Search Results (21)

The study presented in this paper investigates the influence of coating polymers on the acoustic properties of resonant spruce wood. It evaluates absorption, acoustic reflection, and resonance frequency spectrum characteristics in both unvarnished and varnished samples, with the interface between the coating polymer and the wood modifying the acoustic response. The novelty of the research consists in evaluating the acoustic and dynamic parameters of resonant spruce wood boards, varnished with varnishes with different chemical properties (oil-based varnish, spirit varnish, nitrocellulose varnish). The study focuses on the influence of the type of varnish and the thickness of the varnish film on the frequency spectrum, damping coefficient, quality factor, acoustic absorption coefficient, and sound reflection. The sound absorption coefficient increases with the number of varnish layers and is influenced by the sound’s frequency range, the type of varnish, and the quality of the wood—factors that collectively enhance acoustic performance. For instance, oil-based varnish applied in 5 or 10 layers contributes to a fuller sound at a frequency of 1.5 kHz. In contrast, spirit varnish, which has a lower acoustic absorption coefficient at this frequency, and a reduced damping coefficient, can lead to a nasal tone, although the frequency spectrum turns out to have the richest. Applying more than 10 layers of varnish softens the sound when using oil-based varnish but sharpens it with spirit varnish on resonant wood. Thus, the acoustic performance of a soundboard can be tailored by selecting the appropriate varnishing system and number of layers applied. However, a detailed analysis of the timbre of musical instruments finished with these varnishes is necessary to confirm their influence on the acoustic quality of the instruments. Full article

Wood–plastic composites (WPCs) are interesting materials as the biobased content is determined by the inclusion of wood particles regenerated from residual wood sources or biomass products. At present, the aim is to increase the wood content in WPCs above 60%, while it is currently limited to around 40%. The rationale behind this is based on the need for an increase in the performance of WPCs, the relatively cheap price of wood and the aim to augment the biobased content. Most studies are presently carried out with a maximum of 50% wood particles (preferably ranging from around 30 to 40%), while there are only very few sources where the wood concentration is increased to 70%. The formulations are not yet optimized and there are problems in interface compatibility, leading to weak mechanical properties. Problems in the augmentation of the wood content have to be further controlled, e.g., aggregation, dimensional stability and water absorption. Alternative approaches for the treatment of wood chips before (or during) compounding with the polymer matrix should therefore be developed. As the water resistance is mainly related to the control of the surface properties of the hydroscopic wood particles, possible solutions should consider the better protection of the individual wood particles’ surfaces against water ingress, the better development of the wood–polymer interface and the prevention of the formation of a continuous network with contacting wood particles. Therefore, this overview suggests various processing routes together with their industrial potential based on various sources from the literature, including the effects of compatibilizers and additives, the spray coating of wood particles, chemical pretreatment, physical modifications and the thermal treatment of wood fillers. Full article

A novel elastomer-modified multicomponent, multiphase waste-sourced biocomposites, was prepared for converting waste biomass and plastic into value-added products. The effects of blending elastomer–olefin block copolymer (OBC) and maleic anhydride (MAH), and divinylbenzene (DVB) co-grafting of recycled polypropylene (rPP) matrix on the adhesion interface, structure, and properties of high wood flour-filled (60 wt.%) composites were thoroughly investigated. The results indicated that DVB introduced branched structures into the polymer matrix molecular chain and increased the MAH grafting rate. Co-grafting rPP/OBC blends enhanced the interfacial adhesion among rPP, OBC, and wood flour. Additionally, MAH-grafted OBC was prone to encapsulating rigid wood flour, thereby forming an embedded structure. Notably, the tensile modulus and impact strength of the final three-component composites increased by 60% and 125%, respectively, compared with the unmodified composites. Additionally, dynamic mechanical analysis revealed that DVB-induced branching promoted the formation of microvoids in the OBC shell layer surrounding the wood, which in turn induced significant plastic deformation in the polymer matrix. This work offers a facile and efficient method for preparing high-toughness, high-stiffness, and low-cost waste PP-based composites for automotive interiors, and indoor and outdoor decoration. Full article

Wood–plastic composites (WPCs) utilize wood particles as the reinforcing phase. These particles are susceptible to thermal degradation, which can happen while processing the WPCs in usual thermoplastic processes. In this work, we investigated the influence of different processing parameters in injection molding and their influence on WPC properties. To achieve that, WPCs with wood contents ranging from 10 to 50 wt% were processed using different process settings, and then characterized using mechanical testing and appearance changes. We found that the melt temperature showed a major influence, due to degrading the interface between the wood and the polymer matrix, while other parameters, like mold temperature and dwell pressure, showed only minor influence. Overall, the WPCs exhibited good process stability and, with proper process settings, their performance can be improved. Full article

Microplastics, plastic particles smaller than 5 mm, pose a significant environmental threat due to their persistence and distribution in aquatic ecosystems. Research on the dynamics of microplastics within freshwater systems, particularly concerning their transport and deposition along river corridors, remains insufficient. This study investigated the occurrence and deposition of microplastics at the water–sediment interface of the White River near Muncie, Indiana. Sediment samples were collected from three sites: White River Woods (upstream), Westside Park (midstream), and Morrow’s Meadow (downstream). The microplastic concentrations varied significantly, with the highest concentration recorded upstream, indicating a strong influence from agricultural runoff. The types of microplastics identified were predominantly fragments (43.1%), fibers (29.6%), and films (27.3%), with fragments being consistently the most abundant at all sampling sites. A polymer analysis with selected particles using Fourier-transform infrared (FTIR) spectroscopy revealed that the most common polymers were polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET). The hydrodynamic conditions played a crucial role in the deposition and transport of microplastics. The statistical analysis demonstrated a strong positive correlation between the microplastic concentration and flow velocity at the downstream site, suggesting that lower flow velocities contribute to the accumulation of finer sediments and microplastics. Conversely, the upstream and midstream sites exhibited weaker correlations, indicating that other environmental and anthropogenic factors, such as land use and the sediment texture, may influence microplastic retention and transport. This study provides valuable insights into the complex interactions between river dynamics, sediment characteristics, and microplastic deposition in freshwater systems. These findings contribute to the growing body of knowledge on freshwater microplastic pollution and can help guide mitigation strategies aimed at reducing microplastic contamination in riverine ecosystems. Full article

This study investigated the effect of two critical variables for environmental process sustainability, i.e., extruder temperature and printing rate, on thermomechanical performance and accuracy in overall sample sizes, when printing bio-based materials. In this context, 3D specimens produced from basic polylactide (n-PLA) and wood-filled PLA polymer (f-PLA) were realized using extrusion-based additive manufacturing technology (MEX) by varying the nozzle temperatures (200 °C, 210 °C, and 220 °C) and speed (from 70 mm/s to 130 mm/s). Dynamic mechanical analysis (DMA) was carried out on the produced specimens, providing information on changes in storage modulus at testing temperature of 30 °C (E′₃₀) and glass transition temperature (Tg) for each printing condition. Measurements of sample sizes allowed for printing precision considerations as a function of processing temperature and speed. The results revealed similar trends in E′₃₀ changes in printed specimens at a fixed extruder temperature as a function of printing speed for n-PLA and f-PLA. Infrared spectroscopy was performed on printed samples and unextruded material to attest potential material degradation under various operating conditions. Finally, images of sample surface allowed to verify the homogeneity of the diameter of the extruded material and the layer–layer contact at the interface. Full article

Traditional wood–polymer composite (WPC) based on the in situ polymerization of ethylene unsaturated monomers in the cellular cavity of wood is significant for the high-value-added utilization of low-quality wood. However, this type of WPC has the problems of volatile monomers, low conversion rates, odor residue, and poor compatibility between the polymer and wood interface, which hinder its promotion and application. In this study, a two-step process of cell wall bulking in combination with cell lumen filling was prepared to modify wood using Maleic anhydride (MAN) as the bulking agent and GMA-EGDMA (molar ratio 2:1) as the active monomer system. The results indicate that the modulus of rupture (MOR) (125.19 ± 8.41 MPa), compressive strength (116.38 ± 7.69 MPa), impact toughness (55.4 ± 2.95 KJ m⁻²), and hardness (6187 ± 273 N) of the bulking–filling wood composite materials were improved by 54%, 56%, 36%, and 66%, respectively, compared with those of poplar wood. These properties were superior to those of the traditional styrene (PSt)-WPC and even exceeded the performance of Xylosma congesta (Lour.) Merr, a high-quality wood from northeast China. Meanwhile, the mass loss of wood composite materials with bulking–filling treatment was only 2.35 ± 0.05%, and the internal structure remained intact, presenting excellent decay resistance. Additionally, the treatment also significantly improved the thermal and dimensional stability of the wood composites. This study provides a theoretical basis and guidance for realizing the high-value-added application of low-quality wood and the preparation of highly durable wood-based composites. Full article

Biodegradable polymers have recently become attractive and have been increasingly used as matrix materials to replace fossil plastics due to concerns about the environmental issue. However, their application areas are limited due to their high costs and natural properties. In this study, we fabricated ecofriendly and economical polybutylene adipate terephthalate (PBAT) composites loaded with various concentrations of wood flour (WF) to investigate the effects on the PBAT and WF interfaces as well as the physical properties of the WF/PBAT biocomposites. Then, WF was acetylated with acetic anhydride, and the effect of WF acetylation on the mechanical and thermal properties of the biocomposites were investigated. The results showed that the tensile strength, tensile modulus, flexural strength and flexural modulus increased with WF loading in the composites, and acetylation could not only further increase these properties, but also increase the impact strength and elongation at break. The incorporation of WF would weaken the thermal stability of PBAT, but the thermal stability of the biocomposite could be improved after WF acetylation. The cold crystallization temperature and hydrophobicity of the WF/PBAT samples would be increased with the increasing load of the WF, while the melting enthalpy and the crystallinity of the samples reduced gradually. A morphological analysis of the modified composites revealed that the matrix exhibited greater interfacial interactions with the WF compared to the WF/PBAT. Considering the much lower cost of WF compared to PBAT, the improved properties of WF/PBAT biocomposites will make it economically competitive with other commercial polymers, and these biocomposites should have much wider application areas. Full article

Despite their popularity and multiplicity of applications, wood–polymer composites (WPCs) still have to overcome particular issues related to their processing and properties. The main aspect is the compatibility with plant-based materials which affects the overall performance of the material. It can be enhanced by strengthening the interfacial adhesion resulting from physical and/or chemical interactions between the matrix and filler, which requires introducing a compatibilizer or a proper modification of one or both phases. Herein, the impact of cellulose filler modifications with varying contents (1–10 wt%) of hexamethylene diisocyanate (HDI) on the compatibility of Mater-Bi/poly(ε-caprolactone) (PCL)-based biocomposites was evaluated. An analysis of surface wettability revealed that the filler modification reduced the hydrophilicity gap between phases, suggesting compatibility enhancement. It was later confirmed via microscopic observation (scanning electron microscopy (SEM) and atomic force microscopy (AFM)), which pointed to the finer dispersion of modified particles and enhanced quality of the interface. The rheological analysis confirmed increased system homogeneity by the reduction in complex viscosity. In contrast, thermogravimetric analysis (TGA) indicated the efficient modification of filler and the presence of the chemical interactions at the interface by the shift of thermal decomposition onset and the changes in the degradation course. Full article

The application of fibre-reinforced polymers (FRP) for strengthening timber structures has proven its efficiency in enhancing load-bearing capacity and, in some cases, the stiffness of structural elements, thus providing cost-effective and competitive alternatives both in new design and retrofitting existing historical buildings. Over the last few decades, several reinforcing materials and techniques evolved, and considerable progress was made in numerical modelling, especially using the finite element method. As this field of research has become extensive and diversified, as well as numerous contradicting results have emerged, a thorough review is necessary. This manuscript covers the topics of historical preliminaries, reinforcing with carbon and glass fibre composites, bond characteristics, main reinforcing techniques, modelling of knots, and the effects of the fibre waviness on the composite behaviour. A detailed overview is given on the experimental and numerical investigation of mechanics of strengthened beams. A one-of-a-kind table is presented that compares the stiffness improvement observed in several studies with analytical estimates. Attention is drawn to a number of challenges that have arisen, e.g., the moderate stiffness enhancement, composite-to-wood interface, modelling of knots, and strengthening of defected timber members. This paper can be used as a starting point for future research and engineering projects. Full article

The paper presents new value-added composite materials prepared by recycling tire rubber, polyethene terephthalate (PET), high-density polyethene (HDPE), wood sawdust, and fly ash. The composites were manufactured through the compression molding technique for three temperatures (150 °C, 160 °C, and 190 °C) previously optimized. The addition of fly ash as reinforcement in polymer blends is a viable route to improve the composite” properties. The paper aims to assess the effect of fly ash on the mechanical properties and water stability of the new all waste composites considering their applications as outdoor products. The static tensile (stress-strain behavior) and compression properties of the composites were tested. The fly ash composites were characterized in terms of wetting behavior and surface energies (contact angle measurements); chemical structure of the new interface developed between composite” components (FTIR analysis), crystalline structure (XRD analysis), surface morphology and topography (SEM, AFM). The addition of fly ash promoted the development of the hybrid interfaces in the new composites, as FTIR analysis has shown, which, in turn, greatly improved the mechanical and water resistance. The novel all waste composites exhibited lower surface energies, larger contact angles, and smoother morphologies when compared to those with no fly ash. Overall, the study results have revealed that fly ash has improved the mechanical strength and water stability of the composites through the formation of strong hybrid interfaces. The study results show optimal water stability and tensile strength for 0.5% fly ash composites cured at 190 °C and optimal compressive strength with good water stability for 1% fly ash composite cured at 150 °C. Full article

The increasing use and potential of polylactic acid (PLA) in wood-based composite materials due to its greater performance over common polyolefins provides the justification for a closer examination of the PLA−wood adhesion performance. In PLA-bonded laminates and composites, the optical differentiation between PLA polymer and wood is not possible and necessitates complex techniques such as fluorescence microscopy to characterize the PLA adhesion interface. In this study, spatial chemical imaging via FTIR analysis has been successfully applied to directly identify PLA bondlines within PLA-bonded veneer laminates and to determine the migration of semi-crystalline and amorphous PLAs from the bondline into the wood structure. This method uses involved point contouring line spectra over the bondline area to distinguish the PLA polymer from the wood. From this quantitative analysis, it is revealed that bondline thickness and PLA penetration values depend on pressing temperature, and this has implications for the reinforcement of the adhesion interface and the bondline performance. Furthermore, in developing a methodology for this assessment, this spatial chemical imaging approach can equally be applied to other polyester, amide, and urethane systems used to bond wood laminates. Full article

Birch (Betula pendula Roth.) and beech (Fagus sylvatica L.) solid wood and plywood were overmolded with polyamide 6 (PA 6) and polypropylene (PP) to investigate their mechanical properties and interfacial adhesion. In the case of PA 6, maximum tensile shear strengths values of more than 8 to 9 MPa were obtained for birch and beech, respectively. The values are comparable to bond strengths of commercial joints bonded with formaldehyde-containing amino-plastics. Perpendicular to the wood elements, bond strength values of 3 MPa was achieved for PA 6. The penetration of the polymers into the wood structure results in a non-densified interphase and subsequent plastic deformation of the wood structure beyond the interphase. These compressed areas influenced the interfacial adhesion and mechanical interlocking. SEM and XPS analysis revealed different interpenetration behavior of the polymers into the wood structure, with chemical interaction confirmed only for wood and PA 6 but not PP. Full article

Light wood roof-to-wall connections are vulnerable when subjected to high-speed winds. In lieu of traditional metal connections, the present finite element analysis (FEA) study focuses on the use of epoxy and easy-to-apply, noncorrosive FRP ties to connect the roof and the walls in wood frames. The FEA models of the wood roof-to-wall GFRP connection were validated with an experimental study in the literature. Subsequently parametric study was performed on the validated FEA models. Parameters considered were the addition of anchorages to secure the GFRP ties for FEA models of shear and uplift tests, and various FRP types. Wood roof-to-wall connection uplift model was subjected to monotonic cyclic loading to simulate the effect of wind load. In addition, carbon and basalt FRP ties were also examined under monotonic cyclic loading. To evaluate the efficiency of GFRP ties with and without anchorages, the shear and uplift design loads specified in ASCE 7-16 were calculated. Finally, a formula was proposed to approximate the shear strength of GFRP connection in comparison with double shear bolted metal plate connections. The FEA models and experimental results were in good agreement. The finite element results revealed that anchorage increased the uplift load capacity by 15% but the increase in shear capacity was insignificant. Comparing glass, carbon, and basalt FRP ties, BFRP was superior in deformation capacity and CFRP provided more stiffness on uplift test simulation. GFRP ties were found to be approximately nine times stronger in shear and two times stronger in uplift resistance than hurricane clips. Finally, the proposed formula could predict the shear strength of GFRP tie connection which in turns contributes to the design and future research. Full article

Composite materials are increasingly used to strengthen existing structures or new load-bearing elements, also made of timber. In this paper, the effect of the number of layers of Carbon Fiber Reinforced Polymer (CFRP) on the load-bearing capacity and stiffness of Glued Laminated Timber beams was determined. Experimental research was performed on 32 elements—a series of eight unreinforced beams, and three series of eight reinforced beams: with one, three and five layers of laminate each. The beams with a cross-section of 38 mm × 80 mm and a length of 750 mm were subjected to the four-point bending test according to standard procedure. For each series, destructive force, deflection, mode of failure, and equivalent stiffness were determined. In addition, for the selected samples, X-ray computed tomography was performed before and after their destruction to define the quality of the interface between wood and composite. The results of the conducted tests and analyses showed that there was no clear relationship between the number of reinforcement layers and the load-bearing capacity of the beams and their stiffness. Unreinforced beams failed due to tension, while reinforced CFRP beams failed due to shear. Despite this, a higher energy of failure of composite-reinforced elements was demonstrated in relation to the reference beams. Full article