I'm sure this is a dumb question, but all I hear about these days is carbon fiber this, carbon fiber that. What's the big fuss about carbon fiber? What is it? What do parts made of carbon fiber accomplish that other parts don't? Is it all just about weight?

Thanks, I just finally decided to ask.

Alright, here is my bit on carbon fiber. I'm not an engineer, but I've worked with and around carbon fiber for many years.

The advantages of carbon fiber all depend on its application.

It's tensile strength, tensile modulus and specific strength are very high, while it's density and weight are low. This means you can construct a product with similar strength to say steel, but at a much lower weight. Carbon fiber also has a long fatigue life. This means it can be flexed over and over many times without loss of strength. As long as you don't bend the material to it's breaking point, it will last a long time.

Carbon fiber also helps to dampen vibration. This is the main reason you see the product used in high-end bicycles. It provides a very comfortable ride while still being light and efficient.

Carbon fiber can be manipulated to fit the application. Basically, you can lay the threads of fiber in whatever direction you like. You can make the material very stiff in one direction, but have a bit of compliance in another.

And lastly, and most important for many people, it looks cool. Most carbon fiber used in things like cars add a final layer of carbon fiber with the fibers weaved in a pattern that is very visually appealing. If you were to see the layers below, it would be much less visually appealing with a more random pattern. Beware though, many items that look like carbon fiber are not. Often products will just have a carbon wrap that does little more than look cool.

I forgot to touch on what carbon fiber is. Actually, it can be a lot of things. What most people know as "carbon fiber" is a mix of carbon fiber strands and some sort of resin to hold it all together. There are many different grades of carbon fiber and also hybrid mixes, with glass and carbon fiber just one example.

is it similar to fiberglass require bating for strengtha dn shape?

bottom line
carbon fiber is light and strong as hell

and looks cool IMO

Wow, thanks for the very helpful info, mamccubbin!

Of course, the other important factor is that it's not cheap. The fibres themselves are very expensive to make - requires a lot of energy - and once made, difficult to form. Even the mighty Boeing had trouble with this when trying to mould the wing surfaces for their JSF (Joint Strike Fighter) candidate.

Another important aspect of carbon fibers is that they are weak in compression. Think of it like silk. If you grab a dozen strands of silk and pull on them, they are very hard to break. However, you couldn't balance a feather on top of a silk strand - it buckles under its own weight.

This is similar to carbon fibers. They are extremely strong in tension, but much much weaker in compression. This does place limits on its use, as any design much ensure that the fibres are not bearing forces in compression.

Incidentally concrete is the exact opposite - extremely strong in compression, very weak in tension. All the bridges and buildings you see concrete used in are designed such that the concrete is always in compression. Otherwise things would be falling down all over the place :)

Your friendly neighbourhood materials scientist & engineer :)

its not cheap but you get what you pay for

my civic had carbon fiber sterling wheel, pedals, shift, ebrake , dashkit , rearview mirror

that stuff gets costy quick

Originally posted by loco4rx8
What's the big fuss about carbon fiber?
This might stir up some flame-bait, but the big fuss regarding CF in the import scene is a) it looks cool and b) "real racers" use it.

"Real racers" use it because it offers a performance value (high strength to weight ratio means less weight) and could care less about looks.

The flame-bait part is street drivers do things like CF covered interior trim because it looks cool, even though there is no performance advantage and in fact adds (an admittedly small amount of) weight. Rear wings on a front-wheel drive car is the epitome of "ricer" imagery where people do something that looks like a performance enhancement but in fact hurts performance.

Saying you want CF (or anything else for that matter) just for looks is fine, but please don't confuse looks with performance.
________
Lovely Wendie (http://www.lovelywendie99.com/)

Originally posted by aussie77
Your friendly neighbourhood materials scientist & engineer :) Damn! You beat me to it! Friendly neighborhood mechanical/materials engineer here :D

Originally posted by PUR NRG
This might stir up some flame-bait, but the big fuss regarding CF in the import scene is a) it looks cool and b) "real racers" use it.

"Real racers" use it because it offers a performance value (high strength to weight ratio means less weight) and could care less about looks.

The flame-bait part is street drivers do things like CF covered interior trim because it looks cool, even though there is no performance advantage and in fact adds (an admittedly small amount of) weight. Rear wings on a front-wheel drive car is the epitome of "ricer" imagery where people do something that looks like a performance enhancement but in fact hurts performance.

Saying you want CF (or anything else for that matter) just for looks is fine, but please don't confuse looks with performance.

You are correct. People would be a lot better off spending there money on something other than carbon fiber. You'd be a lot better off with lighter wheels than a carbon fiber interior.

Originally posted by mamccubbin
You are correct. People would be a lot better off spending there money on something other than carbon fiber. You'd be a lot better off with lighter wheels than a carbon fiber interior.


thats your thoughts

I disagree

Originally posted by mikeb
thats your thoughts

I disagree

Not to start a war here, but why do you disagree? Not from an appearance standpoint, but for performance.

Originally posted by aussie77
Incidentally concrete is the exact opposite - extremely strong in compression, very weak in tension. All the bridges and buildings you see concrete used in are designed such that the concrete is always in compression. Otherwise things would be falling down all over the place :)

Your friendly neighbourhood materials scientist & engineer :) Reinforcement in concrete, be it steel "rebar" (reinforcement bars) or fiber reinforcement (similar to the tensile properties of carbon fiber), add tensile strength to concrete structures - so that concrete structures can withstand tensile stresses. Note that I said "concrete structures", not the actual concrete.

Concrete bridge spans, parking deck floor sections & other simple beam-type structures which must support weight in mid-span, must be reinforced on the bottom side of their thickness which is in tension. Usually, almost always, these are pre-fabricated off-site because they are "pre-stressed" for lighter section size & weight. At the fabricating shop, the steel rebar in the concrete, in the lower parts of the thickness, is actually being pulled in tension while the concrete hardens & cures. When the tension is removed, the rebar can't relax back to their normal state because they are trapped now in the cured concrete. The internal reactive stresses of this composite structure actually pre-stresses the concrete opposite that of its intended live loading. The bottom side of the concrete thickness will be in compression. So, live loads placed on the structure causes the bottom side to go from compression - to zero stress - to a much less amount of tension as the amount of live load increases.

Coors brewing company was trying to figure out what to do with all of the rice husks they accumulate. Somebody decided to incinerate them & check out what was left. The remaining "whiskers" are now being marketed as reinforcing fiber for ceramics.

Been trying to be an engineer myself for over 32 years now... :D

Originally posted by mikeb
thats your thoughts

I disagree

disagree with what?

er, as far i can see here. all these posts are more or less entirely accurate as far as the performance value of CF goes.

Originally posted by mamccubbin
You are correct. People would be a lot better off spending there money on something other than carbon fiber. You'd be a lot better off with lighter wheels than a carbon fiber interior.

This is what I disagree with

Originally posted by mamccubbin
You are correct. People would be a lot better off spending there money on something other than carbon fiber. You'd be a lot better off with lighter wheels than a carbon fiber interior.

Do exactly what you want and don't worry about it. If people (people like me) are critical over your choices - accept that they don't like what you've done.

BUT do things because you want ti, not for the ME TOO factor.

Originally posted by mamccubbin
You are correct. People would be a lot better off spending there money on something other than carbon fiber. You'd be a lot better off with lighter wheels than a carbon fiber interior. Lighter wheels are a definite plus, and worth far more in performance terms than CF interior parts. In fact, you can buy carbon fiber wheels from Dymag. They're even lighter than Magnesium wheels, and probably stiffer and stronger too. The ones shown here are motorcycle wheels, but Dymag does make car wheels. Be prepared to spend a LOT of money for the privilige. Street Fighters USA (http://www.streetfighters-usa.com/dymag.htm)

If you planning of doing carbonfiber on your car do a little but dont do to much.

well carbon fiber has been bastardized by companies like ViS and Fiber Images. Having 1 layer of carbon fiber and 5 or 6 layers of fiberglass is not weight savings. The hoods we have been making for years are for race applications and they do cost about $1,200 but they also only weight 3.4lbs (rx7 hood) They have the full structure as well not just a skin. Place like ViS use inferior products and claim to be the best because the consumer doesn't know any better. I would never pay $400 for a hood that is 80% fiberglass and is made with polyester resin and that was never post cured and popped out of the mold in several hours because they use 3 times more catalyst they are supposed to to make it kick faster. You also don't have to have it autoclaved to be a good carbon piece. They have vinylester Pre-preg that bakes at 200 degrees and is twice as strong as epoxy pre-preg and for cheaper. Plus epoxy resins are not made for heat anyway. I would not be suprised to see engine covers coming out for $125-$150 that are vinylester pre-preg and more heat resistant. Even wet-layups have been more advanced with the use of vaccum infusion and closed air molding. You can almost not completely but close duplicate a epoxy pre-preg piece in structure integrity and resin content with closed molding for about 3/4's the price.

In the case of the driveshaft on the 6-speed RX-8, carbon fiber is definitely all about weight & performance (the strength of steel at a fraction of the weight).

I smashed my hood a few weeks ago and I am concidering replacing with CF. The OEM hood itself is about $500 and the paint would be i little over $100.

So, I would like to get a CF hood for about $600 or so [I don't mind a little more]. I DON"T want a cheap carbon look hood. Is it reralistice to get a quality product for $600, or is that the price of a cheap CF hood?

I did find (2) CF hoods for about 600, I just don't know if they are well constructed.