To add a bit to what Dave wrote, the 'one in twenty' Advisory Circular guidance (FAA, but EASA also accepts this method of compliance) specifies a 1/3rd disc - with infinite energy. You can't take any credit for shielding for the rotor disc fragments (also known as 'high energy debris'). Smaller bits - such as the blades and blade fragments - are 'low energy debris' and shielding credit can be taken.
There is a defined forward/aft trajectory range for both - IIRC it's +/- 3 deg for 'high energy' debris, and +/- 20 deg for 'low energy' debris (but I stand to be corrected - it's been a while since I worried this).