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View Full Version : Composites experts chime in, need assistance



RoadRaceFanatic
03-24-2005, 08:39 AM
Hello, I've been reading on this forum for a few months now, but sadly I dont have much to post about since I'm not on a fsae team. I am at least on my way to becoming an engineer. After doing some research for this project, it seems that this place might be the best place to get some answers from, seeing as you guys have more experience with composites used in performance applications than just about everybody.

I want to make a carbon fiber (upper) intake manifold for my car. It will be similar to this design: http://img.photobucket.com/albums/v231/vr4guy/CFmanifold.jpg
After much thought and research, this seems like the simplest and easiest to produce design. I simply need help choosing the correct carbon fiber and resin for the job. This seems like it would be a relatively simple project, but my car is turbocharged which drastically increases the strength requirements. The manifold will need to withstand a max of 40psi of boost and 300 degrees fahrenheit to be on the safe side. I'm more concerned with how it performs than how it looks.

In my research so far, I havent been able to find any information regarding max operating temperatures for epoxies. I'd like to use a 2x2 twill cf weave if possible, I'm hoping it is drapeable enough to make the bowl shape of the manifold.

I have some fiberglassing experience, I have made a few parts and repairs with it. I am confident that I can make a nice mold for this and eventually produce the finished part, I just need some help and guidance. I'm also aware that this will most likely require vacuum bagging, which I am willing to buy a pump and other materials and learn how to do. I'm open to any and all advice you have on what to use and how to use it.

So what do you reccomend for the job? Theres waaaaay too many choices as far as modulus, weight, etc. goes for carbon fiber, and just as many for resins and epoxies as well. Its quite intimidating having all these choices when trying to start a project like this.

Thanks,
Jake

RoadRaceFanatic
03-24-2005, 08:39 AM
Hello, I've been reading on this forum for a few months now, but sadly I dont have much to post about since I'm not on a fsae team. I am at least on my way to becoming an engineer. After doing some research for this project, it seems that this place might be the best place to get some answers from, seeing as you guys have more experience with composites used in performance applications than just about everybody.

I want to make a carbon fiber (upper) intake manifold for my car. It will be similar to this design: http://img.photobucket.com/albums/v231/vr4guy/CFmanifold.jpg
After much thought and research, this seems like the simplest and easiest to produce design. I simply need help choosing the correct carbon fiber and resin for the job. This seems like it would be a relatively simple project, but my car is turbocharged which drastically increases the strength requirements. The manifold will need to withstand a max of 40psi of boost and 300 degrees fahrenheit to be on the safe side. I'm more concerned with how it performs than how it looks.

In my research so far, I havent been able to find any information regarding max operating temperatures for epoxies. I'd like to use a 2x2 twill cf weave if possible, I'm hoping it is drapeable enough to make the bowl shape of the manifold.

I have some fiberglassing experience, I have made a few parts and repairs with it. I am confident that I can make a nice mold for this and eventually produce the finished part, I just need some help and guidance. I'm also aware that this will most likely require vacuum bagging, which I am willing to buy a pump and other materials and learn how to do. I'm open to any and all advice you have on what to use and how to use it.

So what do you reccomend for the job? Theres waaaaay too many choices as far as modulus, weight, etc. goes for carbon fiber, and just as many for resins and epoxies as well. Its quite intimidating having all these choices when trying to start a project like this.

Thanks,
Jake

fsae_alum
03-31-2005, 09:33 AM
Ok man....from somebody who is in the composite business....there are a number of things to consider here. If you want to do a simple hand layup, you're probably going to have to make multiple pieces and then bond them all together using a Hysol adhesive. Another choice is to use an inflatable bladder and layup on that. If you wanted to make multiples later on, you could do a resin transfer mold. The question is...what type of laoding do you anticipate this thing seeing? Is there even a remote possibility that it will come in contact with gasoline? Why can't you make it out of aluminum (as that would be SOOOOOOOO much easier)? What about flow analysis...have you done any to drive your design? In terms of material....where I work we are using material that will withstand 750+ F temperatures so that is not an issue. Material is out there...albeit $600/lb!! If I were you, I'd SERIOUSLY think about using aluminum instead.

adrial
03-31-2005, 10:30 AM
Is the car you're working on a 944 turbo?

Just wondering cause that is the Milledge intake for 944's...

RoadRaceFanatic
04-04-2005, 01:51 PM
Thanks for the replies.

fsae_alum: Why do you think I would need to make it using multiple pieces? I decided to go with the same general design as the intake manifold in the picture I posted since it could be made as a one-piece design, simply being sandwiched inbetween two aluminum plates when mounted on the car. I am already nearly done with a male plug, and am now considering different ways to make the female mold.

I'd like to build it to be abe to withstand ~40psi of boost pressure to be on the safe side. I'll probably never see much over 30 on my car, but who knows. On the other hand, it will also see extreme vacuum when off-throttle. And to top it off, it will be operating at around 200 degrees fahrenheit, so it will need to be able to withstand around 300 degrees to be on the very safe side. It will get a coating of fuel and oil vapors on its interior, theres no stopping that.

I could make it out of aluminum, but I dont know anyone with a tig welder, and I want to try and do this by myself since I think I have enough experience with fiberglass to pull it off. It just seems like a fun project with some potentially great results if I can pull it off. I'd rather build it in the comfort of my garage than making trips to the machine shop and deal with them.

What I really need to know at this point is what CF and epoxy are best suited for my application. I'm also wondering how many layers of CF I should make the manifold so it will hold up.

adrial: No, this is for a 3000GT VR-4. If there was something like this available for my car already I would simply buy it and be done with it. Unfortunately there is little aftermarket support for this platform - There is 2 aftermarket intake manifolds available for my car, both of which have runners a mile long and have the throttlebody on the side I dont want it on, which is why I'm trying to take matters into my own hands.

deersound
04-26-2005, 01:58 PM
I wouldn't do it if I were you, but if you've got your mind set on it, here's a few things to keep in mind.

Since you've already got a buck made, I'm assuming you've figured out a way to make a mold that the finished part can come out of. The plenum in the picture doesn't look like it can be pulled off a mold in one piece. Don't count on the part flexing to come out, because to withstand 2.7 atmospheres the thing's gonna have to be fairly thick.

Second, you'll HAVE to vacuum bag it, and you need to make sure you get as close to a full 30" of vacuum as possible... at least 29". You don't want any little bubbles left in there acting as stress risers.

For resin, you should look at AOC Resins or DOW, and use their spec sheets to find something that fits your operating conditions. Expect it to be very expensive... fuel resistant resins are usually phenolic (cancer causing and expensive) and weaker (I think) than epoxy resins. Make sure you follow their directions exactly for the mixing and curing process. I think most of the specialty resins are temperamental about that.

As for the thickness of the part, I couldn't tell you. I've done FEA on carbon structures under internal pressure, and it is an application where carbon's high tensile strength is a godsend. But how much of it you'll need will also depend on the resin strength and the part geometry. I'd suggest you use a lot... maybe have a 3k twill on the outer surface to make it pretty, then add a few layers of 12k behind ot to make it strong. You could build one and pressurize it until it blows. Just make sure you're nowhere near it when it does pop. If it doesn't take at least 50psi, make the next one thicker.

I'm far from an expert, so you might want to do some research on your own too.