Stringer transition and method for producing composite parts using the same

A composite aircraft structure, comprising:

• a skin member;
• and
• a stringer mounted to the skin member, the stringer transitioning from a hat section to a dual-blade section and including:
• a base portion;
• and
• a first web and a second web extending outwardly from the base portion, the orientation of the first and second webs relative to the base portion transitioning within an angle transition zone having opposing first and second angle zone ends, at least one of the first and second webs defining a non-perpendicular orientation at the first angle zone end.

A method of forming a stringer having a base portion and a pair of first and second webs extending outwardly therefrom, the method comprising the steps of:

• forming a base laminate by laying up base plies on a base mold;
• increasing the quantity of the base plies incrementally within a ply transition zone;
• laying up primary plies on a cure mold having cure mold side walls transitioning from a first angle to a second angle within an angle transition zone;
• forming a primary laminate by decreasing the quantity of primary plies incrementally within the ply transition zone in correspondence with the incremental increase in base plies;
• laying up wrap plies about a mandrel formed complementary to the cure mold;
• forming a wrap laminate by increasing the quantity of wrap plies incrementally within the ply transition zone in correspondence with the incremental decrease in primary plies and incremental increase in base plies;
• inserting the wrap laminate into the primary laminate;
• placing at least one of a first and second noodle along the wrap laminate and primary laminate;
• adding the base laminate to the wrap laminate and primary laminate;
• co-curing the base laminate, wrap laminate and primary laminate to form the stringer;
• and
• forming an opening in the stringer by removing at least a portion of a cap of the stinger.