I am quoting a big job and need some help. I know a lot of guys are doing pre preg, but am not sure how many of them are doing it. I know it is typical to do autoclave for pre preg, but was wondering if it is really necessary. Can you just use an oven and vacuum bag your part to get a quality carbon fiber part?
you can vacuum bag carbon prepreg and put it in an oven but it ideally needs to be resin rich (45% RW +) to get a very good finish. We use heated platen presses & compression moulds aswell… 
Dougie, in my former classroom (there’s step by step pictures on here…) we use CF PP that was 2 years old (but frozen all the unused time), vacuum bagged it (Bondline system) and oven cured it AOK!
But this was not stucture tested parts…
45% resin content is only neccesary if you are using prepreg twill and weaves. uni-carbon can typically be 35% or even lower. autoclaves are not needed by anymeans, however you do get a stronger laminate with one. vacuum bag and post cure will work awesome
Because everyone else told ya the same thing, I really love pre-preg.
Yeah, bag and cook. Follow the manuf’s instructions for cooking as close as you can.
It’s a slightly different puppy, so if you want some pointers on bagging it (not careful, and the resin will suck out of the fabric), let me know. I might have tons of pics.
ok, if anyone can allow me to contact them offline to discuss some of these things. I would love it. I am in process of quoting a HUUUUUUGe job. I am almost having an anxiety atack because of the size. We are being given an awesome chance to do this and do need some pointers.
You would get more help if this is discussed on here rather than in PM’s.
who does everyone buy their pre preg from?
What is a going rate for Unidirectional?
What needs to be donwe to the surface of the tools prior to laying in the cloth?
West coast (but they also have plants back East too…) Cytec Engineered Materials
(714) 666-4342 Inside sales dept.
For new and reconditioned / used auto claves Thermal Equipment (310) 328-6600
you can get newport prepreg from northern fiberglass
lewcott, bryte, jps, newport, and cytec are the few companies I have delt with in the past. Also, try http://tmi-slc.com/ They have helped me in the past with samples to get me started with pre-pregs.
(just pretend you will buy lots more!!)
rates vary. normally you will contact the company with an epoxy need. Like the cure temp, what kind of resin (epoxy, BMI, cynate ester, ect), and then what weave, aerial weight.
My experience with Unidirectional is bad. It’s not overly tacky, and it only really likes being draped one way, But, if you are making large flat parts that need strength in one direction, then yeah, it’s good stuff.
Remember, you need heat to cure this stuff, so high-temp epoxy or aluminum molds are the way to go.
i’ll email you some pics of stuff to give you an idea. (they are large, so I can’t upload them anywhere easily)
When you order the prepreg, you can specify oven or autoclave curing and the supplier should be able to B-stage the resin to accommodate one or the other. Unidirectional CF/epoxy is usually autoclaved. You may be able to rent autoclave time from someone nearby or a university or lab.
I made boats from uni-carbon prepreg and honeycomb core with out using a autoclave.