Aerodynamically-stable airfoil spar

• US 5,269,657 A
• Filed: 10/22/1991
• Issued: 12/14/1993
• Est. Priority Date: 07/20/1990
• Status: Expired due to Fees

• Current Assignee: Marvin Garfinkle
• Original Assignee: Marvin Garfinkle
• Inventors: Garfinkle, Marvin
• Primary Examiner(s): Look, Edward K.
• Assistant Examiner(s): Verdier, Christopher M.
• Application Number:
  US07/780,807
• Time in Patent Office: 784 Days
• Field of Search: 416/225, 416/226, 416/229 R, 416/230 R, 416/230 A, 416/241 R, 416/134, 244/123, 244/124, 29/889, 29/889.7, 29/889.71
• US Class Current: 416/226
• CPC Class Codes: B29C 70/20 oriented in a single direction, e.g. roofing or other parallel fibres B29C70/083, B29C70/226 take precedence
• 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 70/865 completely encapsulated
• CPC Class Codes: B29D 99/0025 Producing blades or the like, e.g. blades for turbines, propellers, or wings
• CPC Class Codes: B29K 2995/0079 Torsion strength; Torsion stiffness
• CPC Class Codes: B29K 2995/0082 Flexural strength; Flexion stiffness
• CPC Class Codes: B29L 2031/082 Blades, e.g. for helicopters
• CPC Class Codes: B29L 2031/3085 Wings
• CPC Class Codes: B64C 11/26 Fabricated blades
• CPC Class Codes: B64C 2027/4736 from composite materials
• CPC Class Codes: B64C 27/473 Constructional features
• CPC Class Codes: B64C 3/185 Spars
• CPC Class Codes: Y02T 50/40 Weight reduction
• CPC Class Codes: Y10T 29/49337 Composite blade

Abstract

A structural spar is provided that provides beneficial flexural-torsional coupling to an airfoil so that flexural excursions of the airfoil induces torsion in the spar so as to change the pitch angle of the airfoil in such a manner as to the oppose the flexure, thereby ameliorating the excursion.

Claims

1. In a spar of the type having a neutral plane, a normal bending axis and a longitudinal axis, the method of applying a torsional-flexural coupling to said spar after it is bent comprising the steps of

creating a second bending axis which is skewed from said normal bending axis by providing at least two essentially helical windings that extend longitudinally along said spar, said essentially helical windings essentially mirror images of each other, said second bending axis being the actual bending axis of said spar,

thereby when said spar is bent the bending imparts a torsional-flexural coupling about said longitudinal axis,

whereupon said torsional-flexural coupling is applied over the length of said spar.

2. The method as defined in claim 1 wherein

said helical windings are comprised of resin impregnated filaments, and

curing said resins to bond said filaments into a unitary member.

3. The method as defined in claim 2 including the steps of

providing first and second core section, and

wrapping said helical windings around said sections.

4. The method as defined in claim 2 including the step of

wrapping the filaments in each winding in the same direction.

5. The method as defined in claim 2 including the steps of

providing both high modulus filaments and low modulus filaments, and

wrapping said high modulus filaments in one direction and wrapping said low modulus filaments in the opposite direction so that said low modulus filaments retain said high modulus filaments in their positions without changing the location of said actual bending axis.

6. The method as defined in claim 2 including the step of

varying the location of said neutral plane by providing helical windings of non-identical cross-section.

7. The method as defined in claim 6 wherein said step of providing helical windings of non-identical cross-section includes the step of

placing a different number of filaments in the different helical windings.

8. The method as defined in claim 6 wherein

said step of providing helical windings of non-identical cross-section includes the step of

placing a different types of filaments in the different helical windings.

9. The method as defined in claim 1 including the step of

providing an airfoil, and

including said spar within said airfoil, said spar being the principal load bearing member of said airfoil so that said torsional-flexural coupling provides an aerodynamic restoring force to oppose said bending.

10. The method as defined in claim 9 wherein

said airfoil is a fixed wing.

11. The method as defined in claim 9 wherein

said airfoil is a rotary wing.

12. The method as defined in claim 3 including the step of

removing said core sections after said resin is cured.

13. A spar of the type having a neutral plane, a normal bending axis and a longitudinal axis,

said spar comprising a core having a plurality of sections, and

an actual bending axis, said actual bending axis being skewed from said normal bending axis so that when said spar is bent a torsional-flexural coupling is induced about said longitudinal axis over the length of said spar.

14. A spar as defined in claim 13 including

filament plies around each of said core sections, the filaments in said plies being helically disposed and lying in essentially parallel relationship to each other, and

said core sections being joined so that said filament plies on each of said sections are a mirror image of the filament plies on the other section across said juncture.

15. A spar as defined in claim 14 wherein

said sections have non-identical cross-sections.

16. A spar as defined in claim 14 wherein

the neutral plane of said spar lies along said juncture of said sections.

17. A Spar as defined in claim 15 wherein

there are a different number of plies in each of said sections.

18. A spar as defined in claim 15 wherein

the moduli of the filaments comprising the plies on each of the sections is different.

19. A spar as defined in claim 14 including

filament plies extending longitudinally along said core to increase the strength of said spar.

20. The spar as defined in claim 14 wherein

said core is hollow to provide an internal storage space in said spar.

21. A spar as defined in claim 14 including

an airfoil, and

said spar comprises a load bearing member in said airfoil.

22. A spar as defined in claim 21 including

a plurality of said spars in said airfoil,

said spars being operative to provide redundant load bearing paths in said airfoil to thereby provide load bearing capability if there is physical degradation of one of said spars.

23. A spar as defined in claim 21 wherein

said airfoil is a fixed wing.

24. A spar as defined in claim 21 wherein

said airfoil is a rotary wing.

25. A spar as defined in claim 22 wherein

said airfoil is a fixed wing.

26. A spar as defined in claim 22 wherein

said airfoil is a rotary wing.

27. A spar as defined in claim 14 wherein

said filament plies include both high modulus filaments and low modulus filaments,

said high modulus filaments being wrapped in one direction and said low modulus filaments being wrapped in the opposite direction, said low modulus filaments being operative to retain the high modulus filaments in their positions without changing the location of said actual bending axis.