The present disclosure generally relates to metal-plated polymer components having improved physical and mechanical properties. More specifically, this disclosure relates to metal-plated polymer components having improved interfacial bond strengths.
Metal-plated polymer components consist of a polymer substrate coated with a metal plating. These components are lightweight and, by virtue of the metal plating, exhibit markedly enhanced structural strength and capability over the structural strength and capability of the polymer substrate alone. These properties have made them attractive for component fabrication in many industries such as aerospace, automotive, and military equipment industries, where high-strength and lightweight materials are desired. For example, metal-plated polymer components continue to be explored for use in gas turbine engine applications to reduce the overall weight of the engine and improve engine efficiency and provide fuel savings. However, the strength and performance characteristics of metal-plated polymer materials may be dependent upon the integrity of the interfacial bond between the metal plating and the underlying polymer substrate. Even though the surface of the polymer substrate may be etched or abraded to promote the adhesion of metals to the polymer surface and to increase the surface area of contact between the metal plating layer and the polymer substrate, the interfacial bond strength between the metal plating and the polymer substrate may be the structurally weak point of metal-plated polymer structures. As such, the metal plating layers may become disengaged from polymer substrate surfaces which could lead to part failure in some circumstances.
The interfacial bond strength between the metal plating and the underlying polymer substrate may be compromised upon exposure to high temperatures, such as those experienced during some high-temperature engine operations. If metal-plated polymers are exposed to temperatures over a critical temperature or a sufficient amount of thermal fatigue (thermal cycling or applied loads at elevated temperatures) during operation, the interfacial bond between the metal plating and the polymer substrate may be at least partially degraded, which may lead to structural break-down of the component and possible in-service failure. Unfortunately, brief or minor exposures of metal-plated polymer components to structurally-compromising temperatures may go largely undetected in many circumstances, as the weakening of the bond between the metal-plating and the underlying polymer substrate may be difficult to detect. To provide performance characteristics necessary for the safe use of metal-plated polymer components in gas turbine engines and other applications, enhancements are needed to improve the interfacial bond strengths of metal-plated polymer components.
Clearly, a system is needed to improve the mechanical strength of the interfacial bond between metal platings and polymer surfaces in plated polymer components.
In accordance with one aspect of the present disclosure, a plated polymer component is disclosed. The plated polymer component may comprise a polymer substrate having an outer surface and a metal plating attached to the outer surface of the polymer substrate. The plated polymer component may further comprise at least one interlocking feature connecting the polymer substrate and the metal plating.
In another refinement, the at least one interlocking feature may comprise and interlocking aperture formed on the outer surface of the polymer substrate that is filled with a material of the metal plating.
In another refinement, the plated polymer component may comprise a plurality of the at least one interlocking features.
In another refinement, the interlocking aperture may be formed on the outer surface of the polymer substrate by a method selected from the group consisting of additive manufacturing, injection molding, and machining.
In another refinement, the at least one interlocking aperture may comprise a crevice formed on the outer surface of the polymer substrate that is filled with a material of the metal plating.
In another refinement, the crevice may be formed on the outer surface of the polymer substrate by micro-knurling.
In another refinement, the at least one interlocking feature may comprise at least one interlocking hole extending through a body of the polymer substrate, and the at least one interlocking hole may include a hole extending through the body of the polymer substrate that is plated along a wall of the hole with the metal plating.
In another refinement, the hole may be formed through the body of the polymer substrate by a method selected from the group consisting of injection molding, additive manufacturing, machining, drilling, and etching.
In another refinement, the at least one interlocking hole may be filled with a filling agent.
In accordance with another aspect of the present disclosure, a plated polymer component is disclosed. The plated polymer component may comprise a polymer substrate having at least one exposed surface, and a metal plating deposited on the at least one exposed surface of the polymer substrate. The plated polymer component may further comprise at least one interlocking hole extending through a body of the polymer substrate, and the at least one interlocking hole may include a hole extending through the body of the polymer substrate that is plated along a wall of the hole with the metal plating.
In another refinement, the metal plating may be plated on the wall of the hole by electrolytic deposition.
In another refinement, the hole may have a diameter of at least about 1.6 mm.
In another refinement, the metal plating may be plated on the wall of the hole by electroless deposition.
In another refinement, the hole may have a diameter of at least about 0.8 mm.
In another refinement, the at least one interlocking hole may be filled with a filling agent.
In another refinement, the filling agent may be selected from a group consisting of an epoxy material, an epoxy material containing a filler metal, a low-melting alloy, and one or more wires.
In accordance with another aspect of the present disclosure, a plated polymer component is disclosed. The plated polymer component may comprise a polymer substrate having an outer surface, and a metal plating attached to the outer surface of the polymer substrate. The plated polymer component may further comprise a plurality of interlocking features at an interface between the metal plating and the polymer substrate. Each of the plurality of interlocking features may consist of an interlocking aperture formed on the outer surface of the polymer substrate that is filled with a material of the metal plating.
In another refinement, the interlocking aperture may be formed on the outer surface of the polymer substrate by a method selected from the group consisting of additive manufacturing, injection molding, and machining.
In another refinement, the interlocking aperture may have a depth of at least about 0.005 mm.
In another refinement, at least one of the plurality of interlocking apertures may comprise a crevice formed on the outer surface of the substrate that is filled with a material of the metal plating.
These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the accompanying drawings.
It should be understood that the drawings are not necessarily drawn to scale and that the disclosed embodiments are sometimes illustrated schematically and in partial views. It is to be further appreciated that the following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses thereof. In this regard, it is to be additionally appreciated that the described embodiment is not limited to use with specific applications. Hence, although the present disclosure is, for convenience of explanation, depicted and described as certain illustrative embodiments, it will be appreciated that it can be implemented in various other types of embodiments and in various other systems and environments.
Referring now to
The polymer substrate 52 may be formed from a thermoplastic or thermoset material. Suitable thermoplastic materials may include, but are not limited to, polyetherimide (PEI), thermoplastic polyimide, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polysulfone, polyamide, polyphenylene sulfide, polyester, polyimide, and combinations thereof. Suitable thermoset materials may include, but are not limited to, condensation polyimides, addition polyimides, epoxy cured with aliphatic and/or aromatic amines and/or anhydrides, cyanate esters, phenolics, polyesters, polybenzoxazine, polyurethanes, polyacrylates, polymethacrylates, silicones (thermoset), and combinations thereof. Optionally, the polymeric material of the polymer substrate 52 may be structurally reinforced with materials that may include carbon, metal, or glass.
At or near the interface of the metal plating 54 and the polymer substrate 52 may be one or more interlocking features 57 which may behave as mechanical fasters between the metal plating 54 and the polymer substrate 52, as shown in
The interlocking apertures 59 may have one or more various shapes including, but not limited to, upside-down âTâ shapes, arrow shapes, double âTâ shapes, tri-pod shapes, and/or upside-down street-sign shapes, as shown, and may be introduced into the outer surface by additive manufacturing, injection molding, or machining (see further details below). Depending on the performance requirements of the plated polymer component 50 as well as other considerations, the interlocking apertures 59 may be evenly distributed across the outer surface 55 or may be localized to specific areas of the outer surface 55 requiring a stronger attachment of the metal plating 54. In addition, they may be present on the outer surface 55 in a pre-determined pattern or in a random pattern. The minimum depth of the interlocking apertures 59 may be about 0.0002 inches (about 0.005 mm) and the minimum spacing between the interlocking apertures 59 may be about 0.0002 inches (about 0.005 mm) according to the reproducibility of current polymer fabrication processes, but other aperture depths and spacings may also suffice depending on the manufacturing method used. The diameter (or width) of the interlocking apertures 59 may be at least wide enough to allow the deposition of the metal plating 54 within the interlocking apertures 59. More specifically, the diameters of the interlocking apertures 59 may be at least wide enough to permit the deposition of the catalyst used in the metal plating process on the surfaces of the interlocking apertures 59 (see further details below).
As an alternative arrangement, the outer surface 55 of the polymer substrate 52 may have one or more crevices 60 which may lack a mechanical interlocking ability but may increase the surface area of contact between the metal plating 54 and the polymer substrate 52 (see
A series of steps which may be involved in the fabrication of the plated polymer component 50 is illustrated in
Following the block 66, several steps may be performed (blocks 67, 68, 70, 72, and 74) to deposit the metal plating 54 on selected outer surfaces 55 of the polymer substrate. According to a block 67, one or more outer surfaces 55 of the polymer substrate 52 selected for plating may be prepared to receive a catalyst by mechanical abrasion or chemical etching. According to a next block 68, a catalyst layer may be deposited on the prepared outer surface(s) 55 of the polymer substrate and the exposed surfaces of the interlocking apertures 59 and/or the crevices 60 according to a next block 68, as shown. The catalyst layer may have a thickness on the atomic scale and may consist of palladium or another suitable catalyst material. It is noted that, if desired, masking may be used during the metal deposition steps (blocks 68, 70, 72, and 74) to prevent attachment of the metal plating 54 to certain outer surfaces of the polymer substrate.
According to a next block 70, electroless (or current-free) deposition of a first layer, which may be nickel, on the catalyst layer may be performed as will be understood by those having ordinary skill in the art. Following the block 70, electrolytic deposition of a second layer on the first layer may then be performed according to a block 72, as shown. The second layer may be a copper layer or another conductive material, such as silver or conductive graphite. Following the electrolytic deposition of the second layer, the outer surface(s) 55 of the polymer substrate 52 (including the coated surfaces of the interlocking apertures 59 and/or the crevices 60) may exhibit surface characteristics similar to a metal (i.e., conductivity), thereby allowing the deposition of additional metal platings thereon. Accordingly, the metal plating 54 may be then be deposited on the second layer (including the coated surfaces of the interlocking apertures 59 and/or the crevices 60) according to the block 74, as shown. The metal plating layer 54 may be deposited by a metal deposition technique apparent to those having ordinary skill in the art including, but not limited to, electroplating, electroless plating, and electroforming. During the block 74, the interlocking apertures 59 and/or the crevices 60 may be filled with the metal plating 54. Optionally, additional metal plating layers having the same or different compositions may be deposited by repeating the block 74 as desired. Following the block 74, the plated polymer component 50 having interlocking features 57 which may markedly enhance the interfacial strength between the metal plating 54 and the polymer substrate 52 is provided.
Turning now to
The component 80 may exhibit high interfacial bond strength between the metal plating 84 and the polymer substrate 82 by virtue of one or more interlocking holes 85 which may extend through the entire body of the polymer substrate 82, as best shown in
The metal plating 84 may consist of any platable material such as, but not limited to, nickel, cobalt, copper, iron, gold, silver, palladium, rhodium, chromium, zinc, tin, cadmium, and alloys with any of the foregoing elements comprising at least 50 wt. % of the alloy, and combinations thereof. The thickness of the metal plating 84 may be in the range of about 0.001 inches (0.0254 mm) to about 0.050 inches (1.27 mm), but other metal plating thicknesses may also apply. The polymer substrate 82 may be formed from a thermoplastic or thermoset material. Suitable thermoplastic materials may include, but are not limited to, polyetherimide (PEI), thermoplastic polyimide, polyether ether ketone (PEEK), polyether ketone ketone (PEKK), polysulfone, polyamide, polyphenylene sulfide, polyester, polyimide, and combinations thereof. Suitable thermoset materials may include, but are not limited to, condensation polyimides, addition polyimides, epoxy cured with aliphatic and/or aromatic amines and/or anhydrides, cyanate esters, phenolics, polyesters, polybenzoxazine, polyurethanes, polyacrylates, polymethacrylates, silicones (thermoset), and combinations thereof. Optionally, the polymeric material of the polymer substrate 82 may be structurally reinforced with one or more materials that may include carbon, metal, or glass.
As an optional arrangement, one or more of the interlocking holes 85 may be filled with a filling agent 87, as shown in
The fabrication of the component 80 is schematically depicted in
Depending on the method used for depositing the metal plating 84 (electroless plating, electroplating, electroforming, etc.), the holes 89 may have a minimum diameter of about 0.063 inches (about 1.6 mm) for electroplating or a minimum diameter of about 0.031 inches (about 0.8 mm) for electroless plating, but other hole diameters may also suffice. Electroplating may require larger hole diameters as it may be difficult to pass sufficient current density through smaller holes during the electrolytic process and provide uniform metal deposition. The holes 89 of the polymer substrate 82 may have different diameters and may or may not be oriented perpendicular to the outer surfaces of the polymer substrate 82 (i.e., they may be oriented at oblique angles with respect to the outer surfaces of the polymer substrate 82).
After the polymer substrate 82 is formed, the metal plating 84 may be introduced onto selected exposed surfaces of the polymer substrate 82 as well as the walls of the holes 89. In this regard, masking of selected surfaces of the polymer substrate 82 may be used to block certain exposed surfaces from being plated, if desired. Plating of the metal on the exposed surfaces of the polymer substrate 82 may be achieved following suitable polymer surface activation and metallization (see
For electroplating in holes 89 that have an aspect ratio (hole depth/diameter) greater than three (3), one or more supplemental anodes may be employed to assist uniform plating along the walls of the holes 89. The supplemental anodes may insert into the holes 89 during the electrolytic process to help provide uniform plating coverage. The supplemental anodes may be formed from the metal of the desired plating and may be conformal anodes having a shape that mirrors the shape of the holes 89. Depending on the number of holes in the polymer substrate 82, the supplemental anodes may be connected to each other to form a single comb-like structure having supplemental anodes as prongs which insert into each of the holes 89 during electrolytic deposition. However, those of ordinary skill in the art will understand that depending on the number, size, and arrangement of the holes 89, various other supplemental anode arrangements may be employed for electrolytic metal plating. Following the plating process 90, the component 80 having interlocking holes 85 may be provided, as shown.
A method for forming the interlocked plated polymer component 80 is illustrated further detail in
The selected exposed surfaces (including the walls of the holes 89) of the polymer substrate 82 may first be prepared to receive a catalyst according to a block 96, as shown. Preparation of the selected exposed surfaces may involve surface etching, surface abrasion, ionic activation, or another suitable method selected by a skilled artisan. According to a next block 98, the exposed surfaces of the polymer substrate 82 (including the walls of the holes 89) may be activated with a catalyst layer, which may be a palladium catalyst layer having a thickness on the atomic scale. As other non-limiting possibilities, the catalyst may be platinum or gold. Electroless deposition of a first layer on the catalyst layer followed by electrolytic deposition of a second layer on the first layer may be performed by the blocks 100 and 102, respectively. The first layer may be formed from nickel. The second layer may be copper or another suitable conductive material, such as silver or conductive graphite. Following the deposition of the second layer, the surfaces of the polymer substrate 82 may exhibit surface properties similar to a metal (e.g., conductivity), thereby allowing the subsequent deposition of one or more metal plating layers thereon. According to a next block 104, deposition of the metal plating 84 on the second layer may be performed by a metal deposition method apparent to those skilled in the art including, but not limited to, electrolytic deposition (electroplating), electroless deposition, or electroforming. It is noted that the electrolytic deposition of the second layer and the metal plating 84 in the holes 89 may be achieved with the use of supplemental anodes, particularly for holes having an aspect ratio greater than three, as described above. Following the block 104, additional plating layers having the same or different compositions may be deposited by electroplating or by another plating technique apparent to those of ordinary skill in the art.
From the foregoing, it can therefore be seen that introduction of mechanical interlocking features at the interface of metal platings and polymer substrates in plated polymer structures may advantageously enhance the interfacial bond strength between the metal plating and the polymer substrate. The technology as disclosed herein may be particularly applicable in industries requiring high-strength and lightweight materials, such as, but not limited to, automotive, aerospace, and sporting industries.
This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/844,108 filed on Jul. 9, 2013.
Filing Document | Filing Date | Country | Kind |
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PCT/US2014/045921 | 7/9/2014 | WO | 00 |
Number | Date | Country | |
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61844108 | Jul 2013 | US |