Solid laminate stringer

• US 10,669,005 B2
• Filed: 02/27/2018
• Issued: 06/02/2020
• Est. Priority Date: 02/27/2018
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Cheng, Jiangtian, Schroeder, Ian E., Swanson, Gary D., Pham, Kanna M., Cregger, Samuel E., Spencer, Scott M.
• Primary Examiner(s): Thomas, Alexander S
• Application Number:
  US15/907,224
• Publication Number:
  US 20190263496A1
• Time in Patent Office: 826 Days
• CPC Class Codes: B29C 70/202 arranged in parallel planes or structures of fibres crossing at substantial angles, e.g. cross-moulding compound [XMC] B29C70/207 takes precedence
• CPC Class Codes: B29C 70/302 Details of the edges of fibre composites, e.g. edge finishing or means to avoid delamination
• CPC Class Codes: B29D 99/0005 Producing noodles, i.e. composite gap fillers, characterised by their construction
• CPC Class Codes: B29D 99/0014 provided with ridges or ribs, e.g. joined ribs
• CPC Class Codes: B29L 2031/3082 Fuselages
• CPC Class Codes: B29L 2031/3085 Wings
• CPC Class Codes: B32B 2605/18 Aircraft blades, propellers B32B2603/00
• CPC Class Codes: B32B 3/06 for securing layers together; for attaching the product to another member, e.g. to a support , or to another product, e.g. groove/tongue, interlocking
• CPC Class Codes: B32B 3/263 characterised by a layer having non-uniform thickness
• CPC Class Codes: B32B 5/12 characterised by the relative arrangement of fibres or filaments of different layers, e.g. the fibres or filaments being parallel or perpendicular to each other
• CPC Class Codes: B64C 1/064 Stringers; Longerons
• CPC Class Codes: B64C 2001/0072 from composite materials
• CPC Class Codes: B64C 3/182 Stringers, longerons
• CPC Class Codes: Y02T 50/40 Weight reduction

Abstract

A solid laminate stringer includes a base segment that forms a first generally trapezoidal cross section. The solid laminate stringer also includes a transition segment abutting the base segment, with concave sides that are continuous with the sides of the base segment. The solid laminate stringer also includes a top segment abutting the transition segment, where the top segment forms a second generally trapezoidal cross section with sides that are continuous with the concave sides of the transition segment. The solid laminate stringer also includes a first overwrap layer covering the top segment, the transition segment, and at least a portion of the base segment. The solid laminate stringer also includes a second overwrap layer overlapping at least a portion of the first overwrap layer covering the base segment.

Claims

1. A solid laminate stringer for use in an aircraft, the stringer comprising:

a base segment comprising a first plurality of plies of reinforcement material, wherein the base segment forms a first generally trapezoidal cross section with sides having a first slope angle with respect to a first stacked ply of the base segment;

a transition segment abutting the base segment, the transition segment comprising a second plurality of plies of reinforcement material, wherein the transition segment forms a cross section having concave sides that are continuous with the sides of the base segment;

a top segment abutting the transition segment, the top segment comprising a third plurality of plies of reinforcement material, wherein the top segment forms a second generally trapezoidal cross section with sides that are continuous with the concave sides of the transition segment, and wherein the sides have a second slope angle with respect to the first stacked ply of the base segment that is greater than the first slope angle;

a first overwrap layer comprising at least one ply of reinforcement material, wherein the first overwrap layer covers the top segment, the transition segment, and at least a portion of the base segment; and

a second overwrap layer comprising at least one ply of reinforcement material, wherein the second overwrap layer overlaps at least a portion of the first overwrap layer covering the base segment.

2. The solid laminate stringer of claim 1, wherein the at least one ply of reinforcement material of the first overwrap layer is arranged with respect to an axial direction of the stringer at one or more angles within ranges of between about 15 to 25 degrees and between about −

15 to −

25 degrees.

3. The solid laminate stringer of claim 1, wherein the top segment comprises a top surface that joins each side of the top segment at a convex arc having a radius of at least about 0.15 inches.

4. The solid laminate stringer of claim 1, wherein the concave sides of the transition segment comprise one or more arcs having a radius of at least about 0.25 inches, and wherein the second plurality of plies of reinforcement material comprises plies arranged with respect to an axial direction of the stringer at angles within ranges of between about 25 to 35 degrees and between about −

25 to −

35 degrees, or at angles including 0 degrees, 45 degrees, −

45 degrees and 90 degrees, wherein about 42% to 48% of the second plurality of plies of reinforcement material are arranged at 0 degrees.

5. The solid laminate stringer of claim 1, wherein the second slope angle of the top segment is within a range of between about 60 to 75 degrees, and wherein the third plurality of plies of reinforcement material comprises plies arranged with respect to an axial direction of the stringer at angles within ranges of between about 20 to 35 degrees and between about −

20 to −

35 degrees, or at angles including 10 degrees, −

10 degrees, 60 degrees, and −

60 degrees, or at angles including 0 degrees, 45 degrees, −

45 degrees and 90 degrees, wherein about 45% to 60% of the third plurality of plies of reinforcement material are arranged at 0 degrees.

6. The solid laminate stringer of claim 1, wherein the first slope angle of the base segment is within a range of between about 10 to 20 degrees, and wherein the first plurality of plies of reinforcement material comprises plies arranged with respect to an axial direction of the stringer at angles including 0 degrees, 45 degrees, −

45 degrees and 90 degrees, wherein about 38% to 44% of the first plurality of plies of reinforcement material are arranged at 0 degrees.

7. The solid laminate stringer of claim 6, wherein the top segment further comprises a cap charge abutting the third plurality of plies of reinforcement material, wherein the cap charge comprises a fourth plurality of plies of reinforcement material, wherein the fourth plurality of plies of reinforcement material are arranged with respect to the axial direction of the stringer at angles that are substantially the same as the angles of the first plurality of plies of reinforcement material.

8. The solid laminate stringer of claim 7, wherein an arrangement of the first, second, third and fourth plurality of plies with respect to the axial direction of the stringer is approximately symmetric about a line of symmetry between the base segment and the cap charge, wherein a plurality of terminating plies are successively terminated in the axial direction of the stringer, approximately at the line of symmetry, such that a height of the stringer is reduced along the axial direction of the stringer.

9. A method for fabricating a solid laminate stringer of a structural system, the method comprising:

laying up a base segment of the stringer onto a surface, wherein laying up the base segment comprises stacking a first plurality of plies of reinforcement material such that the base segment forms a first generally trapezoidal cross section with sides having a first slope angle with respect to the surface;

laying up a transition segment of the stringer abutting the base segment, wherein laying up the transition segment comprises stacking a second plurality of plies of reinforcement material such that the transition segment forms a cross section having concave sides that are continuous with the sides of the base segment;

laying up a top segment of the stringer abutting the transition segment, wherein laying up the top segment comprises stacking a third plurality of plies of reinforcement material such that the top segment forms a second generally trapezoidal cross section that is continuous with the transition segment, with sides having a second slope angle with respect to the surface that is greater than the first slope angle;

laying up a first overwrap layer, wherein laying up the first overwrap layer comprises stacking at least one ply of reinforcement material over the top segment, the transition segment, and at least a portion of the base segment;

laying up a second overwrap layer, wherein laying up the second overwrap layer comprises stacking at least one ply of reinforcement material such that the second overwrap layer overlaps at least a portion of the first overwrap layer covering the base segment, and such that the second overwrap layer covers at least a portion of the surface adjacent to the base segment; and

simultaneously curing the base segment, the transition segment, the top segment, the first overwrap layer, and the second overwrap layer.

10. The method of claim 9, wherein laying up the transition segment further comprises:

stacking the second plurality of plies of reinforcement material such that the concave sides of the transition segment comprise one or more arcs having a radius of at least about 0.25 inches; and

arranging the second plurality of plies of reinforcement material with respect to an axial direction of the stringer at angles within ranges of between about 25 to 35 degrees and between about −

25 to −

35 degrees, or at angles including 0 degrees, 45 degrees, −

45 degrees and 90 degrees, wherein about 42% to 48% of the second plurality of plies of reinforcement material are arranged at 0 degrees.

11. The method of claim 9, wherein laying up the top segment further comprises:

stacking the third plurality of plies of reinforcement material such that the second slope angle of the top segment is within a range of between about 60 to 75 degrees; and

arranging the third plurality of plies of reinforcement material with respect to an axial direction of the stringer at angles within ranges of between about 20 to 35 degrees and between about −

20 to −

35 degrees, or at angles including 10 degrees, −

10 degrees, 60 degrees, and −

60 degrees, or at angles including 0 degrees, 45 degrees, −

45 degrees and 90 degrees, wherein about 45% to 60% of the third plurality of plies of reinforcement material are arranged at 0 degrees.

12. The method of claim 9, wherein laying up the base segment further comprises:

stacking the first plurality of plies of reinforcement material such that the first slope angle of the base segment is within a range of between about 10 to 20 degrees; and

arranging the first plurality of plies of reinforcement material with respect to an axial direction of the stringer at angles including 0 degrees, 45 degrees, −

45 degrees and 90 degrees, wherein about 38% to 44% of the first plurality of plies of reinforcement material are arranged at 0 degrees.

13. The method of claim 9, wherein the surface is an inner surface of a laminate skin of an aircraft component, wherein the method further comprises:

before laying up the base segment of the stringer, laying up the laminate skin of the aircraft component, wherein simultaneously curing the base segment, the transition segment, the top segment, the first overwrap layer, and the second overwrap layer further comprises simultaneously curing the laminate skin of the aircraft component.

14. The method of claim 13, wherein laying up the top segment of the stringer further comprises laying up a cap charge abutting the third plurality of plies of reinforcement material, wherein laying up the cap charge comprises stacking a fourth plurality of plies of reinforcement material in an arrangement with respect to an axial direction of the stringer that is substantially the same as an arrangement of the first plurality of plies of reinforcement material with respect to the axial direction of the stringer, and such that an arrangement of the first, second, third and fourth plurality of plies with respect to the axial direction of the stringer are approximately symmetric about a line of symmetry between the base segment and the cap charge.

15. The method of claim 14, further comprising:

successively terminating a plurality of terminating plies in the axial direction of the stringer, wherein each successive terminating ply is terminated a shorter axial distance from a runout end of the stringer, and wherein each terminating ply in the plurality of terminating plies is terminated approximately at the line of symmetry such that a height of the stringer is reduced along the axial direction; and

increasing a thickness of the laminate skin along the axial direction of the stringer as the height of the stringer is reduced.

16. The method of claim 15, wherein the laminate skin comprises an outer mold line, and wherein the structural system comprises an elastic center of gravity located a distance from the outer mold line of the laminate skin, and wherein the method further comprises:

laying up structural fill material on the inner surface of the laminate skin and adjacent to the stringer where the height of the stringer is reduced such that the distance from the outer mold line to the elastic center of gravity is approximately constant along the axial direction of the stringer.

17. A structural system comprising:

a laminate skin of an aircraft component, wherein the laminate skin comprises an inner surface;

a solid laminate stringer positioned on the inner surface of the laminate skin, the solid laminate stringer comprising;

a base segment comprising a first plurality of plies of reinforcement material, wherein the base segment forms a first generally trapezoidal cross section with sides having a first slope angle with respect to the inner surface of the laminate skin;

a transition segment abutting the base segment, the transition segment comprising a second plurality of plies of reinforcement material, wherein the transition segment forms a cross section having concave sides that are continuous with the sides of the base segment;

a top segment abutting the transition segment, the top segment comprising a third plurality of plies of reinforcement material, wherein the top segment forms a second generally trapezoidal cross section with sides that are continuous with the concave sides of the transition segment, and wherein the sides have a second slope angle with respect to the inner surface of the laminate skin that is greater than the first slope angle;

a first overwrap layer comprising at least one ply of reinforcement material, wherein the first overwrap layer covers the top segment, the transition segment, and at least a portion of the base segment; and

a second overwrap layer comprising at least one ply of reinforcement material, wherein the second overwrap layer overlaps at least a portion of the first overwrap layer covering the base segment, and wherein the second overwrap layer further covers at least a portion of the inner surface of the laminate skin adjacent to the base segment.

18. The structural system of claim 17, wherein the top segment further comprises a cap charge abutting the third plurality of plies of reinforcement material, wherein the cap charge comprises a fourth plurality of plies of reinforcement material, wherein the fourth plurality of plies of reinforcement material comprises an arrangement with respect to an axial direction of the stringer that is substantially the same as an arrangement of the first plurality of plies of reinforcement material with respect to the axial direction of the stringer.

19. The structural system of claim 18, wherein an arrangement of the first, second, third and fourth plurality of plies with respect to the axial direction of the stringer are approximately symmetric about a line of symmetry between the base segment and the cap charge, wherein a plurality of terminating plies are successively terminated in the axial direction of the stringer, approximately at the line of symmetry, such that a height of the stringer is reduced along the axial direction of the stringer, and wherein a thickness of the laminate skin is concurrently increased along the axial direction of the stringer.

20. The structural system of claim 19, wherein the laminate skin comprises an outer mold line, and wherein the structural system comprises an elastic center of gravity located a distance from the outer mold line of the laminate skin, and wherein the structural system further comprises:

structural fill material positioned on the inner surface of the laminate skin and adjacent to the stringer where the height of the stringer is reduced, such that the distance from the outer mold line to the elastic center of gravity is approximately constant along the axial direction of the stringer.