Radius fillers for composite structures, composite structures that include radius fillers, and systems and methods of forming the same

A radius filler for a composite structure, wherein the composite structure includes a plurality of plies of composite material that converge within a transition region to define an elongate void space, wherein the plurality of plies of composite material defines a material property gradient of the transition region, wherein the material property gradient of the transition region includes a mathematical description of a variation in at least one material property with direction within the transition region, and further wherein the radius filler is configured to extend within the elongate void space, the radius filler comprising:

• a plurality of lengths of composite tape;
• wherein the plurality of lengths of composite tape includes a first set of plies that defines a first edge and a second set of plies that defines a second edge, and further wherein the first edge and the second edge are in contact with one another.