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Autoclave Bag Leak

Autoclave Bag Leak

Autoclave Bag Leak

Hello partners, I have a topic that would like your expertise support. I work on a composites company on which we cure some of the parts using autoclave pressure, the process specification does not mentions anything about bag leak requirements, the only the specification calls for is a pressure of 20 to 40 psi, the part obtained a 40psi thru the entire cure cycle, but presented a possitive pressure under the bag (Baqg Leak) of 10psi, that means that the pressure recieved during the cure cycle remained at 30psi at least thats what I believed it happen since we applied 40psi and the part presented a leak of 10psi thru the cycle, that means the 30psi that remained applied to the part complies with Specification requirements of 20 to 40psi.

Am I interpreting the correct way or theres something I'm not considering that I should have?

Thanks a lot for your kind support!!

RE: Autoclave Bag Leak

Do you believe that the 10 psi you measured is representative of every location under the bagging film? Where is your gauge and where is the leak?

RE: Autoclave Bag Leak

Does the part pass NDT?

RE: Autoclave Bag Leak

Hello Compositepro and SWComposites thank you very much for your quick response is greatly appreciated, below are the answers:

Do you believe that the 10 psi you measured is representative of every location under the bagging film? Where is your gauge and where is the leak?

Sorry I made a mistake the leak represented on the autoclave is 10in/hg which is around 5psi, the leak is measure by the probe port on the part,the leak seems to have come from the resin that reach the final bag which was burnt.

Does the part pass NDT?
Yes the specimens representing this part which also was piggy bag to the part that leaked pass the drum peel, long beam,short beam and barcol hardness test performed on them.


RE: Autoclave Bag Leak

No, I was not asking about test specimens from a separate panel. Those do not prove the part is good. What about the NDT (ultrasonic) inspection of the psrt?

RE: Autoclave Bag Leak

I suggest you start by considering the consequences of a bag leak. Firstly, inadequate pressurisation of the part. This may result in a high resin content so the part does not meet thickness requirements. Measure the part.
Secondly, the lack of pressure may result in a high porosity level because any liberated volatiles are not compressed due to the inadequate pressure. You may not see this in NDT scans.

If the bag burnt, I'd be concerned about thermal damage to the resin and residual stresses.



RE: Autoclave Bag Leak

Thank you all for your GREAT SUPPORT !!

RE: Autoclave Bag Leak

A number of resins (phenolic, bismaleimide) will corrode Nylon bagging film on contact. The bag appears to be burned. The fix is to use FEP release film to protect the nylon film from contact with liquid resin bleed.

These parts appear to be sandwich panels with some solid laminate areas. Common cure cycles for this type of part usually vent the vacuum at some point in the cycle.

RE: Autoclave Bag Leak

No. That is not normal or acceptable. Probably makesthings worse.

RE: Autoclave Bag Leak

And you never answered the questions about ultrasonic NDT of the part.

RE: Autoclave Bag Leak

My bad SWComposites sorry for not answer about the NDT Ultrasonic, we dont perform Ultrasonic test but we do perform a Thermography Test on parts the one mentioned with the issue did not presented any delamination or porosity indication at all.

Thank you very much for all your support !!

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