Method and coating for protecting and repairing an airfoil surface

• US 20070231156A1
• Filed: 12/14/2006
• Published: 10/04/2007
• Est. Priority Date: 12/14/2005
• Status: Active Grant

• Current Assignee: Hontek Corporation
• Original Assignee: Hontek Corporation
• Inventors: Hong, Shek
• Granted Patent: US 8,091,227 B2
• Time in Patent Office: Days
• US Class Current: 416/241.R
• CPC Class Codes: B05D 1/42 by non-rotary members
• CPC Class Codes: B05D 5/005 Repairing damaged coatings
• CPC Class Codes: B05D 5/06 to obtain multicolour or other optical effects B05D5/02 takes precedence
• CPC Class Codes: B05D 7/56 Three layers or more
• CPC Class Codes: B05D 7/58 No clear coat specified
• CPC Class Codes: B23P 6/007 using only additive methods, e.g. build-up welding
• CPC Class Codes: B64F 5/40 Maintaining or repairing aircraft
• CPC Class Codes: F01D 5/005 Repairing methods or devices
• CPC Class Codes: F05D 2230/10 by removing material
• CPC Class Codes: F05D 2230/30 with deposition of material
• CPC Class Codes: F05D 2230/90 Coating; Surface treatment manufacture with deposition of material F05D2230/30
• CPC Class Codes: F05D 2300/43 Synthetic polymers, e.g. plastics; Rubber
• CPC Class Codes: F05D 2300/611 Coating
• CPC Class Codes: Y02T 50/60 Efficient propulsion technologies, e.g. for aircraft
• CPC Class Codes: Y10T 29/49318 Repairing or disassembling
• CPC Class Codes: Y10T 29/49746 by applying fluent material, e.g., coating, casting
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree
• CPC Class Codes: Y10T 428/2495 Thickness [relative or absolute]

Abstract

This invention relates to the repair and removal of erosion or impact damage using hand sandable elastomeric coatings on a curved substrate, particularly such surfaces as the leading edge of the airfoil. Specialized applicators and methods of use are also disclosed.

Claims

1. A method of repairing an airfoil surface having a plurality of damage cavities caused by erosion or impact damage comprising:

filling said plurality of damage cavities in said surface with a liquid repair material using a flexible applicator capable of conforming to the surface of said airfoil surface while being drawn lengthwise along the airfoil surface.

2. The method of claim 1 wherein the contact between the airfoil surface and said flexible applicator is a curvilinear line of contact which changes as the flexible applicator is drawn lengthwise along the airfoil surface.

3. The method of claim 1 wherein the portion of the airfoil surface containing the plurality of cavities is a surface surrounding the leading edge of said airfoil.

4. The method of claim 1 wherein said airfoil surface has an elastomeric protective coating adhered to a portion of said airfoil surface and said elastomeric protective coating contains said plurality of damage cavities caused by erosion or impact damage.

5. The method of claim 1 further comprising the preliminary step of:

sanding the portion of said airfoil surface containing said plurality of damage cavities with abrasive material.

6. The method of claim 5 further comprising applying a primer coat over the portion of said airfoil surface containing said plurality of damage cavities after said sanding step.

7. The method of claim 6 further comprising after applying said primer coat of then filling the cavities with said liquid repair material formulated as an elastomeric basecoat over the portion of said airfoil surface containing said plurality of damage cavities.

8. The method of claim 1 further comprising after said step of filling said plurality of cavities the further step of subsequently applying an erosion resistant topcoat over the portion of said airfoil surface containing said plurality of damage cavities.

9. The method according to claim 8 wherein said erosion resistant topcoat is more sand erosion resistant than the underlying elastomeric basecoat.

10. The method of claim 1 wherein said flexible applicator has stiffness sufficient to spread a semi-solid material.

11. The method of claim 1 wherein said flexible applicator is a flat sheet of elastomeric material of selected thickness to allow it to be deformable around an arcuate surface and stiff enough to spread viscous material smoothly ahead of it when drawn through the viscous material.

12. The method of claim 1 wherein said flexible applicator is a planar flexible thermoplastic sheet selected such that it does not fold or wrinkle at a curvilinear surface contact line on the contour of said airfoil surface and maintains contact with the surface to be repaired and does not allow fluid to pass between the sheet surface contact line and the surface over which it is being drawn.

13. An elastomeric airfoil erosion protection coating for visual detection of water and sand erosion damage comprising:

(a) a primer of a first color applied directly on a structural substrate of said airfoil surrounding a leading edge of said airfoil;

(b) a basecoat of a second color applied over said primer; and

(c) a topcoat of a third color on top of said basecoat, wherein said first color, second color and third color are contrasting colors allowing visual detection of damage to said protection coating by visual inspection to detect the appearance of the second color of said basecoat or first color of said primer indicating damage in the area.

14. A method of detecting damage to an airfoil erosion protection coating having a primer layer of a first color, a basecoat of a second color and a top coat of a third color comprising:

detecting erosion damage by visually inspecting the erosion protection coating to detect the appearance of the second color of the basecoat or the first color of the primer which indicates that there is erosion damage in the area of the airfoil protection coating where the first color or second color appear.

15. A method of detecting and repairing damage to an airfoil erosion protection coating having a primer layer of a first color, a basecoat of a second color and a top coat of a third color comprising:

(a) detecting erosion damage by visually inspecting the erosion protection coating to detect the appearance of the second color of the basecoat or the first color of the primer which indicates that there is erosion damage in the area of the airfoil protection coating where the first color or second color appear; and

(b) reapplying a plurality of layers of said topcoat to the areas showing said first color or said second color.

16. A method of making an airfoil leading edge erosion protection coating capable of being field repairable by hand sanding, comprising:

(a) applying to an airfoil substrate a coating system comprising a hand sandable basecoat and a topcoat, said basecoat being of lower sand erosion resistance than the topcoat and said basecoat constituting at least 50% of the total coating thickness;

(b) subjecting said erosion protection coating to service which erodes portions of the topcoat away leaving a plurality of cavities in said basecoat having irregular edges;

(c) repairing said erosion protection coating by sanding said plurality of cavities until all irregular edges extending above the surface of said coating have been sanded until said edges are flush with the surface;

(d) applying a repair basecoat to fill said plurality of cavities to form filled cavities; and

(e) applying a repair topcoat layer over the filled cavities.

17. A method of detecting damage to a composite protective layer adhered to a leading edge surface of an airfoil structure comprising:

(a) applying a primer of a first color to the surface surrounding the leading edge of an airfoil structure;

(b) overlaying a basecoat of a second color different from the first color on top of said primer;

(c) applying over said basecoat a topcoat of a third color different from the first color and the second color; and

(d) detecting damage to said airfoil structure from water and sand erosion by visually inspecting the leading edge of the airfoil to detect the appearance of the second color of the basecoat or the first color of the primer in areas where erosion damage has occurred.

18. An erosion protection coating for substrates adapted to be repairable by hand sanding comprising a topcoat and a sandable basecoat, wherein the basecoat has lower sand erosion resistance than the topcoat and said basecoat constitutes at least 50% of the total coating thickness.

19. A field repairable polymeric erosion protection composition positioned on and adhered to a leading edge surface of an airfoil comprising an elastomeric base composition loaded with fillers sufficient to render the polymeric erosion protection composition hand sandable, said base elastomeric base composition tested in accordance with ASTM D412-92 prior to incorporation of said fillers having a minimum tensile strength of 1000 psi, an elongation at break of at least 200%, and a Shore A hardness of less than 95 A.

20. A repairable elastomeric coating for a leading edge surface of an airfoil comprising:

(a) an elastomeric, hand sandable basecoat disposed surrounding said leading edge surface having a sand erosion rate above 0.020 grams/cm²; and

(b) an elastomeric topcoat disposed on top of said elastomeric basecoat having a sand erosion rate below 0.020 grams/cm².

21. The repairable elastomeric coating according to claim 20 wherein said elastomeric topcoat has a sand erosion rate below 0.010 grams/cm².

22. The repairable elastomeric coating according to claim 20 wherein the basecoat has lower sand erosion resistance than the topcoat and said basecoat constitutes at least 50% of the total coating thickness.

23. A repairable elastomeric coating for a leading edge surface of an airfoil comprising:

(a) an elastomeric, hand sandable basecoat disposed surrounding said leading edge surface having an elastomeric base material having a minimum tensile strength of 1000 psi, an elongation at break of at least 200%, and a Shore A hardness of less than 95 A with additional fillers added in sufficient amount to render the elastomeric base material sandable.

24. An applicator comprising:

a body having an open interior area defined by at least one interior wall, said wall having a wiping edge at a distal end thereof and a front edge generally opposite said wiping edge;

said wiping edge defining a contour complimentary to a leading edge surface of an airfoil;

said front edge defining a contour shaped to form a pocket between said leading edge surface of said airfoil and said interior wall; and

wherein

during operation an elastomeric material is resident within said pocket so that as said applicator is drawn along said leading edge surface of said airfoil said elastomeric material is deposited on said leading edge surface of said airfoil and follows the shape defined thereby.

25. The applicator according to claim 24 further comprising an outer surface of said one interior wall having a griping means incorporated therein adapted to allow the applicator to be drawn manually along said leading edge.

26. The applicator according to claim 24 further comprising means for providing access to said pocket from said outer surface of said one interior wall.

27. The applicator according to claim 24 further comprising a handle means affixed to an outer surface of said one interior wall.

28. The applicator according to claim 24 further comprising a means for conveying said elastomeric material through said one interior wall into said pocket.

29. The applicator according to claim 24 wherein said one interior wall is a plastic member capable of maintaining the shape of said wiping edge defining a contour complimentary to a leading edge surface while said applicator is being drawn along said leading edge surface of said airfoil.

30. The applicator according to claim 24 wherein said one interior wall is a plastic member having elastic memory capable of maintaining the shape of said wiping edge defining a contour complimentary to a leading edge surface while said applicator is being drawn along said leading edge surface of said airfoil and capable of deforming slightly to pass over a slightly raised portion of said leading edge surface while returning to said shape after passing over said slightly raised portion.

31. An airfoil repair kit comprising:

a) a flexible applicator capable of conforming to a leading edge surface of an airfoil; and

b) an elastomeric, hand sandable repair material.

32. The airfoil repair kit according to claim 31 further comprising one or more components selected from the group consisting of a sanding disc, a primer, an elastomeric basecoat, an elastomeric topcoat, a brush, and a disposable sprayer.