Hello,
Recently i show something that i can not explain …
I put some plates of prepreg carbon fiber in the oven for cooking and
after a while o saw that the plastic bag was not tight anymore so i opened the oven and it really wasnt tight…so i said that something happened with my set up and i lost vacuum (the part is not connected during the cooking with the vacuum pump).
Untill here everything ok…things like this happen all the time…
But when the cooking finished and the part got cold and i took it out of the oven the part was in vaccum again! -0.8 bar
Was it themal expansion? But what got expanded since there was no air inside to be expanded?
Water … I think:)
Can u please explain?
Was it very loose or just a bit looser? Remember at -.8bar there’s still a decent bit of air in there so it will expand when heated and retract when cooled (Combined gas law). Any volatiles and water given off during the cure will then also cause further expansion and pressure loss.
What i meant was that after i finished with the cooking proccess i had -0,8 bar inside…when i started it was on full vaccum…i can easilly explain why there were fumes inside during the curing which destroyed the vaccum,what i can explain though is how when the proccess finished there where no fume and i was on vaccuum again,almost…
Water in bag, as a liquid, in the beginning, boiled water in oven ( gas expanded bag) bag cools down, gas turns back to liquid and tight bag reappears.
Do you do a long debulk under vacuum before curing? Also sounds like you should keep the vacuum running during cure as well.
curing resin outgasses. Some do a little, some out-gas a lot. You need to have vacuum connected during cure, else that will happen. You could also have a leak, any humidity will expand, etc etc.
Keep the vacuum connected!!!
Ok ok understood … vacuum connected…I am doing some modification to my vacuum pump so that it will be live all the time during process …- I added a vacuum switch.
Thank you