Researchers at Graz University of Technology (TU Graz) in Austria developed not one but two adhesive-free methods to bond (metal) polymers and wood together.

Wood is a renewable and strong material that could be used in vehicle production, replacing energy-intensive or difficult-to-recycle materials. However, it has been a challenge to join wood and other materials in the vehicle, like polymer composites and metal, in a robust way.

To change this, the research team successfully tested two methods that resulted into extremely strong bonds without the use of adhesive of screws. The first one, dubbed AddJoining, the researchers affixed a component made of polymer composite to and printed directly onto a surface using a 3D printing process. The printed material penetrates into the wood pores, where a chemical reaction occurs, similar to the reaction of glue with wood. The resulting connections were highly successful in mechanical load tests.

For the second method, the team made use of high-frequency vibration with low amplitude. Called Ultrasonic Joining, in contact with the base component, in this case, polymer or a polymer composite material, the friction generates heat at the interface which melts the surface of the polymer part.

Photos: TU Graz