Skyhawk5PT
Aerospace
I work for a company who is relatively new to autoclave processing. We are working through an issue during our cures in which the vacuum pressure is decreasing during the ramp phase. The adhesive is condensation polyimide supported film adhesive.
The cure parameters are as below:
Apply full vacuum (minimum of 24 in Hg)
Apply 25 +/- 5 psi external pressure
Heat from 75F to 350F at 2-5F per minute
Hold at 350F for 90 minutes
cool under pressure below 140 at 2-5F per minute
For our process, we vacuum bag the part and perform a leak check. At this point, the bag holds 29-30 in Hg. We then apply external pressure and begin the temperature ramp. The vacuum pressure holds steady until the temperature reaches about 180F. At this point, the vacuum pressure begins to decrease and usually stabilizes around 24 in Hg. As the cure progresses, the vacuum pressure increases and by the time the full soak is complete, the vacuum pressure is back up to 29-30 in Hg. We are scratching our heads as to why this is happening. We have looked at how we are bagging the part and tried many configurations but the condition still prevails. Has anyone faced this issue before?
The cure parameters are as below:
Apply full vacuum (minimum of 24 in Hg)
Apply 25 +/- 5 psi external pressure
Heat from 75F to 350F at 2-5F per minute
Hold at 350F for 90 minutes
cool under pressure below 140 at 2-5F per minute
For our process, we vacuum bag the part and perform a leak check. At this point, the bag holds 29-30 in Hg. We then apply external pressure and begin the temperature ramp. The vacuum pressure holds steady until the temperature reaches about 180F. At this point, the vacuum pressure begins to decrease and usually stabilizes around 24 in Hg. As the cure progresses, the vacuum pressure increases and by the time the full soak is complete, the vacuum pressure is back up to 29-30 in Hg. We are scratching our heads as to why this is happening. We have looked at how we are bagging the part and tried many configurations but the condition still prevails. Has anyone faced this issue before?
