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Testing XPS foam for epoxy adhesion/bonding

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Vigilant1

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I don't live near a large body of water, and I'm finding out that means that Dow Buoyancy Billet foam isn't readily available near me (unless I'm willing to buy a LOT of it and pay for that partial truckload to come to my house). I do know a guy who is building a Long-EZE, I may ask him for a few scraps of whatever he's using. If I were building plane with it now, I'd probably just bite the bullet (or use it as an excuse to take a road trip to the Great Lakes), but I just want to get some experience with laminating to foam and also do some impact tests.
I can get high-strength Dupont (was Dow) blue XPS foam--60, 80, and 100 PSI compressive rating (and that's for 5% compression, not the oft-cited 10% criteria). I've heard that some foams just don't bond well to epoxy, whether due to additives (silicone?) or a very fine cell structure--maybe too fine for the epoxy to get a grip on?

Stansilavz posted a link recently (I can't find it) with an informal test a guy did--prepped some EPS and XPS in various ways (sanding, no sanding), then did an open layup (fiberglass?). After curing he peeled them off and used a fish scale to measure peel strength, together with an examination of whether the bond failed or the foam failed.
I'm thinking of doing much the same with various brands of XPS foam available to me. I'll hot wire all of them to get rid of any facings, test some with no prep, some with a few passes of 80 grit sandpaper, and also test the effects of wiping with isopropyl alcohol. Then layup/vacuum bag some strips of fiberglass to each of them, let cure thoroughly, then try to peel them up. The fish scale didn't seem to give a very precise result for the guy in the video, maybe I'll hang weights and see when the strips zip off. I suspect the type of failure (foam or epoxy-to-foam, and the consistency of that failure) will be at least as telling as any measurements.

So--
1) Does this sound like a worthwhile approach to gaining useful information?
2) Is peel strength a good stand-in for shear adhesion strength?
3) Any opinions on whether a good bond today is likely to remain a good bond for decades? We know that the right foam stays stuck to epoxy--is it likely that any silicone, flourocarbons, etc in the foam might only affect the bond a long time down the road?
4) What does "right" look like? Are there any published tests of peel strength of fiberglass/epoxy to Dow Buoyancy billet XPS? Rutan was good about offering "confidence tests" to builders of his planes as far as weighing and testing coupons of layups. Are there any field tests of adhesion to core foams?
5) Are there other types of foam that are known to bond well to epoxy? Dow/Dupont blue Styrofoam XPS insulation? Corning pink Foamular XPS sheets? Kingspan Greenguard XPS sheets?

Thanks for any assistance, criticism, lewd links, etc.

Mark
 
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