Adhesives Question 1

[dshaffer1001]

I have a problem with an aircraft door seal that's disbonding. The door is a composite door with a rain seal around its outer edge. The current seal is an AMS 3195 silicone rubber strip, bonded to the door with MIL-A-46106 Group I Type I silicone adhesive. I'm not an expert on adhesives, but this stuff does not seem terribly strong or durable.

Can anybody suggest a better adhesive ?

I've been through ASTM D 6465, and while that's great for the initial design, I'm looking for something a little more specific, i.e. actual manufacturer and part number, that sort of thing. Any guidance you folks can give me will be appreciated.

 

[MiketheEngineer]

Check w/ mfg for known problems??

 

[thruthefence]

Don't some of these need a primer?

 

[MintJulep]

Where is the bond failure?

 

[dshaffer1001]

They are disbonding in several places around the door edge, but do not seem to have a "favorite" spot.

Then again, my sample size is pretty small (3 out of a fleet of 20-odd aircraft).

Not sure about the primer, will check.

 

[MintJulep]

I meant is the failure between the adhesive and the door, or between the adhesive and the seal?

Regardless, if the adhesive selection is even remotely appropriate for the application adhesive failure almost always comes down to improper surface preparation.

With a composite I would suspect contamination from mold release or amine blush.

 

[dshaffer1001]

Can't tell - Unfortunately I didn't know to look at the time, and my photos don't show it clearly (I was at a site survey looking at other things, and this was a bit of an afterthought). However, I will pass that question on to the folks at shipside.

 

[wes616]

These are often problems with improper surface prep. My guess would be that the seal is dis-bonding from the door frame due to poor surface prep of the door frame. Does the composite appear glossy? Especially at the areas of contact with the adhesive?

Try to "rough it up" with some 120-grit sandpaper, then wipe it down with IPA before bonding.

Wes C.
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[MintJulep]

IPA = India Pale Ale?

 

[CoryPad]

IsoPropyl Alcohol