Wood Science and Technology最新文献

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.

This work examined the chemical interrelations between melamine–formaldehyde (MF) and waterlogged archaeological wood to demonstrate the effect of the MFtreatment on cultural heritage objects. Samples from a Roman waterlogged trunk of Greek fir, were analyzed with Fourier Transform Infrared Spectroscopy (FTIR), solid-state ¹³C Nuclear Magnetic Resonance (NMR), analytical pyrolysis with in-situ silylation Py(HMDS) coupled with Gas Chromatography Mass Spectrometry (GC/MS) and Evolved Gas Analysis-Mass Spectrometry, (EGA-MS) before and after the MFtreatment. FTIR results showed the formation of amide functionalities due to melamine reactions and strong evidence of lignin modification, while the deteriorated cellulose fraction appeared to have undergone further depletion as a result of the MF treatment. The ¹³C NMR spectra of the MF-treated wood clearly demonstrated the presence of the resin within the wood and indicated that MF carbons were strongly interacting with lignin moieties. Spectra also revealed that the retention of the MF resin in the wood was positively correlated to the degree of wood degradation. Py(HMDS)-GC/MS of MF-treated wood provided few peaks attributed to holocellulose or lignin pyrolytic products, and it was not possible to detect any signs of non-MF-modified wood components, as the lignocellulosic wood matrix appeared to have been transformed into a new biopolymer. EGA-MS profiles of the MF-treated archaeological wood showed early evolution of volatiles due to free MF retained in the wood, while its thermal stability appeared increased in comparison to untreated material. Nonetheless, mass peaks indicated that the chemistry of MF-treated wood was completely different from both fresh and untreated deteriorated wood. Overall, results showed that the MF treatment irreversibly modified the residual chemistry of the archaeological material and failed to preserve its original physical and historical integrity. This permanent modification of unknown longevity is considered not in line with conservation ethics and, therefore, inappropriate for the long-term preservation of cultural heritage objects.

Sawdust from deciduous trees was used as a raw material for the preparation of carbonaceous adsorbents. Microwave-assisted chemical activation with K₂CO₃ and H₃PO₄ was used to produce materials with a well-developed porous structure. The obtained activated biocarbons were characterized in terms of their porous structure, elemental composition, morphology, thermal stability, as well as surface and electrokinetic properties. The sorption abilities of both materials towards synthetic (poly(acrylic acid)) and natural (lysozyme) polymers in the process of their removal from aqueous systems were determined. Both single adsorbates and mixed solutions of two polymeric adsorbates were tested. The stability of aqueous suspensions containing activated biocarbons and one or two polymers was also determined. As a result of microwave-assisted chemical activation two carbonaceous adsorbents were obtained, characterized by a very well-developed specific surface area (1093–1777 m²/g), a completely different type of porous structure (mesoporous or microporous), and the acidic nature of the surface. The maximum adsorption of poly(acrylic acid) was obtained from a mixed solution of both polymers and it reached values of 379 mg/g (for the sample activated with H₃PO₄ with mean pore diameter 3.04 nm and minimal contribution of micropores—0.3%) and 259 mg/g (for K₂CO₃ activated material characterized by the mean pore diameter equal to 1.72 nm and large contribution of micropores—77.4%). In the case of lysozyme, the adsorption efficiency was two times lower (sorption capacity of 127–166 mg/g). Based on the collective data analysis, it can be stated that the most probable mechanisms of polymeric destabilization (highly desirable in separation from the multicomponent solutions) are surface charge neutralization at pH 3 and bridging flocculation at pH 11 (especially for the systems containing material activated with H₃PO₄ and poly(acrylic acid)).