“Steel is set to remain dominant in the large-volume segment”
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For Dr. Oliver Schauerte, Head of Group Research for Materials and Manufacturing Processes at Volkswagen, steel is the material that matters when it comes to large-scale vehicle production. Nevertheless, according to him, the development of structural materials is moving strongly towards hybridization.Schauerte also looks to the future of material development, set to be revolutionized by the new potential quantum computation will open up.
lightweight.design: The Golf 7 marks the first time a new Golf is lighter than its predecessor. The majority of its weight is due to steel. Does this make steel the lightweight material of the hour?
Schauerte: Steel does qualify as the lightweight material of the day given that the steel industry has joined forces with car manufacturers and progressed considerably in terms of new steel grades over the last decade. In future, tensile strengths of up to 2000 MPa in the sheet metal sector may even be feasible. This was almost unimaginable just a decade ago.
Will steel continue to retain its importance as a lightweight construction material in future?
Of course, each material group will have its own justification and need. For example, most of the new Audi A8 is made of aluminum. But steel will continue to prevail in the volume segment, simply because it has become more favorable due to price pressure from Asia, while the steel industry has become more competitive.
Volkswagen intends to become the top manufacturer of electric cars by 2025. Is steel set to play the starring role here, too?
Yes, we will mainly rely on steel because we are aiming for high volumes in the group. Although we also have room to consider the use of fiber-reinforced composite or aluminum for the pricier e-models, steel will remain by far the dominant material for e-mobility. One thing you have to remember along the way: If I want to use lightweight construction for electric vehicles, the most efficient way is to invest the money for lightweight construction in high-performance batteries, given how heavy and expensive batteries are. The more you boost performance, the fewer batteries you need. That’s the simplest way to make lightweight construction work. However, these are all-new fields of application for materials research.
What potential for lightweight construction can you see outside the bodywork, for example in a chassis or drivetrain?
This is where an interesting conflict of objectives arises. On the one hand, the demise of the classic combustion engine has been predicted for some time, but even so, the fact that we will continue using it worldwide for considerable time to come is a given. As materials researchers, we find ourselves at the very beginning of the chain. It is not unusual to see ten or twelve years pass from the time a material is developed to its series application in engines or transmissions. This is something you have to bear in mind during material development.
Which new materials are we likely to find in ten or fifteen years’ time in the body or drive shaft?
When it comes to structural materials, hybridization is definitely becoming the mainstream. From a technical perspective, when you consider the periodic table of elements, only four make sense for the construction of a car: iron, that is steel, aluminum, magnesium and titanium. One of these four elements will always outperform anything else found in the periodic table. Along with fibers — carbon fiber and glass fiber — there are also plastics — thermoplastics and thermosets. The future will see us developing tailor-made materials with tailor-made properties. This may even mean that these special properties differ within a component, in certain positions.
Exactly. The classic hybrid is the plastic fiber composite in which I align carbon fibers or glass fibers according to the load within the plastic matrix. This way I can create anisotropies and adjust directional stiffness and strength.
Meanwhile, steel manufacturers produce so-called sandwiches with external steels and a neutral fiber made of plastic. Or with hard steel on the outside and soft steel within. You can imagine that metals and fibers are joined together, like the well-known material Glare used in the aviation industry. Or that ceramic particles are added to cast materials to modify their stiffness. One all-new approach is undoubtedly metallic 3-D printing. This has allowed us not only to print a metallic component three-dimensionally, but also to change the powder and vary the alloy composition locally at the same time. For example, it is conceivable that local alloys could be created outside the phase diagram.
The most efficient way is to invest the money for lightweight construction in high-performance batteries.
New materials also require new production and joining techniques. With this in mind, just how difficult is it to incorporate new materials into series production?
Our field of research centers on materials and production processes for a reason. We are not simply developing a new material. For each material, we also solve fundamental questions regarding its processability, formability, joining technology, availability and so on. The basics for simulation and processability must already be created during materials development. Under normal circumstances, however, our aim is to process a new material, such as high-strength steel, aluminum or magnesium alloys, more or less in existing production facilities. Even if a component is supplied by a subcontractor, it must be capable of being incorporated into the production process. For example, in the new Audi A8, the carbon fiber rear wall unit comes from an external supplier. The unit is then completed with add-on parts at the Audi plant in Neckarsulm, before being integrated into the existing production process.
At the moment we see a range of material mixes in small- and large-series production vehicles. Carbon fiber and aluminum in one, steel in the other. Will the divide between different materials continue to grow or will the material mixes reconverge in future?
New materials or material solutions tend to go into series production “top-down.” This is understandable, because using a new material will ideally also boost demand for the material. In other words, both material producers and component manufacturers find themselves facing completely different volumes and can therefore produce more efficiently. Efficiency that paves the way, in the next step, to serve the next automotive segment.
So aluminum is likely to feature in mass production sooner rather than later.
Aluminum is already in use in a number of high-volume models, particularly at Audi. But comparing steel and aluminum is also exciting: The past two decades have seen aluminum become ever-cheaper in terms of processing and availability. But so has steel. Steel has also become far better in terms of mechanical properties. In other words, aluminum currently faces a difficult struggle to penetrate further into mass production.
Nowadays, the environmental impact of a car is assessed on the basis of emissions during its service life. Many new material developments are also oriented towards this goal. What material mix would be considered preferable if the environmental impact of a car were assessed on the basis of the entire life cycle, up to and including recycling?
If you compare a new material — let’s just take a fictitious metal-fiber sandwich — with conventional materials, the life cycle assessment of the new material usually looks less than stellar. But we also know that using a new material in series production also triggers activities among other players. All of which means that if a group like Volkswagen embarks on series production with a certain hybrid material, a recycling business featuring the very same hybrid material will soon emerge. More energy-efficient means of manufacture and processing are also added to the mix, simply due to economies of scale. In this respect and from an ecological perspective also, a lightweight construction solution must always be pursued first and foremost, and this is also the preferred long-term option with the environment and CO2 balance in mind.
If we take the example of carbon fiber, this means …
... that we already have excellent ideas about how to use carbon fibers efficiently, but also how to recycle them and how to reuse the waste. These are ideas that first emerged during CFRP development work. Producing carbon fiber is a very energy-intensive process. But if you have a corresponding need for C-fibers, you can also come to an agreement with a C-fiber manufacturer, for example, that the energy for production be produced in an ecologically sound manner, by wind power or hydropower.
What advice would you give composite manufacturers to get their continuous-fiber-reinforced plastics into mass production?
A distinction has to be made between carbon fibers and glass fibers. Glass fibers are very inexpensive, but require processes that can streamline highly automated processing. The cost of carbon fibers, meanwhile, remains very high, although good progress has been made. For the next step, however, developing carbon fibers with better stiffness and/or strength may be preferable, so that there is a prospect of cutting component costs simply by reducing the quantity of fibers used. This might be a better option than simply further hiking up the cost of existing fibers.
Mr. Schauerte, where does materials research go from here? What is the next big thing?
Actually, the phase in which we now find ourselves is one in which all-new opportunities in materials research are opening up. It is no longer just a matter of taking two percent more of this alloying element and one percent of that alloying element, to then have perhaps three percent more tensile strength. No, today we can use new simulation methods to develop completely new materials at unprecedented speed. This is of course very exciting and these possibilities are only just beginning to emerge.
Are these simulation methods really new, or is there simply more computing power available?
What I’m talking about here is quantum simulation, which we now use very successfully in the area of functional materials. Although people have already been familiar with such mechanisms since the 1920s, for example in Heisenberg’s uncertainty principle, it has not yet been possible to use them in materials development. All key physical material properties are described in terms of how electrons interact with the atomic nuclei or the atomic nuclei of neighboring atoms, as essentially described by the famous Schrödinger equation, which, unfortunately, is unsolvable.
Today, we can harness new simulation methods to develop completely new materials.
But you’re still going to solve it …
And by how much could the stiffness of high-strength steel be increased, if it were possible to calculate all these processes?
How does the materials industry benefit from these new opportunities?
Unfortunately, the materials industry is not necessarily a growth sector in Germany. The aluminum and copper industries in particular — as well as magnesium producers — face massive pressure due to high energy costs in Germany. The same applies to plastics manufacturers. And steel producers face the dual problem of low-cost steel from China and high electricity prices. For this reason, material innovations for the industry always constitute an opportunity to reposition itself with new developments.
Volkswagen is benefiting from low steel prices.
Should steel capacities in Europe fall drastically at some point in the future, this may harm the automotive industry.
70 percent of all innovations are said to be material-related. How is materials research in Germany doing?
We already occupy an enviable position in materials research. Here we are in the Open Hybrid Lab Factory, and Germany has seen several similar research facilities established over the years. There is a large number of material clusters. A great deal has also been built up on the research side, in CFRP development for example. Of course, we also observe international research activities in a range of areas. As far as classic materials development is concerned, we in Germany are market leaders, or at least well ahead of the competition. We have brought together many associations, the CCeV or CFK Valley Stade, for example, for carbon fiber development, or the German Society for Materials Science, which also wants to spark interest in materials and materials research among young people, Dechema and various organizations within the VDI, as well as numerous other material-oriented interest groups, to bring research and industry together for plastics. Such moves have already left their mark.
Finally, a short question: Should lighter vehicles cost more?
I think yes, it’s inevitable that the lighter the vehicle, the costlier it will be. That’s why the most efficient lightweight materials are also predominantly found in luxury and super sports cars.
Dr. Schauerte, thank you very much for speaking with us.
Interview: Thomas Siebel