Hightech winner from Geesthacht: new technology for the bonding of plastic and metal
Dr. Sergio Amancio, research group leader at the Helmholtz Zentrum Geesthacht and junior professor at the Technical University of Hamburg-Harburg, has become the “German High Tech Champion 2013 in Lightweight Design”. He was recently honoured for the development of a new joining technology, Friction Spot Joining (FSpJ) which enables the joining of metal and plastic – without the use of adhesives.
Dr. Amancio in Japan, Foto: © K.Yanagiya
In the modern automotive industry, the topic of lightweight construction is at the very top of the to-do list. Due to the challenges of climate change and the rising costs of raw materials, a reduction in emissions and the consumption of resources has become a top priority. Moreover, manufacturers must construct vehicles which are considerably lighter in order to compensate for the huge weight of batteries, for example, in the electric vehicles of the future.
Research is, therefore, intensifying its endeavours to develop concepts which combine carbon fibre reinforced plastic (CFK) with other light-weight construction materials, such as aluminium or magnesium. How can metal and plastic be joined securely, however? Due to the complexity of the components and the differences in the chemical properties of CFK and metal, new tailor-made joining and assembly technologies have yet to be developed in some cases.
Dr. Sergio Amancio, materials researcher at the Helmholtz Zentrum Geesthacht and junior professor, was recently awarded „GHTC® - the German High Tech Champion Award 2013 in Lightweight Design“ for Friction Spot Joining – FSpJ, a joining technology , which he has researched and registered for patent approval. The prize which is endowed with 10,000 euro was presented to him before an invited audience on 18th November in the course of the scientific symposium “Green Technology made in Germany” which was held in Tokyo, Japan.
The sleeve presses into the metal layer (2), the metal gets soft (3) and upon retraction of the sleeve, the CFK deformed into the metal layer (4). [Image: Sergio Amancio]
As Mr Amancio explains, “Our new joining technology, Friction Spot Joining, offers a fast, economic and environmentally friendly alternative, as we completely dispense with the use of adhesives in this technology. We make the metal pliable at selected points.This leads to a mechanical anchoring in the CFK”. In friction spot joining of metal and CFK, a rapidly rotating sleeve is plunged into the metal layer only. The resulting frictional heat softens the metal and the CFK is melted onto its surface. The retraction of the rotating sleeve leads to a slight deformation of the CFK into the metal. Thus a bonding and a mechanical anchoring occur in the so-called transition zone of the CFK (cf. illustration).
Sergio Amancio: “A great challenge in our research into this technology, was finding out how much friction and pressure may be applied to the sleeve, in order to create the desired warming effect. As the plastic matrix and the carbon fibre network are immediately destroyed, if too much friction and pressure are applied. This is also the reason why CFK-metal composite parts cannot be riveted in the conventional way. With this new technology we have proved that this process can be completed more economically and also more efficiently.”
Now the task is to establish how secure this friction spot bond is. The scientists are carrying out numerous further investigations, e.g. into crack growth or crash behaviour. Instruments are available to them, for this purpose, in the recently inaugurated hall of the new “Wayne-Thomas Building” at the Institute of Materials Research on the Geesthacht Campus.
Der German High Tech Champions Competition: GHTC® – the German High Tech Champions Award is an integral part of the initiative “The Promotion of Germany as a Location for Innovation and Research”, sponsored by the Federal Ministry for Education and Research under the heading “Research in Germany”. This year’s GHTC Award in the category “Lightweight Design” was presented, in Tokyo on18 November 2013, to six technology developers from German universities and non-university research organisations.
CFK – Carbon Fibre Reinforced Plastic: This carbon material is both lighter and harder than steel or aluminium. However, it is considerably more expensive than these metals at present. Amongst other factors, this is due the fact that structures made of CFK – for example in aircraft construction – have so far been predominantly manufactured manually. An additional problem is that CFK can currently only be riveted or glued. This means that laborious pre-treatment procedures are required, such as, for example, pre-drilling and surface treatments of the spot to be welded. This involves considerable additional effort and expense.