Fiberglass vs. Carbon Fiber

[SC986]

Interesting. I was wondering because I love the rear diffuser bumper but have not heard good things about the fiberglass diffuser add ons.

[[986]]

Very informative thread! I was looking at some bumpers on Mashaw's site but only fibreglass or carbon fibre are available.. from everyone's experiences what would be more suited to a street driven car?

[insite]

Originally Posted by [986]

Very informative thread! I was looking at some bumpers on Mashaw's site but only fibreglass or carbon fibre are available.. from everyone's experiences what would be more suited to a street driven car?

urethane or FRP. they're flexible. carbon fiber is good, but usually the layups are not done in a manner condusive to high flexibility. cost is also prohibitive, and unless the vacuum bag / autoclave process is sound, they'll have to use too much material, negating the weight savings over fiberglass, FRP or urethane. plus, much of the carbon fiber stuff on the market is actually fiberglass with one outer layer of carbon fiber fabric for looks.

[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!

[markab986]

I agree, urethane for the bumper.

cf is stiff, light weight, and well suited for many applications. But it’s probably not what you want on the street, due to initial cost, and high cost of a specialty shop doing repairs, if an unfortunate event were to occur. It also must be kept from UV, with some sort of protectant, which normally negates the "cool factor" of the exposed weave of the fiber.

One other thing...cf is not corrosive by nature, but when in contact with AL and moisture...you will have an electrolysis effect with the metal. The contact area must be protected using fiberglass.

The choice is really up to you.