Search Results (417)

This study aims to develop high-performance biocomposites for structural applications using kenaf, bagasse, hemp, and softwood fibers bonded with phenol-formaldehyde (PF) and phenol-urea-formaldehyde (PUF) adhesives, commonly used in particleboard manufacturing. A simple, low-cost fiber treatment was applied by adjusting the fiber pH to 11 and 13 using a 33% NaOH solution, following standard protocols to enhance fiber–adhesive interaction. The effects of alkaline treatment on the chemical structure of bagasse, kenaf, and hemp fibers were investigated using Fourier Transform Infrared Spectroscopy (FTIR) and correlated with composite mechanical performance. PF and PUF were applied at 13% (w/w), while polymeric diphenylmethane diisocyanate (pMDI) at 5% (w/w) served as a control for untreated fibers. The fabricated panels were evaluated for mechanical properties; modulus of elasticity (MOE), modulus of rupture (MOR), and internal bond strength (IB), and physical properties such as thickness swelling (TS) and water absorption (WA) after 24 h of immersion. FTIR analysis revealed that treatment at pH 11 increased the intensity of O–H, C–O–C, and C–O bands and led to the disappearance of the C=O band (~1700 cm⁻¹) in all fibers. Bagasse treated at pH 11 showed the most significant spectral changes and the highest IB values with both PF and PUF adhesives, followed by kenaf at pH 13, exceeding EN 312:6 (2010) standards for heavy-duty load-bearing panels in dry conditions. The highest MOE and MOR values were achieved with kenaf at pH 11, meeting EN 312:4 (2010) requirements, followed by bagasse, while softwood and hemp performed less favorably. In terms of thickness swelling, bagasse consistently outperformed all other fibers across pH levels and adhesives, followed by Kenaf and Hemp, surpassing even pMDI-based composites. These results suggest that high-pH treatment enhances the reactivity of PF and PUF adhesives by increasing the nucleophilic character of phenolic rings during polymerization. The performance differences among fibers are also attributed to variations in the aspect ratio and intrinsic structural properties influencing fiber–adhesive interactions under alkaline conditions. Overall, kenaf and bagasse fibers emerge as promising, sustainable alternatives to industrial softwood particles for structural particleboard production. PF and PUF adhesives offer cost-effective and less toxic options compared to pMDI, supporting their use in eco-friendly panel manufacturing. FTIR spectroscopy proved to be a powerful method for identifying structural changes caused by alkaline treatment and provided valuable insights into the resulting mechanical and physical performance of the biocomposites. Full article

This study investigates the use of suberinic acid residues (SARs), derived from birch outer bark, as a bio-based additive in high-density fiberboard (HDF). Boards with target densities of 800 kg m⁻³ were produced with SAR contents of 0, 1, 5, 10, 20, and 50%. Standardized tests evaluated mechanical properties: screw withdrawal resistance, modulus of elasticity, modulus of rupture, and internal bond, as well as moisture resistance through surface water absorption, water absorption, and thickness swelling. Density profiles were also analyzed. SAR content influenced HDF performance in a concentration-dependent manner. The most notable improvements in mechanical properties occurred at 5% SAR, where fine particles likely enhanced internal bonding and stiffness. However, higher SAR levels led to reduced mechanical strength, possibly due to an excessive particle surface area exceeding the adhesive’s bonding capacity. Moisture resistance declined with increased SAR, attributed to its hydrophilic nature and process parameters, although SAR-modified boards still outperformed those with other biodegradable additives like starch. SAR also affected the density profile, improving core densification at moderate levels. Overall, SAR shows potential as a renewable additive for enhancing HDF performance, particularly at low concentrations, balancing mechanical strength and environmental benefits. Full article

Bamboo is a lignocellulosic material characterized by its high hygroscopicity, which refers to the ability of material to absorb and retain moisture from the surrounding environment. This attribute could adversely affect its dimensional stability and resistance against deterioration agents. Thus, a study was conducted to investigate the effect of thermal modification on the hygroscopic, mechanical, and chemical properties of three-year-old Gigantochloa scortechinii, a native and highly exploited bamboo species in Malaysia. Overall, heat treatment effectively reduced the equilibrium moisture content and improved the dimensional stability of bamboo, with samples treated at 210 °C exhibited the most significant moisture resistance of up to 95.6% anti-swelling efficiency (ASE). The heat-treated bamboo exhibited an improvement in modulus of elasticity (MOE) at intermediate temperatures (170–190 °C) whereas modulus of rupture (MOR) declined at 210 °C. Chemical analysis indicated that a significant reduction in hemicellulose content and a relative increase in α-cellulose and lignin contributed to the improved moisture resistance of heat-treated bamboo. The results demonstrate the viability of heat treatment in producing quality thermally modified bamboo as an alternative raw material for construction materials and furniture manufacturing, thereby contributing to the development of Malaysia’s bamboo industry. Full article

The selection of tree species for afforestation in Mediterranean environments involves challenges related to adaptability, impact on soil properties, and overall environmental quality. Cupressus lusitanica has been recognized for its rapid growth, environmental resilience, and versatile applications, positioning it as a promising candidate for these regions. Although it has been used for afforestation in Northeast Portugal since the 1990s, no comprehensive studies have evaluated its performance under local conditions. To address this knowledge gap, this study assessed a 14-year-old C. lusitanica stand in Northeast Portugal. The wood’s anatomical, physical, chemical, and mechanical properties, as well as biomass production, were evaluated. The species showed superior radial growth and adaptability compared with other species under similar environmental conditions. Despite exhibiting lower fiber length (1.6 mm) and basic wood density (404 kg/m³), shrinkage values fell within the typical range for softwoods. Nevertheless, a marked tendency for warping was observed. The extractive content was relatively high (5.1%), with the ethanol-soluble fraction being predominant (3.6%). Mechanical tests revealed low values for both Modulus of Elasticity (MOE) (3592.5–3617.1 MPa) and Modulus of Rupture (MOR) (57.7–68.9 MPa), with both properties significantly influenced by knot presence. Given the results obtained, the species C. lusitanica, despite its low wood density and potential limitations in use, exhibits remarkable growth and adaptability, which confer a high potential for biomass production and carbon sequestration, as well as potential applications of its wood in reconstituted panels and fiber- or particle-based boards. Full article

The scarcity of high-quality wood encouraged the development of various technological processes for joining wood. The finger joint is one of the most widespread technological processes for wood joining. This study aimed to determine the effect of steaming and heat modification of beech wood, as well as the type of adhesive, on the mechanical characteristics of finger joints. Samples made from un-modified beech, steamed-treated, and heat-treated beech wood were bonded with polyvinyl acetate (PVAC), non-structural, and structural polyurethane (PUR) adhesives. Compressive tests on wood materials were used to evaluate their mechanical performance. The finger joint samples were tested for their bending performance. Modulus of rupture, modulus of elasticity, and compressive strength were calculated. An analysis of variance (ANOVA) was conducted to evaluate the impact of wood modification type and adhesive used on the mechanical characteristics of the finger joints. According to the results of this study, it can be concluded that the steaming process does not influence changes in the mechanical characteristics of the finger joints. Heat treatment of beech and the type of adhesive used significantly influence the tested mechanical characteristics of the finger joints and beech wood. Heat-treated beech had lower values of modulus of rupture (70 MPa) and density (690 kg/m³) and higher values of compression strength (59 MPa) in relation to un-modified (780 kg/m³) and steamed-treated (800 kg/m³) beech wood. Full article

Tomato brown rugose fruit virus (ToBRFV) has been causing severe agricultural damage worldwide since its recent discovery. While related to tobacco mosaic virus, its properties and infection mechanisms are poorly understood. To uncover their structure and nanomechanics, we carried out atomic force microscopy (AFM) measurements on individual ToBRFV particles. The virions are rod-shaped with a height and width of 9 and 30 nm, respectively. Length is widely distributed (5–1000 nm), with a mode at 30 nm. ToBRFV rods displayed a 22.4 nm axial periodicity related to structural units. Force spectroscopy revealed a Young’s modulus of 8.7 MPa, a spring constant of 0.25 N/m, and a rupture force of 1.7 nN. In the force curves a step was seen at a height of 3.3 nm, which is related to virion wall thickness. Wall thickness was also estimated by predicting coat protein structure with AlphaFold, yielding a protein with a length of 7.3 nm. Accordingly, the structural element of ToBRFv is a right circular cylinder with an equal height and diameter of ~22 nm and a wall thickness between 3.3 and 7.3 nm. Thus, at least four to nine serially linked units are required to encapsidate a single, helically organized RNA genome. Fragmentation of ToBRFV into these cylindrical structural units may result in a facilitated release of the genome and thus efficient infection. Full article

Three-dimensional concrete printing (3DCP) is an emerging technology that improves design flexibility and material efficiency in construction. However, widespread adoption of 3DCP requires overcoming key material challenges. These include controlling rheology for pumpability and buildability and achieving sufficient mechanical strength. This paper provides a comprehensive review of the application of nanoclays (NCs) as a key admixture to address these challenges. The effects of three primary NCs (attapulgite (ATT), bentonite (BEN), and sepiolite (SEP)) on the fresh- and hardened-state properties of printable mortars are systematically analyzed. This review summarize findings on how NCs enhanced thixotropy, yield stress, and cohesion, which are critical for shape retention and the successful printing of multilayered structures. Quantitative analysis reveals that optimized dosages of NCs can increase compressive strength by up to 34% and flexural strength by up to 20%. For enhancing rheology and printability, a dosage of approximately 0.5% by binder weight is often suggested for ATT and SEP. In contrast, BEN can be used at higher replacement levels (up to 20%) to also function as a supplementary cementitious material (SCM), though this significantly impacts workability. This review consolidates the current knowledge to provide a clear framework for selecting appropriate NCs and dosages to develop high-performance, reliable, and sustainable materials for 3DCP applications. Full article

The destabilizing damage of rock structures in coal beds engineering is greatly influenced by the bearing rupture features and energy evolution laws of rock–coal assemblages with varying height ratios. In this study, we used PFC3D to create rock–coal assemblages with rock–coal height ratios of 2:8, 4:6, 6:4, and 8:2. Uniaxial compression simulation was then performed, revealing the expansion properties and damage crack dispersion pattern at various bearing phases. The dispersion and migration law of cemented strain energy zoning; the size and location of the destructive energy level and its spatiotemporal evolution characteristics; and the impact of height ratio on the load-bearing characteristics, crack extension, and evolution of multiple energies (strain, destructive, and kinetic energies) were all clarified with the aid of a self-developed destructive energy and strain energy capture and tracking Fish program. The findings indicate that the assemblage’s elasticity modulus and compressive strength slightly increase as the height ratio increases, that the assemblage’s cracks begin in the coal body, and that the number of crack bands inside the coal body increases as the height ratio increases. Also, the phenomenon of crack bands penetrating the rock through the interface between the coal and rock becomes increasingly apparent. The total number of cracks, including both tensile and shear cracks, decreases as the height ratio increases. Among these, tensile cracks are consistently more abundant than shear cracks, and the proportion between the two types remains relatively stable regardless of changes in the height ratio. The acoustic emission ringing counts of the assemblage were not synchronized with the development of bearing stress, and the ringing counts started to increase from the yield stage and reached a peak at the damage stage (0.8${\sigma }_{\mathrm{c}}$) after the peak of bearing stress. The larger the rock–coal height ratio, the smaller the peak and the earlier the timing of its appearance. The main body of strain energy accumulation was transferred from the coal body to the rock body when the height ratio exceeded 1.5. The peak values of the assemblage’s strain energy, destructive energy, and kinetic energy curves decreased as the height ratio increased, particularly the energy amplitude of the largest destructive energy event. In order to prevent and mitigate engineering disasters during deep mining of coal resources, the research findings could serve as a helpful reference for the destabilizing properties of rock–coal assemblages. Full article

This study investigated the potential of hazelnut wood (Corylus avellana L.) as an alternative raw material in the production of single-layer structural particleboards. Boards with a target density of 700 kg m⁻³ and thickness of 13 mm were manufactured using varying substitution levels (5%, 10%, 25%, 50% and 100%) of hazel wood particles relative to industrial pine (Pinus sylvestris L.) particles. Phenol-formaldehyde (PF) resin was used as the adhesive at a 15% resination rate. Mechanical and physical properties, including modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), screw withdrawal resistance (SWR), water absorption (WA), and thickness swelling (TS), were evaluated according to relevant European standards. Density profiles (DP) were also assessed. The results showed that while higher hazel content reduced bending strength (from 23.3 N mm⁻² for reference to 18.7 N mm⁻² for 100% hazel wood board) and stiffness (from 3515 N mm⁻² for reference to 2520 N mm⁻² for 100% hazel wood board), most boards met standard mechanical requirements of EN 312 for P3 and P5 boards. Notably, IB strength improved significantly at higher hazel content, with the 100% variant (2.07 N mm⁻²) exceeding the reference board (1.57 N mm⁻²). Screw withdrawal resistance also increased with hazel wood addition (from 235 N mm⁻¹ for reference to 262 N mm⁻¹ for 100% hazel wood board), linked to its higher density. However, water resistance and dimensional stability worsened with increasing hazel content, particularly in bark-containing particles, leading to excessive thickness swelling after prolonged water exposure. Thickness swelling after 24 h of soaking rose from 16.36% for the reference board to 20.13% for the 100% hazel wood board. Density profiles revealed a more uniform internal structure in boards with higher hazel content. Overall, hazelnut wood shows promise as a partial substitute for pine in particleboard production, especially at moderate substitution levels, though limitations in moisture resistance must be addressed for broader industrial application. Full article

Aramid fibre has become a critical material for individual soft body armour due to its lightweight nature and exceptional impact resistance. To investigate its energy absorption mechanism, quasi-static and dynamic tensile experiments were conducted on Kevlar^® 29 plain-woven fabric using a universal material testing machine and a Split Hopkinson Tensile Bar (SHTB) apparatus. Tensile mechanical responses were obtained under various strain rates. Fracture morphology was characterised using scanning electron microscopy (SEM) and ultra-depth three-dimensional microscopy, followed by an analysis of microstructural damage patterns. Considering the strain rate effect, a viscoelastic constitutive model was developed. The results indicate that the tensile mechanical properties of Kevlar^® 29 plain-woven fabric are strain-rate dependent. Tensile strength, elastic modulus, and toughness increase with strain rate, whereas fracture strain decreases. Under quasi-static loading, the fracture surface exhibits plastic flow, with slight axial splitting and tapered fibre ends, indicating ductile failure. In contrast, dynamic loading leads to pronounced axial splitting with reduced split depth, simultaneous rupture of fibre skin and core layers, and fibrillation phenomena, suggesting brittle fracture characteristics. The modified three-element viscoelastic constitutive model effectively captures the strain-rate effect and accurately describes the tensile behaviour of the plain-woven fabric across different strain rates. These findings provide valuable data support for research on ballistic mechanisms and the performance optimisation of protective materials. Full article

A major breakthrough in environmentally friendly building materials is the development of sustainable unfired clay bricks including alumina waste produced during liquid nitrogen generation. Though used extensively, conventional fired clay bricks require energy-intensive manufacturing techniques that produce significant amounts of CO₂ and aggravate environmental damage. By removing the need for high-temperature firing and allowing for the valorization of industrial byproducts including alumina waste and lateritic soil, unfired clay bricks offer a reasonable low-carbon alternative. High silica and alumina contents define the alumina waste, which shows pozzolanic reactivity, thus improving the physicomechanical performance of the bricks. With alumina waste substituting 0–8.57% of the cement content, seven different formulations showed improvements in compressive strength, reduced water absorption, and optimal thermal conductivity. Especially, the mechanical performance was much enhanced with alumina waste inclusion up to 30%, without sacrificing thermal insulation capacity or moisture resistance. Further supporting the environmental and financial sustainability of the suggested brick compositions is the economic viability of using industrial waste and regionally derived soils. A comparative analysis of the conventional fired bricks shows that the unfired substitutes have a much lower environmental impact and show better mechanical properties, including greater compressive strength and modulus of rupture. These results support the more general goals of circular economy systems and low-carbon urban development by highlighting the feasibility of including alumina waste and lateritic soil into sustainable building materials. Using such waste-derived inputs in building fits world initiatives to lower resource consumption, lower greenhouse gas emissions, and build strong infrastructure systems. Full article

Although linear overproduction and overconsumption have benefited businesses, they have created an unsustainable society. Converting wood waste into construction material can support the transition to a circular economy. The mechanical properties of beams constructed from wood waste were measured. Squares with 50, 60, and 70 mm side lengths were glued to create beams, to which the three-point test method was applied parallel to the fibres. The stiffness and moduli of elasticity and rupture were analysed with standard industrial statistical techniques. Specifically, a two-stage analysis was performed using the normal distribution and Shewhart control charts. Changes of 100 mm in width and height and 200 mm in length caused a change of 200–400 N/mm² in elasticity and 500–1300 MNmm² in stiffness. Modulus of rupture values were relatively comparable, as they were determined by the properties of oak wood, from which the beams were made. The observed differences in the tested mechanical parameters will be useful in the optimisation of furniture construction, with our research suggesting that it is possible to predict mechanical properties from the dimensions of the waste-wood pieces. Ultimately, this should help to design sustainable furniture that is aesthetic, functional, and safe. Full article

Cardanol is a derivative of cashew nut shell liquid (CNSL) and has the potential to be used when developing adhesives for wood boards. Adding nanostructures to adhesive can increase its bonding and reduce formaldehyde emission. Therefore, this study aimed to evaluate the different concentrations of nanolignin (1, 2, and 3%) added to the cardanol-formaldehyde adhesive for gluing plywood, in comparison to the cardanol-formaldehyde adhesive without nanolignin (0%). The plywood’s physical, mechanical, and formaldehyde emission properties were assessed. Plywoods with nanolignin showed shear strength increases of around 160% in the wet condition. With the addition of nanolignin, the modulus of rupture and of elasticity increased by approximately 150% and up to 400% in the parallel direction, respectively. The resistance to combustion also significantly improved. Physical properties did not show statistically significant differences with the percentages of nanolignin. Despite the increase in formaldehyde emission with nanolignin, all treatments met the marketing requirements (≤80 mg of formaldehyde/kg), demonstrating the adhesive potential for indoor use in plywood industries. Natural adhesives using cardanol and nanolignin are an innovative and ecological alternative, combining sustainability and high potential to reduce environmental impacts, which is aligned with at least four sustainable development goals (SDGs). Full article

In this work, we present the fabrication of low-cost, stable nanocellulose colloidal suspensions with an average particle size of approximately 160 nm, produced via a straightforward, solvent-free ultrasonication process that eliminates the need for corrosive chemicals or energy-intensive mechanical treatments. The resulting nanocellulose suspensions were utilized as reinforcing additives in urea-formaldehyde (UF) resins, which were subsequently applied in the production of particle boards. This approach addresses the increasing EU regulatory constraints regarding low formaldehyde-to-urea (F/U) molar ratios and the broader need for biobased, eco-friendly alternatives in the wood adhesive industry. Mechanical testing of the nanocellulose reinforced boards revealed notable improvements in the internal bond strength and modulus of rupture, along with a significant decrease in formaldehyde release compared to boards produced with conventional UF resins. These findings highlight the potential of ultrasonication-derived nanocellulose as an environmentally friendly, cost-effective additive to enhance the mechanical performance and reduce the environmental impact of UF-based wood composites. Full article

Wellbore strengthening is a widely applied technique to mitigate wellbore leakage during drilling operations in complex formations characterized by narrow mud weight windows. This method enhances the wellbore’s pressure-bearing capacity by using lost circulation materials (LCMs) to bridge natural or induced fractures. In recent years, advanced sealing technologies such as wellbore reinforcement have gradually been applied and developed, but their related influencing factors and mechanisms have not been deeply revealed. This article uses the Cohesive module of ABAQUS to establish a wellbore fracture sealing model. By establishing a porous elastic finite element model, the elastic mechanics theory of porous media is combined with finite element theory. Under the influence of factors such as anisotropy of geostress, reservoir elastic modulus, Poisson’s ratio, and fracturing fluid viscosity, the circumferential stress distribution of the wellbore after fracture sealing is simulated. The simulation results show that stress anisotropy has a significant impact on Mises stress. The greater the stress anisotropy, the more likely the wellbore sealing is to cause wellbore rupture or instability. Therefore, it is necessary to choose a suitable wellbore direction to avoid high stress concentration areas. The elastic modulus of the reservoir is an important parameter that affects wellbore stability and fracturing response, especially in high modulus reservoirs where the effect is more pronounced. Poisson’s ratio has a relatively minor impact. In fracturing and plugging design, the viscosity of fracturing fluid should be reasonably selected to balance the relationship between plugging efficiency and wellbore mechanical stability. In the actual drilling process, priority should be given to choosing the wellbore direction that avoids high stress concentration areas to reduce the risk of wellbore rupture or instability induced by plugging, specify targeted wellbore reinforcement strategies for high elastic modulus reservoirs; using models to predict fracture response characteristics can guide the use of sealing materials, achieve efficient bridging and stable sealing, and enhance the maximum pressure bearing capacity of the wellbore. By simulating the changes in circumferential stress distribution of the wellbore after fracture sealing, the mechanism of wellbore reinforcement was explored to provide guidance for mechanism analysis and on-site application. Full article