A type of material made from two or more things you wouldn't ordinarily think of putting together.
Trees are cellulose held in a matrix of lignin, a goopy natural compound that glues cellulose fibers in place and adds rigidity.
Bamboo, though really a grass, is similar.
A bright idea in early engineering was to mix straw and mud to make bricks stronger. This worked but had disadvantages for backpacking, which wasn't even invented for several thousand years because it would have been so much too heavy like that.
A later form of composite was sand and gravel mixed with portland cement, and you know where that got us. Right -- skateboard parks.
Fiberglass (glass fibers woven together and glued into mats with plastic resin) comes closer to being useful for backpacking, but it wasn't until carbon fiber fabrics got mixed with epoxy resins that we were able to buy really good fishing rods.
Backpack frames have seen some of this but not too much so far.
As prices come down, new composites are developed, and as designers get smarter we might get better pack frames.
Meanwhile, clever use of new ideas in wood composites (plywood) might do as well, and be biodegradable too.
Back to square one.
Ah, life. It bites.