Experimental investigations on welded double lap joints composed of timber

Fabrication of wood-to-wood connections by means of friction welding is an relatively new process holding high potential for development. To connect wooden pieces by means of friction welding, they are initially pressed against each other. The rapid movement of one of the pieces, applied simultaneously leads to friction, and heating generation, which is softening the material at the interface within a few seconds. This paper addresses the question to which extent welding of wood can be considered for structural joining of load bearing timber elements. For this purpose, experimental investigations on wood-welded double-lap joints were carried-out, in which a series of parameters, including overlap length, member thickness, etc., has been varied. This experimental campaign allowed for (a) the determination of the fracture mechanism of welded wood connections, (b) quantification of the influence of main design parameters on the strength of these and (c) delivering benchmark data related to the strength of welded wood joints, including its statistical component, for a subsequent joint strength prediction model. The experimental investigations were completed by numerical modelling of all investigated welded joints, which allowed to conclude that (1) failure of the investigated welded joints is triggered by a combination of shear and transversal stresses acting in the interface, but also that (2) joint strength is not linearly correlated to stress magnitudes.