Page 55 - Australasian Paint & Panel Magazine Sep-Oct 2018

TECH TALK AUDI
connection with the steel panel lying underneath). How do we replicate this in workshop conditions? So we developed a method where we use a blind rivet to repair a friction weld.”
Then the Audi engineers have to test the method to see if it will produce the same results as the production joining technology.
It was the same process with flow drill joins. “We started with a colleague from development and asked him how he wanted to remove this part and developed the repair method for this. If we use laser beam welding on the roof, aluminium to aluminium, we know bodyshops can’t use laser beams. So we had to choose an alternative method, in this case bonding. All of these joining methods that can’t be replicated in a repair scenario, like grip punch riveting, we find a solution for.”
With CFRP one of the first steps was to establish how to remove parts. They tried with a saw, then a hairdryer, a miniaturised heat inductor and a heat lamp from the bodyshop.
“We had to experiment to find out what the ideal temperature is to remove the part. In the end we found the solution and this involved developing heat pads,” Adous said.
“Another example is if we repair a carbon fibre part and we use a normal steel screw we can have corrosion problems. So it very important for us that our repair methods are also tested for endurance. Using the wrong material can cause a great deal of damage.”
All of these methods need to be crash tested and initially this is carried out in a series of computer simulations. “This is where we see how the car’s structure will behave in an accident and this will also influence our research. As an example, on the high strength steel part in the body cage there is a lot of damage in a crash. We know that it would not be cost efficient to replace the whole part,
so we have to develope a specific repair method where we cut only in the area where the damage is located, put the new part inside, then add some reinforcements and weld that in.
“Obviously, cutting in the exact position we specify is essential because we have run crash simulations on cutting the pillar in other locations and the car body structure did not behave the same way. So where we have extensive damage, we can experiment with different repairs and then see how the part performs in a number of crash simulations and eventually in real crash testing. Of course, the repair also has to be tested in regards to corrosion.
“We worked out for CFRP that we use stainless steel rivets to avoid corrosion and then developed a special tool and the methods to remove them without damaging the resin.”
The problem with carbon fibre is that the damage is often not visible from the outside – if you can see it then it’s relatively easy to fix. “So, for the R8 we developed a special ultra sonic testing camera with a Norwegian company.”
“ According to the testing area (bonding or material delamination), we use blue and red to indicate no damage and white when there is a problem.”
In case you fancy getting into prestige repairs, note that this piece of kit will set you back the Aussie equivalent of 90,000 euros. Another challenge in the R8 was how to remove the B pillar without destroying the carbon fibre panel inside.
“We tried different methods using a complete set of heating pads and different sectioning of the repair. We found that we have to apply the pads to the surface and fix them on to apply the right pressure and head. We need enough heat to weaken the adhesive but not too much or the adhesive would overheatand harden to a to glass-like permanent bond, and could overheat other nearby materials such as aluminium which would weaken the micro structure of the material.”
The engineering teams always incorporate feedback from bodyshops who have encountered repair issues into the development of the next model. There might be damage from
an accident scenario that hadn’t been simulated that was either difficult or expensive to repair. Also in our our meeting was Markus Shultz, Head of concept development exterior and Wolfgang Dorfner whose job involves liaising with insurance companies who decide what risk bracket each car will slot into. Repair costs and how easily a car may be written off are heavily factored into this calculation.
Dorfner admits that sometimes there simply isn’t a repair solution that won’t compromise the way the car will behave
in an accident. In this case, the car will have to be written off, but they will keep experimenting to avoid this scenario.
I asked the team about their headlights which are brilliant
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September / October 2018 PAINT&PANEL 55
Audi R8 employs carbon fibre and magnesium in its body construction making repairs complex and highly specialised.