A method for fabricating a composite wing structural component for an aircraft is described. The method comprises extruding a filler material into each mold channel of a plurality of mold channels of a die to form a plurality of filler segments, removing the plurality of filler segments from the plurality of mold channels of the die, and arranging the plurality of filler segments in a space in the composite structural component, the space being defined by a radius of the composite structural component, such that the filler segments are in end-to-end contact. The method further comprises curing the plurality of filler segments in the space to fuse the plurality of filler segments.