Here's a broken armrest bracket mostly cracked. I reinforced it with fiberglass and polymer resin.

I wrapped it with paper to avoid coats on unwanted area, then brushed it with wax to prevent the resin from sticking.

Brushed resin with fiberglass on cracks.. I didn't color the resin so it looks kinda crappy.

Another coat of resin then followed by fiberglass chop strand mat. A second pass of resin to even out the fiberglass chop stand.