Is a carbon roll cage impossible?

[ThomasSoerensen]

The benefits of weight savings of a carbon roll cage are obvious.

But is is really impossible to make it so it functions like a tradisional steel one?

Are the current FIA approved roll cages steel due to regulations or due to superior performance?

A carbon roll cage must be possible.

What do you guys think/know?

[mmm-five]

I think the problem with carbon-fibre is that it is only strong in one direction, so if it has a side impact on an upright it will collapse. A steel one will take some punishment from all angles. I suppose you could try titanium.

[J4CKO]

My understanding is that it its strength isn't uniform and in the wrong direction its relatively brittle and the right one very strong but I suppose anything is possible. Not sure what its like to make tubes from and joining it once in a car may be an issue, its not like you can weld it and when the carbon tubs are made its done in a big oven under massive pressure.

[Petrolhead_Rich]

massive cost of construction, fitting, maintenance etc

so sir the steel rollcage at £400 or the Carbon Fibre one at £4,000,000?

[Bullett]

I would guess, not possible if it hasn't been done already.

Secondly, I think CF is designed to be strong in one direction only. So in suspension for example it goes up/down all day long but hit it from the side = broken suspension.

Thirdly, doesn't cf shatter when it breaks?

[ThomasSoerensen]

I know your way of thinking.

But how do they make the carbon monocoques then? They shuold be able to take impact from many directions, right?

[rhinochopig]

Carbon tubes suffer when punctured/dented - think how strong a toilet roll is if you push from the open ends and how easily it folds if you dent it. A carbon-tube cage wouldn't work.

[RobM77]

I can think of a couple of reasons why not:

Most cages that I've seen in race cars are welded in, so the fitting may be tricky.

Many cages need customising to fit, which obviously isn't possible with carbon fibre, which I believe needs to be formed in the finished size and shape?

[IanMorewood]

Rolling your going to exert lots of forces into the cage from all different angles including across the grain of the carbon possibly leading to a catastrophic failure.

[thinfourth2]

Its posible but i don't think we understand carbon well enough yet to engineer it to take a multiple hits from different directions

[T.K]

Oakley built a carbon fibre cage for the 997 GT3. But they were complete jokers.

Anyway, titanium.

[ThomasSoerensen]

And you cannot put the different layers of the carbon weave in different directions and thereby make it stronger in more directions?

I know basically nothing about this but I find interesting that it is impossible. Someone should be able to simulate the forces in a computer in order to find the optimal way of construction.

[RobM77]

Obviously F3 (or FRenault now?) upwards have carbon tubs now, and they're often rebuilt after accidents. I don't know much about running carbon cars though, but they might not need much of a knock to need a new tub - not something that a club racer on a budget would be able to do!

[IanMorewood]

ThomasSoerensen said:

And you cannot put the different layers of the carbon weave in different directions and thereby make it stronger in more directions?

Woven CF tubes as used in sports equipment tends to fail spectacularly when impacted against anything solid, you wouldn’t want that to happen if the next thing stopping the roof/floor/head interface is your head.

[ThomasSoerensen]

If not of the woven type then what type are the constructions on monocoques then?

I agree completely that a structure designed to protect should not shatter on first impact.

Don't they make car and bike helmets of CF these days?

They should be able to take a bang and still protect.

Edited by ThomasSoerensen on Friday 17th December 15:34

[BarnatosGhost]

ThomasSoerensen said:

And you cannot put the different layers of the carbon weave in different directions and thereby make it stronger in more directions?

I know basically nothing about this but I find interesting that it is impossible. Someone should be able to simulate the forces in a computer in order to find the optimal way of construction.

Not impossible, just not as good as the popular solution. You could make it out of balsa wood if weight was the primary consideration. You could make it from cheese if flavour was important.

Every material has different compromises, and they are weighted differently for each application. Selecting the right one is just a question of which compromises leave you better-off overall.

[R26Andy]

Just a few of my ill thought out friday afternoon observations for the topic.....

Steel was choosen because it suited the requirements of the design and manufacture of a roll change (cheap, easy to manufacture and material properties suited). Trying to retro fit another material with different properties (square peg in round hole) to as design doesnt normally work either in terms of ability to manufacture, functionality or cost.

In order to make best use of a materials key properties (i.e. lightness) the design should be speicifcally applied to that material or the material specifically choosen for the design as its properties suit the purpose. I.e a monocoque design is used when working with carbon fibre and the cockpit is shaped as such it doesnt need a roll cage.

Oh and I just want to add that during my days as a formula student engineer at university I looked into creating a carbon fibre space frame chassis for our single seater car we designed and built but had the same issue.

Edited by R26Andy on Friday 17th December 15:47

[ThomasSoerensen]

Ok so it seems that a cage mage from pipes is no good for CF.

Maybe a kind of inner skin inside the driver compartment could be made from CF and protect well, and be more in line with CFs properties?

But I guess that is a different thread.

[IanMorewood]

ThomasSoerensen said:

If not of the woven type then what type are the constructions on monocoques then?

I agree completely that a structure designed to protect should not shatter on first impact.

Don't they make car and bike helmets of CF these days?

They should be able to take a bang and still protect.

Edited by ThomasSoerensen on Friday 17th December 15:34

You can reduce the chance of shattering/splitting of course by using composite materials and increasing the thickness and diameter (increasing diameter increases weight dramatically) of the tubing. The downside then is weight/size and the costs of production, its highly likely that studies have been undertaken and an alternative material (such as titanium if your rich enough, or steel if your not) proved more practical.

It like would you use magnesium alloy to make body panels? Sure why not, its light (lighter than aluminium), doesn’t corrode like steel and can be formed into many different shapes and strengths. Only small downside is that you could potentially be sat in a fire trap.

[busta]

If your have an accident and roll 4 times with a steel cage, however bent and battered the cage becomes with each impact, it will still offer a good proportion of it's original strength in each consecutive roll.

A carbon fibre cage would offer excellent strength in the first impact, but because it is brittle and has a composite structure it would be little more that a bucket of shards by the time you hit the ground the 4th time, which would offer much protection.

Also, no matter how much you bend and bow a bit of steel pipe, it's very difficult to make a sharp edge (until it shears of course). Carbon fibre would be quite lethal in that respect.

That's how I see it anyway.