Stringer and associated composite structure and method for reinforcing a base structure

A composite structure comprising:

• a base structure;
• and
• a stringer connected to the base structure, the stringer comprising:
• a first stiffener member extending along a stringer elongation path, wherein:
• the first stiffener member comprises a first flange portion, a first web portion, and a first transition portion extending between the first flange portion and the first web portion;
• the first stiffener member is formed from a first composite material comprising a first woven fabric reinforcement material;
• and
• the first flange portion is connected to the base structure;
• a second stiffener member extending along the stringer elongation path, wherein:
• the second stiffener member comprises a second flange portion, opposed to and spaced away from the first flange portion, a second web portion, opposed to and spaced apart from the second web portion, and a second transition portion, extending between the second flange portion and the second wen portion and opposed to and spaced away from the first transition portion;
• the second stiffener member is formed from a second composite material comprising a second woven fabric reinforcement material;
• and
• the second flange portion is connected to the base structure;
• and
• an intermediate stiffener member extending along the stringer elongation path, wherein:
• the intermediate stiffener member is formed from a third composite material comprising unidirectional reinforcement fibers;
• an entirety of the intermediate stiffener member is positioned between the first web portion and the second web portion and is offset from the base structure by a non-zero offset distance such that a transition region is formed between the at least the intermediate stiffener member, the first transition portion, the second transition portion, and the base structure;
• the intermediate stiffener member is connected to the first web portion and to the second web portion;
• and
• a filler member extending along the stringer elongation path, wherein:
• the filler member fills an entirety of the transition region;
• the filler member is formed from a fourth composite material comprising chopped reinforcement fibers;
• and
• the filler member is connected to at least the intermediate stiffener member, the first transition portion, the second transition portion, and the base structure.

A method for reinforcing a base structure comprising:

• connecting to the base structure a stringer, the stringer comprising:
• a first stiffener member extending along a stringer elongation path, wherein:
• the first stiffener member comprises a first flange portion, a first web portion, and a first transition portion extending between the first flange portion and the first web portion;
• and
• the first stiffener member is formed from a first composite material;
• a second stiffener member extending along the stringer elongation path, wherein:
• the second stiffener member comprises a second flange portion, a second web portion, and a second transition portion extending between the second flange portion and the second web portion;
• the second stiffener member is formed from a second composite material;
• the first web portion is opposed to and is spaced apart from the second web portion;
• the first transition portion is opposed to and is spaced away from the second transition portion;
• the first flange portion is opposed to and is spaced away from the second flange portion;
• and
• the first flange portion and the second flange portion are connected to the base structure;
• an intermediate stiffener member extending along the stringer elongation path, wherein:
• the intermediate stiffener member is formed from a third composite material;
• an entirety of the intermediate stiffener member is positioned between the first web portion and the second web portion;
• the intermediate stiffener member is connected to the first web portion and the second web portion;
• and
• the intermediate stiffener member is offset from the base structure by a non-zero offset distance such that a transition region is formed between at least the intermediate stiffener member, the first transition portion, the second transition portion, and the base structure;
• and
• a filler member extending along the stringer elongation path, wherein:
• the filler member fills an entirety of the transition region and is connected to at least the intermediate stiffener member, the first transition portion, the second transition portion, and the base structure;
• and
• the filler member comprises a fourth composite material.