[phonedrn8]

here is question about carbon fiber parts how safe are they in the a crash? what kind of testing do they stand up to.. and is there any regulation from DOT on them

[chuhsi]

curious as well...

[JFUSION]

highly unlikely that any common vendor around these forums pays the funds necessary to certify and crash test their carbon fiber parts. Outside of carbon fiber helmets I can't see any vendor of parts like Hartops, hoods, fenders, etc.... receiving DOT approval.

The common belief is that carbon fiber is stronger than steel. This may be true on a pound-for-pound basis. Carbon fiber that is layed for applications such as Indycar and F1 racecars can be engineered to be very strong and dissipate energy in crashes extremely well, but the stuff you find for sale for our vehicles tend to be lightweight parts with relatively low crash worthiness strength IMO. This is just my opinion from parts that I've seen over the years.

When you get into very high end applications I know there are companies that can engineer carbon fiber parts with great strength and crash worthiness but you won't find that with parts commonly sold for our cars. I think companies like Mugen and Spoon might have the resources to absorb the expense involved in certifying and testing parts, but I can't say that I've ever seen data provided by them on any of their parts.

I would never buy a carbon fiber part from a vendor based on it being crash-worthy, it seems that most of those parts are sold for cosmetic upgrades along with weight saving properties. Well engineered carbon fiber race parts yes, stuff being made in some guy's basement or workshop not likely. Keeping the discussion based on the typical part that you may find in the general vending community that we see on a daily basis, not million dollar parts you see in F1.

This post has been edited by JFUSION: 03 November 2010 - 11:44 PM

[4bang6]

Tensile strength Density Specific strength
Carbon fibre 3.50 1.75 2.00
Steel 1.30 7.90 0.17


F1 uses it for their entire suspension

[Moddiction]

Yeah most carbon fiber after market parts are really not strong at all!
A lot are also carbon fiber overlaying fiberglass or something.
Most parts made in carbon fiber are for looks and looks alone.

[4bang6]

it has to do with how the fiber is laid....direction wise

Carbonfibre is a non isotrope material. That means that all fibres have to point the same direction as the forcelines through the material. If this is not the case, there will be an opposite effect. To be understandable, wood is also not isotrope, aluminium and copper are for sure.
You can also notice on the table that carbon fibres are 3 times stronger and more than 4 times leighter than steel!

[Jphoa]

werd. A lot of aftermarket manufacturers lay CF over fiberglass mainly to save on cost and to provide maximum profit.

[ikeyballz]

Quote

it has to do with how the fiber is laid....direction wise

Carbonfibre is a non isotrope material. That means that all fibres have to point the same direction as the forcelines through the material. If this is not the case, there will be an opposite effect. To be understandable, wood is also not isotrope, aluminium and copper are for sure.
You can also notice on the table that carbon fibres are 3 times stronger and more than 4 times leighter than steel!

CF is stiffer, yes...but not "tougher" toughness is what counts in crashes since its how much energy it can absorb before it fails. Best way to put it... think of a rubber ball vs. a glass ball. The glass ball will definitely be stiffer and more structural...but imagine dropping it, it just shatters because its STIFF but not "tough" - it doesnt have any rubbery give to it (malleability/ductility).

[H22toF20]

Roll cages are made for a reason.

[ikeyballz]

Quote

Roll cages are made for a reason.

:iagree: but thats why they're made of chromoly steel. :cool:

[atomic]

Apart from it's actual weave and they orientation in which the weave is laid in respect to the particular part being produced most of the structural strength from CM comes from the curing process. Genuine OE high performance parts made for example for the Aerospace/Performance Automotive & Motorsport industries are Autoclaved to achieve the required structural performance.
There are other other aspects that most people don't see like for example the core of the part may have a Aluminum Honeycomb/Nomex & Phenolic resin Honeycomb/Kevlar paper and phenolic resin Honeycomb core which is then wrapped in CF and Autoclaved.

This post has been edited by atomic: 04 November 2010 - 06:21 AM

[datdude1119]

a friend of mine got in a front end collision with a wall.. everything was pushed back about a food except his carbon fiber hood...i just bent and went back to shape..pretty funny to see actually :LOL:

[Jspd]

Quote

Tensile strength Density Specific strength
Carbon fibre 3.50 1.75 2.00
Steel 1.30 7.90 0.17


F1 uses it for their entire suspension

F1 lays many layers in a clean room environment to eliminate skin oil transfer to the material that will weaken the fibers integrity and then pressure cooked. Overall a different level of quality and engineering than the parts for our cars.

Overall though it is a great material but it usually shears at the limit rather than crumple like traditional body panels :)

[Voodoo_S2K]

Quote

Roll cages are made for a reason.

[QUOTE=ikeyballz,Nov 4 2010, 02:32 AM]:iagree: but thats why they're made of chromoly steel.

[JmanS2k]

It depends on the quality of the product and how it's made. Most of the aftermarket CF parts aren't strong, they're just light and showy. I've seen cf hoods after wrecks and they basically just shatter and rip apart. When it comes to F1 and other race cars they use the best of the best CF, so that's another story.

[Zoomie]

Carbon fiber in a crash is a tricky thing. It is extremely strong in the directions it is meant to deal with forces but is very brittle and does a poor job of absorbing energy (cushioning your squishy pink parts). Most structural carbon gains crashworthyness from core materials such as honeycombed aluminum or high density foam or actual crumple zones of steal or aluminum built in. Secondly, carbon has the nasty property of fragmenting into dangerous shards. Kevlar often gets the job of containing these fragments. Keep in mind that whole carbon tubs in dedicated race cars are designed to hold together at all costs and energy is dissipated in the crash by all the accessory parts breaking off.

All that beings said, it applies only to actual engineered, and purpose built composites of OEM or aerospace quality. None of the parts you can buy aftermarket for a car live up to that (the one exception I have seen is that Challenge put a layer of kevlar inside their hardtop for fragmentation protection).

[ikeyballz]

Quote

And yet certified CF roll cages do exist.

Wow, I can honestly say I've never seen that before. That roll cage must be designed to not give at all - i bet if you were to cut a bar on it, it'd be almost a solid piece. Thats designed not with respect to energy absorption, but to WITHSTAND any impact. Designed around a totally different idea..

[suzukawoods]

I wonder how strong the genuine mugnen cf hardtop is?

[Zoomie]

^^^^
Not very, but it's light

[flyingtoaster]

Quote

it has to do with how the fiber is laid....direction wise

Carbonfibre is a non isotrope material. That means that all fibres have to point the same direction as the forcelines through the material. If this is not the case, there will be an opposite effect. To be understandable, wood is also not isotrope, aluminium and copper are for sure.
You can also notice on the table that carbon fibres are 3 times stronger and more than 4 times leighter than steel!

+1



Squeeze an egg as hard as you can between your index and thumb at the poles. It will take 30lbs. Squeeze it at the equator and it will easily break.

[whitebrad25]

there is a video i believe a vendor here posted of his CF hood being driven over by a friggin 18 wheeler...held up fine...

[ikeyballz]

Quote

there is a video i believe a vendor here posted of his CF hood being driven over by a friggin 18 wheeler...held up fine...

:banghead:

That showed the material flexing, then returning. imagine that being your roll bar - it'll flex down to where your head is, past it...(crushing your head in the process) and when you flip the car back over, it'll pop back out! leaving an unhappy crushed head.

The flexibility of cf depends highly on the matrix (resin) its in, so if you have a rubbery/weaker resin it'll flex while not breaking...but you lose the stiffness that you want from CF. To get CF thats "stiffer" than metal/that can take more stresses than metal in both tension AND compression you get highly brittle materials.

[whitebrad25]

im not refrencing the roll bar...the original post is regarding body parts....thank you.

[phonedrn8]

ahhhhhhhh good info, I was thing about changing my hood and front fenders.
GOD forbid I get into a crash how will it do to support me in the car. I like more saftey then losing 10 pounds in Fenders weight. I have a thing for saftey in this small car not a lot of give


I have seen c.f. products made for model airplanes that is practical for strength and light weight, also made in Joe Blows garage

[Olegator]

Quote

Carbon fiber in a crash is a tricky thing. It is extremely strong in the directions it is meant to deal with forces but is very brittle and does a poor job of absorbing energy (cushioning your squishy pink parts). Most structural carbon gains crashworthyness from core materials such as honeycombed aluminum or high density foam or actual crumple zones of steal or aluminum built in. Secondly, carbon has the nasty property of fragmenting into dangerous shards. Kevlar often gets the job of containing these fragments. Keep in mind that whole carbon tubs in dedicated race cars are designed to hold together at all costs and energy is dissipated in the crash by all the accessory parts breaking off.

All that beings said, it applies only to actual engineered, and purpose built composites of OEM or aerospace quality. None of the parts you can buy aftermarket for a car live up to that (the one exception I have seen is that Challenge put a layer of kevlar inside their hardtop for fragmentation protection).

Listen to him, he speaks the truth..... :tipwink: