Quote:
[blue insulation foam will delmaniate. Its does not have the peel of sheer strength needed as a core in a composite sandwich. Its fine for non-structural insulation assuming you use a resin that will not melt it.
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I'm going to qualify my earlier post. While I still wouldn't recommend it for your application, Sean, there are times when the blue foam might be used. Shine is right that the peel and shear strength of blue polystyrene is very low compared to other core materials. But you can compensate for the low strength by using a thicker core.
The core in a composite sandwich subjected to bending loads, whether it's plywood, foam, or some other material, acts like the web in an I beam and resists shear forces. The laminate on both faces of the panel act like the flanges of an I beam and resist compressive and tensile forces. Like an I beam, the farther apart the flanges or laminate surfaces are, the lower the forces acting on the materials. Bottom line, if the core is thick enough, it doesn't have to be as strong to resist the same bending loads as the core in a thinner sandwich laminate.
So one application where it might make sense to use a blue foam core is for the deck over a cooler where you want a thick core for thermal insulation anyway. I've built an in-deck cooler and intend to core the lid with blue foam about 1.5" thick. The lid will only be about 15" in the short dimension, so bending loads will be very low.
Dave