I claim the ornamental design for a fan blade, as shown and described.
FIG. 1 is a top perspective view of a fan blade of the present invention;
FIG. 2 is a front view thereof;
FIG. 3 is a first side view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a is a reduced perspective view thereof shown in an environmental use.
The broken line showing of the fan blade in use is included for the purpose of illustrating environmental structure and forms no part of the claimed design.