Patent Publication Number: US-2023162881-A1

Title: Electrically conductive composite with co-cured region for interface surfaces

Description:
RELATED APPLICATION 
     This patent application claims the benefit of U.S. Provisional Patent Application, Ser. No. 63/283,281 that was filed on Nov. 25, 2021, for an invention titled ELECTRICALLY CONDUCTIVE COMPOSITE WITH CO-CURED REGION FOR INTERFACE SURFACES, which is hereby incorporated herein by this reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to systems and methods for creating electrically conductive surfaces in multi-phase composite systems. More specifically, the present invention relates to systems and methods that provide a highly electrically conductive and corrosion-resistant surface for a multi-component composite. 
     2. The Relevant Technology 
     Current approaches to creating electrically conductive composite systems involve many approaches, primarily encompassing the incorporation of metals, fibers, and resins in various formats and combination methods to achieve desired properties that may include low density, high strength, high stiffness, and high electrical conductivity. 
     For example, current art has been developed to combine metal-coated carbon fiber composite products and metal meshes to construct lightweight composite laminates with good electromagnetic shielding properties. These laminates use very thin and light metallized carbon fiber scrims to impart structural integrity and higher frequency shielding properties in concert with highly open and porous metal meshes (primarily made of copper) which provide very high electrical conductivity and lower frequency shielding protection. These layers can also be jacketed between strong and stiff metal coated carbon fabric layers. This approach yields a lightweight, high strength structural material that provides electromagnetic shielding comparable with solid metal sheeting, at a fraction of the weight and with improved corrosion resistance. 
     To enhance the commercial viability of these lightweight composite laminates formed into component parts of a product having shielding properties, it is important that electrical contact at an interface between components (such as the electrical contact between an enclosure and its lid) have very low resistance. Heretofore, achieving commercial viability while maintaining the requisite electrical contact has proved elusive. Achieving this low resistance requires good physical contact between the most conductive components of the system; namely, the metal-mesh layers and metal-coated composite layers. All components must have good contact with each other because the electrical contact affects shielding performance at both high frequencies and low frequencies. 
     Additionally, the presence of resins in the system complicates the electrical contact issue because the resins do not conduct electricity well, nor do they provide shielding effectiveness. 
     Accordingly, a need exists for new systems and methods for creating electrically conductive surfaces in multi-phase composite systems that provide good physical contact so that the electrical contact at the interface between components has very low resistance. It also would be an advantage if such new systems and methods provided structurally robust components that are non-corrosive and may be streamlined into the normal manufacturing process. Such systems and methods are disclosed herein. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention has been developed in response to the present state of the art. In particular, the problems and needs exhibited in the art have not yet been fully solved by currently available conductive resins or dry gasketing approaches. 
     The invention of the present disclosure is a new approach that addresses previously unmet needs in the industry by co-curing a highly conductive, metal-braided (or metal-knitted) gasket directly into a composite surface. This new approach resolves several issues: gasket tear off or vulnerability issues, non-conductive resin face issues, and the gasket may also be selected such that is provides superior corrosion resistance that will also protect any underlying metal layers. As a result, an electrically conductive surface in a multi-phase composite is created achieving better conductivity as the interface surfaces engage each other between component parts made of multi-phase composites. The issues of gasket tear off and electromagnetic shielding leakage within the interface region are eliminated or drastically reduced. 
     By selecting a highly conductive, metal-braided (or metal-knitted) gasket and infusing it with resin either before or after positioning the gasket to create an interface surface and then co-curing the gasket with the composite layup, the bonding of the gasket to the composite surface secures against tearing forces and metal contact points increase significantly between the gasket and the composite surface, as will be discussed below. The gasket also may be infused with the resin during layup, such as by a wet layup process or a resin infusion process. Further, the gasket may be pressed flat or nearly flat so that the area of contact with the composite surface is also increased significantly so that the co-curing increases the strength of the bond and eliminates the need for an adhesive (whether the adhesive is conductive or non-conductive) between the gasket and the composite surface. 
     These and other features of the present invention will become more fully apparent from the following description or may be learned by the practice of the invention as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS IN THE FIGURES 
       For the above-recited and other features and advantages of the invention to be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are depicted or illustrated in the appended figures. Understanding that these depictions and drawings show only typical embodiments of the invention and should not be considered limiting of its scope, the invention will be described and explained with additional specificity and detail with reference to the accompanying figures in which: 
         FIG.  1    is a photographic depiction of a plan view of exemplary metal-mesh gaskets, showing both a dry gasket and gaskets infused with resin. 
         FIG.  2    is another photographic depiction of a vertical section of a multi-component composite structure having a substantially vertical wall and a substantially horizontal flange formed therein to define a flange face and comprising an infused metal gasket co-cured onto the flange face. 
         FIG.  3    is a perspective view of a vertical section of yet another multi-component composite structure and with a finished interface surface comprising a stepped flange with an infused metal gasket co-cured on the stepped flange. 
         FIG.  4    is a photographic depiction of a top plan view of a transverse edge of an exemplary conductive multi-component composite structure showing an exemplary combination of laminate layers, including a co-cured, compressed conductive gasket layer overlayed along the transverse edge. 
         FIG.  5    is a vertical section of an upper portion of an exemplary conductive multi-component composite structure showing an exemplary combination of laminate layers and a co-cured, compressed conductive gasket layer overlayed along the upper transverse edge of the structure to form a conductive interface surface. 
         FIG.  6    is a side view of an upper portion of another exemplary conductive multi-component composite structure disposed vertically with the portion to the left of Arrow A cutaway on a diagonal section taper to reveal the layers of the multi-component composite, including a co-cured, compressed conductive gasket and an additional metal-mesh gasket attached to the co-cured, compressed conductive gasket by a suitable attachment. 
         FIG.  7    is a side, exploded view of a portion of an exemplary interface region between an upper component and a lower component (such as a lid and an enclosure) showing an infused metal-mesh gasket co-cured on transverse faces of the upper and lower components of representative composite structures. 
         FIG.  8    is a sectional, exploded view of a portion of another exemplary interface region between an upper component and a lower component showing an ablated or roughed, infused metal-mesh gasket co-cured on each transverse face of the upper and lower components of representative composite structures disposed prior to or after the upper and lower components are brought into or out of abutting engagement. 
         FIG.  9    is a sectional end view of an alternative exemplary conductive composite structure showing an exemplary combination of laminate layers disposed vertically, including a co-cured, conductive gasket layer where the co-cured, metal-mesh gasket is less than fully compressed, and a resilient resin is used in curing to give the interface surface a somewhat compressible, resilient surface. 
     
    
    
     REFERENCE NUMBERS 
       
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 metal-mesh gaskets 10 
                 dry metal-mesh gasket 12 
               
               
                 resin 14 
                 infused metal-mesh gaskets 16 
               
               
                 composite structure 18 
                 wall 20 
               
               
                 flange 22 
                 flange face 24 
               
               
                 (co-cured) infused 
                 interface surface 28 
               
               
                 metal gasket 26 
               
               
                 co-cured region 30 
                 copper wire mesh layer 32 
               
               
                 other layer(s) 34 
                 metal-coated carbon fiber 
               
               
                   
                 composite layer 36 
               
               
                 lightweight conductive layer 37 
                 structural layer 38 
               
               
                 wall surface layer 40 
                 metal-wire mesh layer 42 
               
               
                 interface region 44 
                 stepped flange 46 
               
               
                 transverse edge 48 
                 light-weight structural layer 50 
               
               
                 additional metal-mesh gasket 52 
                 upper component 54 
               
               
                 lower component 56 
                 combination composite structure 58 
               
               
                 non-planar roughed surface 60 
                 (exposed) metal threads 62 
               
               
                 resilient resin 64 
                 internal void 66 
               
               
                   
               
            
           
         
       
     
     DETAILED DESCRIPTION OF THE INVENTION 
     The presently preferred embodiments of the invention will be best understood by reference to the figures (photographic depictions and drawings), wherein like parts are designated by like numerals throughout. It will be readily understood that the aspects of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the present invention, as represented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of presently preferred embodiments of the invention. 
     The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated. 
       FIG.  1    is a photographic depiction of exemplary metal-mesh gaskets  10 . Depicted is an exemplary dry metal-mesh gasket  12  on the left side of the photograph. The remaining metal-mesh gaskets  10  shown are infused with a resin  14  to form exemplary infused metal-mesh gaskets  16 . The term “metal-mesh gasket” is meant to include any type of metal-mesh gasket  10 , including highly conductive, metal-braided (or metal-knitted) gaskets, as mentioned above. The type of metal used may be any metal that exhibits suitable conductivity for the gasket&#39;s intended purpose. Additionally, the metal used in the metal-mesh gaskets  10  may be selected from those metals that exhibit better corrosion resistance than, for example, copper or any other metal that is more susceptible to corrosion that may be included as a highly conductive, metal wire mesh layer in a composite structure. Resilient resin  64  is shown representatively in  FIG.  1    but is discussed below in the discussion regarding  FIG.  9   . 
       FIG.  2    is another photographic depiction. It is a vertical section of an exemplary, multi-component composite structure  18  having a substantially vertical wall  20  and a substantially horizontal flange  22  formed therein to define a flange face  24  and comprising an infused metal gasket  26  co-cured onto the flange face  24 . Infused metal gasket  26  co-cured onto the flange face  24  has a conductive interface surface  28 . The representative composite structure  18  depicted comprises a co-cured region  30 , a copper wire mesh layer  32 , and other layer(s)  34  such as a metal-coated carbon fiber composite layer  36 , and a representative structural layer  38  that may or may not be a wall surface layer  40 . Of course, the number of layers, the types of layers, the conductivity of the layers, the juxtaposition of various layers, and the various other composite variables and considerations may be altered and adjusted to create a composite structure  18  with various desired attributes to meet the desired needs for the composite structure  18 . For example, the composite structure  18  depicted has a copper wire mesh layer  32 , but other contemplated composite structures  18  may use a wire mesh comprising a metal other than copper, forming a metal-wire mesh layer  42  or may not have any metal-wire mesh layer  42 . 
     Many types of composite structures are known, and desired composite attributes may be achieved by combining various layers with various characteristics. Heretofore the challenge of creating a robust, highly conductive interface region  44  with enhanced interface surface(s)  28  that protect(s) metal wire mesh layer(s)  32 ,  42  from corrosion has not been accomplished. However, by co-curing an infused metal-mesh gasket  16  with a composite layup, not only is the highly conductive interface surface  28  achieved, but manufacturing is streamlined by combining otherwise multiple steps into a single, simple co-curing manufacturing step that eliminates gasket tear off or vulnerability issues, non-conductive resin face issues, and electromagnetic shielding leakage from the interface region  44 . Exposed metal threads  62  are depicted in  FIG.  2    but are discussed below in reference to  FIG.  8   . 
       FIG.  3    is a perspective view of a vertical section of yet another exemplary multi-component composite structure  18  having a finished interface surface  28  on a stepped flange  46  with an infused metal gasket  26  co-cured on the stepped flange  46 . The composite structure  18  of  FIG.  3    differs from the composite structure  18  of  FIG.  2    in that it is trimmed and finished so that it depicts an interface surface  28  ready for abutting engagement with a complementary trimmed and finished interface surface  28 . 
       FIG.  4    is yet another photographic depiction. It is a top plan view of a transverse edge  48  of an exemplary conductive multi-component composite structure  18  showing an exemplary combination of laminate layers, including a co-cured, compressed infused metal gasket  26  overlayed along the transverse edge  48  forming an interface surface  28 . 
     The representative composite structure  18  depicted comprises a transversely disposed co-cured metal-mesh gasket  26  overlayed upon the transverse edge  48  of the vertically disposed composite layers comprising inside and outside wall surface layers  40 , a copper wire mesh layer  32 , and other layers  34  (the other layers  34 , shown having a phantom lead line to indicate being beneath a visually obscuring structure, and a portion of the copper wire mesh layer  32  are not visible because they are obscured by the overlaying co-cured metal-mesh gasket  26 ). Again, of course, the number of layers, the types of layers, the conductivity of the layers, the juxtaposition of various layers, and the various other composite variables and considerations may be altered and adjusted to create a composite structure  18  with various desired attributes to meet the desired needs for the composite structure  18 . 
     A representative exemplary composite structure  18  having a co-cured conductive metal-mesh gasket  26  overlayed upon and co-cured upon the transverse edge  48  of the vertically disposed composite layers of the composite structure  18  is shown in  FIG.  5   . With this composite structure  18 , a co-cured region  30  comprising a portion of the conductive metal-mesh gasket  26  and a top portion of each of the conductive composite layers define and create at least a portion of a robust, highly conductive interface region  44  having a highly conductive interface surface  28  that is corrosion resistant and corrosion protective to any metal wire mesh layer  42 , particularly the copper wire mesh layer  32 . This is a principal aspect that has not heretofore been known or achieved. 
     The other or additional layers  34  that may be used in the laminate composite structure  18  may be a light-weight conductive layer  37  such as a metal-coated carbon fiber composite layer  36  and/or may be a light-weight structural layer  50  that may be conductive or not conductive and/or any other layer or layers  34 . Those skilled in the art of composite laminates know of many potential combinations of other or additional layers  34  that may be used to achieve other attributes in the composite structure  18 . 
       FIG.  6    is an alternative exemplary conductive composite structure  18  showing an exemplary combination of laminate layers (the portion to the left of Arrow A-A is a cutaway on a diagonal section taper to reveal the layers of the multi-component composite) and includes a co-cured, compressed conductive infused metal gasket  26  and an additional metal-mesh gasket  52  connected to the interface surface  28  of the co-cured, compressed conductive infused metal gasket  26  by a suitable connection. Such connection may be accomplished by adhesive bonding, tacking, spot adhesive bonding, co-curing with the other laminate layers, or any other suitable connection. 
     With the laminate construction shown in  FIG.  6   , the additional metal-mesh gasket  52  (such as a strip gasket) may be dry (as shown in  FIG.  1   , a dry metal-mesh gasket  12 ) and extend along an edge of an interface surface  28  and attached by adhesive or other suitable bonding, or the additional metal-mesh gasket  52  also may be co-cured with the laminate. This type of construction may be used where the interface surface  28  along the edge may be adequate to accomplish the desired conductivity within the interface region  44 . 
     The diagonal section taper portion of the multi-component composite to the left of Arrow A-A reveals an exemplary composite structure  18  comprising a transversely disposed co-cured metal-mesh gasket  26  overlayed upon the transverse edge  48  of the vertically disposed composite layers comprising inside and outside wall surface layers  40 , a copper wire mesh layer  32 , and other layers  34  (the other layers  34 , for example, may comprise a metal-coated carbon fiber composite layer or lightweight conductive layer  36  and a structural layer  38 , as shown). Again, of course, the number of layers, the types of layers, the conductivity of the layers, the juxtaposition of various layers, and the various other composite variables and considerations may be altered and adjusted to create a composite structure  18  with various desired attributes to meet the desired needs for the composite structure  18 . 
     The representative exemplary composite structure  18  having a co-cured conductive metal-mesh gasket  26  overlayed upon and co-cured upon the transverse edge  48  of the vertically disposed composite layers of the composite structure  18  as shown in  FIG.  6   , has a co-cured region  30  comprising a portion of the conductive metal-mesh gasket  26  and a top portion of each of the conductive composite layers define and create at least a portion of a robust, highly conductive interface region  44  having a highly conductive interface surface  28  that is corrosion resistant and corrosion protective to any metal wire mesh layer  42 , particularly the copper wire mesh layer  32 . This is a principal aspect that has not heretofore been known or achieved. 
       FIG.  7    is a side, exploded view of a portion of an exemplary interface region  44  between an upper component  54  and a lower component  56  (such as a lid and an enclosure) showing an infused metal-mesh gasket  16  co-cured on transverse edges (faces)  48  of the upper and lower components  54 ,  56  of representative composite structures  18 . The positions of the upper and lower components  54 ,  56  are shown prior to or after the upper and lower components  54 ,  56  are brought into or out of abutting engagement with each other. The respective interface surfaces  28  are non-planar having complementary mating contours. Complementary mating contours, when in abutting mated engagement, create a contact interface and provide enhanced conductivity to eliminate or drastically reduce electromagnetic shielding leakage within the interface region  44 . 
       FIG.  8    is a sectional, exploded view of a portion of another exemplary interface region  44  between an upper component  54  and a lower component  56  showing an ablated, infused metal gasket  26  co-cured on each transverse edge  48  of the upper and lower components  54 ,  56  of another representative combination composite structure  58 . Again, the positions of the upper and lower components  54 ,  56  are shown prior to or after the upper and lower components  54 ,  56  are brought into or out of abutting engagement. The interface surface  28  of each of the upper and lower components  54 ,  56  within this alternative interface region  44  is a non-planar roughed surface  60 . It should be understood, the non-planar roughed surface  60  shown is exaggerated for illustration purposes. Actual roughing will likely be considerably less pronounced. 
     The roughing of interface surfaces  28  may be achieved by scuffing off some or all excess resin  14  along the interface surface  28  after curing the resin  14 . This also may be done using any of several known ablation processes or techniques such as light sanding, scraping, sand blasting, chemical etching, laser ablation or any other technique that removes excess resin  14  at the interface surface  28 . By roughing the interface surfaces  28 , many metal threads  62  (best seen in  FIG.  2   ) of the metal mesh (best seen in the dry metal-mesh gasket  12  of  FIG.  1   ) of the conductive, infused metal gasket  26  may be exposed. When each of the opposing interface surfaces  28  are brought together, many metal thread-to-metal thread contact points (not shown) will be created, thereby enhancing conductivity between the upper and lower components  54 ,  56 . 
       FIG.  9    is a sectional end view of yet another alternative exemplary conductive composite structure  18  showing an exemplary combination of laminate layers disposed vertically, including an overlayed and co-cured, conductive, infused metal-mesh gasket  26  where the co-cured, infused metal-mesh gasket  26  is less than fully compressed, and a resilient resin  64  is used in curing to give the interface surface  28  a somewhat compressible, resilient interface surface  28 . The exemplary conductive composite structure  18  comprises an exemplary combination of laminate layers, including wall surface layers  40 , a metal wire mesh layer  42  (such as a copper wire mesh layer  32 ), three additional layers  34  that each may be any type of layer that conveys a desired physical attribute (such as, for example as shown, metal-coated carbon fiber composite layer  36 , a light-weight conductive layer  37  and a light-weight structural layer  38 ). These additional layers  34 , if any, may be selected by number of layers, juxtaposition of layers, and type of layers to provide specific attributes to the overall conductive composite structure  18 , and as discussed above, those skilled in the art of composite laminates know of many combinations of other layers  34  that may be used to achieve other desired attributes. One or more of these other layers  34  may be conductive or not conductive. This alternative embodiment depicts a conductive composite structure  18  where the conductive infused metal gasket  26 , the metal wire mesh layer  32 , and any additional layers  34  are combined into a composite layup that is co-cured. 
     The co-cured, conductive, infused metal-mesh gasket  26  shown in  FIG.  9    is attached to the transverse edge  48  of the combination of vertically disposed laminate layers. As depicted, the infused metal-mesh gasket  26  is less than fully compressed, thereby leaving an interior void  66  that facilitates a degree of resiliency in the infused metal-mesh gasket  26 . To introduce a resilient interface surface  28  on the conductive composite structure  18 , a resilient resin  64  may be infused into the metal mesh of the metal-mesh gasket  26  and the internal void  66 , thereby filling the interstices of the metal mesh and the internal void  66 . Then, by co-curing the resilient resin  64 , the interface surface  28  may be somewhat compressible, creating resilient interface surface(s)  28  while maintaining conductivity. 
     Manufacturing expediency is achieved by the present invention. By co-curing an infused metal-mesh gasket  16  together with a composite layup, not only is the highly conductive interface surface  28  achieved but it combines the securement of the infused metal-mesh gasket  16  with a simple manufacturing step that is already being performed in creating the laminate. The only real difference is that the step is altered by adding the compressed infused metal-mesh gasket  16  to the transverse edge  48  of the combination of vertically disposed laminate layup prior to curing so that the compressed infused metal-mesh gasket  16  is co-cured with the other laminate layers  34 . Significantly, this unique method creates a co-cured region  30  that eliminates gasket tear off or vulnerability issues, non-conductive resin face issues, and electromagnetic shielding leakage within the interface region  44 . Additionally, the co-curing increases the strength of the bond and eliminates the need for an adhesive (whether the adhesive that would have been used otherwise is conductive or non-conductive) between the gasket and the transverse edge  48  or the flange face  24 . 
     Those skilled in the art will appreciate that the present embodiments are exemplary and should not be limited to the embodiments shown and described. 
     The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention will, therefore, be indicated by the ultimate claims, rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.