US Patent 9827737 Composite structural element and torsion box

This relates to a composite structural element, in particular a rib or a spar, specifically for use in a torsion box of an aircraft structure such as a vertical tailplane, wherein the structural element defines a coordinate system with a first axis “a” wherein the structural element comprises a substantially planar main section defining a coordinate system with a first axis “a” extending along the longitudinal axis “L” of the structural element and a second axis “b” extending perpendicular to said longitudinal axis “L” within the planar main section and defining an angle of +90° with the first axis “a”, wherein the structural element contains a lay-up of single plies consisting of a fiber-reinforced composite material with a substantially unidirectional fiber orientation.