ABSTRACTThe structural use of wood from young trees requires gluing smaller timber pieces to form large elements. In young Eucalyptus timber of structural dimensions, knots do not significantly diminish the mechanical properties, yet their influence on wood adhesion has not been widely studied. Therefore, the aim of the study was to assess the influence of knots on the bond quality of face-glued wood from young E. grandis. Wood from seven-year-old E. grandis trees was tested in shear on the bond-line (polyurethane adhesive) using paired samples of knot-containing and clear wood samples. Knot features did not correlate with shear strength or wood failure percentage. Knot-containing samples had a lower percentage of wood failure (5.8%), but the same shear strength as clear wood samples. Below a wood density of 650 kg m−3, clear and knot-containing wood behaved similarly, but above this value, knots influenced wood adhesion negatively. By simulating glulam beams with high-density wood on the outer lamellas, it was possible to show that shear stress on those bond-lines is lower than the minimum shear strength observed on dense knot samples. Hence, lower adhesion caused by knots on denser wood probably does not represent a significant problem for glued laminated products from young Eucalyptus grandis trees.

ABSTRACTWood is a traditional roofing material in Europe and other parts of the world. In the seventeenth century, wooden roofing was generally used on more important buildings, but today it is mainly used on huts and houses in the Alpine regions. As wooden roofing is expensive, we investigated the possibility of extending the service life of the roofing through material selection and details. The roof of the Golobar cable yarding was covered with shingles made of spruce (Picea abies) and larch (Larix decidua). Part of the spruce roofing was thermally modified and/or treated with a water-wax emulsion. On the underside, we cut grooves in selected roof shingles to increase the specific surface of the wood and to accelerate drying after rainfall. In addition, wood moisture monitoring sensors were installed on the roof shingles. Based on three years of the wood moisture content measurements, it can be concluded that among shingles made of untreated spruce wood, the highest moisture content was recorded for shingles with a rectangular cross-section without additional grooves. The additional grooves positively affected the moisture performance of wood. Treating the wood with Silvacera wax had an even more pronounced effect on the moisture content of the shingles than the grooves.

ABSTRACTThe aim of this research was to evaluate the bond-line strength and chemical changes of pine (Pinus taeda) and itauba (Mezilaurus itauba) joints welded by rotary friction and the use of the internal standard method with Rietveld refinement for the determination of the absolute cellulose crystallinity of wood samples. The specimens were composed of itauba dowels welded in substrates made of pine and itauba wood. The shear engaged by tensile pullout of the dowels was determined by mechanical tensile tests. Furthermore, macrostructural evaluation of the specimens and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction (XRD) tests were performed. The cellulose crystallinity was determined quantitatively by the internal standard method with Rietveld refinement and compared with the Segal and the deconvolution qualitative methods. The results reveal that itauba dowels welded in itauba substrates produce stronger joints (0.81 MPa) and slighter chemical changes than in pine substrates (0.62 MPa). The welded bond-line of itauba dowel and pine substrate has greater cellulose crystallinity than that of itauba dowel and substrate. The cellulose crystallinity is qualitatively consistent for the three applied methods, however, quantitatively, there are divergences between them.

ABSTRACTMoso bamboo (MB), carbonized moso bamboo (CMB), natural color bamboo scrimber (NBS), and dark color bamboo scrimber (DBS) were subjected to Poria vaporaria (PP), Gloeophyllum trabeum (GT), Coriolus versicolor (CV) and Trametes versicolor (TV) in laboratory experiments. The differences in surface chromaticity and mass loss of four samples before and after decay were compared. The results showed that the decay resistance of DBS after four wood rot fungal infections reached grade I, and DBS had the best decay resistance among the four samples. MB had the worst decay resistance among the four samples. After being infected by four kinds of wood rot fungi, the color of MB and NBS changed significantly, as the brightness decreased significantly. The red-green axis color index and yellow–blue axis color index of MB and NBS infected by PP, GT, CV, and TV showed significant increases compared to those of untreated samples. The chroma values of MB and NBS increased significantly after the decay test. SEM analysis showed that after the brown-rot test, the hyphae of GT entered the MB vessels and the parenchyma cells through the pits in the vessel, causing the cell structure to be destroyed.

ABSTRACTThis study investigates the characteristics of particles recycled from waste particleboards and the factors that lower the physical and mechanical properties of recycled panels. Hot-pressing with/without adhesive and hydrothermal treatment are applied to the fresh wood particles, and the morphology, surface properties, and mechanical strength of the particles after treatments are investigated. The results indicate that hot pressing causes the densification of particles, resulting in reduced wettability, a low compaction ratio, and a loss of particle strength; thus, the mechanical properties of recycled panels are significantly weak. The residual adhesive also affects the wetting of the adhesive. Hydrothermal treatment helps to recover the cellular structure and compaction potential of recycled particles, thus improving the mechanical properties of recycled panels. The deteriorations in particle qualities are mainly due to densification and residual adhesive, and hydrothermal treatment helps to recover the structure and remove the resin on the recycled particles.

ABSTRACTThe design of timber floors is often governed by the fulfilment of serviceability requirements concerning human-induced vibrations. The stiffness and modal properties (eigenfrequency and damping ratio) are essential parameters for the design verification of timber floors against vibrations. In the present paper, a series of experimental tests (static tests, impact hammer modal tests, forced resonant vibrations and free vibrations) on a long-span, stressed-skin, timber floor are presented, together with predictions using a Finite Element model. Moreover, the effect of additional mass was investigated by adding extra weight in the mid-span. The modal properties obtained by different methods were in good agreement. The measured damping ratios were low, especially for the first two modes (of the order of 0.7% for the first mode and 0.8-1.0% for the second mode). The FE predictions were in good agreement with the experimental results regarding stiffness and the first two eigenfrequencies. However, the FE model overestimated the third eigenfrequency and underestimated the steady state accelerations observed under forced vibrations. A stiffness-proportional Rayleigh damping was found to describe best the energy dissipation.

ABSTRACTZeolitic imidazolate frameworks (ZIFs) were considered to be one of the most promising emerging nanoporous adsorbents capable of efficiently removing a variety of heavy metals ions from wastewater. However, due to the powdered crystalline state, easy aggregation and instability of ZIFs materials, their actual large-scale applications in water matrices are significantly hindered. Compounding ZIFs with self-supporting porous wood aerogel (WA) to obtain advanced composites is excepted to further enhance their adsorption performance with higher practicability. Herein, a novel Zeolitic Imidazolate Framework-67 (ZIF-67)@wood aerogel (denoted as ZIF-67@WA) adsorbent for efficient capture of Cu(II) ions was successfully fabricated via in situ growth of Cobalt-based ZIF-67 particles onto the WA scaffold. Benefiting from the integration of unique three-dimensional porous structures and abundant accessible active sites, the obtained ZIF-67@WA hybrids exhibited fast adsorption kinetics and the maximum adsorption capacity towards Cu(II) calculated from the Langmuir model was 254.84 mg g−1. The adsorption kinetic and isotherm studies were consistent with pseudo-second-order model (R2 = 0.991) and Langmuir model (R2 = 0.973), indicating the adsorption of Cu(II) was a monolayer chemisorption process. This work proposed a new route for designing and constructing functionalized MOF@biomass hybrid materials for heavy metal wastewater treatment.

ABSTRACTThe effects of different urea-formaldehyde (UF) resin and paraffin contents on the physical and mechanical properties of medium-density fibreboards (MDF), and their relationship with air and liquid permeability were investigated. The MDF panels were fabricated with three UF resin and three paraffin contents, based on the dry fibres. The physical and mechanical properties of the MDF panels were determined in accordance with the ASTM D1037-99 standard. The highest (3.7 × 10−13 m3 m−1) and lowest (1.2 × 10−13 m3 m−1) air permeability values were found in the panels manufactured with the lowest resin and paraffin contents and the highest resin and paraffin contents, respectively. A significant inverse relationship was found between the permeation of both fluids (air and water) through MDF panels versus resin and paraffin contents. Higher UF-resin contents made wood fibres be stuck more strongly together, limiting the flow of fluids. The water-repellent property of paraffin contributed to the decrease in liquid permeability as paraffin content was increased. Markedly, the coefficients of determination of the regression models between permeability and physical properties were found significant. The mechanical properties also showed significant regression with air permeability. It was concluded that air permeability can be considered a reliable property to predict water absorption behaviour in MDF.

ABSTRACTWood is usually processed into various spaces and used in buildings, packaging and furniture. Dynamic moisture sorption and humidity response inside wooden space to sinusoidally changing external relative humidity (RH) were demonstrated by using a self-assembly device, which simultaneously recorded moisture content (MC) and RH changes. Wood has hierarchical structures, which provided the basis of moisture sorption and further influenced RH inside. Internal RH changed sinusoidally, similar to external RH and MC. During internal and external moisture exchange, water molecules experienced dynamic compound actions, including moisture gradient pressure, the attraction of sorption sites and water molecules and diffusing hindrance. Consequently, MC and internal RH exhibited dynamic phase lag of over 0.39 radian. Meanwhile, moisture sorption was higher for thinner wood, especially in a longer cyclic period since more water molecules interacted with sorption sites with less diffusing hindrance. Correspondingly, the humidity change was lower inside thicker wooden spaces in a shorter period. The average internal RH and amplitude decreased by 5% and 83.7%, respectively. Dynamic humidity change hysteresis existed and showed positive relation to the cyclic period but inversely with wood thickness. The study helped better understand dynamic moisture sorption and humidity change in wooden space and facilitated the better application of wood in human life.

ABSTRACTThe efficient and energy-saving drying process during the production of bamboo scrimber with preserved performance remains challenging. Herein, varying post-impregnation drying temperatures and times were applied first to study the drying rate and energy consumption of impregnated bamboo bundle in a heat pump dryer. Then curing activity of phenolic resin (PF), the physical and mechanical properties of bamboo scrimber were investigated. The results showed that the drying rate was remarkably related to the drying temperature, whereas energy consumption was more dependent on drying time. Drying at 60°C using the heat pump dryer enhanced the drying efficiency by 33-67% and obtained 51-63% energy saving compared with the drying processes in enterprises. Besides, the curing activity of PF was well maintained during drying at various temperatures and times, hence satisfactory physical and mechanical properties of bamboo scrimber were achieved. As a result, drying with heat pump technology at 60°C was the optimal post-impregnation drying condition, and is applicable to practical bamboo scrimber production.

ABSTRACTThe rapid urbanization and economic expansion have increased the negative consequences of environmental noise pollution. The sound that originates from various sources comes from distinct spectrums. To address the aforementioned issue, acoustic absorbers were 3D printed with varying infill patterns to absorb sound across a wide range of frequencies. Acoustic absorbers made of polylactic acid/polyhydroxyalkanoates-wood fibers (PLA/PHA-WF) were fabricated using Fused Deposition Modelling (FDM) technology, and their physical, mechanical, water absorption, biodegradation, and acoustic characteristics were measured and discussed. Acoustic absorbers printed with different infill patterns have a slight difference in density due to the size of the pores and the contact sites exhibited by the infill pattern. As a result, acoustic absorbers printed with varying infill patterns allow sound waves to enter and absorb sound at distinct spectrum levels. Modifying the infill pattern also had an effect on mechanical, water absorption, and biodegradation properties with minor deviations. The proposed biodegradable acoustic absorbers made of natural fiber composites and manufactured by FDM can be installed on building walls or roofs depending on the required acoustic absorption spectrum.

ABSTRACTThermo-mechanical densification of sawn timber results in improved mechanical properties, but densified wood remains a fairly expensive niche product, partially because of high-cost batch processing. Densification in a continuous process could address this problem and was shown to be possible in previous research. The outcomes were limited to proofs-of-concept, partially due to insufficient cooling capabilities of the used densification equipment, resulting in high spring-back. Therefore, a novel continuous process using a belt press to densify full-sized sawn timber has been conceived. The press ensures almost constant contact between the wood and the heating and cooling elements. The study aimed to analyse how the processing temperature, speed and compression ratio affected the density profile, spring-back, set-recovery, Brinell hardness, and bending properties. Results showed a density increase concentrated close beneath the surface in contact with the heating element and approx. 20% spring-back. Belt speeds above 2 m min−1 caused higher spring-back due to the reduced contact time between the wood and the heating element. Brinell hardness increased by up to 250% at a compression ratio of 27% while bending properties were unaffected. Belt temperature and speed were shown to be critical factors to consider for the future optimisation of the belt-press process.

ABSTRACTDetermining the target market constitutes one of the most important strategic decisions. During the target market selection, many factors need to be considered and evaluated systematically and the most accurate choice is required to be made. In this study, the target country market selection is made for the fibreboard industry, which is one of the main sectors of the forest products industry in Turkey. For this purpose, multi-criteria decision-making (MCDM) methods, which are considered the most appropriate decision-making techniques among alternatives with many criteria, are utilised. AHP, VIKOR and TOPSIS methods are used to identify the most appropriate target market. Furthermore, a hybrid mathematical model including goal programming is proposed. And to handle ambiguity and fuzziness in international market decisions, a fuzzy goal programming model is developed. Economic, risk, supply chain and sectoral strategies are determined as the main criteria. 29 target countries are identified by including the countries ranking first in the exports of Turkey in the sector and the target countries determined by Ministry of Development. Target countries are ranked with MCDM. The rankings of the solution are compared via correlation tests. The first 10 countries are selected for the target market by employing the proposed models.

ABSTRACTThis study is concerned with establishing a uniform experimental protocol for the determination of phenolic extractives, which play an essential role in the durability of the wood of selected species included in the field tests. European larch (Larix decidua), Norway spruce (Picea abies), Scots pine (Pinus sylvestris), European oak (Quercus sp.), sweet chestnut (Castanea sativa), and black locust (Robinia pseudoacacia) were included in the study. Extraction yield data were collected for extraction in a Soxhlet apparatus using common polar extraction solvents (ethanol, acetone, methanol, water) and for single static extraction cycles in accelerated solvent extraction (ASE). The suitability of the solvents and the appropriate extraction conditions were evaluated based on the results of gravimetric analysis of hydrophilic extractives, spectrophotometric analysis of total phenols, and chromatographic analysis using high-performance liquid chromatography. Extraction in the ASE system with methanol proved to be a quick and accurate way to prepare samples for chemical analysis of extractives of selected wood species. With the chemical monitoring of targeted phenolic extractives in wood subjected to leaching, we propose a novel protocol suitable also for for measuring the effects of weathering on the natural durability of wood in future studies.

ABSTRACTThis study aimed to reveal the changes in Fe concentration and colour in the wood obtained from selected tree species: Pinus sylvestris L., Picea abies (L.) H. Karst., Pseudotsuga menziesii (Mirb.) Franco, Juglans regia L., and Acer platanoides L. at different stages of the hydrothermal treatment with additive Fe2O3 in combination with tannic acid. The study results showed that wood obtained from deciduous and coniferous trees responded slightly differently to the duration of treatment, and the temperature applied. In all cases, the higher Fe concentrations were found the outer wood layers, which directly contacted the modifying solvent. In deeper wood layers, Fe concentrations gradually decreased. Higher Fe concentration determined darkening of the colour. The longer treatment time and the higher temperature caused the higher Fe concentrations in all wood layers. For the most reliable and efficient technological process, the treatment temperature could be optimised up to 90°C, when the wood is exposed to the solvent made of water with the addition of Fe2O3 and tannic acid. The duration of the full hydrothermal process could be optimised up to 120 h for the wood from coniferous species, and it could be prolonged up to 150–240 h for deciduous species.

ABSTRACTThe objective of this study was to assess the potential gains in log processing yield when integrating sawmill and engineered wood products manufacturing, a process which enables the use of random board widths and higher wane allowances than normal. The simulation was utilized and validated against real log sawing. The validation study showed that simulations consistently over-estimated the actual volume recovery by 2.1%. Simulation results showed that logs with smaller diameters returned higher recovery increases when adopting an increased wane strategy compared to large-diameter logs. When combining both increased wane and random width strategies, the recoveries were the highest. Using a weighted average of log classes (according to a common log size distribution in South African sawmills) an increased wane strategy returned higher recovery (11.0%) than a random width strategy (2.0%), but a combined strategy (13.0%) was the most efficient. The gains in volume recovery presented in this study showed that it is worthwhile to consider the integration of engineered products manufacturing in primary log processing using random widths strategy combined with higher wane allowance. For better use of the raw material, the maximum wane that engineered products can allow without compromising its strength and stiffness must be further investigated.

ABSTRACTAs an eco-friendly material, recycled aggregate concrete (RAC) has lower strength than natural aggregate concrete. To improve the compressive behaviour of RAC, a bamboo composite tube (BCT) is selected as the confining jacket. A total of 60 specimens were tested, which included 45 bamboo composite tube-confined recycled aggregate concrete (BTRAC) specimens and 15 unconfined RAC specimens. To investigate the influence of the replacement ratio of the recycled aggregate and thickness of BCT, a series of analysis were conducted on the failure modes, stress–strain response, dilation behaviour and effect of the replacement ratio. Test results showed that the axial stress–strain curves of the BTRAC specimens were approximately bilinear. The confinement ratio was found as the primary factor affecting the mechanical properties of the BTRAC column. Owing to a greater confinement stiffness in a thicker BCT, the slope of the second stage in the stress–strain curves increased correspondingly. Although the change in replacement ratio of recycle aggregate resulted in different dilation behaviours, the influence was regarded as limited on the BCT confinement effectiveness. Moreover, the ultimate stress, the ultimate strain, and the axial stress–axial strain curves of BTRAC specimens were calculated by the relevant models for FRP-confined concrete to evaluate their applicability.

ABSTRACTThe demand for construction timber is continuously increasing, due to its favourable characteristics. However, the adequate protection of wood is key to its successful use, as it is flammable and susceptible to biodegradation. Given that thermal modification enhances the durability of wood, and mineralisation with CaCO3 considerably improves its fire properties, it is worth considering the combined effects of the two methods.European beech (Fagus sylvatica) was selected to determine the effects of a) thermal modification, b) mineralisation through the in-situ formation of CaCO3, and c) a combination of the two procedures, on resistance to decay fungi, reaction to fire and the mechanical properties of the wood. Microscopic analysis and comparisons of the samples before and after exposure to fungi were also conducted.Mineralised wood generally had a slightly alkaline pH value and higher equilibrium moisture content, while thermal modification lowered the equilibrium moisture content. The present study demonstrated the combined effect of thermal modification and mineralisation: the best response to fire as well as resistance to fungi was achieved when the two treatments were combined. Results from the Brinell hardness and three-point bending tests indicate that both modification procedures can slightly impair the mechanical properties of the wood.

ABSTRACTSelecting individuals in breeding programs for pulp production, the physical and chemical wood traits must be considered in the genotype selection. In this study, trees from hybrid progeny tests of Corymbia torelliana x Corymbia citriodora (CTOxCCT) and progenies of Eucalyptus dunnii (EDU) were investigated. Sawdust of genetically selected standing trees was collected, classified and prepared for near infrared (NIR) spectra readings. The chemical properties of the selected trees were determined through kraft pulping. Predictive models for each property were developed based on the reference data and NIR spectra. Two approaches for models were developed. The first approach, models were fitted with 25 samples of CTOxCCT, and in the second approach, models were fitted using 61 samples (25 of CTOxCCT and 36 of EDU). The estimated R²cv values were 0.60 and 0.73 for basic chip density, 0.37 and 0.65 for extractive contents, 0.56 and 0.53 for total lignin contents, 0.63 and 0.66 for S/G ratio, and 0.52 and 0.77 for screened pulp yield for the first and second approaches, respectively. All developed models have potential for ranking trees in breeding programs. NIR spectroscopy can potentially be applied as a high-throughput field phenotyping tool where thousands of varieties need to be evaluated.

ABSTRACTThis case study aims to determine factors that cause defects in plywood products using failure mode effect analysis (FMEA) parameters. It also analyzes prevention strategies against plywood product defects in the plywood industry in Indonesia. The study involved 9 participants who are employees of different divisions. The research data were collected from direct observations of the plywood production process, analysis of documents recording plywood product defects, and focus group discussions. Based on the results of thematic analysis using FMEA parameters, this study identified five factors that significantly contribute to the failure of plywood products, as indicated by their highest Risk Priority Number (RPN) values. These factors are: (1) lack of employee discipline, (2) unstable machine temperature and excessive machine capacity usage, (3) waste on the veneer surface, (4) excessive adhesive wastage, and (5) inefficient work performance of the employees. The study suggests that the FMEA concept employed to capture product defects can potentially be used to explore employees’ perspectives and their lived experiences in plywood production. In addition, FMEA can provide improvement feedback to prevent defects in plywood products.