A honeycomb member and a honeycomb

Abstract: A member for a honeycomb core or panel that can be bent with various radii of curvature, can contour a compound curvature and can support a load perpendicular to the defined curvature. The honeycomb member, preferably, has cells having an equilateral triangular cross section. The cells are defined by rectangular bottom, top and side faces. The connecting angle between each bottom face and each side face is typically about 60 degrees. The adjoining sides of the bottom faces contact each other. The adjoining sides of the top faces also contact each other. Although the cells contain a small orifice between adjoining sides, the cells have the same strength as that of completely enclosed cells. Furthermore, the relative position of the adjoining cells can be easily altered.

Description: BACKGROUND OF THE INVENTION This invention relates to a honeycomb member and a honeycomb panel. By using a single honeycomb member or by the arrangement of multiple honeycomb members, the honeycomb panel can be formed. Typically, a honeycomb core is composed of a plurality of dense close ended cells and can be used as core for a flat honeycomb panel. The cells typically have a hexagonal or square cross section. When a honeycomb core or panel is used for various structural applications, curved configurations are often required. A curved honeycomb core or panel is generally manufactured by merely bending plate material, but other known methods for manufacturing a curved honeycomb core or panel also exist and are now explained. As shown in Figure 9, flexible honeycomb members composed of cells defined by curved faces are manufactured. The honeycomb members are then adhered, soldered or welded to one another along a desired curvature to form a honeycomb core. A second known method, shown in Figure 10, depicts a plurality of strip materials 101 which are bonded together by applying adhesive onto hatched portions 102 and then formed into a lamination 103. After a crosshatched portion 104 is removed from the lamination 103, the lamination 103 is extended to form a curved honeycomb core 105. The curved honeycomb core 105 is then sandwiched and bonded between face plates 106 and 107 to produce a curved honeycomb panel. Document JP-58-25531-A discloses another method as shown in Figures 11A through 11D. A strip material 111 is folded along folding lines 112 and 113. As shown in Figure 11A, the folding lines 112 are perpendicular to a center line CL, and the folding lines 113 are slanted in relation to the center line CL. The strip material 111 is then folded along the folding lines 112 and 113 to form a corrugated sheet 116. As shown in Figures 11B and 11C, the corrugated sheet 116 has inclined ridges 114 and grooves 115. As shown in Figure 11D, when the corrugated sheet 116 is overlapped with one another corrugated sheet, the ridges 114 of one corrugated sheet 116 are attached onto the grooves 115 of another corrugated sheet 116 through spot welding, thereby defining hexagonal cells 118 thus creating a curved honeycomb core 117. The aforementioned related-art methods for manufacturing curved honeycomb cores or panels have many problems. In the first-explained related-art method, when a curved honeycomb core is manufactured by bending the plate material, the honeycomb core resists against the force required to bend it, thus permitting only large radii of curvature. Small radii of curvature cannot be obtained, using this method. In the second related-art method shown in Figure 9, the materials of the honeycomb cores have such a special configuration that positioning of the materials for forming cells is troublesome when the honeycomb cores are laminated onto one another. The production time is thereby significantly increased, moreover, the desired honeycomb core becomes more difficult to form as its height increases, due to the required curvature. The third related-art method, shown in Figure 10, involves multiple process steps, which increase production time. Furthermore, the honeycomb core 105 is not adequately supported perpendicular to its defined curvature, therefore the honeycomb panel produced has insufficient strength. In the last related-art method shown in Figures 11A through 11D, it is difficult to form the corrugated sheet 116 by folding the strip material 111 along the folding lines 112 and 113. It is also troublesome to form the cells 118 having hexagonal cross section by positioning and attaching the corrugated sheets 116. Additionally, the corrugated sheets 116 are bent with only a limited radius of curvature. This method, as defined, is insufficient to provide honeycomb cores or panels having varying radii of curvature. SUMMARY OF THE INVENTION A honeycomb member comprising the features of the pre-characterizing clause of claim 1 is known from document US-A-3068565, and in particular from figure 5 thereof. Adjoining side edges of two adjoining faces of this known honeycomb member define a comparatively wide opening. This opening is only closed when a plurality of the honeycomb members are arranged in the manner shown in figure 5 of this document. To provide sufficient strength to a honeycomb core made from a plurality of the known honeycomb members, the members are brazed to each other at contacting portions thereof. However, the inherent strength of a single one of the known honeycomb members is comparatively small. It is an object of the invention to provide a honeycomb member comprising the features of the pre-characterizing clause of claim 1 which has an improved inherent stability. It is desired that the honeycomb member can be contoured into complicated configurations such as compound curvatures, composed of multiple continuous curves. Further, it is an object of the invention to provide a honeycomb panel according to the pre-characterizing clause of claim 9 whose strength is improved by an increased stability of the at least one honeycomb member. These objects are achieved by the honeycomb member according to claim 1 and by the honeycomb panel according to claim 9. The honeycomb member according to the invention is characterized by the feature that the honeycomb member is bent such that the adjoining side edges of two adjoining first faces contact each other at least at a portion thereof. This results in that the side edges of each interconnecting wall surrounding a cell contact each other at least at one point so that the individual cell has an increased resistance against external forces. Thereby, the inherent stability of the individual honeycomb member is increased. The related-art honeycomb members must be laminated and bonded onto one another to form cells. Therefore, to form a honeycomb panel, multiple honeycomb members need to be specifically arranged. The honeycomb member, according to the present invention, however, utilizes individual cells each of which can independently resist external forces. Consequently, multiple honeycomb members need not to be specifically ordered to form a honeycomb core. The structure and function of a embodiments of the invention are now explained. BRIEF DESCRIPTION OF THE DRAWINGS: Figures 1A and 1B are explanatory views of an intermediate product used for producing a honeycomb member according to this invention. Figures 2A through 2C are explanatory views of a final honeycomb member bent for use. Figures 3A and 3B are explanatory views showing inner and outer radii formed when the honeycomb member is bent. Figures 4A through 4C are explanatory views explaining the flexibility of the honeycomb member according to this invention. Figures 5A through 5D are cross-sectional views illustrating the configuration of the cells of further embodiments of the intermediate honeycomb member. Figures 6A through 6C are explanatory views of a first embodiment of a honeycomb panel. Figures 7A and 7B are explanatory views of a second embodiment of a honeycomb panel. Figure 8 is an explanatory view of a further application of the honeycomb member. Figure 9 is a perspective view of a related-art honeycomb member. Figure 10 is an explanatory view showing the formation of the curvature from a related-art honeycomb member. Figures 11A through 11D are explanatory views illustrating a related-art honeycomb member. Figures 1A and 1B show a honeycomb member of an intermediate stage of the production of the final honeycomb member according to the invention. As shown in Figures 1A and 1B, each cell 4 in a honeycomb member 5 is defined by a series of bottom first faces 1, a series of top faces 2, and interconnecting walls 3. Each of the first and second faces 1,2 and of the walls 3 has a rectangular surface and creates an equilateral triangular cross section for each cell 4. A connecting angle  between each first face 1 and each wall 3 is about 60 degrees. In the honeycomb member 5, each cell 4 is rowed such that the first faces 1 are arranged with corners or side edges 1a and 1b between adjacent cells 4 and having a slight clearance and such that the second faces 2 are arranged with corners or side edges 2a and 2b between adjacent cells 4 with a slight clearance. As shown in Figures 2A and 2B, when the honeycomb member 5 is bent to form a radius of curvature, adjoining side edges 1a and 1b contact each other to form support points 6. The honeycomb member 5 can then be bent flexibly in any direction on the support points 6. The support points 6, therefore, assure the stable flexibility of the honeycomb member 5. When the honeycomb member 5 is bent to a radius of curvature as shown in Figure 2C, adjoining side edges 1a and 1b contact each other to form support lines 7. These support lines 7 also assure the stable flexibility of the honeycomb member 5. The connecting angle  is so acute that either support points 6 or support lines 7 offer adequate and stable flexibility to the honeycomb member 5, even when the first faces 1, the second faces 2 and the walls 3 are thin. When the final products are manufactured, specified points P can be soldered. In the honeycomb member 5 shown in figures 1A and 1B, the interval between adjoining side edges 1a and 1b is narrow and the cell 4 has a slight clearance therein. The honeycomb member 5 can be bent in such a direction that the adjoining side edges 1a and 1b will contact each other. Therefore, the bend direction of the entire honeycomb member 5 is settled. The honeycomb member 5 can bend flexibly along support points 6 and lines 7. When the honeycomb member 5 is bent, the first faces 1 define an inner bend radius. As aforementioned, the honeycomb member 5 can be bent as shown in Figures 2A and 2B. Before the honeycomb member 5 is soldered to a face plate to form a honeycomb panel, the honeycomb member 5 can also be bent as follows. As shown in Figures 3A and 3B, upon bending the honeycomb member 5, an outer radius R1 and an inner radius R2 are formed. When L denotes the length of the first face 1, the bend limitation of the honeycomb member 5 can be determined by means of the following equations. R1=(d1/2)+(L 2 /8d1) R2=-(d2/2)+(L 2 /8d2) In the above equations d1 and d2 denote clearances as shown in Figures 3A and 3B. Limit clearances are substituted for d1 and d2. The limit clearances are requirements for soldering the honeycomb member 5 onto a face plate. As shown in the above equations, by adjusting the length L of the first face 1, small radii of curvature can be permitted. To further decrease the radius of curvature, both ends of each first face 1 of the honeycomb member 5 can be trimmed according to the curvature of a face plate, thereby minimizing the clearances d1 and d2. As shown in Figures 4A and 4B, a honeycomb member can also be twisted about the axis defining its length. The hatched portion of the strip material for a honeycomb member can be cut out. The strip material is then folded along folding lines a through i to form a honeycomb member as shown in Figure 4C. This honeycomb member can contact a face plate with only slight clearance therebetween. Therefore, as long as the folding lines a through i are perpendicular to the length of the honeycomb member 5, the first faces 1, the second faces 2 and the walls 3 are not limited to a strictly rectangular shape. By cutting the part of the strip material to obtain an appropriate curve, a honeycomb member can be soldered to a face plate easily, thereby following the configuration of a honeycomb panel. As aforementioned, the honeycomb member according to this invention can be bent or twisted to various radii of curvature. In a honeycomb core composed of the honeycomb member, the load-bearing force acts perpendicularly to the curved surface of the honeycomb core. When a honeycomb panel is manufactured, a panel is first pressed to a desired curvature; the honeycomb member of this invention is then arranged onto a panel, and a face plate is fit onto the honeycomb member. Through simple manufacturing steps, the honeycomb member can be bent or twisted as desired. Consequently, a honeycomb panel having a complicated set of curvatures can be easily manufactured. Since the sizes of the cells composing the honeycomb member are easily adjusted, the material thickness, the cell heights and the curvature of the honeycomb core as well as other parameters can each be easily adjusted. Therefore, a honeycomb core or panel having desired strength can be easily manufactured. A honeycomb member can also be manufactured by folding a strip member along a series of parallel folding lines. The cells of the intermediate honeycomb member can alternately have an isosceles triangular or other shaped cross section. For example, per Figure 5A, cells 23 can have a circular cross section composing a honeycomb member 24. As shown in Figure 5B, cells 25 can have a square cross section and form a honeycomb member 26. As shown in Figure 5C, in a honeycomb member 27, curved first faces and second faces can also define cells. In a honeycomb member 29, per Figure 5D, the first faces, walls and second faces of cells can include folded reinforcement ribs 28 for strengthening the honeycomb member 29. In the honeycomb members, 24, 26, 27 and 29 the connecting angle  between each interconnecting wall and each first face of each cell is acute. Therefore, the honeycomb members, 24, 26, 27 and 29 offer the same effects as those of the honeycomb member 5 composed of the cells 4. A first embodiment of a honeycomb panel will now be explained with reference to Figures 6A through 6C. In this embodiment, cells 31 having an equilateral triangular cross section compose a honeycomb member 32, in the same way as the honeycomb member 5 composed of the cells 4 explained above and shown in Figures 1A and 1B. The honeycomb member 32 can be used in honeycomb panels having a variety of curvatures. In this embodiment, aluminum strip material is folded to form the honeycomb member 32, such that three 11mm long sides define the cells 31. The aluminum strip material has a thickness of 0.2mm and a width of 13mm. As shown in Figure 6B, the honeycomb member 32 is first bent in the same way as explained with reference to Figure 2A such that an inner radius Ri is 50mm. As shown in Figure 6C, face plates 33 and 34 are then soldered to the inner and outer peripheries of the honeycomb member 32, respectively, thereby forming a honeycomb panel. The honeycomb member 32 can be bent flexibly and then soldered in place to follow the curvature of the face plates 33 and 34. The load-bearing force of the honeycomb member 32 acts perpendicularly to the radius of curvature of the face plates 33 and 34, thereby providing adequate strength. A second embodiment of a honeycomb panel will now be explained with reference to Figures 7A and 7B. In this embodiment, the honeycomb member 32 of the above first embodiment is formed in the same way as explained with reference to Figure 2B. The honeycomb member 32 is then assembled and soldered between face plates 35 and 36. The face plates 35 and 36 are pressed in advance to have a compound curvature. As shown in Figure 7B, the compound curvature consists of a convex curvature followed by a concave curvature. The convex curvature has an inner radius R1 of 70mm and the concave curvature has an inner radius R2 of 45mm. In this embodiment, the honeycomb member 32 follows the compound curvature of the honeycomb panel. The honeycomb member 32 is securely soldered between the face plates 35 and 36. The load-bearing force of the honeycomb member 32 acts perpendicularly to the compound radii of curvature, thereby offering adequate strength, for example a compressive strength of about 0.7kgf/mm 2 to the honeycomb panel. A further application of the honeycomb members will now be explained with reference to Figure 8. In this embodiment the honeycomb member 32 is bent as shown in Figure 2C to form a spacer between a honeycomb core 41 and an aluminum block 42 in a honeycomb panel. The honeycomb core 41 is composed of known cells having a hexagonal cross section. A screw thread (not shown) is provided in the aluminum block 42. A bore 43 is made in the honeycomb core 41 to receive the aluminum block 42. The honeycomb member 32 is bent and wound around the aluminum block 42. The aluminum block 42 is then inserted into the bore 43. The honeycomb member 32 secures the aluminum block 42 in the honeycomb panel and strengthens the portion between the aluminum block 42 and the honeycomb core 41. The honeycomb member 32 can thus be used as an individual reinforcement due to its rigidity. At the same time, the honeycomb member 32 can contour any curve of the panel. Since the honeycomb member 32 fills the portion between the aluminum block 42 and the honeycomb core 41, this portion has the same strength as the other portions of the honeycomb panel and is more resistant to breakage. The honeycomb member 32 could also be wound around the aluminum block 42 in several layers without having to bond the layers to one another. This invention has been described above with reference to preferred embodiments as shown in the drawings. Modifications and alterations may become apparent to one skilled in the art upon reading and understanding the specification. It should also be noted that Figures 5A through 5D show the cross sections of various configurations the honeycomb cells have. The cross section of the cells, however, is not restricted to these configurations. The connecting angle between the cell walls and first faces, however, is preferably acute. Since the cross section of the cells is not limited to that of an equilateral triangle, the cells can have an orifice therein. Furthermore, the material of the honeycomb member is not limited to the specified material.

Claims: A honeycomb member for a honeycomb core or panel, said honeycomb member (5, 24, 26, 27, 29, 32) being elongate and comprising a plurality of rectangular first faces (1) which are sequentially arranged and extend in the axial direction of said member (5, 24, 26, 27, 29, 32) and further comprising interconnecting walls (2, 3) each extending substantially perpendicular to the length of said member (5, 24, 26, 27, 29, 32) and being connected to adjoining side edges (1a, 1b) of two adjoining ones of said first faces (1), said interconnecting walls (1, 2) defining a plurality of axially spaced cells (4, 23, 25, 31), characterized in that said member (5, 24, 26, 27, 29, 32) is bent such that said adjoining side edges (1a, 1b) of said two adjoining ones of said first faces (1) contact each other at least at a portion (6, 7) thereof. A honeycomb member according to claim 1 in which the connecting angle formed between the interconnecting walls (2,3) and the axially spaced first faces (1) is less than 90°. A honeycomb member according to claim 2 in which the connecting angle is about 60°. A honeycomb member according to claim 1 wherein said adjoining side edges (1a,1b) contact each other along a line (7) to form a continuous load bearing surface perpendicular to a radius of curvature which said member (5,24,26,27,29,32) is bent to. A honeycomb member according to claim 1 wherein the cells (4) have a substantially triangular cross-section. A honeycomb member according to claim 1 wherein the cells (25) have a substantially rectangular cross-section. A honeycomb member according to claim 1 in which the cells (23) have a substantially circular cross-section. A honeycomb member according to claim 1 in which said member (5,24,26,27,29,32) is made from aluminum. A honeycomb panel comprising two face plates (33, 34, 35, 36) and at least one honeycomb member (5, 24, 26, 27, 29, 32) interposed between said two face plates and attached thereto, characterized in that said at least one honeycomb member (5, 24, 26, 27, 29, 32) is arranged as defined by one of claims 1 to 8.

Inventors: ITO YASUNAGA, UOZUMI YOSHIMASA, ITO, YASUNAGA, UOZUMI, YOSHIMASA, Ito, Yasunaga, c/o Technical Research Laboratories, Uozumi, Yoshimasa, c/o Technical Research Lab.
Applicants: SUMITOMO LIGHT METAL IND, SUMITOMO LIGHT METAL INDUSTRIES LIMITED
Application year: 1991
Main classification: B29D24
IPC codes: B21D47, E04C2, B32B3, B31D3, B29D24