There was a thread here somewhere about XPS for use with things like tables or furniture. If you have thin plywood or veneer for impact resistance it can work for that.
XPS is used in SIP panels to build houses but that is properly engineered around thick OSB panels. I think 1/2" or 1.5cm or something.
The compression strength of XPS is fine if you add other material to provide impact resistance and sheer strength - which XPS doesn't have.
If you only put fiberglass on XPS you end up with much thicker laminate that you really need compared to PVC or other structural foam. Truck boxes are made like this I think.
Personally I think (and I'm still a total newbie) it only makes sense if you need thick insulation. Otherwise just use structural foam. But if you really need something like 3" insulation, then structural foam price becomes just insane. There is also XPS foam with new foaming agents that provide better insulation than structural foam with CO2.
You could build a deck with thin plywood and fiberglass on both sides of the XPS and add some thin wood ribs to increase beam strength. But that gets complicated and only really makes sense for insulation.
Then there is 3D core which is a curious case. They started with offering PET foam in hexagonal shapes for vacuum infusion which has some advantages like not needing a flow medium and creating a structure similar to honeycomb core but the epoxy resin becomes a structural element.
Recently they added slightly higher density
XPS 3D core foam (45kg/m² instead of the usual 28 to 35) but you'd need to be carefully consider and probably test the mechanical properties. But it's not actually cheaper than other forms of foam. I'd love to know more about that too.
My guess is you are trying to save money? Best to include what you are trying to do and why you're trying to do it.
There is
Chinese PVC foam that is cheaper than the usual stuff, would love to hear how well it works. But depends where you are and if you can import and have it shipped cheaply enough.
