European Journal of Wood and Wood Products最新文献

Structural performance of timber buildings can be adversely affected by exposed harsh environment and sustained load. This study investigates bending performance degradation of glued laminated timber (GLT) beams (50 mm × 50 mm × 950 mm) that are exposed to unfavorable environmental conditions. The experiments consider eight scenarios, including various climate cycling periods, duration, and stress levels. Eight groups of GLT beams were exposed to the different scenarios for four stages, then loaded by short-term bending to obtain the MOR and MOE. The results showed that coupling effects of sustained loading and the environmental factors such as UV-light and mist spraying aggravated the pronounced damage on the laminates and gluelines and caused the degradation of strength and stiffness. The highest degradation rate occurred in the first stage. In the relatively mild environments, some performance recovery was observed in the later stages, most specimens exhibited ductile failure accompanied by the significant increase of the ultimate deflection with the exposure time. While in the harsh environments, the MOR and MOE degradation was evident and continuous, more specimens experienced brittle failure, and the increase of the ultimate deflection slowed down greatly with the exposure time. Additionally, the effects of sustained loading period were significantly exacerbated under the harsh environmental conditions, the specimens loaded by less than 50% stress level exhibited the distinguished degradation in 24 days.

In order to reduce modeling workload and improve the accuracy of wood density measurement, a modeling method for establishing an overall model for multiple tree species was studied. Firstly, the wood cores and drill resistance of 9 tree species were collected. The absolute dry density, wood moisture content, and average drill resistance for each wood core were calculated. Secondly, the random forest algorithm was used to rank the relative importance of each factor affecting wood density, and factors with relative importance higher than 0.05 were selected as independent variables for building the overall mathematical model for total tree species and sub model for individual tree species. The results showed that: (1) the relative importance of tree species and drill resistance on wood density was higher than 0.05; (2) the relative importance of moisture content and drill usage frequency (less than 150 times) on wood density was lower than 0.05; (3) the average estimation accuracy of overall model was 91.42%, while that of the sub model was only 90.44%; (4) among the 9 tree species, the standard deviation of the overall model for 5 tree species was lower than that of the sub model. The results showed that the accuracy and stability of the overall model were superior to those of the sub models, and it is feasible to establish an overall model to estimate wood density.

The aim of this study was to improve the flame retardation and performance characteristics of wood through impregnation with magnesium-based compounds. Fir wood (Abies sp.) samples, both heat-treated and non-heat-treated, were impregnated with magnesium oxide and magnesium chloride using combined and separate methods. Impregnation was carried out under an initial vacuum followed by pressure. The effects of impregnation on the wood's structure, thermal properties, and fire resistance were investigated using FTIR spectroscopy, XRD analysis, TGA analysis, and flame retardation tests. FTIR, XRD, and TGA analyses confirmed increased thermal stability and crystallinity in impregnated samples, especially non-heat-treated samples. Wood impregnation with magnesium compounds extended the time to ignition, reduced flame duration, and decreased glowing combustion duration. Impregnation of samples resulted in a less carbonized surface. The lowest carbonized surface was observed in the combined-method impregnated non-heat-treated sample. Based on the results of this study, it can be concluded that the impregnation of heat-treated and non-heat-treated wood with magnesium compounds (oxide and chloride) was successful in improving flame retardation and performance characteristics.

Wood density is an important characteristic of wood which correlates to its strength. This study proposes an algorithm using multiple regression on pre-segmented colour images of the wood to estimate the density of light red meranti (Shorea spp.) (LRM). Two batches of LRM timber were randomly selected from a factory (Batch 1: 119 samples, Batch 2: 79 samples). Timber samples were kiln-dried, free of sapwood and major visual defects, and freshly surfaced 2 sides. The apparent density and moisture content (MC) of each timber sample were measured. The samples were then imaged and colour-sorted using KayuSort, an in-house industrial timber colour sorting prototype that uses the self-organising map (SOM) algorithm. Otsu thresholding was applied to several different colour space components to obtain features. Multiple regression was applied to obtain an equation to estimate the density of the wood. Coefficients of determination ((hbox {R}^{2})) and 95(%) Limits of Agreement (LoA) were used to assess performance. Performing colour segmentation to the dataset using KayuSort for average (text {YC}_b{text{C}}_r) colour space scored an (hbox {R}^{2}) of 0.7109 and an LoA of ±146.8 (hbox {kgm}^{-3}). Therefore, it is possible to estimate the density of LRM using colour features of the wood using KayuSort, with the caveat that timber is kiln-dried to under 15% MC, freshly surfaced, without major defects and sapwood, and within the thickness range of 26.9 to 30.6 mm.

Several Malagasy Dalbergia and Diospyros species are highly valued, in the furniture industry despite limited understanding of their wood technological properties. This study contributes to address this gap by assessing the wood density (WD) of 38 Dalbergia and 29 Diospyros species, their radial WD variation, and the influence of climate and tree size on WD. WD was measured on 297 wood cores using X-ray computed tomography. One-way analysis of variance revealed that Diospyros genus (1.070 ± 0.165 g∙cm⁻³) has significantly denser heartwood compared to Dalbergia (0.961 ± 0.142 g∙cm⁻³). Heartwood density also showed greater between-species variation, allowing the identification of eleven groups of Dalbergia and seven groups of Diospyros, each with significantly different heartwood density ranges. For radial density profile assessment, each of the 52 cores having the pith-to-bark part of the wood, was divided into ten equal length segments. Anova between mean WD of the core segments, combined with correlation tests between the average density of each segment and its distance from the pith, showed that radial wood density profile varied among species. Most species exhibited a decreasing radial WD profile. Correlation tests between tree diameter, climatic factors, and wood density demonstrated that, for both genera, wood density increases with rising temperature and decreasing precipitation at the growth site, while tree diameter has no significant effect on density. These findings significantly enrich the wood density database for Malagasy precious wood species, which previously existed for only a very few species.

The effects on the measurement of water sorption and apparent diffusivity when using different flow rate values and different experimental setups, i.e., closed pan, open pan and hanging setup, have been studied in a series of Dynamic Vapor Sorption (DVS) experiments on a spruce sample. The results confirm a concave exponential growth dependency between apparent diffusivity and flow rate and an effect from the setup used, with the hanging setup being optimal for conducting such experiments due to the exposure of both areas of the disk to the airflow.

To prevent cracks in the wooden soundboards of harps while maintaining its acoustic performance, Sitka spruce wood was impregnated with phenol formaldehyde (PF) resin. PF treatment significantly improved the dimensional stability of wood through the bulking effect of the PF resin introduced into the wood cell wall. Highly moistened wood was fixed at its ends and dried. The unmodified wood failed owing to drying stress, whereas the PF-treated wood did not fail because of its excellent dimensional stability. In addition, PF treatment was found to significantly reduce the internal friction of the wood, resulting in an improvement in the acoustic conversion efficiency. These results suggest that PF resin impregnation is a promising method for preventing the cracking of soundboards without degrading their acoustic quality. By contrast, the PF resin migrated around the surface, from which the solvent evaporated. If we need to modify the wood uniformly along the longitudinal (L) direction, its ends or cross-sections should be closed to prevent the migration of the PF resin along the L direction during solvent removal. It is practically difficult to prevent the condensation of the PF resin around the straight-grained surface when a large-dimensional soundboard is impregnated with PF resin. However, the results of a simulation using a multilayered model predicted that such condensation did not adversely affect the acoustic quality of the soundboard.

The existing research mainly improves the performance of wood (round tenon) rotating welded specimens by using a single type of additive. Due to the single type of chemical additive used, the performance of welded specimens is limited. Therefore, we have found a joint pretreatment modification method that can simultaneously improve the waterproof, mechanical, and environmental adaptability of welded specimens. It mainly includes: the CA group (calcium carbonate and oleic acid treatment) and, the CN group (Na₂SO₃ and CuSO₄ oxidation sulfonation treatment). Techniques such as scanning electron microscopy, mechanical testing (Wood Nail Grip Strength testing and Water Resistance Test testing), Fourier transform infrared spectroscopy, X-ray diffraction, and pyrolysis gas chromatography–mass spectrometry were utilized to assess the welded interfaces. Methods including pyrolysis gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy, mechanical testing, X-ray diffraction, and scanning electron microscopy were employed to evaluate the welded interfaces. Following the treatments, the interfaces displayed a grout-like layered structure with increased amounts of cellulose and lignin, enhancing intramolecular cohesion. Hydrogen bonding of oleic acid-stearic acid and tetrahydrofuran (THF) and high molecular weight aromatic methoxy groups were generated at the welding interface of the CA group. Consequently, this leads to a significant improvement in the mechanical properties and water resistance of the rotating welding interface, which in turn enhances the environmental adaptability of the welded specimen. Excluding the CN group, all samples met the ≥ 0.7 MPa strength criterion set by GB/T 14018–2009 “Test Method for Wood Nail Grip Strength” in China, with the CA group showing superior interface performance, In addition, the calcium carbonate whiskers in the CA group enhanced the mechanical properties of the welded specimens, but weakened the water resistance, which led to a large difference between dry and wet in the CA group. The CN group enhances the activity of lignin due to the oxidative sulfonation reaction, maintains a certain viscosity of the welding interface, and is resistant to water. Therefore, although the overall welding strength is low, there is no dry and wet difference in this group.

Traditionally, there are two types of wood fiber insulation boards (WFIB), the rigid ones produced in the industry by a continuous steam process, bonded with polymer diphenylmethane diisocyanate (pMDI), with densities between 80 and 200 kg/m³, and the flexible ones with densities under 80 kg/m³ produced by hot air, usually with bicomponent fibers as a binder. In this work, wood fiber insulation boards (WFIB) were produced with polylactic acid (PLA) as a binder by hot press (HP) and hot air (HA). WFIB with densities of 60 kg/m³, 80 kg/m³, 100 kg/m³ and 5%, 10% and 15% of PLA percentage were produced by hot press (HP) and hot air (HA). Wood and PLA fibers were examined by scanning electronic microscope (SEM) and optical microscope. The WFIB were assessed for physical properties as density and short-term water absorption as well as for their resistance to compression as a mechanical property. Thermal properties such as thermal conductivity and thermogravimetric analysis (TGA) were also tested. In the produced WFIB, the values of density follow the same pattern as water absorption, compression strength, and thermal conductivity. The polylactic acid (PLA) content improves mechanical value like compression and diminishes physical value such as short-term water absorption in WFIB. In conclusion, wood fiber insulation boards (WFIB) were successfully produced with polylactic acid (PLA) as a binder, by hot press (HP) and hot air (HA), reaching remarkably lower thermal conductivity values, comparable with commercial ones.

A field test with two-year-long exposure of natural cork to aboveground and underground conditions was carried out with analysis of CIELAB colour parameters, cellular features by scanning electron microscopy, and surface chemistry by ATR-FTIR. The impact of weathering and soil burial was different regarding changes in colour and surface chemistry. Under atmospheric exposure to weather, cork was bleached (ΔE* 17.1) mainly due to the photooxidation of lignin by UV-radiation and hemicellulose degradation, with suberin remaining mostly unaffected. With soil burial, cork darkened (ΔE* 19.7) while significant depolymerization and degradation of suberin and hemicelluloses occurred in addition to lignin alteration. Only the external one-cell layer at the surface was affected with some cellular expansion and minute cell wall fractures, while the material maintained its characteristics without damage or deterioration signs. The cork weathering features are indicative that it can be used in outdoor applications such as building façades or external equipment, with only surface colour dynamics to be taken into account.