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Mildly delignified softwood holocellulose fibers featuring native tracheid fiber cell wall structure and high hemicellulose content are prominent building blocks for wood derived fiber-based materials. However, preserving the natural alignment of long softwood fiber is challenging since top-down structure-retaining delignified softwood is unstable as extensive removal of lignin from intercellular space induces cracking and disintegration of wood structure. Here we report the use of chemical crosslinking pretreatment to improve the intercellular bonding between softwood fibers, therefore preserving the integrity of the naturally aligned softwood fibers after delignification. The crosslinked softwood veneer was delignified with peracetic acid and further densified into transparent and high-density film by thermal compression. The obtained transparent film of naturally aligned softwood holocellulose fibers showed high optical transmittance of 71 %, high haze of 85 %, strong optical anisotropy, as well as high tensile strength of 449 ± 58 MPa and high Young's modulus of 49.9 ± 5.6 GPa. This study provides a facile approach to preserve the natural alignment of softwood fibers for the fabrication of high performance holocellulose fibers-based materials., QC 20240925

Poor condition of roofs in terms of decay of shingles and loss of tar-based surface treatments has been revealed in a number of churches at various geographical locations in mid-Sweden. The condition of tars obtained from shingles of selected churches in mid-Sweden were analysed and obtained data were compared with geographical locations of the churches. According to gas chromatography-mass spectroscopy result, dehydroabietic acid was the dominant compound found in the exposed tars from the churches except in church of Malung where similar amounts of retene was found. Oxidised resin acids were found in exposed tars from the churches but not in commercially available pit burned tar. Tar from church shingles had higher char residues than the pit burned tar which was totally consumed when heated under nitrogen gas up to 750°C using thermogravimetric analysis. Scanning electron microscopy with energy dispersive X-ray spectrometer analysis revealed higher amounts of silicates in some exposed tars; however, these compounds constituted only a minor portion of the organic matter in these specimens. Based on the data obtained in the study other factors rather than simply geographical location of churches seemed to be of importance to explain differences of the investigated properties of the church tars., Validerad;2024;Nivå 2;2024-06-27 (hanlid);Full text license: CC BY, Biobasedfire protection of wood panel for exterior conditions by using phosphorylated lignin from wheat straw

Locust bean gum, derived from the carob tree, was evaluated as a biobased adhesive in particleboard manufacturing, investigating the effect of adhesive amount, mat moisture content, and process parameters such as temperature and time. Single-layer particleboards prepared with locust bean gum showed that effective hydration of the polymer chains is necessary to achieve satisfactory interactions with wood and thus yield a sufficient particleboard strength. A mat moisture content below 30 % resulted in weak particleboards, which easily broke immediately after pressing. With increasing mat moisture content, while keeping the adhesive amount constant, the internal bond strength was increased. Moreover, with constant mat moisture contents (40 %), the internal bond strength increased when the adhesive amount was increased, even though not proportionally. With an increase from 9 % to 18 % adhesive, the internal bond strength was increased by more than 100 %. However, with a further increase in adhesive content from 18 % to 36 %, the increase in internal bond strength was statistically insignificant. Even with high mat moisture contents (35–45 %), larger lab-scale particleboards had internal bond strength that fulfilled standard requirements for P2 boards, commonly used for furniture in dry conditions (SS EN 312), when the pressing time was long enough (75 s/mm) to allow for water and vapors to be removed before releasing the pressure. Using biopolymers as adhesives, without extensive chemical modification and hazardous crosslinkers, could lead to a more benign and sustainable particleboard production. Since the chemistry and setting/curing processes of biopolymer-based adhesives differ from those of the fossil-based adhesives used today, increased understanding of how production parameters affect the properties of the particleboards prepared with biopolymers may pave the way for their better utilization in this field., QC 20231213

Birch has long suffered from a lack of active forest management, leading many researchers to use material without a detailed management history. Data collected from three birch (Betula pendula Roth, B. pubescens Ehrh.) sites in southern Sweden were analyzed using regression analysis to detect any trends or differences in wood properties that could be explained by stand history, tree age and stem form. All sites were genetics trials established in the same way. Estimates of acoustic velocity (AV) from non-destructive testing (NDT) and predicted AV had a higher correlation if data was pooled across sites and other stem form factors were considered. A subsample of stems had radial profiles of X-ray wood density and ring width by year created, and wood density was related to ring number from the pith and ring width. It seemed likely that wood density was negatively related to ring width for both birch species. Linear models had slight improvements if site and species were included, but only the youngest site with trees at age 15 had both birch species. This paper indicated that NDT values need to be considered separately, and any predictive models will likely be improved if they are specific to the site and birch species measured.

En enkel byggnad utan laster på sig, är en stabil byggnad. Om byggnaden saknarhorisontalstabilisering och en horisontell last läggs på byggnaden blir den omedelbartinstabil och man behöver därför införa horisontalstabilisering. I Sverige är denvanligaste orsaken till horisontella laster vinden, men i andra delar av världen finnsäven jordbävningar som också verkar horisontellt på byggnaden. I det här arbetet hardiagonalstagning, skivverkan och momentstyva förband undersökts förkontorsbyggnader med pelar-balkstomme i trä. Syftet var att undersöka hur mycketsystemen ändrar stabiliteten på de undersökta stabiliseringsmetoderna. För att undersöka detta har en referensbyggnad använts, som är byggd helt i trä ochsom använt sig utav diagonalstagning. Byggnaden modellerades i RFEM där de trevalda stabiliseringssystemen studerades. En testmodell, som var enklare modeller förbyggnaden där resultat togs fram och beräknades, skapades för att lättare undersökade olika systemen. Även några parameterstudier gjordes för att skapa fler resultat ochatt undersöka fler intressanta varianter. Från resultaten beräknades lastfaktorer i x-, y-,och z-led, som beskriver stabilitet på byggnaden, fjäderkonstant, som beskriverstyvheten på bygganden, och mängden använt material. Lastfaktorn i samtliga tre lastriktningar var störst hos den parameterstudie somanvända sig utav stabiliserande innerväggar som tillägg. För testmodellerna med detre stabiliserande grundsystemen presterade skivverkan bäst i två av tre fall avlastfaktor. Diagonalstagning påvisade den högsta fjäderkonstanten av grundsystemenoch parameterstudien med innerväggar hade den högsta fjäderkonstanten. Genom att använda skivverkan istället för de andra två stabiliseringssystemen, kan enenkel modell göra så att en stabilare byggnad uppnås. Mer material kommer dock gååt men det kan accepteras då man får en stabilare byggnad.

The optimization of sawing processes in the wood industry is critical for maximizing efficiency and profitability. The introduction of computerized tomography scanners provides sawmill operators with three-dimensional internal models of logs, which can be used to assess value and yield more accurately. We present a methodology for solving the sawing optimization problem employing a flexible sawing scheme that allows greater flexibility in cutting logs into products while considering product quality classes influenced by wane defects. The methodology has two phases: preprocessing and optimization. In the preprocessing phase, two alternative algorithms are given that generate and evaluate the potential sawing positions of products by considering the 3D surface of the log, product size requirements, and product quality classes. In the optimization phase, a maximum set-packing problem is solved for the preprocessed data using mixed-integer programming (MIP), aiming to obtain a feasible cut pattern that maximizes value yield. This is implemented in a system named FlexSaw, which takes advantage of parallel computation during the preprocessing phase and utilizes a MIP solver during the optimization phase. The proposed sawing methods are evaluated on the Swedish Pine Stem Bank. Additionally, FlexSaw is compared with an existing tool that utilizes cant sawing. Results demonstrate the superiority of flexible sawing. While the practical feasibility of implementing a flexible way of sawing logs is constrained by the limitations of current sawmill machinery, the potential increase in yield promotes the exploration of alternative machinery in the wood industry.

Denna rapport utgör en samlad dokumentation av underlags data, med avseende på de olika industriprocesser som ingår i visualiseringsverktyget BioMapp. De skogsindustriella processerna som beskrivs i rapportens bilagor baseras på en allmänt accepterad inventeringsmetodik för att beskriva skogsbaserade produkters miljöpåverkan och andra hållbarhetsindikatorer i ett livscykelperspektiv. Det systemanalytiska verktyg som används i projektet är livscykelanalys (LCA) på så sätt som det tillämpas i miljövarudeklarationer för produkter (EPD).De inventeringsdata som redovisas har en ambition att vara representativa för den typ av processer och miljöbelastning som är relevanta för svenska förhållande. Det har dock inte varit möjligt inom ramen för projektet att göra kompletta branschsammanställningar., This report constitutes the overall documentation of the data available in the visualization tool BioMapp with regards to various industrial processes. The forest industrial processes described in the report are based on a generally accepted inventory methodology to describe the environmental impact of forest-based products and other sustainability indicators in a life cycle perspective. The system analysis tool used in the project is life cycle analysis (LCA) in the way it is applied in environmental product declarations (EPD).These inventory data are representative in the type of processes and environmental impact that are relevant to Swedish conditions. However, it has not been possible within the framework of the project to make complete industry summaries.

The differential swelling seen between softwood opposite wood (OW) and its neighbouring compression wood (CW) developed in branches prompts several engineering issues such as dimensional instability and cracking. For a more efficient use of resources, the inevitable CW and OW should not be discarded or used as fuel, but incorporated into engineered wood products. Swelling is a hygroelastic phenomenon, where both the swelling and elastic properties of CW and OW are needed in order to make proper structural predictions. In this paper, swelling coefficients and moisture dependent elastic moduli for both CW and OW in the three principal material directions are provided along with measurements of moisture content, density, and microfibril angle. The small deformations necessitate the use of precise X-ray micro-computed tomography for measurements. The results indicate that CW and OW from Norway spruce branches differ in swelling, especially in longitudinal direction at low moisture content. It is noted that CW is a wood type with less pronounced anisotropic behaviour than both OW and normal wood from the stem, with the elastic moduli less sensitive to moisture changes in both longitudinal and transverse directions.

The strength of cross laminated timber (CLT) depends on the stiffness and strength of the lamellas and on thestrength of the finger joints. A model for how stiffness and strength vary along and between lamellas is used incombination with a finite element model of CLT and Monte Carlo simulations to calculate out-of-plane bendingstrength of homogeneous and inhomogeneous CLT. Calculated and experimentally obtained results of characteristicbending strengths, coefficient of variation of bending strength and the proportion of finger joint failures,agree very well for both types of CLT. The characteristic out-of-plane bending strength and the mean bendingstiffness were 23% and 16% higher, respectively, for inhomogeneous CLT with outer layer lamellas graded in thestrength class C35, compared to homogeneous CLT with all lamellas graded in the class C24. Simulation resultsgive basis for simple equations by which bending strength of CLT can be determined as function of the layup, thestrength class of outer layer lamellas and characteristic strength of the finger joints. Furthermore, system effectsare investigated. For inhomogeneous CLT, with outer layer lamellas of high strength class, the system effects turnout to be quite different from those of ordinary, homogeneous CLT.

Humins are heterogeneous and polydisperse furanic macromolecules derived from sugar biorefinery. Improving wood properties by humination has become of interest recently. This study examined the photodegradation stability of European pine sapwood microveneers modified with humins at different concentrations of citric acid (CA) and succinic acid (SA) as reaction catalysts, e.g., 1.5 %, 3 %, and 4.5 % wt.%. The photostability of huminated wood was assessed after 48 h, 96 h, and 144 h of exposure to the accelerated weathering test by means of mass loss and finite-span tensile strength. The results were compared with unmodified and also unweathered samples. The FT-IR spectroscopy showed apparent changes in the chemical structure of wood by humination modifications. The weight percentage gains of the samples increased with increasing the concentration of the catalyst. While no differences were observed between the samples after two weeks of the water leaching. The strength losses of weathered microveneers were, however, mostly reduced by humin-based formulas containing catalysts, where the microveneers modified with 1.5 % and 3 % CA showed respectively 32 % and 41 % lower strength loss values than the unmodified samples after 144 h of weathering. Overall, the results showed a high potential for humins to protect wood against photodegradation.

Tannins are polyphenolic compounds extracted from various tree species and used in variousmapplications such as adhesives, composites, pharmaceuticals, medicines, and food and beverage production (Mubarak et al. 2023). However, tannins, especially condensed tannins, have limited reactivity with wood. Consequently, to effectively modify wood, cross-linkers and other reactive chemicals or additives must be used. In this work, we have introduced a bio-based cross-linker in a 20% tannin (Quebracho) aqueous solution. Five levels of cross-linker (0, 2, 10, 20 and 40% of total tannin solid) were used to modify Scotspine (Pinus sylvestris L.) sapwood with dimensions of 25 × 25 × 10 mm3 (radial × tangential × longitudinal). Full-cell impregnation was applied with a 60 min vacuum and pressure for 60 min. Samples were kept at room condition for 24 h, stepwise dried to avoid drying defects and cured at 140 °C for 10 h. Modified wood samples are shown in Figure 1. Weight percentage gain (WPG) and bulking coefficient (BC) after water leaching for 5 days were measured according to Donath et al. (2004).

Beech wood, renowned for its diverse applications spanning construction, flooring, furniture, veneer, and plywood, holds a paramount position among industrial wood species. Nevertheless, the myriad of beech species worldwide, coupled with the dynamic impact of climate change, have produced structural variations within beech trees. Extensive research has scrutinized the physical and mechanical attributes of beech wood species across the globe. Findings reveal distinguishable mechanical strength, yet increased density leads to notable rates of shrinkage and swelling, somewhat constraining its utility in select domains. Identifying research gaps can create new efforts aimed at exploiting the potential of these wood resources. This paper outperforms a mere exploration of beech wood properties over the past two decades; it delves into the ramifications of climatic fluctuations, temperature shifts, wind dynamics, and soil composition. Given the lack of a comprehensive compendium documenting the full range of physical, mechanical, and microscopic attributes of the Fagus genus, this paper aims to compile information that integrates this multifaceted information.

Vanligtvis används betong för grundläggningar idag, men det undersöks om korslimmat trä (KLT) kanersätta detta. KLT är ett förnyelsebart material och har miljömässiga fördelar jämfört med betong. Enplatta i KL-trä är vekare än betong och den här studien ska utreda hur de påverkas av olika storlekarpå fjäderkonstanter. Bäddmoduls-teorin är en metod som går ut på att modellera marken sommekaniska fjädrar. Studien genomfördes med en platta på mark med två olika material med olikaegenskaper där dessa jämfördes. En specifik byggnad som RISE står för användes för inspiration ochenbart kontakttryck och deformationer kommer undersökas.En litteraturstudie har genomförts för att öka förståelsen för bäddmoduls-teorin och materialen.Beräkningar av plattstyvheter utfördes och programvara för finita elementmetoden (FEM) användesför att simulera grunden. Resultaten från detta kommer sedan jämföras.Resultatet visade stora skillnader mellan materialen. KLT-plattan gav ett kontakttryck med tvåbrytpunkter, där värdena gav lokala max- och minipunkter, för det valda intervallet avfjäderkonstanter och deformationen minskade med en jämn takt. Betongplattan visade istället enjämn ökning av kontakttrycket och en jämn minskning för deformationen i samma intervall.KLT-plattan ger ett högt kontakttryck vid lägre värden på fjäderkonstanten vilket kan vara ett problemvid grundläggningar då det inte får överstiga markens dimensionerande hållfasthet. Betong-plattanvisade lägre kontakttryck vid samma intervall på fjäderkonstanten vilket beror på dess högre styvhet.Deformationen var något högre för KLT-plattan vid lägre bäddmoduler.Bäddmoduls-teorin är enbart en approximativ metod och en djupare undersökning behövs viddimensionering av grunder. Resultatet visar att det är möjligt att bygga grunder i KL-trä men man börundvika för stora koncentrerade laster så kontakttrycket inte blir för högt., Concrete is commonly used for foundations today, but research is being conducted to see if crosslaminatedtimber (CLT) can replace it. CLT is a renewable material and has environmental advantagescompared to concrete. A CLT slab is more flexible than concrete, and this study aims to investigatehow it is affected by different sizes of spring constants. The bedding modulus theory is a method thatmodels the ground as mechanical springs. The study was conducted with a slab on the ground usingtwo different materials with different properties, and these were compared. A specific buildingassociated with RISE served as inspiration, and only contact pressure and deformations wereexamined.A literature review was conducted to increase the understanding of the subgrade modulus theory andthe materials. Calculations of slab stiffness were performed, and finite element method (FEM)software was used to simulate the foundation. The results from this will then be compared.The results showed significant differences between the materials. The CLT slab exhibited contactpressure with two breakpoints, where the values resulted in local maxima and minima, within theselected range of the spring constant, and the deformation decreased at a steady rate. The concreteslab, on the other hand, showed a steady increase in contact pressure and a consistent decrease indeformation within the same range.The CLT slab generates high contact pressure at lower values of the spring constant, which can beproblematic for foundations as it must not exceed the soil’s design strength. The concrete slabshowed lower contact pressure within the same range of spring constant, which is due to its higherstiffness. The deformation was slightly higher for the CLT slab at lower bedding moduli.The bedding modulus theory is only an approximate method, and a more in-depth investigation isneeded when designing foundations. The results show that it is possible to construct foundationsusing CLT, but concentrated loads should be

Citric acid can be used as a bio-based binding agent in composites made from lignocellulosic material due to its crosslinking ability with hydroxyl groups via ester formation. Even though plenty of research has investigated diverse manufacturing conditions, with a focus on citric acid content and pressing temperature, an apparent knowledge gap persists regarding their effect on the properties of particleboards made from softwood sawdust. Furthermore, the optimal temperature for particleboards crafted from mostly non-wood lignocellulosic materials was found to be 180–200°C which is lower than that observed for softwood material in a prior study. This study aimed to systematically examine the effects of citric acid content and pressing temperature on particleboards derived from softwood sawdust. Results highlighted a positive correlation of both citric acid content and pressing temperature with mechanical and hygroscopic properties of the particleboards, the best results being achieved at 20 wt% citric acid and 220°C, exhibiting a thickness swelling of 9%, internal bonding strength of 0.77 MPa and a modulus of rupture of 4.3 MPa. This study served as a foundational framework for future investigations into the addition of other chemicals, offering a comprehensive understanding of their interactions with citric acid in particleboard manufacturing., Validerad;2024;Nivå 2;2024-08-15 (sofila);Full text license: CC BY-NC-ND 4.0

To improve the resistance of wood to biological decay the Maillard reaction between introduced amines and wood cell-wall polymers can be utilised. However, initial studies in wood modification showed almost complete leaching of bicine and tricine from treated wood and the loss of beneficial effects. The objective of this study was to assess whether possible reactions of bicine or tricine with wood could be further enhanced and reaction products stabilised through the addition of glucose and/or citric acid. Thus, Scots pine sapwood specimens were impregnated with tricine or bicine, with or without glucose and citric acid, and then heated to a temperature of 160°C. The dimensional stability, degree of chemical leaching and mechanical properties were assessed. Overall, it was concluded that neither the presence of glucose nor citric acid did appear to enhance the reactivity of tricine or bicine. Anti-swelling efficiency (ASE) of 50% was observed for combined treatments of bicine/tricine and citric acid but the leaching resistance originated mainly from citric acid and glucose, with no indication for the retention of bicine or tricine. The presence of citric acid led to a strongly reduced modulus of rupture., Validerad;2024;Nivå 2;2024-08-15 (sofila);Full text license: CC BY-NC-ND License

Increasing environmental awareness and the carbon-storing capability of wood have amplified its relevance as a building material. The demand for high-quality wood species necessitates exploring alternative, underutilized wood sources due to limited forest areas and premium wood volume. Consequently, the veneer-based industry is considering lower-value hardwood species like grey alder (Alnus Incania), black alder (Alnus glutinosa), and aspen (Populus tremula) as substitutes for high-quality birch (Betula pendula). Initially less appealing due to their lower density and mechanical properties, these species show promise through densification, which enhances their density, strength, and hardness. This study aims to enhance plywood screw withdrawal capacity and surface hardness by densifying low-density wood species and using them in plywood face-veneer layers, or in all layers. The relationship between the wood density, surface hardness, and screw withdrawal capacity of plywood made of low-value species like aspen and black alder is examined. Experimental work with a pilot-scale veneer and plywood production line demonstrates improved surface hardness (65% and 93% for aspen and black alder, respectively) and screw withdrawal capacity (16% and 35% for aspen and black alder, respectively) in densified face veneer plywood. This research highlights the potential of densified low-value wood species to meet construction requirements, expanding their practical applications., Validerad;2024;Nivå 2;2024-07-24 (signyg);Funder: Estonian Research Council (PRG2213); Environmental Investment Center (RE.4.08.22-0012);Fulltext license: CC BY

Recently developed technology in sawmills such as advanced log scanning and traceability concepts enable new ways of grading logs and boards. When it comes to strength grading, this is often done on sawn boards using automatic scanning systems. However, if board scanners were to be augmented with data from log scanners by using traceability, more information on the wood propertiesis available. In this study, the main objective was to compare the strength prediction capability of board scanning alone, to board scanning augmented with X-ray and 3D data from log scanning, for Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.). In that case, data from three different scanning systems was combined, two for logs and one for boards. A further objective was to investigate whether pre-sorting logs for strength grading can be done using either 3D log data alone, or 3D log data augmented with X-ray data. The results show an improved strength prediction when adding log data to board data, and that 3D log data alone is not enough to pre-sort logs for strength, while adding X-ray log data makes it possible. Strength prediction on Scots pine performed somewhat better than prediction on Norway spruce., Validerad;2024;Nivå 2;2024-02-05 (signyg);Funder: ForestValue Research Programme;Full text license: The general policies of BioResources are as follows: Authors retain rights to their material, which, upon acceptance by the journal, is uploaded and made public on the Internet. The journal retains no copyright. Users have the right to read, download, copy, distribute, print, search, or link to the full texts of articles in the journal, and users can use, reuse, and build upon the material in the journal for non-commercial purposes as long as attribution is given when appropriate or necessary.

This review systematically examines the multitude of factors influencing bonding strength in bamboo-based composite materials, given the rising prominence of bamboo as a green building material. With bamboo's inherent variability in mechanical properties and structure, engineered bamboo products have emerged to address challenges related to connections and joints. Such advancements have necessitated a detailed exploration of adhesive systems, a significant cost determinant in bamboo production. The adhesive bonding mechanism in bamboo, akin to wood, involves intricate processes including adhesive spreading, penetration, and solidification, influenced by the unique chemical composition of bamboo. The interfacial bond quality plays a pivotal role in determining the durability and performance of the final products, with numerous factors such as bamboo species, layered structure, adhesive type, and treatment types impacting the mechanical properties. Particular attention is given to the disparities in physical and mechanical properties between the bamboo culm's core and shell layers, attributing complexities to the gluing process. Examining shear failure strength reveals its criticality in mechanical investigations, with variations in bonding strength affecting the outcome. The review underscores the need for consistent quality control and adept manipulation of these influential factors for the successful manufacture of bamboo-based products. A comprehensive discussion ensues on the variables controlling the bonding properties of the developed bamboo products, aiming to evaluate and highlight the optimal parameters and procedures essential for enhancing the quality and reliability of bamboo-based composite materials for sustainable construction applications., Validerad;2024;Nivå 2;2024-07-03 (hanlid);Funder: Prince Sattam bin Abdulaziz University (PSAU/2024/R/1445);Full text license: CC BY

The rise in energy consumption and the increase in the use of bio-based materials in the building sector, has led to the need to investigate the possibilities to use wood as a porous support material for phase change materials (PCMs), and thereby creating a thermal regulative wood-based product. This study investigated the influence of Kraft lignin-glyoxal prepolymer on the thermal-energy storage properties of wood modified with paraffin-type of PCM. The implementation of the modified wood involves preparing PCM emulsions, synthesising lignin-glyoxal prepolymer, and modifying wood with the PCM-Kraft lignin-glyoxal emulsion through vacuum-pressure impregnation. The infrared imaging suggested the ability of PCM-modified wood to delay the temperature changes, even with the introduction of Kraft lignin-glyoxal prepolymer. In conclusion, it is feasible to introduce thermal-energy storage property into wood with the addition of Kraft lignin-glyoxal prepolymer. Further studies will focus on the long-term thermal storage performance properties when this PCM system is subjected to repeated heating/cooling cycles., Validerad;2024;Nivå 2;2024-07-02 (hanlid);Funder: Swedish Wood Industry;Full text license: CC BY-NC-ND

The purpose of this research study was to investigate the properties of polyurethane coatings based on ligninnano-particles. For this purpose, the prepared coatings were applied to pine wood surfaces and weathered artificially.Subsequently, color and gloss of the coatings were measured before and after the weathering test. Fieldemission scanning electron microscopy (FE-SEM) micrographs prepared from the coatings showed that the averagesize of nano-particles in the polyurethane substrate was approximately 500 nm. Nuclear magnetic resonance(13C-NMR) spectroscopy showed that strong urethane bonds were formed in the nano-lignin-based polyurethane.Differential calorimetric analysis (DSC) test revealed that the glass-transition temperature (Tg) of lignin nanoparticlesmodified with diethylenetriamine (DETA) was 112.8°C and Tg of lignin nano-particles modified withethylenediamine (EDA) was 102.5°C, which is lower than the Tg of un-modified lignin (114.6°C) and lignin modifiedwith DETA (126.8°C) and lignin modified with EDA (131.3°C). The coatings modified with lignin nano-particleshad a greater change in gloss. The lignin nano-particles in the modified coating are trapping hydroxylradicals which reduces photoactivity and yellowing of the polyurethane by about 3 times compared to unmodifiedpolyurethane coatings. After weathering test, the nano-lignin-based coating had a rougher surface with a lowercontact angle (0.78°) compared to the unmodified polyurethane coating (0.85°)., Godkänd;2024;Nivå 0;2024-04-08 (marisr);Full text license: CC BY;Funder: Tarbiat Modares University of Tehran

Purpose: Wood comprises different cell types, such as fibers, tracheids and vessels, defining its properties. Studying cells’ shape, size, and arrangement in microscopy images is crucial for understanding wood characteristics. Typically, this involves macerating (soaking) samples in a solution to separate cells, then spreading them on slides for imaging with a microscope that covers a wide area, capturing thousands of cells. However, these cells often cluster and overlap in images, making the segmentation difficult and time-consuming using standard image-processing methods. Results: In this work, we developed an automatic deep learning segmentation approach that utilizes the one-stage YOLOv8 model for fast and accurate segmentation and characterization of macerated fiber and vessel form aspen trees in microscopy images. The model can analyze 32,640 x 25,920 pixels images and demonstrate effective cell detection and segmentation, achieving a mAP0.5-0.95 of 78 %. To assess the model’s robustness, we examined fibers from a genetically modified tree line known for longer fibers. The outcomes were comparable to previous manual measurements. Additionally, we created a user-friendly web application for image analysis and provided the code for use on Google Colab. Conclusion: By leveraging YOLOv8’s advances, this work provides a deep learning solution to enable efficient quantification and analysis of wood cells suitable for practical applications., QC 20240903

Metallic wood combines the unique structural benefits of wood and the properties of metals and is thus promising for applications ranging from heat transfer to electromagnetic shielding to energy conversion. However, achieving metallic wood with full use of wood structural benefits such as anisotropy and multiscale porosity is challenging. A key reason is the limited mass transfer in bulk wood where fibers have closed ends. In this work, programmed removal of cell-wall components (delignification and hemicellulose extraction) was introduced to improve the accessibility of cell walls and mass diffusion in wood. Subsequent low-temperature electroless Cu plating resulted in a uniform continuous Cu coating on the cell wall, and, furthermore, Cu nanoparticles (NPs) insertion into the wood cell wall. A novel Cu NPs-embedded multilayered cell-wall structure was created. The unique structure benefits compressible metal-composite foam, appealing for stress sensors, where the multilayered cell wall contributes to the compressibility and stability. The technology developed for wood metallization here could be transferred to other functionalizations aimed at reaching fine structure in bulk wood., QC 20240626

\par Inom trävetenskapen är noggrann segmentering av icke-cellulära element i mikroskopibilder avgörande för applikationer som bedömning av träkvalitet och förståelse av tillväxtmönster, men utmanande på grund av den komplexa morfologin hos träkomponenter. Denna avhandling utforskar utvecklingen av en djupinlärningsbaserad, semisuperviserad modell för segmentering av icke-cellulära element i mikroskopibilder av gran, en viktig källa för byggmaterial i Europa, vilket adresserar utmaningen med den arbetsintensiva och expertisberoende manuella annoteringen. Segmenteringsmodellen använder effektivt avancerade djupinlärningsarkitekturer, inklusive konvolutionella neurala nätverk och Vision Transformer, för att fånga de inre mönstren inbäddade i trästrukturen. Genom att använda både märkta och omärkta data föreslår denna avhandling en Pixel-level Guided Mean-Teacher (PG-MT) ramverk som en förbättring av Mean-Teacher, vilket möjliggör pixel-nivå guidad korrigering för att förbättra segmenteringsnoggrannhet och modellens robusthet med begränsade märkta dataset. Experimentella utvärderingar visar att det föreslagna PG-MT-ramverket förbättrade Dice-poängen för märgstrålesegmentering med 0,95% och IoU-poängen med 1,14% jämfört med den Uncertainty-Aware Mean-Teacher (UA-MT). Dessutom betonar integrationen med laboratorieinstrument modellens effektivitet i att exakt uppskatta tvärsnittsväggtjocklek, vilket visar en stark korrelation med röntgenmätningar. Detta bekräftar modellens praktiska användbarhet i laboratoriemiljöer, vilket förbättrar analysen av träegenskaper. Studien står dock inför begränsningar, inklusive en datamängd av begränsat omfång vilket påverkar generaliserbarheten, och potentiella bias i manuella annoteringar som kan påverka noggrannheten. Trots dessa utmaningar tillhandahåller detta arbete en robust ramverk för trä mikroskopifältet, vilket avsevärt minskar annoteringsbördan och banar väg för mer automatiserad och exakt analys av träegenskaper., Inom trävetenskapen är noggrann segmentering av icke-cellulära element i mikroskopibilder avgörande för applikationer som bedömning av träkvalitet och förståelse av tillväxtmönster, men utmanande på grund av den komplexa morfologin hos träkomponenter. Denna avhandling utforskar utvecklingen av en djupinlärningsbaserad, semisuperviserad modell för segmentering av icke-cellulära element i mikroskopibilder av gran, en viktig källa för byggmaterial i Europa, vilket adresserar utmaningen med den arbetsintensiva och expertisberoende manuella annoteringen. Segmenteringsmodellen använder effektivt avancerade djupinlärningsarkitekturer, inklusive konvolutionella neurala nätverk och Vision Transformer, för att fånga de inre mönstren inbäddade i trästrukturen. Genom att använda både märkta och omärkta data föreslår denna avhandling en Pixel-level Guided Mean-Teacher (PG-MT) ramverk som en förbättring av Mean-Teacher, vilket möjliggör pixel-nivå guidad korrigering för att förbättra segmenteringsnoggrannhet och modellens robusthet med begränsade märkta dataset. Experimentella utvärderingar visar att det föreslagna PG-MT-ramverket förbättrade Dice-poängen för märgstrålesegmentering med 0,95% och IoU-poängen med 1,14% jämfört med den Uncertainty-Aware Mean-Teacher (UA-MT). Dessutom betonar integrationen med laboratorieinstrument modellens effektivitet i att exakt uppskatta tvärsnittsväggtjocklek, vilket visar en stark korrelation med röntgenmätningar. Detta bekräftar modellens praktiska användbarhet i laboratoriemiljöer, vilket förbättrar analysen av träegenskaper. Studien står dock inför begränsningar, inklusive en datamängd av begränsat omfång vilket påverkar generaliserbarheten, och potentiella bias i manuella annoteringar som kan påverka noggrannheten. Trots dessa utmaningar tillhandahåller detta arbete en robust ramverk för trä mikroskopifältet, vilket avsevärt minskar annoteringsbördan och banar väg för mer automatiserad och exakt analys av träegenskaper.

With the evolution of GPU performance, the interest of using AI for all kinds of purposes has risen. Companies today put a great amount of resources to find new ways of using AI to increase the value of their products or automating processes. An area in the wood industry where AI is widely used and studied is in defect detection. In this thesis, the combination of using AI and hyperspectral images is studied and evaluated in the case of segmenting defects in hardwood with a U- Net network structure. The performance is compared to another known method usually used when dealing with high-dimensional data: PLS-DA. This thesis also compares the use of RGB image data in combination with AI, to further analyze the usefulness that the hyperspectral data provide. The results showed signs of improvement when using hyperspectral images com- pared to RGB images when detecting blue stain and red heartwood defects. De- tection of the defects rot and knots did however show no sign of improvements. Due to the annotations being more accurate in the RGB data, the results from the hyperspectral data-fed networks would suggest that blue stain and red heartwood could be of interest regarding further investigation. Computational performance is shown to vary across the different reduction meth- ods, and the results from this thesis provides some insight that might aid in the reasoning regarding how to choose an appropriate reduction method.

Porous cellular foams, combining lightweight, high strength, and compressibility, hold great promise in a wide range of advanced applications. Here, the native structure of pine wood was modified by in-situ lignin sulfonation and unidirectional freezing, resulting in an alveolate structure inside the wood cell wall with arrays of sub-100 nm channels. The obtained wood foam exhibited highly enhanced permeability while retaining the native cellular arrangement and high lignin and hemicellulose content. Such engineered cellular foam contributed to superior mechanical performance with compressive strength of 9 MPa and Young's modulus of 344 MPa in the longitudinal direction. The high porosity allowed homogeneous infiltration of conductive polymer PEDOT: PSS inside the wood cell wall. The resulting composite exhibited high conductivity, sponge-like compressibility and the ability to modulate electrical resistance in a reversible manner in the radial direction. This rationally designed conductive wood demonstrated potential in durable and ultrasensitive pressure-responsive devices and strain sensors., Funding Agencies|Knut and Alice Wallenberg Foundation (KAW) through the Wallenberg Wood Science Center [WWSC 2.0: KAW 2018.0452]

A reliable determination of the embedment strength and foundation modulus of timber elements is critical for the design and safety assessment of joints in timber structures. However, the existence of various test configurations for characterising the embedding properties of large diameter steel fasteners in timber elements poses challenges in directly comparing and utilising available test data. This paper aims to provide an insight into the influence of embedment property test methods, comparing experimental results from different test setups within the guidelines of the EN 383 and ASTM D 5764-97a standards for European softwood species, Scots pine wood (Pinus sylvestris) and Norway spruce (Picea abies). In addition to the test guidelines, the thickness of the specimen and the application of the load was evaluated within the protocols. A comprehensive statistical analysis was performed to identify statistically significant differences between the groups evaluated. The results of the analysis revealed disagreement between the standards in the evaluation of the strength of the embedding, highlighting the potential bias inserted by the experimental setup and protocol. Furthermore, it was proven that the thickness of the specimens influences both the embedding strength and the foundation modulus of the wood species tested. Finally, no distinctions were observed between tensile and compressive loading within the guidelines of the EN 383 standard., Bibliografiskt granskad

Reducing the time for drying sawn timber to a certain moisture level without deteriorating its quality is increasingly important for an economic and energy-efficient industrial timber-drying process and to support the transition to a sustainable society. It is, however, crucial to ensure that the quality of the timber, i.e. the degree of distortion, cracking, discolouration, and moisture variation within and between the pieces in a drying batch, is not compromised. Drying-simulation software tend to be too conservative in drying-rate recommendations, which has been observed in practise particularly for large cross-section timber of Norway spruce. This study investigated the drying rate and checking occurrence of centre-yielded Norway spruce planks when dried with more aggressive schedules than normally used in practise, i.e. using higher dry-bulb temperatures and/or lower relative humidities than recommended in the conventional optimisation programmes used in the sawmill industry in Sweden. The objective was to investigate the possibility to considerably reduce the total drying time without compromising the quality of the dried timber. The quality of the planks was indirectly assessed by estimating their moisture-content distributions, calculating the moisture gradients and monitoring checking. This was achieved with 4D (3D + time) X-ray computed tomography and a recently developed image processing algorithm based on elastic image registration. The key findings in this study suggest that Norway spruce timber can be dried with significantly higher temperatures and lower relative humidities than suggested by simulations, leading to reduced total drying time without inducing checking. This methodology can help to improve the design of drying schedules to reduce drying time and energy consumption while maintaining timber quality at a level accepted by the customers., Validerad;2024;Nivå 2;2024-03-25 (hanlid);Full text license: CC BY 4.0This article has previously appeared as a manuscript in a thesis.

This study investigates the influence of different machining processes on the tensile shear strength of glued lumber, focusing on optimizing the tool geometry of face milling. The data obtained were analyzed using statistical methods. The roughness of the surface produced by the machining process and the damage to the microstructure under the cutting edge are identified as important factors influencing the quality of the bond. The results show that the optimized process (low roughness and microstructure damage) leads to more effective gluing., Validerad;2024;Nivå 2;2024-03-22 (hanlid);Funder: German Federal Ministry of Education and Research and the Free State of Saxony (SN0390002);Full text license: CC BY 4.0

The modification of Scots pine sapwood (Pinus sylvestris L.) with the heterocyclic compounds imidazole and succinimide was investigated. Pressure-impregnation with aqueous solutions containing imidazole, imidazole + citric acid, succinimide, succinimide + citric acid, and citric acid + sorbitol (CIOL®) with solid contents of 5%, 10%, and 15% was followed by oven-curing at 220 °C for 1 h. During the treatment steps, the changes in mass, bending properties, and anti-swelling efficiency (ASE) were examined. The results indicate that solid concentrations within the range of 5% to 10% were optimal. The results seem to show that there are two differing mechanisms in the modification of imidazole and succinimide, respectively. Mass loss due to heat treatment was highest in the imidazole-treated specimens, whereas it remained low and concentration-independent in the succinimide-treated specimens. After three cycles, the ASE reached 31% for the imidazole-treated specimens and improved to 38% with the addition of citric acid. For succinimide, the ASE increased from 17% to 41%. The bending properties generally showed improvement, except for succinimide + citric acid and CIOL®, which displayed a reduced modulus of rupture. Chemical analyses are warranted to fully understand the reaction mechanisms of these treatments. The positive effects of imidazole treatment are suggested to stem from a thermal reaction between the chemical and the wood, indicated by substantial mass loss during leaching and specimen darkening. Succinimide and citric acid might exhibit polymerization with each other and with wood components, which is akin to the CIOL® process. Further research should delve into the reaction mechanisms and the impact of imidazole and succinimide on biological durability., Validerad;2023;Nivå 2;2023-10-18 (joosat);CC BY 4.0 License

Efficient thermal management of modern electronics requires the use of thin films with highly anisotropic thermal conductivity. Such films enable the effective dissipation of excess heat along one direction while simultaneously providing thermal insulation along the perpendicular direction. This study employs non-equilibrium molecular dynamics to investigate the thermal conductivity of bilayer graphene (BLG) sheets, examining both in-plane and cross-plane thermal conductivities. The in-plane thermal conductivity of 10 nm × 10 nm BLG with zigzag and armchair edges at room temperature is found to be around 204 W/m·K and 124 W/m·K, respectively. The in-plane thermal conductivity of BLG increases with sheet length. BLG with zigzag edges consistently exhibits 30–40% higher thermal conductivity than BLG with armchair edges. In addition, increasing temperature from 300 K to 600 K decreases the in-plane thermal conductivity of a 10 nm × 10 nm zigzag BLG by about 34%. Similarly, the application of a 12.5% tensile strain induces a 51% reduction in its thermal conductivity compared to the strain-free values. Armchair configurations exhibit similar responses to variations in temperature and strain, but with less sensitivity. Furthermore, the cross-plane thermal conductivity of BLG at 300 K is estimated to be 0.05 W/m·K, significantly lower than the in-plane results. The cross-plane thermal conductance of BLG decreases with increasing temperatures, specifically, at 600 K, its value is almost 16% of that observed at 300 K., Validerad;2023;Nivå 2;2023-10-31 (joosat);CC BY 4.0 License

Thermo-mechanical densification of sawn timber results in improved mechanical properties, but densified wood remains a fairly expensive niche product, partially because of high-cost batch processing. Densification in a continuous process could address this problem and was shown to be possible in previous research. The outcomes were limited to proofs-of-concept, partially due to insufficient cooling capabilities of the used densification equipment, resulting in high spring-back. Therefore, a novel continuous process using a belt press to densify full-sized sawn timber has been conceived. The press ensures almost constant contact between the wood and the heating and cooling elements. The study aimed to analyse how the processing temperature, speed and compression ratio affected the density profile, spring-back, set-recovery, Brinell hardness, and bending properties. Results showed a density increase concentrated close beneath the surface in contact with the heating element and approx. 20% spring-back. Belt speeds above 2 m min−1 caused higher spring-back due to the reduced contact time between the wood and the heating element. Brinell hardness increased by up to 250% at a compression ratio of 27% while bending properties were unaffected. Belt temperature and speed were shown to be critical factors to consider for the future optimisation of the belt-press process., Validerad;2023;Nivå 2;2023-11-08 (joosat);Full text license: CC BY-NC-ND 4.0

Determining moisture content (MC) distribution during the drying of porous materials such as wood is crucial for developing drying schedules and assessing their suitability to achieve optimised processes. This study aimed to determine the causes of the unique drying behaviour and the well-known unusual longer drying time of western hemlock compared to other similar softwoods. In situ X-ray computed tomography (CT) was used to study the evolution of MC in timber during the drying process. The drying behaviour of western hemlock (Tsuga heterophylla (Raf.) Sarg.) was compared with Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) from green to oven-dried condition with industry-proposed drying schedules used for steering a custom-made experimental kiln combined with a CT scanner. CT scanning was performed at 30 min intervals during the complete drying period of 30 h, and the CT images were processed to calculate the MC evolution within the specimen. Western hemlock showed a considerably slower capillary-phase drying and did not go into the transition and diffusion phases when a schedule adapted to pine and spruce drying was applied for its drying. CT images and MC gradient calculations showed a lower drying rate and severe non-uniformity in MC distribution, which could be due to the effect of higher green MC and the presence of wet pockets. Furthermore, the evaporation front at the first 5 h of drying receded faster into the hemlock specimen, and as drying proceeded, it slowed down compared to other specimens., Godkänd;2023;Nivå 0;2023-10-12 (joosat);Konferensartikel i tidskrift;Part of special Issue: International Conference Wood Science and Engineering in the Third Millennium - ICWSE 2023CC BY 4.0 License

Particleboards with different combinations of the adhesive material imidazole, citric acid, and sorbitol were produced. Softwood sawdust from a Swedish sawmill was mixed with an aqueous solution of the chemicals and then dried to 0% moisture content prior to pressing. The boards were pressed to a target density of 700 kg m−3 at either 200 °C or 220 °C for 10 min. The hygroscopic and mechanical properties of the boards were clearly better at 220 °C than 200 °C for all used chemical combinations. A combination of imidazole (14.4 wt%) and citric acid (11.3 wt%) led to the best results, where the thickness swelling after 24 h of water immersion was 6.3% and the internal bonding strength was 0.57 MPa. The modulus of rupture and modulus of elasticity were 3.3 MPa and 1.1 GPa, respectively. Cyclic accelerated weathering showed exceptional stability with a thickness change after boiling and drying of only 2.1% compared to the initial dry thickness. This study indicates that the presence of imidazole leads to greatly improved hygroscopic properties and good internal bonding strength when used in particleboards., Validerad;2023;Nivå 2;2023-11-20 (hanlid);Full text license: CC BY, CT WOOD, Multifunktionella byggskivor av sågspån

The structural integrity of cell walls in wood is maintained by matrix polysaccharides through chemical interactions among themselves and with both cellulose and lignin. During wood formation, matrix polysaccharides are deposited in the cell walls and subsequently modified by spontaneous and/or enzyme-mediated processes. These processes are highly regulated during successive stages of wood formation, including cell division, expansion and secondary (or further tertiary) cell wall layer deposition. They are also adjusted in response to various endogenous and environmental signals by developing xylem cells, with corresponding modifications of cell wall properties. In addition, there is substantial variation among taxonomic groups of plants in the chemical composition of matrix wood polysaccharides. This chapter discusses these dynamic changes in matrix polymers during wood development and adaptive responses to environmental stresses, the matrix variation among cell types and between hardwoods and softwoods and the functional significance of this dynamic variation for wood cell wall properties., Part of ISBN 9781000996326, 9781032013213QC 20231229

The mechanical properties of sliced lamellae are critical for structural and decorative engineered wood products. This study evaluates the impact of slicing thickness on the tensile mechanical properties of plain oak (Quercus robur L. and Quercus petraea L.) sliced lamellae, perpendicular to the grain direction. The mechanical performance parameters in terms of the modulus of rupture (MOR), strain at break, and modulus of elasticity (MOE), were analysed using a one-way analysis of variance (ANOVA) and contrast analysis. Our findings indicate that slicing thickness substantially affects the mechanical properties of the modulus of rupture and strain at break, whilst the modulus of elasticity was somewhat independent of the slicing thickness. The mean MOR value increased from 0.8 to 1.43 N mm(-2) for an increase in the sliced lamellae thickness from 1.5 to 4.5 mm. The strain at break increased, on average, from 1.37 to 2.64% for an increase in the sliced lamellae thickness from 1.5 to 4.5 mm. The MOE was approximately 100-120 N mm(-2), indicating a substantially reduced stiffness compared to other sliced lamellae species and solid oak reported values. The slicing check depth ratio diminished from approximately 69% to 50% for an increase in the sliced lamellae thickness from 1.5 mm to 4.5 mm. These findings indicate a negative correlation between the slicing check depth ratio and the tensile performance perpendicular to the grain, suggesting the importance of obtaining an optimal slicing quality. This study employs digital image correlation (DIC) analysis to gain insights into the fracture mechanisms of the tested sliced lamellae and provides an alternative method for strain and stress measuring. The DIC analysis highlighted the role of slicing checks in the stress concentration and ultimate failure areas. This research provides insights into the fracture behaviour of sliced lamellae that are perpendicular to the grain, which is critical for the performance of both stru

Surface-checking is a significant quality issue of veneer and sliced lamellae-based wood products. This study explores how surface-checking in sliced lamellae-based engineered wood Flooring (EWF) is influenced by two key structure parameters: core type and top-layer thickness. The core types assessed were a standard solid wood lamellae with a veneer back-end layer (S), a standard solid wood lamellae core with veneer back-end layers on the two sides (DS), and a single-layer oriented strand board (OS) core. The EWF element's top-layer lamellae were plain sliced at nominal dimensions of 1.5, 2.5, 3.5, and 4.5 mm from freshly sawn slabs of European oak (Quercus spp.). The surface-checking of EWF specimens was quantified based on a digital image correlation (DIC) method, which outputs a surface-checking index. The surface-checking results were evaluated using a Tweedie compound Poisson data distribution to fit a general linear model. The model evaluated the impact of individual factors, sliced lamellae thickness and core type, and their interaction. The checking index confidence intervals were estimated using a bootstrapping technique. Findings reveal a significant interaction between studied factors and provide insight into optimizing top-layer thickness and core construction to diminish surface-checking. A low sliced lamella thickness on standard solid wood lamellae core resulted in low surface-checking, deemed relevant for further research.

Understanding the structure of hardwoods can permit better valorization of lignin by enabling the optimization of green, high-yield extraction protocols that preserve the structure of wood biopolymers. To that end, a mild protocol was applied for the extraction of lignin from ball-milled birch. This made it possible to understand the differences in the extractability of lignin in each extraction step. The fractions were extensively characterized using 1D and 2D nuclear magnetic resonance spectroscopy, size exclusion chromatography, and pyrolysis-gas chromatography-mass spectrometry. This comprehensive characterization highlighted that lignin populations extracted by warm water, alkali, and ionic liquid/ethanol diverged in structural features including subunit composition, interunit linkage content, and the abundance of oxidized moieties. Moreover, ether- and ester-type lignin-carbohydrate complexes were identified in the different extracts. Irrespective of whether natively present in the wood or artificially formed during extraction, these complexes play an important role in the extractability of lignin from ball-milled hardwood. Our results contribute to the further improvement of lignin extraction strategies, for both understanding lignin as present in the lignocellulosic matrix and for dedicated lignin valorization efforts., QC 20231130

The present work focuses on analysis of deformation and strength behaviour of slotted-in steel plateconnections in glued laminated timber (GLT). In Eurocode 5 (EC5), the design of metal dowel-type timber joints is basedon the yield theory presented by Johansen [1]. It consists of analytical expressions to calculate the lateral load-carryingcapacity of single fastener joints that exhibit different (plastic) failure modes. When designing optimised multiple fastenerconnections that are exposed to dominating moment action, the calculation of fastener forces and their directions duringprogressive plasticization of the dowel group is difficult to perform manually. Therefore, a simple numerical model tosimulate progressive elasto-plastic force development for every individual dowel is needed. This study presents new andsimple models to analyse the bending deformations of glulam beams jointed with mechanical slotted-in steel plateconnections. The proposed models were experimentally verified using results obtained from a joint project with theMaterial Testing Institute (MPA) at University of Stuttgart.

Funder: CT WOOD;ISBN for host publication: 978-961-6379-82-3

Optical scanning and X-ray computed tomography (CT) scanning of sawn timber provide a large numberof data points, on which data-driven numerical models can be based for simulations. These models require informationabout the deviations of the fibre orientations in the vicinity of knots. Optical scanning can be used to measure the in-planefibre orientation on wood surfaces. In CT scans of sawn timber, the fibre orientation around knots can be estimated usinga new fibre reconstruction algorithm based on the density gradient. The goal of this paper is to compare and synchroniseoptical and CT scanning data of sawn timber and then use the combined data set to evaluate fibre orientations derivedfrom both representations. The material comprised sawn timber of Norway spruce, in which alignment holes were drilled.The timber was scanned in an industrial CT scanner and subsequently in an industrial optical scanner where scanning wasrepeated after successive planing of the sawn timber surface. The results show that a projective mapping in combinationwith a spline interpolation are required for synchronisation, and that the in-plane fibre orientations calculated from thedensity gradients are qualitatively similar to the orientations derived from the optical data.

The properties of sheathing-to-framing joints considerably affect the load carrying capacity of a light-frame timber shear wall. A fastener with isotropic or kinematic hardening properties is modelled for the sheathing-to-framing joints with a zero-length element, with coupled properties in two perpendicular (orthogonal translational)directions to avoid the overestimation achieved with an uncoupled alternative. A single fastener experiment is performedto determine the elastic and plastic properties. For both fastener level and wall level modelling, monotonic as well ascyclic loading scheme is analysed. A concept of modelling the elasto-plastic coupled behaviour with hardening of theconnector model for the fasteners is suggested. A damage response of the fastener is also studied to estimate the failurein load capacity of the connector model and decrease in the wall capacity after the maximum loading.

Petrochemical-based phenol–formaldehyde (PF) adhesives are widely used in plywood production. To substitute phenol in the synthesis of PF adhesives, lignin can be added due to its structural similarity to phenol. Moreover, micro-fibrillated cellulose (MFC) can further enhance the bond performance, mechanical properties, and toughness of adhesive systems. Thus, the aim of this study was to evaluate the adhesion performance of lignin–PF (LPF) adhesives reinforced with MFC. In LPF formulations, three levels of MFC (0, 15, and 30 wt% based on the total solid content of adhesives) were added to the homogenous adhesive mixture. Three-layer plywood panels from birch (Betula pendula Roth.) veneers were assembled after hot pressing at 130 °C under two pressing durations, e.g., 60 and 75 s/mm. Tensile shear strength was measured at dry (20 °C and 65% RH) and wet conditions (water soaked at room temperature for 24 h). The results indicated that the addition of lignin reduced the strength of LPF adhesives in both dry and wet conditions compared to the control PF adhesive. However, MFC reinforcement enhanced the shear strength properties of the plywood. Furthermore, a longer pressing time of 75 s/mm slightly increased the shear strength.

In the present work, it was demonstrated that mass transfer and mass transfer coefficients related to the wood drying process can be satisfactorily quantified using thermography. The method was based on continuous measurements of the wood's surface temperature, which were converted to a vapor pressure at the wood surface. The results showed that the values of the experimentally obtained transfer coefficients were in the same order of magnitude as values obtained with classical empirical correlations that apply in boundary layer theory. The measurements also showed that an average value of the mass transfer coefficient obtained during drying satisfactorily describes the complete process. The measurement set-up makes it possible to determine a surface potential accurately and continuously, which is useful in the assessment of wood drying processes.

This study investigated whether improved downy birch could perform as well as improved silver birch, and whether there was sufficient genetic variation and control for non-destructive testing (NDT) values to include them as selection traits in breeding programs. NDT tools were applied to a 15-year-old downy birch family trial intermixed with improved silver birch. Average diameters, fissured bark height, and grain angle were higher for silver than downy birch. The genetic analysis for downy birch provided estimates of narrow-sense heritability (h2) for acoustic velocity and Pilodyn penetration depth that were above 0.3 but had low genetic variation. Grain angle had relatively high genetic variability (18%) and an h2 of 0.20. A subsample of 49 trees had 4 mm cores x-rayed for wood density estimates, and 34 stems had 12 mm cores macerated for cell measurements. t-tests revealed that average wood density and cell measurements were not significantly different between species. For silver and downy birch, fiber length and vessel length increased between inner and outer measurement positions, and fiber length was reasonably correlated with acoustic velocity. Silver birch tended to have denser and stiffer wood, while downy birch had less rough bark and straighter grain, and these results are in agreement with existing knowledge. The h2 values were similar to those observed in other birch species and indicate there is potential to breed for improved wood density and grain angle in downy birch.