carbon fibre rigidity

[KnifeEdge_2K1]

hmm carbon fibre is really rigid and resists torsional stress really well ... till it reaches the limit, then it just breaks apart right? as we all see in f1 races usually this means complete destruction of the wing, suspension arms, everything ... so what about the road cars that have carbon fibre (both oem c/f and aftermarket ones)

im guessing the carbon fibre hull for performance cars are extra reinforced while the outer shell is designed with regular crumple zones ... well explosion zones are more like it, but with aftermarket parts if for example the c/f bonnet can take the amount of stress, wont it rip out of its mounts and kinda jam itself into the cabin ??

that'd be scary, decapitated by your own carbon fibre hood, eeshh

[Cyco]

If its layed up is designed by someone who know what they are doing then you will often find Arimid (Kevlar) in areas that they want the crumple to occur in.

The arimid fibres have a much greater elongation than the carbon fibres so it will hold together better in event of an impact.

For crumple zones a core (nomex honeycomb, foam) is often used in the lay up as an extra energy absorbing material as it crushes.

[2ndclasscitizen]

yeah, CF is really strong, its just that instead of bending like steel, or other metals, its just cracks and fragments into splinters, which is why in F1 races after crashes there are heaps of flats

[KELSA]

If its layed up is designed by someone who know what they are doing then you will often find Arimid (Kevlar) in areas that they want the crumple to occur in.


yeah they use carbon kevlar, which is carbon and kevlar cross pattern each other, and under resein, and depends on how you tension them, it is very flexable. they usually have a layer of glass on top of these parts so that 1. glass can help absorbes the impact, but most importantly it looks better on paint work as the nylon (kevlar) doesn't suck paint very well, and in a 40 degree heat you'll see the kevlar patten quite noticeablly.




CF is really strong, its just that instead of bending like steel, or other metals, its just cracks and fragments into splinters, which is why in F1 races after crashes there are heaps of flats

somewhat not true, you can pre-tension the carbon fibre, and you can make it from flexible to extrodenaryly stiff. some of the f1 parts are very flexible and they are straight carbon, e.g. mirrors, front wing flaps, they can be bent so that aerodynamics are able to change depending on speed.

[KnifeEdge_2K1]

thats torsional rigidity, what we're talking about is when its past its max tension, regular steel or metal just bends and permanently deforms, carbon fibre cracks

[ZemoButts]

this is probably a stupid question
but can u weld on carbon fiber???

[Matra et Alpine]

The kind of welding you're thinking of NO.

Gas and arc welding is for metal.

you CAN however BOND to the gel/plastic polyumers the C/F is mixed in and to some comapnies that is "welding" and to others it's bonding - basically it's a glue and it's how it affects the gel/polymer that makes it different.

As I suspected you're thinkign of welding with a welding torch and arc then it is a definite NO. IF there was metal nearby to striek up the arc the heat woudl instantly melt the gel/polymer :)

[Cyco]

If its layed up is designed by someone who know what they are doing then you will often find Arimid (Kevlar) in areas that they want the crumple to occur in.




yeah they use carbon kevlar, which is carbon and kevlar cross pattern each other, and under resein, and depends on how you tension them, it is very flexable. they usually have a layer of glass on top of these parts so that 1. glass can help absorbes the impact, but most importantly it looks better on paint work as the nylon (kevlar) doesn't suck paint very well, and in a 40 degree heat you'll see the kevlar patten quite noticeablly.

There are Carbon/Kevlar weaves, but they are more often used as a decrotive finish, than as a structural element (not that they are not- they can be quite useful). It is usually easier to use multipul layers of each material as the drape properties are more consistant, and the lay-up is easier to optimise.

Nylon and Arimid (of which Kevlar is a DuPont tm) are not the same, and their properties are quite different. There is no structural use of nylon in any high preformance composite part (to my knoweledge). Nylon is sometimes used in the outer layer (Nylon weave or Nylon/Carbon) as it can be coloured for effect.

Glass fibre tends only to be used on parts where the mould quality is poor, and sanding will be required to get a decent surface finish before painting. The patten that can be seen is due to a low resin/fibre mix and the 'divots' between the weave intersections.


thats torsional rigidity, what we're talking about is when its past its max tension, regular steel or metal just bends and permanently deforms, carbon fibre cracks

The carbon itself tends to only crack when there is an existing failure of the resin matrix (usually from impact, if designed correctly). The failure in matrix can cause the carbon to be pointed loaded as the resin is used to transfer the forces between the different fibres.

[viper dude]

does anyone really know what the breaking point is i know they put it in indy and f1 cars to inclose the driver because one man lost his legs in a crash but after they put that in a nother person was hit side on at idk 150mph and it didn't break

[Cyco]

does anyone really know what the breaking point is

Yes


i know they put it in indy and f1 cars to inclose the driver because one man lost his legs in a crash but after they put that in a nother person was hit side on at idk 150mph and it didn't break

Building a part to withstand impacts is easy, building a part to withstand all racing accidents is impossible if you want the driver to be able to see out and have the part weight less than several hundred kilograms.