If you can find a way of submerging the whole assembly in hot water and keep it hot for an extended period, then it will work. But I daresay that means keeping it at a consistent temperature for at least an hour - possibly longer. Not sure what the convection properties of PLA are, but I would be starting at an hour.

My wife told me
I had print a phone holder from PLA for my car  that had encounter a warped perception of sunlight through my sealed car cabin .It can no longer accommodate any phone

I FAILED MISERABLY !!! Unfortunately although ambient temperature was 22C-71,5F the exothermic reaction of resin was enough to soften PLA and vacuum pump did its job and squished the whole layup . My mistake was also that i printed my core thin wall (1,6mm ) . I don't want to try PLA one more time with thicker wall , cause if the heat from the resin is high (60C-140F) the core will soften no mater what.
So  i came to the decision i wanted to avoid in the first place : ABS  and dilution with acetone .
This time i will print a core with ABS  stick a layer of  packing tape on its surface and then wrap this frame with CF and vacuum bag it .After curing i will pour acetone in the core to dissolve the core .The packing tape is to unstick the core from the CF shell as soon as possible .
Any thoughts?
Here some pictures

ABS will be better, but you will need a fair amount of acetone to melt out the print and even then you will probably still have bits stuck inside.

Im looking at using PC Polycarbonate filament next as its good for about 120degrees which opens it up to some of the more common prepregs, there are other options like HIPS material that you can use which is dissolved using limonene.

Or even BVOH could be a good option as its water soluble.

https://www.verbatim.com/prod/3D-printing/bvoh-filament-1.75mm/bvoh-filament-1.75mm-500g-reel-natural-sku-55901/

My first print was is HIPS but i cant find a limonene supplier that ships in Greece , Next PVA is semi flexible and very expensive 80 E/Kgr .I have never heard of BVOH its good to know about it but at 160E/Kgr is out of budget for me. I have never print PC sounds promising , i guess you plan to print a mold ... since for core use i don't know any way to dissolve it.
Anyway thanks for your insight.