Experimental investigations and probabilistic strength prediction of linear welded double lap joints composed of timber

Wood-to-wood bonds obtained by means of friction welding are a relatively new type of connections holding high potential to compete with existing structural adhesives, since a load bearing bond is formed almost instantaneously. 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 in form of tensile-shear tests on welded double-lap joints were carried-out, in which a set of parameters, including overlap length and layer thickness, has been varied. In addition to the experimental analysis, the stress-strain state inside of the connection was determined numerically, taking into account the mechanical complexity of the involved components. It could be concluded that (1) failure of the bond is triggered by a combination of shear and tensile stresses acting in the interface, but also that (2) joint strength is not linearly correlated to stress magnitudes. The mechanical behaviour of the welded interface was characterised by a series of off-axis tests, including its statistical components. The results from this characterisation and the numerical modelling were combined in the framework of a strength prediction routine. Finally, experimental and numerical results are compared, allowing for a validation of the suggested approach.