SHORT COMMUNICATION Wood welding: A challenging alternative to conventional wood gluing JEAN MICHEL LEBAN 1 , ANTONIO PIZZI 2 , MILENA PROPERZI 3 , FREDERIC PICHELIN 3 , PIERRE GELHAYE 1 & CHRISTOPHE ROSE 4 1 LerFob, INRA, Champenoux, France, 2 ENSTIB-Lermab, University Henri Poincare ´, Epinal, France, 3 SWOOD, Swiss School of Engineering for the Wood Industry, Biel, Switzerland, and 4 INRA, EEF, Champenoux, France Abstract The recent finding of a new way to assemble two pieces of wood by mechanically induced wood welding opens a new and challenging perspective for producing more environmentally friendly wooden products, i.e. without glue. This process, recently applied to solid wood, needs to be better understood in order to investigate the dependence of the variability of wood properties on the welding parameters. The two applications presented are the linear vibration welding and direct rotational friction welding. In each case different wood species were tested. In the most favourable cases the wood joints yielded structural grade strength. The resulting bond densification was analysed by the mean of wood density maps for oak, beech, spruce and pine. If this technique proves successful, it could change significantly the future of the furniture industry. The objectives of this article are to present the main results obtained so far and to suggest different research areas needed to improve this new way of jointing solid wood. Keywords: Wood anatomy, wood bonding, wood density, wood welding. Introduction For almost all contexts where wood is involved as a construction material it is necessary to join pieces of wood to each other either mechanically or using more or less environmentally friendly glues. Among other things, these technological necessities impact badly on the life cycle analysis scoring when wooden products are compared with products made with other materials. The recent finding of a new way to assemble two pieces of wood by mechanically induced wood welding opens a new and challenging perspective for producing more environmentally friendly wooden products, i.e. without glue. The objectives of this short communication are (1) to present the main results obtained with this technique applied to wood and (2) to illustrate the importance of the wood anatomy on the quality of the bonded interfaces. Different research areas to investigate in order to understand and improve this new way of jointing solid wood are suggested in the concluding section. The method Friction welding is a technique in which the heat needed to melt the material is generated by pressing one of the samples to be joined against the other and rapidly vibrating it through a displacement. The heat generated by the resulting friction melts the material at the interface in a few seconds. Then the vibration is stopped and the parts are held together under pressure until a solid bond is formed. For thermo- plastic materials, such bonds are permanent and have a strength approaching that of the parent material (TWI, 2005). The main welding parameters involved in this technology are motion amplitude and frequency, friction pressure and holding pressure duration. These parameters are generally interdependent, and weld property testing would be undertaken for an application before any industrial implementation. Since the pioneering work performed in Germany (Sutthof et al., 1996) it has been demonstrated that this technique can be applied to solid wood. This new context for assembling wood was then more Correspondence: J. M. Leban, LerFob, INRA, FR-54280 Champenoux, France. E-mail: leban@nancy.inra.fr Scandinavian Journal of Forest Research, 2005; 20: 534  /538 (Received 12 April 2005; accepted 21 October 2005) ISSN 0282-7581 print/ISSN 1651-1891 online # 2005 Taylor & Francis DOI: 10.1080/02827580500432305