I had another thought on cores for curved swords.
9.5mm diameter 6061 T6 (tempered) aluminium alloy rod.
I’ve seen crossbow prods (bows) made from this stuff and it’s very very strong.They also build airplanes from it, because it is strong, light and has excellent resistance to metal fatigue.
This aluminium alloy weighs 2.7g/cm3, so a 9.5mm diameter rod 1m long would weigh around 190g
Fiberglass varies in density depending on the glass/resin ratio.
Glass has a density of 2.6g/cm3
Resin 1.1-1.2g/cm3.
Rods, would probably be around 2g/cm3
So aluminium rod is maybe 50% heavier than fiberglass, but it can be curved and then tempered to remain in that shape.
Just a thought…
I’d be surprised if the yanks aren’t doing it. I know there are a ton of SCA fighters who make armour from it because it’s light and almost indestructible.