Graz University of Technology
Assembly Line
No glue required: Wood and metal bonded with sound and 3D printing
While there has been quite a push to create more eco-friendly adhesives, from such things as a reusable glue made from plants to an adhesive that biodegrades after use, researchers at the Graz University of Technology (TU Graz) in Austria took another approach. Two other approaches, actually, both of which achieved bonds between a variety of wood types and two types of plastics, stainless steel, and a titanium alloy.
In the first, the researchers used a 3D-printing process they termed “Addjoining.” They were able to 3D print the various materials directly onto a piece of untreated wood in such a way that they penetrated the pores in the wood, forming a bond in much the same way an adhesive would. The team then snapped the bond apart. The second joining technique the researchers came up with was called “Ultrasonic Joining.” It used an instrument called a sonotrode to send high-frequency, low vibration waves through the juncture of the wood and the metal polymers. This created friction, which generated enough heat to bond the two materials together.
The team believes that the 3D-printed bonds could be made even stronger if the wood was etched using lasers to create more complex structures or larger pores for the other material to bond with.
Ultrasonic joining of carbon-reinforced polyamide with oak wood for manufacturing sustainable hybrid structures
The feasibility of manufacturing strong and lightweight hybrid joints of carbon fiber-reinforced polyamide (PA6-15CF) and oak wood using ultrasonic energy was successfully demonstrated. Before joining, a groove pattern was generated on the surface of the wood plate by laser texturing. Wood platelets with and without texturing were joined with the polymer using the ultrasonic joining (U-Joining) process. Mechanical interlocking at the polymer-wood interface was improved, as the grooves and open vessels on the surface of the textured wood plate were filled with the polymer composite. Therefore, the lap-shear strength of joints with textured wood was 9.2 ± 0.7 MPa, whereas the shear strength of joints with untextured wood was just 4.1 ± 0.8 MPa.