Abstract:
A honeycomb core includes a first wall secured to a second wall and a conductor disposed therebetween. A honeycomb cell is formed between the first wall and the second wall and the conductor is configured to extend through the cell and a point where the first wall and the second wall are secured together.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to the field of composite structures. 
     2. Description of Related Art 
     Many systems require signals or power, such as electrical, optical, or fluid signals or power, to be routed from one point to another point. Electrical signals and power are conventionally transmitted over wires or other such electrical conductors. Optical signals and power are conventionally propagated along optical fibers, optical waveguides, or the like. Fluid signals and power are conventionally transmitted through pipes, tubes, or other conduits. Electrical conductors, optical fibers or waveguides, and fluid conductors are often bundled into cables or “harnesses.” 
     Considerable effort and expense is expended, in many cases, to attach such cables to adjacent structural components. In some systems, such as aircraft or other vehicles, considerable effort and expense is also expended to route the cables or harnesses around structural and other components of the system. Moreover, cables and harnesses can significantly contribute to the overall weight of a system, which is of great importance in aircraft systems. 
     Some efforts have attempted to address these issues, particularly in the aircraft and other vehicle arts. Vehicles, and aircraft in particular, often include “sandwich” or “solid laminate” panels made from composite materials, such as glass fibers, carbon fibers, aramid fibers, or the like disposed in a polymeric matrix. Sandwich panels typically include a core adhesively bonded between face sheets or “skins.” Sandwich panel face sheets and solid laminate panels typically include a plurality of adhesively bonded layers or plies of composite material. 
     Electrical and optical conductors have been embedded in sandwich panel face sheets or “skins” and in solid laminate panels. A sandwich structure, however, typically has thin face sheets or skins. The thickness of the skins is principally determined by the structural requirements of the sandwich structure. Embedding conductors in the face sheets or skins often increases the thickness of the face sheets or skins to unacceptable levels. For example, thick skins are heavier than thinner skins. Moreover, thick skins may interfere with other structure and systems near the skins. 
     There are many ways of routing conductors well known in the art; however, considerable room for improvement remains. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the invention are set forth in the appended claims. However, the invention itself, as well as a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, in which the leftmost significant digit(s) in the reference numerals denote(s) the first figure in which the respective reference numerals appear, wherein: 
         FIG. 1  is a stylized, top, plan, exploded view of an illustrative embodiment of a honeycomb core including an embedded conductor; 
         FIG. 2  is a stylized, top, plan view of the honeycomb core of  FIG. 1 ; 
         FIGS. 3-7  are cross-sectional views of various alternative constructions of the honeycomb core of  FIG. 1 ; 
         FIG. 8  is a top plan view of an illustrative embodiment of a honeycomb core including a plurality of embedded conductors; 
         FIG. 9  is a side, elevational, cross-sectional view of a first illustrative embodiment of a sandwich panel incorporating a honeycomb core of the present invention; and 
         FIG. 10  is a side, elevational, cross-sectional view of a second illustrative embodiment of a sandwich panel incorporating a honeycomb core of the present invention. 
     
    
    
     While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Illustrative embodiments Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer&#39;s specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as “above,” “below,” “upper,” “lower,” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction. 
     The present invention represents a honeycomb core having an embedded conductor, such as an electrical, optical, or fluid conductor. For the purposes of this disclosure, the term “honeycomb core” means a core material comprising a plurality of interconnected cell walls that define a plurality of cells. While many honeycomb core materials define hexagonal cells, the scope of the present invention encompasses core materials that define cells of other shapes, such as square, rectangular, and the like. The honeycomb core of the present invention comprises a first formed wall, a second formed wall, and a conductor disposed between the first formed wall and the second formed wall. The first formed wall is adhesively bonded to a first side of the conductor or to a first side of insulation disposed about the conductor, if such insulation is present. The second formed wall is adhesively bonded to a second side of the conductor or to a second side of the insulation disposed about the conductor, if such insulation is present. The walls define a plurality of cells through which the conductor extends. The conductor extends from edges of the honeycomb core, so that the conductor may be connected to other equipment, devices, systems, and the like. 
       FIG. 1  is an exploded view of an illustrative embodiment of a honeycomb core  101 . As is described herein, honeycomb core  101  may form a portion of a larger honeycomb core. In the illustrated embodiment, honeycomb core  101  comprises a first formed wall  103 , a second formed wall  105 , and a conductor  107 . Formed walls  103  and  105  may comprise paper, unwoven fibers, woven fibers, or any other suitable material for honeycomb core  101 . Conductor  107  is disposed between first formed wall  103  and second formed wall  105  and may comprise an electrical conductor, an optical conductor, and/or a fluid conductor. Portions  109  of first formed wall  103  are adhesively bonded to a first side  113  of conductor  107 . Portions  115  of second formed wall  105  are adhesively bonded to a second side  119  of conductor  107 . It should be noted, however, that the adhesive for bonding walls  103  and  105  to conductor  107  may comprise adhesive coatings, such as coatings generated when walls  103  and  105  are immersed in a resin bath. Moreover, the adhesive may comprise adhesive impregnated about woven or unwoven fibers in walls  103  and  105  made from composite “pre-preg” material. 
     It should be noted that, in some embodiments, conductor  107  may be formed of a bare electrical conductor or may be formed of an electrical conductor with insulation disposed about the conductor. Thus, while the present disclosure describes first wall  103  and second wall  105  as being adhesively bonded to conductor  107 , the scope of the present invention encompasses first wall  103  and second wall  105  being adhesively bonded to insulation disposed about conductor  107 . In some embodiments wherein conductor  107  comprises a bare electrical conductor, i.e., without insulation disposed about conductor  107 , adhesive used to bond walls  103  and  105  to conductor  107  electrically insulate conductor  107  from walls  103  and  105 . It should be noted that walls  103  and  105  may themselves serve as an insulator when walls  103  and  105  are constructed of a low dielectric or insulating material. As is discussed herein, the scope of the present invention encompasses a plurality of conductors, such as conductor  107 , disposed between walls  103  and  105 . 
     Referring now to  FIG. 2 , walls  103  and  105  form one or more cells  201  (only one indicated in  FIG. 2  for clarity) of honeycomb core  101  when walls  103  and  105  are adhesively bonded to conductor  107 . In the illustrated embodiment, walls  103  and  105  are formed to define recesses  121  and  123  (only one each indicated in  FIG. 1 ), respectively. When walls  103  and  105  are adhesively bonded to conductor  107 , recesses  121  and  123  form cells  201 . Conductor  107  extends through cells  201  and extends from a first edge  203  of honeycomb core  101  and a second edge  205  of honeycomb core  101 . 
       FIG. 3  depicts a cross-sectional view of one particular embodiment of honeycomb core  101 . In the illustrated embodiment, conductor  107  is a bare electrical conductor, which is electrically insulated from walls  103  and  105  by layers  301  and  303  of adhesive. Adhesive layers  301  and  303  bond walls  103  and  105  to conductor  107 . In one embodiment, adhesive layers  301  and  303  are provided as separate layers, such as adhesive film, disposed between wall  103  and conductor  107  and between wall  105  and conductor  107 , respectively. In another embodiment, adhesive layers  301  and  303  are provided by adhesive disposed on walls  103  and  105 , such as from a resin bath. In yet another embodiment, adhesive layers  301  and  303  are provided by adhesive in composite “pre-preg” that makes up walls  103  and  105 . 
       FIG. 4  depicts a cross-sectional view of an embodiment alternative to the embodiment of  FIG. 3 . In the embodiment of  FIG. 4 , insulating layers  401  and  403  are disposed between conductor  107  and adhesive layers  301  and  303 , respectively. Other aspects of the embodiment of  FIG. 4  correspond to the embodiment of  FIG. 3 . It should be noted, however, that the scope of the present invention encompasses configurations wherein only one of insulating layer  401  and  403  is present. 
       FIG. 5  depicts a cross-sectional view of yet another embodiment alternative to the embodiment of  FIG. 3 . In the embodiment of  FIG. 5 , a plurality of conductors  107   a - 107   c  are disposed in an insulating layer  501 . Adhesive layers  301  and  303  bond walls  103  and  105 , respectively, to insulating layer  501 . It should be noted that any suitable number of conductors, such as conductors  107   a - 107   c , may be disposed in insulating layer  501 . Moreover, while conductors  107   a - 107   c  are depicted as being rectangular in cross-section, the scope of the present invention is not so limited. Rather, the conductor or conductors in any of the embodiments disclosed herein may exhibit any suitable shape, such as substantially round. For example, conductors  107   a - 107   c  and insulating layer  501  may form a “ribbon cable” that is disposed between and adhesively bonded to walls  103  and  105 . In one embodiment, the conductor or conductors of the present invention comprise a metallic foil. 
     As depicted in  FIG. 6 , conductors  107   a - 107   c  may be disposed in separate insulating layers  601   a - 601   c , respectively. Insulating layers  601   a - 601   c  are disposed in an adhesive layer  603 , which bonds insulating layers  601   a - 601   c  to walls  103  and  105 . 
     Moreover, as depicted in  FIG. 7 , honeycomb core  101  may comprise a plurality of conductors  701   a - 701   c  disposed on a substrate  703 , forming a printed wiring board or element  705 . Printed wiring element  705  is disposed between and adhesively bonded to walls  103  and  105  by adhesive layers  707  and  709 , respectively. Note that an insulating layer, such as insulating layer  401 , may be disposed between conductors  701   a - 701   c  and adhesive layer  707 . 
       FIG. 8  depicts an illustrative embodiment of a honeycomb core  801 . Honeycomb core  801  comprises a plurality of formed walls  803  (only one indicated in  FIG. 8  for clarity). Conductors are disposed between at least some of the plurality formed walls  803 . In the illustrated embodiment, conductor  805  is disposed between formed walls  803   a  and  803   b  in a fashion corresponding to the embodiment of  FIGS. 1 and 2 . In other words, formed wall  803   a  corresponds to formed wall  103 , formed wall  803   b  corresponds to formed wall  105 , and conductor  805  corresponds to conductor  107 . Formed walls  803   a  and  803   b  define cells  807  through which conductor  805  extends. Conductor  805  also preferably extends from a first edge  809  and a second edge  811  of honeycomb core  801 , so that conductor  805  can be coupled with other equipment, devices, systems, or the like. 
     In the illustrated embodiment, conductors do not extend through cells  813  of honeycomb core adjacent to cells  807 , through which conductor  805  extends. In other embodiments, or within the same honeycomb core, conductors may extend through cells that are adjacent to one another. For example, still referring to  FIG. 8 , a conductor  815  is disposed between and adhesively bonded to formed walls  803   c  and  803   d , a conductor  817  is disposed between and adhesively bonded to formed walls  803   d  and  803   e , and a conductor  819  is disposed between and adhesively bonded to formed walls  803   e  and  803   f . Thus, one portion of honeycomb core  801  includes conductors, i.e., conductors  815 ,  817 , and  819 , that extend through adjacent cells and are disposed between adjacent formed walls, i.e., formed walls  803   c ,  803   d ,  803   e , and  803   f . In this particular embodiment, conductors  815 ,  817 , and  819  are terminated at connectors  821  and  823  proximate edges  809  and  811 , respectively, of honeycomb core  801 , so that conductors  815 ,  817 , and  819  may be coupled with other conductors, devices, systems, and/or equipment, or to adjacent honeycomb core having conductors embedded therein. 
     Adjacent conductors, however, are not necessarily terminated in common connectors. For example, still referring to  FIG. 8 , a conductor  825  is disposed between and adhesively bonded to formed walls  803   g  and  803   h , while a conductor  827  is disposed between and adhesively bonded to formed walls  803   h  and  803   i.    
     It should be noted that, while conductors  107 ,  805 ,  815 ,  817 ,  819 ,  825 , and  827  are depicted in the Figures as extending substantially linearly through honeycomb core  101  or  801 , the scope of the present invention is not so limited. Rather, conductors of the present invention may take any suitable route through a honeycomb core, such as a non-linear or circuitous route. 
       FIG. 9  depicts a side, elevational, cross-sectional view of a first illustrative embodiment of a sandwich panel  901 . Panel  901  comprises an upper skin  903 , a lower skin  905 , and a honeycomb core  907  adhesively bonded to upper skin  903  and lower skin  905 . Conductors  909  and  911  are embedded in honeycomb core  907 , as described herein concerning the embodiments of  FIGS. 1-8 . 
     As shown in  FIG. 10 , it should be noted that some or all of the cells of honeycomb core  907 , such as cells  913   a - 913   d  (shown in  FIG. 9 ), of honeycomb core  907  may be partially or substantially completely filled with an aerogel  1001 , for example, as described in commonly-owned U.S. patent application Ser. No. 10/514,753, published as U.S. Published Patent Application 2005/0208321; and/or Patent Cooperation Treaty Application Serial No. PCT/US2005/013675, published as WO2006/115477, each of which is incorporated herein by reference in its entirety for all purposes. Generally, aerogels are a class of open-celled, mesoporous, solid materials possessing no less than 50% porosity by volume. Typically, aerogels are composed of 90-99.8% air, with densities ranging from 1.9 mg/cm 3  to around 150 mg/cm 3 . At the nanoscale, an aerogel structurally resembles a sponge and is composed of a network of interconnected nanoparticles. Aerogels can be composed of a variety of materials including silica, alumina, zirconia, and the like. Aerogel  1001  improves the thermal insulation properties of panel  901 . In some embodiments, aerogel  1001  includes a radar-absorbing material, such as carbon. Aerogel  1001  may take on the form of a single element or may be in granular form. 
     The present invention provides significant advantages, including: (1) providing a lower-weight means for conducting power or signals; (2) providing a means for conducting power or signals through sandwich panels without embedding conductors in the skins of the sandwich panels; (3) providing functionality, in addition to structural functionality, to honeycomb core sandwich panels; and (4) providing a means for conducting power or signals through a sandwich panel without increasing the overall thickness or volume of the panel. 
     The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. It is apparent that an invention with significant advantages has been described and illustrated. Although the present invention is shown in a limited number of forms, it is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof.