I am looking to join two halves of a car spoiler together. The spoiler is a 2-part mold, with a hollow inner section. I understand that the “best” method would be to use a joggle gasket to join the two halves, but I am starting to re-think that because it’s going to take quite a bit more time to process the parts by using the joggle gasket. Plus, due to the way I’ve designed the joggle I’m concerned about the bag bridging in the corners and creating resin-rich sections, or possibly even trapping air in the part.
My new idea is to use a black structural adhesive around the two halves of the part, and then butt joining the two sections together. After trimming, the “bond line” would only be about 1.5mm in thickness. I am aware that would not be the strongest bond, so my plan is to fill the inside of the part with pour foam. My thinking is that the foam will aide in bonding the two halves together, and create additional strength for the bonded part. Does this sound like a good idea?
My next question is what foam to use. I could use a 2-part PU foam w/ 16lb density, but how well does PU foam bond to a carbon part made w/ epoxy? I have found a source for an epoxy foam as well, but it’s more expensive. The inside of the bonded area would have a peel ply textured surface, so the foam would be adhering to a peel ply finish. Would an epoxy foam bond better than a PU foam? Or would they both be about the same?