A stringer beam joint structure of an aircraft formed from fiber-reinforced composites includes a wing and a wing box. The wing is joined to the wing box at a side of a joint structure. The wing and the wing box each includes a lower skin. A plurality of stringers is coupled to the lower skin and all made of fiber-reinforced composites. A first end of at least one of the plurality of stringers at the side of the joint structure features a web cutout with a taper formed in the base flange that spans longitudinal to the respective stringer and the taper located at the end of each respective stringer, where the taper runs from a knife edge of a base flange of the respective stringer to a full height of the base flange. The tapered surface of the base flange is contiguous with an edge of the web cutout.