The intensive utilization of agricultural residues, particularly wheat straw (WS), in particleboard production as an environmentally sustainable alternative to wood-based panels remains limited due to their poor bonding performance with conventional adhesives. Citric acid (CA) has recently gained increasing attention as a bio-based adhesive and appears to be a promising solution to overcome the bonding challenges associated with wheat straw However, there is limited information available on the combined effects of the moisture content (MC) of the mat and the adhesive dosage on the behavior of WS particleboard bonded with citric acid. Therefore, the objective of this study was to determine the optimal moisture content (MC) and the optimal CA content required to achieve satisfactory physical and mechanical properties without pretreating the straw particles. To this end, the resinized straw particles were oven-dried at different times intervals (2 h to 14 h) and temperatures (80 °C and 100 °C) to obtain mat with various moisture content (0,5 % - 20 %). The effects of adhesive content of 15 %, 20 %, 25 %, and 30 % (based on the dry mass of the straw) on the properties of the panels were also studied. The optimum moisture content of the mat before hot pressing was about 11%, and the corresponding panel exhibited flexural strength, modulus of elasticity and internal bond of about 12 MPa, 3700 MPa and 0,26 MPa, respectively, while the thickness swelling and water absorption after 24-hour immersion were 6,5% and 46 %, respectively. Increasing the adhesive content from 15 % to 30 % led to an increase in flexural strength from 9 MPa to 13 MPa and 117% in internal bond. However, a further increase in the adhesive content above 20 % did not lead to any statistically significant differences in the physical properties. In general, the results showed that due to the acidic nature of citric acid, it is possible to produce particleboard from wheat straw without pretreating the straw particles before use.
The chemical and surface changes induced by heat treatment can affect wood-adhesive interactions; however, limited attention has been given to the role of silane-based surface modification in enhancing the bonding and mechanical performance of heat-treated cross-laminated timber (CLT). Heat-treated Pinus sylvestris (Scots pine) and Abies bornmülleriana (Uludağ fir) were used as outer layers in the manufacture of three-layer CLT panels, and their mechanical properties were evaluated in this study. Heat treatment (HT) was carried out at 200 °C for 4 hours according to the Thermo-wood method. Layers were joined using one-component polyurethane-based adhesive. Some samples were treated with a silane-based coupling agent before bonding to improve bonding performance, and the effects of silane on bonding and mechanical properties were studied. Within this frame, tensile shear strength (TSS), bending shear strength (BSS), modulus of elasticity in bending (MOE), and tensile strength perpendicular to the surface (PTS) were measured. According to the results, silane modification generally improved mechanical performance, leading to a significant 74 % increase in PTS in Scots pine, while also affecting BSS (13 %) and MOE (7 %) in fir. In contrast, HT mainly altered bending-related behavior, most notably in Uludağ fir (BSS ≈ 10 %). Uludağ fir samples showed a higher BSS performance when compared to Scots pine ones. Overall, this study emphasizes that HT and silane modification can improve the mechanical performance of CLT, with effects varying by wood species and mechanical properties, providing valuable insights for the enhancement of low-durability wood.
This study investigates sustainable wood-plastic composites produced from heterogeneous furniture-factory waste sawdust and recycled polypropylene, with maleic anhydride-grafted polypropylene as a compatibilizer. Composites containing 0-40 wt% furniture-factory waste sawdust and 0 or 3 wt% maleic anhydride-grafted polypropylene were melt compounded and injection molded. Mechanical, physical, thermal, morphological, and biological performances were systematically evaluated. Increasing furniture-factory waste sawdust content significantly increased tensile and flexural moduli, while tensile strength, elongation at break, and impact strength decreased in the absence of maleic anhydride-grafted polypropylene due to weak interfacial adhesion. The addition of 3 wt% maleic anhydride-grafted polypropylene markedly enhanced mechanical performance, increasing tensile strength to 22,80 MPa and flexural strength to 43,58 MPa at 40 wt% furniture-factory waste sawdust (improvements of up to 42,9 % and 35,7 % respectively, relative to the uncompatibilized counterparts). Scanning electron microscopy analysis confirmed improved fiber encapsulation and reduced interfacial defects. Water absorption increased with furniture-factory waste sawdust content, while fungal mass losses remained below 2 % for all formulations. Thermal analysis revealed reduced initial degradation temperatures with furniture-factory waste sawdust and a broader decomposition range in the presence of maleic anhydride-grafted polypropylene. These results demonstrate that heterogeneous furniture-factory waste sawdust can be successfully incorporated into recycled polypropylene-based wood–plastic composites and that MAPP compatibilization significantly enhances composite performance. The findings provide valuable insights into the mechanical, physical, thermal, morphological, and biological characteristics of FFWS/rPP composites produced from real industrial waste streams.
The stem moisture content (MC) of living trees governs log weight, drying behavior, preservative uptake, and the susceptibility of timber to checking and decay, while also reflecting the response of the tree to climate. This study aimed to evaluate monthly variations in the stem MC of scots pine (Pinus sylvestris L.) and oriental beech (Fagus orientalis Lipsky) at two altitudes and examine the relationships between stem MC and environmental factors such as air humidity, temperature, and soil moisture. Stems were sampled monthly over a full annual cycle at two contrasting altitudes in the Andes. The cross-sections were partitioned into radial zones, and the air temperature, relative humidity, and soil moisture were recorded in parallel. Altitude and sampling month significantly affected stem MC for both species. The annual mean reached 57% at high altitudes versus 50% at low altitudes in Scots pine (Pinus sylvestris L.) and 70% versus 58% in oriental beech (Fagus orientalis Lipsky). Stem MC peaked in October-December and February-March, and fell to its annual minimum during summer. Radially, MC in Scots pine (Pinus sylvestris L.) increased from the bark towards the inner sapwood (mean ≈ 85%) and then dropped sharply to ≈ 35% in the heartwood, with the sapwood-heartwood contrast widening at higher altitudes. Oriental beech (Fagus orientalis Lipsky) showed a more gradual gradient (sapwood ≈ 79%, heartwood ≈ 55%), and at lower altitudes, the two zones became virtually indistinguishable in some summer months. Stem MC was positively correlated with soil moisture in both species. Oriental beech (Fagus orientalis Lipsky) additionally showed a positive correlation with relative humidity and a strong negative correlation with air temperature, whereas scots pine (Pinus sylvestris L.) MC was not associated with atmospheric variables. Therefore, altitudinal origin and felling month carry a predictable signal of log moisture, with direct consequences for transport, drying, impregnation, and defect management. January felling emerged as the most favorable window, and the dataset supports fire risk modelling, biomass energy calculations, and drought stress assessments for two ecologically and economically important species.
Axial compression in glued laminated timber (glulam) elements requires precise dimensioning that consider both the mechanical properties of material and effects of slenderness. In this context, current regulations present limitations by applying single values for stability (CP) and instability (Kc) factors, without considering the variations inherent to each species or the modes of buckling failure. This study addresses this issue using Populus deltoides glulam bars, with the aim of adjusting the parameters "c" and "(3c" involved in the calculation of these factors. Axial compression tests were carried out on a total of 320 samples within slenderness range of 30 to 100. Based on the experimental results of the 5th percentile failure stresses and fiber-parallel compressive strength, the optimal values of parameters "c" and "(3c" were determined. The Argentine regulation uses a single value of c = 0,9 for glulam members in practical application. However, this value highlights the need for adjustments to improve the dimensioning of compressed elements, resulting in a lower value of 'c'. On the other hand, the European criterion with (3c = 0,1 overestimates the compressive loads. However, the highest value of (3c, as determined by the experimental program, showed a better correlation for all slenderness ratios, reducing the overestimates of compression loads. The results confirm that adjusting the parameters 'c' and '(3c' significantly improves the accuracy of dimensioning and optimizes the design of compressed elements.
The increasing use of fast-growing plantations for structural purposes requires reliable criteria to assess the mechanical quality of new genetic materials using non-destructive methods. However, the high proportion of juvenile wood and the associated anatomical variability limit the effectiveness of these techniques when their structural basis is not well understood. The objective of this study was to analyze the anatomical variation of wood and its relationship with basic density and dynamic properties determined by acoustic resonance in five improved 11-year-old Eucalyptus grandis clones. Cell wall thickness and proportion, fiber length, microfibril angle, vessel diameter, and vessel frequency were evaluated, considering their variation among clones and within the stem. The results showed that vessel diameter and frequency can be used to identify mature wood, while cell wall proportion explained the variation in basic density. The microfibril angle showed a strong relationship with sound velocity and the dynamic modulus of elasticity. In conclusion, integrating anatomical analysis with acoustic resonance improves the interpretation of dynamic mechanical properties and provides an applied tool for the nondestructive structural evaluation and genetic selection of Eucalyptus clones.
Forest biomass is widely used as a biofuel for energy generation due to its renewable nature and favorable technological properties. However, information regarding the contribution of different tree components to biomass production and energy stock remains limited, particularly for fast-growing Eucalyptus species used in bioenergy systems. Therefore, this research aimed to evaluate the performance and energy stock of the stem and forest by-products in three Eucalyptus species. The data were collected from Eucalyptus benthamii (camden white gum), Eucalyptus dunnii (white gum), and Eucalyptus saligna (blue gum) trees at six-years-old, cultivated in the south of Brazil. The wood basic density, the wood calorific value and the dry biomass of the tree stems were determined, the dry biomass and the calorific value of the co-products (bark, leaves, and branches) were also determined. Finally, the biomass stock and energy yield of wood and by-products of the species used were determined. The stem contributed 66 % to 81 % in total biomass while the by-products 19 % to 34 %. The energy stock was over 360 GJ ha-1 and 81 GJ ha-1 for the stem and by-products, respectively. The stem showed the highest biomass stock and energy yield; however, forest by-products, particularly bark and branches, also presented substantial energy potential. These findings improve the understanding of biomass allocation and energy stock distribution among Eucalyptus tree components and demonstrate the importance of considering forest by-products as complementary feedstocks for bioenergy systems. Among the species evaluated, Eucalyptus benthamii showed the best overall performance, combining high biomass yield, favorable energy properties, and superior energy stock.
The performance of bonded wood products depends on wood properties and adhesive systems, resulting in variability in bonding. Although Pinus caribaea has been introduced in Brazil since the mid-20th century and presents potential for commercial use, there is still a lack of studies evaluating the bonding performance of its different varieties. In particular, comparative analyses of bonding behavior among varieties under different adhesive systems remain limited, especially for industrial applications such as edge glued panels. In the context, this study evaluated the bonding performance of three Pinus caribaea varieties affects using different adhesive systems (PVAc and EPI), for the production of edge glued panels using Pinus taeda as a reference. Wood samples from three varieties originating from 17- and 18-year-old experimental plantations were characterized in terms of physical and chemical properties according to COPANT and TAPPI standards. Bonding performance was assessed through finger joint (bending and tension) and edge bonding (shear strength) tests using PVAc and EPI adhesives, following ASTM and EN standards, with statistical analysis based on a factorial design. The results indicated that all varieties of Pinus caribaea exhibited low density, similar to Pinus taeda, although with higher extractive contents. All varieties achieved satisfactory performance in finger joint tests, meeting or exceeding ASTM requirements and showing results comparable to the reference species. In edge bonding, the varieties performed similarly or superiorly to Pinus taeda, with emphasis on the bahamensis variety. The EPI adhesive showed superior performance compared to PVAc. These findings demonstrate that intra-species variability does not limit bonding performance and confirm the technical feasibility of using Pinus caribaea varieties in the production of edge glued panels. The results contribute to expanding the industrial applicability of this species, supporting its use as an alternative raw material in the wood products sector.
In the forest production process, large quantities of lignocellulosic residues are generated, requiring strategies for their valorization and reuse. This study evaluated the physical, mechanical, and energetic performance of briquettes produced from Pinus sp. sawdust and from mixtures of MDF industry residues with Pinus sp. and Eucalyptus spp. sawdust. The briquettes were characterized in terms of apparent density, friability, and energetic properties, including proximate analysis and higher, lower, and net heating values. The results show that raw material composition has a direct influence on briquette performance. Briquettes produced from Pinus residues exhibited superior energetic properties, whereas those containing Eucalyptus presented higher apparent density and lower fines generation, indicating greater physical stability. The incorporation of MDF industry residues in combination with sawmill materials represents a viable alternative for producing briquettes with more balanced physical and energetic properties, contributing to the utilization and energy recovery of lignocellulosic residues.
This study addresses the need for a clearer understanding of how specific lignocellulosic substrates influence the performance of mycelium-based composites. Mycelium-based composites were prepared by combining Ganoderma lucidum (Curtis) mycelium with sawdust from Quercus sp. (oak) and Fagus orientalis (oriental beech) using a molding process. The aim was to evaluate the effects of wood species on the physical, thermal, and mechanical properties of these composites under controlled conditions. Physical properties (density), thermal stability (thermogravimetric analysis, TGA), and mechanical performance (compressive strength) were evaluated, and morphological characteristics were analyzed using scanning electron microscopy (SEM). The results showed that substrate type significantly influences composite performance. Oak-Ganoderma lucidum (curtis) composites exhibited superior physical and mechanical properties compared with beech-Ganoderma lucidum (curtis) composites, with a density of 239 kg/m³ and a compressive strength of 0.20 MPa. SEM analysis revealed a filamentous network of tubular hyphae of varying diameters surrounding the wood cell walls, while TGA results indicated similar thermal degradation behavior for both composites.The developed mycelium-based composites exhibited properties comparable to expanded polystyrene (EPS), highlighting their potential as sustainable alternatives for packaging and insulation. Overall, this study demonstrates that substrate composition plays a governing role in determining material performance and informs the design of bio-based composites.
Timber structures require a maintenance plan, along with periodic monitoring of their condition, to ensure their performance is maintained. The most common methods for wood inspection are those classified as non-destructive. Notably, visual inspection is one of the most frequently used methodologies in diagnostic engineering services. These methods lack the capacity to estimate or evaluate the structural resistance and integrity of the elements. The study used data from the inspection conducted in the Maloca building at the University of Brasília to estimate the structural resistance of its elements. The resistance estimate was based on a new resistance model using basic density. This model simplifies the estimative of different resistance parameters using only the basic density of the wood species. The resistance models adopted for various load conditions followed the guidelines of the Brazilian wood standard. The results show that the proposed methodology aligns with the performance and levels of degradation observed during the inspection. In conclusion, the methodology proves to be an important tool for estimating and monitoring the structural capacity of timber structures in inspection contexts without the need for destructive methods.
Fast-growing wood species are often characterized by low density, unsatisfactory mechanical properties, and poor biological durability. Therefore, various modification techniques have been tested to improve these disadvantages. The aim of this research work was to investigate the effects of densification of Salix alba (white willow) under hot pressing for 15 and 30 minutes on its physical and mechanical properties. Vapor pre-treatment for four and six hours was also applied to mitigate the negative effects of cracks and checks caused by breakage in wood cell wall under pressure. Markedly, separate sets of specimens were impregnated with aluminum oxide nano-suspension to evaluate if an increase in thermal conductivity would improve the properties of wood. The results indicated that densification significantly enhanced both the physical and mechanical properties of the wood. The four-hour vapor pre-treatment demonstrated the optimal improving results in both hot pressing durations. Though impregnation of specimens with the nano-suspension improved some properties (including spring back, hardness, and physical properties), most of the studied mechanical properties did not show any statistically significant improvement. Therefore, it was concluded that densifying willow wood for 15 minutes with a four-hour vapor pre-treatment yields optimal results. The enhancement in mechanical properties due to nano-aluminum oxide was not substantial enough to justify the associated costs, and thus, its use is not recommended for industrial applications.
This study addresses the limited availability of scientific data on the physical and mechanical properties of Detarium microcarpum (sweet detar) wood, which constrains its evaluation as a potential timber resource. An experimental characterization was conducted using wood samples obtained from three mature trees in Walateng-Goziir, Nandom Municipality, Ghana. The stems were sectioned into bottom, middle, and top portions to assess axial variation. Physical properties (moisture content, oven-dry density, volumetric shrinkage, and swelling) and mechanical properties (modulus of elasticity, modulus of rupture, compression parallel to grain, and shear strength) were determined at 12 % moisture content using standardized methods. The results showed significant axial variation (p < 0,05) across all measured properties. Moisture content increased from 13,78 % at the base to 16,35 % at the top, while oven-dry density decreased from 775,84 kg/m³ to 670,28 kg/m³. Mechanical properties also declined along the stem height, with modulus of elasticity decreasing from 6453,78 MPa to 5996,44 MPa. These findings provide empirical data that contribute to the scientific understanding of Detarium microcarpum (sweet detar) wood and support its evaluation as a lesser-used species with potential for timber applications.
This study examines the limited understanding of axial variation in color and hardness properties of Cedrus libani wood. In this context, the variation in color parameters and Shore D hardness across heart, heartwood, and sapwood sections was systematically investigated. Wood disc samples obtained from different axial positions of a 102-year-old tree were used to evaluate color properties, including lightness (L*), redness (a*), and yellowness (b*), together with hardness values. A total of 480 measurements were conducted across the three anatomical sections. The results demonstrated that both color and hardness properties vary systematically along the axial direction of the tree. Sapwood exhibited higher lightness values, whereas heart and heartwood showed comparatively lower L* values. Redness was more pronounced in heartwood and heart sections, while yellowness values were relatively similar across sections, with slightly higher values observed in the heart. In terms of mechanical properties, Shore D hardness increased from sapwood toward the center of the tree, reaching its maximum in the heart section. Additionally, axial differences were evident, with upper sections displaying higher hardness values compared to lower sections. These findings provide new insights into the axial variation of physical and mechanical properties in Cedrus libani wood, contributing to a better understanding of its material behavior. This knowledge is important for optimizing utilization strategies and improving performance-based classification of wood depending on its position within the tree.
Laminated bamboo lumber is a lignocellulosic composite with a wide range of applications in construction. Despite its growing use in structural applications, the structural behavior of laminated bamboo lumber has not been sufficiently investigated through advanced numerical modelling approaches, and the influence of species–adhesive combinations on bonding performance remains insufficiently understood. This lack of integrated numerical–experimental studies represents a critical research gap for the reliable structural analysis of bamboo-based elements. This work aimed to address this gap by numerically and experimentally evaluating laminated bamboo lumber elements submitted to three-point bending tests and by assessing the bonding performance of four distinct species-adhesive combinations (i.e. Dendrocalamus asper, Phyllostachys pubescens). The physical and mechanical properties of the lamellas were obtained from the experimental characterization of bamboo. A finite element modeling was developed to simulate the structural response, incorporating orthotropic behavior and physical non-linearity. The constitutive model adopted for bamboo followed Hill's criterion, simulating elastic-plastic behavior through bilinear curves. The numerical and experimental results showed good agreement, and the model was able to simulate the behavior of beams in bending, including the identification of critical stresses regions along the element. The species-adhesive combinations showed high delamination and shear strength at the glue lines. The results demonstrate the capability of the proposed numerical framework to predict the bending behavior of laminated bamboo lumber and highlight the importance of appropriate species–adhesive selection, contributing to the development of reliable design and manufacturing strategies for structural bamboo products.
The increasing accumulation of wood and plastic waste necessitates the development of sustainable, value-added materials such as wood-plastic composites (WPCs). This study investigated the feasibility of utilizing Falcataria moluccana (falcata) sawdust as a reinforcing filler in a recycled low-density polyethylene (LDPE) matrix. WPCs were fabricated via twin-screw extrusion using three sawdust particle sizes—P20R40 (0,840 - 0,400 mm), P40R60 (0,400 - 0,250 mm), and P60 (<0,250 mm)—at blending ratios of 30:70 and 40:60 (sawdust:LDPE, by weight). Physical properties, including relative density, moisture content, water absorption, and thickness swelling, were evaluated alongside mechanical performance according to ASTM standards. The results demonstrated that the incorporation of sawdust produced WPCs with physical stability and hygroscopic properties comparable to or superior to those of the pure recycled LDPE control. Mechanical analysis revealed a significant reinforcement effect; the inclusion of sawdust enhanced both the tensile and flexural strength and modulus of the composites. Specifically, finer sawdust particles (<0,250 mm) and a 30:70 sawdust-to-LDPE ratio yielded the optimal overall mechanical performance. However, impact strength tests indicated that the wood filler increased material brittleness, as the neat LDPE significantly outperformed all WPC treatments in energy absorption. Overall, this study concludes that falcata sawdust is a viable natural fiber for reinforcing recycled LDPE, offering a sustainable pathway for upcycling waste into rigid composite materials, provided that applications account for the inherent reduction in impact resistance.
Understanding anatomical responses in various tree species to fungi causing gummosis is limited. In this article, wood samples from an apricot tree (Prunus armeniaca) with severe gummosis and branch dieback were studied macroscopically and microscopically to determine the response of woody tissues to the infection. The fungi species Valsaria insitiva was determined visually by the signs of the disease and by cultivating clean cultures. Macroscopical examination found wedge and arch shaped necroses running along the growth rings under the bark necroses and sunken lesions. Microscopical examination found small black fruiting bodies of the fungus on the bark. Vessels and libriform fibers were blocked by gum, thus blocking the water and nutrients flow to the branches and causing the dieback. Sites with fungi infection were compartmentalized and this was discussed according to the CODIT model. Oxidized ray parenchyma was visible in tangential and cross sections of the wood; calluses were covering the infected areas. Compartmentalizing the infections by releasing gum into vessel lumina, restricting the flow of nutrients and water in the tree thus drying it out is a way of protection of the tree against the pathogens. Apoplexy of apricots is an acute disease and can be very extreme in some cases. The studied tree had signs of compartmentalization of the infection, but the infection was spreading faster than new tissues were formed.
Terahertz time-domain spectroscopy (THz-TDS) combined with chemometric techniques was investigated as a non-destructive method for species classification in wood samples from four different species. For this purpose, samples were introduced into the THZ-TDS spectrometer chamber purged with dry nitrogen, and spectra were collected at wave intervals from 0,1 THz to 10 THz to evaluate the samples. It was obtained that in the range between 0,1 THz and 1,7 THz, there is higher differentiation of the samples, being this the best range to generate classification models. After the chemometric analysis, the Support Vector Machine algorithm achieved an accuracy rate of 91 % in classifying the four wood species. Finally, it was demonstrated that THz spectroscopy can be used for quantitatively complex natural organic materials such as wood.
Brazil has a vast area of planted forests, which makes it the second largest producer of bark as a by-product. Several alternatives have been studied for the reuse of this residue; however, little attention has been given to the use of forest residues, such as bark, in the energy sector for briquette production and to the main variables involved in this process. The aim of this work was to evaluate the viability of producing briquettes from Eucalyptus bark. The briquettes were produced and characterized according to American and Brazilian standards, evaluating two different particle sizes and the addition of cassava starch. The briquettes produced from Eucalyptus bark show potential for use, although attention should be paid to their ash content. In particular, the treatment produced with a 12-mesh granulometry and the addition of cassava starch showed the best chemical, energetic, physical, and mechanical properties. The production of briquettes from Eucalyptus bark demonstrates the feasibility of reusing forest residues for bioenergy production.
It is still a challenge to manufacture traditional three-way Zongjiao mortise-and-tenon joints using modern CNC-based machines. This study aimed to improve the structure of the Zongjiao mortise-and-tenon joint, a commonly used three-way corner joint in wood furniture, to better align with modern manufacturing practices. First, four improved mortise-and-tenon joint types were designed, and their appearances were evaluated. Secondly, mechanical tests and numerical analyses were conducted to compare the four improved types and two previous types using bending strength and load difference ratio (DR) between the two horizontal members of the joint. Subsequently, the machinability of all types of joints was evaluated through processing time (PT), cutting force (CF), and number of effective programs (NEP). The results showed that the maximum bending strength of the Zongjiao M-T joint was observed in Type D, and the load DR between the two horizontal members was 13,79. The improved Type D has the lowest milling CF of 182 N and the minimum PT of 32 minutes with the least NEP. Through a comprehensive analysis of all the above indices evaluated, it was found that the improved Type D of Zongjiao mortise-and-tenon joint was superior to others, considering appearance, mechanical strength, and machinability. This study provided a paradigm for optimizing wood furniture joints, which can also be applied to other wood products.
