Mainline was Kevlar strands down the length of the stick, through a metal tube, and "plastic" was poured into it, creating a rod when cured. The taper, butt and tip were then ground into it. Wonderful sticks IMO, I was sad to see them go in 2001 or so. They could do a lot of different looks with the sticks, some remarkably wood-like.
Trick made a carbon fiber stick, I don't think it made it to market.
I do recall some actual fiberglass timbale sticks in the '70s, but not regular sticks. Will have to check my collection, I have almost every synthetic ever made. :)