New to composites or plastics - need some help.

General Composites Discussions Composites Talk
#1

I am building a prototype device that will (during operation) sustain air temps of approx 500 degrees F. My current prototype is made of steel but I really need to reduce the weight, but still maintain the rigidity and strength. I’m looking for a composite or plastic that someone may be aware of that will have these ideal qualities and be no more than .250 thick, thinner is better and maintain rigidity, strength and be machinable (cut, drilled, etc). Also, the composite/plastic will basically need to be sheet or plate style, and able to be cut, etc.

I’m knowledgeable in metals, but plastics/composites are new to me, willing to learn. Any help appreciated. Oh, also, trying to keep cost below the cost of my current steal prototype, so if you can recommend a plastic/composite perhaps it can be made through a DIY process or purchased relatively inexpensive. Thanks!! :smiley:

#2

I guess for these temperatures you will need to look at cyanate esters. But I am sure someone onthis forum has a more elaboratove answer.

#3

But it won’t be cheaper than steel!

#4

Thanks! Well, what is the absolute working/constant temp carbon fiber sheeting can be exposed to without degradation? I might be able to shield the heat source and thereby reduce radiating heat. Thanks.

#5

Cynate esters, BMIs, check out PEEK, PEKK, and PPS plastics. There are several other resins that can handle that temp, which are of other chemistries.

#6

carbon fiber can handle 450c…600c in inert atmosphere

#7

The carbon fibers can handle that heat but the resins that make it rigid cannot. Relatively available epoxy resins can only tolerate 350-400 degrees F. Expense goes up with the temperature capabilities. It will not be cheaper than steel.

#8

I burnt the scraps of my carbon boat (mixture of carbon, PVC foam, wood, aramide and epoxy) in a closed fireplace, and although I was able to burn the exhaust to red-hot, I never have been able to burn off the carbon fabric. The rest, however, is not a problem.

Would PEEK work? Its Tg is relatively low, I thought.

#9

Thanks everyone. A few more questions, some testing, and I’ll post back to see what my max temp is if I control radiant heat. I see CF is quite expensive. However, I may try to set up a few small panels myself and see how it comes out (I’ve done some fiberglassing in the past) - however for quick prototyping I may just buy something already made and see if it even works before expending too much time and energy. Which brings me to the next question: I need a material that is .125 - .1875 thick - flat panel. Would it be best, and less expensive for a panel made out of all carbon fiber material to this thickness or use a core of some material wrapped in CF? If a core would be the best option, which type of material should I look for, for strength and rigidity? Thanks again!

PS - I checked out some of the high temp plastics, and damn they are VERY expensive. If I could get away with a material that maybe a little higher priced than steel but significantly lighter I might be able to justify it. Thanks again!

#10

As soon as I saw the temps you need to endure along with the need for strength, light weight and rigidity, the first material that came to mind was titanium. Don’t get me wrong, I love trying to make things out of FRP as much as anyone else here but sometimes there are more suitable materials available. :slight_smile: