Into a wall at 350 kmph
Or: How do you actually test CFRP materials in a Lamborghini?
Get EDAG employee Lukasz Lasek from Neckarsulm to talk about his favourite subject, and his enthusiasm for high-end sports cars is unmistakable. As is his enthusiasm for driving them into walls at 350 kmph. In this borderline area of automotive engineering, at the point where unchartered technological territory and maximum requirements come together, intensive testing is the only way of gaining any real insight into the materials used. It is all about clever designs that differ completely from any of the cars we see on the road, high-performance materials bonded together with adhesives, and not just a top class sports car but also a top class team that already knows what will come after CFRP.
Nearly € 200,000 for a spaceframe with a difference
In the present time, with unlimited cloud computing capacity, endless memory capacity and algorithms that can create complete worlds on the smartphone, it comes as no surprise that great importance is attached to virtual crash tests in automotive testing. Standardised and extremely reliable, virtual simulations nowadays reflect reality. Nevertheless, we enter unknown territory with every new high-tech material. All the more so if it is put to use in a vehicle that challenges the limits of ph
sical feasibility. We are, of course, talking about the use of CFRP in the new Lamborghini Huracán.
For just under € 200,000, the buyer gets a vehicle that, compared to the cars typically seen on our roads, does not have a self-supporting body. Instead, it has a so-called spaceframe. Various profiles are joined together with cast nodes to give a sophisticated structure designed with one particular advantage in mind: reduced weight combined with stiffness. For the calculation, or virtual testing, of such high-performance structures consisting of aluminium and CFRP, there is no possibility of anyone being able to draw on a decade's experience in series production. It is not possible to pull a perfect calculation method out of the hat just like that. It will always need to be adapted. Individually, to the material and the vehicle. All the better then, if you can rely on a team that has already mastered this challenge in earlier projects, and so knows how to solve the problem.
CFRP - what it boils down to is "direction"
The nature of the great challenge that Lukasz Lasek and his team had to solve lay in the special properties of CFRP compared to materials such as steel or aluminium. Conventional materials have what are known as isotropic properties. This means that, regardless of the direction from which a load is applied to the component, the material will always behave in the same way. To put it simply, a force from the front can bend a steel plate in exactly the same way as a force from behind. With CFRP, the very opposite applies. In this case, whether a component breaks or is able to withstand a force depends on the direction from which it is applied. The reason for this can be seen with the naked eye: the differently aligned fibres in CFRP. For each component, the individual fibres must be correctly positioned (e.g. rotated through 90 degrees relative to one another) to ensure the necessary properties. If the fibre arrangement diverges by even just a few degrees, this will considerably reduce stiffness and therefore the stability of the component. Bearing in mind that CFRP components of this type are still hand-made, this is especially critical.
And simulation and the virtual crash test must provide early answers to precisely these weak spots, be they small or large, not just for driving the racing machines, but also for their production. What makes things more difficult is the fact that aluminium bonded with CFRP in the Huracán presents further possible weak spots that need to be tested.
Where might a joint break? How stiff is the car overall? Where do unpleasant vibrations and noises occur when the car is being driven? Can the Huracán survive a head-on, side or rear collision? Through to the question of how the tools for producing the Huracán will need to be designed in order to meet quality requirements – the 41-year-old mechanical engineer's team have accomplished a great deal. Using their own calculation methods and processes.
The next step after CFRP
CFRP is hip. No doubt about it, it is a current trend. More than any other material, it stands for brand values such as "innovative" or "sustainable" on account of the possible weight savings it can generate. However, if a list is made of all its advantages and disadvantages, then the question as to whether there might not be something better is definitely justified. A solution that would also work in high-volume production.
SMC is currently being treated as a possible successor to CFRP. A dough-like moulding compound with much shorter fibres. This is attended by almost isotropic properties and simple formability - everything needed for high-volume production. As yet, there is no way of knowing whether SMC will in the future be used in the mid-range segment as well as in high-end sports cars. Lukasz Lasek and his team, who are already putting their money on this "trend after the trend", are already regarded as SMC experts. With the work on the Huracán, EDAG have not only proved that the company is in a position to master highly complex vehicle demands on the very edge of what is technically feasible, but also that we think ahead. Beyond current trends. To technologies and processes that could well be moving people tomorrow.
The next exhibition:
21st International Congress,
Advances in Automotive Electronics
27.06.16 - 28.06.16
Forum am Schloßpark
Stand No. 29, Ludwigsburg