Fiberglass vs. Carbon Fiber

[SC986]

If you/can you paint the carbon fiber what will the finish look like? Will you see the fiber or can it be matched in a smooth finish like the bumper?

[markab986]

Originally Posted by SC986

If you/can you paint the carbon fiber what will the finish look like? Will you see the fiber or can it be matched in a smooth finish like the bumper?

Yes, you can make a super smooth finish.
It depends on the tooling/cure process, fill & sand, and the desired finish.
Most composite components will need some sort of buildup, insert, or stiffener in the hole areas to prevent cracking.

BTW...fiberglass is a composite material too!

[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.

[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.