European Journal of Wood and Wood Products最新文献

The influence of size effects on the shear strength and stiffness of glued-laminated timber (GLT) made from European ash (Fraxinus excelsior L.) was assessed based on a comprehensive experimental campaign. The experiments were performed on full-scale GLT beams with rectangular cross-sections width × height = b × h = 120 × 480-800 mm², shear lengths L_v = 720-1500 mm, and ratios between the shear length L_v and the beam height h, i.e. α = L_v/h = 1.2-2.5. The influence of the test configuration (3-point bending and asymmetric 4-point bending) was also assessed. The obtained shear strengths of European ash GLT had mean values f_{v, mean} = 10.2 N·mm^-2 (coefficient of variation CoV_fv = 14%) and 12.2 N·mm^-2 (CoV_fv = 15%), for the 3-point and asymmetric 4-point bending test configurations, respectively. The shear strength showed some size dependency, with an exponent 1/m = 0.2 0.4 for a strength modification factor (600/h)^1/m as a function of the beam height h. The shear modulus showed no size dependency and the obtained mean values were G_mean = 1162 N∙mm^-2 (CoV_G = 6%) and 1120 N∙mm^-2 (CoV_G = 6%), for the 3-point and asymmetric 4-point bending tests, respectively.

The durability of hybrid composites under environmental and biological stresses is a significant challenge for sustainable structural materials. This study assessed vacuum-infused hybrid composites made of Pinus elliottii veneers, unidirectional jute fabrics, fiberglass mats, and an unsaturated isophthalic polyester matrix. Manufactured via the Vacuum Infusion Process (VIP), composites with varied stacking sequences were tested against fungal decay and accelerated weathering. Decay tests using Trametes versicolor involved 16 weeks of incubation, monitoring mass loss weekly. Accelerated weathering in a QUV chamber exposed samples to cycles of UV radiation, simulated rain, and moisture for 15 weeks, with weekly evaluations including mass loss, colorimetric analysis (CIELab), and FTIR spectroscopy. Fiberglass-faced composites demonstrated superior T. versicolor resistance, with minimal mass loss due to protective polyester and fiberglass layers. Conversely, wood-faced composites were more vulnerable, showing greater mass loss and chromatic changes. Weathering caused significant reductions in chromatic parameters (a* and b*), especially in wood-faced composites, due to lignocellulosic degradation. FTIR analysis revealed carbonyl and ether bond breakdown in the polyester matrix, with more pronounced degradation in hydrophilic jute-layered composites. These results underscore the potential of hybrid composites as durable, sustainable materials for extreme environments, with tailored configurations enhancing resistance to environmental and biological stresses.

Black locust (Robinia pseudoacacia L.) has great potential for weathered exterior applications due to its natural durability and density. In particular, the narrow sapwood range and the crooked trunk areas with strong fiber inclination make the production of veneer lumber from shorter logs very interesting, except for logs with a tension back. This paper describes selected elasto-mechanical properties of robinia laminated veneer lumber, tested in a climate of 20 °C and 60% relative humidity and at the fiber saturation point. In particular the Young’s modulus (E_L, E_R, E_T) in tension, the Poisson’s ratios (µ_LT, µ_TR, µ_LR), and the strengths (σ_L, σ_R, σ_T). were determined experimentally by tensile tests, and the lateral strain coefficients µ_TL, µ_RT, and µ_RL were calculated from these values. The results show a significant decrease in Young’s modulus and modulus of rupture with increasing wood moisture content in the longitudinal, radial, and tangential directions. There was no notable dependence of the lateral strain coefficients on moisture content. Additionally, no significant correlations were observed between the investigated properties and gross density, nor between Young’s modulus and tensile strength. Unlike Young’s modulus and tensile strength, the lateral strain coefficients showed no clear trend with increasing wood moisture content. The strain coefficients are in good agreement with literature values, but further research with larger samples and different material sources is needed to complete the engineering constants. In addition, characteristic values of component size and material durability are of interest for future development.

In the 1950s and 1960s, Eucalyptus camaldulensis trees were planted in the Lazio region (Central Italy) as windbreaks to protect crops. Nowadays, a maintenance plan has been implemented to manage these windbreak systems, resulting in a significant quantity of wood, currently used almost exclusively as biomass for energy. This study aims to explore the potential of this material for higher-value applications in industries beyond energy production. To this end, we conducted a classical technological characterization to establish preliminary knowledge of the physical, mechanical, and anatomical properties of E. camaldulensis specimens obtained from the management of windbreak belts in Tarquinia (Central Italy). The assessment considered radial and axial variations and compared the results with those of other Eucalyptus species to evaluate possible industrial uses. Physical characterisation included density, basic density, and radial, tangential, and volumetric shrinkages. Mechanical tests measured axial compression strength, bending strength, and hardness. Anatomical analysis examined fibre dimensions (length and diameter) and the proportions of heartwood, sapwood, and bark. The average density was 734 kg/m³ (12% MC) and the basic density was approximately 620 kg/m³. In general, the density seemed to increase with the increasing distance from the ground. Radial and tangential shrinkage were 5.6% and 8.7%, respectively; compression strength averaged 49.4 ± 7.9 MPa, bending strength 84.5 ± 22.8 MPa and hardness 30 MPa. Fibres length and diameter averaged 886 µm and 19 µm, respectively. A decrease in fibre diameter was observed with increasing distance from the ground, coupled with an increase in slenderness ratio. These characteristics suggest the feasibility of an alternative cascade use of the material, highlighting its potential applications beyond energy production.

This study was aimed at exploring the sheer creep behavior of wood through off-axis tensile creep and creep recovery tests. Using the creep recovery data, the shear creep properties of softwood (Japanese Hinoki cypress, Chamaecyparis obtusa) and hardwood (Japanese Buna beech, Fagus crenata) were compared. The trends of three components of strain, i.e., instantaneous elastic, delayed elastic, and permanent strains, during shear creep were predicted by decomposing the total strain during creep recovery, assuming that the rate of increase in delayed elastic strain is the same as the recovery rate during creep recovery. Fitting a Burger model to each predicted strain yielded more reliable material parameters compared with those obtained by simply mathematically fitting the Burger model to the total creep strain. The Burger model demonstrated excellent accuracy in fitting the measured creep curves of hardwood. However, it could not explain the shear creep behavior of softwood. This discrepancy in the fitting results was attributable to the differences in the behavior of permanent strain: The permanent strain of cypress exhibited a curvilinear trend, while that of beech displayed a more linear trend. To explain the curvilinear behavior of permanent strain, a modified Burger model, which assumes that the apparent viscosity of permanent strain changes in a strain-rate-dependent manner, was proposed. The modified Burger model yielded better fitting results than the conventional Burger model, suggesting that the viscous component of wood exhibits an apparent viscosity that depends on the strain rate rather than a constant value, as assumed in the conventional Burger model.

The Atkins model has been widely adopted for determining mechanical properties of wood, such as fracture toughness and shear yield stress, which are typically normalised by global density for cutting force and power predictions. This study explores the feasibility of determining these mechanical properties for knotty and clear Scots pine (Pinus sylvestris L.) using local densities revealed by X-ray computed tomography scanning. Six wood workpieces, three from Poland and three from Sweden, were scanned and subsequently cut on a custom single-tooth quasi-linear cutting machine. Cutting forces for both clear and knotty regions were recorded and normalised by local densities. Results indicate that clear Polish pine exhibits higher local-density-normalised fracture toughness and shear yield stress than Swedish pine, suggesting that wood origin influences mechanical properties beyond mere density differences. Knots display significantly lower local-density-normalised shear yield stress compared to clear wood, despite their higher density. The large variation in normalised fracture toughness observed in knots is attributed to differences in cutting direction relative to knot orientation. The study highlights the effectiveness of computed tomography scanning to provide detailed insights into wood density and structure, enabling more accurate normalization of cutting forces and enhancing the understanding of wood machinability across different origins and structural characteristics.

As a valuable biological resource, wood plays a vital role in human societal development. However, wood undergoes biotic and abiotic degradation and dimensional instability, which limit its applications. Wood modification techniques, including acetylation, furfurylation, and silicification, can help enhance the durability and sustainability of wood. However, the effectiveness of these methods varies depending on the wood species and origin, emphasizing the need for further research to refine these techniques and enhance the wood performance for diverse industrial applications. This study aimed to investigate the effectiveness of three modification methods for Korean domestic wood species by assessing their effects on the weight% gain (WPG), equilibrium moisture content, water absorption, anti-swelling efficiency, and fungal decay resistance. Attenuated total reflectance (ATR)–Fourier transform infrared spectroscopy and scanning electron microscopy were conducted for the chemical and structural characterization of modified wood. The applicability of the modification methods was tested using five Korean domestic woods, sampled from Radiata pine, Korean red pine, Japanese larch, Hybrid poplar, and Sawtooth oak. The results showed that furfurylation produced the highest WPG, water resistance (WR), dimensional stability, and fungal decay resistance among the modification methods on all the tested wood materials. Acetylation and silicification also enhanced the dimensional stability and fungal decay resistance; however, the WR differed depending on the wood species and type. This study provides valuable insights into the applicability of three modification methods for improving the durability and performance of Korean domestic wood species and contributes to the sustainable utilization of wood in various industries.

This study reveals the magnitude of stress spread angles in the design of plywood gusset plates when subjected to uniaxial tension, with a specific focus on mechanical connections. Plywood plates with elevating widths at three different load-face grain angles were destructively tested. The test series continued with consecutively increased plate widths until the measured forces reached plateaus. Two models, namely, the classic and modified stress spread models, adopted from the Whitmore effective width theory, were investigated to account for the observed phenomenon. The classic stress spread model considers a rigid fastener array and an evenly distributed stress block. A closer-to-reality modified model considers the summation of stress blocks contributed from each fastener line. For both models mentioned, the magnitudes of corresponding spread angles were calibrated utilizing a fitting scheme considering maximized R-square values. The validity of both models was later examined and validated versus the previous experimental data reported in the literature. It was found that the classic model, despite some close predictions, gave over-estimations on the load-bearing capacities of several connection patterns. The modified model was found to be conservative for almost all investigated fastener patterns. Accordingly, a hybrid adoption of stress spread models was suggested.

Different tree species exhibit significant variations in physical properties, uses, and economic value, making accurate species identification crucial. Traditional methods relying on human visual inspection are time-consuming and susceptible to subjective experience and fatigue. This paper proposes an RGB image expansion method based on hyperspectral data and an optimized Mask R-CNN model for wood species identification. First, 600 hyperspectral images of wood blocks of four tree species (Larch, Spruce, Birch, and Poplar) were collected. Principal Component Analysis was used to reduce the dimensionality of the hyperspectral images, followed by spectral band recombination to enhance texture features, resulting in a dataset of 1873 RGB images. Secondly, Leaky ReLU was used in place of ReLU as the activation function for the residual blocks. The ResNet50 and ResNet101 networks, combined with Feature Pyramid Networks were served as the two foundational feature extraction networks, and Convolutional Block Attention Module (CBAM) and Squeeze-and-Excitation Network (SENet) were inserted at different layers of the feature extraction network. Experimental results show that appropriate integration of attention mechanisms at different layers of the backbone can improve model accuracy and reduce loss rates. The ResNet101-CBAM3-SENet4 model exhibited the best overall performance, with precision of 0.9574, 0.9778, 0.9592, and 0.9783 for the four wood species in the test set, and an average precision of 0.9680. The mean Average Precision was calculated as 0.9657, and the mean Average Recall was 0.9806. This research provides new directions for dataset expansion in image identification and accurate identification of wood species with similar textures.

Wooden fasteners are gaining increasing attention due to their potential to enhance automation in wood processing, recyclability, sustainability, and producing Engineered Wood Products free from metal fasteners and adhesives. The mechanical response of wooden fasteners differs significantly from conventional metal fasteners. This distinct behaviour necessitates the development of specific guidelines and standards for assessing and designing wooden fastener connections. Current standards, such as the Eurocode and National Design Specification, along with existing research, offer empirical equations that are not fully applicable to wooden fasteners. Proper evaluation of wooden fastener joints requires the determination of key mechanical properties, including maximum bending moment, maximum bending strength, shear strength, and embedment strength. However, the flexible nature of wooden fasteners and their size and geometry make the determination of these properties challenging. This review critically examines the mechanical properties of wooden fasteners, factors influencing their performance, testing methodologies, failure modes, deviations from existing metal fastener standards, and emerging trends and challenges in the design of wooden fastener-based connections. This critical comparative review of wooden fasteners and their quantitative evaluation of deviations from steel fasteners provides valuable insights that will be helpful for future standards and innovation related to wooden fasteners.