Abstract:
A gasket for compressible placement between a first surface and a second surface is disclosed. In one embodiment, the gasket has a cellular metal skeleton embedded in a viscoelastic, pliable, deformable tacky polymer body. The skeleton has multiple strands, which connect to form multiple interconnected cells or pores. The skeleton, prior to being encapsulated in the tacky polymer body, is typically about 75% or more void space. The void space is substantially filled in the manufacture of the gasket, with the tacky uncured polymer. The uncured polymer will set up or cure, and then the gasket may be used.

Description:
[0001]    This application claims priority from U.S. Provisional Patent Application Ser. No. 62/026,352, filed Jul. 18, 2014; and Provisional Application Serial No. 62/078,451, filed Nov. 12, 2014, both applications incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Gaskets, including tacky elastomeric gaskets having a reticulated cellular metallized or foam metal skeletal member. 
       BACKGROUND OF THE INVENTION 
       [0003]    Gaskets are typically provided between mating surfaces for providing, among other things, an effective environmental seal. However, gaskets are typically found in a wide variety of environments and, therefore, often have widely or substantially different properties. Some gaskets may be used in heavily corrosive environments, others in high pressure and high temperature environments, still others in environments that are subject to a variety of different chemicals or electrical properties. Thus, gaskets are typically designed for the specific environments and moreover are often a compromise among several different design objectives. 
         [0004]    In an aircraft environment, gaskets are used to provide good environmental seal between two parts having a mating surfaces for placement of the gasket therebetween. Aircraft gaskets may also be used in an environment, such as an aircraft antenna, where EMI (electromagnetic interference) or RFI (radio frequency interference) may occur due to a gap between the metallic body fuselage of the aircraft and the metal aircraft antenna. This gap may create a potential difference (voltage) and may adversely affect the transmission or receipt of radio frequencies from the antenna. A number of solutions to the EMI problem have been provided, wherein a part of the gasket is highly conductive and the gasket is compressed sufficiently to provide an electrically conductive path across the gap of, for example, of an antenna mounted to the fuselage of an aircraft. 
         [0005]    Some of the solutions to the problems of EMI may be found in U.S. Pat. No. 6,309,742 (Culpepper 2001), the contents of which are incorporated herein by reference. The &#39;742 patent discloses the use of an electrically conductive gasket comprising an open cell foam substrate having a skeletal structure in a range of pore density between about 80 to about 250 pores per inch, the open cell foam structure having a metal coating deposited therein. The metal coating is nickel and the gasket may have a defined range of volume resistivity, deformability, and recoverability. 
         [0006]    In Applicant&#39;s issued U.S. Pat. Nos. 6,530,577; 6,695,320; and 7,229,516 (incorporated herein by reference), gaskets are disclosed that have a skeletal member that may be flexible and open, such as a woven member as a skeletal member impregnated with a polymer gel. The skeletal member provides certain properties to the gasket and the polymer gel body other properties. The polymer body, which may be a viscoelastic cured gel, may provide deformability and surface tack, and the skeletal structure substantially encapsulated by the body may provide shape, especially two dimensional shape, and structure to the gasket and, when metallic, may provide good conductivity between mating surfaces when the gasket is placed between the mating surfaces and compressed. 
       SUMMARY OF THE INVENTION 
       [0007]    A gasket for compressible placement between a first surface and a second surface, the gasket comprising: a viscoelastic, pliable, deformable, tacky polymer body; and a cellular metal skeleton embedded in the body, the skeleton having multiple interconnected strands, some of the strands meeting at nodes, the strands and nodes defining multiple interconnected cells or pores, the skeleton having a pore density which may be measured in an x, y and z dimension, the z axis being the shortest axis and normal to the x and y axis and the first and second aircraft surfaces and defining a skeleton thickness, the skeleton having a relative density of less than about 25%. 
         [0008]    The gasket wherein the skeleton comprises regular-shaped cells. 
         [0009]    The gasket wherein the skeleton comprises irregular-shaped cells. 
         [0010]    The gasket wherein the skeleton has a pore density of between about 17 and 63 ppi. 
         [0011]    The gasket wherein the skeleton has a pore density of between about 50 and 150 ppi. 
         [0012]    The gasket wherein the skeleton has a pore density of between about 15 and 250 ppi. 
         [0013]    The gasket wherein the mass density of the skeleton is between about 0.3 and 0.6 g r/cc. 
         [0014]    The gasket wherein the skeleton has a thickness in the range of about 0.0125″ to about 0.50″. 
         [0015]    The gasket wherein the skeleton has a relative density of less than about 10%. 
         [0016]    The gasket wherein the skeleton requires greater than about 50 psi before there is about 20% or more of reduction to its original thickness. 
         [0017]    The gasket wherein the resistance of the skeleton measured in the z dimension is less than about 2.5 milliohms. 
         [0018]    The gasket wherein the strands and nodes of the skeleton are solid metal. 
         [0019]    The gasket wherein the strands and nodes of the skeleton are metal with a non-metallic core. 
         [0020]    The gasket wherein the body is a cured polyurethane gel. 
         [0021]    The gasket wherein the polyurethane has a cured hardness of between about 40 and 150 (cone penetration). 
         [0022]    The gasket wherein the cured body is tacky. 
         [0023]    The gasket wherein the cellular skeleton is aluminum or aluminum alloy. 
         [0024]    The gasket wherein the body is a cured polyurethane gel. 
         [0025]    The gasket wherein the metal is nickel or nickel alloy. 
         [0026]    The gasket wherein the metal is aluminum or aluminum alloy. 
         [0027]    The gasket wherein cells have an average pore diameter in the range of about 0.01″ to 0.125″. 
         [0028]    A gasket for compressible placement between a first aircraft surface and a second aircraft surface, the gasket comprising: a viscoelastic, pliable, deformable, tacky polymer body; a cellular metal skeleton embedded in the body, the skeleton having multiple interconnected strands, some of the strands meeting at nodes, the strands and nodes defining multiple interconnected cells or pores, the skeleton having a pore density which may be measured in an x, y and z dimension, the z axis being the shortest and being normal to the x and y axis and the first and second aircraft surfaces and defining a skeleton thickness, the skeleton having a cell volume of greater than 75%; wherein the skeleton comprises irregular-shaped cells; wherein the skeleton has a pore density of between about 17 and 63 ppi, wherein the pore density is substantially the same in the x, y and z dimensions; wherein the skeleton has a relative density of less than 30%; and wherein the strand and nodes of the skeleton are solid metal. 
         [0029]    The gasket wherein the metal is nickel or nickel alloy. 
         [0030]    The gasket wherein the metal is aluminum or aluminum alloy. 
         [0031]    A method of making a gasket for compressible placement between a first surface and a second surface, the method comprising the steps of: providing an uncured polymer mix that will cure to a tacky, pliable gel; providing a cellular metal skeleton, the skeleton having multiple interconnected strands, some of the strands meeting at nodes, the strands and nodes defining multiple interconnected cells or pores, the skeleton having a pore density which may be measured in an x, y and z dimension, the z axis being the shortest axis and normal to the x and y axis and the first and second surfaces and defining a skeleton thickness; encapsulating the skeleton in the uncured polymer mix; and allowing the polymer to cure. 
         [0032]    The method wherein the encapsulating step includes placing the skeleton and polymer mix in a mold until the gel cures, then removing it from the mold. 
         [0033]    The method wherein the encapsulating step is achieved by combining the mix with the skeleton without a mold. 
         [0034]    The method wherein the encapsulating step includes placing the skeleton and polymer mix in a mold and drawing a vacuum on the mold. 
         [0035]    The method wherein the encapsulating step includes allowing gravity to urge the mix into the skeleton. 
         [0036]    The method wherein the encapsulating step includes pressing the polymer mix into the skeleton. 
         [0037]    A metal foam is a cellular structure the metal of which may be a solid metal, such as aluminum, as well as a large volume of open pores. The pores can be sealed (closed cell) or they can form an interconnected network (open cell), typically about 70 to 95% void space. 
         [0038]    In one embodiment of Applicant&#39;s gasket, an open cell substrate is provided having a metal coating, substantially encapsulated with a viscoelastic or elastomeric body that provides a good environmental seal, and removes the voids in the foam skeleton such that there are substantially no pockets of air or gas. 
         [0039]    In another preferred embodiment of Applicant&#39;s gasket, an open cell skeleton is provided with substantially solid metal struts and nodes defining the cells. 
         [0040]    In another embodiment, a metal open cell foam, such as Duocel® available from Energy Research and Generation, Oakland, Calif., or NiFoam from Recemat BV, The Netherlands, is substantially saturated, encapsulated and covered by a sticky, pliable body that will provide a good environmental seal when under compression between mating surfaces, including, in one embodiment, an aircraft antenna and an aircraft fuselage. 
         [0041]    The elastomeric gel body provided to the various metal cellular skeletal structures set forth herein will provide a good environmental seal against gas or fluid leaks, as well as resistance to potentially corrosive hydrocarbons, such as jet fuel. Applicant&#39;s gel body will assist in vibration dampening and may be flexible and deformable under compression so as to conform to the workpiece and be substantially inert to the environment (air, moisture, hydraulics or other hydrocarbons) and inert (non-corrosive) to the material comprising the workpiece and base. 
         [0042]    In one embodiment, the body encapsulating the foam metal is a cured, viscoelastic or elastomeric gel, which may be polyurethane, polyurea or other suitable material, poured and cured about the metal foam skeletal structure. One method of manufacturing the gasket disclosed herein is similar to that which may be found in U.S. Pat. Nos. 6,530,577; 6,695,320; and 7,229,516, but modified as set forth herein. The foregoing patents are incorporated by reference. 
         [0043]    In one embodiment, the body encapsulating or enclosing the skeleton has a cured peel strength between about 0.1 and 2.0 pounds per inch width has a hardness of between about 40 and 150 (measured with a 37.5 g half cone penetrometer), a tackiness as set forth in the patents incorporated by reference, and a viscosity that allows it to deform and flow under compression in the range of about 10 to 500 psi. In a preferred embodiment, the chemical composition of the body may be a two-part self curable polymer mix: polyurethane, polyurea, fluorosilicone rubber or any other suitable composition. In another embodiment, the gel body comprises a two-phased colloidal system typically a dispersed phase and a continuous phase providing a viscous, jelly-like or gel product for the body to create an effective environmental seal. 
         [0044]    In a preferred embodiment of the gasket, there may be a unitary integral, solid gasket (substantially no air or gas pockets) comprised of a celular metal skeleton and a sticky, polymeric, viscoelastic elastomer body, which gasket in cross-section is substantially free of any air containing voids and provides a body thickness (pre-compression) that typically exceeds foam metal skeletal thickness by at least a 2.5 mil. In a preferred embodiment, the foam metal skeleton is sheet-like and the body enclosing or encapsulating the sheet-like metal skeleton is sheet-like also with the same perimeter or exterior shape. 
         [0045]    In a preferred embodiment, the cellular metal skeleton is a conductive metal with sufficient conductivity to overcome EMI when placed under compression between spaced apart metallic bodies. The metal of the skeleton may include the following metals: aluminum, copper, silver, carbon, silicon carbide, and nickel (including alloys of these metals). The metals comprising the skeleton of the gasket may be coated or uncoated and, if coated, may be coated with another metal, such as silver, nickel or other suitable material. 
         [0046]    In a preferred embodiment, the skeleton is cut to size and is placed in a mold and a two-part polymer is applied with an applicator in a thick, syrupy uncured mix that will cover and surround and work its way through (or is forced through) the voids of the metal, and cure to form an elastomeric tacky body, which substantially encloses or encapsulates the skeleton. 
         [0047]    The skeletal structure typically has free and complete communication between all of the voids (is open), such that it is a continuous integral structure with a plurality of voids or openings, such that there is complete communication between all the voids. Such a structure may be found in U.S. Pat. No. 3,616,841, incorporated herein by reference, and is available from Energy Research &amp; Generation, Oakland, Calif., under the mark Duocel®. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0048]      FIG. 1  is an illustration of a skeleton with irregular-shaped pores. 
           [0049]      FIG. 1A  is an illustration of a skeleton with a regular structure. 
           [0050]      FIGS. 1B and 1C  are photographs of the skeleton of  FIGS. 1 and 1A , respectively. 
           [0051]      FIG. 2  is a detail perspective view of the cell structure of the skeleton. 
           [0052]      FIG. 2A and 2B  are cross-sectional views of a small portion of the gasket,  FIG. 2A  showing the manner in which a gasket body may extend beyond the skeletal structure and  FIG. 2B  a close up of a cell of the skeleton and the manner in which it may be saturated with the body material. 
           [0053]      FIGS. 2C and 2D  illustrate cross sections thru the strands. 
           [0054]      FIG. 3  is a perspective exploded view of an assembly that may use applicant&#39;s gasket used with an aircraft antenna.  FIG. 3A  is a close up cross-sectional view illustrating Applicant&#39;s gasket under compression. 
           [0055]      FIGS. 4 and 4A  are cross-sectional views showing the relationship between the skeletal member and the gasket body and some dimensions of the gasket body and skeletal member. 
           [0056]      FIGS. 5A and 5B  are cross-sectional views of two methods of manufacturing Applicant&#39;s gasket. 
           [0057]      FIG. 5C  is a perspective view of a portion of the gasket in an embodiment that includes conductive or non-conductive particulate filler. 
           [0058]      FIGS. 5D ,  5 E and  5 F illustrate perspective views of methods to manufacture the applicant&#39;s gasket. 
           [0059]      FIGS. 6 ,  7  and  8  are top views of three different shaped gaskets made by the methods and having the structure and function disclosed herein. 
           [0060]      FIGS. 9 ,  10 , and  11  illustrate the use of Applicant&#39;s novel elastomeric foam metal gasket for use on an aircraft with sealing an aircraft fuel access door to the surface of an aircraft fuselage or skin. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0061]      FIG. 1  illustrates a perspective illustration of a cellular metal skeleton  12  of the type which may be used in gasket  10  (see  FIG. 2A ).  FIGS. 2 ,  2 A,  2 B,  2 C,  2 D,  3 A,  4  and  4 A illustrate Applicant&#39;s gasket  10  comprising a metal skeleton  12  substantially saturated with a gasket body  14 . Skeleton  12  may be a foam metal skeleton, in one embodiment; a reticulated open cell foam, in one embodiment, Duocel® foam. The term foam metal or cellular metal skeleton may refer to an all metal skeleton or a skeleton with strands having a non-metallic core. Gasket body  14  may be a cured polyurethane, polyurea or other suitable polymer gel two component mix  11  (see  FIG. 5B ) that is applied with an applicator  18  and allowed to cure after saturating skeleton  12 . 
         [0062]    In  FIGS. 1 ,  1 A, B, C,  2 ,  2 A, and  2 B, skeleton  12  is seen to have a skeleton perimeter  12   a , multiple open cells  12   b  each one that may comprise multiple struts or strands  12   d  that are joined at nodes  12   c . Each cell (for example, see  FIG. 2B ) is joined to multiple other cells and they are intertwined as seen in a cross-section view,  FIG. 2A . In one configuration, each cell  12   b  is configured generally like a “bucky ball” and as substantially set forth in the &#39;841 patent incorporated herein by reference (see also  FIGS. 1A and 1C ). The skeletons may be as substantially set forth and may be made by the methods set forth in U.S. Pat. Nos. 6,309,742 and 3,616,841. Briefly, the foam metal body of the &#39;841 patent may be “all metal” (see  FIG. 2C , cross-section of a strand), whereas the foam metal body of the &#39;742 patent may include metal deposited on a non-metallic foam substrate (see  FIG. 2D ). Either foam metal skeleton or any other cellular metal skeleton may be used with the pliable gasket body  14  to provide the suitable gasket  10  for use in a number of environments.  FIG. 2C  illustrates that the strands may be solid metal (or metal with an open core), while  FIG. 2D  illustrates that in cross-section, strands  12   d  may be a metal coated  13   a , deposited on a core  13   b , which may be non-metal such as a polyurethane reticulated foam core. This skeleton may sometimes be termed a metalized foam. The strands of  FIG. 2D  sometimes provide more “give” (less stiff) and resiliency than skeletons made from the solid metal strands of  FIG. 2C . 
         [0063]      FIG. 1A  illustrates an embodiment of a skeletal structure  12 , in which the pores are regular shaped, that is, generally defined by regularly orderly shaped cells, at least in three dimensions (see  FIG. 1A ), in one view being honeycomb and, in one embodiment, honeycomb shaped. In the embodiment of the skeleton set forth in  FIG. 1 , the pores are somewhat random in size, shape, and spacing (three dimensioned), thus deemed “non-regular.” Both skeletons may have the same pore density and void space. 
         [0064]    Gasket body  14  may have a perimeter  14   a  as seen in  FIGS. 2 ,  4 , and  4 A, which perimeter  14   a  may, in one embodiment, extend pass all of the outer surfaces of the metal skeleton  12  a distance of about 1 mil up to about 20 mil. In another embodiment, the perimeter  14   a  make extend past one, two or more faces or surfaces of the skeleton  12 , depending upon the use. This is illustrated with the “gap” in  FIGS. 4 and 4A  (no gap on the lower surface in  FIG. 4A ). 
         [0065]    A range of thicknesses Ts for the skeleton  12 , which in one preferred embodiment may be tabular (and may contain holes for fasteners or other items), is in the range of about 20 to 150 mil. A preferred thickness (shortest dimension) of body Tb in a preferred embodiment is tabular, essentially the same shape as the metal skeleton  12 , and substantially saturating the cells thereof, Tb in one embodiment, in the range of about 30 to 200 mil. 
         [0066]      FIG. 3  illustrates one environment or assembly in which gasket  10  may be used, that is, between two parts, here, aluminum antenna A a  and aluminum outer surface A s  of an aircraft. These parts A s  and A a  represent the skin of an aircraft A s  and an aircraft antenna (A a ) with an embodiment of Applicant&#39;s gasket  10  therebetween. Fasteners (not shown) are entrained in the holes illustrated and the gasket is typically compressed between the moveable workpiece (antenna) and static base (aircraft outer surface). Compression will tend to squeeze out the pliable sticky, soft body material, which may extend (uncompressed) above or below the surface of the skeleton, which squeeze out may be seen in  FIG. 3A . Typically, the gasket  10  may be die cut as set forth below, such that the perimeter of the gasket conforms to the perimeter of the workpiece, here, in one embodiment, an aircraft antenna. 
         [0067]    In  FIG. 3A , squeeze out is seen extending past the edges of As and Ab, as well as past the edge of the skeletal member. This occurs under compression and may be wiped clean with an alcohol soaked cloth, if desired. The greater the compression, the greater the squeeze out. In  FIGS. 4 and 4A , it is seen that there may be a perimeter  14   a  of gel body extending above or below one or both of the upper or lower surface of the skeleton creating a gap. Additionally, there may or may not be a gap along the perimeter. For example,  FIG. 4  illustrates that prior to compression the body extends beyond the perimeter, sidewalls and the top of the skeleton, leaving a gap, but there being no gap on the bottom surface. In  FIG. 4A , there is a gap that is a difference between TS, referring to skeletal thickness and TB referring to body thickness, the gap defining a perimeter  14   a  typically comprised of gel. 
         [0068]    The gel or body material that is on the gasket surfaces facing the faying structures is used to create a good environmental seal between the two pieces that generate the compression on the gasket. In one embodiment, the skeleton is substantially soaked with the gel such as polyurethane gel and there is only a very thin veneer on the top surface and the bottom surface of the gasket, prior to compression, amounting to only about 1 or 2 two mil. In this embodiment there may be substantially no perimeter gap, could just a thin veneer of gel along the perimeter of the skeleton. When a very thin layer or veneer of gel is provided, there will be, when under compression, less or limited squeeze out. In one embodiment, the skeleton may be undercut; that is, cut back a few millimeters from the edge of the workpiece. In this embodiment, when compression occurs between the movable workpiece and the base, the squeeze will tend to fill the undercut. 
         [0069]      FIGS. 5A and 5B  illustrate two ways to make the gasket illustrated herein. An important objective in making the gasket is soaking the skeleton so that substantially all of the voids contain the body material. These two methods illustrated combine the uncured fluid, viscous or semi-solid mix  11  (typically in the viscosity range of 18,000 to 42,000 cps at about 24-26° C.) that will form gasket body  14  with the metal skeleton, such that there is soaking or encapsulation of the skeleton. The first illustrated cross-sectional view of  FIG. 5A  uses a substantially closed mold M in which is placed in (vacuum assisted) close proximity to the walls thereof, metal skeleton  12 . A liquid or semi-solid curable two-part mix  11  is applied, at least sufficient to fill the skeletal voids. Closed mold (which may be used with a bag, not shown) then has a vacuum V drawn on it to draw out air and ensure investment of the skeleton with the mix prior to the mix curing. 
         [0070]      FIG. 5B  illustrates a gravity displacement method with an open mold in which skeleton  12  is laid, the skeleton closely configured to the floor and side walls of the mold. An applicator  18  with a forcing element  18   d  and two compartments  18   a / 18   b  applies a two-part mix  11 , which mixes in nozzle  18   c  of the applicator. Under the impetus of gravity, and/or with the assistance of a roller  22  or weight  26  (see  FIGS. 5E and 5F ), the uncured liquid or syrupy semi-solid mix will settle (or be forced) into the voids and, over time (typically between about 30 and 120 minutes), will cure in place. In an alternate embodiment, some of the voids may have some air trapped (which may be forced out with a “squeegee” roller  22  or other tool prior to curing), but at least the majority of the cells will be at least partially and preferably completely filled upon curing with the mix. 
         [0071]      FIGS. 5D and 5E  illustrate a moldless use of gravity or gravity assisted (tool  22 ) method. Here skeleton  12  is placed on release film  24  and uncured mix  11  is applied. It will soak in under its weight, and may be assisted by using tool  22  to force the uncured mix into the voids of skeleton  12 . The skeleton may be cut to shape first, before application of mix or cut later, after curing. Following curing of mix, the edges may be trimmed to the skeleton shape.  FIG. 5F  illustrates another method, moldless, of making a cellular metal gasket encapsulated with polymer gel. Here, like  FIG. 5D , the uncured mix is applied. A second release film  24  is laid over top the uncured mix and, on top of the second release film, a weight  26  is applied, to “force” uncured mix into the voids of the skeleton. Upon curing, weight  26  and release paper  24  are removed. The skeleton is then cut to shape (of workpiece, for example) before adding the polymer (encapsulated) or after curing. 
         [0072]      FIGS. 6 ,  7  and  8  illustrate various patterns of gaskets that may be diecut from the gasket stock that is removed from the mold following curing.  FIG. 6  illustrates a generally circular gasket,  FIG. 7  a generally rectangular gasket, and  FIG. 8  a generally straight-sided oval shape. These gaskets may be used in aircraft assemblies or other suitable environments, including EMI shielding applications. They typically have fastener holes that may have large internal openings, in one embodiment, for carrying electrical conductors to an external antenna. 
         [0073]    In addition to the body preferably comprising a gel, such as a polymer gel, the body may also have dispersed throughout thereof, many thousands of tiny electrically conductive particles or filler  20  (see the “dots” in  FIG. 5C ). Conductive parties may be all or partially metallic particles, such as those set forth in Publication U.S. 2013/0068519 (U.S. application Ser. No. 13/643,331, filed May 10, 2011), the contents of which are incorporated herein by reference. These at least partly conductive particles may be mixed with gel to form a top  21   c  and/or bottom  21   d  layer on the body. The conductive particulate filler  20  may include carbon, Graphenol, Graphene, and conductive metals, such as copper, nickel, silver, aluminum, tin, and alloys thereof, in one embodiment, nanoparticles; in another, macro-particles with diameters in the nano range. The conductive filler may be in amounts of 20-80% of total weight of the body (polymer gel) and may be any shape and size in the micron, submicron or other suitable range. Suitable shapes may be micron-size spheres, flakes, and fibers. In the &#39;519 publication, elastomeric polymers are set forth and any of those listed in that publication may be used as all or part of the body  14  set forth herein. 
         [0074]    The manufacturing of the cellular metal skeleton, in one embodiment, may start with an open cell polyurethane foam that is being metallized. Subsequently, the polyurethane is removed by pyrolosis. A cellular metal skeleton and the gaskets set forth herein may be used in applications where high electrical and thermal conductivity are of importance. In addition, where high strength and rigidity are required, the metal may be further chromised and further treated. The result is a three-dimensional, extremely porous (so as to take up the gasket body), electrically conductive (low resistance) structure of unexpected strength and wear resistance, and high corrosion resistance. 
         [0075]    Cellular metal can be cut with a shear knife or with circular saws; it may be laser cut, EDW machined, rolled, drilled, braised, etc. In one embodiment, it may include a pre-compressed thickness and may be compressed prior to application to the workpiece, to a desired thickness. While nickel foam may be used as a skeletal structure, copper foam and even titanium foam may be used or non-foam cellular metal skeleton of the same metals may be used. The nickel may be alloyed with chromium to form a nickel chromium skeleton material or further alloyed with aluminum to form a nickel chromium aluminum to improve oxidation resistance at high temperatures in other embodiments. 
         [0076]    The pore size of the cellular skeleton may be indicated by a pore range number or ppi (pores per linear inch) which may be termed pore density. Some embodiments of Applicant&#39;s skeleton has a ppi range of about 17 to 63, with an average pore diameter in a first range of about 0.01″ to 0.025″ and a second range of about 0.01″ to 0.125″. The gasket may have a thickness of about 0.055 to 0.150 inches in a first range of about 0.0125″ to about 0.50″ in a second range (compressed or uncompressed). Other embodiments of Applicant&#39;s cellular metal skeleton may have a ppi range of about 47-53 and an average pore diameter of about 0.4 mm and a thickness in the range of about 0.055 inches to 0.063 inches. Other embodiments may have a ppi range of about 27-33 and a thickness of about 0.125 inches. Yet another embodiment of Applicant&#39;s skeleton is nickel or aluminum with a ppi range of about 57-63, average pore diameter of about 0.35 mm and a thickness of about 0.055 inches. The pore density is typically uniform whether measured from x, y or z axis or any other orientation. 
         [0077]    Any of the aforementioned foams or any cellular metal may be compressed to a thickness of between about 70 to 90% of original thickness (reduced by 10-30% of original thickness cause by squashing cells) (up to 50% for Al) prior to application of the gel to form the gasket in a thickness range of about 0.0125 inches to 0.020 inches. This reduction is produced by a psi application of between about 30-350 psi. In one embodiment, the metal cellular skeleton produces a resistance of 2.5 milliohms or less when used in a polyurethane gel body, with the metallized skeleton pre-crushed to a thickness of between about 12.5 and 20 mil. In another embodiment, the metallized cellular skeleton is annealed before application of the gel. 
         [0078]    In one embodiment, a skeleton has an open cell structure of “struts”  12   d , a three-dimensional hollow skeletal metal where the cavities or voids cover more than in one embodiment about 90% of the total volume. It is very strong, yet has a low density compared to solid material. The densities may fall in the range of about 0.3 to 0.6 grams per cubic centimeter. The relative density indicates the mass ratio between the porous metal foam and the mass of the same volume of the basic solid material. Relative density (void/solid) may be, in one embodiment, less than about 5%, in another embodiment, less than 30%, in yet another embodiment about 2-25%. 
         [0079]    The skeleton may be metal foam (also called cellular metal) and can be any metal or alloy. The skeleton may be made from a number of processes. In one embodiment, aluminum is foamed in a liquid state and then cooled quickly to maintain its shape, and provide an effective skeleton when used with a polyurethane gel body. 
         [0080]    Compressive strength is proportional to the density of the metal. In one embodiment, an aluminum alloy of AA6061 is used for the metal. It may be heat treated to adjust strength and ductility. Ductility can be increased via annealing—at the cost of strength. Annealing is meant to increase ductility and eliminate, if desired, the effects of string hardening and cold work components or prior heat treatments, and to avoid any hardening effects through natural aging. 
         [0081]      FIGS. 9 ,  10 , and  11  illustrate the use of Applicant&#39;s novel cellular metal elastomeric gasket  10  on an aircraft fuel access door  106 . An aircraft fuel access door  106  may be mounted on a wing  102  of an aircraft using a retainer ring  108 . Removal of access door  106  provides access fuel tank  104 , typically located within the wing, for refueling of an aircraft. Access door  106  may be engaged with fasteners  112  to captured blind nuts  114  for fastening or free nuts  116  to hold the retainer ring  108  in place. Other fasteners may fasten through fuel access door  106  into retainer ring  108 . 
         [0082]    Between a shoulder on the perimeter of fuel access door  106 , Applicant&#39;s gasket  10  may be placed such that threading fasteners  112  through fuel access door  106  into the retainer ring provides compression between wing  102  and the shoulder of the fuel access door as seen in  FIG. 11 . In one embodiment, fasteners  112  fastening the door to the retainer ring is sufficient to compress the gasket until there is contact between the elements on top and on bottom (shoulder and wing), so that there is metal (access door)/metal (metal foam)/metal (metal ring) contact, generally caused by squeeze-out of the gel body during the process of fastening and compressing the fastener that is fastening the door to the retainer ring. In some instances, psi may be as high as about 2000 psi. 
         [0083]    Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. The skeletons are cellular metal, either metal foam or solid metal (which may have an open, unfilled core). On the contrary, various modifications of the disclosed embodiments will become apparent to those skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover such modifications, alternatives, and equivalents that fall within the true spirit and scope of the invention.