See the failure point? It's all along the full cross-section of the mounting bracket. One can deduce from looking at the poor composite construction that the failure is due to weak material. You can clearly see some delamination on the 2nd picture, a thin 1 or 2 layer of CF and the foam (or whatever they used) core have separated. One cannot make assumptions as to the procedure used in manufacturing, but if CF parts are not properly vacuum bagged and the epoxy is not properly mixed, your parts end up weak.

When a car goes around the track, the airstream and airfoil will interact at different angles, not just head on. Wings and their mounting hardware need to be made to withstand forces from all directions. Resulting forces from the airfoil's downforce is not downwards all the time. There are resulting forces at various angles as the car goes thru corners. That's why critical parts like mounting brackets need to be properly designed.

It's not that difficult to design/make a bracket that can withstand sustained forces in any direction. Just give it adequate x-sectional area considering the material strength properties and design it for a target speed, say 250mph, and account for airfoil loads. If you know the airfoil load from your chord design and wing span, then you can calculate how much force the wing can generate. You then design necessary bracket strength to keep it from breaking off. Of course, execution in manufacturing CF components also has to be done right

 

believe it or not that's no core, it's solid carbon all the way through. I'm pretty sure in both my case and the Element Tuning car that our mounts both failed first. I'd love to think otherwise but I know when I redesign mine I will be doing FEA and wind tunnel testing before I hit the track again. I still have the other piece of the mount that broke off and if I put one end in a vice and push/pull as hard as I can on the other I cannot even phase it.

 

Wow! if it's full CF cross-section, then the manufacturing procedure is quite poor then.
The only way to get that delamination seen there in the pic is from poor epoxy infusion into the fiber.
When I worked in my school's solar powered car project back in 1995, we were careful to mix the epoxy in the specified ratios, then lay the CF cloth layers, spread the epoxy evenly, then use bleeder/peel cloths, and vacuum bag the parts overnight to allow for curing. Parts made like that are very strong and light, very close to prepeg parts.
Prepreg material, otherwise known in tuner world as "dry carbon" is better but not by a lot and it's really costly since you need an autoclave.
We even made wheel centers from CF and balsa wood core. The car weighed around 1200 ~1400 lbs and was test driven at up to 70 mph at GM's bumpy proving grounds in Mesa, AZ for long periods of time. We drove the car for about 1000 miles during the SunRayce in '97 and never had any delamination as seen in that wing bracket.

Usually when you have CF fractures you will see jagged edges, due to the way CF fails once its ultimate strength is exceeded. In the pic you can see the "hairy" remnants of the cloth. That happens when a CF part is not made/cured properly in the mold. The color of the center portion in the pic led me to believe it was some type of core, also Phil stated it was some type of foam-based core.
Could it be the epoxy-infused foam appears to be solid CF?
It would take too much CF cloth material to make the wing pylon of solid CF, considering most CF cloth is about 1-2mm thick, and no company in their right savvy business mind would use that much CF!
A properly designed composite part can have a foam, balsa wood, aluminum honeycomb core and fewer layers of CF and it would be just as strong as a solid CF part but considerably lighter. Remember that the most strength is realized at the outer edge of a cross-section and the middle portion sees lesser stress.

Unfortunately, it's the nature of the tuner business, cheaper parts sell more. Consumers would opt buying a $300 wing over a $1200 wing. For the majority the cheaper wing suffices. When pushed to their limits as in these failures, it's when we realize the importance of proper material/manufacturing.

 

I'm 100% sure it's solid carbon, looks like 20-25 layers (i'm going blind trying to count). It looks as though they were formed under pressure and pretty well manufactured honestly. I think the big design flaw is the complete lack of any radius at the corners. I couldn't believe there was no core either.

 

I saw this video on another thread. the driver goes thru a highspeed corner without the wing and has no problem with it/.

this crash has almost nothing to do w/ the lost wing and a ton to do with driver talent.

 

[media]http://www.youtube.com/watch?v=_LnmD7kxHUw [/media]&feature=player_embedded

wing breaks off at 0:26 and he immediately goes thru a high speed left hander without any problem using the same amount of steering input as he does on the corner he spins.

You can see and hear him lift off when he turns too.

Glad he's ok, but that crash is WAY more driver induced than wing induced imo.

 

I tend to agree, when I lost my wing my car definitely got looser but the bottom line is conditions change and that includes the car. Losing a wing that produces 200ish pounds of downforce might be the difference between making a clean turn vs a little bit of oversteer and maybe even going off the track a bit but totally losing it like that... I doubt it.

 

[QUOTE=krazik,Apr 14 2010, 01:29 PM] I saw this video on another thread.

 

^Could be both.

Great driver/setup loses wing, driver is able to adjust for one corner but not the next. Everyone makes mistakes.

If my wing broke off I would partially blame the wing and myself for not catching it.

 

[QUOTE=EngineerX,Apr 14 2010, 02:17 PM] So Phil, who has consistently run just under 2:00 at VIR full and has won/ placed top on time attack competition crashed due to his poor driving?

So an aerodynamic part that's generating 100+ ~ 200+ lbs? of downforce breaks off and it doesn't have anything to do with tire/road grip at the rear and the crash?