Fiberglass vs. Carbon Fiber

[Topless]

Fiberglass
A fairly generic term in which you take fiberglass mat or cloth and lay it up with resin to form nearly any shape. Found everywhere, boats, surfboards, airplanes, car bodies, rocket motors, space shuttle etc.
Pros- good strength to weight, easy to work with, can be made very flexible,low cost.
Cons- repeated flex can cause failure, gets brittle when uncoated/painted and exposed to sunlight. Glass fibers get in your skin when sanding and make you crazy.

Carbon Fiber
The same basic process as fiberglass only using carbon fiber cloth and high quality resins to get the highest tensile strength, highest strength to weight, and achieve a very rigid shape or structure.
Pros- Ultra high strength, ultra rigid, resists damage from sunlight when unpainted.
Cons- does not flex, if flexed it shatters like glass. very expensive.

Traditionally this was only found on ultra high tech applications (fighter jets, space shuttle, F-1 race cars, world class racing yachts) due to its high cost. It is now much more mainstream (even NASCAR bodies use carbon fiber now I think) and has become a fashion accessory of the Rice racers and others who have body and dash panels laid up with carbon fiber just for the look. Most of these panels are not pure carbon fiber but common plastic/metal panels with carbon fiber skin. No lighter in weight or stronger than fiberglass. Just pure bling. All foam...no beer.

So do you want carbon? Is ultra high strength/ultra rigid important for your application? If so then carbon fiber is the way to go if you can bear the extra cost.

[insite]

Originally Posted by Topless

Carbon Fiber
The same basic process as fiberglass only using carbon fiber cloth and high quality resins to get the highest tensile strength, highest strength to weight, and achieve a very rigid shape or structure.
Pros- Ultra high strength, ultra rigid, resists damage from sunlight when unpainted.
Cons- does not flex, if flexed it shatters like glass. very expensive.

i take exception to the last statement. carbon fiber can be designed to flex very well (think golf club shaft or corvette leaf springs). CF properties can be greatly varied depending on the manufacturing methods (resins, mold types, cure method, etc.).

[Perfectlap]

^ very true you should see my carbon fiber bicycle's rear triangle flex when out of the saddle hill climbing. These guys can do amazing things nowadays.
But ohh so expensive. I lusted after a Fondriest frame made from F1 grade CF (they had a former F1 Ferrari engineer) but they couldn't make the darn things for less than $6K and eventually went out of business. Too bad, best bike I ever owned (partially CF).

[Topless]

Insite,

You are right. I forgot golf shafts. My experience with CF was on racing yachts where it was chosen and designed to eliminate flex.

[EPIQTodd]

For a spoiler, fiberglass is just fine. No advantage for polyresin on that one.

Regarding carbon fiber and composites, I wholly disagree that it is a 'low tech' process - if done poorly, it is, but done correctly, it is VERY high tech, and difficult to do. Those who do the half-ass method of just using resin and drying in the open air are just making fiberglass with carbon fiber sheets. True carbon fiber and composites must be cured in a heated vacuum, and that is what makes good carbon fiber what it is.

[yellowboxster01]

i've heard the mount holes on some of the aftermarket spoilers crack out after time. i believe there was a thread on here a couple weeks ago about it.

[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!

[porsche986spyder]

Originally Posted by yellowboxster01

i've heard the mount holes on some of the aftermarket spoilers crack out after time. i believe there was a thread on here a couple weeks ago about it.

Yes, what he said. If your getting a spoiler made out of Figerglass, just make sure the mounting brackets are made well and don't crack at the base. This is why I would go with Carbon Fiber, it's less prone to stress cracks. I had a spoiler on my other car that slowly began to crack because of vibrations that were sent through it every time I closed my trunk. They started right where it bolted up to the deck lid.