in certain areas with Sorel cement, particle accumulation in cell walls and cell lumina, and an increase in the presence of Mg, Cl, and O elements in the impregnated samples. Furthermore, the physical property analyses indicated improved wood properties post-impregnation, with the combination impregnation method demonstrating the most notable performance in terms of weight gain percentage. Electron microscopy confirmed the formation of the magnesium oxychloride cement structure within the cell voids of both types of wood. The mineralization of the wood structure with magnesium compounds resulted in increased dimensional stability, reduced water absorption, and enhanced bulking and density of the wood. Moreover, the contact angle of water droplets on the wood’s surface decreased following impregnation with magnesium compounds, while the surface roughness of the wood increased. Mineral impregnation significantly enhances the bending strength, modulus of elasticity, impact resistance, and fire resistance of wood, regardless of heat treatment. The combined impregnation method consistently outperforms the other method.

Strand characteristics, i.e. orientation, length, width, and size, have a substantial effect on the mechanical properties of Oriented Strand Board (OSB). In this study, an automatic method was established to obtain the characteristics of the strands on the surface layer of the OSB mattress in real time by taking images and using neural networks. The Segment Anything Model was used to extract surface layer strands, the YOLOv5 model was used to distinguish and position strands, and the minimum bounding rectangle algorithm was used to measure characteristics of each strand. Based on the results obtained from manual measurement, the performance of the automatic method was evaluated. In laboratory tests, this method presents great performance in extracting and distinguishing characteristics of strands. This method also shows good adaptability for production line application. In the production line, around 80% of strands can be correctly extracted and distinguished, with a strong correlation between manual measurements and automatic method results (R² > 0.97). It takes 37.7ms to process one image containing approximately 500 strands. Strand orientation in the production line nearly concords with normal distribution (N (-1.25, 30.5²)). The size of strands significantly affects the relative intensity of the strand orientation (with P < 0.05). There is a positive and linear relationship between the strand size and the orientation of strands. The outputs of this study contribute to a better understanding and management of OSB manufacture in the production line.