Fiberglass vs. Carbon Fiber

[MNBoxster]

Hi,

The term Carbon Fiber encompasses many different materials and processes - too many to discuss in length here.

Most CF on the Aftermarket is not pure CF, but (CRP) Carbon Reinforced Plastic. The plastic is most often epoxy, but other plastics, such as polyester, vinyl ester or nylon, are also used. Some composites contain both carbon fiber and fiberglass reinforcement. Less commonly, the term graphite-reinforced plastic is also used.

One way of producing graphite epoxy parts is by layering sheets of carbon fiber cloth into a mold in the shape of the final product. The alignment and weave of the cloth fibers is carefully selected to optimize the strength, stiffness, or flexibility of the final product, depending upon it's application.

In demanding applications, all air is evacuated from the mold, but in applications where cost is more important than structural rigidity, this step is skipped. The mold is then filled with epoxy and is heated or air cured.

The resulting part will not corrode in water and is very strong, especially for its weight. If the mold contains air, small air bubbles will be present in the material, reducing strength. Most composite parts are manufactured by draping cloth over a mold, with epoxy either preimpregnated into the fibers (also known as prepreg), or "painted" over it. Hobby or cosmetic parts are often made this way, as are high performance aerospace parts. High performance parts using single molds are often vacuum bagged and/or autoclave cured.

There are very few Aftermarket parts which are made of CF or CRP which are produced for anything more than the 'Trick' look and so are pretty cheaply made - no vacuum or heat. These pretty much perform on par with fibreglass and don't offer any real strength advantages, though they are slightly more robust - but only slightly due to the amount of air bubbles (mostly internal and not visible) they contain.

Happy Motoring!... Jim'99

[Perfectlap]

Originally Posted by MNBoxster

Hi,

The term Carbon Fiber encompasses many different materials and processes - too many to discuss in length here.

Most CF on the Aftermarket is not pure CF, but (CRP) Carbon Reinforced Plastic. The plastic is most often epoxy, but other plastics, such as polyester, vinyl ester or nylon, are also used. Some composites contain both carbon fiber and fiberglass reinforcement. Less commonly, the term graphite-reinforced plastic is also used.

One way of producing graphite epoxy parts is by layering sheets of carbon fiber cloth into a mold in the shape of the final product. The alignment and weave of the cloth fibers is carefully selected to optimize the strength, stiffness, or flexibility of the final product, depending upon it's application.

In demanding applications, all air is evacuated from the mold, but in applications where cost is more important than structural rigidity, this step is skipped. The mold is then filled with epoxy and is heated or air cured.

The resulting part will not corrode in water and is very strong, especially for its weight. If the mold contains air, small air bubbles will be present in the material, reducing strength. Most composite parts are manufactured by draping cloth over a mold, with epoxy either preimpregnated into the fibers (also known as prepreg), or "painted" over it. Hobby or cosmetic parts are often made this way, as are high performance aerospace parts. High performance parts using single molds are often vacuum bagged and/or autoclave cured.

There are very few Aftermarket parts which are made of CF or CRP which are produced for anything more than the 'Trick' look and so are pretty cheaply made - no vacuum or heat. These pretty much perform on par with fibreglass and don't offer any real strength advantages, though they are slightly more robust - but only slightly due to the amount of air bubbles (mostly internal and not visible) they contain.

Happy Motoring!... Jim'99

Why is it so expensive? the build process doesn't strike me as very scientific and the materials are hardly exotic.

[MNBoxster]

Originally Posted by Perfectlap

Why is it so expensive? the build process doesn't strike me as very scientific and the materials are hardly exotic.

Hi,

There are a number of reasons and it's getting even more expensive.

First, it is very Labor Instensive, not an easily automated process.

Second, the cost of producing Molds for limited production runs equates to a high cost/unit.

Third, and increasingly so, while the demand for Carbon Fiber increases, the Supply of Carbon Fiber is decreasing due to the high demand from Contract Consumers causing the price of the Raw CF Fabric and yarns to shyrocket. The market price of Carbon Fiber reinforced plastic saw a 150% increase during 2005, primarily due to increased use in the Civil Aerospace industry.

Allocation and contracts to Boeing Commercial Airplanes' 787 and Airbus' A350 XWB and A380 caused supply constraints, and suppliers raised prices to suit. As the aerospace companies were locked-in with long-term contracts, users of Carbon Fiber Reinforced Plastic in other applications have suffered the brunt of this price hike. In fact, 6 of the 9 top producers of Carbon Fiber are now dedicating 100% of their output to fulfilling these aviation contracts, and will for the next 4-5 yrs. This essentially reduces the availability of supply of Carbon Fiber to the rest of Industry by 2/3.

There are a number of Companies working to make Carbon Fiber less expensive through newer Oxidation processes. Carbon Fiber is generally created from plastics such as Polyacrylonitrile (PAN), a polymer based on acrylonitrile, Rayon and Pitch. These are all derived from Petroleum, and so the price of Oil is another factor in the final price of CF.

These materials are then oxidized through Pyrolysis - the chemical decomposition of organic materials by heating in the absence of oxygen or any other reagents, except possibly steam (think pure, complete Burning). This process leaves only the Carbon as a residue, and is essentially the same process used to make Charcoal and Coke. These materials are used because they generally yield about 98% of their initial weight/mass as pure Carbon. This requires large, specialized, machinery such as very large Autoclaves, as well as large amounts of expensive Energy.

But, Research Labs, specifically Oak Ridge National Laboratories, are working on making the molding process more efficient and cost effective by introducing methods which can be done robotically see - http://www.ornl.gov/info/press_releases/get_press_release.cfm?ReleaseNumber=mr20060306-00

Happy Motoring!... Jim'99

[CJ_Boxster]

"Allocation and contracts to Boeing Commercial Airplanes' 787 and Airbus' A350 XWB and A380 caused supply constraints, and suppliers raised prices to suit. As the aerospace companies were locked-in with long-term contracts, users of Carbon Fiber Reinforced Plastic in other applications have suffered the brunt of this price hike." --wikipedia



Thank god for Wikipedia, you can also see how the Carbon Fibre structures are made for a popular supercar on youtube.

[insite]

Originally Posted by Perfectlap

Why is it so expensive? the build process doesn't strike me as very scientific and the materials are hardly exotic.

aside from materials, the build process to PROPERLY create carbon fiber components, especially structural components, is quite difficult. much of what's on sale in the way of body panels, bumpers, interior parts, etc. is made in more or less the same way as a fiberglass part. in this case, it's not much stronger or lighter or time consuming to construct.

on the high end, very tight controls on the mold (materials, temperature, humidity, etc.) are in place. where i work, we even went so far as to choose a metal that has the same thermal coefficient of expansion as the CF matrix has to prevent distortion.

once the molds have been created, the fabric must be layed up in a manner specific in fabric orientation (you cant' just stick the fabric on the mold). you actually have to choose in which dimensions you want the part to be strong.

application of the resin is a task in itself if one wants to eliminate porosity, boracity / de-lamination issues, etc. after the resin is applied, a vacuum bag is put in place over the mold to suck the fabric and resin together. in some instances, the CF matrix is actually under tension during this process (pre-stressed CF matrix). after this, the whole schebang is baked in an autoclave.

the methods above probably aren't used on your average bumper, but they are used in F1, carrera GT, enzo, etc.

[Topless]

Jim,
Did you rip off Wiki without giving them credit?? Shame on you!

[MNBoxster]

Originally Posted by Topless

Jim,
Did you rip off Wiki without giving them credit?? Shame on you!

Hi,

No I didn't. Someone else PM'd me about Chico's (? or whatever his name is) post, seemingly jabbing me. I didn't see it since his contributions are hidden to me. Guy must be cyber-stalking me, disecting everything I write, I dunno - his prob, not mine, I'm not concerned with what he does.

I took my post from my own notes. I've been working with CF since I was studying for my degree in Materials Science back in the '70's. Back then, there were probably fewer than 1000 people who even knew what it was.

You see, I had a small business with a partner producing cosmetic CF parts for the Lotus Esprit. I met my partner, a fellow Esprit owner, at a Nat'l. Lotus convention we both attended. We had similar science/engineering backgrounds and decided to see if we could make up some parts. That's when we contributed to the article in Wikipedia back in '05. We made contributions to the articles on Carbon Nanotubes and Pyrolysis also - this isn't the only forum I contribute to.

He was actually working for a company and had access to some mold making equipment, including a CNC. I spec'd the pieces, produced 3D CAD drawings and my partner would use these to produce a mold and lay up the piece. We made a few sample pieces, but found that using the painted or wet method produced too many rejects from air bubbles, even when vacuum bagged.

We then started making the pieces from prepreg cloth and autoclaving them. These turned out so well that our reject rate came down from 50% to under 4%. So, we started making them to order. We produced about 1000 various pieces in total. But, since we used this expensive production method, we could not really afford to continue (at a price people were willing to pay, and we sold at near our cost) since we could not reach any economy of scale without making a sizeable investment in equipment and we didn't feel the market (both demand estimates as well as competition from firms already doing this work) warranted such a gamble. But, we had a good time, learned a great deal, made several new good friends, and came out pretty much even.

I'd actually forgotten about this submission to Wiki until I broke out my notes for the current thread. Guess I don't feel the need to footnote an article I co-authored...

Happy Motoring!... Jim'99

[CJ_Boxster]

Lol he thinks I'm stalking, I just decided to check his words against wikipedia and I just noticed that his first large reply about carbon fiber is word for word identical to thw wikipedia information on carbon fiber. Not jabing him, just think its unethical to copy and paste amounts of information like that without parphrasing it or quoting it. People get kicked out of there masters program for that kind of thing. But its a forum so doesn't really matter but I knew he didn't know everything about everything he posts... try compairing his posts to wikipedias info on carbon fiber.... word for word match on 80% of his posts here. And if he contributed his notes on CF to wiki, for someone who is anal to the max, he didnt cite himself at all in the artical

http://en.wikipedia.org/wiki/Carbon_fiber
Heres the history of contributions to the topic of CF on wiki and i see no Jim or MNBoxster listed
http://en.wikipedia.org/w/index.php?title=Carbon_fiber&limit=500&action=history

I must admit, im being kind of a jerk right now so ill stop before things escalate.

[Grizzly]

Exposed as a fraud???



Impossible, because I'm ignoring you... Ignoring you... Ignoring you... I cannot hear you... Ignoring you... Ignoring you...