Just looking at MB's Citroen Lekki track car concept post and was wondering what such a car would cost if it hit production, then they mention a carbon composite chassis/body panels etc which instantly triggered thoughts of 'silly money'

Just why is Carbon Fibre still so expensive? After all its not as if Carbon is a rare element here on planet Earth.

Clearly Carbon Fibre is a material that we'll want to use more and more of in the future with its properties of light weight and extreme rigidity it's the perfect material for many an application; so why isnt there more of it being manufactured now in such a way that it lowers the cost; or is it the case that this simply isnt possible due to the costs being in the actual forming process of a part as opposed to the actual material itself?

(I'll just say that I know little to nothing about the use of materials in engineering so may be overlooking the blindingly obvious)

 

Well, Lamborghini have co developed something called 'Forged Carbon' which offers up 95% of traditional CF strength/weights with a fraction of the costs.

Unfortunately, Carbon Firbe as it stands is an arse to work with.

Infact, management for Airbus wanted a passenger plane built completely from composites. The eingeers went away and came back with one that not only took longer to build and was more expensive, but also HEAVIER!!

Unlike with metals, you can't just go an drill holes in it without massively compromising integrity.

You need moulds that need to be vacuum baged and then pressure baked which takes an immense amount of time.

All of this adds up to silly costs compared to sheet metal.

Plastics are the future of car construction.

 

Today i was talking to a guru of model aircraft.

Apparently propellers made of carbon are heavier than the ones made of wood.

A Honda S2000 bonnet made from carbon weighs more than one made from aluminium.

So apart from higher prices we are looking at equivalent or even higher weight.

Does it make sense?

 

That is not strictly true.

The cheapo 'wet' carbon fibre bonnets are heavier but the more expensive 'dry' carbon bonnets made by the likes of Mugen, ASM and Amuse are lighter.

Chris.

 

Wet and dry?



We are on about carbon fibre here, not sandpaper.

I have no doubt in believing that some CF bonnets are heavier than others, but that will be down to the quality of fibre, the forming process, and the fact that the sttructure won't be made from carbon fibre.

'Dry' carbon is JDM tite y0 and nothing more.

 

^^^


Do some research, nothing to do with JDM y0

Wet and dry refer to the two main methods of creating carbon fibre parts.

Wet lay up is where the resin is spread into the mold before the CF material is applied.

Dry lay up is where the CF material is already impregnated with resin--sometimes called prepreg. This method can generally produce lighter parts than wet lay up.

Chris.

 

From a mate who works in Carbon Fibre composites research. (We had a similar conversation the other week)

"Its because it costs so much to convert the carbon into its fibre form, and then it costs a lot to store it, and finally costs a lot to manufacture parts from it. Due to the cure cycles and the price of the epoxies used in the carbon fibre composites. The epoxies bond the carbon fibres together, and they are not cheap!"

 

and "composites"

One problem with CF that no one talks about much is how easy it is to delaminate it when it is "knocked" in the wrong direction.
There was a very interesting program on over the weekend looking at the issue of Airbus tails falling off
It showed a piece of CF that had a hammer knock, it looked fine on the out side but ultrasound showed microsopic damage in the weave to the fibres they then showed how it would delaminate around that area after flexing.
It is also a know issue in F1 cars.

Whilst it has benefits for weight and strength in certain directions it does not lend itself to mass production in the required quality. Hence it is expensive.

BTW composites don't always have CF in them

 

Having made CF from wet and dry as you want to call it, there are benefits to both depending on the application.

Pre-preg is generally easier to mould, but more expensive.

The bare carbon firbe I used was stored in a big roll and looked/felt like wind breaker material.

Process for both was essentially the same in that you applied fibre to mould, added resin sheet where appropriate, and then applied more fibre at angle for unilateral strengths if required. All were then vacuum bagged and autoclaved.

However, 'Wet/dry' won't mean heavier/lighter parts - there is much more to it than that.

And try speaking about Wet/Dry carbon to someone who works in the industry - they will laugh at you in the same way if you speak to a pilot about using the 'Afterburner'

Like I said - JDM tite y0.

 

The problem with CF also is that it isn't a longlife product when everyday use like a car is concerned. It's liable to delamination and needs regular ultrasonic inspection (this applies to F1 and aircraft parts). If a vehicle that was made purely from composite materials had any sort of excursion off the road it would take the battering but would be almost useless to put back on the road without major structural repair hence why only supercars tend to be made of the stuff.