Thermoplastic honeycomb with improved cell walls, production process and equipment

Abstract

A thermoplastic folded honeycomb structure is described, which is produced from a material by plastic deformation perpendicular to the plane of the material to form semi-hexagonal cell walls and small connection areas. The cell walls in the L direction of the honeycomb core have a wavy shape with an amplitude of about 10% of the cell wall length. The zero slope of the wavy shape at the cell wall connection points allows optimal shear load transfer between the cell walls. By folding in the transport direction, the wavy cell walls come together to form the honeycomb structure.

Description

[Technical field]

[0001] The present invention relates to cellular structures, such as folded honeycomb structures, an embodiment of a method for producing the same, and equipment for producing the same. In particular, the present invention relates to an improved thermoplastic folded honeycomb structure, a process and equipment for producing the same. [Background technology]

[0002] The folded honeycomb known from WO 97 / 03816 is produced continuously from a single layer, for example a flattened body. The hexagonal cells are built up by folding after the introduction of incisions. The cells are bridged by covering layer connecting surfaces. Folded honeycombs without incisions can be produced economically from one continuous layer of thermoplastic film by rotary vacuum thermoforming. Such folded honeycombs are described in WO 2006 / 053407 and have connecting surfaces covering every second hexagonal cell.

[0003] Honeycomb shapes with deformed cell walls have been proposed to facilitate bending of honeycombs into complex shapes. Wendel, U.S. Pat. No. 3,991,245, shows one embodiment of a method for making flexible honeycombs by corrugation. McCarthy, WO 94 / 17993, shows one embodiment of a method for making flexible honeycombs by expansion. Hull, WO 88 / 06970, shows a "formable honeycomb panel" with folds or twists in the W cell walls. Additionally, honeycombs with folds or twists in all cell walls have been proposed to increase compressive strength. See, for example, "Expanded honeycomb with structured cell walls," WO 2014 / 140453. Conventional expansion processes have been proposed to include folds in the cell walls prior to expansion. The specific shape of very thin cell walls as a function of cell wall width cannot be achieved by conventional expansion processes. Summary of the Invention [Problem to be solved by the invention]

[0004] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT DISCLOSURE The present invention relates to a cellular structure, such as a folded honeycomb structure, an aspect of a method for producing the same, and an apparatus for producing the same. In particular, the present invention relates to an improved thermoplastic honeycomb structure, a process and an apparatus for producing the same.

[0005] It is an object of the present invention to be able to provide a honeycomb, such as a folded honeycomb, having an improved cell wall geometry, as well as methods and apparatus aspects for producing such honeycombs or folded honeycombs.

[0006] It is an object of the present invention to be able to provide honeycombs, such as folded honeycombs, having stronger cell wall geometries, as well as methods and apparatus aspects for producing such honeycombs or folded honeycombs.

[0007] An advantage of the present invention is that it utilizes forming techniques such as vacuum forming or rotary vacuum forming. Thermoforming can also be used. These can be used as a step in the creation of the honeycomb core, allowing for continuous, cost-effective production.

[0008] An advantage of embodiments of the present invention may be good adhesion to the coating layer applied to the honeycomb core. Furthermore, the honeycomb products produced have improved compression resistance, allowing for further reduction in material usage.

[0009] An embodiment of the present invention provides a honeycomb that is not made by spreading or expanding, for example, from a stack of sheets glued together. [Means for solving the problem]

[0010] An embodiment of the present invention provides a honeycomb formed from a plurality of polygonal cells arranged in an array, each polygonal cell having a lateral cell wall extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer plane, the lateral cell walls of each polygonal cell forming a polygonal ring, and for each polygonal cell, at least one lateral cell wall has a wavy shape, the wavy shape being defined by an offset from a line joining two adjacent vertices of a cell, and the slope of the offset of the lateral cell wall having a wavy shape is zero where the lateral cell wall meets the connection point to the other lateral cell wall. Three lateral cell walls meet at one vertex (see, for example, FIG. 6), and the ends of each cell wall meet each other at an interior angle of 120°, or in the case of a rectangular cell shape, four lateral cell walls meet at an interior angle of 90°. Honeycombs having one or more lateral cell walls with a wavy shape have improved mechanical properties. One, some, or all of the lateral cell walls per cell have such a wavy shape. This wavy shape can be included in the honeycomb by the methods disclosed herein. The wavy shape can be applied to at least one, at least two, at least three, or all of the lateral cell walls per cell, where the wavy shape does not have to be the same for all of the lateral cell walls of an individual cell.

[0011] The wavy shape of the side cell walls can have four parts, with two curved parts in the middle of the wavy shape (i.e., in the middle of the side cell walls), the two curved parts being offset from a line joining two adjacent vertices of one polygonal cell, these two curved parts having an inflection point between them, and each central part being connected to a tail or end part having a low or zero slope. One, some, or all of the side cell walls per cell have such a wavy shape. This wavy shape can be included in the honeycomb by the methods disclosed herein. The wavy shape can be applied to at least one, at least two, at least three, or all of the side cell walls per cell, where the wavy shape does not have to be the same for all of the side cell walls of each cell.

[0012] The wavy shape of the lateral cell wall may have two curved portions, one of which is convex and the other of which is concave, such that the center of curvature of one curved portion is on one side of the lateral cell wall and the center of curvature of the other curved portion is on the other side of the lateral cell wall.

[0013] The wavy shape of the lateral cell walls can have three portions, with one curved portion in the middle, offset from a line joining two adjacent vertices of a cell, and this central portion is connected to two tails or ends of the lateral cell walls that have a low or zero slope.

[0014] The two tails or ends have a small or zero slope offset where the lateral cell wall having a wavy shape meets the connection point to the other lateral cell wall at an apex where the lateral cell wall has a zero offset.

[0015] The side cell walls in the L direction can have a wavy shape and the side cell walls in the W direction can have a planar shape, or the side cell walls in the L direction can have a wavy shape and the side cell walls in the W direction can have a wavy shape.

[0016] A number of 3D structures can be formed by plastic deformation of the sheet material, where the 3D structures are half cells that are folded together and adjacent or abutting each other to form lateral cell walls of polygonal cells.

[0017] The wavy shape can be 5% to 20% of the length of the lateral cell wall between adjacent apexes or have an offset with an amplitude in the range of 10% to 15%.

[0018] The polygonal cells may have at least two lateral cell walls forming a double wall having twice the material thickness, both lateral cell walls of the double wall having a wavy shape.

[0019] An embodiment of the present invention provides a method of manufacturing a honeycomb, the method comprising: The method includes forming a plurality of polygonal cells arranged in an array, each polygonal cell having lateral cell walls extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer, the method including forming the lateral cell walls of each polygonal cell as a polygonal ring, and forming, for each polygonal cell, at least one lateral cell wall having a wavy shape, the wavy shape being defined by an offset from a line joining two adjacent vertices of a cell, and a slope of the offset of the lateral cell wall having a wavy shape being zero where the lateral cell wall having a wavy shape meets a connection point to the other lateral cell wall.

[0020] The wavy shape of the side wall can have four parts, i.e., two curved parts in the middle of the wavy shape that are offset from a line joining two adjacent vertices of one polygonal cell, and these two middle parts can have two curved parts with an inflection point between them, and two tails or ends of the wavy shape with low or zero slope, one of the two curved parts is convex and one is concave.

[0021] The wavy shape of the lateral cell walls can have three portions: one curved portion that is in the middle of the wavy shape and is offset from the line joining the two adjacent vertices of a polygonal cell, and two tails or ends that have a low or zero slope and to which this central portion is connected.

[0022] The side cell walls formed in the L direction can have a wavy shape and the side cell walls formed in the W direction can be flat, or the side cell walls formed in the L direction can have a wavy shape and the side cell walls formed in the W direction can have a wavy shape.

[0023] The wavy shape applied to the lateral cell walls may have an offset amplitude that is 5% to 20% of the length of the lateral cell wall between the vertices of the polygonal cell, more precisely in the range of 10% to 15%.

[0024] The lateral cell walls having a wavy shape can have twice the material thickness. The polygonal cells can have at least one double wall, with both lateral cell walls of the at least one double wall having a wavy shape.

[0025] An embodiment of the present invention provides an apparatus for producing honeycombs from a plastically deforming material, the apparatus comprising: means for forming a plurality of polygonal cells arranged in rows, each polygonal cell having lateral cell walls extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer plane; The method comprises means for forming the lateral cell walls of each polygonal cell as a polygonal ring, and means for forming, for each polygonal cell, at least one lateral cell wall belonging to the polygonal cell having a wavy shape, wherein at least one lateral cell wall is connected to or integral with one or two flat lateral cell walls of the polygonal cell to which it belongs or of an adjacent polygonal cell, and the slope of the lateral cell wall is zero where the lateral cell wall meets the connection point to the other lateral cell wall.

[0026] The object of the invention is achieved according to the subject matter of the appended claims and is further developed by the further features of the dependent claims and further aspects detailed below.

[0027] Further aspects of the invention 1. A first embodiment of a honeycomb according to the present invention is formed from a plurality of polygonal cells arranged in an array, e.g., in rows and columns of cells, each polygonal cell having lateral cell walls extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer plane, the lateral cell walls of each polygonal cell being in the form of a polygonal ring, and for each polygonal cell, at least one lateral cell wall has a wavy shape, the wavy shape being defined by an offset from a line joining two adjacent vertices of a polygonal cell, and the gradient of the offset of the cell wall having a wavy shape is zero where the lateral cell wall meets the connection point to the other lateral cell wall.

[0028] Optionally, two or more, or three or more, or four or more, or five or more, or six lateral cell walls of each polygonal cell have a wavy shape.

[0029] At the apex, in the case of a hexagonal core (see FIG. 6), the three lateral side walls meet at an internal angle of 120°, and in the case of a rectangular / square cell, the four lateral cell walls meet at the apex at an internal angle of 90°.

[0030] The wavy shape should preferably be smooth without kinks or steps. 2. An embodiment of a honeycomb according to embodiment 1, wherein the wavy shapes have sinusoidal, square or triangular cross-sections, or parallel alternating ridges and furrows that run parallel to the longitudinal axis of the honeycomb cells. These wavy shapes are generally smooth curves without kinks or steps.

[0031] 3. The honeycomb embodiment of embodiment 1 or 2, wherein for each side cell wall having a periodic wavy shape, the periodic wavy shape has a single period for each such side cell wall. Optionally, the periodic wavy shape has more than one period for each such side cell wall, or is a half period or more than ½ period per side cell wall.

[0032] 4. An embodiment of a honeycomb according to any of the previous embodiments, wherein the offset of the wavy shape is zero where the wavy cell wall meets the connection point to the other side cell wall at the apex of the polygonal cell.

[0033] 5. A honeycomb embodiment according to any of the previous embodiments, wherein the wavy shape of the side cell walls has four portions, namely, two curved portions in the middle of the wavy shape that are offset from a line joining two adjacent vertices of one polygonal cell, these two curved portions in the middle having an inflection point between them, and each curved portion further connected to one of two tails or ends of the wavy shape having a low or zero slope.

[0034] The centers of curvature of the two curved sections are on opposite sides of the lateral cell walls. This arrangement is anticlastic.

[0035] The wavy shape should preferably be a smooth curve without kinks or steps. 6. The honeycomb of embodiment 5, wherein one of the two curved portions is convex and one is concave.

[0036] 7. The honeycomb embodiment of any of embodiments 1-4, wherein the wavy shape of the side cell walls has three portions, namely, one curved portion in the middle of the wavy shape defined by an offset from a line joining two adjacent vertices of one polygonal cell, and two tails or ends having low or zero slopes to which this central portion is connected.

[0037] The curved portion does not have an inflection in the middle of the side cell wall. 8. The honeycomb embodiment of any of embodiments 5-7, wherein the ends have a low or zero offset gradient where the wavy cell walls meet the connection points to the other side cell walls at apexes where the offset is zero.

[0038] 9. The honeycomb embodiment of any of embodiments 5-8, wherein at one vertex or at some vertices or at each vertex, the wavy cell wall offset and the wavy cell wall slope are zero.

[0039] 10. An embodiment of a honeycomb according to any of the previous embodiments, wherein the side cell walls in the L direction have a wavy shape and the side cell walls in the W direction have a planar shape, or the side cell walls in the L direction have a wavy shape and the side cell walls in the W direction have a wavy shape.

[0040] 11. A honeycomb embodiment of any of the previous embodiments, wherein a plurality of 3D structures are formed by plastic deformation of the sheet material, the 3D structures being half cells that are folded together and adjacent or abutting each other to form lateral cell walls of the polygonal cells. As a result of the plastic deformation of the sheet material and folding the half cells together to form the final cells, there is no need to expand or spread out the stack of strips that are secured together, for example by adhesive. This results in better mechanical performance.

[0041] 12. A honeycomb embodiment of any of the preceding embodiments, wherein the plurality of polygonal cells are bounded toward the two open sides of each polygonal cell by a coating layer plane, whereby the cells are each fully or partially bridged at one or the other coating layer plane.

[0042] 13. The honeycomb embodiment of embodiment 11 or 12, wherein the sheet material is a flattened body, a continuous sheet of flattened bodies, multiple pieces of corrugated sheet, a continuous corrugated sheet, and / or a piece or pieces of uncut or nearly uncut flattened bodies, and the multiple 3D structures are formed by at least some plastic deformation of the sheet material.

[0043] 14. The honeycomb embodiment of any of the preceding embodiments, wherein the wavy shape has an offset that is 5%-20% of the length of the cell wall between adjacent vertices or has an amplitude in the range of 10%-15%, the offset being from a line joining two adjacent vertices of one cell.

[0044] 15. The honeycomb embodiment of any of the preceding embodiments, wherein at one vertex or several vertices or each vertex, the offset of the wavy cell walls is 0 and at one vertex, each vertex or all vertices, the slope of the wavy cell walls is 0.

[0045] 16. The honeycomb embodiment of any of the previous embodiments, wherein at least a portion of each side cell wall is fully or partially permanently connected to another side cell wall.

[0046] 17. The honeycomb embodiment of any of embodiments 11-16, wherein the sheets are formed from a thermoplastic polymer, a fiber composite, or a plastically deformable paper, or are metal sheets. Optionally, non-metallic sheet materials can be used.

[0047] 18. The honeycomb embodiment of any of embodiments 11-17, wherein the sheet is composed of a material selected from the group including woven fabrics, spunbond or spunlaid nonwoven fabrics, meltblown nonwoven fabrics, carded nonwoven fabrics, airlaid nonwoven fabrics, wetlaid nonwoven fabrics, knitted fabrics, netting, scrims, a two-dimensional mat of extruded entangled filaments, a reinforcing layer of unidirectional fibers, a layer of rubber material, and a three-dimensional structured mat of entangled filaments.

[0048] 19. The honeycomb embodiment of any of the previous embodiments, wherein at least one edge bounded by a cover layer plane includes a cover layer attached to at least one edge of the honeycomb.

[0049] 20. The honeycomb embodiment of embodiment 19, wherein the cover layer is a two-dimensional (2D) layer and comprises or consists of a material selected from the group including woven fabrics, spunbond or spunlaid nonwoven fabrics, meltblown nonwoven fabrics, carded nonwoven fabrics, airlaid nonwoven fabrics, wetlaid nonwoven fabrics, knitted fabrics, netting, scrims, two-dimensional mats of extruded entangled filaments, reinforcing layers of unidirectional fibers, continuous layers or combinations thereof.

[0050] 21. The honeycomb embodiment of any of embodiments 11-20, wherein the sheet is composed of a thermoplastic polymer selected from the group consisting of a thermoplastic and / or elastomeric polymer, or a thermoplastic polymer selected from the group consisting of polyolefins, particularly polyethylene or polypropylene, polyesters, particularly polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene-1,2-furandicarboxylate, polyamides, particularly polyamide 6 or polyamide 6,6, polycarbonates, polyetherketones, polyetheretherketones, polyetherketoneketone polyethers, polyetheresters, polyphenylene sulfides, polyetherimides, copolymers and mixtures thereof.

[0051] 22. The honeycomb embodiment of any one of embodiments 11-21, further comprising a connection region formed by plastic deformation, the connection region being located at one or the other coating layer plane of the honeycomb.

[0052] 23. An embodiment of a honeycomb according to any of the previous embodiments, wherein the polygonal cells have at least one double material thickness and both side cell walls of the double wall have a wavy shape.

[0053] 24. One aspect of the invention relates to a method of manufacturing a honeycomb, the aspect of the method including forming a plurality of polygonal cells arranged in an array, such as rows and columns, each polygonal cell having lateral cell walls extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer plane; forming the lateral cell walls of each polygonal cell as a polygonal ring; and for each polygonal cell, forming at least one lateral cell wall having a wavy shape, the wavy shape being defined by an offset from a line joining two adjacent vertices of a cell, the slope of the offset of the cell wall having the wavy shape being zero where the lateral cell wall meets a connection point to the other lateral cell wall.

[0054] The wavy shape should preferably be a smooth curve without kinks or steps. 25. An embodiment of the method of embodiment 24, wherein the wavy shape is formed by sinusoidal, square or triangular cross sections, or parallel alternating ridges and furrows that run parallel to the longitudinal axis of the honeycomb cells. Such morphology is generally smooth.

[0055] 26. The method of embodiment 24 or 25, wherein the wavy shape has four parts, i.e., two curved parts in the middle of the wavy shape defined by an offset from a line joining two adjacent vertices of one cell, these two middle parts having an inflection point between them, and two tails or ends of the wavy shape with low or zero slope where each curved part is joined, one of the curved parts is convex and one is concave. The centers of curvature of the curved parts are on different sides of the lateral cell walls. This arrangement is anticlastic.

[0056] 27. An embodiment of the method of any of embodiments 24-25, wherein the wavy shape of the cell walls has three portions, i.e., one central curved portion defined by an offset from a line joining two adjacent vertices of a cell, and two tails or ends of the wavy shape having a low or zero slope at the central portion, and one curved portion has no central inflection. This arrangement is synclastic.

[0057] 28. An embodiment of the method of any of embodiments 26 or 27, wherein the offset of the wavy shape is 0 where a side wavy cell wall meets a connection point to the other side cell wall.

[0058] 29. An embodiment of the method according to any of embodiments 26 to 28, wherein at one vertex or at some vertices or at each vertex, the offset of the wavy cell wall is 0 or the slope of the wavy cell wall is 0.

[0059] 30. An embodiment of the method according to any one of embodiments 24 to 29, wherein the lateral cell walls formed in the L direction have a wavy shape and the lateral cell walls formed in the W direction are flat, or the lateral cell walls formed in the L direction have a wavy shape and the lateral cell walls formed in the W direction have a wavy shape.

[0060] 31. An embodiment of the method of any of embodiments 24-30, comprising forming a plurality of 3D structures by plastic deformation of the sheet material, the 3D structures being folded together and adjacent or abutting one another to form rings of lateral cell walls.

[0061] 32. An embodiment of the method of embodiment 31, wherein a plurality of polygonal cells are bounded toward two open sides of each polygonal cell by a coating layer plane, whereby the cells are each fully or partially cross-linked at one or the other coating layer plane, and a plurality of 3D structures are formed by at least some plastic deformation of the sheet material.

[0062] 33. An embodiment of the method according to any of embodiments 24 to 32, wherein the wavy shape has an offset amplitude that is 5% to 20% of the length of the cell wall between the vertices of the polygonal cells, and more precisely within the range of 10% to 15%.

[0063] The wavy shape is defined by an offset from a line joining two adjacent vertices of a cell.

[0064] 34. An embodiment of the method according to any of embodiments 24-33, wherein the lateral cell walls having a periodic wavy shape have twice the material thickness.

[0065] They can be made from two walls so that twice the thickness is obtained. 35. An embodiment of the method according to any of embodiments 27-34, wherein the offset refers to a plane connecting adjacent vertices of the polygonal cell.

[0066] 36. An embodiment of the method of any of embodiments 31-35, wherein the sheet material is a flat body, a continuous sheet of flat bodies, multiple pieces of corrugated sheet, a continuous corrugated sheet, or a piece or pieces of uncut or nearly uncut flat body, and the multiple 3D structures are formed by at least some plastic deformation of the sheet material.

[0067] 37. An embodiment of the method according to any of embodiments 31-36, wherein the 3D structure is a polygonal, sinusoidal or arc-shaped region.

[0068] 38. An embodiment of the method according to any of embodiments 24-37, wherein at least a portion of each lateral cell wall is permanently connected, fully or partially, to another lateral cell wall.

[0069] 39. An embodiment of the method of any of embodiments 36-38, wherein the sheet material comprises multiple pieces of flat bodies, a continuous sheet of flat bodies, a corrugated sheet, a continuous corrugated sheet, a piece or pieces of uncut or nearly uncut flat bodies, and is formed from a thermoplastic polymer, a fiber composite material, or a plastically deformable paper or metal sheet.

[0070] 40. The method of any one of embodiments 36-39, wherein the sheet material is made from a material selected from the group including woven fabrics, spunbond or spunlaid nonwoven fabrics, meltblown nonwoven fabrics, carded nonwoven fabrics, airlaid nonwoven fabrics, wetlaid nonwoven fabrics, knitted fabrics, netting, scrims, a two-dimensional mat of extruded entangled filaments, a reinforcing layer of unidirectional fibers, a layer of rubber material, and a three-dimensional structured mat of entangled filaments.

[0071] 41. An embodiment of the method of any of embodiments 24-40, wherein at least one edge bounded by the coating layer plane includes a cover layer attached to at least one edge of the honeycomb.

[0072] 42. An embodiment of the method of embodiment 41, wherein the cover layer is a two-dimensional (2D) layer and comprises or consists of a material selected from the group including a woven fabric, a spunbond or spunlaid nonwoven fabric, a meltblown nonwoven fabric, a carded nonwoven fabric, an airlaid nonwoven fabric, a wetlaid nonwoven fabric, a knitted fabric, a net, a scrim, a two-dimensional mat of extruded entangled filaments, a reinforcing layer of unidirectional fibers, a continuous layer or a combination thereof.

[0073] 43. The method of any one of embodiments 24 to 42, wherein the sheet is composed of a thermoplastic polymer selected from the group consisting of a thermoplastic and / or elastomeric polymer, or a thermoplastic polymer selected from the group consisting of polyolefins, particularly polyethylene or polypropylene, polyesters, particularly polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene-1,2-furandicarboxylate, polyamides, particularly polyamide 6 or polyamide 6,6, polyetherketones, polyetheretherketones, polyetherketoneketone polyethers, polyetheresters, copolymers and mixtures thereof.

[0074] 44. An embodiment of the method of any of embodiments 24-43, further comprising forming a connection region by plastic deformation, the connection region being located at one or the other coating layer plane in the honeycomb.

[0075] 45. An embodiment of the method according to any of embodiments 24-44, wherein the polygonal cells have at least one double lateral cell wall, and both cell walls of the at least one double lateral cell wall have a wavy shape.

[0076] 46. ​​An embodiment of the method of any one of embodiments 24-45, wherein the plastic deformation is by thermoforming, vacuum forming, rotary vacuum thermoforming, or a non-cutting rotary process.

[0077] 47. An embodiment of the method of any of embodiments 31-46, wherein the sheet material is cast or extruded as a corrugated sheet, and the corrugated sheet is then molded to modify the corrugations so that they form a 3D structure.

[0078] 48. An embodiment of the method according to embodiment 47, wherein the forming of the corrugated shape is by vacuum forming or thermoforming, or a non-cutting rotary process, or a rotary vacuum thermoforming process.

[0079] 49. The method of any one of embodiments 24-48, wherein one, two or more of the deformed lateral cell walls have a wavy shape, optionally with a periodic or cyclic offset.

[0080] 50. This embodiment relates to an apparatus for manufacturing a honeycomb from a plastically deformable material, the apparatus comprising: means for forming a plurality of polygonal cells arranged in rows, each polygonal cell having lateral cell walls extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer plane; The method comprises means for forming the lateral cell walls of each polygonal cell as a polygonal ring, and means for forming, for each polygonal cell, at least one lateral cell wall belonging to the polygonal cell having a wavy shape, wherein at least one lateral cell wall is connected to or integral with one or two flat lateral cell walls of the polygonal cell to which it belongs, or wherein at least one lateral cell wall is connected to an adjacent polygonal cell, and the slope of the lateral cell wall is zero where the lateral cell wall meets the connection point to the other lateral cell wall.

[0081] 51. Equipment: a) means for plastically deforming a sheet to form therein first 3D structures (1 and 2) and second connection regions (3 and 4) formed between the first 3D structures, forming at least one wall or at least two walls of the first 3D structures having a wavy shape; b) means for folding the first 3D structure towards each other to form cells in the form of rings having cell walls abutting or adjacent to each other such that a cell wall of one cell is adjacent to a cell wall of another cell in the honeycomb structure; c) forming, for each polygonal cell, at least one lateral cell wall having a wavy shape, the slope of the wavy shape being zero where the at least one lateral cell wall meets a connection point to another cell wall of each polygonal cell; An embodiment of an apparatus as described in embodiment 50, comprising:

[0082] 52. An embodiment of the apparatus according to embodiment 50 or 51, comprising an apparatus for processing the flat body as a web, or comprising an apparatus for extruding or casting a planar sheet or web, and then processing the sheet or web with an apparatus for shaping at least one cell wall of any polygonal cells to obtain a wavy shape.

[0083] 53. An embodiment of the apparatus according to embodiment 52, wherein the apparatus for molding is an apparatus for vacuum forming or thermoforming, or a means for a non-cutting rotary process, or a means for a rotary vacuum thermoforming process for forming a first 3D structure in which at least one cell wall has a wavy shape.

[0084] 54. An embodiment of the apparatus of embodiment 52 or 53, wherein the apparatus for casting or extruding the sheet produces a corrugated sheet and further comprises means for shaping the corrugated sheet to modify the corrugations so as to form a first 3D structure having at least one cell wall having a corrugated shape.

[0085] 55. An embodiment of the apparatus according to any of embodiments 52-54, wherein the apparatus for shaping is selected from vacuum forming or thermoforming, or a means for a non-cutting rotary process, or a means for a rotary vacuum thermoforming process for forming a 3D structure in which at least two or all of the cell walls have a wavy shape.

[0086] 56. An embodiment of the equipment described in any of embodiments 52-55, wherein the equipment for molding comprises two half molds having surfaces having a 3D shape that forms a first 3D structure in a sheet including at least one W cell wall or at least two cell walls having a wavy shape.

[0087] 57. An embodiment of the device according to embodiment 56, wherein the mold halves are in the form of matching rotating molds or are stationary molds having upper and lower mold surfaces.

[0088] 58. The apparatus of any one of embodiments 51-57, further comprising an extruder for extruding the sheet, and means for cooling the extruded sheet to a temperature for molding.

[0089] 59. The apparatus of embodiment 58, further comprising means for a further cooling step to solidify the semi-honeycomb structures into their finished shape, and means for folding the semi-honeycomb structures.

[0090] 60. An embodiment of an apparatus configured to produce a honeycomb structure having honeycomb cells from a continuous film or piece of sheet material, where the sheet material can be composed of a thermoplastic polymer or a thermoplastic elastomeric polymer, and the apparatus is further configured for plastic deformation perpendicular to the plane of the material such that three-dimensional structures and connection regions are formed, resulting in the formation of semi-hexagonal cell walls, which are then folded toward each other, resulting in the semi-hexagonal cell walls being at an angle to each other or adjacent to each other in the form of honeycomb cells, and one or more side cell walls per honeycomb cell having a wavy shape.

[0091] The invention and its exemplary embodiments will now be described with reference to the following schematic drawings. [Brief description of the drawings]

[0092] [Figure 1] 1 is a cross-sectional view of a plastic deformable material web according to one embodiment of the present invention; [Diagram 2] 1 is a cross-sectional view of a web of material folded in half to form a honeycomb cell according to one embodiment of the present invention. [Diagram 3] FIG. 1 illustrates a nearly completely folded web of material forming two rows of partially closed honeycomb cells according to one embodiment of the present invention. [Figure 4] 2 is a cross-sectional view of a cross-section of a plastically deformable web of material according to one embodiment of the present invention; [Diagram 5] FIG. 2 illustrates a wavy shape of the cell walls according to one embodiment of the present invention. [Figure 6] FIG. 2 illustrates a hexagonal honeycomb pattern with wavy cell walls according to one embodiment of the present invention. [Figure 7] 11A-11C are diagrams showing variations in cell wall shape according to an embodiment of the present invention. [Figure 8] FIG. 2 is a diagram of a mold surface having a wavy shape according to any of the embodiments of the present invention. [Figure 9] FIG. 2 shows a top view of a hexagonal honeycomb core in which all cell walls have a wavy shape according to one embodiment of the present invention on the left, and for comparison, a top view of a conventional hexagonal honeycomb on the right. [Figure 10] FIG. 2 illustrates planar compressive strength versus density for a conventional hexagonal honeycomb and a hexagonal honeycomb having wavy cell walls, according to one embodiment of the present invention. [Figure 11] FIG. 13 shows the shear buckling failure of hexagonal honeycombs with wavy cell walls loaded in out-of-plane shear in the W direction (WT). [Figure 12] FIG. 1 illustrates the out-of-plane shear performance in the W-direction (WT) of conventional hexagonal honeycomb and hexagonal honeycomb with wavy cell walls, according to one embodiment of the present invention. [Figure 13] FIG. 2 shows a hexagonal honeycomb pattern with wavy cell walls according to one embodiment of the present invention, where the wavy cell walls do not have an inflection in the middle of the cell wall between two vertices. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0093] The above object is achieved according to the subject matter of the appended claims and is further developed by the further features of the dependent claims.

[0094] definition "Wavy shape" refers to the shape of one or more cell walls of a honeycomb core, for example, as seen from above looking down on a fully folded half cell. One or more cell walls of the honeycomb may include one or more periods or cycles of periodic offsets or cyclic offsets or half periods or multiple half periods per lateral cell wall. Alternatively, the wall shape may be non-cyclic or non-periodic offset, but still provide better mechanical properties than cyclic or periodic offsets. The result of the above mentioned offsets is a wavy cell wall shape formed in at least one cell wall of the honeycomb cells, for example cell by cell. The wavy cell wall has an offset amplitude measured with reference to a straight / perpendicular plane between adjacent vertices in the cell, i.e. between the ends of the cell walls of the considered wavy form. The end edges of the cell walls are at the edge connection points to other cell walls. Preferably, when periodic or cyclic is used, there is a half period, multiple half periods, one period or multiple periodic or cyclic offsets along the cell walls between cell wall junctions (i.e., two adjacent vertices) of polygonal, e.g., four-sided or six-sided honeycomb cells.

[0095] The wavy cell wall shape between the apexes of the honeycomb cells according to some embodiments can be described with reference to four sections, with two curved sections in the middle offset from a plane joining two adjacent apexes of a cell after the half cells are folded together to create the honeycomb core. These two middle sections further include two tails or ends with an inflection point between them and with a low or zero slope. One curved section is convex and one concave. This arrangement is anticlastic because the centers of curvature are on opposite sides of the side cell walls. In other embodiments, the wavy shape of the side cell walls has three sections, with one curved section in the middle offset from a line joining two adjacent apexes of a cell, which is connected to two tails or ends that join at the apexes to one or more other side cell walls. The ends preferably have a low or zero slope where the side cell wall with the wavy shape meets the connection point to the other side cell wall at the apex where the offset of the side cell wall is zero. The ends join adjacent cell walls and, by doing so, they create vertices and therefore at this location there is an offset of 0. At one vertex or at some vertices or at each vertex of the honeycomb cell, the offset of the wavy cell walls and the slope of the wavy cell walls are preferably 0.

[0096] "gradient" The slope of a wavy cell wall refers to the slope of the offset of such a wall. The slope is determined relative to a plane joining two adjacent vertices of the polygonal cell. Thus, the slope is the rate of change of the offset of a lateral cell wall with respect to the distance along the plane joining two adjacent vertices of the polygonal cell. It is preferred that the slope at the vertices is zero. The slope and in particular the "zero slope" can be understood by referring in particular to Figures 5 and 6 and the legends to these figures. It is preferred that the offset is also zero at the vertices. For the meaning of small slope or low slope, see the discussion below regarding truncated asymptotic cell wall shapes.

[0097] "L direction or W direction" In the case of honeycomb cells made from sheet material having one or more cell walls with double layers of sheet material, the L direction of the honeycomb is the main direction of the double cell walls in such technical honeycombs, while the single cell walls (if present) have an angle of 30° (alternating positive and negative) with the W direction of the honeycomb and an angle of 60° with the L direction.

[0098] "Vertex at connecting edge" The hexagonal or square tubular cells have several cell walls whereby one cell wall joins with another cell wall at the apex of the hexagonal or rectangular honeycomb cells.

[0099] "Prefix asymptotic cell wall shape" At each end of the cell wall where one cell wall is connected to another cell wall, the shape of the cell wall approaches and preferably reaches a shape of zero slope at the location of zero offset at each apex. The approach to a cell wall without a slope, reaching zero slope at the apex, can be asymptotically truncated since the asymptotic form of the cell wall is truncated. At one or several apexes or each apex of the honeycomb cell, the offset of the wavy cell wall and the slope of the wavy cell wall are preferably zero. The truncated asymptotic end region of the lateral cell wall is preferably limited to the end region of the lateral cell wall up to a distance of L / 10 or L / 7 from the apex, where L is the distance between the two apexes of the polygonal cell. In this specification and claims, the slope at the lateral cell wall connection point / apex is described as a low or small slope. Low or small in this context means a truncated asymptotic cell wall shape that reaches zero slope over a certain distance at the end of the wavy lateral cell wall.

[0100] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS The present invention will be described with reference to particular embodiments and to certain drawings, which are not necessarily to scale and which are schematic and non-limiting. The invention is more generally defined in the appended claims, with each dependent claim representing a further embodiment of the invention.

[0101] An embodiment of the present invention provides a honeycomb structure, such as a folded honeycomb structure, formed from a plurality of tubular / cylindrical polygonal cells arranged in rows, the axes of the tubular / cylindrical polygonal cells being parallel to each other (see FIG. 9). The cells have a polygonal cross section, such as four-sided (rectangular) or six-sided (hexagonal) cells, optionally square. The honeycomb structure, such as a honeycomb core, comprises an array of parallel polygonal cells, each polygonal cell having, for each cell, lateral cell walls adjacent or abutting each other in the form of a polygonal ring. The ring can be formed from a plurality of two half cells, for example by folding together. The ring is formed from polygonal cell walls. The polygonal shape comprises cell walls extending between the vertices of the polygonal shape. The tubular / cylindrical cells can be bounded towards at least one open side of each polygonal cell, and optionally towards two open sides, by a coating layer plane. Each polygonal cell can be fully or partially bridged in one or the other coating layer plane. Honeycombs, such as folded honeycombs, can be formed from uncut or nearly uncut flat bodies, e.g. continuous sheets. Honeycombs, such as folded honeycombs, are preferably made from a plurality of 3D structures formed by plastic deformation of the sheets. They further comprise connection areas, e.g. formed by plastic deformation of the sheets, the connection areas being located in one or the other coating layer plane in the folded honeycomb core. At least one, more preferably two cell walls have a wavy shape, or all cell walls of all cells have a wavy shape. Wavy shape refers to the shape of one or more cell walls of the honeycomb core that are offset compared to a straight line between two vertices of the honeycomb cells. The wavy cell walls between the apexes of a honeycomb cell can be described by reference to four sections, two curved sections in the middle that are offset from a line joining two adjacent apexes of a cell, with an inflection point between them, and two tails or ends that have a low or zero slope. One curved section is convex and one concave. The ends may also have a low or zero slope at the zero offset.At one or several or each vertex of the honeycomb cells, the offset of the wavy cell walls and the slope of the wavy cell walls are preferably zero.

[0102] Each cell can be made from cell walls of a single thickness of material, i.e., a single sheet material thickness or cell can have a combination of a single thickness of sheet material cell walls and one or more cell walls having double the thickness of sheet material or having two walls. The one or more cell walls having a wavy shape can be one or more cell walls having double the sheet material thickness.

[0103] It is preferred that at least the cell walls, which for example become double cell walls in the L direction of the honeycomb core after the folding step, have a wavy shape. Preferably, each cell wall has a wavy structure.

[0104] The wavy shape of one or more cell walls of a honeycomb cell is an offset, i.e. a deviation in a direction perpendicular to the sheet material that constitutes the cell wall, whereby the deviation can be of at least one, or more than one, or all of the cell walls. This deviation can be semi-periodic or periodic, for example with a wave-like or sinusoidal deviation shape that repeats itself. However, non-periodic shapes can be useful and even preferred. Whatever type of shape is selected, it should preferably be smooth and continuous and should not have steps or kinks. It has been found that the offset amplitude of the wavy cell walls, for example with respect to compressive strength, is optimally within the range of 5% to 20%, more precisely within the range of 10 to 15%, of the distance between the apexes or between the connection points to other cell walls, or the length of the cell wall between the cell wall connection points. This amount of offset amplitude helps to prevent or delay buckling of these cell walls under out-of-plane compressive loads. The cell walls are in the form of corrugated six-sided (hexagonal) or corrugated four-sided (rectangular) tubular honeycomb cells held between one or two coating layers. By compensating for the increased length of the corrugated cell walls, the planar compressive strength can be significantly increased even if the corrugated cell walls are made slightly thinner to reach an equal density. In the case of six-sided cells, such as hexagonal cells, the gradient at or near the beginning and end of the corrugation, i.e., at the apex of the hexagonal or square cell, i.e., at the connection points of the cell walls to each other, is preferably small, more precisely zero, so that the cell walls having the corrugated shape join at the cell wall connection points with an internal angle of 120°, as in a regular hexagonal honeycomb. In the case of four-sided, optionally rectangular, e.g. square cells, the cell walls join at the cell wall connection points with an internal angle of 90°, as in a regular square honeycomb. This has been found to be important for the out-of-plane shear performance of the honeycomb core. The cell walls have an offset of zero at the cell wall connection points, i.e., at the apex of the polygon.

[0105] The wavy wall can be formed from four distinct zones. In the center of the cell wall, the wall shape is curved and this curvature defines an offset. In the center, there are two curved sections, one convex and one concave, with an inflection point between them. In the end zones, the offset reduces until the wavy wall shape has a zero slope, preferably reaching a zero offset at the same location.

[0106] One Process Embodiment The production process of folded thermoplastic honeycomb allows the use of a mold that is used to create a 3D structure in a thermoplastic sheet with the desired geometric shape so that the cell walls can be formed by folding. Thermoforming, vacuum forming, rotary vacuum forming or other forming techniques can be used. The input material for forming can be a sheet of material. The process can include a batch process that forms a sheet of material to be processed that is then plastically deformed by a forming technique. Heat and pressure can be applied to the mold to plastically deform the sheet material to form a 3D structure having the shape of a honeycomb half cell, some or all of which are wavy cell walls.

[0107] The input material for extrusion can be a polymer granule, which can be provided by extruding a film directly from an extruder. The 3D structure can then be directly molded into an extrudate. In another embodiment, a sheet, such as a thermoplastic polymer film, is preheated and then processed to obtain a 3D structure that forms honeycomb cells when folded together. The production of the 3D structure can be done by extruding a sheet, then vacuum forming, rotary vacuum forming, thermoforming.

[0108] Thus, the 3D structures according to the embodiments of the present invention can be made from sheet materials or foil or film materials with a relatively thin cross-section or small thickness. In terms of wall thickness or cross-section, a structure can be considered thin-walled if the wall thickness is much smaller than the overall dimension of the structure, such as, for example, height or width or length or radius. The wall thickness compared to the overall dimension of the structure can be one order of magnitude thinner, or more than one order of magnitude thinner. This relates to the thickness of the sheet material and the diameter of the cells. The sheet material can be selected from the group including thermoplastic polymers, thermosetting polymers, woven fabrics, spunbond or spunlaid nonwovens, meltblown nonwovens, carded nonwovens, airlaid nonwovens, wetlaid nonwovens, high loft nonwovens with fibers having vertical orientation, such as V-wrap nonwovens, knitted fabrics, nets, scrims, two-dimensional mats of extruded intertwined filaments, reinforcing layers of unidirectional fibers, and rubber layers.

[0109] Woven, nonwoven, knitted fabrics, netting and scrims may comprise natural fibres, such as hemp, jute or flax fibres, mineral fibres, such as glass, basalt or rock wool fibres, or fibres made from synthetic polymers.

[0110] Preferably, the films, wovens, nonwovens, knits, netting and scrims are composed of synthetic polymers or mineral fibers, more preferably thermoplastic polymers and / or thermoplastic elastomeric polymers.

[0111] In a preferred embodiment, the films, wovens, nonwovens, knits, netting and scrims are comprised of a thermoplastic polymer selected from the group consisting of polyolefins, particularly polyethylene or polypropylene, polyesters, particularly polyethylene terephthalate or recycled polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene-1,2-furandicarboxylate, polyamides, particularly polyamide 6 or polyamide 6,6, polycarbonates, polyetherketones, polyetheretherketones, polyetherketoneketone polyethers, polyetheresters, polyphenylene sulfides, polyetherimides, copolymers and mixtures thereof.

[0112] Detailed finite element analysis shows that for out-of-plane compression resistance, it is preferred that the double cell walls in the L direction or all cell walls are corrugated, with non-periodic or periodic offsets, such as, but not limited to, sinusoidal, square or triangular cross sections, with parallel ridges and furrows extending parallel to the longitudinal axis of the honeycomb cells, but for out-of-plane shear strength, it is preferred that they have very small or zero gradients at the connection points between the cell walls. The corrugated structure can have a periodic structure, with two or more half or full periods in one cell wall, but one half or one period is preferred. Such a corrugated structure can be defined by the amplitude or offset of the waves of the corrugation, the thickness of the sheet, and the number of periods in each corrugated cell wall. This corrugated structure increases the area moment of inertia. The area moment of inertia or second moment of inertia is important in the bending and buckling strength of honeycomb cell walls. The amplitude of the wavy structure of the cell walls, with reference to the straight walls passing between their ends, has been found to be optimal in terms of compressive strength within the range of 5% to 20%, more precisely within the range of 10 to 15% of the length of the cell walls between their connection points to other cell walls (which are the vertices of the polygonal form).

[0113] Surprisingly, the improved compression resistance of the wavy cell walls also results in higher out-of-plane honeycomb shear strength when there is no gradient at the ends of the wavy cell walls (at the connection points to other cell walls), so that the adjacent cell walls at the cell wall connection points can fully support the cell walls. The wavy cell wall pattern according to embodiments of the invention increases the mechanical resistance to initial buckling even though the cell walls are thinner to compensate for the longer length of the wavy cell walls. This significantly increases the honeycomb's compressive strength to weight ratio.

[0114] Edge support for the wavy L cell walls can be provided by adjacent cell walls with smaller offset amplitudes, for example. This support is reduced or substantially reduced when the cell walls in the W direction have a slope at the cell wall connection point. The out-of-plane shear stiffness and strength of the honeycomb core is further reduced when the support of adjacent cell walls is reduced when joining with a slope at the cell wall connection point. Both the wavy L cell walls and the wavy W cell walls should have zero slope at the connection to the adjacent cell wall, and the cell walls may approach the connection point as a truncated asymptote achieving zero offset and zero slope at the connection point.

[0115] One Device Embodiment The present invention further provides an apparatus for producing folded honeycombs made of a plastically deformable material, the apparatus comprising: a) means for plastically deforming a web to form therein first 3D structures (1 and 2) and second connection regions (3 and 4) formed between the first 3D structures (1 and 2), wherein at least one wall or at least two walls of the first 3D structures (1 and 2) have a wavy shape; b) means for folding the first 3D structures (1 and 2) towards each other to form cells in the form of rings having cell walls abutting or adjacent to each other such that a cell wall of one cell is adjacent to a cell wall of another cell in the honeycomb structure; Equipped with.

[0116] To form the wavy shaped cell walls using a vacuum forming mold, it is necessary to form additional small areas at the fold lines 5, 6 between the L cell walls in order to obtain straight fold lines. Straight fold lines are desirable for a stable folding process.

[0117] The equipment for producing folded honeycomb can process the flat body as a web. Alternatively, the web can be processed by equipment for extruding or casting planar sheets or webs, and then processed by equipment for shaping, such as vacuum forming or thermoforming, or by a non-cutting rotary process or rotary vacuum thermoforming process to form the first 3D structure (1 and 2). Preferably, the material is directly rotary vacuum thermoformed after being extruded as a thin film in the extrusion process.

[0118] The sheet may also be cast or extruded as a corrugated sheet, which is molded to modify the corrugations to form a first 3D structure (1 and 2). This molding can be done using equipment for molding, such as vacuum forming or thermoforming, or using a means for a non-cutting rotary process, or using a rotary vacuum thermoforming process, to form a first 3D structure (1 and 2) having at least one cell wall with a corrugated shape.

[0119] Figure 8 shows a mold surface forming a first 3D structure (1 and 2) in a sheet according to one embodiment of the present invention, where all cell walls have a wavy shape. Molds for this purpose form the desired geometry of the cell walls, including the wavy shape, in their surface. The matching molds can include upper and lower molds. The molds can be in the form of matching rotating molds or can be stationary molds with upper and lower mold surfaces.

[0120] Embodiments of the present invention may use thermoforming, which is a process in which a thermoplastic sheet material is heated to a plastic deformation temperature. The thermoplastic material may be a polymeric material.

[0121] The hot sheet material is formed into a specific shape in a mold, such as the mold of FIG. 8, or a rotary vacuum forming mold, to form at least one or all of the cell walls of the honeycomb core with a corrugated shape. The result can be trimmed to cut away excess material. The thermoplastic sheet or web material is preferably heated in an oven to a temperature at which it is malleable so that it can be stretched into or onto the 3D shape in the mold. If extrusion molding is used, the material exits the extrusion die at a high temperature and can be cooled to a temperature at which molding can take place. The cooling step solidifies the semi-honeycomb structures into their finished shape, after which the web is folded. An embodiment of the invention may use vacuum forming or rotary vacuum forming, or may use thermoforming, which uses heat and pressure to allow the porous material to be processed.

[0122] In thermoforming, a thermoplastic sheet or web can be fed from a roll or extruder and transported through an oven for heating to the forming temperature.

[0123] In either case, the heated sheet is then moved into a mating set of mold halves. The mold halves are then closed together, causing the thermoplastic sheet material to deform to the detailed shape within the mold. After a cooling period, the mold tooling opens and the sheet material is extracted from the mold.

[0124] Second Device Embodiment The present invention further provides an apparatus for producing honeycombs, such as folded honeycombs, from flat thermoplastic composite sheet or web materials comprised of plastically deformable thermoplastic sheet materials. Suitable thermoplastic materials may be selected from the polymeric materials described above.

[0125] The equipment is a) means for transporting flat or corrugated thermoplastic composite sheet material from a roll, or extruding a flat or corrugated sheet from an extruder, or removing a flat or corrugated sheet from a stack of sheets; b) means for plastically deforming a flat thermoplastic sheet material, forming or completing therein a first 3D structure (1 and 2) and a second connection area (3 and 4) formed between the first 3D structures (1 and 2), at least one wall or at least two walls of the first 3D structures (1 and 2) having a wavy shape; c) means for folding the first 3D structures (1 and 2) towards each other to form cells in the form of rings having adjacent cell walls such that a cell wall of one cell is adjacent to a cell wall of another cell in the honeycomb structure; may include.

[0126] In an embodiment of the invention, the final honeycomb can have closed ends for the cells. Preferably, only half of the cells are closed at the ends. Figure 1 shows a cross section of a flat web of plastically deformable material, e.g. a thin thermoplastic polymer, with plastic deformation formed in the composite material perpendicular to the material web or sheet. In the regions of the first 3D structures 1 and 2, the material is formed into a polygonal shape, e.g. a trapezoid, a sinusoid, a circular arc, etc., out of the plane of the web. The fold lines (5 and 6) remain in the plane of the web, so that the material is stretched to form second connection regions (3 and 4) that are substantially perpendicular to the material web. The deformation of the thermoplastic composite web material in the regions helps to form the first three-dimensional shape or structure (1 and 2), which will form the walls of the cell halves in the folded final product. The shaping also produces one or more walls of plastically deformed material, which become the cell walls of the final honeycomb core, and have a wavy shape. These cell walls with a wavy shape are, for example, the cell walls of the final product, which have walls with twice the material thickness. For example, in Figure 1, walls 10 abut against each other to form a honeycomb cell wall having a double thickness. As shown in Figure 1, the first 3D structures (1 and 2) are elongated. The corrugated wall waves have troughs and ridges that run along the long sides of the first 3D structures (1 and 2). This improves the compressive strength when a force is applied through the thickness of the final honeycomb core.

[0127] The cells with wavy cell walls are structural and load-bearing elements of the folded final product, whose walls extend transversely to the longitudinal direction of the folded final product. In the folded final product, the cells formed by folding are preferably cylindrical in cross section, the axis of the cylinder extending transversely to the longitudinal direction of the folded final product. The cross-sectional shape of the cells can be formed either flat or wavy and can be selected as desired, for example circular or polygonal, in particular polygonal with even numbers, for example hexagonal.

[0128] FIG. 2 shows a further intermediate state in the production of a folded honeycomb. The constriction of the deformed material web is performed by a folding operation of the material web about the folding lines 5 and 6. By this folding operation, the second connection areas 3 and 4 become flat in the upper and lower planes of the honeycomb core. The folding operation can be performed by a compressive force, which compresses the web in the production direction. Expansion deformations of the cell walls in a direction transverse to the production direction are avoided by the second connection areas 3 and 4. The folding operation can also be performed, for example, by a hot tool, which can also preheat the cell walls that come into contact with each other for joining, for example with an adhesive or by welding, such as ultrasonic welding.

[0129] 1 and 2 show a cross section of a planar sheet or web that is being made of a plastically deformable material. The plastically deformable material may be a thermoplastic polymer material, or a fiber composite material, etc. According to this embodiment, the flat web or sheet has a plastic deformation that forms first 3D structures 1 and 2 formed therein, mainly perpendicular to the material web. In the region of the first 3D structures 1 and 2, the material is deformed, for example, from the plane of the web into a polygon, for example a trapezoid, or a sinusoid, or a circular arc, etc. The deformation forms ridges 8 and valleys 9, whereby each of these is not continuous. For example, the ridges 8 are composed of a linear series of deformation sections, for example of the first 3D structures (1 and 2), for example polygonal, for example trapezoidal, or sinusoidal, or a circular arc section. Preferably, the ridges 8 have an upper surface 10 that may be initially (for example as formed) parallel to the plane of the material web. The two top surfaces 10 abut each other when the first 3D structure (1 and 2) is rotated (also called "folded") to form honeycomb cells. These cell walls, which have at least twice the material thickness, have a wavy shape. The wavy shape is a corrugated shape that is periodically offset from the plane of the surface 10, the corrugated shape having ridges 8 and valleys 9 that extend across the surface 10 in a direction perpendicular to the production direction shown in FIG. 1. Preferably, the wavy shape has only one period, but a half period or multiple half periods or multiple complete periods are included within the scope of the present invention.

[0130] The production direction is preferably as shown in Figure 1. However, a direction perpendicular thereto (parallel to the axes or fold lines 5 and 6) can be used as well.

[0131] The regions containing the first 3D structures 1 and 2 are preferably formed tilted towards each other, i.e. rotated, about an axis or fold line 5 and / or 6, to form additionally U-shaped or V-shaped second connection regions 3 and 4. The second connection regions 3 and 4 separate the ridges of the first 3D structures 1 and 2, e.g. polygonal, e.g. trapezoidal, sinusoidal or curved sections, in one row of the regions containing the first 3D structures 1 and 2. One second connection region 3, 4 is arranged between two regions containing the first 3D structures 1, 2, and the second connection regions 3 are alternated with the second connection regions 4 along the row of the regions containing the first 3D structures 1, 2. The second connection regions 3, 4 form cross valleys, i.e. perpendicular to the valleys 9. Adjacent cross valleys are on opposite sides of the web material. Rotating the regions containing the first 3D structures 1, 2 to the initial position of FIG. 1 is preferably performed at the same time that the deformation is placed in the web of material. The web material is stretched at the transitions between the regions comprising the first 3D structures 1 and 2 to form second connection regions 3 and 4 that are substantially perpendicular to the outer surface of the region comprising the first 3D structures 1 and 2. The angle between the upper surfaces of the second connection regions 3, 4 on the different ridges 8 allows a part of the tool to enter and thus form these ridges 8. The width direction of the material web is preferably parallel to the direction of the axes 5 and 6, while the endless length direction of the material web is continuous along the production direction (shown between the lines 7 in FIG. 1 ).

[0132] The deformation of the web or sheet material serves the purpose of forming three-dimensional shapes or structures 1 and 2, which form the walls of the cell halves in the folded final product. The cells thus formed are the structural and load-bearing elements of the folded final product, whose walls extend transversely to the longitudinal direction of the folded final product. The cell walls having a wavy shape contribute to an increase in the out-of-plane compressive strength. In the final folded product, the cells formed by folding are preferably cylindrical in cross section, the axis of the cylinder extending transversely to the longitudinal direction of the folded final product and in the thickness direction of the planar honeycomb finally produced. The basic cross-sectional shape of the cells can be selected as desired, for example circular or polygonal, in particular polygonal with even numbers, for example hexagonal. This cross section is modified by the formation of at least one or at least two cell walls, for example cell walls with twice the material thickness. The final cell shape is determined by the shape of the deformation areas containing the 3D structures 1, 2 in the original web and how they are folded. As shown in FIG. 3, when the web is folded almost completely, each cell is formed from two half cells. The cells are arranged in rows. Each final cell is formed by the bottom and the sides of two longitudinally adjacent valleys 9 (in the sheet or web material). The half cells are preferably joined together over the contact surface 10 from two longitudinally adjacent ridges 8 (in the web material). The invention therefore provides a folded honeycomb formed from a plurality of cells arranged in rows, with the following characteristics: the cells are adjacent to each other in the form of rings and have lateral cell walls bounded towards the two open sides of the cell by a coating layer plane, whereby the cells are each completely bridged or closed in one or the other coating layer plane. At least one or at least two cell walls have a wavy shape. The cell walls having double material thickness preferably have a wavy shape. The folded honeycomb can be formed from a substantially uncut flat body, i.e. a continuous sheet that is not porous. The sheet can be extruded and can be extruded with a corrugated shape. The plastic deformation of the sheet or corrugated sheet forms a 3D structure.Thus, the folded honeycomb includes a plurality of 3D structures (1 and 2), e.g. polygonal, sinusoidal or curved shaped regions formed by plastic deformation, and a second connection region (3 and 4) in the coating layer plane produced by plastic deformation. At least some of the cell walls are preferably fully or partially permanently connected to each other, e.g. by glue or adhesive or welding. Preferably, the parts of the cell walls close to both coating layer planes are welded together. This can be done by heating the honeycomb core surface in a double belt laminator, preferably while welding the coating sheets onto the honeycomb core.

[0133] The present invention includes a final folded product that is a mixture of cells having different cross-sectional shapes and / or sizes, in particular where at least one cell wall or at least two cell walls have a wavy shape.

[0134] The final honeycomb structure is a planar product, the cells being arranged perpendicular to the plane of the product and across the thickness. The cells on alternate sides of the planar structure are closed by connection regions 3, 4. All cells can be closed by application of one or more covering layers, for example by laminating the planar product of the invention with a covering sheet. The invention includes within its scope the possibility that the first 3D structures 1, 2 in the web forming the cell walls, for example trapezoidal, sinusoidal or circular structures, are not perfectly perpendicular and / or do not come into contact with each other after folding of the deformed material web, thus forming an open structure in at least one direction in the plane (as shown in FIG. 3).

[0135] Returning to the production aspect of the method and to FIG. 4, the production aspect of the method continues by further rotating the regions 1 and 2 so that the surfaces 10 from adjacent ridges 8 are adjacent to each other or preferably in contact. FIG. 4 shows a side view of an intermediate state in the production of a folded honeycomb. The constriction of the plastically deformed material web is performed by a folding movement of the material web about axes or fold lines 5 and 6. The u- or v-shaped connection regions 3 and 4 are widened and flattened in a plane perpendicular to the cell walls. The connection regions 3 and 4 are introduced to avoid substantial deformation of the 3D structure 1 and 2 of the material web, for example polygonal, for example trapezoidal, or sinusoidal, or arc-shaped deformed sections, etc.

[0136] FIG. 3 shows the material almost completely folded to form two rows of hexagonal honeycomb cells. As a result of being folded together, adjacent connection regions 3 (or 4) abut each other. Each honeycomb cell is then closed on at least one side by the connection region 3 or 4. That is, the cell has a closed surface at one end, formed by the connection region 3, 4. The surfaces 10 can be connected to each other, for example, by means of an adhesive or glue, or by welding, such as ultrasonic welding. Preferably, at least the edges of the surfaces 10 that are connected to the connection regions 3 and 4 are connected to each other. However, this connection is not a requirement of the invention.

[0137] The above process relies on folding the deformed web material, by which the 3D structures 1, 2 and surfaces 3, 4 are formed, in order to facilitate the folding and rotating process. Figure 4 shows a side view of the formed material web before the folding action. To facilitate the folding action, the plastically deformed material web has axes or fold lines 5 and 6, preferably located out of plane with a positive value "x", about which the material regions comprising the 3D structures 1 and 2 rotate during folding. The dimension x is selected such that the cross valleys on the upper surface of the material have their lowest apex junction on the axis 6 of the valleys higher than the apex junction on the axis 5 of the cross valleys on the lower surface of the web. Longitudinal forces along the production direction act through the axes 5 and 6, and in so doing exert bending moments around the axes 5, 6. This allows the formed material web to be folded by simple compression in the production direction.

[0138] The production can be carried out discontinuously, for example with a static mould, or it can be carried out continuously in an automated way. Preferably, roller pairs are used to push the material web or sheet together in the production direction. However, rotating tools, vibrating translation tools or guide profiles can be used to assist or ensure the folding of the web or sheet. An independent aspect of the invention is therefore the formation of a folded honeycomb by non-cutting, continuous, static plastic non-rotating or plastic rotational forming of a material web. The plastic deformation can be carried out, for example, by rotary vacuum thermoforming or rotary thermoforming, without a vacuum or static forming process. The sheet or web material can be provided as a stack of films or from a roll or via a film from a die of an extruder. The mould has interengaging profiles, for example on each of the two mould surfaces or on rolls stretching opposite each other.

[0139] The surface of a mould or roller, e.g. a vacuum roller, for thermoforming a material sheet or web has a relatively complex geometric shape in order to allow regions 1 and 2 in the formed material web to be formed as well as to be rotated preferably slightly (e.g. 10 to 30°) towards each other, thereby allowing the formation of the v-shaped connecting regions 3 and 4 and ensuring a vacuum thermoformable airtight shape of the material web which can be folded by further rotation (e.g. about 80° to 60°) of regions 1 and 2 about axes 5 and 6.

[0140] The folding equipment may include a pair of feed rollers, e.g., rubber-coated feed rollers, with grooves in the surface, located upstream of the guide grid to hold the material web in-plane during folding, and a second set of rollers, e.g., rubber-coated push-in rollers with similar grooves, applying a counter pressure to ensure sufficient in-plane compression force to allow folding. The compression force between the lower and upper feed rollers may reduce the tilt and rotation of regions 1 and 2 towards each other by elastic deformation, while in the section between the feed rollers and the counter roller, the material web preferably, but not necessarily, returns to its thermoformed shape without the aid of tools or guides and continues to fold. A gating and / or braking mechanism initially slows or stops the web, which opens with a force generated only by the material web at the fully folded stage. It continues to apply a friction force in its open state as the folded web is formed.

[0141] The folded honeycomb is preferably further processed directly into a lightweight sandwich panel by laminating or directly extruding a covering layer on both sides of the honeycomb core, for example by using laminating rollers or belts. The equipment provided by the present invention can include a deformation and folding unit, as well as a core bonding or welding unit and a lamination unit.

[0142] The web sheet material is provided directly from a suitable forming equipment such as an extruder, or from a roll of web material or a stack of sheet material. Optionally, the web or sheet of material is maintained at a temperature or heated to a forming temperature. The 3D structures 1, 2 are formed in the web or sheet material by any suitable process, for example thermoforming, vacuum forming or hot rolling. Instead of using vacuum forming, a form including opposing shaped pressure plates can be used to apply pressure and heat to a malleable (e.g. high temperature) thermoplastic sheet to form half cells. This allows the use of perforated materials that would not be possible if vacuum forming were applied. The perforations can be produced simultaneously with the application of pressure or can be made in the sheet before the pressure forming step. Creating honeycomb cores from perforated sheets can be excellent for noise attenuation or ensure ventilation of the honeycomb cells in spatial applications.

[0143] The 3D structured web material is folded together to form a honeycomb core. Optionally, lamination of one or more cover layers or other layers is performed, either in-line or offline. Finally, a post-forming operation is performed, such as cutting the honeycomb material to a suitable length or forming it into a suitable shape, for example by pressing or fastening it to another, e.g., a metal part.

[0144] The invention includes folded honeycombs in which the connection regions 3 and 4 are subsequently removed, for example during lamination of the nonwoven covering layer, for example by cutting or melting, so that all cells are open on both sides. Folded honeycombs from thermoplastic materials are very well moldable into complex 3D shapes after preheating the material. The wavy cell walls facilitate the formation of complex 3D shapes without preheating the material.

[0145] Depending on the raw materials used for the folded honeycomb core and the covering layers, the sandwich panels can be used for example for structural components, impact and crash protection, cosmetic panels or packaging applications.

[0146] Figures 5-7 show various versions of wavy cell walls that can be used with any of the embodiments described above.

[0147] FIG. 5 shows a top view of the periodic shape shown as 11 in FIG. 6. Although a preferred single period is shown, two or more periods can be used, for example, for larger honeycomb cores. Preferably, at least the cell walls that result in cell walls with double material thickness in the L direction of the honeycomb core (e.g. after the folding step) have a wavy shape. For example, the wavy shape used for cell walls with double material thickness has an offset with an amplitude in the range of 5% to 20%, more precisely 10 to 15%, of the distance between the vertices of the polygonal cells (e.g. hexagonal or rectangular or square, or 4 or 6 sides) or the length of the cell walls with double material thickness between the vertices. The other cell walls are single cell walls in the W direction of the honeycomb core. The wavy shape of these cell walls can have a smaller amplitude, but can also have the same amplitude as the wavy shape of the double cell walls. The periodic shapes used in any of the embodiments of the present invention have a gradient at the beginning and end of the wavy shape, i.e. at the edges of the cell walls, which is preferably small, more precisely zero, so that in the case of hexagonal cells, the cell walls meet at the cell wall junctions at an angle of 120° (twice 60°), as in a regular hexagonal honeycomb, and in the case of rectangular or square cells, the cell walls meet at the cell wall junctions at an angle of 90°, as in a regular square honeycomb.

[0148] A further example is shown in FIG. 6, which shows a top view of a cell of a six-sided, e.g., honeycomb, core that can be used with any of the embodiments of the invention that provide a honeycomb core. FIG. 6 shows a cell shape with all cell walls 11, 16, 17 having a single period of wavy shape between the hexagonal vertices (at least 18, 12, 14, 19). The invention includes multiple periods of the side cell walls, or multiple half periods per side cell wall. The wavy shape joins without a gradient at the cell wall connection points (at least at the vertices 18, 12, 14, 19), so that the orientation of the cell walls at the connection points is in the general direction of the cell walls. Thus, the cell walls join at an angle of 120° as shown for vertex 12 (90° for rectangular cells). In FIG. 6, all cell walls with wavy shapes are shown. Cells such as those in FIG. 6 can include rectangular, e.g., square, honeycomb cells. The wavy shape used for example in the cell walls of FIG. 6 can have a single thickness, but one or more cell walls with double material thickness are not excluded. The wavy shape has an offset with an amplitude in the range of 5% to 20%, more precisely 10 to 15%, of the distance between the vertices of the polygonal cells (e.g. hexagonal or rectangular or square, or 4 or 6 sides) such as at least 18, 12, 14, 19 or the length of the cell walls with double material thickness between the vertices. The other cell walls are single cell walls in the W direction of the honeycomb core. The wavy shape of these cell walls can have a smaller amplitude or the same amplitude as the wavy shape of the double cell walls. The periodic shapes used in any of the embodiments of the present invention have a slope at the beginning and end of the wavy shape, i.e. on the sides of the cell walls, which is preferably small, more precisely 0, so that in the case of hexagonal cells, the cell walls join at the cell wall connection points at an angle of 120°, as in regular hexagonal honeycombs. In the case of rectangular or square cells, the cell walls meet at the cell wall junctions at 90° angles, as in a regular square honeycomb.

[0149] FIG. 7 shows a single period of a wavy shape 50, which shows a schematic representation of different options for the shape of the wavy cell walls. The cell wall shape 50 includes four cell wall sections, all integrally constructed as cell walls from sheet material. The parts 54 and 56 are convex / concave curved regions (convex in opposite directions) of the cell walls that are joined together, e.g. integral with each other, and pass through an inflection point 51 between them at a zero offset point. Alternatively, the parts 54 and 56 can form a single convex / concave curved region without inflection. These curved regions 54, 56 can be identical to corresponding sinusoidal or pseudo-sinusoidal shapes. The curved region 56 includes a position 55 with a maximum offset in the cell wall in one direction (solid line 57 in FIG. 7). The curved region 54 includes a position 53 with a maximum offset in the opposite direction (solid line 57 in FIG. 7). At the edge away from the region 56 is a tail region 52. This tail region 52 joins the adjacent cell wall at a junction or apex of the honeycomb (not shown) and has a slope less than the slope of the corresponding sinusoidal shape at this location, or has a truncated asymptote shape that reaches a zero slope in the wavy cell wall. The slope does not have to increase monotonically until it reaches a zero slope.

[0150] At the edge away from part 54 is a tail region 58. This tail region 58 joins the adjacent cell wall at a connection point or apex of the honeycomb core (not shown) and has a slope less than the slope of the corresponding sinusoidal shape at that point, or has a truncated asymptote shape that reaches a zero slope at the wavy cell walls, or the wavy cell walls of tail region 52 are at a zero slope, or the wavy cell walls do not increase monotonically until they reach a zero slope.

[0151] The small or preferably zero slope of the wavy shape at the cell wall junction (solid line 57 in FIG. 7) is shown in contrast to a wavy shape having a significant slope or even a maximum slope at the cell wall junction (dashed line 59 in FIG. 7). The two wavy shapes associated with the two materials may be slightly different.

[0152] FIG. 8 shows a mold surface for vacuum forming a web with wavy cell walls. Other forming aspects of the method can be used, such as using pressure and heat in a mold with top and bottom platens. As a result of the formation of the wavy L cell walls, small additional skin connection areas 30 and 40 are formed at the fold lines. This allows for easy and reliable folding action with straight fold lines. The small additional skin connection areas 30 and 40 can improve the core-skin connection at the L cell walls.

[0153] FIG. 9 shows, on the left side of the page, a top view of a folded honeycomb with wavy cell walls, and, on the right side, a top view of a conventional hexagonal honeycomb with straight cell walls.

[0154] Figure 10 shows the planar compressive strength as a function of honeycomb cell wall density. Compression test results for honeycombs with wavy cell walls show a compressive strength of 60-70 kg / m 3 This is an improvement of approximately 70%. 3 Within this density range, the compressive strength is about 49% higher, at 110-120kg / m 3 Within the density range, the compressive strength is about 23% better than that of a conventional hexagonal honeycomb with straight cell walls. At equal compressive strength, the wavy cell wall geometry is about 20 kg / m at lower densities. 3 This allows for a reduction in density. This allows for significant savings in raw material costs and resources. With regard to the performance of sandwich core materials, the out-of-plane shear stiffness and strength are important in addition to the significant out-of-plane compression stiffness and strength.

[0155] Figure 11 shows the shear buckling failure mode of a W-direction out-of-plane shear loaded honeycomb core with wavy cell walls. The out-of-plane shear strength in the W-direction is typically significantly lower than in the L-direction in technical honeycomb cores due to the double L cell walls.

[0156] Figure 12 shows a comparison of stress-strain curves of W-direction out-of-plane shear loaded honeycomb cores of the same density with and without wavy cell walls obtained from FEM analysis. The shear stiffness of the honeycomb with wavy cell walls is approximately equal to that of a conventional honeycomb with straight cell walls, but in shear strength, the honeycomb with wavy cell walls performs significantly better. Without being limited by theory, it is believed that the higher shear strength is caused by the later onset of shear buckling of the wavy W cell walls. This effect was also seen in the L direction, but the increase in the already much better shear strength in this direction was smaller. This also results in more balanced shear properties in the two main directions of the honeycomb core. If desired, further balance up to equal shear properties in both directions can be achieved by reducing the length of the L cell walls compared to the length of the W cell walls.

[0157] FIG. 13 shows a further embodiment of the invention that can be made by any of the equipment of the invention, can be made from any of the disclosed materials, and can be used in any of the product embodiments of the invention. The cell wall of FIG. 13, unlike the wavy cell wall of FIG. 6, does not have an inflection point in the middle of the cell wall. Instead, there is one main curve shape for the side cell walls. The concave or convex side of the side cell wall points to the center of the cell depending on which side cell wall is involved. FIG. 13 shows a hexagonal cell in which all side cell walls have a wavy shape. The wavy shape of the side cell walls shown in FIG. 13 is maintained if the cell is rotated 120°, but not if the cell is rotated 60°. For rectangular, e.g., square, honeycomb cell types, this angle is 180°. A wavy cell wall like that of FIG. 13 can be translated to the opposite side of the honeycomb cell while maintaining the same shape. The wavy shape of Figure 13 can be a periodic shape, whereby there is one half period per side cell wall, i.e., a center of curvature on one side of the side cell wall, in Figure 13. Also included within the scope of the invention are periods of 1.5, 2.5, etc. per side cell wall.

[0158] In comparison, FIG. 6 shows a wavy curved shape applied to the lateral cell walls, the wavy shape having a concave and convex shape for each lateral cell wall, thus showing the centers of curvature of different sides of the lateral cell wall by inflection points in the wavy shape. The wavy shape of one lateral cell wall is maintained if the lateral cell wall is rotated by 60°. For rectangular, e.g., square, honeycomb cell types, this angle is 900°. The wavy cell wall can be translated to the other side of the honeycomb cell while maintaining the same shape. The wavy shape of FIG. 6 can be a periodic shape, whereby in FIG. 16 there is one period per lateral cell wall. Also included within the scope of the invention are periods of 2, 3, etc. per lateral cell wall.

[0159] With respect to Figures 6 and 13, all the side cell walls are shown with a wavy shape. At least one, at least two, at least three or all the side cell walls of the cell having a wavy shape are also included in the present invention. The wavy shape can be different for different side cell walls of the cell. This can be achieved by using the molding technique disclosed in the embodiments of the present invention.

Claims

1. 1. A honeycomb formed from a plurality of polygonal cells arranged in an array, each polygonal cell having lateral cell walls extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer plane, the lateral cell walls of each polygonal cell forming a polygonal ring, and for each polygonal cell, at least one lateral cell wall has a wavy shape, the wavy shape being defined by an offset from a line joining two adjacent vertices of a polygonal cell, and a slope of the offset of the side cell wall having the wavy shape is zero where the side cell wall meets a connection point to another side cell wall.

2. 10. The honeycomb of claim 1 comprising two or more, or three or more, or four or more, or five or more, or six lateral cell walls of each polygonal cell having a wavy shape.

3. 10. The honeycomb of claim 1, wherein at an apex, in the case of a hexagonal core, three lateral sidewalls meet at an interior angle of 120°, or in the case of a rectangular / square cell, four lateral cell walls meet at an interior angle of 90°.

4. 2. A honeycomb according to any preceding claim, wherein said wavy shape is a smooth curve without kinks or steps.

5. 2. The honeycomb of claim 1, wherein said wavy shape has a sinusoidal, square or triangular cross section, or said wavy shape has parallel alternating ridges and furrows extending parallel to the longitudinal axes of said polygonal honeycomb cells.

6. for each side cell wall having a periodic undulation, said periodic undulation has a single period for each such side cell wall; or 3. The honeycomb of claim 1 or 2, wherein the periodic wavy shape has two or more periods for each side cell wall or is a half period or more than 1 / 2 period per side cell wall.

7. 2. A honeycomb according to any preceding claim, wherein the offset of the wavy shape is zero where the wavy cell walls meet their connection points to other side cell walls at the vertices of the polygonal cells.

8. 10. A honeycomb according to any of the preceding claims, wherein the wavy shape of the side cell walls has four sections, with two curved sections in the middle of the wavy shape, the two curved sections being offset from a line joining two adjacent vertices of a polygonal cell, the two curved sections having an inflection point therebetween, and each of the central curved sections being connected to a tail or end having a low or zero slope.

9. 9. The honeycomb of claim 8, wherein the centers of curvature of said two curved portions are on opposite sides of said side cell walls.

10. 10. The honeycomb of claim 8 or 9, wherein the wavy shape is anticlastic and free of twists or steps.

11. A honeycomb according to any one of claims 8 to 10, wherein one of the two curved portions in the center of the wavy shape is convex and the other of the two curved portions is concave, such that the center of curvature of one curved portion is on one side of the side cell wall and the center of curvature of the other curved portion is on the other side of the side cell wall.

12. 11. A honeycomb according to any of claims 1 to 10, wherein the wavy shape of the side cell walls has three portions, namely one curved portion in the middle that is offset from a line joining two adjacent vertices of one polygonal cell, and two tails or ends of the side cells with low or zero slope to which the central portion is connected.

13. 13. The honeycomb of claim 8, wherein the two tails or ends have a low or zero slope where the side cell wall having a wavy shape meets a connection point to the other side cell wall at the apex of the polygonal cell where the offset of the side cell wall is zero.

14. the lateral cell walls in the L direction have a wavy shape and the lateral cell walls in the W direction have a planar shape; or 10. A honeycomb according to any preceding claim, wherein the lateral cell walls in the L direction have a wavy shape and the lateral cell walls in the W direction have a wavy shape.

15. 13. A honeycomb as claimed in any preceding claim, comprising a plurality of 3D structures formed by plastic deformation of a sheet material, said 3D structures being half cells, folded together and adjacent or abutting each other to form said lateral cell walls of said polygonal cells.

16. 10. A honeycomb according to any preceding claim, wherein a plurality of polygonal cells are bounded towards two open sides of each polygonal cell by coating layer planes, whereby each of said polygonal cells is fully or partially bridged at one of said coating layer planes.

17. 17. The honeycomb of claim 15, wherein the sheet material is a flat body, a continuous sheet of flat bodies, multiple pieces of corrugated sheet, a continuous corrugated sheet, and / or a piece or pieces of uncut or nearly uncut flat bodies, and the multiple 3D structures are formed by plastic deformation of the sheet material.

18. 10. A honeycomb according to any preceding claim, wherein said wavy shape has an offset that is 5% to 20% of the length of the lateral cell wall between adjacent vertices or has an amplitude in the range of 10% to 15%.

19. 10. A honeycomb according to any preceding claim, wherein at one or several vertices or each vertex, the offset of the wavy cell walls is zero and at the one or each vertex, the slope of the wavy cell walls is zero.

20. 10. A honeycomb according to any preceding claim, wherein at least a portion of each side cell wall is permanently connected, either fully or partially, to another side cell wall.

21. A honeycomb according to any of claims 15 to 20, wherein the sheet material is formed from a thermoplastic polymer, a fibre composite material or a plastically deformable paper, or is a metallic or non-metallic sheet material.

22. 22. The honeycomb of any of claims 15 to 21, wherein the sheet is composed of a material selected from the group consisting of woven fabrics, spunbond or spunlaid nonwoven fabrics, meltblown nonwoven fabrics, carded nonwoven fabrics, airlaid nonwoven fabrics, wetlaid nonwoven fabrics, knitted fabrics, netting, scrims, two-dimensional mats of extruded entangled filaments, reinforcing layers of unidirectional fibers, layers of rubber material, and three-dimensional structured mats of entangled filaments.

23. 2. A honeycomb according to any preceding claim, wherein at least one edge bounded by said coating layer plane includes a cover layer attached to at least one edge.

24. 24. The honeycomb of claim 23, wherein the cover layer is a two-dimensional (2D) layer and comprises or consists of a material selected from the group comprising woven fabrics, spunbond or spunlaid nonwoven fabrics, meltblown nonwoven fabrics, carded nonwoven fabrics, airlaid nonwoven fabrics, wetlaid nonwoven fabrics, knitted fabrics, netting, scrims, two-dimensional mats of extruded entangled filaments, reinforcing layers of unidirectional fibers, continuous layers or combinations thereof.

25. 25. A honeycomb according to any of claims 15 to 24, wherein the sheet is composed of a thermoplastic polymer selected from the group consisting of thermoplastic and / or thermoplastic elastomeric polymers or polyolefins, in particular polyethylene or polypropylene, polyesters, in particular polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene-1,2-furandicarboxylate, polyamides, in particular polyamide 6 or polyamide 6,6, polycarbonates, polyetherketones, polyetheretherketones, polyetherketoneketonepolyethers, polyetheresters, polyphenylene sulfides, polyetherimides, copolymers and mixtures thereof.

26. A honeycomb according to any of claims 15 to 25, further comprising a connection area formed by said plastic deformation, said connection area being located in one of said coating layer planes.

27. 10. A honeycomb according to any preceding claim, wherein said polygonal cells have at least two lateral cell walls forming a double wall having twice the material thickness, both lateral cell walls of said double wall having a wavy shape.

28. 1. A method of manufacturing a honeycomb, the method comprising:

11. A method for forming a plurality of polygonal cells arranged in an array, each polygonal cell having lateral cell walls extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer plane, the method including forming the lateral cell walls of each polygonal cell as a polygonal ring, and forming, for each polygonal cell, at least one lateral cell wall having a wavy shape, the wavy shape being defined by an offset from a line joining two adjacent vertices of a polygonal cell, the slope of the offset of the lateral cell wall having a wavy shape being zero where the lateral cell wall having a wavy shape meets a connection point to another lateral cell wall.

29. 30. The method of claim 28, wherein the wavy shape is a smooth curve without kinks or steps.

30. 29. The method of claim 28, wherein the wavy shape is formed by sinusoidal, square or triangular cross sections or parallel alternating ridges and furrows extending parallel to the longitudinal axis of the honeycomb cells.

31. 31. The method of claim 30, wherein the centers of curvature of the curved portions are on different sides of the lateral cell walls.

32. 31. The method of any of claims 28 to 30, wherein the wavy shape of the cell walls has three parts, namely one central curved part defined by an offset from a line joining two adjacent vertices of a cell, and two tails or ends of the wavy shape having a low or zero slope in this central part, one of the curved parts having no central inflection.

33. 33. The method of claim 32, wherein the offset of the undulating shape is zero where the lateral undulating cell wall meets a connection point to another lateral cell wall of the honeycomb.

34. A method according to any of claims 28 to 33, wherein at one or several or each vertex, the offset of the wavy cell walls is zero or the slope of the wavy cell walls is zero.

35. The method according to any one of claims 28 to 35, wherein the side cell walls formed in the L direction have a wavy shape and the side cell walls formed in the W direction are flat, or the side cell walls formed in the L direction have a wavy shape and the side cell walls formed in the W direction have a wavy shape.

36. 36. A method according to any of claims 28 to 35, comprising forming a plurality of 3D structures by plastic deformation of a sheet material, said 3D structures being folded together and adjacent or abutting each other to form rings of said lateral cell walls.

37. 37. The method of claim 36, wherein the plurality of polygonal cells are bounded towards two open sides of each polygonal cell by a coating layer plane, whereby the cells are each fully or partially cross-linked at one or the other of the coating layer planes, and the plurality of 3D structures are formed by plastic deformation of the sheet material.

38. the wavy shape of the lateral cell walls has four parts, namely two curved parts formed in the middle of the wavy shape with an offset from a line joining two adjacent vertices of one polygonal cell, the two curved parts having an inflection point between them, and two tails or ends of the wavy shape with a low or zero slope, one of the two curved parts being formed convexly and one being formed concavely, or 29. The method of claim 28, wherein the wavy shape of the lateral cell walls has three portions: one curved portion formed in the center of the wavy shape and offset from a line joining two adjacent vertices of one polygonal cell, and two tails or ends having a low or zero slope to which the central portion is connected.

39. The side cell walls formed in the L direction are made to have a wavy shape and the side cell walls formed in the W direction are made flat, or 39. The method of claim 37 or 38, wherein the lateral cell walls formed in the L direction are made to have a wavy shape and the lateral cell walls formed in the W direction are made to have a wavy shape.

40. A method according to any of claims 28 to 392, wherein the wavy shape is between 5% and 20% of the length of the lateral cell walls between the vertices of the polygonal cells, or has an offset amplitude in the range of 10% to 15%.

41. A method according to any of claims 28 to 40, wherein the lateral cell walls having a wavy shape are formed with double material thickness.

42. 42. The method of any of claims 36 to 41, wherein the sheet material is a flat, a continuous sheet of flat, multiple pieces of corrugated sheet, a continuous corrugated sheet, an uncut or nearly uncut piece or pieces of flat, and the multiple 3D structures are formed by plastic deformation of the sheet material.

43. 43. The method of claim 42, wherein the 3D structure is a polygonal, sinusoidal or arc-shaped region.

44. A method according to any of claims 28 to 43, wherein at least a portion of each lateral cell wall is fully or partially permanently connected to another lateral cell wall.

45. 45. The method of any of claims 42 to 44, wherein the sheet material comprises pieces of flats, a continuous sheet of flats, a corrugated sheet, a continuous corrugated sheet, an uncut or nearly uncut piece or pieces of flats and is formed from a thermoplastic polymer, a fiber composite material, or a plastically deformable paper or metal sheet.

46. 46. ​​The method of any of claims 36 to 45, wherein the sheet material is made from a material selected from the group comprising woven fabrics, spunbond or spunlaid nonwoven fabrics, meltblown nonwoven fabrics, carded nonwoven fabrics, airlaid nonwoven fabrics, wetlaid nonwoven fabrics, knitted fabrics, netting, scrims, a two-dimensional mat of extruded entangled filaments, a reinforcing layer of unidirectional fibers, a layer of rubber material, and a three-dimensional structured mat of entangled filaments.

47. The method of any of claims 36 to 46, wherein at least one edge bounded by a coating layer plane comprises a cover layer attached to said at least one edge of the honeycomb.

48. 48. The method of claim 47, wherein the cover layer is a two-dimensional (2D) layer and comprises or consists of a material selected from the group comprising woven fabrics, spunbond or spunlaid nonwoven fabrics, meltblown nonwoven fabrics, carded nonwoven fabrics, airlaid nonwoven fabrics, wetlaid nonwoven fabrics, knitted fabrics, netting, scrims, two-dimensional mats of extruded entangled filaments, reinforcing layers of unidirectional fibers, continuous layers or combinations thereof.

49. 49. The method according to any of claims 36 to 48, wherein the sheet is composed of a thermoplastic polymer selected from the group consisting of a thermoplastic and / or elastomeric polymer, or a thermoplastic polymer selected from the group consisting of polyolefins, in particular polyethylene or polypropylene, polyesters, in particular polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene-1,2-furandicarboxylate, polyamides, in particular polyamide 6 or polyamide 6,6, polyetherketones, polyetheretherketones, polyetherketoneketonepolyethers, polyetheresters, copolymers and mixtures thereof.

50. The method according to any of claims 36 to 49, further comprising forming connection areas by said plastic deformation, said connection areas being located in one or the other of said coating layer planes in said honeycomb.

51. 51. The method of any of claims 28 to 50, wherein the polygonal cells have at least one double lateral cell wall, and both cell walls of the at least one double lateral cell wall have a wavy shape.

52. The method of any of claims 36 to 51, wherein the plastic deformation is by thermoforming, vacuum forming, rotary vacuum thermoforming or a non-cutting rotary process.

53. 45. The method of any of claims 36 to 44, wherein the sheet material is cast or extruded as a corrugated sheet, and then the corrugated sheet is shaped to modify the corrugations to form the 3D structure.

54. 54. The method of claim 53, wherein the forming of the corrugations is by vacuum forming or thermoforming, or a non-cutting rotary process, or a rotary vacuum thermoforming process.

55. A method according to any of claims 28 to 54, wherein one, two or more lateral cell walls have a wavy shape, optionally with a periodic or cyclic offset.

56. 1. An apparatus for producing honeycombs from a plastically deformable material, comprising: means for forming a plurality of polygonal cells arranged in rows, each polygonal cell having lateral cell walls extending between vertices of each polygonal cell, each polygonal cell being bounded on two sides by a coating layer plane; The device comprises means for forming the lateral cell walls of each polygonal cell as a polygonal ring, and means for forming, for each polygonal cell, at least one lateral cell wall belonging to the polygonal cell having a wavy shape, wherein the at least one lateral cell wall is connected to or integral with one or two flat lateral cell walls of the polygonal cell to which it belongs, or the at least one lateral cell wall is connected to an adjacent polygonal cell, and the slope of the lateral cell wall is zero where the lateral cell wall meets the connection point to the other lateral cell wall.

57. 57. The apparatus of claim 56, comprising an apparatus for forming, for each polygonal cell, at least one lateral cell wall having a wavy shape, the slope of the wavy shape being zero where the at least one lateral cell wall meets a connection point to another cell wall of each polygonal cell.

58. 58. The apparatus of claim 56 or 57, comprising an apparatus configured to process a flat body as a web, or comprising an apparatus for extruding or casting a planar sheet or web, followed by processing said sheet or web with an apparatus for shaping at least one cell wall of any polygonal cells to obtain a wavy shape.

59. 59. The apparatus of claim 58, wherein the apparatus for shaping is an apparatus for vacuum forming or thermoforming, or a means for a non-cutting rotary process, or a means for a rotary vacuum thermoforming process to form the first 3D structure, in which at least one cell wall has a wavy shape.

60. 60. The apparatus of claim 58 or 59, wherein the apparatus for casting or extruding the sheet produces a corrugated sheet and further comprises means for shaping the corrugated sheet to modify the corrugations to form the first 3D structure having at least one cell wall with a corrugated shape.

61. 61. The apparatus according to any of claims 58 to 60, wherein the apparatus for shaping is selected from vacuum forming or thermoforming, or a means for a non-cutting rotary process, or a means for a rotary vacuum thermoforming process for forming the 3D structure, in which at least two cell walls or all cell walls have a wavy shape.

62. 62. The apparatus of any of claims 58 to 61, wherein the apparatus for molding comprises two half molds having surfaces with a 3D shape forming the first 3D structure in a sheet comprising at least one W cell wall or at least two cell walls having a wavy shape.

63. 63. The device of claim 62, wherein the mold halves are in the form of mating rotating molds or are stationary molds having upper and lower mold surfaces.

64. 64. The apparatus of any of claims 57 to 63, further comprising an extruder for extruding the sheet, and means for cooling the extruded sheet to a temperature for forming.

65. 65. The apparatus of claim 64, further comprising means for a further cooling step to solidify said half-honeycomb structures into their final shape, and means for folding said half-honeycomb structures.

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