Umbrellas - particularly cheap umbrellas - break, due to wind or misadventure, and when enough struts have failed, they usually get thrown away.
This is a shame, the materials could be useful. The fabric, in particular, is often colourful, and reasonably sturdy.
Carbon fibre is a very tough composite
material, made from sheets of woven carbon fibre laminated together with epoxy resin. Pre-formed boards and rods are available in many thicknesses. For many purposes however, the inherent strength would be overkill, and the inherent cost of the raw materials makes the product expensive enough to be prohibitive.
I propose that broken umbrellas be salvaged, and used to produce strong and stylish composite material, in a similar manner to carbon fibre sheet.
The umbrella fabric would be separated, cleaned, and cut into smaller fragments (I envisage quarters). A single sheet of base material would be used to form a contiguous central core. Umbrella fabric would spread several layers thick on both sides, soaked in epoxy resin, pressed together tightly, and the entire assembly allowed to cure.
The artisanal nature of the process would lend itself to interesting designs, and at moderate scale curved sheets could readily be prepared to suit those awkward connecting areas in a stylish way.