The renewable raw material wood is climate-neutral, light and strong at the same time, and therefore fundamentally attractive for use in automotive construction. A strong bond between wood and other materials, such as metals and plastic composites in vehicles, has been a challenge so far. A research team led by Sergio Amanzio at the Institute of Materials Science at the Technical University of Graz, joining Technology and Technology Development – Gian Marcotto, Awais Avon, Willian Carvalho and Stephan Herbst – have now successfully tested two techniques. Achievable without glue or screws. The application of the techniques to the material wood is patented and can be used in the aircraft industry, automobile construction and the furniture industry.
By joining technology and Additive manufacturing Wood can replace less stable materials
Both joining techniques are suitable for their own application areas, and peaches were used as test materials. Or Oak wood and a carbon fiber reinforced polyamide and polyphenylene sulfide, as well as 316L stainless steel and Ti-64 alloys are used. “Our motivation is clearly environmental protection,” says Sergio Amancio. Through new manufacturing processes, the renewable raw material wood can replace components made from energy-intensive or difficult-to-recyclable materials.
Addition: 3D printing leads to connection through wooden holes
at AdditionThe technology is applied to a surface – in this case wood – and a component made of plastic composite materials is printed directly using a 3D printing process. The printed material penetrates the wood pores, where a chemical reaction occurs, similar to the reaction of glue with wood. The resulting joints were very successful in mechanical stress tests. “After the structure broke, we were able to find the plastic in the wood holes and the wood fibers in the plastic, which suggests that there was a break in the wood or plastic, but not in the joint,” explains Gian Marcato, a postdoctoral researcher. The company worked on this process. These successful tests were carried out on untreated wood surfaces.
Pre-work by etching or lasering a micro- or nano-structure into the wood can create even more durable connections to increase the holes and connection surfaces. “But we wanted to work with as few steps as possible, above all, without chemicals,” explains Sergio Amancio, the indirect objective. “We can best use this technology with complex geometries because the components are printed directly onto the surface – whatever geometry is required.”
Ultrasound ensures a stable point attachment
During ultrasonic coupling, a wooden component is vibrated by a sonotrode. When in contact with the underlying component – in this case plastic or plastic composite material – friction generates heat and the wood penetrates the surface of the underlying component. In this way, a more stable point connection can be achieved, a combination of mechanical interlocking (the melted plastic solidifies back into the wood) and adhesion forces. “This technology is very suitable for long components and 2D structures because we achieve a very targeted connection instead of a flat connection,” explains Awais Awan, who dedicated his PhD to joining the technology using ultrasound. These connections have been mechanically tested very successfully. through target surface treatment and adjustment of pore structure Or Surface texture can also improve hybrid bonding.
In the future, the team wants to further refine the technologies with partners from the automotive, aerospace and furniture industries.
This study has Department of Expertise”Advanced Materials Science“ One of five strategic focus areas at TU Graz.
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