information on carbon fibre

[marvin]

please enligthen me on information regardin carbon fibre to build a formula sae car
-the grade of carbon fibre used
-the amount of cabon fibre reuired to build a monocouque chasis
-the cost incurred in procuring carbon fibre
-the companies which provide carbon fibre to fsae teams at subsidised rates

[Chris Allbee]

Having built a gazillion of these things myself, i can tell you that you want some 23k fiber. Takes about 500 linear yards for an entire chassis. About 30,000 dollars in material. We make our own carbon by the way. chemically treated cotton fibers wrapped in fairy dust.

[conekilr]

Even if all of the most knowledgable people on this forum answered your questions you would still have to do a good deal of research to determine how to construct a carbon fiber monocouque for your purposes. It would probably be beneficial if you obtained small samples of many different weaves and resins as well as core materials so that you could make test pieces to determine strength and stiffness. With these results and the data you have for loads that the chassis will see, you can determine if CF is the best material for your team. Keep in mind that the goal of a CF chassis is not necessarily to be lighter because, if designed to hold up to the loads we see, it will be heavier than a well built chromoly chassis. However, the benefit of a properly designed CF chassis is much improved stiffness and safety.

I believe there are many technical books and articles on composites and applications listed on the official SAE website that would be more helpful to you than my advice.

[Erich Ohlde]

Originally posted by conekilr:
Even if all of the most knowledgable people on this forum answered your questions you would still have to do a good deal of research to determine how to construct a carbon fiber monocouque for your purposes. It would probably be beneficial if you obtained small samples of many different weaves and resins as well as core materials so that you could make test pieces to determine strength and stiffness. With these results and the data you have for loads that the chassis will see, you can determine if CF is the best material for your team. Keep in mind that the goal of a CF chassis is not necessarily to be lighter because, if designed to hold up to the loads we see, it will be heavier than a well built chromoly chassis. However, the benefit of a properly designed CF chassis is much improved stiffness and safety.

I believe there are many technical books and articles on composites and applications listed on the official SAE website that would be more helpful to you than my advice.

It is heavier than most of the chro-mo chassis at fsae but its stiffness to weight ratio is 3-5 times that of chro-mo tho

[LU-Bolton]

marvin, i'm afraid these guys are right. our team has built a composite chassis the past two years after many years of building steel spaceframes. Unfortunately composites are a thing that can only be learned through practice for the most part, especially if your school doesnt have a great composites facility. There are so many different ways to build them, do you go with pre-preg, vacuum infusion or wet laying? aluminum honeycomb or structural foam? then you have to figure out how you're going to pay for the stuff. don't forget to include all the throw away setup costs, i.e. bag materials that can be expensive and are thrown away after layup. Not to mention the fact that if you screw up, you have to start over. There is no chop and re-welding of composite panels like with steel. As far as fibers and resin picking, that depends on where you can get quality materials for the least price. either from your school or a very kind sponsor. don't forget that an accurate analyzation of a composite chassis is almost impossible unless you use a program like ANSYS that takes months and months to learn. it's a tough road, start your research and then decide.

[Foz]

Marve:

We're on our third carbon tub (see monocoque thread (http://fsae.com/eve/forums/a/tpc/f/125607348/m/33110761511)
for more info).

In answer to your questions from my experience:

Grade:
The highest spec we can get for free. This year we managed to get some F1 pre preg offcuts. Its pretty much the best you can get.

Amount:
Surface area of monocoque x number of skins required x waste factor (I have found this to be ~20-25%). Obviously thicker carbon will need less skins.

Cost:
We get CF material & consumables free. Mostly (quite generous) offcuts and pre preg that is near the end of its shelf life.
The thing that costs is the plug & mould material. This stuff ain't cheap. Even if you get free tooling carbon, epoxy tooling block is ~£6000/m3 and people don't like to give it away. You can get much cheaper stuff, but it is much worse quality.

Where from:
A selection of well known composite suppliers. Our website will give you a clue, but it will all be different in the US, if that is where you are from.

You should bear in mind that making a carbon chassis for a FSAE car is NOT EASY. Every step involves extra time, cost and work. Even then, it is still difficult to get right first time.

LU-Bolton is right - you screw up, you're back (a long way) to square one. Believe me, I know.

You've also got to look at the spec for the car: you need to be able to make 1000/year at less than $26,000. Can you do this in carbon?

The other guys are also right about the weight advantage being minimal. FSAE tubs generally weigh about the same (or some times more!) as good steel frames. They much stiffer, but do you need this?

I only chose carbon over steel because I wanted to learn how to work with composites. At the end of the day, that's what all this is about.

If I was going to make a car only to win the competition, it wouldn't have a carbon fibre monocoque chassis.

Hope this enlightens you.

Chris Foster
Imperial College Racing
www.cgcu.net/icracing (http://www.cgcu.net/icracing)

[Marshall Grice]

. About 30,000 dollars in material.

Just out of curiosity, if the above quote is true, how does a team build a carbon tub with out getting DQ'd from the cost event?

[Erich Ohlde]

i think chris is being a little sarcastic. Although we do sprinkle in a little fairy dust into the carbon we use for our chassishttp://fsae.com/groupee_common/emoticons/icon_smile.gif

[Foz]

Fairy dust aside, the cost event is a load of bull.

[Chris Allbee]

Yes, I was being sarcastic. I'm just tired of "hey i'm building this part for the first time, I don't really feel like doing my own research so could you guys just tell me how to build a car that will win? thanks!" In the past few months these threads have popped up a LOT. I remember when this forum was a knowledge EXCHANGE. If you want a "how to" guide, then you will fail. You can't just mimic someone's design and expect to do well in this competition unless you know all the 'whys' that went into that design. Its been said before, if you want detailed information show people that you have done your own research first, given it some thought beyond "ooh! pretty carbon! i want one!" Or just go ahead and build whatever you can come up with based on casual advice and then send us a picture of the look on your face when you can't figure out why things keep breaking, not fitting together, and plain just not working.

[Erich Ohlde]

Boom!

[Cement Legs]

Originally posted by Chris Allbee:
Yes, I was being sarcastic. I'm just tired of "hey i'm building this part for the first time, I don't really feel like doing my own research....

LOL... Its too bad there wasnt some type of compilation of the best general advice posted. That way poeple new to this project could start there to get caught up with basics. I personally understand how people feel when they want a hand getting started. I've had to be involved in way too many areas of our car to really sit down and focus on one section. When you dont have to spend countless hours of research just getting yourself up to speed on what may be considered common knowledge it really helps with morale. Unfortunately gravity is not constant throughout the universe, the Steelers won the Super Bowl, and this compilation of data only exists in the endless pages of this forum......

[Jersey Tom]

Blah, more of this. Its much more satisfying doing the actual research and crunching the numbers yourself. That and you know its right. Even if people are giving serious advice here, be wary of it. There's a lot of signal, but there's a lot of noise. Just because team X placed high last year and did things one way, doesn't mean its the best way, or even the right way for you.

That said, I suggest you make a wrought iron chassis. With gargoyles.