Thermochemical changes during wood-dowel welding were investigated in two Canadian hardwood species commonly used for indoor appearance applications: sugar maple (Acer saccharum) and yellow birch (Betula alleghaniensis). The original reference wood sample and the welded interface between two bonded wood pieces, a dowel and a substrate, were compared to explain differences in mechanical properties between species. Pyrolysis gas chromatographymass spectrometry (Py-GC/MS), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) were used. The gases emitted during wood welding were determined by Py-GC/MS and gas chromatography coupled with a thermal conductivity detector and a flame ionization detector (GC-TCD/FID). Results showed that thermal welding of birch and maple woods degrades hemicelluloses and affects lignin polymer through depolymerisation. Welding effectiveness is therefore directly associated with the properties of the original wood constituents, primarily lignin and carbohydrates. The lignin-related changes at the welded interface were greater for sugar maple than for yellow birch, corroborating mechanical property differences observed between the two species. The gases proportions were similar for both species and no harmful gases were detected in the smoke released during welding process. Untersuchung von thermochemischen Veränderungen in kanadischen Laubholzarten beim Reibschweißen Zusammenfassung Untersucht wurden die thermochemischen Veränderungen, die beim Einbringen von Dübeln mittels Reibschweißen in zwei in Kanada für Innenanwendungen häufig verwendeten Laubholzarten Zuckerahorn (Acer saccharum) und Gelbbirke (Betula alleghaniensis) auftreten. Die Schweißfläche zwischen den zwei verbundenen Holzteilen, einem Dübel und einem Holz, und dem nicht betroffenen Holz wurden verglichen, um unterschiedliche mechanische Eigenschaften beider Holzarten anhand von Pyrolyse-Gaschromatographie-Massenspektrometrie (Py-GC/MS), Fourier-Transformations-Infrarot-Spektroskopie in abgeschwächter Totalreflexion (ATR-FTIR) und Röntgen-Photoelektronenspektroskopie zu bestimmen. Die beim Reibschweißen emittierten Gase wurden bestimmt mittels Py-GC/MS und Gaschromatographie gekoppelt mit einem Wärmeleitfähigkeitsmesser und einem Flammenionisationsdetektor (GC-TCD/FID. Die Ergebnisse zeigten, dass beim Reibschweißen von Birken-und Ahornholz Hemicellulosen abgebaut werden und auch das Ligninpolymer depolimerisiert wird. Die Güte der Verschweißung hängt deswegen direkt von den Eigenschaften der zu verschweißenden Holzbestandteile ab, insbesondere dem Lignin und der Kohlenhydrate. Veränderungen des Lignins an der Schweißfläche waren bei Zuckerahorn größer als bei Gelbbirke und bestätigen damit die unterschiedlichen mechanischen Eigenschaften beider Holzarten. Die Gasanteile waren bei beiden Holzarten vergleichbar und im Rauch, der beim Schweißen entsteht, wurden keine schädlichen Gase festgestellt.

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Rotational wood-dowel welding has been shown to rapidly produce wood joints of considerable strength without any adhesive. The technique offers an opportunity to increase productivity and reduce costs in the fumiture industry. The objective of the study was to define optimal wood-dowel welding parameters for two North American hardwood species fi^equently used for indoor appearance products: sugar maple {Acer saccharum) and yellow birch {Betula alleghaniensis). Optimized parameters for individually studied species were determined using a rotational wood-dowel welding machine designed for the technique. A comparative analysis of wood-dowel welding parameters was performed. The investigated parameters for both species were grain orientation, rotational speed, and insertion speed. Temperature profile measurements at the interface during rotational wood-dowel welding were also carried out. Optimal welding mechanical properties were determined from the dowel withdrawal strength using a standard tensile strength test. Results revealed a significant interaction between species, rotational speed, and insertion speed. Sugar maple produced wood joints with higher withdrawal strength than yellow birch. The best results for sugar maple and yellow birch were obtained with a rotational speed of 1000 rpm. A 25mms~ insertion speed produced significantly stronger welded joints in sugar maple than at 12.5 mm s~'. For yellow birch, a 16.7mm s^' insertion speed provided the best results. Both species and rotational speed had a significant effect on peak temperature at the interface during welding. Peak welding temperatures with optimal parameters were 244 and 282 °C for sugar maple and yellow birch, respectively.

This study assessed the moulding, drilling, turning, sanding, and routing properties of seven plantation-grown hardwood species from southeast Australia to evaluate their potential as a resource for the manufacture of high quality furniture and furnishings. Eucalyptus grandis, Eucalyptus saligna, Corymbia maculata, Eucalyptus camaldulensis, Eucalyptus sideroxylon, Eucalyptus cladocalyx, and Eucalyptus globulus were machined using different tools, and the surface quality obtained was visually graded. A sanding sequence of 100-150 grit produced satisfactory surfaces for furniture manufacturing for most studied species. Usually, a feeding direction against the rotational direction of the tool showed best results and reduced incidence of corner breakout when routing. Overall, high-density plantationgrown Australian hardwood species performed well during machining trials with the use of appropriate parameters and cutting tools allowing overcoming some typical processing difficulties for some species.The data obtained within this study will allow optimising the machining process of plantation-grown wood in Australia and increase value from the current plantation resource.

aOptimal linear wood welding parameters along the end-grain-to-endgrain faces were determined for Eucalyptus saligna, Eucalyptus pilularis, and Corymbia maculata. Joints made using Eucalyptus saligna showed a significant interaction between welding time (WT), amplitude (WA), and pressure (WP). A preheating phase of 3 s at 0.4 MPa WP and 0.75 mm WA coupled with a WT of 2 s at 2.0 MPa WP and 1.5 mm WA provided the best shear strength results of 5.1 MPa. Joints made using Eucalyptus pilularis and Corymbia maculata snapped once the holding pressure was removed, suggesting that end-grain-to-end-grain welded fibers cannot withstand the thermal stresses generated when the surface to be welded is too small (e.g., 13.5 cm 2 ). However, grain orientation had a significant effect on the weld mechanical properties, as very strong edge-grain-toedge-grain joints were produced with Eucalyptus pilularis and Corymbia maculata (9.5 and 6.2 MPa, respectively). The joints made of Eucalyptus saligna also showed significant improvement (7.3 MPa). Energy efficient combinations were usually those involving low WA and short WT, as WP had a marginal effect on energy consumption during the welding process.