European Journal of Wood and Wood Products

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Online ISSN: 1436-736X
Print ISSN: 0018-3768
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  • Annette HafnerAnnette Hafner
  • Özlem ÖzdemirÖzlem Özdemir
The construction sector is a central source of greenhouse gas (GHG) emissions. Reducing environmental impacts along the life cycle of buildings is therefore an important target. Given recent innovations in low-energy buildings and energy supply systems with low climate impacts, additional reduction potential can mainly be found in mitigating GHG emissions in other life cycle stages. The focus of mitigation has thus shifted to emissions related to material input, and comparative life cycle analyses of buildings constructed with different material types are becoming increasingly relevant in guiding regulations to achieve emission reduction targets. This paper performs comparative life cycle assessments for 48 non-residential buildings, comparing GHG emissions according to the current European standardised calculation methods. A substitution potential is introduced to evaluate the advantage of using timber as a building material. Furthermore, a comparative method is presented for assessing the substitution potential on the building level. The results show that the substitution potential for the construction of the studied buildings ranges from 5 to 48%. Specific substitution potentials are differentiated between four subcategories of non-residential buildings. The lowest substitution potential was identified for agricultural buildings and the highest for office and administration buildings. Moreover, the current research shows that the specific materials, construction, the geometry and design all affect the substitution potential of a building. On the basis of these values, it is possible to make projections regarding GHG reduction potential in the construction sector on a national scale.
 
The size of wood is reduced by splitting or chipless cutting whilst logging trees, limbing, or preparing wood to be a fuel, for example, or in order to improve the efficiency of wood drying processes. Low costs of wood processing are desirable in each of these processes. The article presents experimental and simulation tests run in ABAQUS software, which allow for an analysis of the geometry of cutting tools used during the splitting or chipless cutting of wood in order to determine the cutting force and driving force of the machine executing such a process. The tests involved wood of Pinus sylvestris L. (moisture content: 8.74% ± 0.1%) in four configurations (chipless cutting transverse to the fibres (90°–90°), splitting along the fibres (0°–90°), splitting radially to the grain (90°–0°) and splitting tangentially to the grain (90°–0°)). Analysis of the force and strength of the blade proved that an effective tip angle of the knife blade falls between 30° and 45°. The presented results also suggested that splitting wood along the fibres (0°–90°) is preferable in a machine process, while splitting tangentially and radially to the wood grain (90°–0°) is preferable when splitting wood using manual tools.
 
Mean vertical density profiles of OSB panels made from (1) black spruce with a unidirectional single layer (A), three layers with a nondirectional core layer (B), and cross-oriented three layer (C) structures; (2) 50% spruce/50% aspen strands with a unidirectional single layer (D), three layers with a nondirectional core layer (E), cross-oriented three layer (F) structures; (3) cross-oriented three-layer panels with a mixed spruce-aspen core layer (SMS) with proportions of 40% (panel G), 50% (H), and 75% (I); (4) cross-oriented three-layer panels with a black spruce core layer (MSM) with proportions of 40% (J), 50% (K), and 75% (L)
Vertical (above) and cross section (below) images of cross-oriented three layer OSB panels made from (1) black spruce; (2) 50% spruce/50% aspen strands; (3) mixed spruce-aspen core layer and black spruce surface layers (SMS); (4) black spruce core layer and mixed spruce-aspen surface layers (MSM)
Vertical porosity profiles (VPP) of OSB panels made from (1) black spruce with a unidirectional single layer (A), three layers with a nondirectional core layer (B), and cross-oriented three layer (C) structures; (2) 50% spruce/50% aspen strands with a unidirectional single layer (D), three layers with a nondirectional core layer (E), cross-oriented three layer (F) structures; (3) cross-oriented three-layer panels with a mixed spruce-aspen core layer (SMS) with proportions of 40% (G), 50% (H), and 75% (I); (4) cross-oriented three-layer panels with a black spruce core layer (MSM) with proportions of 40% (J), 50% (K), and 75% (L)
Void size distribution of OSB panels made from (1) black spruce with a unidirectional single layer (A), three layers with a nondirectional core layer (B), and cross-oriented three layer (C) structures; (2) 50% spruce/50% aspen strands with a unidirectional single layer (D), three layers with a nondirectional core layer (E), cross-oriented three layer (F) structures; (3) cross-oriented three-layer panels with a mixed spruce-aspen core layer (SMS) with proportions of 40% (G), 50% (H), and 75% (I); (4) cross-oriented three-layer panels with a black spruce core layer (MSM) with proportions of 40% (J), 50% (K), and 75% (L)
Water absorption (WA) of OSB panels made from (1) black spruce with a unidirectional single layer (panel A), three layers with a nondirectional core layer (panel B), and cross-oriented three layer (panel C) structures; (2) 50% spruce/50% aspen with a unidirectional single layer (panel D), three layers with a nondirectional core layer (panel E), cross-oriented three layer (panel F) structures; (3) cross-oriented three-layer panels with a mixed spruce-aspen core layer (SMS) with proportions of 40% (panel G), 50% (panel H), and 75% (panel I); (4) cross-oriented three-layer panels with a black spruce core layer (MSM) with proportions of 40% (panel J), 50% (panel K), and 75% (panel L)
The internal structure of oriented strand board (OSB) is made of a large number of voids. This results from the complexity of strand distribution within the panel and impacts panel performance greatly. In this research, X-ray microcomputer tomography was used to investigate the void characteristics of OSB panels with different structures. The results indicated that OSB panels have a porosity profile opposite to that of density. Unidirectionally oriented homogeneous boards showed slightly higher total porosity, a steeper porosity profile, and higher void size than other three-layer boards. Still, there was no significant difference between them. Although the changes in bending properties resulted from changes in core layer strand orientation, the slight difference in internal bond and water absorption rate was caused by the narrower void distribution and a larger void size. Panels containing a mixture of black spruce and aspen strands had a higher porosity, a steeper porosity profile, and a small void size compared to panels with black spruce strands. This resulted in better bending properties, worse internal bonding, and a lower water absorption rate and thickness swelling. Thus, the internal bond, water absorption rate, and thickness swelling of the panels with a mixed spruce-aspen core layer decreased with an increase in core layer proportion. An opposite trend was observed for panels with a black spruce core layer.
 
This work presents the experimental study of natural drying and cracking of green wood slices of two tropical species. The tests were carried out on slices of Aucoumea klaineana P. and Pterocarpus soyauxii at uncontrolled temperature and relative humidity. To follow the strains, specifical targets were drawn on the slice in the radial and circular directions. The slice was placed in front of a camera to record the mass loss on a control specimen and to follow the displacement of the targets on a regular basis until the end of the tests. As results, the evolutions of radial and tangential displacements were calculated in a cylindrical coordinate and the fiber saturation point was deduced accordingly. In addition, the initiation and the crack propagation were followed in a green wood slice subjected to natural drying. At the end, finite element model was developed , and the obtained results were compared to experimental data. The results help to better understand and anticipate the behavior of green wood slices during desiccation. In addition, the potential areas of appearance and propagation of cracks were identified to reduce and prevent defects resulting from the primary processing of wood.
 
In this paper, orthogonal cutting of wood-plastic composites (WPC) was carried out experimentally, focusing on the trend and fluctuation of cutting force and temperature with the influence of cutting parameters during the cutting process and combined with the chip formation to reveal the processing mechanism of WPC. The effects of cutting parameters on cutting force and cutting temperature were strikingly similar; with the increase in rake angle and decrease in cutting depth, the numerical value and fluctuation of cutting force and cutting temperature were all decreased. In addition, a decreasing trend in the angle between chip formation and the rake face of the tool was observed by a high-speed camera. The cutting heat will be more concentrated in the chip during the cutting process because of the lower coefficient of thermal conductivity of WPC, so the cutting temperature of the cutting edge was always lower than the temperature of the chip area. After machining, the surface quality was linearly related to the tool rake angle, but not the cutting speed and cutting depth. Therefore, the established response surface model can better fit and predict surface quality. The cutting process was complex and fluctuating, so appropriate cutting parameters were required to carry out stable and efficient machining and produce good cutting quality. Thus, it is promising for WPC’s high-quality and stable cutting.
 
To prevent the degradation of outdoor wood products such as wood decks, it is vital to keep them dry. Weathering induces checks on wood surfaces. Surface checks gather water and maintain a high moisture content, causing decay of the wood. Herein, water absorption and redrying tests were performed on wood specimens with slits and simulated surface checks, and the moisture content distribution on a cross section was obtained using X-ray densitometry. On redrying of the slit, two levels of slit depths (10 and 20 mm) were tested under four redrying conditions: three humidity levels with no airflow and a medium humidity level with a wind velocity of 1 m/s. The redrying rate and moisture trapping time that kept moisture content greater than 20% were used to estimate the moisture trapping risk in the surface check. The moisture trapping risk was found in the no-wind condition until 48 h redrying or longer, independent of the slit depth. Conversely, in the forced-air condition, an air-dried state was observed within 24 h. The redrying rate in the 10 mm depth slit was influenced by ambient humidity levels; however, the redrying rate in the 20 mm depth slit was unaffected. Overall, while a deeper check has a higher risk of moisture trapping, if the wood is in a poorly ventilated environment with a high ambient humidity level, a shallow check with a 10 mm depth may also be at risk.
 
Polydimethylsiloxane (PDMS) and hydrophobic silica nanoparticles (HSNP) were applied to coat wood surfaces to decrease boron release from DOT (disodium octaborate tetrahydrate) treated wood. The surface-modified specimens were then subjected to a 14-day-leaching course followed by mold resistance tests under laboratory conditions. Water absorption, dimensional stability and water contact angle of the modified wood specimens were then determined. FTIR analysis and SEM imaging were also performed for characterization of the modified wood surfaces. Retention level of 3.3 kg/m3 was retained in the DOT and PDMS-treated wood specimens after the leaching process, but nearly no boron remained in the wood specimens treated with DOT only and DOT + HSNP. In accordance with leaching tests, the DOT and PDMS-treated specimens showed highest performance against mold fungi even after leaching tests; however, no complete protection was achieved in both DOT + HSNP and DOT-only treated specimens. The PDMS and HSNPs coated wood samples displayed water contact angles of 114° and 172°, respectively. The comparison of chemical, wetting and structural characteristics of the modified wood samples before and after leaching showed similar behavior. More detailed research is needed to obtain a better understanding of the mechanisms of interaction between PDMS/HSNP and wood surfaces.
 
This study explored the feasibility of the finite element method (FEM) and Hankinson formula to predict the compressive properties of cross-grain wood with a wide range of moisture content, avoiding the waste of materials and time in experimental methods. This study examined the influence of moisture content and cross-grain orientation on the elastoplastic performance of beechwood under compressive loads. The comparison of compressive load–displacement curves between the experiment and FEM was achieved, and the relative errors of compressive yield strength or modulus of elasticity between the experiment and FEM. The stress concentration distribution and failure models of different principal planes were analyzed. It demonstrated that the FEM could simulate compressive elastoplastic properties of wood with 45º cross-grain and a broad range of moisture content. For cases of 45º cross-grain orientation, comparisons between the experimental data and FEM, and Hankinson formula, were conducted which validated that the Hankinson formula can predict beechwood’s compressive yield strength and elastic modulus with multilevel grain orientations and moisture contents. Regression models were established based on the Hankinson formula to forecast the compressive yield strength or modulus of elasticity for a broad range of moisture content and random grain direction. This study can assist in the rational utilization of cross-grain timber in terms of structural optimization of outdoor wood products.
 
To elevate performance of bamboo flour/high-density polyethylene (BF/HDPE) composites, poly(catechol/amine) (i.e., an adhesive material inspired by mussel adhesive proteins) treatment of BF was researched for the first time. Influence of monomer type was surveyed by applying three representative monomers, i.e., catechol/diethylenetriamine (catechol/DETA), catechol/triethylenetetramine (catechol/TETA), and catechol/tetraethylenepentamine (catechol/TEPA). All the monomers constructed poly(catechol/amine) coatings on BF. Among treated BF, poly(catechol/amine) uploading was 7.21–15.16%, which enlarged the average diameter of BF by 17.53–24.33%. After treatment, the potential of BF to interact with other substances was raised. When using different monomers, fractal dimension and specific area of BF surface were promoted by 3.58–4.31% and 14.08–16.81%, respectively; catechol/DETA and catechol/TEPA also reduced water-BF contact angle by 4.05–6.03°, and increased adhesion work by 8.50–12.69%. The treated BF showed a better interfacial bonding with HDPE, which was verified by physical–mechanical properties of composites. With the change of catechol/amine, composites made from treated BF exhibited a decrease in pore volume and 720 h water absorption by 6.71–15.49% and 42.57–46.54%, respectively, and an increase in flexural strength and distortion temperature by 13.13–23.14% and 3.60–7.30 °C, respectively. Overall, the optimal property enhancement for composites was observed in poly(catechol/TEPA) treatment.
 
The growth ring boundary substantially affects the mechanical performance of wood. Glue impregnation has been widely applied to wood protection. Shear strength of the growth ring boundary with and without glue impregnation under normal pressure (NP) and vacuum pressure (VP) conditions was measured using the lap-shear test, meanwhile strain distribution was recorded with digital image correlation. Glue distribution and microstructure in the specimens were visualized using scanning electron microscopy. Glue impregnation can switch specimens’ failure location from growth ring boundary to earlywood or notches. Compared to the control specimens, shear strength and breaking elongation in VP specimens are significantly higher. Looking at the ruptured cross section, there are less ruptures in the control specimens and they are sharper and cleaner than in NP and VP specimens. In NP and VP specimens, the relationship between strength and elongation consists of four sections. In control specimens, the relationship between strength and elongation includes two sections. More sections could be due to residual stress from impregnation processes and breakage of glue. Such mechanical performance relates to the fact that tension strain is much larger than shear strain in NP and VP specimens, which protects the specimens from failing in the growth ring boundary.
 
Presently, the recycling potential of wood aggregates (WA) is limited. However, their utilization appears to be a viable alternative for building insulation. Recycled wood aggregates in composite materials are usually used in cement as a matrix. The present research focuses on the possibilities of their recycling in the plaster matrix. Wood aggregates/plaster (WAP) composites are prepared with varying WA densities (0; 5; 10; 15; 20 by volume). Four sodium hydroxide (NaOH) solution concentrations (1, 2, 6, and 10%) are used to treat WA at 80 °C for 2 h. Thermal and mechanical properties of newly treated bio-aggregates composites were investigated. Results show that the use of untreated WA makes the composite lightweight and enhances the thermal insulating performances of plaster paste but negatively affects its mechanical strengths. An optimal chemical surface modification of WA improves the flexural and compressive strengths and decreases the water uptake of resulting composites. The adequate treatment process (2% NaOH concentration at 80 °C during 2 h) of wood aggregates was proven when comparing treated and untreated fibers’ morphology as well as their crystallinity index. Experimental results confirm the possibility to reuse the wood aggregates in new mortars for insulating and building applications.
 
Theoretical background and structure of the survey
Differences between the clusters regarding their level of digitalization based on the digitalization criteria. Three clusters were identified: The manual small business cluster (n1 = 44), the automated business cluster (n2= 30), the solid developed business cluster (n3 = 13)
Perceived challenges for the use of digital technologies in % by cluster (n1 = 44, n2 = 30, n3 = 13)
Perceived opportunities for digitalization technologies in % by cluster (n1 = 44, n2 = 30, n3 = 13)
Three levels of digitalization (modified after Saam et al. 2016)
This study investigates the level of digitalization as well as opportunities and challenges from the perspective of sawmill representatives. The level of digitalization of business processes was assessed by a survey on digitalization criteria regarding business processes. The questions dealt with the existence of basic data processing, digitally networked information and communication and digitally networked products and services. Over 700 small and medium sized sawmills were contacted by e-mail or mail using enterprise directories. The response of 87 completed questionnaires was analyzed by means of cluster analysis. The companies were divided into different groups based on their similarity regarding the digitalization criteria. The study identified three clusters: the first cluster (n 1 = 35), the “manual small business”, did not reach the first stage of digitalization. The second cluster (n 2 = 26), the “automated business”, has partially reached the first stage of digitalization. The third cluster (n 3 = 26), the “solid developed” group, has reached the first stage of digitalization as the basic hardware and software is available. The increasing networking of the value chain, the workplace of the future and the increasing individualization of customer requirements are perceived as opportunities. The main barriers are data protection and data security whereas cloud solutions are considered as the biggest risk.
 
(a) Compreg surfaces before (background) and after 250 and 1,000 h of exposure. Samples with top veneers from European oak (QCXE) and teak (TEGR), either without or with PF overlay (QCXE_O, TEGR_O). (b) Corresponding micrographs of surface areas after 250 and 1,000 h, scale bars represent 1,000 μm; identical areas were recorded in each case
(a) CIELab color changes of Compreg without (QCXE, TEGR) and with PF overlay (QCXE_O, TEGR_O) after 1,000 h of exposure; (b) Relation between gloss levels and total color change of Compreg without and (c) with PF overlay; arrows indicate weathering progress (texp = 0 … 1,000 h)
The weather resistance of Compreg surfaces depends on various factors, such as top veneer type, impregnating resin, and protective topcoats. Artificial weathering tests were performed for the first time on material types with oak and teak top veneer surfaces. Both showed strong surface brightening due to resin degradation and subsequent photobleaching of the exposed veneer surface. Directly pressed, phenolic resin-impregnated cellulose paper overlays caused significant surface stabilization.
 
In this research, the feasibility of producing flexible plywood employing combinations of poplar (Populus deltoides) and Paulownia (Paulownia fortunei) veneers with thickness of 1 and 2 mm was investigated. For this aim, layer combinations, treatment type, and the resin type were chosen as variables. Laboratory panels were produced based on Taguchi design of experiments (L18;6^1 3^2) and some physical and mechanical properties of the specimens including density, moisture content, water absorption and thickness swelling after 24 h of immersion in water, modulus of rupture and modulus of elasticity parallel and perpendicular to the grain, bonding quality, and bending radius were determined. The present work focuses on using Taguchi method in order to detect the optimum combination of the parameters. The results revealed that bending radius was considerably influenced by the properties of wood and the thickness of the core veneer. The outcomes showed that as the thickness of the core veneer decreased, the bending radius increased. Accordingly, the optimum choice for the core layer of plywood is poplar with a thickness of 1 mm, and the best elastic attributes were obtained for plywood with veneers treated by the Pro-Glu solution. Polyvinyl acetate also demonstrated an increase in flexibility, and a decrease in MOE. The experimental samples of the manufactured plywood could ultimately bend around a cylinder with a diameter of 6.5 mm to reach the minimum bending radius with no sign of damage.
 
The current market of timber products shows a clearly identifiable dominance of rectangular cross sections in modern timber buildings. To promote roundwood as addition to commonly used wood and wood products, this paper presents experimental investigations serving for axial connectors in roundwood truss structures. Glued-in threaded rods, bonded parallel to grain into Douglas fir (Pseudotsuga menziesii) softwood, represent the basis of this research. To increase the load-carrying capacity and usability of this connection technique in roundwood, a resin-bonded polymer concrete (PC) with an increased bondline thickness and contact surface to timber was investigated. The pull out strength and embedment stiffness of the new modified bonded-in rod connection was studied on Douglas fir roundwood specimen exposed to different service conditions. The study also determined the influence of wood defects and moisture content before testing. The results show a larger single-fastener capacity, also for higher moisture content applications, compared to traditional glued-in rods. The quality of the adhesive bondline, for example bonding length, hardening process and homogeneous adhesive bond could be verified by visual inspection.
 
Proper surface pre-treatment plays an important role for good compatibility between the wood and the coating. The present study aimed to determine the correlations between the type of surface pre-treatment and the wettability for unmodified and thermally modified beech (Fagus sylvatica L.) wood with water and water-based coatings. A new approach to evaluate the water permeability of coating systems was developed by investigating the wettability of wood samples using the multicycle Wilhelmy plate method in combination with immersion of the coated samples in water. The treatment with non-thermal plasma made the wood surfaces more hydrophilic and treatment with organic solvent made the surfaces more hydrophobic. The poorer wettability and sorption with water and coatings in thermally modified wood was clearly related to the altered chemical composition of wood. As the water content in coating increased, the amount of absorbed coating in the wood decreased. The surface pre-treatments had no effect on the colour of the coated wood. The higher water content in the coating negatively affected the water protection performance of the coated wood. The thinner coating films correlated with greater water absorption in the coated wood, generally resulting in microscopic delamination between the wood substrate and the coating films.
 
The interpretation of the outputs of acoustic tomography is often altered by different physical and mechanical parameters. Detailed information on the relationships between static mechanical properties and dynamic parameters of intact and degraded green wood can improve the results of this device-supported method used for tree stability assessment. This research presents a graphic and statistic comparison of acoustic tomography outputs with the laboratory assessed material parameters. The analysis was based on the relationship between the dynamic and static mechanical parameters of four cross-sections from two living tree stems. The occurrence of seven white and soft rot fungi was taken into consideration. The influence of density ( $$\uprho$$ ρ ) on stress-wave propagation ( $$v$$ v ) was proved. A strong correlation between the dynamic moduli of elasticity ( $${E}_{dyn}$$ E dyn ) and compressive strength ( $$\upsigma$$ σ ) is reported. A higher heterogeneity of wood degradation among the cross-section can lead to an underestimation of the defect during AT assessment. The dynamic modulus of elasticity $${E}_{dyn}$$ E dyn was less influenced than $$v$$ v by the heterogeneity of degraded wood. Therefore, $${E}_{dyn}$$ E dyn can be used to form a better interpretation of acoustic tomography assessment of standing beech trees. Due to the complexity of the topic, further investigation of previously mentioned relationships is still needed.
 
Mathematical models are essential for the development of schedules for the air-circulation drying of timber in Swedish sawmills, but earlier models have been shown to be conservative leading to longer drying times than necessary. In the current study, macroscopic (macro) X-ray computed tomography (CT) has been used in both the development and validation of a finite element (FE) model, to enable the macro-CT aided FE modelling of the nonlinear transient moisture flow in wood. The model uses more advanced theory than has previously been used in Swedish sawmills, by incorporating a surface emission coefficient to simulate the surface resistance to moisture flow. A single piece of Norway spruce [ Picea abies (L.) Karst.] timber was subjected to that part of a traditional kiln-drying schedule, which is associated with diffusion-driven moisture transport. The incorporation of macro-CT data into the FE model resulted in a more realistic representation of the board’s geometry, the initial moisture state, and the definition of material parameters. It also led to a better simulation of flow speed and moisture gradient, especially the asymmetric MC development within the cross section throughout the drying process.
 
The material removal in wood sanding is associated with the chip formation and flow, which is directly influenced by grits cutting geometries. Hence, typical single grits with conical, triangular pyramid (3 M) and pentagonal pyramid (5 M) cutting geometries were selected to experimentally simulate wood sanding on sugar maple wood (Acer saccharum). The results of dynamic chip formation showed that only 3 M geometry produced discernable continuous chips. Combined with the scratch morphology and the cutting force ratio, more cutting actions occurred for 3 M geometry, while the conical and 5 M geometry induced material compression and better surface quality. According to the established force model and the result of specific energy, the work done by tangential cutting force Ft to compress and densify wood material by the conical and 5 M geometry was similar and even larger than the work done by Ft to make debris caused by the 3 M geometry. Besides, less oscillation of Ft suggested that the 5 M geometry performed more stable negative-rake cutting. It can be concluded that the grit cutting geometry has a notable effect on the chip formation, surface quality and energy dissipation.
 
Transverse surfaces produced by chainsaw (left) and circular saw (right) of Amazonian wood specimens
Average values by species of the spectra collected on the surfaces of the wood produced with a chainsaw (M) and circular saw (S)
PCA of spectral data treated with the 1st wood derivative from six native Amazonian species considering the type of surface finish
PCA of spectral data treated with the 2nd derivative of wood samples from 6 native Amazonian species considering the surfaces produced with a chainsaw (A) and circular saw (B)
The need for fast and reliable methods to determine wood-producing species at risk of extinction in tropical forests has become increasingly evident. The aim of this study was to evaluate the potential of near infrared (NIR) technology to identify these types of wood species in Amazon forests by developing multivariate models for the spectral signatures of wood specimens processed by circular saws and chainsaws. Three trees of six species from the Legal Amazon were evaluated (Manilkara elata, Dinizia excelsa, Goupia glabra, Hymenaea sp., Micropholis melinoniana and Copaifera sp.), of which 350 wood specimens were cut with chainsaws and circular saws. The processing-type effect on the information quality recorded on wood surfaces was evaluated in terms of the performance of the classification of tropical wood species through cross validation and independent sets based on partial least squares-discriminant analysis (PLS-DA). The results indicated that PLS-DA models based on spectral signatures recorded on wood surfaces processed with a circular saw achieved a higher percentage of correct classifications (99.2%), while models based on spectral signatures taken from wood surfaces processed with a chainsaw correctly classified 95.2% of the specimens. This study suggests that unknown wood samples belonging to these species can be correctly and satisfactorily preclassified regardless of the tool used for sampling the wood before identification, inspection and commercialization operations.
 
This study investigated the use of deep eutectic solvents (DESs) to improve the accelerated weathering performance of Scots pine (Pinus sylvestris L.) wood. In addition to being natural and easily obtained, the simple preparation of these solvents via heating and mixing has led to their use in a pretreatment process. The DES solutions were prepared by mixing, in different molar ratios, oxalic acid (OA) and acetic acid (AA) as hydrogen bond donors (HBDs) and choline chloride (ChCl) and betaine (BT) as hydrogen bond acceptors (HBAs). In this study, the novel DESs were prepared and characterized. Scots pine wood samples prepared in dimensions of 15 (radial) × 75 (tangential) × 150 (longitudinal) mm were treated with the DES solutions at 150 °C for 2 h. The weathering effects on the surface characteristics and morphology of the samples were examined by means of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and measurement of color, gloss, and surface roughness. Weathering was carried out via cycles of 8-h UV-light irradiation and 15-min water spraying followed by 3.45-h conditioning in an accelerated weathering test cycle chamber. According to the FTIR results, the lignin ratio decreased significantly in the wood samples subjected to 2-h pretreatment at 150 °C. The results showed that the greatest color change occurred on the surfaces of the control samples, whereas the least color change was observed up to 168 h on the OA-BT samples. The glossiness values increased with the first 168 h of weathering. Thereafter, the gloss values of the samples treated with OA-BT and OA-ChCl remained stable. The surface roughness and degradation of surface components rose with the increase in the weathering exposure period. In accordance with the color and surface roughness measurements, the FTIR spectra proved that for all specimens, lignin continued to degrade on the exposed surfaces throughout 168 h of accelerating weathering.
 
Densified Pinus sylvestris wood was prepared via densification treatment at different compression pressures, and the flame retardancy and heat-insulating property of the resulting densified Pinus sylvestris wood are investigated by various analytical methods. The results verify that the densification treatment has a negligible effect on the composition and chemical structures of the wood, while the flame retardancy, smoke suppression and heat-insulating properties of wood are significantly increased. However, an excessive compression pressure will destroy the porous structure of wood, which results in the decrease in flame-retardant efficiency of the densified wood. When the compression pressure reaches 10 MPa, the resulting specimen presents the lowest fire hazard, which has 9.8% reduction in total heat release (THR), 37.1% reduction in total smoke release (TSR) and 25.9% reduction in equilibrium backside temperature at 2400 s compared to natural wood. Char formation analysis shows that the enhanced flame retardancy of densified wood can be attributed to a lower contact area between the wood and high-temperature environment accompanied with the generation of a strong and thermally stable char layer rich in aromatic and cross-linking structures. These attractive features of densified wood effectively reduce the transfer of heat and combustion rates when exposed to flame, resulting in better fire-retardant and heat-insulating properties during combustion.
 
Application of OSB panels in civil construction: roof covering (a-b) and walls (c). Source: Adapted from LP CORP (2021)
Main degradation agents and reactions that occur when wood is exposed to nature. Source: Adapted from Rowell (1983)
Document sources found in this search for the keyword “Oriented Strand Board”
Co-occurrence of all keywords in the publications
Given the need for durable and low-maintenance products, thermal modification has emerged as an environmentally friendly alternative, replacing chemical treatments. Although the literature reports a large number of articles related to the wood thermal treatment, nevertheless there is a much smaller number related to the thermal treatment of Oriented Strand Board (OSB) panels, which are scarce, limited or contradictory. This panel is used as a building material for internal and covered exterior functions in roofs, walls, floors, structural elements and other uses, currently being widely studied. Therefore, this research aims to present a bibliometric and systematic literature review on heat treatment of OSB panels published between 2000 and 2020 in the Scopus database, through extensive bibliographic review and using a simple and integrative systematic, containing its metrics and main findings. It was found that, despite the progressive growth of interest from the scientific community in relation to wood modification, thermal-based modifications still have much less studies compared to other techniques. At the end, gaps, opportunities and potential areas for future research related to thermal modification of panels are presented.
 
The adhesives used in the production of engineered wood products mainly influence the mechanical performance of structural elements. In this context, the present paper aims to evaluate the bonding performance of two different one-component polyurethane adhesives (1C-PUR-A and 1C-PUR-B) in the production of finger-joints made from four planted forest species (Tectona grandis, Eucalyptus grandis, Eucalyptus urograndis and Pinus spp.). Tensile tests were performed to evaluate the strength and failure modes of seven combinations of structural adhesives and wood species from planted forests in Brazil. The finger-joints made from hardwood species (T. grandis Group 1: 35.1 MPa, E. grandis: Group 2: 45.5 MPa; Group 3: 55.8 MPa, E. urograndis: Group 4: 37.9 MPa; Group 5: 43.0 MPa) presented greater mean value of tensile strength than those made from softwood species (Pinus spp.: Group 6: 21.9 MPa; Group 7: 24 MPa). Therefore, the feasibility of using these hardwood species in the production of engineered wood products becomes evident. Moreover, the tensile strength of finger-joints with one-component polyurethane depends on the wood species utilized in the production. One-component polyurethane presented good adhesion in finger-joints made from T. grandis and Pinus spp. given that 90% and 80% of failure mode did not occur on the bondline respectively. On the other hand, the failure mode of finger-joints made from Eucalyptus spp. occurred mainly on the bondline of one-component polyurethane adhesives.
 
A Dou-gong joint is one of the essential components in traditional Chinese timber structures. This work investigates the seismic performance of Dou-gong joints under cyclic loading through experiments and model calibration. Four full-scale joints were subjected to cyclic loading to study the failure mechanism and ability to dissipate energy. The test results indicated that a Dou-gong joint will finally fail with a large overall tilt. The Dou-gong joint itself had a strong ability to dissipate energy through shear deformation and the extrusion of different components. The maximum load-bearing capacity in the Y direction was larger than that in the X direction because the Dou and Xiao components perform better in the Y direction than in the X direction. A macro model whose nonlinearity was governed by a spring element was used to model a Dou-gong joint. The spring element was separately assigned to two different hysteretic models, and the model parameters were calibrated using the tested data. Both the advantages and disadvantages of the two hysteretic models are compared and discussed. The obtained seismic performance of a Dou-gong joint provides useful and valuable information to maintain and retrofit historic Chinese timber structures.
 
The resins developed with Fillaeopsis discophora tannin extract using either Vitellaria paradoxa trunk exudate as bio hardener or glyoxal as hardener were thermally analyzed using thermomechanical (TMA) and thermogravimetric (TGA) analysis. A microscopic interpretation of glass transition, physical aging, and phase segregation was analyzed and the relative activation energy was determined. The activation energies of gelling of the resins above are 57,658 and 52,967 J. mol⁻¹, respectively. Their glass transition temperatures are 172 °C and 149 °C respectively. The tannin extract used in the development of these two resins is of a condensed polyflavonoid type linked to some furan residues. The resin developed with the Vitellaria paradoxa exudate as a bio-hardener has a good thermal behavior and it degrades slower than that with glyoxal as hardener.
 
This paper presents the results of static and dynamic crushing of wood tubes made of poplar, birch and oak veneer. Despite different veneer thicknesses (poplar: 1 mm, birch: 0.5 mm and oak: 0.75 mm), the tubes have the same overall dimensions to enable comparisons. The static tests were carried out on an MTS 100 kN machine between two loading plates and the dynamic tests were carried out on a drop weight testing machine. The dynamic specific energy absorption is, on average, 32 J/g, 35.5 J/g and 38.5 J/g for poplar, oak and birch, respectively. The energies absorbed in dynamic tests for poplar, oak and birch are on average 1581 J, 2544 J and 3245 J, respectively. These characteristics, which are quite comparable with those of tubes made of composite materials, show that these materials are serious candidates for energy absorption at low carbon cost and with renewable materials.
 
Exterior cladding boards benefit from a known service life that makes planning of maintenance and replacement procedures easier. Among the different wood modification methods, surface charring of wood is expected to increase the lifespan of wooden elements in building façades. This paper reports the properties of surface charred Norway spruce, Scots pine and Silver birch in Southern Finnish climate over a natural weathering period of one year. Several modifications were examined, namely variants of contact and flame charring. These also included oiled and brushed surfaces. The flame charred samples of spruce and birch withstood the weathering well, with some minor flaking and cracking. The thick pine samples cracked extensively regardless of modification, raising questions on suitable density and thickness of wood destined for a charring modification. Contact charring did not seem suitable for outside uses at least in direct sunlight, as the colors faded, and surfaces cracked within all examined groups. The spectroscopical methods employed also revealed degradation of contact charred wood lignin, whereas the flame charred surface consisted mostly of recalcitrant carbon structures rather inert towards weathering. This highlights the importance of sufficient structural degradation of wood components in creating a weathering resistant surface, and also shows that a thicker thermally modified layer does not necessarily improve the weatherability in contact charred wood.
 
A composite mixture of wood fiber and sodium silicate (SS) binder has been explored as a viable material for use in additive manufacture of wood based composite materials. Mixtures of 50–60% wood fiber and 50 − 40% SS were explored. The curing behavior of these formulations were examined by differential scanning calorimetry (DSC) and dynamic rheometry. An exothermic curing peak of 83 °C was observed for SS and increased to 153 and 163 °C with the addition of wood fiber. Rheology flow curves showed higher viscosity values for 50/50 blends and lower values for SS. A custom extrusion system was fabricated and 50/50 wet blends were extruded, cured at different temperatures, and characterized for flame retardancy, mechanical, thermal, and water absorption properties. Surface chemistry changes before and after curing were determined by Fourier Transform Infrared (FTIR) spectroscopy. Mechanical properties, determined by three-point bend testing, improved with the addition of the wood fiber but varied with different curing temperatures and thermal stability of the composites increased with curing temperature. This extruded wood-SS composite shows promise for use in additive manufacturing.
 
Wood bond strength and its durability under unstable climatic conditions is a critical factor for engineered wood products. This article aims to identify the efect of alternating freezing and high temperatures on the tensile-shear strength of adhesivebonded wood. Emulsion polymer isocyanate and one-component polyurethane adhesives were used to bond European larch (Larix decidua Mill) and Norway spruce (Picea abies (L.) H. Karst.). The thermal loading of glued samples was carried out at temperatures of −15 °C/70 °C and −25 °C/70 °C. The tensile-shear strength was determined on the glued samples with a universal testing machine. The results showed that the tensile-shear strength of the glued wood exposed to −15 °C/70 °C and −25 °C/70 °C remained unchanged compared to that of reference samples. A negligible correlation was found between the thermal loading and the shear strength of glued samples.
 
Mostly the effect of solar and UV radiation on wood photodegradation has been researched. This paper discusses the effect of artificial light sources, which differ in the spectral composition of the emitted light, on the photodegradation of wood. Ash, birch, aspen, pine sapwood and heartwood, and spruce wood were exposed to two LEDs of different colour temperature (3000 and 6500 K), incandescent and fluorescent lamps. Changes in colour (ΔE) and colour parameters L*, a*, b* (CIELAB colour space) as well as reflectance and FTIR spectra were analysed to evaluate the photodegradation of wood depending on the light source. According to the results of changes in the chromaticity system of woods, the tested light sources can be divided into two groups: one group with similar results includes the two tested LEDs while the other group includes incandescent and fluorescent lamps. Lower irradiation dose was needed for the LEDs to impart visually perceptible discolouration, whereas colour changes of greater magnitude were caused by the incandescent and fluorescent lamps at higher irradiation doses. It was detected that depending on the light source, there are differences in the changes in the chromophores between hardwoods and softwoods, with more total discolouration observed for softwoods. The transformations in the chemical structure, which was analysed by FTIR, considerably differed for all tested light sources with a general trend of the greatest effect of the fluorescent lamps followed by the incandescent lamps and LEDs.
 
Regarding mechanics, wood is one of the most efficient materials available. Due to its unique combination of composite and cellular microstructure, it exhibits superb specific mechanical properties which exceed many man-made materials. However, concerning absolute mechanical properties, wood is often inferior to metals and novel engineered composites. Since many wood properties are strongly correlated with its density, densification is a promising pathway towards improved absolute mechanics. Spruce, beech and poplar wood were densified in a two-step process. First, amorphous wood polymers were partially extracted according to an alkaline (AL) and an organosolv (OS) protocol. Subsequently, partially delignified veneers were densified by hot pressing in tangential direction. After densification, average densities increased to 1.00–1.20 g cm ⁻³ . FTIR analysis confirmed chemical changes, mostly in the bands attributed to hemicelluloses and lignin, of chemically treated and hot-pressed veneers. To evaluate the modification process regarding mechanics, tensile and bending properties were characterized and revealed promising results. Compared to untreated control specimens, stiffness and strength tested in tension and bending improved, regardless of wood species and pretreatment. Regarding average tensile properties, the OS treatment improved stiffness, up to 40 GPa, whereas the AL treatment improved strength, up to 300 MPa. Set-recovery tests showed, that chemically treated and densified samples exhibited a better dimensional stability compared to H 2 O-soaked and compressed specimens. However, 24 h water soaking resulted in excessive thickness swelling. This might be a major drawback of partially delignified and densified wood and should be considered in a material selection process.
 
The pretension force for bolted timber joints increases the frictional resistance between the clamping wood and steel plate. Increasing the frictional resistance improves joint stiffness and strength. External tensile load causes the pretension loss in bolted timber joints, but this mechanism remains unclear. This study investigated the mechanism of pretension-bolted timber joints with different pretension forces and clamping part lengths under external tensile loads. Nonlinear finite element analysis (FEA) was conducted. The FEA results were validated by comparison with the experimental results. The separation behavior and mechanism of the clamping wood were also investigated using the FEA results. Moreover, the applicability of conventional theoretical models of the load factor, which is an index for evaluating the pretension loss of bolts, to bolted timber joints was investigated for their practicality. The FEA results provided a good prediction of the initial stiffness, maximum strength, and load factor for the experimental results. The FEA results also showed that increasing the pretension force of the bolt and the length of the clamping wood delayed the onset of separation of the contact interface.
 
Weighted summary effect sizes (average value ± deviations) with different characteristics: species (a); heartwood or sapwood (b); mature or juvenile wood (c); natural or plantation wood (d); density (e) and plane (f). n is the number of studies contributing to each characteristic. P ≤ 0.05 indicates that the summary effect was significantly different from the average value (same for Figs. 2 and 3)
Weighted summary effect sizes (average value ± deviations) with different characteristics: treatment time (a); treatment temperature (b); MC prior to treatment (c); treatment agent (d); and vacuum condition (e)
Weighted summary effect sizes (average value ± deviations) with different characteristics: gaseous agent (a); and liquid agent (b)
Relationships between chromatic parameters (L*, a* and b*) and variables (density, time and temperature)
An attractive darker colour is an important advantage of heat-treated wood. The variation in colour of the heat-treated wood is influenced by the heterogeneous structure of wood and the different technologies that can be applied. In this study, chromatic parameters (L*, a*, b* and △E*) were investigated via meta-analysis. The colour of heat-treated wood was species-dependent and associated with the tree age, silviculture method, and wood characteristics (hardwood or softwood, heartwood or sapwood, etc.). With increasing wood density, L* and b* decreased, while △E* increased. In addition, the colour change of heat-treated wood was closely related to treatment factors (time, temperature, agent of treatment). 180 °C was a critical temperature for the evolution of colour changes. Predictions of colour changes were performed by fitting the chromatic parameters with density, treatment time, and temperature. Prediction of the colour of heat-treated wood was feasible based on the results of the meta-analysis. This study showed the quantitative influences of the material and technology related factors on the chromatic properties of heat-treated wood, and the results are helpful for regulating and optimizing heat treatment technology.
 
In this work, the physical and mechanical properties of laminated and densified bamboo elements for use in structural panels were assessed. The physical properties, such as apparent density, water absorption, swelling in radial and tangential directions, the effect of wet–dry cycles on dimensional stability and, surface roughness for un-densified and densified samples before and after wet–dry cycles were studied. Three-point bending tests were also carried out to measure the modulus of elasticity (MOE) and the modulus of rupture (MOR), which was correlated to the fiber distribution profile obtained from image processing of un-densified and densified bamboo samples. In addition, the effect of the bamboo skin (outer layer) on the properties of densified samples was evaluated. The dimensional changes during the wet–dry cycles test started to stabilize after one cycle for un-densified samples and after three to four cycles for the densified samples. The roughness test showed a meaningful variation of surface roughness after one wet–dry cycle for all the samples. The results indicated that densification of bamboo to 34% of densification degree improves both MOR and MOE by up to 81.3% and 36.1%, respectively but sacrifices dimensional stability. Last but not least, it was demonstrated that maintaining the bamboo skin has a positive impact on the all-mentioned analysis and reduces processing steps/costs for the production of high-performance bamboo elements.
 
A reliable and efficient numerical modelling technique is essential to investigate the behaviour of timber and engineered timber products to promote their widespread use in construction. Wood is an anisotropic material and hence its mechanical properties largely depend on grain direction and type of loading i.e., material behaves differently under compression and tension. Material responses under tension parallel and perpendicular to the grain directions have been reported in the literature but the relevant progressive fracture behaviour has been ignored in typical numerical simulations, due to the complexities and uncertainties around modelling as well as lack of reliable test data. Fracture characteristics play a significant role in analysing crack initiation, propagation, and failure modes of timber so that its full potential can be utilised by knowing the post-elastic behaviour. This paper applies and compares four continuum damage mechanics based constitutive material models (MAT-22, MAT54/55, MAT-143 and MAT-261) available in the commercial finite element software LS-DYNA for simulating the post-elastic behaviour of general timber lamella products. Timber was modelled as both orthotropic and transversely isotropic material to simulate the fracture behaviour in tensile load cases. It is shown that the predicted fracture properties correlate well with experimental data. It was observed that all considered built-in continuum damage models in LS-DYNA are able to simulate the elastic response, but MAT-261, which was originally developed for modelling fibre reinforced composite materials, provides a simple yet reliable option for simulating fracture behaviour of timber.
 
Numerous studies are dedicated to the dynamics of the guitar, the challenge of interdisciplinary researchers being to find a better approach to the design and construction of the classical guitar in correlation with the development of mathematical models of dynamic and acoustic behavior. The aim of this paper is to present a comparative study on dynamic behavior of guitar wooden plates in different stages of guitar manufacturing, focusing on how the dynamic response of wooden plates changes with the addition of components and the increase in mass, going from the simple wooden plate to the whole guitar body. Four types of structures (corresponding to four stages of guitar construction) were analyzed, starting from the wooden top plate without stiffening bars, then adding seven radial stiffening bars onto the structure, then the guitar’s main body (including the stiffening bars) was considered, and, in the end, the whole body of the classical guitar (unfinished, without bridge, saddle, nut and strings) was analyzed. The results consist of vibration patterns with nodes and antinodes for each applied frequency, Fourier spectrum, the harmonic overtone components in accordance with geometry complexity and wood species. The novel aspects of this research consist of comparative analysis of the dynamic response of guitar plates in different stages of processing, the contribution of each added component to the acoustic and vibrational behavior of the guitar being highlighted.
 
The objective of this study is to predict the optimum pressing parameters for the best mechanical properties of plywood panels manufactured with polystyrene instead of formaldehyde-based adhesives using artificial neural network (ANN). For this purpose, veneers from four different wood species (beech, poplar, alder and pine) were produced with styrofoam, also known as expanded polystyrene (EPS) in different pressing parameters. For the 6 mm thick wood veneer/polystyrene composite plywood (WPCP) panels, pressing temperature of 130 °C, 140 °C and 150 °C and pressing time of 1 min/mm (total 6 min), 1.34 min/mm (total 8 min) and 1.67 min/mm (total 10 min) were used. Some of the mechanical properties of the WPCP panels such as bonding strength, bending strength and modulus of elasticity were determined according to respective standards. The experimental data used in this study were obtained from a previous study from the authors. By analyzing this data with ANN, the best prediction models were determined. According to the results obtained from the models, the optimum pressing temperature and pressing time values of WPCP panels, which give the best values for all three mechanical properties, are 138 °C and 8.2 min for beech, 139 °C and 10 min for poplar, 147 °C and 7.6 min for alder, and 147 °C and 9 min for pine. Moreover, the highest bonding strength, bending strength and modulus of elasticity values among all groups were obtained from beech WPCP panels as 1.70 N/mm², 110.22 N/mm² and 8907.83 N/mm², respectively.
 
Wood, which belongs to organic-based building materials, is useful and natural. Despite the many benefits, environmentally exposed wooden building elements are prone to weathering and gradual damage that significantly reduces the structural durability of aged wooden buildings. To effectively assess the structural health of wooden buildings, it is vital to detect, categorize and localize the damaged wooden elements. This study initially identifies and categorizes the damaged wooden elements, adopting deep convolutional neural network (DCNN) models, named Resnet-50, VGG-16, VGG-19, Inception-V3, and Xception. Afterward, the detected damaged parts are localized using Grad-CAM, Grad-CAM++, and Score-CAM visualization techniques. The obtained results are further improved in terms of classification accuracy and computational cost using the K-mean clustering algorithm. Resnet-50 and Xception models performed best amongst the studied DCNN models, resulting in over 90% classification accuracy. Grad-CAM++ and Score-CAM proved to be better for localization of damaged areas. Besides, compressing the image color with K-mean increases the prediction accuracy by 1% while decreasing the computational cost by more than 60 s.
 
A new timber frame structural system consisting of continuous columns, prefabricated hollow box timber decks and beam-to-column moment-resisting connections is investigated. The hollow box timber decks allow long spans with competitive floor height and efficient material consumption. To achieve long spans, semi-rigid connections at the corners of deck elements are used to join the columns to the deck elements. In the present paper, experimental investigations of a semi-rigid moment-resisting connection and a mock-up frame assembly are presented. The semi-rigid connection consists of inclined screwed-in threaded rods and steel coupling parts, connected with friction bolts. Full-scale moment-resisting timber connections were tested under monotonic and cyclic loading to quantify rotational stiffness, energy dissipation and moment resistance. The mock-up frame assembly was tested under cyclic lateral loading and with experimental modal analysis. The lateral stiffness, energy dissipation, rotational stiffness of the connections and the eigen frequencies of the mock-up frame assembly were quantified based on the experimental tests in combination with a Finite Element model, i.e., the model was validated with experimental results from the rotational stiffness tests of the beam-to-column connections. Finally, the structural damping measured with experimental modal analysis was evaluated and compared with FE model using the material damping of timber parts and equivalent viscous damping of the moment-resisting connections.
 
Novel solutions with large-diameter connectors for cross-laminated timber (CLT) assemblies require wood brittle failure to be avoided through capacity-design-based provisions to protect the CLT panels. Current design standards, such as the Canadian Standard for Engineering Design in Wood (CSA-O86), do not cover the block tear-out resistance of CLT panels associated with large-diameter connectors. The primary objective of the research presented herein was to assess the block tear-out and net-section tension resistances of CLT panels loaded in plane and to provide guidance for the required end distances of single large-diameter connectors such as internal-bearing hold-downs. A total of 117 full-scale CLT specimens were tested to determine their in-plane tear-out resistance. 3-ply and 5-ply CLT panels with different loaded end and the edge distances and varying the grain direction of the outer layers were tested under quasi-static monotonic loading. The results demonstrate that brittle block tear-out or net-section tension failure can occur in CLT panels. These failure modes have to be accounted for in design. A simple stress-based strength criterion considering the rolling shear strength of wood delivers conservative and reasonably accurate predictions of the CLT brittle resistance.
 
For better application of laminated bamboo lumber (LBL) in construction industry, the tensile performance of LBL was studied by conducting tension test on LBL specimens with seven different fiber alignment angles, each alignment angle containing 30 specimens. All the specimens only experienced the elastic stage before brittle failure with four failure types. With increasing alignment angle, the tensile strength, tensile modulus, and ultimate tension strain decreased rapidly from 0° to 30°, while they almost remained constant after the angle of 45°. Hankinson’s formula (n = 1.75) can be used to predict the tensile strength of LBL. An empirical equation was proposed to predict the tensile modulus of LBL. The Poisson’s ratio increased and peaked at 15° before declining. Based on the stress–strain coordinate transformation, the relation between shear properties and the alignment angle of LBL was studied; the calculated shear strength decreased with increasing alignment angle, and an empirical equation was proposed, which could be used to obtain the shear strength of LBL for engineering use.
 
Black locust ( Robinia pseudoacacia L . ), beech ( Fagus sylvatica L.), poplar ( Populus x euramericana cv. pannonia ) and spruce ( Picea abies Karst.) wood samples were treated in saturated steam at 100, 110 and 120 °C for 2 days. Steamed and unsteamed (control) specimens were irradiated using a UV emitter mercury lamp in order to determine the chemical changes generated by UV irradiation. The main goal of the research was to find out if steaming can improve the UV resistance of wood. Chemical changes were determined by diffuse reflectance FTIR spectroscopy. Steaming deacetylated the hemicellulose molecules of hardwood species. Steamed spruce specimens showed the same photodegradation properties as the unsteamed ones. Steaming reduced the photodegradation sensitivity of lignin considerably for black locust only. Steamed hardwood specimens presented greater absorption increase at 1705 cm ⁻¹ compared to unsteamed samples, which corresponds to the photodegradation of hemicelluloses.
 
In wood based panel industry, formaldehyde based adhesives are widely employed for bonding, and formaldehyde released from panels negatively affects the environment and human health. Decreasing formaldehyde emission without compromising mechanical properties is an important challenge. In this study, urea glyoxal (UG) and urea melamine glyoxal (UMG) resins were synthesized as non-formaldehyde adhesive, and the effects of melamine content were investigated. Furthermore, an acid ionic liquid named as N-methyl-2-pyrrolidone hydrogen sulfate, was synthesized and used as hardener for particleboard pressing. The solid content, gel time, and viscosity of the synthesized resins were determined. In addition, the structures of these resins were investigated by means of Fourier transform infrared spectroscopy (FTIR) and solid-state cross-polarization/magic angle spinning nuclear magnetic spectroscopy (CP-MAS ¹³C NMR). Thermal properties of resins were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The obtained samples were also characterized morphologically by scanning electron microscope (SEM) and scanning electron microscope energy dispersive X-ray analyses (SEM EDEX). The synthesized resins and hardener were employed for particleboard pressing in laboratory scale. All of the pressed particleboards were evaluated as P1 class according to EN 312 standard. The formaldehyde content was determined with the perforator method (EN 12460-5) resulting in E1 classification. Furthermore, as a whole, the particleboards fulfil E0 and F**** criteria according to well-acknowledged approaches in determining formaldehyde emission.
 
With the aim to utilize the waste biomass of mulberry branches, an injection-moulded wood-based composite was produced by a two-step physical method. Firstly, the thermoplastic wood flour was prepared by kneading wood flour in NaOH/urea solution. Secondly, the injection-moulded wood-based composite was produced by extruding kneaded wood flour with plasticizer. Through the interactions of the hydrogen bonds with NaOH/urea solution and plasticizer during the process of kneading and extrusion, wood flour was efficiently utilized as thermoplastic composite. The whole preparation process was simple and feasible. The mechanical properties of wood-based composites prepared using glycerol triacetate (GT) as plasticizer were much better than that of glycerin. At a GT content of 14 wt%, screw rotating speed of 60 r/min and extrusion temperature of 155 °C, the as-prepared wood-based composite exhibited satisfactory performance in terms of flexural strength (56.14 MPa), tensile strength (26.56 MPa) and elongation at break (3.96%). The thermostability of the wood-based composite decreased after kneading and extrusion.
 
Polyethylene glycol (PEG) was used as the modifying agent of cold-setting melamine–urea–formaldehyde (MUF) resin adhesive in this work. Effects of the amount of PEG on the flexibility of MUF resin, and its bonding properties, as well as water resistance were studied. Then, the flexibility improvement mechanism was also discussed in this paper. Results showed that: (1) the strength and flexibility of MUF resin were greatly improved by PEG. With a PEG addition lower than 0.72% on the total amount of MUF resin, PEG exerted simultaneous reinforcing and flexibility improvement on MUF resin. (2) Both dry and wet shear strength of MUF resin increased with the addition of PEG, reaching the maximum values with 1.80% PEG on the total amount of MUF. (3) The DSC and TG results showed that thermal stability of MUF is degraded with the addition of PEG. (4) SEM results indicated that the addition of PEG was beneficial to the flexibility of MUF resin. The larger the addition amount of PEG, the better the flexibility improvement.
 
Microwave (MW) treatment can be utilized to improve the sound absorption of wood; however, it alters the physical and mechanical properties of the material. Various parameters such as porosity, surface roughness, air cavity depth (ACD), and check after MW treatment were measured in this study. To determine the relationship between wood intrinsic properties and sound absorption capacity, the parameters of MW power density were set to 46.30 kW h/m³, 55.56 kW h/m³, 64.82 kW h/m³, 69.44 kW h/m³, 83.33 kW h/m³, and 97.22 kW h/m³. Many macro-checks and micro-voids occurred, and pit membranes were destroyed after MW treatment as verified by scanning electron microscopy (SEM). The optimal MW-treated parameter for Pinus radiata D. Don was 97.22 kW h/m³. MW treatment increased the sound absorption capacity, decreased the density, and did not affect the surface roughness of the material. The maximum sound absorption coefficient (SAC) increased, and the SAC peak shifted to low frequency range gradually as ACD increased. The average SAC of appropriate ACD of 50 mm was 0.32. Total intrusion volume, total pore area, and permeability improved after MW treatment. The total intrusion volumes of the MW-treated sample and control sample were 2.07 mL/g and 1.81 mL/g, respectively. The pore distribution also widened after MW treatment. ImageJ software was used to determine that percentage of checks to the total sample area is moderately related to sound absorption capacity. MW-modified wood is a favorable potential acoustic absorption material for indoor and outdoor applications.
 
Bamboo winding composite pipe (BWCP) is a commercialized, bio-based product suitable for below-ground infrastructure tunnels and low-pressure water and sewage reticulation. Being manufactured from fast-growing and sustainable but moisture-sensitive bamboos, plus winding resin and fillers, the long-term bond durability of this bio-pipe requires evaluation. Existing standards for assessing the moisture and chemical durability of traditional mortar, plastic, and metal pipes are not suitable for evaluating the bond durability of wound bio-based pipes. Furthermore, standards for testing bond durability of flat resin-bonded structural wood composites are not suitable for continuous cylindrical composites. This paper reports an adapted protocol for rapid assessment of the bond durability of bio-pipes based on existing ASTM standards for bond aging in structural composite lumber and strength testing procedures for pipes. Standard pipe ring compression tests induce adequate interlaminar shear on curved bond lines, and after accelerated aging, although the winding resin was severely moisture degraded, a helically wound bio-pipe like BWCP can retain good residual compression strength. The accelerated aging regime had little effect on the pipe wall tensile strength, assessed using apparent hoop tensile tests, suggesting BWCP may still be able to maintain its internal pressure holding capacity even if water enters the wall substrate provided the bamboo does not decay. The wall structure retains its integrity if it remains sealed from water but once water infiltrates the wall substrate it is difficult to dry out. The proposed protocol is expected to be transferrable to the rapid assessment of moisture-induced durability of other bio-based pipe products.
 
Experimental equipment and procedures
Influence of input parameters on mass loss (a), glossiness difference (b), ∆L* (c) and ∆E* (d)
Interaction influence of laser modification parameters on mass loss
Effects of laser power on discoloration of poplar plywood
Plots of predicted and actual values for mass loss, glossiness difference, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varDelta {L}^{*}$$\end{document}and\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varDelta {E}^{*}$$\end{document}
Laser surface modification is a method that uses a laser beam to irradiate the workpiece surface to change its structure and chemical components, so as to change the physical and chemical properties of the material surface. In this study, the CO2 laser was applied to modify poplar plywood. The mass loss per unit area and paint film properties (color, glossiness and adhesion) were tested and measured to evaluate the processability of laser modification for plywood. The experimental design, data analysis and model creation were accomplished by response surface methodology. Results showed that selected laser processing parameters had a significant influence on mass loss and paint film properties. The absolute values of mass loss, lightness differences and total color differences increased observably with an increase in the laser power, while decreased with an increase in the feed speed and path scanning distance. The glossiness decreased when the laser power and path distance increased but increased with the feed speed increasing. The dark and low gloss surfaces were achieved under high intensity treatment conditions. The laser modification parameters did not have obvious effects on the paint film adhesion, and the grade of paint film adhesion reached to grade 1 according to Chinese standard (GB/T 4893.4–2013). The quadratic models were selected to evaluate the quantitative relationship between laser processing parameters and response parameters, due to the high values of determination coefficient of R². The accuracy of these models was also verified by the validation experiments. The values achieved by the prediction model were in good agreement with the results of validation experiments, which indicated that the created quadratic models could give accurate prediction for the properties variations of poplar plywood during CO2 laser modification.
 
Wood modification at a high temperature (180–300 ℃) and duration (> 5 h) consumes energy and results in a decrease in the quality of the wood. Therefore, wood modifications at mild temperature (120–180 ℃) within a short duration (1–5 h) are proposed to improve dimensional stability, hardness, and flexural modulus with consideration of the wood applications and consumption during manufacturing. The effect of the temperature and duration of mild hydrothermal modification on the properties of beech wood (Zelkova schneideriana Hand-Mzt) was investigated in this study. The physical and mechanical properties of modified wood were measured. Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction were used to analyze the morphology, chemical composition, and crystallinity of modified wood, respectively. The mechanical properties of the wood were deteriorated at high temperatures (180 ℃) and durations (5 h). At a temperature of 140–160 ℃ and duration of 3 h, a moderate increase and decrease were found in dimensional stability and mechanical properties of modified wood, respectively, and the integrated properties of the wood were acceptable. Therefore, mild hydrothermal modifications can be applied into wood modification to obtain improved dimensional stability, good surficial appearance, and almost unchanged mechanical properties that are needed in practical building materials, such as furniture production, and to maximize the functional efficiency and industrial production benefits of wood modification.
 
Top-cited authors
O. Faix
  • University of Hamburg
Dietrich Meier
  • thermophil international
A.Pizzi Pizzi
  • University of Lorraine
Andreas Ringhofer
  • Graz University of Technology
Reinhard Brandner
  • Graz University of Technology