They built it with fiberglass...
Recall the story of the marine helicopters falling out of the sky when their blades de-laminated in flight....
Was eventually traced to a laminator who went out at lunch time and re-did her nail polish.
It was actually of a carbon fiber manufacturer. Never tested for the depth planned.
When I flew, our first blades were metal skinned, very subject to damage except the leading edge. Fiberglass blades were a huge improvement. I’m sure some of the early blades delaminated, but not 79-96.