Creep 1

[berkshire]

I have a project where a person in front of me added a gas lift strut to a composite structure on an aircraft, the piece was a bulkhead made from 6 layers of 400 gm twill weave fiberglass with a room temperature epoxy resin.
Most likely Epicote 162 with a Laromin c 260 hardener. The attachment fitting for the lift strut was a ball joint, bolted through the bulkhead . when it was originally installed the axis of the ball joint was at 90 degrees to the bulkhead. Now after an unknown period of time the axis of the ball joint is at 45 degrees to the bulkhead, and the bulkhead has crept to a bulge with the fitting now angled out.
The fix would appear be to apply heat and pressure to the area to iron out the bulge, the question is how much heat?
I know from past experience that too much heat will produce white marks in the glass epoxy matrix, and I wish to avoid that.
I also know that this thing crept slowly over time, and that if I try to rush this I am going to create more problems than I solve. Any suggestions , or am I on my own on this one ?
B.E.

You are judged not by what you know, but by what you can do.

 

[Compositepro]

The epoxy will probably not start to degrade until over 350F.

 

[berkshire]

Thanks Composite pro , I will start at 270* and see if it will move at that. The designer of this never thought about the constant pressure a gas spring exerts.
B.E.

You are judged not by what you know, but by what you can do.

 

[SWComposites]

And how does this sove the problem?

Its just going to creep/defect back again. Or are you counting on this heat application to further cure the resin and raise the Tg?

Sounds like reinforcement is needed.

 

[berkshire]

SW composites ,
Getting the bulkhead straight does not solve the problem, I am intending to add a couple of fender washers either side of the bulkhead on the fitting to spread the load out, The prior installer just used standard aircraft washers. Which might have seemed adequate at the time of installation , but did not allow for creep from a constant load. If that does not work I will add a sheet metal doubler .
B.E.

You are judged not by what you know, but by what you can do.

 

[berkshire]

Ok I got the layup to move at 300 degrees F without whiting out. Thanks Composite Pro.
B.E.

You are judged not by what you know, but by what you can do.