Used Tyres, locally available for free, can be easily cut up with a hand blade & a metal jig saw blade (for side wall metal tyre bead) to strengthen a plywood or metal shutter.
The tyre off cuts are screwed and / glued into raw plugs in the wall . Preferably bolted to the plywood
A Short Lesson in Building Effective Shutters
plywood hurricane shutters images
If there's no money for plywood , salvaged pallets could be used
The whole shutter counld be covered with over lapping tyre treads fo max strength, but weight would be heavy.
First ideas for total coverage layout
Perhaps a combination of the side walls & tread would work best . Side walls could be cut as complete circles & screwed to tread strips