Composite skin and stringer structure and method for forming the same

• US 20060243860A1
• Filed: 04/28/2005
• Published: 11/02/2006
• Est. Priority Date: 04/28/2005
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Kismarton, Max U.
• Granted Patent: US 8,444,087 B2
• Time in Patent Office: Days
• US Class Current: 244/132
• CPC Class Codes: B29C 65/562 using extra joining elements, i.e. which are not integral with the parts to be joined using plastic snap elements B29C65/58; using plastic rivets B29C65/601
• CPC Class Codes: B29C 66/112 Single lapped joints
• CPC Class Codes: B29C 66/1122 Single lap to lap joints, i.e. overlap joints B29C66/45, B29C66/472, B29C66/52272 take precedence
• CPC Class Codes: B29C 66/131 Single flanged joints, i.e. one of the parts to be joined being rigid and flanged in the joint area
• CPC Class Codes: B29C 66/474 said single elements being substantially non-flat
• CPC Class Codes: B29C 66/524 Joining profiled elements
• CPC Class Codes: B29C 66/721 Fibre-reinforced materials B29C66/729 takes precedence
• CPC Class Codes: B29C 66/7212 characterised by the composition of the fibres
• CPC Class Codes: B29C 66/72141 Fibres of continuous length
• CPC Class Codes: B29C 70/228 the structure being stacked in parallel layers with fibres of adjacent layers crossing at substantial angles
• CPC Class Codes: B29C 70/30 Shaping by lay-up, i.e. applying fibres, tape or broadsheet on a mould, former or core; Shaping by spray-up, i.e. spraying of fibres on a mould, former or core
• CPC Class Codes: B29K 2101/00 Use of unspecified macromolecular compounds as moulding material use of unspecified rubbers B29K2021/00
• CPC Class Codes: B29K 2307/00 Use of elements other than metals as reinforcement
• CPC Class Codes: B29K 2307/04 Carbon
• CPC Class Codes: B29L 2031/3076 Aircrafts blades, propellers B29L2031/08
• CPC Class Codes: B64C 1/064 Stringers; Longerons
• CPC Class Codes: B64C 1/12 Construction or attachment of skin panels
• CPC Class Codes: B64C 3/182 Stringers, longerons
• CPC Class Codes: B64C 3/26 Construction, shape, or attachment of separate skins, e.g. panels
• CPC Class Codes: Y02T 50/40 Weight reduction
• CPC Class Codes: Y10T 428/24124 : Fibers

Abstract

Composite stringer and skin structures and methods for forming the same are disclosed. In one embodiment, a composite stringer and skin structure includes a polymer-based elongated stringer portion having reinforcing fibers positioned in a plurality of adjacent plies, a first portion of the reinforcing fibers being oriented at a relatively shallow angle relative to a selected reference direction, and a second portion of the reinforcing fibers being oriented at a relatively broad angle relative to the selected reference direction. A polymer-based and fiber reinforced skin member adjoins the stringer portion, and an adhesive material is interposed between the stringer portion and the skin member.

Claims

1. A composite stringer and skin structure, comprising:

a polymer-based elongated stringer portion having reinforcing fibers positioned in a plurality of adjacent plies, a first portion of the reinforcing fibers being oriented at a relatively shallow angle relative to a selected reference direction, and a second portion of the reinforcing fibers being oriented at a relatively broad angle relative to the selected reference direction;

a polymer-based and fiber-reinforced skin member that adjoins the stringer portion; and

an adhesive material interposed between the stringer portion and the skin member.

2. The composite stringer and skin structure of claim 1, wherein the first portion of the reinforcing fibers are oriented at angles that range in magnitude between approximately about zero degrees and approximately about twenty degrees, and the second portion of the reinforcing fibers are oriented at angles that range in magnitude between approximately about forty-five degrees and approximately about ninety degrees.

3. The composite stringer and skin structure of claim 2, wherein the first portion of the reinforcing fibers are oriented at angles of approximately about five degrees, and the second portion of the reinforcing fibers are oriented at angles of approximately about sixty-five degrees.

4. The composite stringer and skin structure of claim 1, wherein the stringer portion and the skin member are comprised of reinforcement fibers having more than one modulus.

5. The composite stringer and skin structure of claim 1, wherein the stringer portion comprises a web portion that is oriented approximately perpendicular to the skin member, and positioned between a first flange portion and an opposing second flange portion that substantially abuts the skin member.

6. The composite stringer and skin structure of claim 5, wherein at least one of a depth of the web portion and a respective width of the first and second flange portions varies along a span of the structure.

7. The composite stringer and skin structure of claim 1, wherein the first layer and the second layer comprise approximately about eighty percent of the stringer portion and wherein the third layer and the fourth layer comprise approximately about twenty percent of the stringer portion.

8. The composite stringer and skin structure of claim 7, wherein the reinforcing fibers include carbon fibers having a modulus of at least about 40 M-lbs. per square inch.

9. The composite stringer and skin structure of claim 1, wherein the skin member comprises a first layer with reinforcing fibers substantially aligned with the selected reference direction, a second layer with reinforcing fibers oriented substantially perpendicular to the selected reference direction, a third layer with reinforcing fibers oriented at an angle α

relative to the reference direction and a fourth layer with reinforcing fibers oriented at an angle −

α

relative to the reference direction.

10. The composite stringer and skin structure of claim 7, wherein the angle α

is approximately about forty-five degrees, and the reinforcing fibers in the second, third and fourth layers include fibers having a modulus of at least about 50 M-lbs. per square inch.

11. The composite stringer and skin structure of claim 9, wherein the wherein the first layer comprises approximately about ten percent of the skin member, the second layer comprises approximately about ten percent of the skin member, and the third layer and the fourth layer comprise approximately about eighty percent of the skin member.

12. The composite stringer and skin structure of claim 1, wherein the first portion of the reinforcing fibers includes a first layer and a second layer, and the second portion includes a third layer and a fourth layer, further wherein the stringer portion further comprises a first layer group, a second layer group, a third layer group and a fourth layer group, wherein each layer group includes five adjacent layers selected from the first layer, the second layer, the third layer and the fourth layer.

13. The composite stringer and skin structure of claim 12, wherein the first layer group and the fourth layer group include the third layer interposed between a selected pair of the first and second layers.

14. The composite stringer and skin structure of claim 12, wherein the second layer group and the third layer group includes the fourth layer interposed between a selected pair of the first and second layers.

15. The composite stringer and skin structure of claim 1, further comprising at least one fastener that projects through a selected portion of the stringer portion and the skin member.

16. A method of fabricating a stringer and skin structure, comprising:

forming a stringer portion by repetitively bonding fiber-reinforced layers of a polymer material to impart a predetermined shape to the stringer portion;

forming a skin member by repetitively bonding fiber reinforced layers of a polymer material to impart a predetermined shape to the skin member; and

adhesively joining the stringer portion to the skin member.

17. The method of claim 16, wherein forming a stringer portion comprises forming a plurality of adjacent plies that include a first portion having the reinforcing fibers oriented at a relatively shallow angle relative to a selected reference direction, and a second portion having the reinforcing fibers oriented at a relatively broad angle relative to the selected reference direction.

18. The method of claim 17, wherein forming a plurality of adjacent plies further comprises orienting the reinforcing fibers in first the portion at angles that range in magnitude between approximately about zero degrees and approximately about twenty degrees, and orienting the reinforcing fibers in the second portion at angles that range in magnitude between approximately about forty-five degrees and approximately about ninety degrees.

19. The method of claim 16, wherein forming a skin member comprises forming a first layer with reinforcing fibers substantially aligned with a selected reference direction, forming a second layer with reinforcing fibers oriented substantially perpendicular to the selected reference direction, forming a third layer with reinforcing fibers oriented at an angle α

relative to the reference direction and a fourth layer with reinforcing fibers oriented at an angle −

α

relative to the reference direction.

20. The method of claim 16, wherein adhesively joining the stringer portion to the skin member further comprises curing at least one of the stringer portion and the skin member, interposing a film adhesive between the stringer portion and the skin member, and curing the film adhesive.

21. The method of claim 16, wherein adhesively joining the stringer portion to the skin member comprises interposing a paste adhesive between the stringer portion and the skin member.

22. The method of claim 16, further comprising forming at least one aperture that projects through a selected portion of the stringer portion and the skin member, inserting a fastener in the at least one aperture, and applying a predetermined torque to the fastener to generate a predetermined compressive force.

23. An aerospace vehicle, comprising:

a fuselage;

wing assemblies and an empennage operatively coupled to the fuselage; and

a composite stringer and skin structure positioned in at least one of the wing assemblies and the empennage, the composite stringer and skin structure further comprising;

a polymer-based elongated stringer portion having reinforcing fibers positioned in a plurality of adjacent plies, a first portion of the reinforcing fibers being oriented at a relatively shallow angle relative to a selected reference direction, and a second portion of the reinforcing fibers being oriented at a relatively broad angle relative to the selected reference direction;

a polymer-based and fiber reinforced skin member that adjoins the stringer portion; and

an adhesive material interposed between the stringer portion and the skin member.

24. The aerospace vehicle of claim 23, wherein the wherein the first portion of the reinforcing fibers are oriented at angles that range in magnitude between approximately about zero degrees and approximately about twenty degrees, and the second portion of the reinforcing fibers are oriented at angles that range in magnitude between approximately about forty-five degrees and approximately about ninety degrees.

25. The aerospace vehicle of claim 23, wherein the skin member comprises a first layer with reinforcing fibers substantially aligned with the selected reference direction, a second layer with reinforcing fibers oriented substantially perpendicular to the selected reference direction, a third layer with reinforcing fibers oriented at an angle α

relative to the reference direction and a fourth layer with reinforcing fibers oriented at an angle −

α

relative to the reference direction.