European Journal of Wood and Wood Products最新文献

While traditional wood preservatives may impede wood decay, their potential harm to both human health and the environment has led to limitations in their usage. This has spurred recent research to focus on seeking wood preservatives derived from plants, owing to their inherently eco-friendly attributes. Agricultural waste such as corn stover fractions, are not only abundant but also frequently underutilized, making them promising candidates for such endeavors. This study delves into the antifungal properties of extracts derived from thermally degraded corn stalk and corn cob. The selection of optimal raw materials and the identification of the most effective thermal degradation process were determined based on their inhibitory activity against Gloeophyllum trabeum (Pers.: Fr.) Murr. and Trametes versicolor (L. ex Fr.) Quél. Gas chromatography-mass spectrometry (GC-MS) was employed to analyze the composition of corn cob extracts resulting from various thermal degradation processes. The evaluation of decay resistance involved wood decay resistance tests and electron microscope observations. Results indicated that ethanol extracts from corn cobs heat-treated at 220 °C exhibited the strongest antifungal activity, accompanied by the highest extract yield. Additionally, the corn cob extracts also demonstrated inhibitory effects on the growth of Aspergillus niger, Escherichia coli, and Staphylococcus aureus. Chemical analysis revealed significant quantities of vanillin, squalene, and other compounds known for their antifungal or antibacterial activity in the corn cob extracts. Furthermore, wood treated with these extracts exhibited improved decay resistance, surpassing that against G. trabeum compared to T. versicolor. These findings suggest that thermally degraded corn cob extracts can be utilized as environmentally friendly wood preservative.

Coating paper with cellulose micro/nanofibrils (CMF/CNF) can improve the performance of paper packaging. However, the cost of the process is high due to the significant energy consumption during the CMF/CNF production process, which can be reduced through pre-treatment of cellulosic fibers. The objective of this work was, therefore, to evaluate the performance of CMF/CNF subjected to accelerated carbonation with different concentrations of calcium hydroxide (5% and 10% m/m) as a paper coating for packaging production in terms of spreading properties of adhesives, air permeability, and water absorption. The CMF/CNF coating was able to fill pores contained in the papers, with the treatment with 10% carbonation (CMF/CNF 10%) being the one that adhered best to the surface. There was a reduction in surface roughness from 1.35 ± 0.53 μm (uncoated paper) to 0.72 ± 0.21 μm (CMF/CNF 10%). Similarly, air permeability in the coated treatments was decreased, indicating good barrier properties and possible CO₂ absorption activity in the carbonated samples. Coated papers showed greater spreading of water, PVA, and PVOH. On the other hand, the Cobb value dropped from 41.55 ± 3.83 g m² (uncoated paper) to 26.26 ± 2.36 g m² (CMF/CNF 10%). CMF/CNF subjected to pre-treatment with accelerated carbonation have the potential for use as a coating material, being recommended for applications in food packaging and those that will be subjected to gluing/coating processes with other materials.

This work uses the M-theta method on a new proposed specimen called "I-specimen" for the numerical modeling of cracks on some tropical hardwoods in general and in particular on some Cameroonian woods. The finite element analysis of fracture in an orthotropic medium is developed. The fracture algorithm is introduced in a finite element software Cast3M and, with an incremental orthotropic formulation, the simulation of crack growth is computed. Using this method, stress intensity factors and energy release rate are calculated for Mode I and II failures. The energy release rate and stress intensity factors are numerically deduced using “I-specimen” to characterize three Cameroonian hardwoods under mode I and II loading for different crack growths. The specimen used has better characteristics than other samples generally used in the literature and its geometry is very simple to define. The proposal of a new geometry that can guarantee the reproduction of the different failure modes while exhibiting some stability of the crack parameters G and K during propagation was evaluated and compared to other specimens given by the fracture mechanics literature. For each fracture mode, the influence of the orthotropy rate parameters on the energy release rate was investigated.

The fire performance of buildings can be assessed through the thermal and charring characteristics of laminated bamboo lumber (LBL), due to its combustibility properties, which are akin to those of wood. This study employed Thermal Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Hot Disk techniques to ascertain the thermal conductivity, heat flow, and mass loss rate of LBL at elevated temperatures. Thermal conductivity initially rises, then falls, as the temperature increases from 25 °C to 280 °C across both grain directions, peaking at 100 °C. The thermal conductivity ratio of LBL, from parallel to perpendicular to grain, ranges from 1.93 to 4.00. A distinct peak in heat flow of LBL, ranging from 1.00 to 2.23, is observed as the temperature increases from 23 °C to 200 °C. Beyond 200 °C, the mass loss rate of LBL accelerates, driven by the pyrolysis of phenolic resin and decomposition of bamboo cellulose. The normal and nominal charring rates for LBL specimens were established based on the detachment of charring layers at furnace temperatures, adhering to ISO 834 standards. These findings may serve as a foundation for advanced fire performance analysis of LBL structures.

Virgin cork is a little-known, sustainable and relatively scarce raw material. However, its global output is expected to increase substantially as recent cork oak plantations are stripped for the first time. The work described here aimed to examine the factors underlying the mechanical properties of granulated cork, most particularly the type of cork (virgin or reproduction), and to develop a technique to deliver fast and accurate assessments of the effects of said factors. A batch of virgin cork was boiled, dried, ground and graded following standard granule classification procedures according to size and density. The resulting granulates were then compared with equivalent commercial-grade reproduction cork granulates. Physical variables (tapped density and moisture content) were measured and elastic recovery and Young’s modulus were used as proxies for mechanical properties. Image analysis was used to study the size, shape and colour of the cork particles. ANOVA results show significant effects of particle size, density class, type of cork and first and second order interactions between most variables. Density class clearly reached the highest level of significance, whereas the type of cork was less critical. A very strong correlation was found between granulates’ elastic recovery and their tapped density (R² = 0.98; RMSE < 1%). Likewise, greyscale imaging revealed a good adjustment between tapped density and grey level (R² = 0.84; RMSE = 24 g·l⁻¹). The primary conclusion was that the differences between virgin and standard cork granulates are small and should have no effect on less demanding applications. Image analysis is likely to prove useful in further, more in-depth studies.

Hybrid cross-laminated timber (CLT), being a derivative of generic CLT, offers the advantages of combining different materials to achieve improved performance. This study focused on investigating the withdrawal capacity of self-tapping screws (STS) in a hybrid CLT, i.e., cross-laminated timber-bamboo (CLTB), which is composed of high-density bamboo scrimber and low-density fast-growing Chinese fir lumber. The effects of screw diameters, penetration length and penetration sides on withdrawal performance were evaluated and the experimental results were further compared with the predicted values obtained from existing theoretical formulas. The experimental findings revealed a significant increase of 297% in withdrawal capacity when the outer layer of CLT is replaced with high-density bamboo scrimber. Compared to Chinese fir CLT, the penetration length of STS has a smaller influence on the withdrawal capacity of CLTB, with a minimum increase of 20.9% for CLTB, and a maximum increase of 119% for Chinese fir CLT. In addition, STS diameter significantly affects the CLTB withdrawal capacity by 66.4%, whereas the effect is 9.9% for Chinese fir CLT. When inserted into the narrow side, STS should only penetrate the transverse layer. The withdrawal capacity of bamboo scrimber transverse layer in type A was 260% higher than those of Chinese fir transverse layer in types B and C. Finally, significant differences were found between the predicted and experimental values for all three types of CLT. One of four existing theoretical formulas demonstrates improved accuracy in predicting the withdrawal capacity of CLTB.

Nowadays, using flame-retardant chemicals is gaining importance in chipboard production. Melamine resins to produce chipboard are preferred to provide flame retardancy properties with a cost of approximately 2.5 times the urea–formaldehyde (UF) resin. In this study, the UF resin to produce the chipboard was preferred due to its economical availability. To improve the flame retardancy properties of the chipboard, phosphate-based and inorganic flame retardants were used in the chipboards. In chipboard production, oak, pine, poplar, sawdust, urea–formaldehyde resin as adhesive, flame retardant chemicals like triphenyl phosphate (TPP), ammonium polyphosphate (APP), and calcium gluconate (CaG) were used. Flame retardant chemicals were added to chipboards in single and double compositions and prepared by pressing method. Mechanical (tensile, bending, and surface strength), physical (humidity, density, formaldehyde emission), and fire (limiting oxygen index (LOI), cone calorimeter, and UL-94 vertical) tests were performed on wooden boards. It has been observed that the use of different types of flame retardant and their combinations in chipboard does not significantly change the mechanical properties. It was seen that the free formaldehyde emission rate decreased by using flame retardant added compared to the control sample. The chipboard samples with added flame-retardant chemicals have entered the V-0 rating in the UL-94. LOI values of the chipboard samples containing 50% CaG-50% APP and 50% TPP—50% CaG were observed as 29.7% and 29.8%, respectively. Besides, the highest heat release rate (HRR) reduction was obtained in the chipboard sample containing 50% CaG—50% APP.

Wooden pallets can straightforwardly sustain fractures during storage and transportation. This shortens their service life. To minimize the economic losses caused by damage to wooden pallets, this study aimed to 1) investigate the falling damage behavior of wooden pallets by piezoelectric technology and acoustic emission (AE) and 2) evaluate a nondestructive method for damage-degree detection. The piezoelectric signal of the wooden pallets during the falling process was collected and analyzed for the variation law. The corresponding AE parameters were obtained when the different damage status occurred. It was observed that the peak voltage piezoelectric signal of the pallets decreased with an increase in the number of falls, and rebounded after damage occurred. The rebounding amplitude depended on the damage degree. The AE parameters of ringing count, energy, and amplitude reduced significantly as the pallet damage degree aggravated. The high-frequency proportion of the AE signal was observed to decrease as the damage strengthened. From undamaged to completely broken, the damage behavior of the wooden pallet generally underwent four stages: nondestructive, nail loosening, nail withdrawal, and the deck board off stage. The boundary of each damage stage could be clearly identified and read from the profile of the piezoelectric signal. Moreover, each stage could be effectively monitored and characterized by the AE parameters. Therefore, the combination of piezoelectric sensors and AE technology is capable of determining the structural health status of wooden pallets in use and predicting the remaining life.

This paper presents an experimental study on the flexural behavior of hybrid Pine-Birch Glued-Laminated Timber (GLT) beams. The study focuses on the performance of GLT beams with different lengths (2.1 and 2.8 m) and different compositions of birch (30 and 50%) and pine lamellas. The experiments were conducted using a four-point bending test and data were analyzed using Linear Voltage Displacement Transducers and Digital Image Correlation techniques. The results highlight that pure pine GLT beams exhibited brittle failure, while pure birch beams displayed a more ductile behavior. The hybrid GLT beams demonstrated a transitional behavior between the two. The presence of birch lamellas in the hybrid beams highlights the potential of these beams in structural applications, and significantly improves the global bending modulus of elasticity, bending strength, and flexural ductility compared to pure pine beams.

This paper details the manufacturing and dynamic performance evaluation of bamboo spur gears utilizing bamboo powder. The research involved a comparison between the accuracy and dynamic performance of a bamboo gear and a POM gear. Initially, a disk-shaped preformed bamboo product was created and transformed into a gear using a gear hobbing machine. Subsequently, the gear's accuracy was assessed, and the dynamic gear testing machine was employed to measure gear temperature, generation noise, and wear volume. The bamboo gear produced in this study exhibited accuracy nearly equivalent to that of the injection-molded POM gear. The wear volume of the bamboo gear was reduced by elevating the molding temperature. Furthermore, the bamboo gear fabricated at 200 °C, under torque conditions of 0.5 Nm and 1.0 Nm, with a range of revolutions from 500 to 1500 rpm, demonstrated comparable performance in terms of temperature, noise, and wear to that of a POM gear. However, gears comprised entirely of bamboo powder proved incapable of withstanding a load torque of 1.5 Nm. This limitation stemmed from the fact that the flexural strength of POM was 90 MPa, whereas that of the bamboo powder molding product was 60 MPa. Therefore, when fabricating a bamboo gear using bamboo powder reinforced with bamboo fiber bundles, it withstood up to 10⁷ rotations even under a load torque of 1.5 Nm.