Effect of natural and accelerated aging on the properties of wood-plastic composites

The correspondence of natural and laboratory-accelerated aging of WPC has long been a highly important problem discussed by many scholars. In this work, the changes in moisture content (MC), modulus of rupture (MOR), modulus of elasticity (MOE), screw holding force and creep recovery rates of two groups of wood-plastic composites (WPC) after natural and accelerated aging (high-low temperature cycles and freeze-thaw cycles) were studied to provide guidance for the use of WPC in outdoor applications. The results showed that, after the natural aging and freeze-thaw cycles treatments, MC increased significantly with both 167% of the untreated value of wood-HDPE composites with 30% wood fiber content and a thickness of 25 mm (W25), while 67% and 133% of the wood-HDPE composites with 30% wood fiber content and a thickness of 20 mm (W20), but is almost unchanged after the treatment with high-low temperature cycles. The mechanical strength, including MOR, MOE, screw holding force and creep recovery rate, decreased after natural and accelerated aging. The greatest decreases of MOR, MOE, screw holding force and creep recovery rate were 14%, 13%, 21%, and 7% for W25, while 5%, 8%, 8%, and 14% for W20 respectively. Environmental aging can reduce the strength of WPC, but the bending strength retention rate is more than 85%, showing that performance of WPC is relatively stable compared to wood materials, which is one of the reasons for the widely use of WPC in outdoor applications.

Ratio analysis between compression and shearing of 72 Brazilian wood species

The Brazilian standard ABNT NBR 7190 (1997) governs the premises for the wood structure sizing through a table and the simplified method. Thus, this research aims to analyze whether the simplified method shown in the standard matches the resistance values of 72 Brazilian species, separated from class C20 to C60. In the end, it was possible to conclude that the value displayed by the standard between the ratio of shear and compression in the direction parallel to the fibers is half of what actually happens in Brazilian species, showing an urgent review in the standard premises.

Study on permeability of Cunninghamia Lanceolata based on steam treatment and freeze treatment

In order to improve the permeability of Cunninghamia lanceolata, the weight gain rate of C. lanceolata was taken as index. The effect of time, temperature and water content on the weight gain rate of impregnated wood was analyzed by frozen and steaming treatment. By comparing the weight gain rate under different modification methods, the optimal modification process was determined. The results indicate that the optimum parameters of C. lanceolata were saturated water content (-25°C and 8 h) at this time, the three-day gain rate of silica sol impregnated at normal temperature and pressure was 15.058%. After C. lanceolata is pre-treated by superheated steam, the weight gain rate of C. lanceolata, which in oven-dried specimen (120°C and 3 h) contents was the highest, at this time, the three-day gain rate of silica sol impregnated at normal temperature and pressure was 15.291%. By comparing the results of pre-freezing with the results of superheated steam treatment of C. lanceolata, the latter will increase the permeability of C. lanceolata better. Therefore superheated steam treatment should be chosen as an effective method for the pretreatment.

Impact of the electric cables installation on the ignition parameters of the spruce wood surface

This study is aimed to investigate of an impact of electrical cables installed on Norway spruce (Picea abies (L.) Karst.) wood board surface on main ignition parameters (mainly critical heat flux, ignition temperature, thermal response parameter and thermal inertia). Ignition parameters have been determined by dependence of ignition times (raised to the power of -1, -1/2 and -0.547) on heat flux. Initiation times have been measured for three configurations of spruce wood boards with surface dimensions of 100 x 100 mm ± 1 mm (the first configuration: board without cables on surface, the second configuration: board with three electrical cables on surface – spacing between cables was equal to their diameter and the third configuration: board with five electrical cables – spacing between cables was equal to their diameter) at five heat fluxes (30, 35, 40, 45 and 50 kW·m-2). Obtained results proved that installation of the electrical cables on the spruce wood board surface has a significant impact on the ignition parameters. The critical heat flux (8.5 kW·m-2), apparent thermal inertia 0.20 ± 0.02 kJ2·m-4·K-2·s-1 and ignition temperature 324 ± 105°C of spruce wood board increased up to 18 ± 3 kW·m-2 (critical heat flux), 0.68 ± 0.03 kJ2·m-4·K-2·s-1 (apparent thermal inertia) and 475 ± 27°C (ignition temperature) by the installation of electrical cables on the surface of spruce wood board.

A comparison of metabolites in wood-forming tissues from eight commercial timber tree species of Heilongjiang province in China

Four coniferous and four deciduous commercial tree species from Northeastern of China were selected to investigate the differences of metabolites in wood-forming tissues by gas chromatography-mass spectrometry. The results showed that the identified metabolites mainly consisted of neutral sugars, lipids, and organic acids. The mean contents of both arabinofuranose and 1-cyclohexene-1-carboxylic acid were higher in coniferous trees than in deciduous ones. Similarly, the D-fructose and D-glucose content was significantly higher in coniferous trees than deciduous trees, but the total contents of these two sugars was roughly equal among most tree species. The mean content of lactic acid, glycerol and malic acid was lower in coniferous trees than deciduous trees. The malic acid content decreased in later-stages of wood formation than in early-stage for all tree species. The content of L-proline and myo-inositol was greater in later-stage of wood formation than early-stage. The content of octadecanoic acid, D-fructose and D-glucose decreased in later-stage of wood formation for most tree species. All of this suggested that the metabolites in wood-forming tissues showed the significance of species-specific and seasonal dynamic differences among the eight tree species.

Selected properties of compregnated wood using low molecular weight phenol formaldehyde and succinic anhydride

The aim of this study was to investigate the effect of impregnating materials (low molecular weight phenol formaldehyde or LmwPF and succinic anhydride or SA), their concentrations (5 and 10%), and compression ratios (20 and 40% from initial thickness) on improvement of specific gravity (SG) and dimensional stability on nyatoh, sepetir, and pisang putih wood; and then compared them to control and densified wood. The results showed that SG and dimensional stability of compregnated wood were affected by all parameters studied. Higher compression ratio and concentration will result in a greater improvement. In general, SG and dimensional stability of compregnated wood were better than the control. SG of LmwPF- and SA-compregnated wood increased by 10.69‒22.31% and 6.96‒23.09%, respectively. Utilization of LmwPF and SA has significantly reduced the spring-back, but the latter is better. The compression-set recovery after compregnation was 18.34‒33.99%, while after densification was 47.86‒71.49%.

Efficacy of linseed oil-treated wood to improve hydrophobicity, dimensional stability, and thermostability

In this work, linseed oil was impregnated into the wood at room temperature, under vacuum pressure. The properties of linseed oil-treated wood, including dimensional stability, wood moisture absorption, chemical structure, thermostability, and morphological characteristics, were evaluated. Linseed oil displayed good permeability in Ailanthus wood, with weight gains of 30.95% after impregnation. The swelling coefficients of treated wood in the tangential and radial directions decreased by 25.97 to 33.33%, indicating that impregnation improved the dimensional stability of wood. Moreover, linseed oil treatment significantly modified the wood structure, although the FTIR spectra generally remained unchanged. Observation by scanning electron microscopy showed, that linseed oil impregnated into the wood and occluded pits, thereby prevented moisture absorption. This technique can be used in a variety of wood products, such as buildings, furniture, and landscape architecture.

Determining the coefficient of friction of wood-based materals for furniture panels in the aspect of modelling their shredding process

In order to improve the power selection of the drive unit for the shredding machines, the authors determine the values of friction coefficients used in the cutting force models. These values consider the friction between steel and such wood-based materials as chipboard, MDF and OSB. The tests concern laminated and non-laminated external surfaces and surfaces subjected to cutting processes. The value of the coefficient of friction for the tested materials is in the range: for the static coefficient of friction 0.77-0.33, and for the kinetic coefficient of friction 0.68-0.25. The highest values of the static and kinematic coefficient of friction were recorded for MDF (non-laminated external surface) and they were equal respectively: 0.77 and 0.68. In turn, the smallest values of the discussed coefficients were recorded for chipboard (laminated external wood-base surface), which were at the level of 0.33 and 0.25, resp.

Modelling of steel-timber composite beams: Validation of finite element model and parametric study

In this paper, non-linear finite elements models (FEM) of steel-timber composite (STC) beams have been developed and analyzed using ABAQUS software. In the FEM, the loading conditions of STC beams were simulated, and the nonlinear behaviour of the contact interface between the steel and timber components were incorporated adequately into the FEM. For the yield load, the maximum error between the FE results and the experimental results is 14.85%. The maximum average error of the yield deflection is 12.94%. and of the ultimate load is 16.79%. However, the error of key points was less than 17% (within a reasonable range), which proves that the established finite element model, selected material parameters and contact element model can better simulate the bending performance of STC beams. Finally, a parametric study was carried out by using the verified FEM. It is shown that the FEM developed in this study can replicate adequately the load-deflection response, and the development of stress and plasticity of the bending experiment. Through the parameter study, it can be seen that the distribution density and mechanical properties of the connection between the glulam and H-section steel can affect the mechanical behavior of the whole STC beams.

Use of logging waste in technologies for deep chemical processing of wood

The study presents theoretical aspects and modern technologies for processing wood biomass, considers the possibility of obtaining wood chips from felling residues of cutting areas, in particular technological chips that meet the GOST 15815: 1983 “Technological chips. Specifications” standard for use as raw materials in the production of fiberboard. Wood fiber obtained from similar in size and quality indicators according to GOST 15815: 1983 technological chips, pre-treated in a defibrator, was subjected to a refining process at a low concentration, in particular using the developed design of the disks of the refiner of fibrillating action while regulating the main parameters of the process. The resulting wood-fiber mass was characterized by an improvement in the fractional composition of fibers, their size and quality indicators. As a result, improving the quality of the wood-fiber mass provides an increase in the physical and mechanical properties of wood-fiber boards under all other equal production conditions, which excludes the use of binding resins, and may indicate the possibilit of effective processing of logging waste.

Comparative proteomic analysis of the thick-walled ray Formation process of haloxylon ammodendron in the gurbantunggut desert, China

Thick-walled ray cells of Haloxylon ammodendron were first reported by Zhou and Gong in 2017, but their formation mechanism remains unknown. In this study, we performed a proteomic analysis of ray cell wall formation in the xylem. H. ammodendron in Shihezi exhibits a thicker ray cell wall than that in Jinghe. During the process of cell wall biosynthesis in the xylem of H. ammodendron, the nonspecific lipid-transfer protein and beta expansin EXPB2.1 (Mirabilis jalapa) first loosen the cell wall, and this step is followed by extension and expansion. Subsequently, xyloglucan endotransglycosylase/hydrolase 1 cleaves and links the xyloglucan chains. Photosystem I P700 apoprotein A1, reversibly glycosylated polypeptide 1 and GDP-mannose-3′,5′-epimerase are involved in the cellulose, hemicellulose and pectin biosynthesis processes in the cell wall by providing components or energy. Finally, the proteins involved in phenylpropanoid biosynthesis promote lignification of the ray cell wall and complete the biosynthetic process of the cell wall.

Experiments and reliability analysis on frame-to-sheathing joints in light wood framed shear walls

To exploit the spruce-pine-fir (SPF) panel and the parallel strand bamboo (PSB) panel used in light wood framed shear wall and investigate the lateral behaviors of frame-to-sheathing joints in light wood framed shear wall with different characteristics, the experimental investigation and reliability analysis were carried out under monotonic load. The test configurations included joints with perpendicular-to-framing-grain load or parallel-to-framing-grain load, with SPF sheathing panel or PSB sheathing panel and with nail or screw. The results suggested that nailed joints with PSB panel occurred ductile failure but other joints occurred brittle failure. Moreover, the ultimate bearing capacity and the elastic stiffness of the joints under perpendicular load were higher than that of the joints under parallel load. The use of PSB panel and screw increased the ultimate bearing capacity of the joints. Furthermore, based on Johansen yield theory and experimental results, the reliability analysis was carried out through first-order reliability methods. The results showed that the SPF-nail joints, the PSB-nail joints, and PSB-screw joints achieved the reliability requirements.

International competitiveness of the furniture manufacturing– lesson from the selected Eu countries

This study aims to compare and evaluate the international competitiveness of the furniture industry in the selected European Union (EU) countries using chosen result-oriented indicators. The results found that countries with the highest levels of international competitiveness of the furniture industry included Poland, Romania and Italy. In contrast, the comparative advantage of Germany, which is the largest furniture exporter in the EU, was not as significant. No comparative advantage in the furniture trade was observed in France and United Kingdom, which is confirmed by the negative values of the Relative Trade Advantage (RTA) index and by unfavorable values of the export specialization index. The results presented in the article expand the existing knowledge in the area of assessing the international competitiveness of the largest furniture exporters.

Wood-based sandwich panels: A review

A sandwich panel with a high ratio of strength to weight is commonly used in aerospace, construction, packaging and other fields. Using a renewable material such as wood to make sandwich panels can achieve a perfect unity of material and structure. In view of the lack of systematic analyses of wood-based sandwich panels, this work reviewed the development of wood-based sandwich panels. Based on the core structure, these panels can be divided into hollow-core structures and solid-core structures. With the emergence of new materials and new technologies, new wood-based sandwich products had been created. However, the current research only focused on the manufacturing, and the related novel design was still lacking. This work put forward a research idea of bionic design based on the integration of structure and function and pointed out the research direction for wood-based sandwich panels.

Short notes: Application of mineral filler in medium density fiberboard (Mdf) and its effect On material properties as a function of particle size

The addition of inorganic filler material in medium density fiberboard (MDF) and the effect on material properties as a function of particle size was examined. Medium density fiberboard was manufactured in a laboratory scale environment to a target raw density of 750 kgm-3. Wood fibers were replaced by using calcium carbonate at 3 and 10 wt.% using fillers with weighted median particle sizes of d50 = 2.0 μm and d50 = 30 μm, respectively. Urea formaldehyde resin was used as binder in all MDF. The influence of filler addition on the modulus of elasticity, bending and tensile strength, dimensional stability and liquid permeability was investigated. The results demonstrate the effect of filler content and its dependence on particle size. The addition of filler with d50 = 30 μm does not have any influence on material properties up to a filler content of 10 wt.%. Using the finer filler with d50 = 2.0 μm at 10 wt.% filler, the quantity significantly increases the water adsorption and swelling behavior and reduces the strength properties of the MDF.