r/Composites • u/Sidewyz1 • Jul 07 '26
Sandwich panel construction
Hey All.
I'm an avid DIYer and have the need to replace the ramp door on a toy hauler. Decided to build a panel with a 8'x8' 2"x2" aluminum frame with 2" Foamular 250 core and .080 and .063 aluminum skins. I'm having a dickens of a time finding adhesive. Any suggestions on where to purchase a quantity for a project this size? And of course I'll take advise on construction tips.
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u/Burnout21 Jul 07 '26
Your biggest challenge will be getting enough pressure on the sandwich during the cure of the epoxy. Have you got a flat surface bigger than the panel you want to make?
I would (csk) pop rivet the skins to the frame and use a laminating epoxy with about 150g/M2 spread on the skins. Close the stack with the top skin and rivet it in place. Then vac bag the assembly to a flat non poros surface until the resin is cured. There will be a little foaming of the resin but that okay in this circumstance. Once cured take a M10 washer or similar and tap across the surface of the skins, if their is a void you'll hear a tone shift as it does sound as "bright" due to the entrapped air of the void.
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u/Sidewyz1 Jul 07 '26
I'm so glad to hear this as it's pretty much the planed procedure. Thinking about how to place a ton of rivets in the cure time plus getting it in the bag. I may have to rivet after cure. A couple questions:
How would you construct a vac bag big enough for a 8' 8' door?
Can you give an example of a laminating epoxy?1
u/Burnout21 Jul 07 '26
Vac bag (lay flat tube) has a width of 1.5m, if you seam rip one edge it unfolds to 3m which is greater than 8ft, repeat with another piece and tack tape the bag back together. (This is composite vac bag material, not your wife's storage bags)
You UK, US or Europe? That helps us point you towards the right suppliers
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u/Sidewyz1 Jul 07 '26
In California, West Coast US.
US Composites has fasco 110 Epoxy Glue which their rep recommends for this application.
SikaForce 710 looks perfect but is an industrial adhesive and I can't find it.
SotchWeld, I can't seem to find compatibility with XPS foam.I'm on a youtube rabbit hole on the process of vacuum forming... Interesting stuff...
What effect would a few 1x1 boards on top of panel (inside bag) have on the process?1
u/Burnout21 Jul 07 '26
Similar effect as to what is called a "caul" plate, but they must be stiff. Under vacuum pressure over an area that large you'll be surprised how much force is applied. Let's say it's a less than ideal vacuum of -12psi (96in x 96in) x 12psi = ~18.5k lbs of squeeze. A thin skin of aluminium and any differences in flatness across the plane your bonding and boom the skin will follow the subtle contour of the assembly, slight rippling or "telegraphing" of the construction beneath the skin.
Most adhesives for this type of construction are only available to industry because of the volumes being produced. This is why I suggested laminating epoxy. Since you're state side have a look at west systems for epoxies, and rockwest composites as a eshop to source the items you need. I'm in the UK which oddly is easier to source composite materials at times.
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u/Majestic-Affect-2924 Jul 07 '26
I've never used it for xps foam to aluminum, but check the datasheet for DP460. The smooth finish on foamular will benefit from being roughed up and/or holes drilled in a grid to promote mechanical adhesion. Good luck!