A research team from Graz University of Technology (TU Graz) in Austria has introduced two innovative techniques for joining wood with metals and polymer composites without using adhesives or screws. One of these methods, called AddJoining, utilizes additive manufacturing to bond wood with polymer composites. The second technique, known as Ultrasonic Joining, employs high-frequency vibrations to attach materials to wood.
These patent-pending techniques hold significant potential for industries such as aerospace, automotive, and furniture manufacturing. By enabling the use of wood—a strong, lightweight, and renewable material—these methods could encourage the adoption of more sustainable alternatives to non-renewable or difficult-to-recycle materials. “Our motivation is clearly environmental protection,” stated Sergio Amancio, the leader of the TU Graz research team.
The AddJoining process involves 3D printing a polymer composite directly onto an untreated wood substrate. The bond is formed as the polymer penetrates the wood’s pores, creating a chemical reaction similar to traditional gluing. According to the researchers, the resulting bond demonstrated remarkable strength in mechanical tests. Researcher Gean Marcatto noted, “After the joint fractured, we observed polymer within the wood pores and broken wood fibers in the polymer, indicating the fracture occurred in the materials themselves, not at the joint.”
The Ultrasonic Joining technique operates on a similar principle, but instead of direct 3D printing, it uses high-frequency vibrations to create the bond. A sonotrode applies vibrations to the wood, causing frictional heat that melts the polymer or composite material, which then seeps into the wood’s porous structure. This method is particularly suited for larger components and 2D structures. Awais Awan, another researcher, mentioned, “This technique allows for precise, localized joints, which can be further strengthened by laser texturing the wood.”
The research team tested various materials, including wood types like beech and oak, and base materials such as carbon-fiber-reinforced polyamide, polyphenylene sulfide, stainless steel 316L, and Ti-64 alloys. They are now seeking industrial partners in the automotive, aircraft, and furniture sectors to further develop these multi-material joining methods.
