What is Best Material for Flat Panel Tables?

Particle board is really flat and cheap and doesnt warp as long as it doesn't get wet. That's why it's used for countertops and tables. Melamine is PB with that very thin plastic coating on it. I wonder if resin would stick to it because it's really slick. 2X4s might warp and are rarely super staight. You could build a table using metal studs which are super straight and just slightly more than lumber. They are really light, too.
You don't have to weld, just screw your top through the joints.
There is a product called drywall shims which are 4' long pieces by 1/16" thick by 1 1/2" wide of dense cardboard that you can use for minor shimming and leveling. Good Luck

 

Almost any material will change size with temp or moisture, steel tables will distort with temp changes unless they are in a temp controlled environment. Wood, even particle board, will change thinkness and shape with moisture and temp changes.

I think the best bet is heavy 1" particle board or Melamine, and backed with 2x4 or 2x6 stringers no further apart than 2 ft (16" spacing would be better). Use screws at 6" spacing, and construction adhesive in all contact surfaces. Than paint the particle board with several layers of vapor barrier paint. That should keep moisture changes to a minimum.

You might also consider laminating on top a layer of Masonite to give you a smooth hard surface. Or look into using the heavy plywood used to make concrete form boards, they have a smooth Masonite or plastic vernier on the outside and are really stiff. These are pretty costly, but you likely can sell them to a concrete contractor when you are done. They beat the crap out of them and have to replace them regularly.

Good luck.

 

laminating table........ on wheels

This is the basis of my laminating table, here it is under construction, an 11M long trailer, the untapered part is 8M x 1.8M & I use 2 other steel framed tables at 3.6 x 1.8M to sister up to it. I used it as a storge base/trailer for my tooling & to transport long but light stuff, axles/springs etc rated to 3.6tonne max. I use 3.6M x 1.8M melamine faced 16mm particle board from Laminex industries on them.

 

Consider not fastening the table top to the framework, or fastening it loosely. That way the table top and framework can expand and contract independently with changes in temperature and humidity. If fastened tightly together they will warp unless they expand/contract exactly the same amount in unison.