You said the rod was 1.5" diameter.
To use it for a core you will need to shape it down most likely to .625".
That WILL male a lot of carbon fiber dust and if you get that into your lungs it is not good news.
I know of a wind surfboard maker here that used carbon fiber to make parts for his boards. He would grind and sand it to shape.
He dont do that anymore.
In fact he dont do much of anything anymore.
I see the rod can be bought as .625" diameter.
That would be the way to go.
Yea, I know. When we worked with it, we had to have proper PPE to cut or do anything like that with it. I was thinking maybe gundrill a butt and put a piece of .500 in it to just see what it would do. No idea what would happen, but would be fun to try and see what kind of hit it had.
And no, I would not recommend cutting, machining, drilling this stuff without the proper protective equip....its nasty stuff for your insides.