Multi-layer coating for a flow surface of an aircraft component

A component is provided for an aircraft. This aircraft component includes an object and a multi-layer coating. The object includes an object surface. The multi-layer coating includes a barrier layer and a laminar flow layer. The covers at least a portion of the object surface. The barrier layer a fluoropolyether, a silicon rubber and/or a polyurethane. The laminar flow layer covers the barrier layer and forms an exterior surface of the component. The laminar flow layer includes a sol-gel siloxane, a rare-earth oxide and/or a phosphate.

BACKGROUND

1. Technical Field

This disclosure relates generally to coatings and, more particularly, to a multi-layer coating for an aircraft component.

2. Background Information

Various coatings are known in the art for use with aircraft components. While these known coatings have various advantages, there is still room in the art for improvement.

SUMMARY OF THE DISCLOSURE

According to an aspect of the present disclosure, a component for an aircraft is provided. This aircraft component includes an object and a multi-layer coating. The object includes an object surface. The multi-layer coating includes a barrier layer and a laminar flow layer. The barrier layer covers at least a portion of the object surface. The barrier layer includes a fluoropolyether, a silicon rubber and/or a polyurethane. The laminar flow layer covers the barrier layer and forms an exterior surface of the component. The laminar flow layer includes a sol-gel siloxane, a rare-earth oxide and/or a phosphate.

According to another aspect of the present disclosure, an apparatus is provided that includes a metal object and a multi-layer coating that consists of (only includes) a barrier layer and a flow layer. The metal object includes an object surface. The barrier layer covers at least a portion of the object surface. The barrier layer includes a fluoropolyether, a silicon rubber and/or a polyurethane. The flow layer covers the barrier layer and forms an exterior surface of the component. The laminar flow layer includes a sol-gel siloxane, a rare-earth oxide and/or a phosphate. The apparatus is configured as a component of an aircraft.

According to still another aspect of the present disclosure, another apparatus is provided that includes a metal object and a multi-layer coating that consists of (only includes) a barrier layer, a flow layer and a primer between the barrier layer and the flow layer. The barrier layer covers at least a portion of the object surface. The barrier layer includes a fluoropolyether, a silicon rubber and/or a polyurethane. The flow layer covers the barrier layer and forms an exterior surface of the component. The flow layer includes a sol-gel siloxane, a rare-earth oxide and/or a phosphate. The apparatus is configured as a component of an aircraft.

The object may be a metal object.

The object surface of the metal object may be anodized and/or sealed.

The object may be configured as a nacelle noselip skin.

The object may be configured as a flight control skin.

The barrier layer may be configured from or otherwise include the fluoropolyether.

The barrier layer may be configured from or otherwise include the silicon rubber.

The barrier layer may be configured from or otherwise include the polyurethane.

The barrier layer may be doped with at least one inhibitor.

The inhibitor may include (a) barium sulfate or calcium sulfate and (b) Pr(OH)3.

The laminar flow layer may be configured from or otherwise include the sol-gel siloxane.

The laminar flow layer may be configured from or otherwise include the rare-earth oxide.

The rare-earth oxide may be configured from or otherwise include CeO2 and/or LaPO4.

The laminar flow layer may be configured from or otherwise include phosphate.

The barrier layer may be applied directly onto the object surface.

The laminar flow layer may be applied directly onto the barrier layer.

The multi-layer coating may also include a primer between the barrier layer and the laminar flow layer.

The primer may be configured from or otherwise include a functionalized alkoxysilane including a hydrolysable unit, (3-glycidoxypropy)trimethoxysilane and/or an aminoethylaminopropytrimethoxysilane.

DETAILED DESCRIPTION

FIG. 1is a perspective illustration of an aircraft10such as a passenger airliner. This aircraft10includes various exterior components with aerodynamic exterior flow surfaces. Examples of such exterior components include, but are not limited to, a noselip12of a nacelle14for a propulsion system, an aircraft flight control component as well as other aircraft components with leading edges. Examples of a flight control component include, but are not limited to, a wing leading edge flap16and a wing leading edge slat18. Examples of other aircraft components with leading edges include, but are not limited to, a stabilizer wing20, a tail wing22and an engine pylon24. The present disclosure, of course, is not limited to the foregoing exemplary aircraft components. The present disclosure is also not limited to the foregoing exemplary aircraft configuration. For example, in other embodiments, the aircraft10may alternatively be configured as a business-type jet, a cargo plane, a propeller plane, a helicopter or any other type of aircraft.

An aircraft component with an aerodynamic exterior flow surface, such as the components described above, may be contaminated and/or damaged during aircraft operation with/by debris. Examples of debris include, but are not limited to, insects, dirt and ice. Accumulation of debris on the flow surface and/or damage (e.g., pitting, wear, etc.) to the flow surface caused by debris may negatively affect natural laminar flow over the flow surface of the component. A reduction in laminar flow may in turn reduce aircraft efficiency; e.g., reduce propulsion system fuel efficiency. Therefore, to prevent or reduce likelihood of debris related contamination and/or damage to the flow surface of the aircraft component, the aircraft component may include a multi-layer coating as described herein.

FIG. 2is a sectional illustration of a portion of an exterior component26with an aerodynamic exterior flow surface28for an aircraft such as the aircraft10. This component26may be configured as one of the exemplary exterior components described above, or any other component of an aircraft which forms an aerodynamic exterior flow surface of the aircraft. The component26ofFIG. 2includes an object30(e.g., a substrate) and a multi-layer coating32.

The object30may be configured as a support and/or base structure of the component26. More particularly, the object30may be configured to provide the component26with its structural integrity and characteristics (e.g., stiffness, etc.). The object30is also configured to provide the component26with its geometry and general size. For example, where the multi-layer coating32is applied substantially evenly over a surface34of the object30(object surface), the multi-layer coating32may not substantially (or at all) alter the underlying geometry of the object30. Rather, the multi-layer coating32may merely add to the size of the object30.

In some embodiments, the object30may be configured as or otherwise include an aerodynamic exterior flow skin. The object30, for example, may be configured as or otherwise include a nacelle noselip skin (e.g., a skin of noselip12ofFIG. 1) or a flight control skin (e.g., a skin of component16,18,20,22or24ofFIG. 1). The present disclosure, of course, is not limited to the foregoing exemplary embodiments.

The object30may be formed from or otherwise include metal such as, but not limited to, aluminum (Al), titanium (Ti) or an alloy thereof. However, in other embodiments, the object30may alternatively be formed from or otherwise include non-metal such as, but not limited to, fiber-reinforced composite material. The present disclosure, of course, is not limited to the foregoing exemplary object materials.

The multi-layer coating32is applied (directly or indirectly) to and covers at least a portion (e.g., an entirety or a leading edge portion) of the object surface34. The coating32may have a thickness36that is less than a thickness38of the object30. For example, the object thickness38may be between about (e.g., +/−2%) 13,000 to 250 times (e.g., between 500 and 800 times) greater than the coating thickness36. However, in other embodiments, the object thickness38may be less than 250 times greater than the coating thickness36, or greater than 13,000 times greater than the coating thickness36. For example, the object thickness may be as small as about 0.020 inches and the thickness36may be as large as about 0.005 inches such that the object thickness38is about four times (4×) greater than the coating thickness36. The present disclosure, of course, is not limited to the foregoing exemplary dimensions or dimensional relationships.

The multi-layer coating32ofFIG. 2at least includes (or may only include) a barrier layer40and a laminar flow layer42. Each of these layers40,42may provide and/or promote various characteristics such as, but not limited to, decreased insect adhesion, increased durability and corrosion protection as discussed below in further detail. In combination, the layers40and42may provide and/or promote various additional characteristics such as, but not limited to, transparency, relatively high temperature resistance and relatively high solvent resistance.

The barrier layer40is applied (directly or indirectly) to and covers at least a portion (e.g., an entirety or a leading edge portion) of the object surface34. This barrier layer40may account for about (e.g., +/−2%) 93 to 98 percent of the coating thickness36. The present disclosure, of course, is not limited to the foregoing exemplary dimensions. For example, in other embodiments, the barrier layer40may account for less than 97 percent of the coating thickness36, or more than 95 percent of the coating thickness36.

The barrier layer40may be configured to provide passive and/or active corrosion protection for the underlying object material. For example, for passive corrosion protection, the barrier layer40may at least include (or may only include) a fluoropolymer, a silicon rubber and/or a polyurethane. An example of a fluoropolymer containing material is, but is not limited to, the fluoropolymer containing material disclosed in U.S. Pat. No. 9,567,468, which is hereby incorporated herein by reference in its entirety.

For active corrosion protection, the barrier layer40may at least include (or may only include) at least one of the above-described barrier layer materials in combination with one or more inhibitors. More particularly, the barrier layer material may be doped with the one or more inhibitors. Examples of an inhibitor include, but are not limited to, ZnMoO4, Pr2O3, Ce-citrate, magnesium silicate, graphene nanoplatelets, alkali earth sulfate, zinc oxide and/or yttrium oxide. Where the inhibitor is an alkali earth sulfate such as, but not limited to, barium/calcium sulfate, an additive such as Pr(OH)3 may also be included in the barrier layer material. Examples of other inhibitors which may also or alternatively be included in the barrier layer material include those inhibitors disclosed in U.S. Publication No. 2017/0350020, which is hereby incorporated herein by reference in its entirety. The present disclosure, of course, is not limited to the exemplary fluoropolymer, silicon rubber, polyurethane or inhibitor materials described above. Furthermore, in some embodiments, the barrier layer material may also include one or more additives not described above.

The laminar flow layer42ofFIG. 2is applied directly to and covers at least a portion (e.g., an entirety or a leading edge portion) of the underlying barrier layer40. This laminar flow layer42may account for about (e.g., +/−2%) 7 to 2 percent of the coating thickness36. The present disclosure, of course, is not limited to the foregoing exemplary dimensions. For example, in other embodiments, the laminar flow layer42may account for less than 5 percent of the coating thickness36, or more than 3 percent of the coating thickness36.

The laminar flow layer42may form at least a portion (e.g., an entirety or a leading edge portion) of the flow surface28of the component26. Thus, the laminar flow layer42may be directly exposed to air flowing along the component26during aircraft operation. As a result, the laminar flow layer42may also be directly exposed to debris carried by the air. Therefore, the laminar flow layer42is configured to promote laminar flow of the air over the component26. More particularly, the laminar flow layer42is configured to increase durability of the component26as well as reduce debris (e.g., insect, direct and/or ice) adhesion to the flow surface28. For example, the laminar flow layer42may at least include (or may only include) a sol-gel siloxane, a rare-earth oxide and a phosphate. The sol-gel siloxane containing material may also include a chlorosilane and/or a cross-linker. Such sol-gel siloxane containing material can provide nanostructuring, which can help to decrease surface energy; e.g., has relatively high hydrophobicity. Another example of a sol-gel siloxane containing material is disclosed in U.S. Publication No. 2005/0282953, which is hereby incorporated herein by reference in its entirety. Examples of a rare-earth oxide include, but are not limited to, CeO2 and LaPO4, where the Ce and La may be replaced with any other rare-earth element such as, but not limited to, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb. Such rare earth oxides are durable, high temperature resistant ceramics. The present disclosure, of course, is not limited to the exemplary sol-gel siloxane, rare-earth oxide or phosphate materials described above. Furthermore, in some embodiments, the laminar flow layer material may also include one or more additives not described above.

FIG. 3is a sectional illustration of a portion of another exterior component26′ with an aerodynamic exterior flow surface28′ for an aircraft such as the aircraft10. Similar to the component26ofFIG. 2, the component26′ ofFIG. 3may be configured as one of the exemplary exterior components described above, or any other component of an aircraft which forms an aerodynamic exterior flow surface of the aircraft. The component ofFIG. 3includes the object30and the layers40and42of the multi-layer coating32described above with reference toFIG. 2. However, in contrast to the component26ofFIG. 2, a multi-layer coating32′ ofFIG. 3also includes a primer44disposed between the barrier layer40and the laminar flow layer42. Thus, the laminar flow layer42is applied indirectly to the barrier layer40through the primer44.

The primer44is applied (directly or indirectly) to and covers at least a portion (e.g., an entirety or a leading edge portion) of the underlying barrier layer40. The primer44is configured to promote adhesion between the barrier layer40and the laminar flow layer42, which layer42is applied (directly or indirectly) to and covers at least a portion (e.g., an entirety or a leading edge portion) of the underlying laminar flow layer42.

The primer44may at least include (or may only include) a functionalized alkoxysilane that includes a hydrolysable ligand such as, but not limited to, a halide, an alkoxide, or an amine. The primer44may at least include (or may only include) (3-glycidoxypropy)trimethoxysilane and/or an aminoethylaminopropytrimethoxysilane (diaminofunctional silane). An example of a functionalized alkoxysilane is (3-aminopropyl)triethoxysilane. The silane may include 1 to 3 hydrolyzable units (alkoxy (e.g., ethoxy, methoxy, etc.) for bonding to a surface of the barrier layer40following hydrolysis and subsequent condensation. The terminal functional group may include amino, amide, carboxy, epoxide, etc. for bonding to the laminar flow layer42. The halide may include Cl, Br or I for bonding to a surface of the barrier layer40. In some embodiments, a mixture of hydrolysable units (e.g., mixture of alkoxy and halide) may also be considered. The present disclosure, of course, is not limited to the exemplary primer materials described above.

In some embodiments, the object30and its surface34may be conditioned prior to application of the multi-layer coating32,32′. This conditioning may promote enhanced adhesion between the object30and the barrier layer40. The conditioning may also or alternatively provide enhanced corrosion protection of the object material. For example, where the object30is formed from metal (e.g., aluminum and aluminum alloy), the object surface34may be anodized and/or sealed.