Patent Publication Number: US-6910996-B1

Title: Method for producing a honeycomb structure and apparatus therefor

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the filing benefit under Title 35, United States Code, §119(e) of U.S. provisional application 60/414,265, filed Sep. 27, 2002. 
    
    
     TECHNICAL FIELD 
     The present invention generally pertains to honeycomb structures, and more particularly to a method and apparatus for corrugating and connecting deformable sheets to produce a honeycomb structure. 
     BACKGROUND OF THE INVENTION 
     The advantages of using composite honeycomb core in low-density sandwich structures have been well documented and understood for many years. Unfortunately the technology designed to produce such cores has not kept up with the advances in composite material technologies. The standard methods of composite core manufacturing tend to exhibit such problems as release residue in the inner core structure, non-uniform node adhesion, inaccurate geometrical structure, as well as a non-constant tg (glass transition temperature) throughout the volume. Due to these inadequacies of construction the structural and dielectrical properties of the core tend to be compromised. 
     The standard method for creating a composite core involves the stacking of aluminum rods over sheets of unidirectional or fabric prepreg. This process creates a large block of mostly aluminum that is generally heated in some form of a standard oven using convection as the method of heat transfer to the outer edges of the rods and then through conduction for the center of the block. The temperature curve with respect to block thickness will take tens of minutes to level off resulting in a non-even cure rate. Thus when the resin in the center of the block is just starting to advance the external edges could already be fully cured. This process will never be able to yield a core that has an even tg. The energy required to heat large blocks, tens of cubic feet, becomes astronomically large. When heating a large block the thermal difference from exterior to interior will result in differentials of thermal expansion. These differentials will show themselves as points of node separation as well as non-uniform cell size in which the structural, dielectrical and thermal advantages of the core are compromised. 
     A very large problem common with the aluminum rod composite core manufacturing process is due to the release agent applied to each aluminum rod which inherently a necessary step required to extract the rods from the core. The release agent tends to leave a silicon coating on the core. Structurally this inhibits a full bond between the core and skin of the structure. The residue also adversely affects the dielectrical properties of the core. 
     The lack on uniformity in cell geometry is a key factor in inhibiting the progression of composite honeycomb being applied to the field of R.F. cancellation in the aerospace market. Presently syntactic core is generally used due to its ease in dielectrical loading but structurally honeycomb core material is much more advantages. To control the dielectrical properties of composite honeycomb core, the core is created through an older method than previously stated, instead of using aluminum rods a nomex fabric is lightly impregnated with a resin, bonded at nodes and expanded much like the creation of an aluminum honeycomb core. The nomex style core is geometrically non-accurate and dialectically useless for R.F. cancellation. To make the core useful it is repeatedly dipped in a resin of particular dialectic properties until the desired effects are achieved. This works to a point but again dose not take advantage of the uniformity and controllability of the advance composite prepregs. 
     To overcome the aforementioned shortcomings, the present invention comprises a honeycomb production apparatus that will eliminate the present problems of composite core manufacturing and take full advantage of the advances in modern composite technologies. 
     The apparatus of the present invention produces composite honeycomb core through the corrugation of individual sheets of resin-impregnated fibers or fabric (prepreg). The corrugated sheets are stacked and adhered together using a node adhesive film. The resulting core will be extremely uniform, heat formable, absent of release residue, capable of extremely large ribbon lengths and will have dielectric properties controlled by the resin and fiber content. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method and apparatus for producing a honeycomb structure wherein a continuous automated production process is employed. The process includes:
         (a) providing a first sheet of deformable material stacked upon a second sheet of deformable material;   (b) passing the stacked first and second sheets of deformable material through a first conveyer (corrugator) wherein the first and second sheets of deformable material are corrugated by the first conveyor;   (c) separating the first sheet of corrugated deformable material from the second sheet of deformable material as they exit the first conveyor;   (d) applying an adhesive to the second sheet of deformable material;   (e) passing the first and second sheets of deformable material through a second conveyer wherein the corrugated first and second sheets of deformable material are connected to form a single layer honeycomb structure; and,   (f) connecting a plurality of single layer honeycomb structures to form a honeycomb structure of a desired thickness.       

     The development of the present invention comprises a necessary step in the progression of advancing composite core technologies and signifies a significant leap in present honeycomb core construction technologies. The creation of geometrically accurate large heat formable composite honeycomb cores with customer specified resin and fiber properties at a cost comparable to standard composite honeycomb core opens the door to new honeycomb core applications in previously inapplicable fields. 
     Other aspects of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation view of a system for producing a honeycomb structure from sheet of deformable material in accordance with the present invention; 
         FIG. 2  is an enlarged side elevation view of a first conveyor (Station  2  of  FIG. 1 ); 
         FIG. 3  is an enlarged view of area  3  of  FIG. 2 : 
         FIG. 4  is an enlarged fragmented perspective view of interlocking rods; 
         FIG. 5  is an enlarged fragmented side elevation view of the input portion of the first conveyor; 
         FIG. 6  is an enlarged fragmented side elevation view of the output portion of the first conveyor; 
         FIG. 7  is an enlarged side elevation view of a portion of a first corridor of the first conveyor; 
         FIG. 8  is a perspective view of the first conveyor; 
         FIG. 9  is an enlarged side elevation view of Station  1  of  FIG. 1 ; 
         FIG. 10  is an enlarged side elevation view of a five layer sandwich; 
         FIG. 11  is an enlarged view of area  11  of  FIG. 10 ; 
         FIG. 12  is an enlarged side elevation view of Station  3  of  FIG. 1 ; 
         FIG. 13  is an enlarged side elevation view of a second conveyor; 
         FIG. 14  is an enlarged view of area  14  of  FIG. 13 ; 
         FIG. 15  is an enlarged fragmented perspective view of interlocking rods the second conveyor; 
         FIG. 16  is an enlarged side elevation view of a portion of a second corridor of the second conveyor; 
         FIG. 17  is an enlarged side elevation view of the single layer honeycomb structure produced by the second conveyor; 
         FIGS. 18 through 21  are enlarged side elevation views which depict the process of building a honeycomb structure of a desired depth; 
         FIG. 22  is a perspective view of an embodiment of Station  2 ; and, 
         FIG. 23  is a perspective view of an embodiment of Station  3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring initially to  FIG. 1 , there is illustrated a side elevation view of a system for producing a honeycomb structure from sheet of deformable material in accordance with the present invention, generally designated as  20 . System  20  comprises a continuous production apparatus wherein elongated sheets of deformable material are automatically corrugated and then connected to form the honeycomb structure. System  20  has five Stations designated Station  1  through Station  5 . In an embodiment of the invention, the deformable material is “prepreg” which is a resin based material available from YLA, Inc. 2970 Bay Vista Ct., Benica, Calif. 94510. Prepreg thickness of around 0.005 inches ±0.002 inches have been found useful. In the shown embodiment, at Station  1  first  22  and second  24  sheets of a deformable material are interleaved with three sheets of release ply  26  to form a five layer sandwich (also refer to  FIG. 11 ) which is introduced into Station  2 . Release ply  26  is available from Airtech, Inc. 5700 Skylab Road, Huntington Beach, Calif. 92647. A release ply  26  thickness of around 0.001 inches has been found useful. The first  22  and second  24  sheets of deformable material are dispensed from first roller  28  and second roller  30  respectively, and release ply  26  is dispensed from third, fourth, and fifth rollers  29 . Rollers  31  remove a backing form the first  22  and second  24  sheets of deformable material. 
     At Station  2  the five layer sandwich is corrugated by a first conveyor  32  having two counter-rotating belts  34  and  36 . Belts  34  and  36  are constructed of interlocking rods  50  wherein each rod has a tooth  52  (also refer to  FIG. 4 ). The teeth  52  of belt  34  mesh with the teeth of belt  36 , so that as the five layer sandwich passes through first conveyor  32  the sandwich is corrugated by teeth  52 . 
     At Station  3  first sheet  22  (which is now corrugated) is separated from second sheet  24  (which is also corrugated). The center layer of release ply  26  is removed, however a layer of release ply  26  remains attached to the top of first sheet  22  and to the bottom of second sheet  24 . A layer of adhesive is then applied to the top of second sheet  24  by adhesive applicator  38 , and then first sheet  22  and second sheet  24  are routed to Station  4 . 
     At Station  4  first sheet  22  and second sheet  24  are connected by the adhesive as they pass through second conveyor  40 . Second conveyor  40  has two counter-rotating belts  42  and  44 . Belts  42  and  44  are also constructed of interlocking rods  50  wherein each rod has a tooth  52 (also refer to  FIG. 15 ). The teeth  52  of belt  42  aligns (does not mesh, but rather the top of the teeth  52  come together, refer also to  FIG. 16 ) with the teeth of belt  44  so that as the first  22  and second  24  sheets pass through second conveyor  40  they are connected to form a double sheet which defines hollow honeycomb shape cells (a single layer honeycomb structure). Belts  42  and  44  also contain indexing teeth  78  (refer to  FIG. 15 ) which ensure that the tooth to tooth alignment of second conveyor  40  is continuously maintained. 
     At Station  5  release ply  26  is removed from first sheet  22  and second sheet  24 . A second adhesive applicator  46  applies a second adhesive to each single layer honeycomb sheet (sturcture) exiting Station  4 . The single layer honeycomb structure is then cut by cutter  48  and stacked with a plurality of other similarly cut single layer honeycomb structures to form a honeycomb structure of a desired thickness (refer also to  FIGS. 18–21 ). 
     Now referring to  FIG. 2 , there is illustrated an enlarged side elevation view of first conveyor  32 . First conveyor  32  includes first belt  34  of interlocking rods  50  (refer also to  FIGS. 3 and 4 ). Each rod  50  has a tooth  52 , which in the shown embodiment has a half-hexagonal shape. First belt  32  rotates in a first direction  54  (counterclockwise as shown). First conveyor  32  also includes a second belt  36  of interlocking rods  50  having teeth  52  having a half-hexagonal shape. Second belt  36  rotates in a second direction  56  (clockwise as shown) opposite from first direction  54 . First  34  and second  36  belts form a first corridor  58  wherein teeth  52  of first belt  32  mesh with teeth  52  of second belt  36  (refer also to  FIG. 7 ). First belt  34  and second belt  36  can traverse a radius such as around rubber coated drive rollers  35 , but when laid flat in first corridor  58  they form the necessary half-hexagonal shape to produce a half-hexagon corrugated sheet. 
     When a sheet of deformable material  500  is passed through first corridor  58 , the deformable material  500  is crimped into a corrugated half-hexagon shape by teeth  52  of first belt  34  and second belt  36 . A pluralilty of corrugated sheets may then be connected by and adhesive to form a honeycomb structure. 
     First conveyor  32  includes a first heated pressure plate  60  which contacts first belt  34  in first corridor  58 . First heated pressure plate  60  heats first belt  34  and urges first belt  34  toward second belt  36 . In an embodiment of the invention, first heated pressure plate  60  comprises flat one inch thick pieces of aluminum having heat strips on their back side to evenly heat rods  50  and hence the deformable material  500 . First conveyor  32  also includes a second heated pressure plate  62  which contacts second belt  36  in first corridor  58 . Second heated pressure plate  62  heats second belt  36  and urges second belt  36  toward first belt  34 . A first friction reducing material  64  (such as a sticky backed sheet of Teflon) is disposed between first heated pressure plate  60  and first belt  34 , and a second friction reducing material  66  is disposed between second heated pressure plate  62  and second belt  36 . The friction reducing material  64  and  66  ensures that rods  50  can traverse first corridor  58  with little resistance. The pressure and heat during passage through first corridor  58  facilitates the corrugation process. 
       FIG. 3  is an enlarged view of area  3  of  FIG. 2  showing an end view of one interlocking rod  50  having a tooth  52 . 
       FIG. 4  is an enlarged fragmented perspective view of the interlocking rods  50  of second belt  36  in first corridor  58  (also refer to  FIG. 3 ). In an embodiment of the invention interlocking rods  50  are extruded aluminum. 
       FIG. 5  is an enlarged fragmented side elevation view of the input portion of first conveyor  32 . Deformable material  500  is feed in direction  502  between first belt  34  and second belt  36  and into first corridor  58 . 
       FIG. 6  is an enlarged fragmented side elevation view of the output portion of first conveyor  32 . Deformable material  500  exits first corridor  58  in direction  502 . Because the teeth  52  of first belt  34  mesh with the teeth  52  of second belt  36 , deformable material  500  is corrugated as it passes through first corridor  58  (refer also to  FIG. 7 ). 
       FIG. 7  is an enlarged side elevation view of a portion of first corridor  58  of first conveyor  32  showing first belt  34 , second belt  36 , rods  50  and meshing teeth  52 . The deformable material  500  is bent by the meshing teeth  52  into a corrugated shape. 
       FIG. 8  is a perspective view of first conveyor  32  showing first belt  34 , second belt  36 , with sheet of deformable material  500  being feed into first corridor  58 . 
       FIG. 9  is an enlarged side elevation view of Station  1  of  FIG. 1 . System  20  includes first  28  and second  30  rollers which feed first  22  and second  24  sheets of deformable material into first corridor  58  of first conveyor  32  (also refer to  FIG. 2 ). Third, fourth, and fifth rollers  29 , feed the three layers of release ply  26  into first corridor  58  to create a five layer sandwich  68  (refer to  FIGS. 10 and 11 ) which is then corrugated by first conveyor  32 . Five layer sandwich  68  comprises first  22  and second  24  sheets of deformable material disposed between three layers of release ply  26  (refer to  FIG. 11 ). The three layers of release ply  26  separate the two sheets of prepreg from each other as well as inhibit the bonding of the prepreg to the corrugation device of second conveyor  40 . Rollers  31  collect a backing from deformable material before it enters first conveyor  32 . Five layer sandwich  68  is then corrugated by first conveyor  32  as the sandwich passes through first corridor  58  (refer also to  FIG. 12 ). 
     Prepreg is a material that combines fibers and resins in a homogeneous nature. It was designed originally to make composite structures more uniform and structurally predictable. For example most fiberglass boats were and sometimes and still are created by a method known as a wet lay-up; in which sheets of dry fiberglass fabric are placed on a mold or frame and a epoxy resin much like a basic glue is applied to create a rigid structure. For this example prepreg could be used in which the fiberglass fabric comes on a roll with a heat cured epoxy resin system pre-dispersed evenly throughout the fabric. The boat builder will now be able to know exactly how much resin and how much fabric is in each section of the boat yielding a boat with the optimum strength to weight ratio. 
     Prepreg commonly comes on a release paper (ply) that can be used in the corrugation process but if so desired the release paper can be removed and other release films can be used such as Tedlar or FEP. Using the release films such as the ones mentioned tends to yield a more accurate hexagonal geometry in the final block of core but increases final block costs. The apparatus of the present invention can corrugate a large range of prepregs fabrics composed of Fiberglass, Carbon fibers, Kevlar along with other exotic materials such as Spetra and PBO. These materials can be combined with many types of resin systems such as epoxies, cyanates, polyesters and ceramics, yielding a large variety of possible Honeycomb core materials. 
       FIG. 10  is an enlarged side elevation view of five layer sandwich  68  showing first  22  and second  24  sheets surrounded by release ply  26 . 
       FIG. 11  is an enlarged view of area  11  of  FIG. 10 , showing five layer sandwich  68  as it enters first conveyor  32 . As five layer sandwich  68  is passed through first corridor  58  of first conveyor  32 , the entire five sheet sandwich  68  is corrugated, and then exists first conveyor  32  and is further processed at Station  3  (refer also to  FIG. 1 ). 
       FIG. 12  is an enlarged side elevation view of Station  3  of  FIG. 1  wherein the corrugated first  22  and second  22  sheets of deformable material are separated and the central layer of release ply  26  is removed from five layer sandwich  68 . System  20  includes a sixth roller  70  which collects the central layer of release ply  26  as the corrugated five layer sandwich  68  exists first corridor  58  of first conveyor  32 . System  20  also includes a seventh roller  72  which separates corrugated first sheet  22  of deformable material and an attached layer of release ply  26  from the corrugated second sheet  24  of deformable material and an attached layer of release ply  26 . The physical separation of first sheet  22  and second sheet  24  is necessary to allow clearance for the application of an adhesive (also called a node adhesive) to second sheet  24 . System  20  further includes an adhesive applicator  38  which applies an adhesive to the corrugated second sheet  24  of deformable material. In an embodiment of the invention the adhesive is a resin film (refer also to  FIG. 23  and the discussion pertaining thereto). 
     Now referring to  FIG. 13 , there is illustrated an enlarged side elevation view of second conveyor  40 . Second conveyor  40  includes third belt  42  of interlocking rods  50  (refer also to  FIGS. 14 and 15 ). Each rod  50  has a tooth  52 , which in the shown embodiment has a half-hexagonal shape. Third belt  42  rotates in a first direction  54  (counterclockwise as shown). Second conveyor  42  also includes a fourth belt  44  of interlocking rods  50  having teeth  52  having a half-hexagonal shape. Fourth belt  44  rotates in a second direction  56  (clockwise as shown) opposite from first direction  54 . Third  42  and fourth  44  belts form a second corridor  74  wherein teeth  52  of third belt  42  align (not mesh) with teeth  52  of fourth belt  44  (refer also to  FIG. 16 ). It is important to note that the alignment of teeth  52  of third belt  42  and fourth belt  44  of second conveyor  40  differs from the alignment of teeth  52  of first belt  34  and second belt  36  of first conveyor  32 . In first conveyor  32  the teeth  52  mesh as is shown in  FIG. 7 . However in second conveyor  40  the teeth  52  align as is shown in  FIG. 16 . “Align” means that the teeth  52  are aligned along an axis  75  and therefore combine to form a hexagonal void  76  which produces the single layer honeycomb structure  510  of the present invention. 
     When the corrugated first  22  and second  24  sheets of deformable material are simultaneously passed through second corridor  74 , corrugated first sheet  22  of deformable material is joined by the adhesive (applied to second sheet  24  at Station  3 ) to corrugated second sheet  24  of deformable material to form a single layer honeycomb structure  510  as is shown in  FIG. 17 . That is the corrugated first  22  and second  24  sheets of deformable material occupy the hexagonal void  76  (refer also to  FIG. 16 ) as they pass through second corridor  74 , and therefore produce a single layer honeycomb structure  510 . 
     Third belt  42  and fourth belt  44  each include a plurality of rods  50  which have an indexing tooth  78  (refer also to  FIGS. 14 and 15 ). In the shown embodiment, indexing teeth  78  are periodically spaced around third belt  42  and fourth belt  44 . Indexing teeth  78  cause the teeth  52  of third belt  42  and fourth belt  44  to align rather than mesh (refer to  FIG. 16 ). Indexing teeth  78  also have a half-hexagonal shape (refer to  FIG. 15 ). 
     Second conveyor  40  includes a third heated pressure plate  80  which contacts third belt  42  in second corridor  74 . Third heated pressure plate  80  heats third belt  42  and urges third belt  42  toward fourth belt  44 . Second conveyor  40  also includes a fourth heated pressure plate  82  which contacts fourth belt  44  in second corridor  74 . Fourth heated pressure plate  82  heats fourth belt  44  and urges fourth belt  44  toward third belt  42 . As with first conveyor  32 , a friction reducing material  64  and  66  is utilized easy to easy belt passage through second corridor  74 . The pressure and heat cures the adhesive thereby ensuring that the two sheets are fixedly connected. 
       FIG. 14  is an enlarged view of area  14  of  FIG. 13 , showing interlocking rods  50  having teeth  52  and indexing tooth  78 . 
       FIG. 15  is an enlarged fragmented perspective view of interlocking rods  50  of second conveyor  40 . It is noted that indexing teeth  78  are only disposed on the outer edges of rods  50 . This permits the corrugated first  22  and second  24  sheets to pass through the large area between the indexing teeth  78 . 
       FIG. 16  is an enlarged side elevation view of a portion of second corridor  74  of second conveyor  40 . Corrugated first  22  and second  24  sheets have been connected to form a single layer honeycomb structure  510  (also refer to  FIG. 17 ). It is noted how the teeth  52  align rather than mesh as in  FIG. 7 . It is also noted that at this stage layers of release play  26  are still attached to the first  22  and second  24  sheets (refer also to  FIG. 17 ). 
       FIG. 17  is an enlarged side elevation view of the single layer honeycomb structure  510  produced by second conveyor  40 . First sheet  22  has been attached to second sheet  24  with the adhesive applied at Station  3 . A layer of release ply  26  is disposed on top of first sheet  22 , and another layer of release ply  26  is disposed on the bottom of second sheet  24 . 
     At Station  5  (refer to  FIG. 1 ) the continuous stream of double plied sheets which exit from Station  4  are cut to the final desired length. The next step in the process is to stack the cut sheets to form the final block of honeycomb core. First the release ply is removed from each side of the material. Then the double plied sheets are infused with a second resin system in which instead of adhering to just the nodes it is of a viscosity and rigidity such that is spans over the nodes as well as the space between the nodes. The double plied sheets with the top resin film are then stacked such that the sheets fall into each other. This process creates a unique honeycomb core that consists of cell walls that are two plies of prepreg and node contact points that are of 4 plies of prepreg. The entire block is then placed in an oven with a simple flat weight on the top to inflict a constant gravity based force down on to the curing core. The cure cycle will be such that the resin film bonding the double plies together as well as all of the prepreg will be fully cured. The end result is a block of honeycomb core that can be made at any standard cell size and can be cut to a desired thickness or machined down into a desired shape. 
       FIGS. 18 through 21  are enlarged side elevation views which depict the process of building a honeycomb structure of a desired depth (thickness) as is performed at Station  5  (refer to  FIG. 1 ). First the two layers of release ply  26  are removed from the first single layer honeycomb structure  510  ( 1 ) which exists Station  4 . Then a second adhesive  84  is applied to the top of the first single layer honeycomb structure ( 1 ), and the structure is cut to a desired length. In an embodiment of the invention, adhesive  84  is a sheet of resin film which includes a rubber additive. Next a similarly processed second honeycomb sheet ( 2 ) is positioned above first honeycomb sheet ( 1 ) as is depicted in  FIG. 19 . Then as shown in  FIG. 20 , a second single layer honeycomb structure ( 2 ) is meshed with first single layer honeycomb structure ( 1 ) wherein the adhesive bonds the two sheets together. It is noted that the single layer honeycomb structure do not align as at Station  4 , but rather mesh as is shown in  FIG. 20 . The above process is repeated until a honeycomb structure of a desired thickness is achieved such as in  FIG. 21 . In  FIG. 21 , eight single layer honeycomb structures  510  have been connected. It is noted that the wall thickness of each of the honeycomb cells varies. Referring to  FIG. 21 , the two horizontal walls of each honeycomb cell are four layers of prepreg thick, while the four angled vertical walls are two layers of prepreg thick. The present invention can be used to create honeycomb structures have various cell sizes. Cell sizes of ⅛ inch, ⅜ inch, and ¼ inch have been found useful. 
       FIG. 22  is a perspective view of an embodiment of Station  2  (first conveyor  32 ). Pressure is maintained on the corrugated material by means of four large bolts  100 . This pressure holds the corrugated material while the heat advances the resin allowing for the prepreg to gel. The gel point of a resin is when the viscous resin turns into a solid locking the material in its corrugated shape. 
       FIG. 23  is a perspective view of an embodiment of Station  3  (adhesive application  38 ). The adhesive applicator  38  is a simple device in which the exposed prepreg passes under a heated resin applicator roll  200 . The heated resin applicator roll  200  is a steel roll heated with a fixed heating element traversing through the center of the roll. A smaller fixed resin bath roll  202  creates a pinching point in which only a certain thickness of resin film adhesive is allowed onto the application roll  200 . Two wedges  204  at each end of the bath restrict the resin in the bath from flowing out of the sides. This process yields a controllable thickness of resin film that rolls onto the nodes (top wall) of the corrugated prepreg as it passes underneath but applies no adhesive into the valleys of the corrugated prepreg. 
     In terms of use, a method for producing a honeycomb structure includes:
         (a) providing a first sheet  22  of deformable material stacked with a second sheet  24  of deformable material;   (b) providing a first conveyor  32  including:
           a first belt  34  of interlocking rods  50 , each rod  50  having a tooth  52 , first belt  34  rotatable in a first direction  54 ;   a second belt  36  of interlocking rods  50 , each rod  50  having a tooth  52 , second belt  36  rotatable in a second direction  56  opposite from first direction  54 ;   first  22  and second  24  belts forming a first corridor  58  wherein the teeth  52  of the first belt  34  mesh with the teeth  52  of second belt  36 ;   
           (c) providing a second conveyor  40  including:
           a third belt  42  of interlocking rods  50 , each rod  50  having a tooth  52 , third belt  42  rotatable in a first direction  54 ;   a fourth belt  44  of interlocking rods  50 , each rod having a tooth  52 , fourth belt  44  rotatable in a second direction  56  opposite from first direction  54 ;   third  42  and fourth  44  belts forming a second corridor  74  wherein the teeth  52  of third belt  42  align with the teeth  52  of fourth belt  44 ;   
           (d) passing first  22  and second  24  sheets of deformable material through first corridor  58  wherein first  22  and second  24  sheets of deformable material are corrugated by the teeth  52  of first  34  and second  36  belts;   (e) separating said corrugated first sheet  22  of deformable material from said corrugated second sheet  24  of deformable material;   (f) applying an adhesive to corrugated second sheet  24  of deformable material; and,   (g) simultaneously passing corrugated first sheet  22  of deformable material and corrugated second sheet  24  of deformable material through second corridor  74  so that corrugated first sheet  22  of deformable material is joined by the adhesive to corrugated second sheet  24  of deformable material to form a single layer honeycomb structure.       

     The method further including:
         in steps (b) and (c), teeth  52  having a half-hexagonal shape.       

     The method further including:
         in step (b), first conveyor  32  including a first heated pressure plate  60  which contacts first belt  34  in first corridor  58 , first heated pressure plate  60  heating first belt  34  and urging first belt  34  toward second belt  36 ; and,   first conveyor including a second heated pressure plate  62  which contacts second belt  36  in first corridor  58 , second heated pressure plate  62  heating second belt  36  and urging second belt  36  toward first belt  34 .       

     The method further including:
         in step (b), a first friction reducing material disposed  64  between first heated pressure plate  60  and first belt  34 ; and,   a second friction reducing material  66  disposed between second heated pressure plate  62  and second belt  36 .       

     The method further including:
         in step (c), second conveyor  40  including a third heated pressure plate  80  which contacts third belt  42  in second corridor  74 , third heated pressure plate  80  heating third belt  42  and urging third belt  42  toward fourth belt  44 ; and,   second conveyor  40  including a fourth heated pressure plate  82  which contacts fourth belt  44  in second corridor  74 , fourth heated pressure plate  82  heating fourth belt  44  and urging fourth belt  44  toward third belt  42 .       

     The method further including:
         in step (a), the deformable material being prepreg.       

     The method further including:
         in step (c), third  42  and fourth  44  belts each including a plurality of rods  50  having an indexing tooth  78 , indexing tooth  78  causing third  42  and fourth  44  belts to align rather than mesh.       

     The method further including:
         indexing teeth  78  having a half-hexagonal shape.       

     The method further including:
         in step (a), the deformable material including a five layer sandwich  68  having first  22  and second  24  sheets of deformable material disposed between three layers of release ply  26 ; and,   prior to step (d), providing first  28  and second  30  rollers for feeding first  22  and second  24  sheets of deformable material into first corridor  58 , and third, fourth and fifth rollers  29  for feeding release ply  26  into first corridor  58  to create the five layer sandwich  68 , wherein the five layer sandwich  68  is corrugated by first conveyor  32 .       

     The method further including:
         after step (g), providing a sixth roller  70  which collects the central layer of release ply  26  as the corrugated five layer sandwich  68  exists first corridor  58 ;   in step (e), providing a seventh roller  72  which separates the corrugated first sheet  22  of deformable material from the corrugated second sheet  24  of deformable material; and,   in step (f), providing an adhesive applicator  38  which applies the adhesive to the corrugated second sheet  24  of deformable material.       

     The method further including;
         after step (g), removing a layer of release ply  26  from the corrugated first sheet  22  of deformable material, and removing a layer of release ply  26  from the corrugated second sheet  24  of deformable material: and,   using an adhesive to attach a plurality of the single layer honeycomb structures of step   (g) together.       

     Put another way, a method for producing a honeycomb structure includes:
         (a) providing a first sheet  22  of deformable material stacked upon a second sheet  24  of deformable material;   (b) passing the stacked first  22  and second  24  sheets of deformable material through a first conveyer  32  wherein the first  22  and second  24  sheets of deformable material are corrugated by first conveyor  32 ;   (c) separating first sheet  22  of corrugated deformable material from second sheet  24  of deformable material as they exit first conveyor  32 ;   (d) applying an adhesive to second sheet  24  of deformable material; and,   (e) passing first  22  and second  24  sheets of deformable material through a second conveyer  40  wherein corrugated first  22  and second  24  sheets of deformable material are connected to form a honeycomb structure.       

     The method further including:
         (f) applying a second adhesive to the honeycomb structure of step (e);   (g) repeating steps (a) through (e) to produce a next honeycomb structure;   (h) applying a second adhesive to the next honeycomb structure; and,   (i) placing the next honeycomb structure on top of the honeycomb structure so that the honeycomb structure and the next honeycomb structure are bound together.       

     The method further including:
         repeating steps (g) through (i) a plurality of times until a desired honeycomb structure thickness is achieved.       

     The method further including:
         steps (a) through (e) being performed as a continuous automated production process.       

     Another method for producing a honeycomb structure includes:
         (a) providing a first sheet  22  of deformable material;   (b) providing a first conveyor  32  including:
           a first belt  34  of interlocking rods  50 , each rod having a tooth  52 , first belt  34  rotatable in a first direction  54 ;   a second belt  36  of interlocking rods, each rod  50  having a tooth  52 , second belt  36  rotatable in a second direction  56  opposite from first direction  54 ;   first  34  and second  36  belts forming a first corridor  58  wherein the teeth  52  of first belt  34  mesh with the teeth  52  of second belt  36 ;   
           (c) passing the first sheet  22  of deformable material through first corridor  58  wherein first sheet  22  of deformable material is corrugated by teeth  52  of first  34  and second  36  belts;   (d) providing a second sheet  24  of deformable material;   (e) passing the second sheet  24  of deformable material through first corridor  58  wherein second sheet  24  of deformable material is corrugated by teeth  52  of first  34  and second  36  belts; and,   (f) connecting the first  22  and second  24  corrugated sheets to form a single layer honeycomb structure.       

     It is noted that in this embodiment of the present invention, the first  22  and second  24  sheets of deformable material are sequentially rather than simultaneously passed through the first corridor  58 . This is in contrast to the continuous process embodiment of  FIG. 1  wherein the first  22  and second  24  sheets are simultaneously passed through first corridor. 
     The method further including:
         in step (b), teeth  52  having a half-hexagonal shape.       

     The method further including:
         in step (b), first conveyor  32  including a first heated pressure plate  60  which contacts first belt  34  in first corridor  58 , first heated pressure plate  60  heating first belt  34  and urging first belt  34  toward second belt  36 ; and,   first conveyor  32  including a second heated pressure plate  62  which contacts second belt  36  in first corridor  58 , second heated pressure plate  62  heating second belt  36  and urging second belt  36  toward first belt  34 .       

     The method further including:
         in step (b), a first friction reducing material  64  disposed between first heated pressure plate  60  and first belt  34 ; and,   a second friction reducing material  66  disposed between second heated pressure plate  60  and second belt  36 .       

     The method further including:
         in step (a), the deformable material being prepreg.       

     A method for corrugating a sheet of deformable material includes:
         (a) providing a first sheet  22  of deformable material;   (b) providing a first conveyor  32  including:
           a first belt  34  of interlocking rods  50 , each rod  50  having a tooth  52 , first belt rotatable  34  in a first direction  54 ;   a second belt  36  of interlocking rods  50 , each rod  50  having a tooth  52 , second belt  36  rotatable in a second direction  56  opposite from first direction  54 ;   first  34  and second  36  belts forming a first corridor  58  wherein the teeth  52  of first belt  34  mesh with the teeth  52  of second bel  36   t ; and,   
           (c) passing first sheet  22  of deformable material through first corridor  58  wherein first sheet  22  of deformable material is corrugated by the teeth  52  of the first  34  and second  36  belts;       

     The method further including:
         in step (b), teeth  52  having a half-hexagonal shape.       

     The method further including:
         in step (b), first conveyor  32  including a first heated pressure plate  60  which contacts first belt  34  in first corridor  58 , first heated pressure plate  60  heating first belt  34  and urging first belt  34  toward second belt  36 ; and,   first conveyor  32  including a second heated pressure plate  62  which contacts second belt  36  in first corridor  58 , second heated pressure plate  62  heating second belt  36  and urging second belt  36  toward first belt  34 .       

     The method further including:
         in step (b), a first friction reducing material  64  disposed between first heated pressure plate  60  and first belt  34 ; and,   a second friction reducing material  66  disposed between second heated pressure plate  62  and second belt  36 .       

     The method further including:
         in step (a), said deformable material being prepreg.       

     The preferred embodiments of the invention described herein are exemplary and numerous modifications, variations, and rearrangements can be readily envisioned to achieve an equivalent result, all of which are intended to be embraced within the scope of the appended claims.