What about the heavy hard rubber floor mats found in maintenance shops or horse stalls? I'm pretty sure you can pick em up in tractor supply but i'd be lying if I had an idea on price
I thought about the rubber mats. Did not know if dogs would chew them or not.
I would just use plywood or MDF. Then make a frame out of angle iron (steel) weld the hinges to the angle frame. Stain and seal the wood and attach it to the frame with bolts to the frame. Then you can take it apart and re-paint it if it starts to look bad or replace the wood.
Do you have chain link left over? What about cutting a piece of treated plywood the size of you door opening. Then take a piece of chain link or other type of 4x4 or 2x4 Galv panel and cut it the same size as the door (maybe a tad bit smaller) using a bolt cutter. Attach hinges and staple fencing to both sides of plywood.
I would think this will make door sturdy and discourage chewing, especially if you get the 2x4 Galv panel. Just make sure that the sharp edges of the panel do not cut or scrath dogs back when they walk through. You may put a rubber sweep type end on the bottom of the door.
Thinking this might be the way to go, except use facial metal to cover it with. Rent a brake to bend it with.
Thanks & please keep the ideas coming.
Just got the bathroom in & working on the plumbing. The inside is climate controlled. Still need to build a work bench & some closets for storage. Will take some pics. when I am done.