There is no plastic lumber that is suitable for aircraft construction. Works great for decks, docks, outdoor furniture, fences and house trim. It is heavy and very flexible. Not suitable for framing, or structural use.
Not really,
I've been drawing up my dock/beach setup for a while, debated on using the low profile snap together floating docks where you just add decking, but with the synthetic decking instead of wood, that lasted about 3 conversations with local boat and home owners, way too bendy, heavy and expensive, plus face it, it's fake wood and looks like it, compared to pressure treated/marine grade it just sucks.
Same in for siding, once you get close, it's a coke bottle trying to look like a tree, and with our winters, if you even look at it cross, it cracks. If fema got out of trailers and started to build houses, they'd have plastic siding.
Same with outdoor chairs, all the plastic stuff doesn't last in our winters, but through a rock and you'll hit a real wood Adirondack chair that's probably older than I am.
Closest I'll get is a lvl beam
For me, it's wood, stone or metal.