maybe as a filler, either the fiberglas or resin (more than likely both) breaks down in sunlight.

I have a couple of home-made antennas that have fiberglass and Teflon parts that have been in the sun for nearly 40 years, The resin is gone from the outer layers of fiberglass, so from a distance they look pure white (you see the remaining glass). As long as you don't rub the glass off (the outer layer is no longer held in place by resin), the glass protects the interior resin, so the thing holds together. The main beam was originally a pole-vaulting pole (a tube), and the smaller parts were solid rod.

There is undoubtedly some degradation of the glass, but it is not obvious, as is the degradation of the resin.

The Teflon parts are visually unchanged - look and feel like new!.

Dick

kinda how the statue of liberty copper skin protects it. the patina acts as a protective coating.

What do you have? Did it hold contaminated fluids?

This is a valid point - how 'clean' is this fiberglass?

It was used to wrap aluminum air cylinders