The Influence of Different Wood Modifications on Pull-out Force of Rotary Welded Dowels

The increasing use of modified wood justifies the intention to use it in joints made by rotary welding with dowels. Thermal modification, for example, increases the dimensional stability of wood by reducing its hygroscopicity and water absorption, but it is difficult to glue or to rotary weld due to the appearance of cracks. This can be avoided by changing the optimal welding parameters, which on the other hand directly affects the reduction of the pull-out force by more than 25 % depending on the type of the modified base. In the case of welding wooden dowels into wood modified with citric acid, the reduction in pull-out force is even greater. Due to the significant reduction, the use of this type of modification for wood welding is questionable. When citric acid modification is extended to the dowels, the dowel becomes a problem due to its lower tensile strength, which is even lower than the pull-out force of the welded dowel.