Unfortunately, my clarification, specifically as to the cause of the
Agusta109 main rotor blade separation is in error. In that particular case,
I was informed that at manufacture too much bonding material was applied to
a weight that is bonded inside of the spar to achieve balance to
manufacturing tolerances. That excess bonding material was "scraped" out
leaving a tooling mark that eventually led to the crack.

Now to briefly answer your questions:
A "Forging Lap" is a flap of metal that should not be present after a
forging or hammering type of process. Those spars are not forged, they are
extruded (pushed or pulled through a die). Typically, manufacturing defects
are not as blatent as to be seen by the naked eye, and many times are inside
of the spar requiring x-ray, eddy current, or some other form of
non-destructive detection.

Composite (meaning totally composite) main rotor blades do not have a metal
spar. Some newer composite main rotor blades incorporate a carbon fibre
reinforced plastic spar and are filled with a Nomex honeycomb material. The
blades are corrosion and damage resistant. Sorry for my error.