Lightweight Construction Summit 2018
"Lightweight Construction is Even More Urgent in the E-Mobility"
Heinrich Timm, member of the Management Board of Carbon Composites e. V. and for many years head of the Audi Lightweight Construction Centre, talks about the potential of holistic, systemic lightweight construction, its significance in e-mobility and why lightweight construction has a marketing problem.
Mr. Timm, to what extent is the holistic, systemic lightweight construction already anchored in the minds of vehicle developers?
First of all, every systemic approach is characterized by a look beyond single issues and the consideration of a system in its entirety. In my view, this definition is self-explanatory and describes the strive to develop even better approaches to solving a certain challenge. This naturally also applies to lightweight construction. Systematically and holistically dealing with challenges holds enormous potential for progress. Individual technologies can be used even better if they are used intelligently.
What is the concrete potential you see in this technology?
Let's take a look at the lightweight construction technology "Carbon Composites", for example. At first glance, carbon is an expensive material. The allegedly high costs per kilogram of the material are often reason enough to stop here and stick with familiar materials. There are many possibilities for economical lightweight construction using carbon composites — especially when lightweight construction is accompanied by significant functional improvements.
The basic prerequisite for developments using fiber technologies is to systematically take anisotropy into account, i. e. the technology should preferably be used in cases with clear load conditions and should not be used as "black metal" for all kinds of applications. Then manufacturers can achieve lightweight grades which ensure that the higher prices for this material pay off and make carbon fully competitive to metals. At the same time, carbon can improve the functional properties of a part. In short: Entrepreneurs should not base their decision on prices per kilogram but rather on positive business cases.
Hybrid lightweight concepts are also often combined with carbon composites.
Yes, because in addition to its lightweight construction potential, the material offers the ideal conditions for use as a composite material. With little additional weight, you can achieve an enormous functional improvement at a very reasonable price.
Can you give a few examples?
Easy-to-understand examples include the higher rigidity of truck semitrailers that can be achieved by applying CFRP laminates to the upper and lower sides of the frame in the area of maximum bending stress, the higher load-bearing capacity of bridges due to prestressed CFRP strips, the greater span widths of bridges due to CFRP tensioning ropes instead of steel cables or the improvement of intrusive resistance in crash zones. In hybrid material composites with alternative fibers, from aramid to glass fibers, the optimum concept can be defined precisely in line with functional and economic requirements.
So carbon composites and low-cost are no contradiction?
Not at all, especially if you take the systemic approach across the entire value chain into consideration. Due to the relatively low investment costs for composites in tool and fixture construction right through to functional components, composites ensure very economical business cases for small and medium volumes.
This is an advantage for new companies starting out on a "greenfield site"?
It can at least provide a considerable relief. But composite modules also allow manufacturers to react to the greater diversification of volume models, for example due to the many alternative drive concepts, very flexibly and at reasonable investments costs.
Does an electric car even need lightweight construction?
Everything that is moving profits from lightweight construction because it leads to an effective reduction in energy consumption. Electromobility is not just the uniform electric car. The lack of differentiation often reveals very controversial views. Initially, electric cars were intended to reduce emissions in urban centers. The systemic approach to meeting this requirement resulted in an e-vehicle designed to meet the mobility needs of everyday urban life. This means it has a limited but sufficient range, a relatively small battery capacity and thus a low battery weight and relatively low power consumption per 100 kilometers. This concept has the potential to reduce pollution in urban centers drastically.
The trend, however, is ‘overweight’ electric cars, and that comes from the chosen system approach, which states: "We want long-distance capabilities with a range of 500 kilometers and preferably an SUV". These concepts require 650 to 800 kilograms lithium batteries, depending on the standard or real range. Concepts based on this systemic approach consume a correspondingly high amount of electricity. Hopefully, on the basis of CO2 emission figures for battery production and German power generation, it will be clear that systemic lightweight construction in e-mobility is extremely important, if in the end, the CO2 emission into the atmosphere by electric vehicles should be below that of internal combustion engine cars.
But you would agree that the significance of lightweight construction has changed when it comes to e-mobility — not least because of the recuperation of the braking energy?
On an emotional level, e-mobility is currently having a very strong impact on the overall situation of lightweight construction — albeit driven by populism. In fact, the importance of lightweight construction has not changed at all. Quite simply because physics and the law of inertia do not change. Each mass that needs to be accelerated requires a corresponding energy equivalent. The source from which this energy is drawn is completely irrelevant to the mass inertia.
Concepts that allow for the recuperation of energy naturally offer a certain degree of relief — according to my research, inside towns and cities, the efficiency of recuperation is expected to be 69 % and 62 % outside towns, while on the motorway the effect of recuperation is going to be negligible. However, in the case of electric cars on the market they will find that with a weight delta of 60 % there is a power drain delta of 45 to 50 %.
That sounds like a plea for lightweight construction?
The emotional insignificance of weight in electric cars, we should by no means take lightly. Populists are very successful in spreading this message to the public because it is easy to convey that no CO2 comes out of the socket and that the full torque of the electric motor makes even very heavy cars appear dynamic over the entire speed range. However, these supposed experts are happy to ignore the fact that this dynamism results in correspondingly high power consumption. In countries such as Norway, which generates its electricity almost exclusively from renewable sources, the high electricity consumption of heavy electric cars may not pose a major problem, but in Germany, Eastern Europe or Asia it does. Here, the high power consumption of electric vehicles results in a very serious impact on the climate.
Do you consider electric cars as the mobility concept of the future?
Electric drives are part of it. However, based on today's state-of-the-art technology they are certainly not the best solution for every mobility requirement, and not in every country they are a way to improve the environment and climate. I very much hope that politicians and decision-makers will integrate e-mobility into their strategies with the necessary differentiation and that the development of alternatives will pursued seriously and intensively. But this obviously requires marketing based on facts — and a world that is open to facts again.
This article was first published by Automobil Industrie.
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