If you want to know more about HPL you'll be better served by looking for information about countertop laminate such as Formica or Wilsonart material.
You can turn standard countertop laminate over and the backside offers a fairly attractive alternative for instrument body material. I've actually used it for fret board top surface and it performs well. It just doesn't look great IMHO.
What it is and how it's made:
https://www.compositepanel.org/produ...ure-laminates/