Bogo
FOOF
The stuff is expensive unless you can salvage it. Also because of the slots on the side, square tube of the same dimensions will be significantly stronger. I see they have added some profiles without slots on some faces. They may be a possibility for the cross bars to support a platform, but note the dimensions 1.5" sq.
As mentioned, a honeycomb sandwich structure will be very light. The gotcha is you need to orientate the walls of the honeycomb right. You need to have one of the 3 directions the walls line up with the gap you are spanning. This would have them cross wise for the typical drawer set.
Another option would be a medium to dense foam core between two sheets of AL. If you make it yourself, you can put wood bars in where you need attachment points and around the edges. I'd use a good hardwood to get the best holding power for wood screw fasteners. Gluing up a panel takes vacuum bagging. The home built aircraft industry has lots of online write ups on how to do this. The most important part is glue selection. It needs to be compatible with your core foam, wood and aluminum. Thinking about it, using aluminum square tube stock in the core for the attachment points could be done. Think about it carefully as it limits the attachments methods that can be used.
Aircraft Spruce is a major supplier to the homebuilt aircraft market and has most of the materials and unusual equipment needed for vacuum bagging.
Pilot Supplies, Avionics, and Homebuilt Aircraft Parts from Aircraft Spruce and Specialty Co.
Most everything needed for vacuum bagging is under the Composites page.
Composites from Aircraft Spruce
Pay attention to any compatibility warnings they give. Polyester based resins will melt styrene based foams leaving you with a gooey mess.
A thing to watch with composite structures is the skin weights. 0.062" diamond plate is the thinnest I know of. for a 4'x8' equivalent sheet that is 29 lbs. The thing is that is way overkill strength wise except for denting strength. For a surface you will be putting heavy stuff on it may be good to have that strength. The bottom sheet on a composite could be 0.020" thick as it mostly needs tension skin strength.
Another issue with composite structures is the loading from the vertical support walls to the composite sheet. Using a flange at the top of the wall may be needed to spread the load. To calculate what you need, take the compression strength of the foam, divide it by two (safety factor), then multiply by the area of the top of the wall. A typical blue or pink insulation foam strength from a home store is only 30PSI. Divide by safety factor for 15PSI. For illustrative purposes lets use the top of a wall as 4' long x 1" wide for only 48 sq in. That gives us 48 * 15 = 720 lbs. Sounds good until you realize that the aluminum skins are only really tension members keeping the foam from bending and have near zero ability to spread the load. So, if you sit up directly over a support wall, your weight is being supported by a foot long section of the support wall. So that leaves us with only 180 lbs load bearing to support your butt. We could add a flange to make the wall wider. Making it 2" wide gives use 360lbs load bearing which is much better. OK, lets try a structural foam, Last-A-Foam FR-7100 (Available at Aircraft Spruce). At 6lbs per cubic foot it is 77lbs per sq inch. Running the calculations for it, a single 1" wide 4' long wall could support 1386 lbs. That gives us 462lbs for when we sit up over a support wall.
As for how thick to make the sandwich. That is reliant on the shear strength of the foam, strength of the skins, and how wide of area you want to span. I'm not comfortable making a rule of thumb calculation for that as there are to many variables. I will mention that industrial made composite boards have supported an adult male's weight with only 1" core thickness over a 4' span.
Honeycomb cores work in a very similar way to foam cores, but the skins aren't as evenly supported and the cores have directionality for the structure resisting bending.
Another advantage of the structural foam is it has a greater ability to resist delaminating. This means the structure will handle greater abuse.
Insulation foams may also have plastic or foil skins that need removing before bonding. The plastic skins are used in manufacture to make them easier to make.
I'm no expert on composite foam structures, but the above is what I've gathered from all my reading up on them.
