Carbon Fibre- The In's And Out's?

CSV_LS1 · 25-03-2008, 12:29 PM

Has anyone any info on how carbon fibre reacts in an impact on a vehicle? Like those used on current day supercars? I'm interested in separating the fact from myth when it comes to this material being used on cars. Since they are used on road legal supercars, how are their construction any different to any other aftermarket piece? Is it due to their higher quantity of carbon sheeting since aftermarket pieces are usually mostly fibreglass with just a top layer of carbon to give mostly the look or is it more than that?

Thanks

ltd · 25-03-2008, 12:47 PM

The best way to look at carbon fibre in use is on the formula 1 cars. In this application, the cars are extremely resilient to damage, deformation and deflection; but conversely are extremely brittle. When you see a major accident in formula 1 you can often see little pieces blowing around like paper at the point of impact which is in fact the carbon fibre shattering.
As for V8 supercars, I'm not sure that they use carbon fibre because the cost is astronomical. In formula 1, the actual car can be worth over 30 million dollars in materials and developmental costs, yet the V8's tend to be donor domestic sedans that are modified. The formula 1 monocoque I think costs on the order of about 3 million pounds each; based on the purchase of over 20 throughout the year from the same manufacturer.

As for the carbon fibre look bonnets, I think you are right in the fibre glass with a carbon fibre inlay, as the real cost of a carbon fibre bonnet for a ford or Holden would be tens of thousands each. Not only that, what would be the point? Save maybe 10 kilos? Also, wouldn't you then legally be obliged to inform your insurer of your change to the crash/safety structure and the overall structural integrity of your vehicle necessitating an engineers certificate?
I have seen one that was metal with a carbon fibre sheet laminated to it. Looked very glossy.

CSV_LS1 · 25-03-2008, 01:10 PM

Yes very true about formula 1. At breaking point they seem to explode everywhere. Thats why i find it interesting cars like the koenigsegg and Pagani Zonda are made mostly of carbon fibre and be safe enough for the road. I imagine they are made to be flexible enough in an impact.
I'm looking at doing this as a hobby so i'm doing some initial research.

ltd · 25-03-2008, 01:38 PM

They also do it for weight savings as well as the inherent strength. As these cars are designed to hit whopping top speeds the bodies themselves are subjected to phenominal frictional forces, and frankly, metal just doesn't cut it without being extensively heavy or extensively reinforced. In these exotics, the actual cost of the car allows for considerable carbon fibre, and on a batch for the koeniggsegg of a couple of hundred the economics dictate that the use of the technology becomes viable. Another carbon fibre monolyth set to change thew world is about to take flight; the Boeing 787 or DreamLiner which has all of its fuselage and most of its wings made from carbon fibre. The reason for this is its lighter weight and ergo fuel savings, its higher strength than aluminium, its durability and its overall cost. Production facilities for this have cost well into the billions, but the aircraft at approximately 200 million US each has racked up over 800 orders, and a further 500 options. Big dollars indeed. This technology has leant itself to allowances for bigger holes for the windows, higher cabin pressure and humidity, as well as an exemplary performance in the FAA required crash test. Check it out if interested at http://www.boeing.com

4Vman · 25-03-2008, 02:03 PM

Carbon fibre can be used many ways to make parts, you need to remember the quality of the end product is largely the result of manufacturing process: infusion method, curing method and resin system employed.
You can make simple hand layed carbon fibre parts using CF matt and polyester resin and then there are vacuum infused CF parts using sophisticated resin systems and curing processes.... the 2 parts may look the same but their structural behaviour is very different.

TadKa · 25-03-2008, 02:59 PM

just on the 'myths' of carbon fibre. I'm sure I heard a commentator once going on about how carbon fibre doesn't actually split into 'shards'. No idea who or when but he was quite fierce about the term "cabon fibre shards". One of my favorite shows on fox/aus is how's its made. they had a segment on making carbon fibre racing rowing hulls. Amazing the work that goes into the layering and laminating of the sheets. big $$$ I'd say.

jabba · 25-03-2008, 03:24 PM

Quote:

Originally Posted by ltd

The best way to look at carbon fibre in use is on the formula 1 cars. In this application, the cars are extremely resilient to damage, deformation and deflection; but conversely are extremely brittle. When you see a major accident in formula 1 you can often see little pieces blowing around like paper at the point of impact which is in fact the carbon fibre shattering.
As for V8 supercars, I'm not sure that they use carbon fibre because the cost is astronomical. In formula 1, the actual car can be worth over 30 million dollars in materials and developmental costs, yet the V8's tend to be donor domestic sedans that are modified. The formula 1 monocoque I think costs on the order of about 3 million pounds each; based on the purchase of over 20 throughout the year from the same manufacturer.

As for the carbon fibre look bonnets, I think you are right in the fibre glass with a carbon fibre inlay, as the real cost of a carbon fibre bonnet for a ford or Holden would be tens of thousands each. Not only that, what would be the point? Save maybe 10 kilos? Also, wouldn't you then legally be obliged to inform your insurer of your change to the crash/safety structure and the overall structural integrity of your vehicle necessitating an engineers certificate?
I have seen one that was metal with a carbon fibre sheet laminated to it. Looked very glossy.

The V8 supercars use a Carbon Kevlar hybrid weave.... To look at the raw matting, the weave is black(Carbon) and gold(Kevlar)....The Kevlar is added into the weave to make the panels, spoilers and wings more durable. If they were just carbon fibre, we would have spoilers exploding all over the place each time they nudge the car in front...

CSV_LS1 · 25-03-2008, 03:44 PM

Quote:

Originally Posted by jabba

The V8 supercars use a Carbon Kevlar hybrid weave.... To look at the raw matting, the weave is black(Carbon) and gold(Kevlar)....The Kevlar is added into the weave to make the panels, spoilers and wings more durable. If they were just carbon fibre, we would have spoilers exploding all over the place each time they nudge the car in front...

So this kevlar-carbon mix would be whats really wanted for road use then?

xwgasaxe · 25-03-2008, 04:07 PM

As 4V stated there are lots of different manufacturing processes for Aramid fibres wtih some of the top forming techniquies called Pre Pregs.

Your best bet and this is what I did is go to a technical bookshop like Relim and get a book on this stuff,

jabba · 25-03-2008, 07:43 PM

Quote:

Originally Posted by CSV_LS1

So this kevlar-carbon mix would be whats really wanted for road use then?

Not really, the bad thing about Kevlar is it cant be finished as well as fibreglass or carbon... You end up with a fury finish just were the kevlar is in the weave, not nice and as you get with Fibreglass..... Also kevlar won't hold its shape as good a fibreglass. It will destort over a relitive short period off time.. It has been a while since I went down this path,(Looking to get a carbon bonet).... The guy who told me all about the pro's and cons, makes all the wings, spoilers and anything else fibre related for Stone Brothers Racing...

**MR_LON** · 25-03-2008, 08:00 PM

the difference between CF, Kevlar & normal fibreglass is the different properties they have, all can be made to make the same part at the same weight but basic glass doesnt have the strength, CF is a more torsionally stronger material but shatters easily in an accident. Kevlar (a synthetic fibre) is an impact resistant material hence it's major use is in racing kayaks & sculls, a carbon kevlar mix exubes both these properties but not to the highest level. fibreglass whilst stronger than metal/alloy in a strength to weight ratio has a tendancy to delaminate easily. the biggest advantage over metals is in the majority of accidents any form of fibreglass will rebound to close to its original shape, that is why they now make the front guards in the V8's out of kevlar.

jabba, kevlar can be finished just as smooth as glass or carbon if the correct process is used, it will fluff up when using a diamond blade but the normal way kevlar is cut is by laser

IDT · 26-03-2008, 02:18 AM

I thought the big problem with Kevlar and carbon fibre was its very difficult to fix? Something about it being heat pressed/sealed that once its broken it tends to delaminate/fray resulting in the need to replace entire panels.
That and the lack of after market expertise in doing repairs? imagine your local shonk trying to repair kevlar/carbon fibre holes, cracks etc.