Composite suspension components

[tipcapman]

All...

I read about the FIA intentions to ban or limit the use of carbon fiber in suspension pieces due to Ralf Schumacher's crash at indianapolis that liberated shards that punctured a bunch of tyres.

My quesion is twofold.... Kevlar is being proposed as an alternmative, what are the ramifications of the lower modulus of kevlar?

And as a followon, exactly how are the parts fabricated? I was speculating that RTM (resin transfer molding) might be the technique.

Thanks in advance...

Len

[West]

If you say Kevlar has a lower modulus, I assume of elasticity, meaning it probably isn't as stiff as carbon fiber. Maybe it has more tendency to yield rather than shatter? Kevlar is more resistant to scratching that carbon fiber tho.

[Guest]

Apossible method of producing those carbon suspension parts is
with a lost core .The Core is produced from a metal formulation with quite low melting point.these metals/blends can be formulated to melt at quite every point from 50 to 200°C ,they can be dimension/volume constant
when melting ,or they could grow or shrink with raising temps ,depending
on the necessary properties of the melting core.
You get a perfectly defined inner surface this way and the core gets melted out during or in advance of the temperature curing process of the part.
Having a additional outer mould ,you could do vakuum resin transfer moulding of course.
I think the teams use prepregs though.

[ReubenG]

Kevlar does have a higher yield stress than carbon fibres and has much higher energy absorption. The energy absorption would be pretty desirable in a crash situation. Not sure how the members are made, but what I would like to know is how they are bonded to the flexures at the ends. When last I checked there were various difficulties in bonding composites to steel, and I don't think that the flexures are made of aluminium.

[scarbs]

As I understand it, Kevlar would not be used as a (Primary) structural material, but as a wrapping to enclose the brittle carbon composites during a crash. this approach was tested by Williams on a tes tpart reducing the debris from 80% to just 4%....

Scarbs...

[Monstrobolaxa]

As I understand it, Kevlar would not be used as a (Primary) structural material, but as a wrapping to enclose the brittle carbon composites during a crash. this approach was tested by Williams on a tes tpart reducing the debris from 80% to just 4%....

Scarbs...

Yup this is also what I heard.

[tipcapman]

Gents...

Thanks for the replies. An envelope of Kevlar sounds like an easy change with no significant effect on structure or manufacturing method.

I have experience with Kevlar, and I think it is overrated in some respects, but sounds like it would function well in this application.

L

[Guest]

i´d say Dyneema is far superior in retaining debris of shattered suspension or aero parts.Dyneema is a fabric woven of Polyethylen(HPPE)
fibres.
The only problem is it is less temp resistant and would not work on the top rear suspension possible.It fails at 144-152°C

The advantage of dyneema is it does not attract wateringress into the part,is highly abrasion resistant,has high impact strength and is lighter than kevlar.It is the material used for armouring and protective clothing nowadays.
Kevlar soaks water and looses its stability very fast as some companys have learned the hard way.

Bonding is a very high skill thing you have to edge the surfaces to prepare the metal surfaces for bonding.whereas the composite bonding surface is finished of with peeloff fabrik .This last layer gets peeled off directly before bonding and offers perfect bonding surface properties.
Edging of the metal parts with acids or in the case of magnesium sodiumhydroxide after a thorough texture has been sanded on the bonding surface will do the trick.
Interestingly Titanium is quite easy to bond ,sanding and degreasing with acetone does the trick,whereas Aluminium is quite tricky.

[tipcapman]

Bonding is a very high skill thing you have to edge the surfaces to prepare the metal surfaces for bonding.whereas the composite bonding surface is finished of with peeloff fabrik .This last layer gets peeled off directly before bonding and offers perfect bonding surface properties.
Edging of the metal parts with acids or in the case of magnesium sodiumhydroxide after a thorough texture has been sanded on the bonding surface will do the trick.
Interestingly Titanium is quite easy to bond ,sanding and degreasing with acetone does the trick,whereas Aluminium is quite tricky.

Thanks for the input.

I agree that structural bonding is indeed very tricky, but my company has found that bonding of aluminum is far easier than titanium, even with very elaborate surface preparation.

But there are constantly new developments, and we are always looking for easier ways to do our jobs.

Regards...

Len

[Monstrobolaxa]

Well I wasn't going to coment the guests post....cause it seems that he knows what he is talking about....but I also had the impression (like tipcapman) that titanium bonding if far more dificult then aluminium! I read it somewhere in an interview with Neil Oatley that Mclaren was having development problems of wishbones and some gearbox casing parts because the bonding process takes them almost 3 weeks! And that aluminium takes around a week or so....so when the stock is low on titanium/composite parts the team tends to panic a little because it takes a whole long time to make them.

[Guest]

i have to confess my bonding expertise does not cover titanium structuralbonds.
so maybe i was just lucky yet....I´ve heard about some companies doing
very elaborate surface preparation of titanium.
And it would make sense ,as the surface instantly oxydises when exposed to air. that´s why I did all titanium bonding in my argon gas chamber (usually used for tig welding)it worked fine.