Fracture Mechanics of Linearly Welded Wood Joints: Effect of Wood Species and Grain Orientation

The energy release rates of beech, oak and pine wood specimens welded by linear friction were determined using double cantilever beam (DCB) tests. The influence of grain orientation both in welding along the wood longitudinal direction as well as in end-grain-to-end-grain welding to give butt joints was determined. The analysis of results was done with the experimental compliance method, based on linear-elastic fracture mechanics. The energy release rates obtained varied considerably according to wood grain orientation, wood species and welding cycle used. In many cases, the energy release rates obtained with the recently developed 150 Hz/faster weld technology were in the range as obtained for adhesive-bonded wood joints. Some cases also gave energy release rates higher than adhesive-bonded joints. Welding of butt joints by end-grain-to-end-grain welding was achieved, although the joints presented much lower energy release rates. In butt joints there appeared to be no significant difference in the energy release rates obtained for the three different timber species used.