A lucky laboratory accident may have important implications for the wood products industry. Researchers were using linear friction equipment to melt plastics between pieces of wood. On one occasion, a technician forgot to insert the plastic piece – the exciting and unexpected result was wood that was “welded” together. Since that accident, the research team has been improving the technique for using mechanical welding machines to bond wood.
The technique is now called “mechanically-induced wood flow welding”, and it produces high-strength bonds in seconds without the use of adhesive. To “weld” wood, pieces of lumber are pressed together (at 60 – 330 psi) and rubbed back and forth at high speed for a few (3-5) seconds. After a few more seconds of clamp time, the bonding process is complete. Examination of the bondline suggests that the friction between the pieces heats and melts components of the wood (mainly lignin) and loosens fibers on the surface. These fibers intertwine in a matrix with the molten lignin and solidify to form a bond that is strong enough for structural applications. The bonds are not water-resistant, thus the technology is most promising for interior joinery and furniture.
The technology is still being developed but someday “wood welding” may offer a fast, inexpensive, adhesive-free method for bonding wood.
Friction welded beech. Note the slightly burned appearance of the bond line. Photo courtesy of M. Zanetti-Pernot.
For more information, contact:
Adam M. Taylor
Tennessee Forest Products Center 2506 Jacob Drive
Knoxville, Tennessee 37996