Autoclave prepreg without autoclave

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#1

I have a question :
What will happen if i cure -at the specified from the manufacturer
schedule temperature a prepreg material but instead of autoclave process i use just vacuum bagging process ?The laminate will around 2 mm in thickness . I think that the autoclave helps in less void content so the material has some ‘‘Small??’’ percentage of better properties.
Otherwise the resin matrix will cure as it was supossed to cure without any difference?

1)Am i right or not ?
2) Do you use prepreg for autoclave process in out of autoclave process ?

#2

It can cure pretty much the same as you suggest however the differences are in gas & volatile extraction as well as flow. Its fine if the pre-preg is a breathable pre-preg designed for out of autoclave use but if its an autoclave pre-preg, you shouldnt use it out of autoclave.

#3

Why ?
What will happen?

#4

Make a test panel and see what it’s like.

The main difference would be in how well it would breathe, so you might have higher void content. If you do a good layup schedule with debulks at regular intervals and then bag with breathable edge dam and use perforated release film, you’d probably be ok. Plus a long debulk before curing.

I’d bet you could get some good parts. Maybe not aerospace quality but, hey.

#5

Can’t claim any real experience with this exact issue but a pass with a spiked roller couldn’t hurt

#6

I would expect the main consequences to be

i) poor surface finish with a high level of pin-holes
ii) reduced mechanical properties due to increased void levels

#7

The reason for this conversation is that most of the stractural prepregs that i can find our autoclaved and the ooa are mostly for cosmetics, so i try to find a way to get my hands on autoclave materials without an autoclave … if anyone of you has some recomendation about aao prepreg with high strength is more than welcome .

What if by a silicon mold or something i could inflate something outside of the bag creating possitive pressure around it maybe up to
10 bar…
Would it be like be like using autoclave ?

#8

There are plenty of OOA structural prepregs out there

#9

Pretty much all pre pregs are designed for use with autoclaves.

They still work fine in an oven only process but the parts will have some voids and porosity as expected with much less pressure.

Voids in the laminate like this could be quite acceptable? it all depends on what you are making. Having voids in the laminate does not automatically mean your parts are no good or that they will break.

I have made plenty of pre preg plate up to 12mm thick but mostly around 2-5mm thick. You can debulk the layers every now and then (after each 2-3 layers or more) and this can be done at ambient temp or you can also do this hot in the oven “hot debulk” at 50-60 degrees for 15 minutes to help the air evacuate. It just adds a lot of time to the job, bagging, heating, cooling etc.

I made some small plate parts last week 3.2mm thick ( 15 layers 200gm) with no debulking. Just bagged and cooked.

If you can you will get a better surface finish off a PTFE sticky back material on your mould face.

#10

You are doing all the above using autoclave prepreg?

#11

I believe so. I know it’s not a specific OOA material.

The part I made last week is this angle bracket here https://www.facebook.com/Fastacraft/photos/pcb.588267474648521/588267277981874/?type=1&theater

#12

What is the material do you use Fasta?