Composite Flexures

[StockR]

Hi,

I'm as you can tell new to this forum. I would like to know more about composite flexures and their uses + designs as part of automotive suspension.

Can anyone give me an idea of how they work, design aspects, analysis, etc.? Or any links to articles or resources (online or print) would be great as well.

I have tried google and maybe these designs are too new? I can't find much on it.

TIA

 

[GregLocock]

I've never seen one used except on F1 cars. I doubt they would have sufficient articulation for any cars other than ground effect circuit cars.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Fabrico]

There are common suspension springs on production cars, usually transverse, that are often referred to as being composite. But nearly all are fiberglass.

 

[patprimmer]

I think Chevrolet used a transverse fibreglass spring in the Corvette around the late 70s. I am not very sure on the dates, or for how long.

Regards

eng-tips, by professional engineers for professional engineers
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[Fabrico]

Many GM cars use of have used transverse fiberglass leaf springs at one time or another, and for several years.

 

[patprimmer]

Maybe I remember the Corvette as it is a high profile example, and because I really liked Corvettes, especially around the mid 60s era.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[GregLocock]

I'm pretty sure Corvette is still transverse glass fibre leaf spring/ lateral arm.

http://20car.com/specials/spec26.htm

Sorry, I assumed the OP was after the arm to body mounts, which are small beams made of something or other that often last for a whole race.





Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Fabrico]

Corvettes not only still have them in the rear, but they've been using them in the front suspension for a few years. Chevrolet still calls them "composite". I think Ferrari, Volvo and others use them too.

http://www.corvettemuseum.com/specs/2006/index.shtml

I'm still not sure what the OP was referring to.

 

[BioMax]

I believe that some mid 90's Astro vans had composite leafs.

I'm not sure how that will help though.

 

[leaftye]

I believe most commercial GM trucks use composite springs too. About the only things I can add is that the spring use unidirectional fibers, and there's a popular aftermarket spring company that's starting to make replacement springs....Eibach I think, which would make them the second aftermarket manufacturer.

 

[LUBolton]

Formula 1 uses flexures, but they're not composite. They're made from titanium and they can get away with it because they have so little suspension travel. (most of it is in their tires)

Composite flexures are very uncommon for SLA suspensions. My FSAE team designed and built them into the a-arms on all four corners of our 2006 car. To our knowledge we are the only people to ever do this. The flexures were carbon fiber along with the entire a-arm. We used carbon as opposed to titanium because we are required to design for 2" of total wheel travel. Titanium can't deal with this type of strain to my knowledge.

Anyways, to answer your question. Design issues are as follows:
1. Stiffness- reduce it so that it does not add additional stiffness to your suspension.
2. Buckling- main failure mode of the flexure aka how it will break in actual use.
3. Compressive failure of skin due to high flex angles.
4. Fatigue- theoretically composites have infinite fatigue however we know that this isn't always the case in practice due to inconsistencies, scratches, cracks, etc.

Aaron Cassebeer
2007 Lehigh FSAE Team Leader

 

[rpmag]

could you use a longer flexure of thin flat spring steel?

 

[ubrben]

I'm fairly sure some teams have used carbon flexures in F1.

Jordan Grand Prix did use spring steel flexures in 1993 I believe.

Ben

 

[Fabrico]

The F1 Ferrari very recently used a composite lower control arm that was one piece from wheel to wheel, and was the flexure. It may still be under their current car. However, it did have a titanium spar inside of it.

 

[GregLocock]

rpmmag, problem is likely to be buckling under axial compression when articulated, and vertical compliance.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.