Composite stiffeners for aerospace vehicles

• US 8,720,825 B2
• Filed: 10/04/2010
• Issued: 05/13/2014
• Est. Priority Date: 03/31/2005
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Kismarton, Max U.
• Primary Examiner(s): Lee, Benjamin P
• Application Number:
  US12/897,742
• Publication Number:
  US 20110045232A1
• Time in Patent Office: 1,317 Days
• Field of Search: 244/129.1, 244/117.R, 244/119, 244/123.1, 244/123.8, 244/133, 244/132, 428/105, 428/107, 428/113, 428/109
• US Class Current: 244/129.1
• 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 65/564 hidden in the joint, e.g. dowels or Z-pins B29C65/603 takes precedence
• 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 70/202 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 70/207 arranged in parallel planes of fibres crossing at substantial angles
• 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: B29K 2707/04 Carbon
• CPC Class Codes: B29L 2031/3076 Aircrafts blades, propellers B29L2031/08
• CPC Class Codes: B32B 1/00 Layered products having a non-planar shape
• CPC Class Codes: B32B 2250/20 : All layers being fibrous or filamentary
• CPC Class Codes: B32B 2260/023 : Two or more layers
• CPC Class Codes: B32B 2260/046 : Synthetic resin
• CPC Class Codes: B32B 2262/106 : Carbon fibres, e.g. graphite fibres
• 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: B32B 5/26 : another layer next to it also being fibrous or filamentary relative arrangement of fibres or filaments of different layers B32B5/12
• CPC Class Codes: B32B 5/28 : impregnated with or embedded in a plastic substance not used
• CPC Class Codes: B64C 1/064 : Stringers; Longerons
• CPC Class Codes: B64C 1/12 : Construction or attachment of skin panels
• CPC Class Codes: B64C 2001/0072 : from composite materials
• 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

An aerospace vehicle includes a plurality of composite stiffeners. Each stiffener of the plurality has a stack of plies of reinforcing fibers. At least some of the plies in the stack have reinforcing fibers oriented at ±α with respect to an axis of primary loading, where α is between 2 and 12 degrees. At least some of the plies in the stack have reinforcing fibers oriented at ±β with respect to the axis of primary loading, where β is between 50 and 85 degrees.

Claims

1. An aerospace vehicle comprising a plurality of composite stiffeners, each stiffener of the plurality having a stack of plies of reinforcing fibers;

at least some of the plies in the stack having reinforcing fibers oriented at ±

α

with respect to an axis of primary loading, where α

is between 2 and 12 degrees;

at least some of the plies having reinforcing fibers oriented at ±

β

with respect to the axis of primary loading, where β

is between 50 and 85 degrees.

2. The vehicle of claim 1, further comprising a plurality of skin panels stiffened by the stiffeners, wherein the stiffeners include bases fastened to the skin panels by fasteners, whereby the fibers oriented at ±

α

suppress or delay ply splitting in the bases.

3. The vehicle of claim 1, wherein α

is between 2 and 8 degrees.

4. The vehicle of claim 1, wherein α

is between 3 and 5 degrees.

5. The vehicle of claim 1, wherein the reinforcing fibers oriented at ±

α

constitute at least 50% of the total number of fibers in each stiffener.

6. The vehicle of claim 1, wherein the stiffeners include webs, and wherein the fibers oriented at ±

β

are biased towards outer surfaces of the webs to increase stiffness in buckling and transverse bending.

7. The vehicle of claim 1, wherein the skin panels and the stiffeners include carbon fibers in a polymer matrix.

8. The vehicle of claim 1, wherein the vehicle includes a fuselage, wing assemblies and empennage;

and wherein the plurality of stiffeners are included in at least one of the fuselage, the wing assemblies and the empennage.

9. The vehicle of claim 1, wherein all fibers in the stack consist of the fibers oriented at ±

α and

±

β

; and

wherein 20-30% of the total fibers are oriented at ±

β

to reach bearing strength levels similar to traditional 0/+45/−

45/90 degree hard laminates.

10. An article comprising an aerospace vehicle stiffener, the stiffener including a base and a web, at least one of the base and web including a stack of plies of reinforcing fibers, at least 50% of the reinforcing fibers oriented at ±

α

with respect to an axis of primary loading, where α

is between 2 and 12 degrees.

11. The article of claim 10, wherein the base has fastener apertures, whereby the reinforcing fibers in the base are oriented at ±

α

degrees to suppress or delay splitting caused by the fastener apertures.

12. The article of claim 10, wherein α

is between 2 and 8 degrees.

13. The article of claim 10, wherein α

is between 3 and 5 degrees.

14. The article of claim 10, wherein the reinforcing fibers oriented at ±

α

constitute 100% of the total number of fibers in the stack.

15. The article of claim 10, wherein the stack further includes plies of reinforcing fibers oriented at ±

β

degrees with respect to the axis of primary loading, where β

is between 50 and 85 degrees.

16. The article of claim 15, wherein the fibers oriented at ±

β

are biased towards outer surfaces of the webs to increase stiffness in buckling and transverse bending.

17. The article of claim 10, wherein the reinforcing fibers in the stack include carbon fibers embedded in a polymer matrix.

18. An article comprising an aerospace vehicle stiffener, the stiffener including a base and a web, the web including plies of reinforcing fibers for providing strength in tension and compression along an axis of primary loading, the web also including plies of reinforcing fibers oriented at ±

β

degrees with respect to the axis of primary loading, where β

is between 50 and 85 degrees, wherein the fibers oriented at ±

β

degrees are biased towards outer surfaces of the web to increase stiffness in buckling and transverse loading.

19. The article of claim 18, wherein the reinforcing fibers for providing strength in tension and compression are oriented at ±

α

with respect to the axis of primary loading, where α

is between 2 and 12 degrees.

20. The article of claim 18, wherein the reinforcing fibers are carbon fibers embedded in a polymer matrix.