COMPOSITE STRUCTURES EMPLOYING QUASI-ISOTROPIC LAMINATES

• US 20100233424A1
• Filed: 03/10/2009
• Published: 09/16/2010
• Est. Priority Date: 03/10/2009
• Status: Abandoned Application

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Dan-Jumbo, Eugene A., Keller, Russell L., Westerman, Everett A.
• Application Number:
  US12/401,541
• Publication Number:
  US 20100233424A1
• Time in Patent Office: Days
• US Class Current: 428/113
• 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: B29D 99/0014 provided with ridges or ribs, e.g. joined ribs
• CPC Class Codes: B29K 2995/0045 Isotropic
• CPC Class Codes: B29L 2031/3082 Fuselages
• CPC Class Codes: B32B 1/00 Layered products having a non-planar shape
• CPC Class Codes: B32B 2260/021 Fibrous or filamentary layer layers of natural mineral fibres or particles being impregnated in a plastic substance B32B19/02
• CPC Class Codes: B32B 2260/046 Synthetic resin
• CPC Class Codes: B32B 2262/106 Carbon fibres, e.g. graphite fibres
• CPC Class Codes: B32B 2307/50 having particular mechanical properties
• CPC Class Codes: B32B 2307/708 Isotropic
• CPC Class Codes: B32B 2307/718 Weight, e.g. weight per square meter
• CPC Class Codes: B32B 2605/00 Vehicles
• CPC Class Codes: B32B 2605/18 Aircraft blades, propellers B32B2603/00
• CPC Class Codes: B32B 27/06 as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to a layer of a particular substance B32B9/045; next to a bituminous or tarry layer B32B11/046; next to a water setting substance layer B32B13/12; next to a metal layer B32B15/08; next to a glass layer B32B17/10; next to a layer formed of natural mineral fibres or particles B32B19/045; next to a wood layer B32B21/08; next to a cellulosic plastic layer B32B23/08; next to a natural or synthetic rubber layer B32B25/08
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/18 characterised by the use of special additives
• CPC Class Codes: B32B 27/38 comprising epoxy resins
• CPC Class Codes: B32B 5/022 Non-woven fabric
• 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 5/22 characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed layer formed of natural mineral fibres or particles next to a foam layer B32B19/047, next to a layer made of particles B32B19/048, or next to a fibrous or filamentary layer B32B19/06; paper layer or cardboard layer next to a paper layer or cardboard layer B32B29/005, next to a foam layer B32B29/007, next to a fibrous or filamentary layer B32B29/02, or next to a particulate layer B32B29/04
• CPC Class Codes: B32B 5/24 : one layer being a fibrous or filamentary layer
• 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 7/12 : using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: B64C 1/068 : Fuselage sections
• CPC Class Codes: B64C 2001/0072 : from composite materials
• CPC Class Codes: Y02T 50/40 : Weight reduction
• CPC Class Codes: Y10T 428/24124 : Fibers

Abstract

A composite laminate comprises a stack of unidirectional fiber reinforced composite plies arranged in a fiber orientation sequence providing the laminate with quasi-isotropic properties.

Claims

1. A composite laminate, comprising:

a stack of unidirectional fiber reinforced composite plies arranged in a fiber orientation sequence providing the laminate with quasi-isotropic properties.

2. The composite laminate of claim 1, wherein adjacent plies in the stack have differing fiber orientations and Poisson'"'"'s ratios differing from each other by an amount generally in the range of approximately 15 to 40%.

3. The composite laminate of claim 1, wherein the adjacent plies include first and second groups of plies having fiber orientations differing from each other by at least approximately 45 degrees.

4. A composite structure having crack arrestment, comprising:

a first composite member; and

,

a second composite member joined to and reinforced by the first composite member, the second composite member including a laminated stack of composite plies each having unidirectional reinforcing fibers and a fiber orientation,

wherein at least certain adjacent plies in the stack have respective Poisson'"'"'s ratios which differ in an amount sufficient to arrest propagation of a crack in the second composite member.

5. The composite structure of claim 4, wherein the amount of difference in the Poisson'"'"'s ratios is generally in the range of approximately 15 to 40%.

6. The composite structure of claim 4, wherein the fiber orientations of the at least certain adjacent plies is approximately 45 degrees.

7. The composite structure of claim 4, wherein:

the first composite member is an aircraft frame, and

the second composite member is a fuselage skin covering the frame.

8. A composite airframe, comprising:

at least one stiffener; and

a skin joined to the stiffener, the skin including stacked plies of unidirectional fiber reinforced composite material wherein each of the of plies has a fiber orientation,

the plies being are stacked in a sequence of fiber orientations that alter the propagation path of a crack in the skin approaching the stiffener.

9. The composite airframe of claim 8, wherein:

the stiffener is a composite laminate,

the skin is joined to the stiffener by an adhesive bond.

10. The composite airframe of claim 8, wherein the fiber orientations of at least certain adjacent plies in the stack differ from each other at least approximately 45 degree.

11. The composite airframe of claim 8, wherein at least certain adjacent plies in the stack have Poisson'"'"'s ratios differing from each other by an amount generally in the range of approximately 15 to 40%.

12. A method of constructing a composite airframe having crack arrestment, comprising:

fabricating a composite frame member;

fabricating a composite skin, including laying up a stack of unidirectional fiber reinforced composite plies in a sequence of ply orientations that provide the skin with quasi-isotropic properties; and

joining the frame member to the skin.

13. The method of claim 12, wherein laying up the stack of plies includes orienting the adjacent plies such that the fiber orientations of the adjacent plies differ by at least approximately 45 degrees.

14. The method of claim 12, further comprising:

determining the level of mis-match in the Poisson'"'"'s ratios between adjacent plies in the stack that will result in the skin exhibiting the quasi-isotropic properties.

15. The method of claim 14, further comprising:

selecting the sequence of ply orientations that will result in the determined level of mis-match in the Poisson'"'"'s ratios.

16. The method of claim 12, wherein joining the frame member to the skin includes bonding the frame member to the skin.

17. A unitized composite airframe for aircraft, comprising:

a plurality of barrel-shaped composite frame members each formed of a fiber reinforced composite laminate; and

a composite skin bonded to the frame members, the skin including a plurality of laminated plies of unidirectional fiber reinforced polymer, wherein the plies are arranged in groups each having a fiber common fiber orientation, and adjacent ones of the groups have fiber orientations that differ by at least approximately 45 degrees and the adjacent groups of plies have a mis-match of Poisson'"'"'s ratios generally in the range of approximately 15 to 40%.

18. A method of constructing a composite airframe having crack arrestment, comprising:

fabricating a plurality of composite frame members;

fabricating a composite skin, including—

determining the level of mis-match in Poisson'"'"'s ratios between adjacent plies required to aid in the arrestment of a crack in the skin, and

laying up a stack of plies of unidirectional fiber reinforced composite plies in orientations that provide the determined level of mis-match in Poisson'"'"'s ratio; and

adhesively bonding the frame members to the skin.