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Fire-retardant (FR) treated wood-based panels, used commonly in furniture and construction, need to meet stringent fire safety regulations. This study presents a novel treatment for imparting fire resistance to wood composites by applying separate solutions of phytic acid and sodium silicate onto wood particles before the hot pressing at 160 °C. A scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) analysis revealed that phytic acid and sodium silicate were uniformly distributed throughout the wood particles, and the formation of silica gel resulted in the aggregation of elemental silicon. Fourier-transform infrared spectroscopy (FTIR) displayed that phytic acid caused the thermal degradation of hemicelluloses, which led to a brownish outer appearance of the FR-treated composites. Fire performance was assessed using both limiting oxygen index (LOI) and a cone calorimeter. These techniques showed a higher LOI value and a significant reduction in heat-release rate (HRR), total heat release (THR), smoke-production rate (SPR), and total smoke production (TSP). In addition, cone calorimeter and thermogravimetric (TGA) analyses consistently showed increased char residue in treated wood composites. Moreover, internal bond strength (IB) and modulus of elasticity (MOE) of the wood composite were not significantly changed compared with those of the untreated composite. Surprisingly, in the FR-treated composite, the 24 h-thickness swelling, and the water uptake were slightly decreased. Consequently, this new treatment has the potential to increase the fire retardancy of wood composites, such as particleboard, without deteriorating the key mechanical properties. Validerad;2023;Nivå 2;2023-05-22 (hanlid);Funder: Slovak Research and Development Agency (APVV-16-0223); VEGA agency (VEGA 1/0678/22); KEGA agency (KEGA 016STU4/2021); Swedish wood industry; OP RDE (CZ.02.1.01/0.0/0.0/16_019/0000803) Biobased fire protection of wood panel for exterior conditions by using phosphorylated lignin from wheat straw Advanced research supporting the forestry and woodprocessing sector’s adaptation to global change and the 4th industrial revolution

The connection between branch and trunk in a tree must be strong enough to transfer all loads acting on the branch, and it is well known that such branch-stem connections are indeed very strong. In this paper, X-ray computer tomography is employed to investigate the local fibre orientation in the close surrounding of a knot in a Norway spruce specimen to better understand the origins of the mechanical strength of the branch-trunk connection. First, a wood specimen containing an entire knot from pith to bark was imaged with a voxel size of 52 µm. Subsequently, smaller specimens were cut from this original specimen and imaged again with increasingly higher resolution over four levels. With the highest resolution level (2.6 µm voxel size), the tracheids with smallest lumen were successfully traced. The results revealed how the direction of the fibre paths that start below the knot curve around it as the paths progress upwards to the region just above the knot, where the paths divide into two: one set of paths integrating with the knot on its top side and the other set continuing up along the trunk. Fibres that integrate with the knot at its top follow paths just before they continue into the knot, with a radius of curvature of only about 1 mm in both vertical and horizontal directions. No abrupt change of fibre pattern between latewood and earlywood is observed; rather, a continuous change of fibre direction across annual layers can be seen. The detailed characterisation of the local fibre structure around the knot provides new data that can explain the remarkable strength of the branch-trunk connection.

Engineered wood products (EWPs) are being increasingly used as construction materials. EWPs are currently being made using synthetic adhesives or metal fasteners, which lead to poor recyclability and reusability. Therefore, this review paper focused on emerging adhesive- and metal-free assembling techniques including wood dowels, rotary-dowel welding, wooden nails, and dovetail joining as alternative ways of making prefabricated EWPs. This will contribute towards green construction and optimising the building process to minimise its negative impact on the environment and its inhabitants, while maximising the positive aspects of the finished structure. The respective advantages and shortcomings will be compared with those of equivalent EWPs. In general, the dowel-laminated timber (DLT) provides sufficient load-bearing capacity and even better ductility than EWPs of equivalent size, but its relatively low stiffness under a bending load limits its application as a structural element. Optimised manufacturing parameters such as dowel species, dowel spacing, dowel diameter, dowel insertion angle, dowel shape, etc. could be studied to improve the stiffness. The improved mechanical properties and tight fitting due to set-recovery of densified wood support its use as sustainable alternatives to hardwood dowels in DLT to overcome problems such as the loosening of connections over time and dimensional instability. The rotary welding technology could also enhance the strength and long-term performance of dowel-type joints, but its poor water resistance needs further investigation. The main obstacles to implementing DLT products in the market are missing technical information and design guidelines based on national codes. Validerad;2023;Nivå 2;2023-02-13 (hanlid);Funder: Republic of Slovenia; Slovenian Research Agency ARRS (J4-3087); CT WOOD, Luleå University of Technology

Walnut (Juglans regia L.) is widely used in wood furnishings, and machinability is a key factor for improving product quality and enterprise benefits. This work focused on the influence of the rake angle, depth of cut, and cutting speed on the cutting force and machined surface roughness during the straight-tooth milling of walnut. On the basis of the experimental findings, a mathematical model was created using a response surface methodology to determine the relationship between the cutting force and the cutting conditions, as well as the relationship between the surface roughness and the cutting conditions. Variance analysis was used to study the significant contributions of the interactions of various factors and two-level interactions to the cutting force and surface roughness. The optimized combination of milling conditions, resulting in lowest cutting force and surface roughness, was determined to be a rake angle of 5°, a depth of cut of 0.6 mm, and a cutting speed of 45 m/s. Validerad;2023;Nivå 2;2023-01-01 (sofila);Funder: National Natural Science Foundation of China (grant no. 31971594); Natural Science Foundation of the Jiangsu Higher Education Institutions of China (grant no. 21KJB220009); Nanjing Forestry University (grant no. nlzzyq202101); Technology Innovation Alliance of Wood/Bamboo Industry (grant no. TIAWBI2021-08); The Qing Lan Project; International Cooperation Joint Laboratory for Production, Education, Research and Application of Ecological Health Care on Home Furnishing

In this paper, a new method of measuring slicing checks for flat-sliced veneers was evaluated. The method is based on image analysis of veneer cross-sections, having highlighted the slicing checks using surface staining. The segmentation of the checks consists of global thresholding followed by some morphological operations. The outputs of the algorithm are check depth ratio and check frequency. The method was tested on flat-sliced oak (Quercus robur L. and Quercus petraea (Matt). Liebl.) veneers of different thicknesses (1.5, 2.5, 3.5 and 4.5 mm). Two distinct wood qualities and two different cutting directions (lengthwise-sliced and plain-sliced veneers) were evaluated. The algorithm performance resulted in an overall accuracy of 85% enabling an accessible method for relatively fast and accurate measurements of slicing check characteristics in lamella cross-sections. Regression analysis indicated a lack of fixed bias but the presence of proportional bias with the presented method. Check measurements indicate that by varying cutting parameters, it is possible to achieve desired check characteristics independent of slicing thickness. The semi-automated slicing check detection method could benefit further research and optimisation of the slicing process parameters and pave the way towards industrial quality control of slicing checks. The intended area of application is veneer-laminated products for interior use with the focus on veneered wood flooring.

The correct characterisation of wood properties is fundamental for the best utilisation of resources. In Europe, grading is defined by strength classes that are determined based on either bending or tension tests. The European standards give equations to estimate characteristic strength in tension from characteristic strength in bending, and vice versa depending on which was tested. These equations are applied to all softwoods. The aim of this paper is to empirically determine the relationship between bending and tension strength properties using two conifer species grown in Ireland and the UK. The results show that the relationships change with species. The standard conversion underestimates, importantly, the performance of spruce for tension loads calculated for the most common bending strength class for Ireland and the UK, C16. The opposite occurs on the reverse conversion. Additionally, the study includes published data from continental Europe, to establish a new conversion that uses timber from a broader range of grades, and that adjusts the tension performance of Irish and UK spruce obtained from bending strength classes, ensuring safe values for design. Open Access funding provided by the IReL Consortium. This research was funded by the Forest Sector Development Division of the Department of Agriculture, Food and the Marine, Ireland. peer-reviewed

Chemical composition is one of the key characteristics that determines wood quality and in turn its suitability for different end products and applications. The inclusion of chemical compositional traits in forest tree improvement requires high‐throughput techniques capable of rapid, non‐destructive and cost‐efficient assessment of large‐scale breeding experiments. We tested whether Fourier‐transform infrared (FTIR) spectroscopy, coupled with partial least squares regression, could serve as an alternative to traditional wet chemistry protocols for the determination of the chemical composition of juvenile wood in Scots pine for tree improvement purposes. FTIR spectra were acquired for 1,245 trees selected in two Scots pine (Pinus sylvestris L.) full‐sib progeny tests located in northern Sweden. Predictive models were developed using 70 reference samples with known chemical composition (the proportion of lignin, carbohydrates [cellulose, hemicelluloses and their structural monosaccharides glucose, mannose, xylose, galactose, and arabinose] and extractives). Individual‐tree narrow‐sense heritabilities and additive genetic correlations were estimated for all chemical traits as well as for growth (height and stem diameter) and wood quality traits (density and stiffness). Genetic control of the chemical traits was mostly moderate. Of the major chemical components, highest heritabilities were observed for hemicelluloses (0.43–0.47), intermediate for lignin and extractives (0.30–0.39), and lowest for cellulose (0.20–0.25). Additive genetic correlations among chemical traits were, except for extractives, positive while those between chemical and wood quality traits were negative. In both groups (chemical and wood quality traits), correlations with extractives exhibited opposite signs. Correlations of chemical traits with growth traits were near zero. The best strategy for genetic improvement of Scots pine juvenile wood for bioenergy production is to decrease and stabilize the content of extractives among trees and then focus on increasing the cellulose:lignin ratio.

The effect of thermal modification (TM) on the chemistry, anatomy and mechanical properties of wood is often investigated using small clear samples. Little is known on the effect of growth-related and processing defects, such as knots and checks, on the bending strength and stiffness of thermally modified timber (TMT). Nine boards of Norway spruce with different combinations of knot types were used to study the combined effects of checks and knots on the bending behaviour of TMT. Digital image correlation (DIC) measurements on board surfaces at sites of knots subjected to bending allowed to study strain distribution and localise cracks prior to and after TM, and to monitor development of fracture (around knots) in TMT to failure. DIC confirmed that checking in knots was increased after TM compared to kiln-dried timber, specifically for intergrown knots and intergrown parts of encased knots. Effects appear local and do not affect board bending stiffness at these sites. Bending failure in TMT initiated mainly at knot interfaces or besides knots and fractures often propagated from checks. Scanning electron microscopy analyses of fracture surfaces confirmed this, and fractures were typically initiated around knots and at knot interfaces due to crack propagation along the grain in the longitudinal–radial plane (TL fracture) under mixed mode I and II loading, such that boards failed in simple tension like unmodified timber. Images of fracture surfaces at the ultrastructural level revealed details of the brittle behaviour of TM wood. This was especially apparent from the smooth appearance of transwall failure under mode I loading across the grain.

This work proposes an experimental approach to study the scratch resistance of green wood under the effect of polyethylene glycol (PEG) impregnation. To this end, small-scale green spruce samples are stabilized against water by using the technique of PEG impregnation to prevent water to seep out of the wood during experimental tests. Scratches are performed in the radial-longitudinal and tangential-longitudinal planes of cubic wood samples by using two different indenter tips under constant and progressive normal loads. Scratch testing has previously been used mainly to characterize the abrasion resistance of coatings. Since PEG simulates the swelling effect of water in wood, this paper shows that the scratch tests on PEG-impregnated green wood can be adopted as a simple technique to understand the scratch resistance in swollen wood and the related mechanisms. The scratch test results, quantified in terms of frictional forces and permanent residual depths, reveal that the scratch resistance of wood samples depends on their PEG concentration and density, as well as on the indenter tip size and material, and on the normal force and direction during scratching. Due to the lack of literature on the scratch tests of wood, the results presented in this paper will serve as a scientific reference for future studies on the scratch resistance of untreated or treated dry wood and other wood-based products.

Rattan cane is an important forest product with economic value. Its anatomical, physical, and biological properties vary with the cane height. This makes it difficult to select the appropriate cane diameter for harvesting. Understanding the material properties of rattan cane with different diameter sizes is important to enhance its utilization and performance for different end uses. Thus, the present study was performed on two rattan species, Calamus zollingeri and Calamus ornatus, at two different cane heights (bottom/mature and top/juvenile). Calamus zollingeri was studied at diameter classes of 20 mm and 30 mm, while Calamus ornatus was analyzed at a diameter class of 15 mm. The anatomical properties, basic density, volumetric swelling, dynamic moisture sorption, and biological durability of rattan samples were studied. The results showed that C. zollingeri with a 20 mm diameter exhibited the highest basic density, hydrophobicity, dimensional stability, and durability against mold and white-rot (Trametes versicolor) fungi. As confirmed by anatomical studies, this could be due to the higher vascular bundle frequency and longer thick-walled fibers that led to a denser structure than in the other categories. In addition, the lignin content might have a positive effect on the mass loss of different rattan canes caused by white-rot decay.

Resource-efficient wood chipping for forest-industrial processes demands large fractions of accept chips and small fractions of small-sized material, such as pin chips and fines. In Kraft pulping, a narrow distribution of wood chip thickness is important for even impregnation and for making high-quality pulp. Using newly developed forest-industrial drum-chipping technology, the investigation covered wood of varying moisture content, frozen versus unfrozen wood, and the use of different wood species. Using conventional techniques for analyzing wood chip dimensions, fast-grown spruce wood with high moisture content gave 4.2 % pin chips and fines, which was less than half of the fractions obtained with spruce wood with lower moisture content. A comparison between frozen and unfrozen pine resulted in slightly thinner and shorter chips for the frozen wood, but in both cases accept yields of up to ∼85 % were achieved. A comparison of different tree species (aspen, birch, pine, and spruce) resulted in larger accept fractions (∼90 %) for the hardwood species, even though the average length of these wood chips was as low as 17 mm. The results provide a first indication of how basic wood log properties affect the yields of accept chips and small-sized material when using modern industrial drum-chipping technology.

A developed bioeconomy needs better storage methods for wood chips and forest industry by-products, since increasing demands for more assortments, more storage will be necessary Today, solutions for coping with storage-related problems, such as dry matter losses and risk of self-ignition, are based on separating assortments into smaller piles and avoiding large-scale long-term storage of chips. A safe and efficient storage solution is needed to enable wood chip production all year round and not be limited to just-in-time production during the cold heating season when there is a large demand. This might result in a more robust system with larger buffer capacities, a less stressful working environment for chipping and transport contractors, and a better yearly machine utilisation. This study evaluated storage outcomes for wood chips and bark when using an improved storage design that created assortment separation using concrete walls and a semipermeable sheet for cover. The new design enabled efficient area utilisation and increased fire safety. The storage outcome was also improved in terms of moisture content, dry matter losses and temperature development compared to conventional open-air piles.

The market share of thermally modified wood (TMW) has increased in Europe during the past few years as an environmentally friendly and durable building product. However, TMW products of today are not permitted for use in structural applications, because the reduction in strength that is caused by thermal treatment cannot be accounted for. The purpose of this paper was to investigate the bending properties of thermally modified timber (TMT) of Norway spruce, and to explore possibilities to predict the bending properties of TMT. A sample of 100 boards from a 2X-log sawing pattern of 100 logs was thermally modified according to the ThermoWood® process, while the mirror 100 boards served as an unmodified control sample. Two non-destructive methods were employed: (1) a novel method based on scanning of fibre directions to obtain the lowest edgewise bending modulus of elasticity (MOE) along a board, and (2) a conventional excitation method to determine the first axial resonance frequency used to calculate the axial dynamic MOE. Finally, the boards were bent to failure according to European standard EN 408. Despite the fact that bending strength was reduced by 42% due to thermal treatment, the type and location of failure in TMT remained related to the presence of knots. Prediction of bending strength based on local fibre direction and axial dynamic MOE, gave coefficients of determination of 0.51 for the thermally modified boards and 0.69 for the control boards, whereas axial dynamic MOE alone gave 0.46 and 0.57, respectively. These results indicate that although Norway spruce TMT has lower bending strength compared to unmodified timber, predictions of the bending strength can be made with good accuracy.

Thermo-hydro-mechanical (THM)-densified timber is rarely used in construction, although its mechanical properties are in many cases excellent. The main reason for its rare use is set-recovery, which reduces the degree of densification over time so that the mechanical properties deteriorate. Our knowledge of the long-term creep of densified timber is insufficient and a full understanding of its long-term behaviour is still lacking. The purpose of this study was to examine the behaviour under long-term loading of Scots pine sapwood densified in an open system at 170–200 °C. The influence of the THM densification process on the creep properties was studied on (1) unmodified specimens, (2) THM-densified specimens, (3) THM-densified specimens that had been further thermally treated, and (4) low-molecular-weight phenol-formaldehyde resin-impregnated and THM-densified specimens. All specimens were loaded at 20 ± 2 °C and 65 ± 5% relative humidity for 14 days under 3-point bending at 35% of the short-term ultimate load, and the bending deformation was registered. The THM densification doubled the density, causing a significant increase in the modulus of rupture but no change in the modulus of elasticity, and reduced the equilibrium moisture content and creep compliance. Post-thermal modification and resin impregnation improved the dimensional stability and further reduced the creep compliance in bending. The results demonstrate that THM densification combined with resin-impregnation or thermal modification reduces the creep of Scots pine timber under a long-term bending load in a constant climate. Validerad;2022;Nivå 2;2022-05-16 (joosat);Funder: Republic of Slovenia, European Regional Development Fund, Slovenian Research Agency ARRS (J4-3087); CT WOOD, Luleå University of Technology

Solid wood can serve multifunctionality for energy savings in buildings. The study reveals the results of biodeterioration and degradation of solid Scots pine wood used to incorporate single or multicomponent fatty acid mixtures as bio-based phase change materials (BPCMs). The sapwood samples were impregnated with capric acid (CA), methyl palmitate (MP), lauryl alcohol (LA) and a mixture of coconut oil fatty acids and linoleic acid (CoFA-LA). The samples were tested against subterranean termites by an Italian species (Reticulitermes lucifugus), the wood boring beetle Hylotrupes bajulus and mold through a discoloration test. Tested against termites, the impregnated samples were significantly less susceptible to the attack than the controls, i.e., the tested BPCMs were resistant to R. lucifugus. The only test with MP terminated at the moment against H. bajulus showed positive results with no larvae surviving. The mold discoloration test revealed that the wood impregnated with CoFA-LA was identically susceptible to mold discoloration when compared to the control, nonimpregnated samples. This pioneer study verifies that solid wood employed for the encapsulation of BPCMs for building purposes can serve identically or somewhat better than similar wooden building elements regarding attacks of the above microorganisms and insects. Such multifunctional building elements will be tested further in a pilot scale building to characterize better the durability aspects of the new materials.

The hardness of the outer regions of solid wood can be improved by surface densification, and this opens up new fields of application for low-density species. So far, surface densification relies on time- and energy-consuming batch processes, and this means that the potential advantages over more expensive hardwood species or non-renewable materials are reduced. Using fossil-based plastics or applying wood densification processes with a high energy consumption has adverse effects on the environment. In a previous study, it was shown that the surface of wood can be densified by a continuous high-speed process, adopting a roller pressing approach. The desired density profiles could be obtained at process speeds of up to 80 m min-1, but an equally simple and fast method to eliminate the moisture-induced set-recovery of the densified wood cells is still required. For this reason, the goal of the present study was to evaluate the effect on the set-recovery and hardness of surface-densified Scots pine after a fast pre-treatment with solutions of sodium silicate, sodium hydroxide, methacrylate resin, and ionic liquids. The Scots pine specimens were pre-treated by applying the chemical treatment and impregnation agents to the wood surface with a paper towel, before the specimens were densified. For each type of treatment, 15 specimens were densified in a hot press. The set-recovery was measured after two wet-dry cycles, and 30 Brinell hardness measurements were carried out on each group of specimens. In general, the effect of the treatments on the set-recovery was rather low. Ionic liquid solutions appear to work as a strong plasticiser and the treatment led to a reduction in set-recovery by 25%. The treatments with sodium silicate, ionic liquids and methacrylate resin led to a greater hardness than in untreated and densified specimens. Further experiments are needed to improve the depth of penetration of the treatment solutions into the wood surface, as this was identified as one of the main causes of the rather weak effects. Validerad;2017;Nivå 2;2017-10-31 (rokbeg)

The strength of structural timber largely depends on the occurrence of knots and on the local material directions in the surroundings of such knots. There is, however, a lack of methods for establishing a full dataset of the local material directions. The present research aims at the development and application of a laboratory method to assess the geometry of growth layers and the orientation of fibres in a high-resolution 3D grid within wood specimens containing knots. The laboratory method was based on optical flatbed scanning and laser scanning, the former resulting in surface images and the latter, utilizing the tracheid effect, resulting in in-plane fibre angles determined in high-resolution grids on scanned surfaces. A rectangular solid wood specimen containing a single knot was cut from a tree in such a way that it could be assumed that a plane of symmetry existed in the specimen. By splitting the specimen through this plane through the centre line of the knot, two new specimens with assumed identical but mirrored properties were achieved. On one of the new specimens, the longitudinal-radial plane was subsequently scanned, and the longitudinal–tangential plane was scanned on the other. Then, by repeatedly planing off material on both specimens followed by scanning of the new surfaces that gradually appeared, 3D coordinate positions along different growth layers and 3D orientation of fibres in a 3D grid were obtained. Comparisons between detected fibre orientation and growth layer geometry were used for the assessment of the accuracy obtained regarding 3D fibre orientation. It was shown that the suggested method is well suited to capture growth layer surfaces and that it provides reliable information on 3D fibre orientation close to knots. Such knowledge is of great importance for understanding the properties of timber including knots. The quantitative data obtained are also useful for calibration of model parameters of general models on fibre orientation close to knots.

Distribution patterns of pectin and hemicellulose epitopes in the phloem of Pinaceae conifers differ between cell types including sieve cells, axial/ray parenchyma cells and stone cells, which is more prominent in seedlings than mature trees. Although there is considerable information on the gross chemistry of conifer bark, little is known on the chemistry of secondary phloem at the individual cell level. This study investigated distribution of pectins and hemicelluloses in the phloem of two conifer species (Norway spruce and Scots pine) at an individual cell wall level using nine monoclonal antibodies specific for pectin and hemicellulose epitopes combined with immunofluorescence and TEM immunogold labeling. Differences in phloem cell wall chemistry between juvenile (seedlings) and mature conifer trees were also examined. The two conifer species showed qualitatively similar distribution patterns of epitopes in sieve- and (axial/ray) parenchyma cells, irrespective of seedlings and mature trees. Sieve- and parenchyma cell walls showed the presence of rhamnogalacturonan-I (RG-I), homogalacturonan (HG) and xyloglucan epitopes, but revealed the absence of heteroxylan epitopes. Heteromannan epitopes were only detected in sieve cell walls, showing a chemical difference between sieve- and parenchyma cells. In contrast to qualitative similarity, there were several quantitative differences of epitope localization in sieve- and parenchyma cells between the two conifer species, indicating variations in the chemical structure and/or the amount of pectins and hemicelluloses between the two conifer species. These differences were more significant in seedlings than mature trees. Immunogold labeling of Norway spruce seedlings further indicated the possibility of chemical variations between cell wall regions within a single sieve cell wall. Phloem stone cells detected in mature Norway spruce showed the presence of heteromannans/heteroxylans and RG-I/HG/xyloglucans in secondary cell wall and middle lamellae, respectively.

Steam explosion pretreatment results in the formation of microcracks in the cell walls of wood. In the present study, steam explosion experiments were performed and structural changes in Norway spruce were identified using scanning electron microscopy. The cellular structure of the softwood spruce was simulated using the finite element method, and the effects of pressure generated during the steam explosion pretreatment on the deformation of the cells were investigated. The simulated model included earlywood, latewood, and ray cells. The effects of bordered and cross-field pits on the stresses in the cell wall were studied as well. Many similarities were observed between the microcracks in the steam-exploded wood and the high-stress regions predicted by the model. The experimental and simulation results showed that the radial cell walls in the earlywood cells experienced major deformation. The presence of the pits created stress localization and facilitated the formation of microcracks in the cell walls.

Creep deformation is a general problem for large wooden structures, and in particular for shipwrecks in museums. In this study, experimental creep data on the wooden cubic samples from the Vasa ship have been analysed to confirm the linearity of the viscoelastic response in the directions where creep was detectable (T and R directions). Isochronous stress–strain curves were derived for relevant uniaxial compressive stresses within reasonable time spans. These curves and the associated creep compliance values justify that it is reasonable to assume a linear viscoelastic behaviour within the tested ranges, given the high degree of general variability. Furthermore, the creep curves were fitted with a one-dimensional standard linear solid model, and although the rheological parameters show a fair amount of scatter, they are candidates as input parameters in a numerical model to predict creep deformations. The isochronous stress–strain relationships were used to define a creep threshold stress below which only negligible creep is expected. These thresholds ranges were 0.3–0.5 MPa in the R direction and 0.05–0.2 MPa in the T direction.

Establishment of biorefineries for processing forest biomass in the Nordic region is extremely costly due to the high investment, running, and procurement costs. Procurement costs could be reduced by allowing all actors to open access to all available terminals in an area (regardless of ownership) and allowing trucks with higher gross weight. These impacts of changes were evaluated for deliveries of logging residue and energy wood chips to a potential biorefinery, from two suppliers in northern Sweden. Open access to all terminals reduced the terminal-procurement costs by 2-6% and the terminal-to-biorefinery transportation costs by 7-9%. When 74 tonnes trucks were used instead of 60 tonnes, the terminal-to-biorefinery transportation costs were reduced by 4 and 3%, in the current situation and with open access to terminals, respectively. However, the largest effect of open access was that the fraction of short-distance transportation to terminals and train transportation from terminals increased significantly. This indicated that open access to terminals and relatively heavy trucks between terminals and the biorefinery are preferable from both environmental and economic perspectives. Furthermore, the estimated cost saving was adequate and should allow the deliverers to pay a reasonable fee for the use of terminal space.

Markkompaktering ökar risken för stress och skador på träden, såsom stormfällningar och rotröta. Idag spelar klimatfrågan en viktig roll, både i samhället och inom skogsbruket. Därför är det intressant att undersöka intresset för att använda alternativa skogsskötselmetoder. Syftet med denna studie var därför att undersöka skogsägares attityder till att använda hästar till drivning. Studien genomfördes som en enkätundersökning bland skogsägare i fem kommuner i Dalarna, med en svarsfrekvens på ca. 36%. Baserat på inkomna svar gick det inte att se några skillnader mellan certifierade och icke certifierade skogsägare. Däremot spelade inställningen till hyggesfritt skogsbruk och storleken på skogsinnehavet in. Slutsatserna var att det fanns ett intresse av att använda häst till drivningen av virket, speciellt vid uttag av vindfällen och fröträd. Skogsägarna bör ta ett större ansvar för sina kunskaper inom skogsskötsel och skogsbruk, medan hästentreprenörer och skogsbolag har ett stort ansvar i att visa på lämpliga alternativ till skogsmaskinerna.

This paper introduces, with the development of user-subroutines in the finite-element software Abaqus FEA®, a new practical analysis tool to simulate transient nonlinear moisture transport in wood. The tool is used to revisit the calibration of moisture simulations prior to the simulation of mechanical behaviour in bending subjected to climate change. Often, this calibration does not receive sufficient attention, since the properties and mechanical behaviour are strongly moisture dependent. The calibration of the moisture transport simulation is made with the average volumetric mass data experimentally obtained on a paired specimen of Norway spruce (Picea abies) with the dimensions $$30\times 15\times 640\, {\mathrm{mm}}^{3}$$ 30 × 15 × 640 mm 3 . The data, from a 90-day period, were measured under a constant temperature of 60 °C and systematic relative humidity cycles between 40 and 80%. A practical method based on analytical expressions was used to incorporate hysteresis and scanning behaviour at the boundary surface. The simulation tool makes the single-Fickian model and Neumann boundary condition readily available and the simulations more flexible to different uses. It also allows for a smoother description of inhomogeneity of material. The analysis from the calibration showed that scanning curves associated with hysteresis cannot be neglected in the simulation. The nonlinearity of the analysis indicated that a coherent set of moisture dependent diffusion and surface emission coefficient is necessary for the correct description of moisture gradients and mass transport.

The chemical composition of wood is one of the key features that determine wood quality. The focus of this study was on identifying differences between juvenile and mature woods in Scots pine (Pinus sylvestrisL.) and developing models for predicting the chemical composition of these two wood types. Chemical traits, determined by traditional wet chemistry techniques, included the proportion of lignin, polysaccharides and extractives. Partial least squares regression of Fourier transform infrared (FTIR) spectra was used for model building. The model performance was primarily evaluated by root mean squared error of predictions (RMSEP). High predictive power was attained for the content of lignin (RMSEP of 0.476 and 0.495 for juvenile and mature woods, respectively) and extractives (0.302 and 0.471), good predictive power for cellulose (0.715 and 0.696) and hemicelluloses in juvenile wood (0.719) and low predictive power for hemicelluloses in mature wood (0.823). A distinct band was observed at 1693 cm−1, and its intensity was strongly associated with the content of extractives (r = 0.968 and 0.861 in juvenile and mature woods, respectively). FTIR has proved suitable for the rapid, non-destructive, cost-efficient assessment of the chemical composition of juvenile and mature woods in Scots pine. The band at 1693 cm−1is to be further investigated to unravel its link with individual extractive components.

Results of the recently approved machine control grading settings for Douglas fir in the Republic of Ireland and the UK have shown that the species can be graded to C18, and higher strength classes, and while there is a relatively high proportion of low strength timber, useful yields of grades up to C35 can be achieved. Large differences were found between subsamples, but it is believed that this is not a geographical difference between Ireland and the UK, but a feature of the representative sampling, and consequence of much more localised variation in timber quality. This work was supported by Forest Sector Development Division of the Department of Agriculture, Food and the Marine, Ireland. peer-reviewed 2020-05-19

Irregular seasonal demand from heat- and combined heat and power plants means that outdoor storage of forest fuels is an inevitable step in the forest fuel supply chain. Storage of fresh comminuted biomass render substantial dry matter and energy losses. Covering can protect wood chips from rewetting, leading to a higher net calorific value and lower dry matter losses, and thus increase the amount of available energy. This study examined the combined effect of covering material on fuel quality and the amount available energy from wood chips stored in a full-scale pile. The combined changes in fuel quality and dry matter loss reduced the amount of accessible energy by 9.8% in the uncovered part, by 5.6% when covered with water proof or light semi-permeable cover materials and by 1.0% when covered with a thicker semi permeable material. Fuel quality of wood chips can be improved by covering the piles during storage but the gain is affected by the type of cover material. Seasonal storage in properly covered chip piles facilitate an increased annual utilisation of chippers and chip trucks which reduces overall biomass supply chain cost.

To understand how the energy requirements of the mechanical pulping process can be reduced, the fundamental mechanisms behind fiber separation in Norway spruce were studied experimentally and analytically. Single tip scratching in heated water was used to reproduce initial defibration mechanisms found industrially. The resulting scratches were then compared with surfaces ground in a real industrial process. Moreover, the mechanical behavior of the wood microstructure was monitored with X-ray computed microtomography as a single hard tip was pressed into it. Subsequent digital image correlation was applied to estimate the strain field in the region around the indenting tip. Regions in the wood with high tensile or shear strains were identified, i.e. where cracking and fiber separation is believed to initiate.

Finger joints in structural timber and glulam lamellae are often used to enable production of long members or to allow for re-connection of parts of a member after removal of weak sections. According to the European Standard EN 15497, certain margins are required between knots and a finger joint in structural timber, which means that a considerable amount of clear wood becomes waste when finger joints are applied. The purpose of this paper was to investigate the possibility of reducing the quantity of waste using different criteria for placement of finger joints. The investigation was based on (1) application of methods of colour scanning and tracheid effect scanning to detect knots and grain disturbance on board surfaces, and (2) interpretation of the requirements of EN 15497 regarding where finger joints may be placed. The standard’s requirement when producing finger joints is that the minimum distance between a knot and a finger joint is three times the knot diameter. The standard allows for the minimum distance between a knot and a finger joint to be shortened to 1.5 times the diameter when the local fibre orientation is measured. Utilizing this in simulated production resulted in reduction of waste from 7.4 to 4.0%, when using finger joints simply to produce timber of long lengths. If finger joints are also used to re-connect parts of members after removal of weak sections, even larger savings can be made. Furthermore, it is concluded that knowledge of fibre orientation obtained from scanning could be used not only to decrease the waste in production but also to increase the quality of finger joints.

The study describes a ground contact test on natural durability of the Siberian larch heartwood timber. The test has been conducted in Finland according to the European norm EN 252 since the year 2006. The material is timber imported from natural larch stands in Ust-Ilimsk, Russia, and cultivated larch stand in Punkaharju, Finland. The Finnish stand is growing outside the natural range of distribution of Siberian larch. Untreated Scots pine heartwood and impregnated Scots pine sapwood were used as reference materials. The results after 11 years showed that there was remarkable variation in the durability between the larch heartwood samples. Nevertheless, the most durable timber lots on average were the Siberian larch heartwoods harvested from the Russian native stands and the Finnish cultivated stand. It is predicted that it will take another 10 years or more until the failure of the most durable larch stakes.

Impulse excitation is commonly used to assess wood stiffness in both scientific and industrial settings. Modes of vibration are excited by a mechanical impulse and their resonant frequencies measured to calculate elastic moduli. It is also possible to assess damping, which is an important property for wood used in musical instruments. This paper covers finer details of the signal analysis necessary when making very accurate measurements. Provided code for Open Source statistical software R is illustrated with data from an experiment tracking small changes in Douglas-fir clear wood during thermal treatment. A frequency domain interpolation method is introduced that enhances the potential precision of the technique to a very high degree, with computational efficiency, even when using inexpensive audio equipment. With multiple measurements, resonant frequencies can be assessed to a precision of 0.1 Hz and better, allowing for tracking of very small changes due to wood treatments or moisture content.

Willow species (Salix) are important as short‐rotation biomass crops for bioenergy, which creates a demand for faster genetic improvement and breeding through deployment of molecular marker‐assisted selection (MAS). To find markers associated with important adaptive traits, such as growth and phenology, for use in MAS, we genetically dissected the trait variation of a Salix viminalis (L.) population of 323 accessions. The accessions were sampled throughout northern Europe and were established at two field sites in Pustnäs, Sweden, and at Woburn, UK, offering the opportunity to assess the impact of genotype‐by‐environment interactions (G × E) on trait–marker associations. Field measurements were recorded for growth and phenology traits. The accessions were genotyped using 1536 SNP markers developed from phenology candidate genes and from genes previously observed to be differentially expressed in contrasting environments. Association mapping between 1233 of these SNPs and the measured traits was performed taking into account population structure and threshold selection bias. At a false discovery rate (FDR) of 0.2, 29 SNPs were associated with bud burst, leaf senescence, number of shoots or shoot diameter. The percentage of accession variation (Radj2) explained by these associations ranged from 0.3% to 4.4%, suggesting that the studied traits are controlled by many loci of limited individual impact. Despite this, a SNP in the EARLY FLOWERING 3 gene was repeatedly associated (FDR

Effective utilization of structural timber requires grading and indicating properties (IPs) that are able to predict strength with high accuracy, and machines that are able to measure the underlying board properties at a speed that corresponds to the production speed of sawmills. The aim of this research is to assess the performance of a new machine strength grading method/procedure which was recently approved for the European market and to compare the performance of it with the performance of other available techniques. The novel method is based on laser scanning utilizing the tracheid effect, in combination with data from dynamic excitation and weighing. Applied indicating properties are defined in detail and results presented include assessment of the repeatability, coefficients of determination between IPs and grade determining properties, and examples of the yield achieved in different strength classes and combinations of strength classes. The investigated sample comprised more than 900 pieces of timber of Norway spruce (Picea abies) from Sweden, Norway and Finland. For this sample the coefficient of determination between the IP to bending strength and the measured bending strength was as high as R2 = 0.69, while the coefficient of determination between dynamic modulus of elasticity (MOE) and measured bending strength was R2 = 0.53. The yield in high strength classes, C35 and above, become about twice as high using the new method/procedure compared to machines using dynamic MOE as IP. A comparison of the performance with what have been presented for machines that are based on X-ray in combination with dynamic excitation indicates that the new method/procedure will surpass such machines as well.

This work describes distortion (bow, crook, twist, cup) and the formation of visible cracks in green and seasoned timber of Scots pine and Norway spruce. Distortion and crack formation have been evaluated according to the original location in the cross section of the log. The purpose is to describe differences in distortion and crack formation between sawn timber taken from star sawing and from traditional sawing patterns. Bow and crook develop in the green timber immediately after sawing as a result of growth stress release. Drying and conditioning in general lead to a marginal increase in bow, but crook may show a large percentage increase depending on the location of the wood in the cross section. Twist and cup do not occur directly after sawing, but arise during seasoning of the wood. In sawn wood, the juvenile wood has a major influence on the twist. This means that timber sawn close to the pith shows a greater twist than timber sawn away from the pith. This is a consequence of the fibre orientation in this timber. Cupping increases with decreasing radius of curvature of the annual rings in the cross section of the timber. Cracks occur in timber before seasoning. The pattern of crack formation is the same in both pine and spruce; timber sawn close to the pith or with pith enclosed exhibits a considerably larger number of visible cracks than timber sawn away from the pith. Cracks occur mainly on surfaces orientated to the pith, a fact that becomes clearer when timber is observed close to the pith. Seasoned star-sawn timber with a rectangular cross section has bow and crook of the same extent as or less than that of timber sawn according to traditional sawing patterns. Seasoned star-sawn timber with a triangular cross section has high bow, but the crook is low. Star-sawn timber does not show any cup and has a good shape stability according to the geometrical shape in the cross section. It also has a very small twist and shows very few visible cracks after seasoning.

A new manufacturing system, the PrimWood Method, has been proposed to improve the utilization of wood. A basic concept within this method is the sawing pattern called star-sawing, which produces timber with both rectangular and triangular cross sections. This method facilitates an efficient production of radially sawn timber with vertical annual rings, without juvenile wood. The sawn timber produced in the PrimWood Method is used to produce high quality, knot-free solid wood panels with vertical annual rings. In this process, part of the timber is finger-jointed to form knot-free lengths which are glued together into a block. This block can then be divided according to thickness into thinner panels with vertical annual rings. The PrimWood Method has been tested in an industrial plant. The manufacturing system was designed for a sawing capacity of about 30,000 m3 logs, which corresponds to 16,800 m3 of star-sawn timber per shift per annum. The production of solid wood panel was then designed to give a volume of 5,800 m3 per annum.

Sistematično smo analizirali objave Oddelka za lesarstvo Biotehniške fakultete Univerze v Ljubljani. Za identifikacijo vseh dokumentov objavljenih do vključno novembra 2009 smo preizkusili in izbrali najustreznejše ukaze v ukaznem iskanju slovenske vzajemne bibliografsko-kataložne baze podatkov in sistema COBIB/COBISS. Za nadaljnjo analizo objav smo zgradili lastno eksperimentalno bazo podatkov, v kateri so zbrani vsi pridobljeni podatki. Bibliometrična analiza je zajela objave vseh avtorjev oddelka glede na leto izida in jezik besedila ter objave raziskovalcev še zaposlenih na oddelku v letu 2009 in članke razkropljene po revijah. Identificirali smo 5078 različnih objav oddelka, vpisanih v bazo z vsemi potrebnimi šiframi. Število objav se je z leti poviševalo, največji porast je zaznati po letu 1990. Med tipi dokumentov v skupini Monografije in druga zaključena dela številčno prednjači diplomsko delo s šifro 2.11, v skupini Članki in drugi sestavni deli je največ izvirnih znanstvenih člankov s šifro 1.01, medtem, ko izvedenih del (dogodkov) s šifro oddelka v bazi podatkov ni zaslediti. Največ objav (80 %) je napisanih v slovenskem jeziku, med tujimi jeziki pa prevladuje angleški (17 % vseh objav). Najrazličnejši članki so razkropljeni po 146 slovenskih in tujih revijah. Pri 24 izbranih raziskovalcih so števila objav na posameznega v razponu med 773 in 6. Samo s standardnimi osnovnimi iskalnimi ukazi baze podatkov COBIB ni mogoče dobiti popolne bibliografije Oddelka za lesarstvo. Pojavljajo se pomanjkljivi vnosi ter napake, in sicer 69 vnosov brez šifre tipologije in 225 brez šifre ustanove. Izdelali smo tudi seznam dokumentov, na osnovi katerega bo knjižnica lahko po potrebi dopolnila bibliografijo oddelka z manjkajočimi podatki. Thesis systematically analyses publications of the Department of Wood Science and Technology of the Biotechnical Faculty of the University of Ljubljana. For the purposes of identification of all publications until November 2009 inclusive, we examined and selected the most suitable commands in the command search of the Slovenian catalogue and COBIB/COBISS system. For a further analysis of publications, we set up our own experimental database, including all of the acquired data. The bibliometric analysis covered publications of all Department authors according to publication year and language, as well as publications of researchers still employed at the Department in 2009, and articles scattered among various journals. We identified 5078 different Department publications recorded in the database with all the required codes. The number of publications was gradually increasing it was the highest after 1990. Among document types in the Monographs group and other completed works the highest number belongs to graduation theses with code 2.11, among the Articles group and other component parts the highest number belongs to original scientific articles with code 1.01, whereas performed works (events) with the department number cannot be detected in the database. The majority of publications (80 %) is written in Slovene, while English prevails among foreign languages (17 % of all publications). A wide variety of articles is scattered among 146 Slovene and foreign journals. Among 24 selected researchers the numbers of publications per individual range from 773 and 6. It is not possible to obtain a complete bibliography of the Department by means of standard basic search commands of COBIB database. Data deficiency and errors appear 69 records have no typology code and 225 records no institution code. We have also created a list of documents providing a basis for the library to complete the department bibliography with the missing data.