Abstract:
An encapsulated polymeric article is disclosed. The encapsulated polymeric article may include a polymer substrate and a metallic outer shell at least partially encapsulating the polymer substrate. The encapsulated polymeric article may be fabricated by a method comprising: 1) providing a mandrel in a shape of the encapsulated polymeric article, 2) shaping the metallic outer shell on the mandrel, 3) removing the mandrel from the metallic outer shell, and 4) molding the polymeric substrate into the metallic outer shell through a port formed in the metallic outer shell to provide the encapsulated polymeric article.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/844,161 filed on Jul. 9, 2013. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure generally relates to polymeric components. More specifically, this disclosure relates polymeric components at least partially encapsulated in a metallic outer shell. 
       BACKGROUND 
       [0003]    Many engineers continue to seek strategies to fabricate high-strength and lightweight components in complex geometries for various industrial applications. Lightweight components may be desirable, for example, in some applications (e.g., automotive and aerospace applications) to provide increases in fuel efficiency. In addition, higher-strength components may exhibit enhanced performance characteristics such as improved environmental durability, erosion resistance, and impact resistance. Polymeric materials may be attractive materials for forming components with complex geometrical features, as they are lightweight and may be molded into a range of complex shapes. However, many polymeric materials may be limited to relatively few structurally loaded applications due to their low strengths relative to metallic materials. In addition, certain complex geometries may be costly to access by conventional polymer molding techniques such as injection molding. 
         [0004]    Clearly, there is a need for enhancements to provide high-strength and lightweight parts in a range of complex geometries. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    In accordance with one aspect of the present disclosure, an encapsulated polymeric article is disclosed. The encapsulated polymeric article may comprise a polymer substrate, and an outer shell at least partially encapsulating the polymer substrate. The polymer substrate and the outer shell may be in mechanical contact without being bonded to each other. 
         [0006]    In another refinement, the outer shell may be formed from a metallic material. 
         [0007]    In another refinement, the outer shell may fully encapsulate the polymer substrate. 
         [0008]    In another refinement, the metallic material may be selected from the group consisting of nickel, cobalt, copper, iron, gold, silver, palladium, rhodium, chromium, zinc, tin, cadmium, and an alloy of any of the foregoing elements comprising at least 50 wt. % of the alloy, and combinations thereof. 
         [0009]    In another refinement, the polymer substrate may be formed from a thermoplastic material. 
         [0010]    In another refinement, the thermoplastic material may be selected from the group consisting of polyetherimide, thermoplastic polyimide, polyether ether ketone, polyether ketone ketone, polysulfone, polyamide, polyphenylene sulfide, polyesters, polyimide, and combinations thereof. 
         [0011]    In another refinement, the polymer substrate may be formed from a thermoset material. 
         [0012]    In another refinement, the thermoset material may be selected from the group consisting of a condensation polyimide, an addition polyimide, an epoxy cured with an aliphatic amine, an aromatic amine, and/or an anhydride, a cyanate ester, a phenolic compound, a polyester, polybenzoxazine, a polyurethane, a polyacrylate, a polymethacrylate, a thermoset silicone, and combinations thereof. 
         [0013]    In another refinement, the polymer substrate may be reinforced with a reinforcement material selected from glass and carbon. 
         [0014]    In accordance with another aspect of the present disclosure, an encapsulated polymeric article is disclosed. The encapsulated polymeric article may include a polymer substrate and a metallic outer shell at least partially encapsulating the polymer substrate. The encapsulated polymeric article may be fabricated by a method comprising: 1) providing a mandrel in a shape of the encapsulated polymeric article, 2) shaping the metallic outer shell on the mandrel, 3) removing the mandrel from the metallic outer shell, and 4) molding the polymeric substrate into the metallic outer shell through a port formed in the metallic outer shell to provide the encapsulated polymeric article. 
         [0015]    In another refinement, shaping the metallic outer shell on the mandrel may comprise shaping the metallic outer shell on the mandrel by a method selected from the group consisting of electroforming, cold spraying, and plasma vapor deposition. 
         [0016]    In another refinement, molding the polymeric substrate into the metallic outer shell may comprise injecting a polymeric material into the metallic outer shell. 
         [0017]    In another refinement, molding the polymeric substrate into the metallic outer shell may comprise molding the polymeric substrate by compression molding. 
         [0018]    In another refinement, the method may further comprise introducing the port into the metallic outer shell prior to molding the polymeric substrate into the metallic outer shell. 
         [0019]    In another refinement, the method may further comprise attaching one or more additional features to the encapsulated polymeric article. 
         [0020]    In another refinement, the method may further comprise removing the port from the metallic outer shell after molding the polymeric substrate into the metallic outer shell. 
         [0021]    In accordance with another aspect of the present disclosure, a method for fabricating an encapsulated polymeric article is disclosed. The method may comprise: 1) providing a mandrel in a shape of the encapsulated polymeric article, 2) shaping an outer shell on the mandrel, 3) removing the mandrel from the outer shell, and 4) molding a polymeric substrate into the outer shell through a port formed in the outer shell to provide the encapsulated polymeric article. 
         [0022]    In another refinement, shaping the outer shell on the mandrel may comprise shaping the outer shell on the mandrel by a method selected from the group consisting of electroforming, cold spraying, and plasma vapor deposition. 
         [0023]    In another refinement, molding the polymeric substrate into the outer shell may comprise injecting a polymeric material into the outer shell. 
         [0024]    In another refinement, molding the polymeric substrate into the outer shell may comprise molding the polymeric substrate by compression molding. 
         [0025]    These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is a front view of a metal-encapsulated polymeric article, constructed in accordance with the present disclosure. 
           [0027]      FIG. 2  is a cross-sectional view of the metal-encapsulated polymeric article of  FIG. 1  taken along the line  2 - 2  of  FIG. 1 , constructed in accordance with the present disclosure. 
           [0028]      FIG. 3  is a flowchart illustrating a method for the fabrication of the metal-encapsulated polymeric article, in accordance with a method of the present disclosure. 
       
    
    
       [0029]    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 certain 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. 
       DETAILED DESCRIPTION 
       [0030]    Referring now to  FIGS. 1 and 2 , an encapsulated polymeric article  250  is shown. The encapsulated polymeric article  250  may consist of a polymeric substrate  252  encapsulated in one or more outer shells  254 , as best shown in  FIG. 2 . Depending on the application, the polymeric substrate  252  may be fully encapsulated or it may be partially encapsulated in the outer shell  254 . The outer shell  254  may be formed from a metallic material and may substantially increase the strength of the article  250  over all polymeric materials of similar size and dimensions. Accordingly, the article  250  may exhibit enhanced performance characteristics over similarly-dimensioned completely polymeric parts with respect to properties such as, but not limited to, environmental durability, erosion resistance, impact resistance, and resistance to foreign-objection damage. In addition, the article  250  may exhibit a range of geometries, including complex geometries. More specifically, it may have any shape suitable for its intended use, which may deviate substantially from the exemplary box-like structure shown in  FIGS. 1 and 2 . 
         [0031]    The polymeric substrate  252  may be in intimate contact with the outer shell  254  and there may be a mechanical interaction between the polymeric substrate  252  and the outer shell  254 . However, the polymer substrate  252  may not be directly bonded to the outer shell  254 . If the outer shell  254  is formed from metallic materials, it may be formed from a range of metallic materials, 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 polymeric substrate  252  may be formed from a thermoplastic material or a thermoset material, and it may be optionally structurally reinforced with reinforcement materials, such as, but not limited to, carbon or glass. 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, polyesters, polyimide, combinations thereof, or any of the foregoing with reinforcement (e.g., carbon or glass). 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), combinations thereof, or any of the foregoing with fiber reinforcement. 
         [0032]    A method for fabricating the encapsulated polymeric article  250  is illustrated in  FIG. 3 . Beginning with a first block  256 , a mandrel in the shape of the desired article may be provided. The mandrel may be designed to be removable from the outer shell  254  or it may be a sacrificial mandrel. It may be formed in the desired shape by a conventional forming process (e.g., additive manufacturing, etc.) from a range of materials such as, but not limited to, metallic materials including pure metals and alloys, polymeric materials, glass, or wood. According to a next block  258 , the outer shell  254  may be formed on the mandrel from selected metallic materials. The outer shell  254  may be shaped on the mandrel using a range of processes apparent to those skilled in the art such as, but not limited to, electroforming, cold spraying, plasma vapor deposition, or other spray deposition processes. 
         [0033]    Subsequent to the block  258 , the mandrel may be removed from the outer shell  254  according to a block  260 , leaving the outer shell  254  with one or more open (or hollow) internal cavities for receiving polymeric materials. A port (or opening) for receiving the polymeric materials may be directly formed in the body of the outer shell  254  during its formation (block  258 ), but if not, a port may be later introduced into the body of the outer shell by an optional block  261 , as shown. This port may have features such as a flange or a boss to facilitate attachment of a polymer molding tool in the next step (see below). 
         [0034]    Following the block  260  (or the block  261 ), the polymeric substrate  252  may be molded in the outer shell  254  by injecting selected polymeric materials (selected from the thermoplastic or thermoset materials described above) into the outer shell  254  through the port, according to a block  262 . Alternatively, the polymeric substrate  252  may be molded into the outer shell  254  by compression molding or another suitable process selected by a skilled artisan. 
         [0035]    The block  262  may furnish the desired encapsulated polymeric article  250 , although additional optional processing of the article may also follow. For example, the port on the outer shell  254  may be removed by machining or another process by an optional block  264 , as shown. Alternatively, the port may be designed to be an integral part of the article  250  and may be used, for example, to subsequently attach the article  250  to another component. In addition, additional features (e.g., bosses or inserts) may be attached to the encapsulated polymeric article  250  according to an optional block  266 . Such features may be attached to selected surfaces of the article using a range of methods apparent to those skilled in the art such as, but not limited to, adhesive bonding, riveting, brazing, or transient liquid phase (TLP) bonding. It is noted that the optional block  266  may also be performed prior to the block  262 , if desired. As another optional processing step, a polymer coating may be applied over the surfaces of the article  250  according to an optional block  268 , as shown. The polymer coating may be applied by conventional processes such as, but not limited to, spray coating or dip coating, and it may be applied over all of the outer surfaces of the article or on selected surfaces. The optional polymer coating may produce a lightweight, strong, and polymeric-appearing (non-conductive) article. 
       INDUSTRIAL APPLICABILITY 
       [0036]    From the foregoing, it can therefore be seen that encapsulated polymeric articles as disclosed herein may find industrial applicability in many situations such as, but not limited to, situations requiring lightweight, high-strength parts with complex geometrical features. The metallic outer shell may markedly enhance the structural resilience of the article and lead to advantageous improvements in properties such as, but not limited to, stiffness, environmental durability, erosion resistance, impact resistance, and foreign-object damage resistance. In addition, the outer shell may be formed into a range of complex shapes and serve as a template for molding the polymeric substrate. In some circumstances, this fabrication method may lead to increased ease of fabricating complex part geometries and reductions in manufacturing costs. The technology as disclosed herein may find wide industrial applicability in a wide range of areas such as, but not limited to, automotive and aerospace industries.