"Laser joining techniques are specifically predestinated for multi-material treatment"

Automotive IQ spoke with Axel Jahn, Division Manager Laser beam joining at Fraunhoher Institute. Mr. Jahn works on providing new door design and production conceptions especially in terms of light weight issues, respecting load adapted component design and multi-material construction. In the lead-up to the 8th International Congress Automotive Doors we spoke about material trends and laser produced doors structures.

Mr. Jahn, you are working with Laser produced lightweight automotive doors structures. In your opinion, is the laser process used for lightweight door structures more demanding or complex than the one used for steel door structures?

We focused our work on the three important applications tailored blank welding, assembly and patch-work. Mainly, our laser processes are specifically developed for multi-material joining, especially in terms of joint preparation, laser spot positioning and temperature control. And additionally we are using a special transition joint element, which requires a very specific machine set-up for production. However, the actual laser joining processes we developed are generally using equipment which is commercially available.

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Multi-material joining is quite a popular topic among engineers. What is the current landscape of joining technologies and the materials that fit each other the best?

In the field of metallic multi-material joining usually mechanical joining and adhesive bonding are applied at present. Both opportunities imply a couple of disadvantages, like punctual joints and massive disturbance of the base material in terms of mechanical joining as well as a comparatively low joint strength and poor thermal resistance in terms of adhesive bonding.

The main challenge of metallic multi-material joining is the control of the intermetallic phase formation. Especially the most interesting material combinations steel-aluminum and steel-magnesium are very sensitive for that problem

A main concern regarding lightweight and composite materials is that they might not be that durable and they’re quite fragile when it comes to accidents. What role do laser processes play in strengthening these materials?

In most cases not the strength is the problem but the ductility. The intermetallic phases (IP) are usually very brittle. A very effective solution is the limitation of the IP layer thickness which normally depends on the heat input during the joining process. Therefore laser joining techniques are specifically predestinated for multi-material treatment due to their very high intensity of energy introduction.

What are the main trends that you see developing in the following years in terms of laser processes for lightweight materials?

I see a high potential in the direct metallic multi-material joining because of high practical relevance of these materials. Furthermore, also applications for joining of metal and FRP components, like cutting, surface preparation and direct joining, will be rinsing.

What does the future hold for the automotive industry regarding future materials? Lighter steel or lightweight materials such as aluminium or maybe thermoplastics?

In my opinion the mixture of materials will be increase dramatically in the future. This fact will also force a significant development in all material sections. However, the delivery of appropriate joining technologies will be one of the key aspects.

What are the topics that you look forward to hearing during the doors conference in June?

New trends in the automotive door design are very interesting for us. Especially, I hope to get into contact to OEMs and Suppliers in terms of a component design which considers lightweight aims as well as load, material and joining aspects. And finally we are looking for potential multi-material applications for our laser joining processes.

Mr. Jahn, thank you very much for your time.

Dr.-Ing. Axel Jahn received his Master for Mechanical Engineering from the University of Technology in Dresden in 1997. He worked for the Fraunhofer IWS Dresden in the Welding Group in the field of laser beam welding of high strength steels and local laser strengthening. Since 2015 he is division manager for Laser beam welding and Component design.