Carbon Fibre

[iamrcb]

I'm certainly no materials expert but considering the weight benefits of carbon fibre and related composites on performance AND ecomony (all sides covered) will it ever become the material of choice for cars? If "everyone" switched to carbon fibre body panels or structural parts extensively throughout all vehicles would the production costs ever come down to that of steel? or is it the case that is a fundamentally more expensive material that will always be more costly to produce, handle and work with?

[belleair302]

Two issues here. Firstly the cost of making enough carbon fibre will just not come down enough when compared to steel / aluminium and secondly carbon has a limited lifespan...it does deteriorate over time.

Plastics are the future of car manufacturing, but until the process of producing sophisticated plastics becomes more international and the processes become more cost effective in larger sizes we are stuck with steel etc.

[davepoth]

Non-structural parts will in all probability move towards composite manufacture (for example, the way bumpers are going there will be no such thing as a front wing in a couple of years, and the pedestrian safety regs make a plastic bonnet that's a bit bendy quite a good idea)

[reg_slr]

iamrcb said:

I'm certainly no materials expert but considering the weight benefits of carbon fibre and related composites on performance AND ecomony (all sides covered) will it ever become the material of choice for cars? If "everyone" switched to carbon fibre body panels or structural parts extensively throughout all vehicles would the production costs ever come down to that of steel? or is it the case that is a fundamentally more expensive material that will always be more costly to produce, handle and work with?

Carbon fibre is great at certain things but it will never replace steel/aluminium as a load bearing structure...not at any reasonable cost anyway. Another issue is that along with its relativly high production cost despite its weight advantage it is tricky to repair properly so it is unlikely to be adopted as a material of choice for body panels.

[deviant]

Doesn't it take quite a long time to produce a shaped part out of carbon fibre? I should imagine laying the material and then applying the resin could be automated but it then has to be baked for some time where a steel or aluminium body panel can just be pressed in to shape in about 2 seconds.

[flemke]

belleair302 said:

...it does deteriorate over time.

Does it?
IINM, that depends on the conditions (exposure of unpainted CF to UV). They're using a lot of it in commercial airliners these days.
If carmakers can get the expense part licked, I believe the main problem is difficulty of repair. After a certain point, it does not deform like metal, but shatters.

[kazste]

it would never be carbon neutral though would it

[JonnyVTEC]

I cant see why the comments about it not lasting come from? Its fatigue resistance and self relieving to a certain extent. There will be plenty of aerospace structures lasting decades. Cost will prevent main stream automotive use though aswell as repair implications.

kazste said:

it would never be carbon neutral though would it

Depends where you're getting the carbon from before you lock it away in strands...

Edited by JonnyVTEC on Monday 18th January 01:20

[Ravell]

JonnyVTEC said:

I cant see why the comments about it not lasting come from? Its fatigue resistance and self relieving to a certain extent.

As far as I'm aware it was mainly a problem with early carbon fiber structures, I believe the epoxi used degraded with exposure to UV light. I think the problem is less of an issue these days as Epoxis used will have much better UV resistance and UV resistant paint will be used in most cases.

[10 Pence Short]

There are alternative resins to epoxy, anyway. The main problem with using Carbon Fibre is that it's far more expensive and difficult to mass-produce and, for most vehicles, the small weight saving on non-structural parts doesn't justify the extra cost of manufacture and resultant high insurance premiums the car will have to cater for repairs.

[DJC]

It isnt actually that expensive.

Its a wee bit of a myth these days. And a very profitable myth at that.

[mat205125]

To make a bonnet skin (as an example) for a car involve slapping a sheet of metal through a few press tools, and stacking up the products that spew out at the other end. The technology is proven, it happens at room temperature, it doesn't involve and nasty chemicals or respiritory hazards, and most importantly it can be automated to spit out several hundred units per hour.

Forget what we all call "Carbon Fibre" as being the future for large volume production parts. Complex lay-ups (wet or pre-preg), and baking cycles in presurised autoclaves is unlikely to ever become cost effective for a "white good" mass market car.

As mentioned above, however, the future is in plastics like we currently use for bumpers. These may or may not involve an element of composite technology (carbon fibre is but one option .... Glass Fibre, Aramids, Cotton, Nylon, Paper etc etc etc) to add strength or stiffness in certain plains / directions.

Whoever ends up owning the patent for the process that leads to an effective mass manufacture process will be a very rich person indeed.

[10 Pence Short]

DJC said:

It isnt actually that expensive.

Its a wee bit of a myth these days. And a very profitable myth at that.

We manufacture carbon fibre sea kayaks- the materials aren't that cheap.

Not to mention it's not as easy to find people willing to work with composites once there's something to repair, if you can find a way to damage the laminate without rendering the whole panel useless, that is.

[10 Pence Short]

Just to add...

You probably be better off using some form of plastics for non-load bearing panels, anyway. You just don't need the stiffness of carbon or the strength of Aramid on a wing or door skin.

Composite shells in mass production would be an interesting concept, though.

[The Wookie]

flemke said:

I believe the main problem is difficulty of repair. After a certain point, it does not deform like metal, but shatters.

I can see it now, car enthusiasts worldwide presented with a new, affordable car that weighs hundreds of kilos less than it's predecessor despite being the same size, with supreme safety and structural stiffness... two weeks later someone on pistonheads will spectacularly crash their brand new car... three weeks later we will see the thread title:

'Had a minor bump and my car has been written off!!11!1!!!'

Followed by a 20 page thread on why CF is rubbish and why it isn't, and lo another fanboyism will emerge

Thing is, most steel cars already get written off if their shell gets tweaked, with shells using high tensile stuff none of it is particularly easy to fix anyway. The only things that get replaced are the body panels and the crash beams, which could easily be bolt on in a carbon fibre car and have better energy absorption characteristics. I'd imagine that the shell would be more resistant to damage than a steel one and that would offset any reduction in repairability.

[10 Pence Short]

If you wanted energy absorbtion, you'd be better of with aramid than carbon fibre which, as Flemke mentioned, is more liable to shatter once stressed beyond its (low) stretch point.

[BoRED S2upid]

Well the aircraft industry is making wings out of Carbon composites basically layers of carbon fibre and plastic so maybe thats an option, less carbon fibre and more plastic.

Half of my car (Classic Mini) is made out of fibreglass, I couldn't afford Carbon Fibre.

[The Wookie]

10 Pence Short said:

If you wanted energy absorbtion, you'd be better of with aramid than carbon fibre which, as Flemke mentioned, is more liable to shatter once stressed beyond its (low) stretch point.

I must admit I have no knowledge of aramids, but my understanding was that CF was very good because of its linear energy absorbtion characteristics in crush, meaning that it reduced peak acceleration over a steel structure which is usually non-linear as it buckles

Edited by The Wookie on Monday 18th January 09:13

[10 Pence Short]

The Wookie said:

10 Pence Short said:

If you wanted energy absorbtion, you'd be better of with aramid than carbon fibre which, as Flemke mentioned, is more liable to shatter once stressed beyond its (low) stretch point.

I must admit I have no knowledge of aramids, but my understanding was that CF was very good because of its linear energy absorbtion characteristics in crush, meaning that it reduced peak acceleration over a steel structure which is usually non-linear as it buckles

Edited by The Wookie on Monday 18th January 09:13

Aramid- Kevlar. Kevlar will stretch and bend more than Carbon Fibre; more impact absorbtion. Carbon is very stiff, but as a sheet will not absorb impacts as well before shattering. Along it's length it will be very, very stiff (although I wouldn't have thought that too important on a non-load bearing panel) but will not tolerate heavy impacts on the 'face' of the panel.

A couple of factories we use to put our kayaks together work for motor manufaturers producing carbon parts- it's suprising that they haven't really got facility in-house yet.

[The Wookie]

I thought Kevlar's strength was in tensile, and that it wasn't particularly stiff? I know they use it in combination with CF in racing applications, but not on its own?

I'm also surprised manufacturers haven't taken it in house. I suspect it's some sort of chicken and egg situation where no-one wants to spend the money until it's cheap enough to mass produce, and it needs to be mass produced for someone to make it cheap enough.

It takes a lot of work to make a racing tub, I can only imagine that a complex monocoque of even a boggo hatchback would be pretty difficult to reproduce in CF unless someone develops an automated process. I think probably injection moulding plastics are more likely to start appearing.

I wondered if perhaps that's what Gordon Murray's city car would be with the grandiose claims of breaking the mould (see what I did there)