Search Results (139)

The wood-based grid sandwich structure with a high load-to-mass ratio and specific strength was prepared with the core of KH-560-modified jute (Corchoruscapsularis) fabric-reinforced epoxy laminated composite (JFRELC). The compressing behavior and energy absorption characteristics of pure grid cores (GC50#, GC80#) and grid sandwich structures (GS50#, GS80#) were analyzed and compared. The failure mechanism of the fracture surfaces of jute fabrics of grid sandwich cores was clarified by SEM. The results showed that the core made of JFRELC-80# had a good performance for the grid sandwich structure by tenon-and-mortise linking. The load-bearing capacity and energy absorption performance of this wood-based grid sandwich structure can be comparable to that of some glass and carbon fiber reinforced composite sandwich structures, and even show certain advantages. The failure modes of the grid sandwich structure were panel cracking, core buckling and core collapse. The failure mechanisms of jute fabrics in epoxy resin were fiber pull-out and fiber splitting. Full article

Bio-based packaging is receiving increasing attention due to the environmental impact of fossil-based plastics. However, its practical implementation requires further evidence on material processing and functional performance. This study evaluated the thermal properties of expanded polylactic acid (E-PLA) prototypes blended with raw, minimally processed agroforestry residues. Specifically, spruce bark and grape stalks were used as waste wood fibers. This study focused primarily on the thermal characterization of the materials by measuring thermal conductivity and resistance. To evaluate the distribution of the two fractions (polymer and fibrous), samples were created with various volumetric ratios between the parts. Simultaneous pressure and microwave heating of the sample were used to stabilize the material. To characterize the raw materials used in this study, bulk density and moisture content were measured. To characterize the mixed materials samples, thermal conductivity and resistance, bulk density, and pressure were measured. To investigate the variables that influence thermal characteristics, statistical analyses such as regression models, ANCOVA, and Spearman correlation were applied. These analyses showed that increasing the biofiber content significantly reduced thermal resistance and increased thermal conductivity. However, negligible effects were observed for the type of fiber used and the duration of the heat treatment. These results describe the thermal properties of blends containing E-PLA and agroforestry residues. The results also show a marked effect of the biofiber content on thermal performance. This study does not provide a comprehensive characterization of the new materials, as it focuses on the prototyping methodology and the laboratory-scale production feasibility of E-PLA/agroforestry-residue prototypes. Full article

This paper examines certain strength characteristics of wood–concrete composites in comparison with other lightweight concretes. To address these issues, we conducted a series of experiments to study the relationship between the prismatic strength-to-cubic strength ratio, the development of strength, and the sequence of failure stages in arbolite–concrete composites with various structural characteristics under a destructive load. Our experiments confirmed that the ratio of cubic to prismatic strength in wood–concrete specimens ranges from 0.894 to 0.965 and, in some cases, approaches unity depending on the size, fibers, and microstructure of the organic aggregate. We have also established that the failure of fibrous-structured arbolite concrete specimens occurs sequentially: first, the mortar component fails, and then the organic aggregate fibers fail. In arbolite concrete specimens with a porous and coarse-pored structure, failure occurs simultaneously, as in other types of concrete. Based on the characteristics of the hardening and failure stages of arbolite–concrete composites, they can be used as wall material for building construction in regions with high seismic activity. Full article

Dendrochronological research has focused on species from temperate environments due to their high dendrochronological potential. However, in recent decades, advances in dendrochronology have been reported for species from tropical environments, which may be useful for analyzing the effects of climate variability. The objective of this study was to analyze the wood anatomy of Bursera simaruba, Sideroxylon foetidissimum, Gliricidia sepium, Vitex gaumeri, and Lysiloma latisiliquum from the island of Cozumel to identify their dendrochronological potential. The qualitative and quantitative anatomical characteristics were evaluated in accordance with the International Association of Wood Anatomists (IAWA) List of Microscopic Features for Hardwood Identification. B. simaruba, L. latisiliquum, and V. gaumeri exhibit dendrochronological potential (i.e., the development of distinct growth rings), unlike the S. foetidissimum, G. sepium. Differences in vessel diameter, vessel wall thickness, vessel density (number of vessels per mm²), fiber diameter, fiber lumen diameter, and fiber wall thickness between earlywood and latewood within the growth rings of these three species with dendrochronological potential indicate the formation of distinct growth rings. These findings contribute to the anatomical characterization and validation of growth-ring identification in tropical tree species for which anatomical and dendrochronological information remains scarce, thereby reinforcing the scientific foundation of tropical dendrochronology. Furthermore, they improve our understanding of the influence of climatic variables on tree growth and provide a valuable foundation for climate reconstructions at sites with limited or incomplete instrumental records, such as the Mexican Caribbean. Full article

The reprocessing of wood–plastic composites (WPCs) significantly affects their structural integrity and thermal behavior. Despite this, the effect of reprocessing on PVC-based WPCs has not been extensively investigated, and the mechanism is not well understood. This study evaluated the effect of reprocessing on the properties of a PVC-based WPC. Small pieces of extruded WPC boards (2–4 mesh) were first milled to a granulation of 50 mesh, and then the material was reprocessed by compression molding, with part of the samples reinforced with glass- and carbon-fiber fabric. The physical and mechanical properties of the reprocessed material were analyzed, and the chemical and thermal characteristics of the reprocessed WPC were compared with the virgin WPC. The results of the mechanical and physical property tests showed that the reprocessed WPC had satisfactory properties compared with the virgin WPC. Samples reinforced with carbon-fiber fabric showed a statistically significant increase in tensile and flexural strength in comparison with unreinforced reprocessed WPC samples. Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) showed that partial dehydrochlorination, thermal degradation and a decrease in thermal stability occurred. Overall, the results of this study show that although chemical degradation and a decrease in thermal stability were present in the reprocessed WPC, it retained satisfactory mechanical and physical properties that could be improved by reinforcing it with carbon-fiber fabric. Full article

The efficient utilization of hardwood lignocellulosic biomass has attracted increasing attention as a sustainable strategy for the high-value conversion of renewable resources. Chemical-mechanical pulping (CMP) is a promising route for hardwood utilization; however, its performance is strongly influenced by species-dependent differences in chemical composition, macromolecular structure, and physical accessibility. In this study, four representative hardwood species (poplar, sycamore, eucalyptus, and acacia) were selected as model feedstocks to investigate the relationships between structural characteristics and CMP performance in alkali-assisted systems. The chemical composition and structural features of cellulose, hemicellulose, lignin, and lignin-carbohydrate complexes were characterized, together with key physical parameters including density, porosity, and fiber morphology. The effects of alkali charge on fiber softening, fibrillation development, and paper properties were then evaluated. The results revealed pronounced species-dependent differences in alkali response, which were closely correlated with variations in cellulose supramolecular organization, hemicellulose substitution characteristics, lignin structural features, lignin-carbohydrate associations, and wood microstructure. This study provides a comprehensive qualitative comparative analysis of the relationships between wood structural features and CMP performance. Hardwoods with lower density and higher porosity exhibited more efficient alkali penetration and superior performance under mild conditions, whereas denser species such as sycamore and eucalyptus required higher alkali charge. This work provides important insights into the structure-performance relationships governing alkali-assisted CMP behavior, and offers useful guidance for the efficient utilization of lignocellulosic biomass in pulp and paper applications. Full article

This study developed poly(lactic acid) (PLA) biocomposites reinforced with pine wood flour (10, 20, and 30 wt%) to achieve the interphase through chemical modification. Specifically, the wood flour was treated with poly(propylene glycol) toluene 2,4-diisocyanate terminated (PEGTDI), while 1 wt% poly(lactic acid)-g-maleic anhydride (PLA-g-MA) was integrated as a reactive compatibilizer during extrusion and thermocompression. Fourier-transform infrared spectroscopy (FTIR) analysis corroborated the occurrence of urethane formation and ester/anhydride linkages, as substantiated by the presence of characteristic bands indicative of surface carbamation at 1645 and 1726 cm⁻¹. Thermal analysis revealed that both the pine wood flour and coupling agents promoted PLA crystallization; however, thermogravimetric analysis (TGA) indicated a decrease in thermal stability for functionalized composites, suggesting a trade-off between enhanced interfacial interaction and heat resistance. Mechanical testing demonstrated a significant reinforcement effect, with the Young’s modulus increasing by up to 22% in untreated composites. The coupling agents effectively optimized stress transfer at low fiber loadings (10 wt%), while flexural modulus improvements were predominant at higher loadings (20–30 wt%) regardless of treatment. These findings underscore the criticality of surface modification and compatibilizer selection for tailoring the structural and thermo-mechanical properties of PLA-based biocomposites, thereby providing a pathway for optimized performance in structural applications. Full article

Functional traits help to understand plant ecological strategies and play a determinant role in restoration. This study evaluated interspecific variability among 38 timber species of bioeconomic importance associated with natural forests and forest trials in the northern Colombian Amazon, identifying Plant Functional Types (PFTs) and their implications for productive restoration. Soft and hard traits were integrated, including tree morphological characteristics (diameter at breast height, total height, and crown cover) and wood functional traits (wood basic specific gravity, SG; maximum moisture content; fiber diameter and wall thickness; and vessel diameter and density). Correlations among these traits were also assessed. Five PFTs were identified. PFTs 1 and 2 grouped species with acquisitive strategies and high hydraulic efficiency, making them suitable for rapid vegetation cover recovery. In contrast, PFT 5 included conservative and hydraulically safe species, appropriate for enrichment processes once vegetation cover has been established. PFTs 3 and 4 represented intermediate strategies. Additionally, tree size was found to directly influence stem hydraulic architecture, and distinct anatomical configurations may occur within similar SG ranges, highlighting the need to integrate multi-trait approaches, as this trait alone does not fully capture the hydraulic and mechanical strategies of species. Full article

The development of lightweight, high-strength structural systems is a persistent pursuit in modern civil engineering. This paper presents an experimental study on a novel hybrid beam concept in which a sawn timber core is fully bonded with an externally applied Carbon Fiber-Reinforced Polymer (CFRP) laminate, fabricated through a controlled hand lay-up process. The design seeks to exploit the complementary characteristics of the two materials: timber provides compressive resistance and serves as a permanent formwork, while the CFRP carries tensile stresses with high efficiency. Fourteen hybrid beams, with variations in the number of longitudinal CFRP layers (one, two or, three), the presence or absence of longitudinal CFRP layers bonded along the top and bottom surfaces, and the presence or absence of circumferential wrapping in the pure bending region, were tested under four-point bending alongside two solid timber control beams. The results demonstrate that circumferential wrapping is a critical design detail. Wrapped beams consistently failed by tensile rupture of the CFRP—the intended failure mode—and exhibited ultimate moments 15–20% higher than their unwrapped counterparts. Beams with two longitudinal CFRP layers offered the most favorable balance between strength enhancement and material efficiency; adding a third layer shifted the failure mode to crushing of the timber core, indicating a core-limited condition. All hybrid beams showed pronounced linear-elastic behavior up to sudden brittle failure, with performance variability attributable to the inherent inhomogeneity of wood and the sensitivity of the hand lay-up process. The study provides quantitative data and mechanistic insights that support the design and application of bonded CFRP–timber hybrid beams as efficient structural members. Full article

The article presents the results of a study of constructed composites based on degradable poly(3-hydroxybutyrate) (P(3HB)) filled with plant materials of 30, 50, and 70% of different origin—wood flour (WF) from birch (Betula pendula), hemp hurds (HH) or hemp fiber (HF) (Cannabis sativa). Composite bar samples were obtained by hot pressing homogeneous mixtures of polymer and fillers at 170 °C and a specific pressure of 6.13 MPa. The influence of the filler type and the polymer/filler ratio on the temperature characteristics of the samples, density, microstructure, surface properties, water absorption, physical and mechanical properties, and degradability in soil was determined. The Young’s modulus of the samples ranged from 2640 to 3715 MPa, depending on the composition. The maximum degradation of the composites after 120 days of exposure to soil was recorded at 70% WF, HH, or HF filling, amounting to 77.4, 63.5, and 38.6%, respectively. Perspective biodegradable composites based on P(3HB) filled with various plant-based fillers were obtained and characterized, along with new knowledge about their properties, the lack of which currently hinders the active development and commercialization of such in-demand materials. Full article

Plastic waste poses a growing environmental challenge due to the extensive use of plastics in packaging applications. Recycling plastics offers environmental and economic advantages. Wood flour-derived from cypress wood, often generated as a by-product and discarded in landfills, contributes to environmental In this study, wood–plastic composites were fabricated from recycled high-density polyethylene, wood flour, and high-density polyethylene with maleic anhydride-grafted polyethylene as a coupling agent. Five composite formulations were produced by varying the recycled high-density polyethylene and wood flour volume ratios and processed through injection molding. The mechanical properties, including flexural, tensile, and impact strengths, along with water absorption behavior and microstructural characteristics, were evaluated in accordance with relevant standards using a universal testing machine, Charpy impact test, and scanning electron microscopy. The results revealed that increasing the recycled high-density polyethylene content from 20% to 35% significantly improved the composite performance, reducing water absorption by 9.86% and enhancing flexural, tensile, and impact strengths by 43.33%, 36%, and 35.03%, respectively. Morphological analysis confirmed improved fiber–matrix interfacial adhesion with higher recycled plastic content. These findings demonstrate the potential of recycled high-density polyethylene wood composites as sustainable materials for structural applications, combining environmental benefits with enhanced mechanical performance. Full article

Wood polymer composite (WPC), composed of polymer matrices reinforced with natural fibers, is increasingly used in structural and non-structural applications due to its sustainability and performance. Although teak and rice husk are common natural reinforcements, the use of oil palm empty fruit bunches (OPEFB) remains underexplored despite their abundance as agricultural waste. This study investigates the potential of OPEFB as an alternative reinforcement for recycled polyethylene-based WPC containing 20 wt% fiber and compares its morphology and performance with teak and rice husk. Compositional analysis shows that OPEFB exhibits lignin and cellulose contents as well as crystallinity comparable to teak, while exceeding rice husk in several structural parameters. These characteristics contribute to the highest tensile strength observed among the composites (37.45 MPa). Although its Shore D hardness is the lowest (58.8), the value remains within the acceptable range for construction applications. Combined with its favorable production costs, OPEFB emerges as a viable, resource-efficient alternative to conventional natural fibers, expanding the options for sustainable WPC development. Full article

Lignin obtained in acidic conditions is a waste product in various technological processes like sulfite pulping, organosolv pulping, or bioethanol production. Knowing the structure of the lignin enables its use in high-value-added applications. In this paper, the lignin structure isolated from Pinus sylvestris L. and Populus deltoides × maximowiczii wood in acidic conditions was investigated. Two methods of lignin isolation (Klason method and a method using a sulfuric and phosphoric acid mixture) were compared. Additionally, lignin acetylation was performed. The lignin samples were analyzed using different instrumental techniques, such as size exclusion chromatography (SEC), attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM). Based on the studies carried out, it was found out that the lignin isolated from pine and poplar wood in acidic conditions had a highly condensed structure. This was evidenced by the high-weight average molar mass of lignin (up to 118,700 g/mol) and the precipitates, aggregates, and agglomerates on its surface. Moreover, the characteristic signals of condensed lignin in ATR-FTIR analysis (band with wavenumber of 767 cm⁻¹) and their decrease/disappearance (band that usually occurs with a wavenumber of about 814 cm⁻¹) were observed. Lignin acetylation and analysis in the 0.5% LiCl/DMAc system have proven particularly effective in the case of the condensed poplar lignin. The beneficial effect of lignin acetylation was confirmed by SEM analysis. The high-molecular-weight condensed lignin, despite some of its problematic properties connected mainly with solubility, is a valuable substance that can be used for different applications (carbon fibers or as an additive for thermoplastic blends), which was confirmed by the studies in this paper and the findings of other scientists. Full article

Softwood-based composites are increasingly used in structural and nonstructural applications owing to their renewability, cost-effectiveness, and favorable strength-to-weight performance. This study applies a systematic literature review and comparative analysis, drawing on approximately 140 sources, to synthesize current knowledge on the physicochemical, mechanical, thermal, and environmental characteristics of engineered wood products derived from softwood species. The intrinsic lignocellulosic composition of softwood, comprising roughly 40%–45% cellulose, 25%–30% hemicelluloses (with mannose as the predominant sugar), and 27%–30% lignin, strongly influences hydrophilicity, stiffness, and thermal behavior. Mechanical properties vary across engineered wood product classes; for example, plywood exhibits a modulus of rupture of 33.72–42.61 MPa and a modulus of elasticity of 6.96–8.55 GPa. Microstructural and spectroscopic analyses highlight the importance of fiber–matrix interactions, chemical bonding, and surface modifications in determining composite performance. Emerging advanced materials, such as scrimber, with densities of 800–1390 kg/m³, and fluorescent transparent wood, achieving optical transmittance above 70%–85%, demonstrate the expanding functional potential of softwood-based composites. Sustainability assessments indicate that coatings, flame-retardants, and adhesives may contribute to volatile organic compound emissions, emphasizing the need for lower-emission, bio-based alternatives. Overall, the findings of this systematic review show that softwood-based composites deliver robust, quantifiable performance advantages and hold strong potential to meet the rising demand for sustainable, low-carbon engineered materials. Full article

After a series of successful reintroductions, the Eurasian beaver (Castor fiber) is expanding its range throughout Europe. Timely monitoring of beaver activity contributes to early detection of environmental impacts and aids in mitigating human–wildlife conflicts and other threats. However, the signs of beaver presence are difficult to detect in some environments, e.g., densely vegetated river banks or in areas with considerable water level variability. In these cases, new technologies can offer opportunities for easier and faster monitoring. In the current study, we provide a characterisation of the wood-gnawing activity of a newly established beaver population in Northern Bulgaria, using a traditional transect method. In addition, we test the application of unmanned aerial vehicles (UAVs) to detect and map the signs of beaver activity. The overall gnawing-activity characteristics of newly established Castor fiber populations in Bulgaria follow the pattern documented in earlier studies: the affected trees were mainly willow and poplar, located at less than 10 m from the riverbank, with a diameter mostly under 30 cm. However, there were considerable differences in the tree size and distance from the water between the two studied habitats—the Danube River and its tributaries. No dams were recorded, probably due to the rivers’ sizes. We found no significant difference in the detection rates of the UAV with and without canopy cover. Overall, the UAV-based transects were reliable for the detection of the species’ presence, but not for quantification of its activity patterns, due to the low detection rates, in comparison with ground-level transects. We believe that the method is promising because it is cost- and time-saving but could be improved using cameras with better resolution and by involving machine learning algorithms. The drone detection method could help identify the areas with the densest populations of the species, where Natura 2000 protected zones could then be established. Full article