Tropical Wood Research Articles

Ultrasound to estimate the physical-mechanical properties of tropical wood species grown in an agroforestry system

Abstract The great diversity of tropical wood species makes it difficult to obtain information about their technological properties. The present work employed ultrasound to estimate the physical and mechanical properties of four wood species: African mahogany (Khaya senegalensis), ‘freijó’ (Cordia goeldiana), ‘paricá’ (Schizolobium amazonicum), and teak (Tectona grandis). Nineteen-year-old adult trees were selected and harvested from an agroforestry system (AFS) located in the Brazilian Amazon. From the harvested trees, 1.5 m logs were sawn and test specimens were obtained for physical-mechanical assays. The ultrasound propagation speed (V 0) and the dynamic modulus of elasticity (E d ) were obtained from applying ultrasound longitudinally in wood samples. Values of V 0 decreased from the lightest wood (paricá) to the heaviest (African mahogany), and E d presented the opposite behavior. For the physical properties, the coefficient of determination (R 2) ranged from 12 to 35% and the best linear regression models were fitted for the basic density, having V 0 and E d as independent variables. For the mechanical properties, the values of R 2 varied from 18 to 63% and higher correlations were found between parallel-to-grain compression strength and E d , and rigidity, static bending and Ed. Ultrasound presented the potential to estimate the properties of tropical wood species from the ASF.

Physico-mechanical properties of the wood of freijó, Cordia goeldiana (Boraginacea), produced in a multi-stratified agroforestry system in the southwestern Amazon

ABSTRACT Agroforestry systems (AFSs) integrate, through sustainable practices, agricultural and forest crops for the production of wood and food, providing environmental services, and conserving biodiversity. The freijó (Cordia goeldiana) has potential for cultivation in the Amazon for timber purposes, but data on the characteristics of its wood produced in AFSs are scarce. Our objective was to determine the physical-mechanical properties and suggest technological applications of freijó wood produced in a multi-stratified AFS established in the state of Rondônia, Brazil in 1996. Agricultural and forest species were established in the AFS in double rows with 5.0-m x 2.5-m spacing. Three 19-year-old freijó trees were harvested for chemical, physical (density and dimensional stability), and mechanical (compression, static bending, Janka hardness, and shear strength) characterization of the wood. The wood presented a chemical composition similar to tropical hardwoods, was moderately heavy (582.63 kg m-3), and had high dimensional stability in comparison with other consecrated woods on the market (longitudinal, radial, and tangential retraction = 0.25, 4.27, and 6.83%, respectively). The values determined for parallel (32.32 MPa) and perpendicular compression (8.02 MPa), specific strength (55.32 MPa kg-1 m-3), parallel (2373.33 N) and perpendicular Janka hardness (2326.67 N), strength to static bending (63.5 MPa), and shear (5.94 MPa) were similar to the values observed in other high-density tropical woods grown in either monoculture plantations or natural forests. The wood under study is suitable for manufacture of high-value-added products, such as fine furniture, residential floors, musical instruments and structural pieces.

Bonding quality of two lesser-used wood species Brachystegia spiciformis and Julbernardia globiflora from Mozambique

The objective of this study was to evaluate the density, chemical properties and bonding quality of two lesser-used Mozambican wood species known as messassas (Brachystegia spiciformis and Julbernardia globiflora) aiming at edge-glued panel production. The bonding was performed using structural adhesive polyvinyl acetate D4, semi-structural adhesive emulsion polymer isocyanate and non-structural polyvinyl acetate D3 applied at 120·m-2 and 180·m-2 weights. Density, chemistry, edge shear bonding, wood failure percentage and the finger-joint tests were performed in accordance with ISO 13061-2:2014 (E), TAPPI, EN 13354:2008, ABNT-NBR ISO 12466-1:2006 and ASTM 5572:2005 standards, respectively. The results showed that both species have medium density, high extractives and lignin contents typical of tropical wood. The emulsion polymer isocyanate adhesive was approved with better performance compared to polyvinyl acetate D3 and D4 adhesives. It can also be affirmed that Brachystegia spiciformis and Julbernardia globiflora have similar bonding behaviour and the potential for producing edge glued panel panels, especially for indoor use

Influence of weathering on surface roughness of thermally modified wood

Wood is one of the most important building materials. Thermally modified wood is entering the market and replacing wood preservatives and tropical wood species in some applications. Thermally modified wood is exposed to weathering similarly as other wood-based building materials. It has been reported that if thermally modified wood is exposed to weathering, its moisture performance might decrease fairly fast. Moisture performance reflects the material’s ability to remain dry and dry out fast when wet. The aim of this study was to determine whether this phenomenon is associated with crack formation or roughness. Norway spruce, thermally modified spruce, wax-treated thermally modified spruce, and European larch heartwood samples were exposed to artificial accelerated weathering and natural weathering for 9, 18, and 27 months. Samples were subsequently isolated, and their roughness was determined with a confocal laser scanning microscope on axial and longitudinal surfaces at 10× and 50× magnification. After weathering, roughness increased on both axial and longitudinal surfaces. This was evident from the profile 2D measurements (Ra) and surface 3D measurements (Sa). The effect of natural weathering on roughness was higher than artificial accelerated weathering, presumably due to synergistic effects of abiotic and biotic factors. This may be associated with Wenzel’s theory on the influence of roughness on the contact angles of water on the surface; namely, increased roughness will decrease the contact angle on hydrophilic surfaces.

Publication de descriptifs techniques extraits de l’Atlas des bois tropicaux

L’Atlas des bois tropicaux publié en 2016 par les Éditions Quæ en version française (aux formats papier, epub et pdf) puis en 2017 en version anglaise (aux formats epub et pdf) présente des informations technologiques sur les bois destinées à tous les professionnels qui transforment et mettent en œuvre des bois tempérés ou tropicaux. Il réunit les principales caractéristiques technologiques de 283 essences tropicales et 17 essences de régions tempérées les plus employées en Europe, associées à leurs principales utilisations. Sa réalisation a bénéficié du soutien financier de l’Organisation internationale des bois tropicaux (OIBT), et d’Agropolis Fondation pour la version anglaise. Les descriptifs techniques d’une sélection d’essences tropicales seront régulièrement publiés dans la revue Bois et Forêts des Tropiques.
 Cet ouvrage est le fruit d’un travail collectif de l’Équipe Bois tropicaux du Cirad qui, depuis des décennies, a étudié dans ses laboratoires les caractéristiques technologiques de plus de 1 200 espèces tropicales en réalisant plusieurs centaines de milliers d’essais. La collecte récurrente d’informations sur le terrain est venue compléter ces données pour constituer une base de connaissances qui se décline aujourd’hui sous différents types d’applications.
 Outre sa fonction de mémoire collective et de réservoir d’informations pour alimenter des produits documentaires de vulgarisation sur la qualité des bois tropicaux (fiches ou guides techniques, atlas, logiciels, etc.), cette base de connaissances constitue un outil d’étude des relations entre les propriétés des bois et les usages des produits forestiers.
 Aujourd’hui, les recherches et les études conduites par les chercheurs et les techniciens de l’Unité de recherche BioWooEB du Cirad continuent à alimenter cette base de connaissances sur le comportement technologique et les potentialités d’utilisations d’un nombre toujours plus important d’espèces forestières issues des régions tropicales des quatre continents.
 L’Atlas des bois tropicaux décrit les caractéristiques de 300 essences. C’est un outil de référence pour les opérateurs de la filière bois en France et à l’étranger, ainsi que pour les établissements de recherche et d’enseignement, les institutionnels, les donneurs d’ordre, les architectes, les maîtres d’œuvre, les maîtres d’ouvrage et, de façon générale, pour tous les professionnels qui transforment et mettent en œuvre des bois tempérés ou tropicaux, ou qui projettent de le faire.
 Pour chaque essence, le descriptif technique reprend les informations suivantes : famille et appellation(s) botanique(s), origine géographique, éventuelle restriction commerciale selon la convention de Washington (CITES), description de la grume, description du bois, principales propriétés physiques et mécaniques, durabilité naturelle et imprégnabilité du bois, traitement de préservation, séchage, sciage et affûtage, assemblage, classements commerciaux, réaction au feu, principales utilisations, principales appellations vernaculaires. Chaque descriptif est illustré par deux photos de débit sur dosse et sur quartier (ou faux quartier), par deux macrophotographies aux grossissements 20 et 115 et par une photo d’un ouvrage construit avec le bois décrit.
 Les détails sur le contenu de ces descriptifs techniques, sur la nature et l’intérêt des informations, des caractéristiques et des données qu’elles contiennent sont disponibles dans une notice d’informations générales sur le site web de Bois et Forêts des Tropiques, annexée uniquement à la version web de cet article.
 Jean Gérard
 Rédacteur scientifique de la revue Bois et Forêts des Tropiques et chercheur de l’unité de recherche BioWooEB

Changes of Meranti, Padauk, and Merbau Wood Lignin during the ThermoWood Process.

Thermal modification is an environmentally friendly process in which technological properties of wood are modified using thermal energy without adding chemicals, the result of which is a value-added product. Wood samples of three tropical wood species (meranti, padauk, and merbau) were thermally treated according to the ThermoWood process at various temperatures (160, 180, 210 °C) and changes in isolated lignin were evaluated by nitrobenzene oxidation (NBO), Fourier-transform infrared spectroscopy (FTIR), and size exclusion chromatography (SEC). New data on the lignins of the investigated wood species were obtained, e.g., syringyl to guaiacyl ratio values (S/G) were 1.21, 1.70, and 3.09, and molecular weights were approx. 8600, 4300, and 8300 g·mol−1 for meranti, padauk, and merbau, respectively. Higher temperatures cause a decrease of methoxyls and an increase in C=O groups. Simultaneous degradation and condensation reactions in lignin occur during thermal treatment, the latter prevailing at higher temperatures.

Mechanical Characterization of Iroko Wood Using Small Specimens

Despite their favorable physical and mechanical properties for structural use, tropical woods, such as Iroko (Milicia excelsa), present knowledge gaps to be filled mainly about their mechanical characterization, which currently limit their use or result in under- or overdimensioned structural elements. Visual classification, one of the most used methods for characterizing wood, is inaccurate in the case of Iroko due to the wide variety of geographical locations in which this species can be found. In addition, mechanical characterization using test pieces with structural dimensions leads to high and impractical costs. In this context, this study aims to verify the mechanical properties of Iroko (imported from the Republic of the Congo) from small size specimens, a process that is currently standardized only for softwoods, and to verify the correlation of different properties through bending properties and ultrasound tests. Prior to the bending tests, the speed of propagation of ultrasonic waves was measured using the direct method. The results obtained show a good correlation between density and bending properties and the velocity of propagation of ultrasonic waves.

Furfurylation of wood from fast-growing tropical species to enhance their resistance to subterranean termite

The purpose of this study was to use furfurylation to enhance the resistance of wood to subterranean termite attack. Wood samples were obtained from four fast-growing tropical wood species, namely sengon (Falcataria moluccana), jabon (Anthocephalus cadamba), mangium (Acacia mangium), and pine (Pinus merkusii), felled at a short cutting rotation. Specimens were impregnated with furfuryl alcohol (FA) solution and tartaric acid as a catalyst and then heated at 100 °C for 24 h. After conditioning, the specimens were exposed to subterranean termite attack in the laboratory according to the Indonesian standard. Furfurylated samples were found to have a higher density presumably because poly-FA filled the void space. It also had a lower moisture content because of the presence of poly-FA bulking in the wood cell wall, making it more hydrophobic. Furfurylation greatly enhanced subterranean termite attack resistance of wood, as shown by remarkably higher termite mortality, higher wood resistance class, lower wood weight percent loss, and reduced termite feeding rate. Based on the Indonesian standard, in which class I indicates very resistant wood and class V indicates very poorly resistant wood, untreated wood was class IV, but all furfurylated wood specimens were rated as class I.

Use of a pin-penetration wood density meter to determine the density of 25 Indonesian species

The pin-penetration device is a minimally destructive instrument that is widely used to estimate the physical properties of wood, e.g., density, with advantages such as reduced testing times, low costs, and fewer defects induced in the wood being tested. In this study, such a device was used on 25 Indonesian hardwood species with a strength class (SC) distribution from SC II to IV (according to the Indonesian classification of wood SCs). Tests were conducted on three different orthogonal planes, i.e., cross-sectional, radial, and tangential planes. The wood density ranged from 0.28 to 0.88 g/cm3, and the specific gravity was 0.25 to 0.76. The cross-sectional plane penetration depth of the wood was significantly greater than that of either the radial or tangential plane, whereas the pin penetration values of the radial and tangential planes were not significantly different. A prediction model for predicting the density and specific gravity of wood via pin penetration showed a significant regression. Thus, the use of a pin-penetration device was found to be suitable for estimating wood density and specific gravity in a range of SCs of tropical wood species regardless of species.

Non-Isothermal Thermogravimetry of Selected Tropical Woods and Their Degradation under Fire Using Cone Calorimetry.

For selected tropical woods (Cumaru, Garapa, Ipe, Kempas, Merbau), a relationship was established between non-isothermal thermogravimetry runs and the wood weight loss under flame during cone calorimetry flammability testing. A correlation was found for the rate constants for decomposition of wood in air at 250 and 300 °C found from thermogravimetry and the total time of sample burning related to the initial mass. Non-isothermal thermogravimetry runs were assumed to be composed from 3 theoretical runs such as decomposition of wood into volatiles itself, oxidation of carbon residue, and the formation of ash. A fitting equation of three processes was proposed and the resulting theoretical lines match experimental lines.

Furfurylation of tropical wood species with and without silver nanoparticles: Part I: Analysis with confocal laser scanning microscopy and FTIR spectroscopy

ABSTRACT This work focused on the upgrading of non-durable tropical wood species originating from fast-growing plantations of Costa Rica. Modification of such tropical woods with furfuryl alcohol, although has not been broadly studied up to date, offers a potential way to increase their low durability. The purpose of this research was to investigate the modification effects on cell wall, vessels wall, radial and axial parenchyma using confocal laser scanning microscopy (CLSM) as well as the changes in the bands of chemical composition using Fourier-transform infrared spectroscopy (FTIR). In fact, nine tropical wood species such as Cedrela odorata, Cordia alliodora, Enterolobium cyclocarpum, Gmelina arborea, Hieronyma alchorneoides, Samanea saman, Tectona grandis, Vochysia ferruginea and Vochysia guatemalensis were treated with plain furfuryl alcohol (FA), and furfuryl alcohol combined with silver nanoparticles (FA-NPsAg). Furfurylation effects were also assessed by the weight percentage gain (WPG) of wood. Results showed that WPG varied from 14.4% to 44.3% with the FA treatment, and from 12.9% to 44.5% with the FA-NPsAg treatment. In the species which exhibited a WPG over 25% with the FA treatment, fluorescence at 600 nm band occurred mostly in the cell walls of fibres, while the furfurylation degree in radial and axial parenchyma was limited. Moreover, furfurylation occurred in lesser extent in wood species with high abundance of axial parenchyma as revealed by fluorescence. Wood species such as Vochysia ferruginea, Vochysia guatemalensis, Cedrela odorata, Samanea saman, Enterolobium cyclocarpum, which showed WPGs>25%, evidenced considerable changes in the lignin structure as observed in the FTIR spectra. In particular, with the FA treatment, the changes were observed in the bands of 1711, 1652, 1561, 889, 796 and 733 cm–1, whereas, with the FA-NPsAg treatment, the changes occurred in the bands of 1711, 1505, 1426, 1370, 1224 and 1016 cm–1. Overall, no significant difference was found in FTIR spectra and anatomical fluorescence between the FA and FA-NPsAg treatment, probably because the NPsAg concentration was insufficient for a change to occur in the bonds.

CITES and beyond: Illuminating 20 years of global, legal wildlife trade

Nature has the potential to provide wide-ranging economic contributions to society – from ecosystem services to providing income to communities via fair trade of resources. Unsustainable trade in wildlife, however, threatens biodiversity and its ability to support communities and a functioning planet. It is therefore important to have clear systems in place for tracing traded wildlife. Monitoring legal wildlife trade in all species is as important as it is for trade in protected species, since flows of the legal trade correlate with, and provide cover for, illegally traded wildlife. The majority of wildlife trade research is focused on species listed in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The concurrent, considerably larger legal wildlife trade in both CITES and non-CITES-listed species, however, remains unexamined – despite the fact that if mismanaged, it can lead to over-exploitation. Here we analyzed 20 years of data from the UN Comtrade database, aiming to detail the scale, composition, and trends across all taxa of wildlife traded legally, and to indicate opportunities for improvement. From 1997 to 2016 the value of this trade totaled between US$2.9 and 4.4 trillion. Of this, $2.9 trillion wildlife was traded under “specific” codes that specify taxonomic Order and below, while around $1.4 trillion was traded under “broad” codes that declare wildlife to taxonomic Class and above. The top 10 trading nations/territories accounted for 51.4% of the total value of wildlife traded. The top commercial categories for wildlife trade were seafood (82%), furniture (7%), and fashion (furs and hides) (6%). In these three major categories, vague commodity codes such as “Fish”, “Tropical wood”, and “Other furs” were used to declare 23%, 24% and 26% of items traded, respectively – despite encompassing thousands of species. This lack of granularity imperils biodiversity as trade cannot be comprehensively monitored. We recommend a review of what species are traded under these broad code descriptions, and a distillation of codes to taxonomic Family or Genus level in the next HS Code review period, particularly in the pet, traditional Chinese medicine and furniture categories. In addition, interdisciplinary research into legal wildlife trade should be increased to provide forensic, policy, economic and social solutions to improve trade management.

Models to estimate longitudinal compressive strength of Brazilian hardwood based on apparent density

As wood is an orthotropic and natural material, there are several properties required for its use in civil construction. The apparent density has been used to estimate physical and mechanical properties of wood, as it is easy to determine experimentally, unlike other determinations, which involve the use of equipment available only in large research centers. Using the Brazilian standard ABNT NBR 7190 and linear and non-linear regression models, this research aimed to evaluate their accuracy in estimating the compressive strength parallel to the fibers (fc0) as well as their characteristic value (fc0,k). This study considered 72 tropical wood species from native forests that were divided into the 4 strength classes of this standard. For the set formed by all species, the linear polynomial model was the best fit, resulting in a determination coefficient of just over 70%.

Aromatic profiling of flavor active compounds in sugarcane spirits aged in tropical wooden barrels

Abstract The production of high quality spirits implies an aging period in wooden barrels, resulting in numerous physicochemical reactions between the wood and the beverage. Oak is the main wood used in the aging process of alcoholic beverages worldwide. However, in Brazil, the use of tropical wood species can be a viable option, allowing for innovation in the characteristics of spirits. This study aimed to determine the aromatic profiling of flavor active compounds in Brazilian sugarcane spirit (cachaça) after a 12-month aging period in new 225-L toasted and non-toasted barrels made from the tropical wood species cerejeira [Amburana cearensis (Fr. Allem.) A.C. Smith], castanheira (Bertholletia excelsa Humboldt & Bonpland), and cabreúva (Myrocarpus frondosus Allemão). The chemical characterization was carried out using the Gas-Chromatography/Mass Spectroscopy (GC/MS) scan mode, and the identification targeted on flavor active compounds (esters, alcohols, organic acids, phenolic compounds, and terpenes). Toasted and non-toasted cerejeira barrels intensified the contents of phenolic compounds in cachaça. The samples aged in cerejeira barrels exhibited the most complex profile, mainly related to organic acids and phenolic compounds. However, cabreúva barrels transferred significant aromatic terpenes to cachaça. This research presented a novel focus on the aromatic profiling of flavor active compounds in cachaça aged in barrels made from tropical wood species.

Investing in Native Tree Species and Agroforestry Systems in Brazil: An Economic Valuation

Silviculture of native species and agroforestry systems have an enormous potential for tropical wood markets, in Brazil and globally. Their economic viability is shown in this report. These results also demonstrate that the main market risk variables can be included in the valuation of forest assets, including exchange rates, inflation, production volumes, and price volatility.

Physical, mechanical, and decay resistance properties of heat-treated wood by Besson® process of three European hardwood species

Description of the subject. In Europe, the heat treatment of native wood species is gradually becoming an industrial reality. It provides a promising alternative to both the use of naturally durable, essentially tropical woods and the use of chemical preservative treatments based on biocides. Objectives. The aim of this study is to quantify the effect of heat treatment on the physico-mechanical and decay resistance properties of three native hardwood species (oak, ash, beech + steamed beech). Method. The wood was heat-treated in accordance with the Besson® process. The standard physical and mechanical tests including hardness, modulus of elasticity in static bending, static bending, axial compression, splitting and impact bending strengths, have been performed on 15 treated and 15 control associated samples for each species. The standard durability test on fungi exposed 60 treated and 60 control samples to each fungus. Results. The results show a decrease in the equilibrium moisture content and an increase in dimensional stability of heat-treated wood for the three species studied. The modulus of elasticity, hardness and axial compression strength increase slightly after the heat treatment, while static and impact bending strength and splitting strength may considerably decrease. The fungal durability of oak heartwood and ash increased until class 1, beech and steamed beech until class 3. Conclusions. The global approach of this study allows a complete and precise characterization of the technological properties of three native hardwood species after heat treatment. New uses of these native species can thus be explored.

An Improved Pheromone-Based Kohonen Self- Organising Map in Clustering and Visualising Balanced and Imbalanced Datasets

The data distribution issue remains an unsolved clustering problem in data mining, especially in dealing with imbalanced datasets. The Kohonen Self-Organising Map (KSOM) is one of the well-known clustering algorithms that can solve various problems without a pre- defined number of clusters. However, similar to other clustering algorithms, this algorithm requires sufficient data for its unsupervised learning process. The inadequate amount of class label data in a dataset significantly affects the clustering learning process, leading to inefficient and unreliable results. Numerous research have been conducted by hybridising and optimising the KSOM algorithm with various optimisation techniques. Unfortunately, the problems are still unsolved, especially separation boundary and overlapping clusters. Therefore, this research proposed an improved pheromonebased PKSOM algorithm known as iPKSOM to solve the mentioned problem. Six different datasets, i.e. Iris, Seed, Glass, Titanic, WDBC, and Tropical Wood datasets were chosen to investigate the effectiveness of the iPKSOM algorithm. All datasets were observed and compared with the original KSOM results. This modification significantly impacted the clustering process by improving and refining the scatteredness of clustering data and reducing overlapping clusters. Therefore, this proposed algorithm can be implemented in clustering other complex datasets, such as high dimensional and streaming data.

Catalytic Process in Producing Green Aromatics through Fast Pyrolysis of Wood of Five Tropical Fast Growing Trees Species

The generation of liquid fuels and chemicals is potential through a catalytic fast pyrolysis (CFP) which is a rapid, inexpensive, and promising method utilizing tropical wood biomass as starting material. There is a little known in the potential of wood biomass from tropical fast-growing trees as starting materials for the production of liquid fuel and chemicals. In this study the formation of aromatics by pyrolytic-gas chromatography/mass spectroscopy (Py-GC/MS) is evaluated on the effect of wood species with different characteristics and its cellulose component to the formation of aromatics. Fast pyrolysis of eucalyptus wood characterized with low content of ash and high percentages of hollocellulose and α-cellulose produced much high relative peaks of levoglucosan and small relative peaks of lignin derived products. Meanwhile high content of vollatile matter and high crystallinity of cellulose attributed balsa and jabon woods as feedstock for fast pyrolysis. The catalytic process in fast pyrolysis of eucalyptus decomposed the most of oxygenated compound such as levoglucosan and furfural into aromatics in the presence of ZSM-5. Coke formation on the surface catalyst might lead partly of decomposition of levoglucosan and furfural to form aromatics in the catalytic fast pyrolysis of balsa wood. Cellulose component determined on the formation of benzene, toluene, styrene, p-xylene, indane, indene, and naphthalene in catalytic fast pyrolysis of wood.

Wood identification of charcoal with Confocal Laser Scanning Microscopy

Wood identification of barbecue charcoal from commercial packages of three retailers (B1, B2, B3) in Slovenia and Croatia was performed with help of Confocal Laser Scanning Microscopy (CLSM). CLSM enabled us to image key identification features of charcoal wood that were compared with light micrographs of wood from the reference collection. Product B1 contained charcoal made exclusively of beech wood (Fagus sylvatica) and the declaration indicated the address of the producer, in Serbia which allowed traceability of the wood. The selection of wood species in product B2, consisted of red oak (Quercus cerris or Q. rubra), black locust (Robinia pseudoacacia), and cherry (Prunus avium), which could originate from Serbia, and it did not contain tropical wood as stated on the package. Product B3 contained wood from at least four (sub)topical species which could not be exactly identified to species/genus level. The declaration on the product did not allow traceability of wood. As the risks of illegal logging are high for wood of (sub)tropical origin, our results support the initiative that the monitoring of the charcoal trade should be covered by the EUTR - European Timber Regulations.

Water resistance of heat-treated welded Iroko, ash, tulip, and ayous wood

The friction welding method has been an effective criterion in determining the mechanical performance of wood joints in wood industry applications compared to traditional methods. Although it is used in structural applications, joints from linear vibration are quite sensitive to water. In this study, the water resistance of the heat-treated woods, iroko (Chlorophora excelsa), ash (Fraxinus excelsior L.), tulip wood (Liriodendron tulipifera) and ayous (Triplochiton scleroxylon), were investigated by friction linear welding. The weld line density profiles were examined. The resistance of heat-treated welded wood joints to water remarkably decreased compared to the control sample, depending on water immersion time. The highest shear strength loss was found in tulip wood (60% to 65%) and the lowest shear strength loss was found in ash wood (3%) for the heat-treated group and in Iroko wood (17%) for the control. The heat-treated samples increased in density with welding but had a slightly lower density than the control group. According to the TGA results, it was found that the thermal degradation of untreated welded woods was lower than that of heat-treated welded woods. This difference could be due to the chemical constituents of hardwood and tropical wood. X-ray computed tomography (CT-scanning) is feasible and usable for welding line density change.