The ornamental design for structural panel, as shown and described.
FIG. 1 is a top perspective view of a first embodiment of the structural panel of the present invention with a break-away to illustrate the continuous nature of the internal walls and to illustrate an indeterminant length feature of the present invention; also the rear, lengthwise view, the left end view and the bottom view are the same as the corresponding illustrated front, lengthwise view, the illustrated right end view and the illustrated top view of FIG. 1;
FIG. 2 shows a front elevational view of the structural panel shown in FIG. 1;
FIG. 3 top perspective view of a second embodiment of the structural panel of the present invention with a break-away to illustrate the continuous nature of the internal walls and to illustrate an indeterminant length feature or the present invention; also the rear, lengthwise view, and the left end view are the same as the corresponding illustrated front, lengthwise view and the illustrated right end view (and vice versa with respect to the illustrated interior surfaces of the left end protrusion and the non-fully illustrated interior surface of the right end protrusion); and the bottom view is the same as that of the first embodiment; and,
FIG. 4 shows a front elevational view of the structural panel shown in FIG. 3.
The present invention includes within its scope a range opaqueness non-transparent, translucent and transparent.