In ultrasonic joining, wood and base component are joined by frictional heat. Photo: Wolf - TU Graz
 
Alternative in car and aircraft construction: New joining and additive manufacturing processes allow adhesive-free joining of wood and metal

Researchers at Graz University of Technology have succeeded in joining wood with metal and plastic composites extremely firmly using 3D printing technology and ultrasound.

Wood is climate-neutral, light, strong - and therefore fundamentally attractive for use in vehicle construction, for example. One challenge to date has been the robust connection between wood and the other materials in the vehicle. A research team at Graz University of Technology has now successfully tested two techniques with which such extremely strong connections can be achieved without glue or screws.


Addjoining uses 3D printing to print a component made of plastic composites onto wood. Photo: Wolf - TU Graz

PRESSED
The two joining techniques are each suitable for their own areas of application. The test materials used were beech or oak wood and a carbon fibre-reinforced polyamide and polyphenylene sulphide, as well as 316L stainless steel and Ti-64 alloys. In addjoining technology, a component made of plastic composites is applied directly to a surface - in this case wood - 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. According to Graz University of Technology, the resulting joints were highly successful in mechanical load tests.

SONICATED
In ultrasonic joining, a wooden component is vibrated by a sonotrode. On contact with the base component - in this case plastic or plastic composite material - the friction generates heat and the wood penetrates the surface of the base component. The result is a very stable point connection, a mixture of mechanical interlocking and adhesive forces. This technique is particularly suitable for long components and 2D structures, and these joints have also been successfully mechanically tested. A patent application has been filed for the application of these techniques to wood and they could be used in the aircraft industry, the automotive industry and the furniture industry.

Source: tugraz.at