Thermoplastic honeycomb structures having multi-layer cell walls, their manufacturing processes and apparatuses

Abstract

Embodiments of the present invention provide a honeycomb core formed from a plurality of polygonal cells arranged in an array, each polygonal cell having side cell walls, the side cell walls of each polygonal cell forming a polygonal ring, the side cell walls being composed of a sheet material, the sheet material being a symmetric three-layer or five-layer thermoplastic coextruded sheet material having an inner center or core layer and an outer layer. The symmetric three-layer or five-layer thermoplastic coextruded sheet material provides improved mechanical properties compared to a simple sheet material.

Description

Technical Field

[0001] The present invention relates to a cellular structure such as a folded honeycomb structure, an aspect of a method for manufacturing the same, and a manufacturing apparatus therefor. In particular, the present invention relates to an improved thermoplastic folded honeycomb structure, a process and an apparatus for manufacturing the same.

Background Art

[0002] The folded honeycomb known from WO 97 / 03816 is produced continuously from a single layer, for example a flat body. The hexagonal cells are constructed by folding after the introduction of cutouts. The cells are cross-linked by coating layer connection surfaces. A folded honeycomb without cutouts can be produced economically from one continuous layer of a thermoplastic film by rotary vacuum thermoforming. Such a folded honeycomb described in WO 2006 / 053407 has connection surfaces covering every other hexagonal cell. Further honeycombs are described in WO 2019 / 158743, the entire disclosure of which is incorporated herein by reference, and WO 2006 / 053407, the entire disclosure of which is incorporated herein by reference.

[0003] A three-layer honeycomb cell wall is known from US 2022 / 0001643 A1, the three layers being a support layer having two adhesive layers, with one adhesive layer provided on one side of the support layer.

[0004] Chinese Patent Application Publication No. 110154490 (CHN Energy Invest Group CO LTD., NAT INST Clean&Low Carbon Energy, filed Aug. 23, 2019) relates to material forming, in particular to a thermoplastic core material having a multi-layer composite structure and an apparatus including the core material.

[0005] Chinese Patent Application Publication No. 110228220 (CHN Energy Invest Group CO LTD., NAT INST Clean&Low Carbon Energy, filed on September 13, 2019) relates to material forming, in particular, a method and an apparatus for manufacturing a thermoplastic composite core material.

[0006] European Patent Application Publication No. 3297817 (Ecocore NV [Belgium], filed on March 28, 2018) relates to a hierarchical sandwich core (20), and describes those having a honeycomb form, i.e., those having a repetitive and periodic lattice material. The sandwich core (20) can be composed of a mesoscopic honeycomb structure having a sandwich cell wall with a mesoscopic cell core. The longitudinal axis of the cells of the mesoscopic honeycomb cells may be perpendicular to the longitudinal axis of the cells of the mesoscopic honeycomb structure.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention relates to a sheet material capable of manufacturing an improved thermoplastic honeycomb core, as well as a process and an apparatus for manufacturing the same.

[0008] An object of the present invention is to be able to provide a honeycomb such as a folded honeycomb having an improved cell wall, and a method and an apparatus aspect for manufacturing such a honeycomb or a folded honeycomb.

[0009] An object of the present invention is to be able to provide a honeycomb such as a folded honeycomb having a stronger cell wall shape, and a method and an apparatus for manufacturing such a honeycomb or a folded honeycomb.

Means for Solving the Problems

[0010] Embodiments of the present invention provide a honeycomb core formed from a plurality of polygonal cells arranged in an array, each polygonal cell having side cell walls, each polygonal cell being bounded on both sides by a coating layer plane, the side cell walls of each polygonal cell forming a polygonal ring, the side cell walls being composed of a sheet material, the sheet material being a symmetric three-layer or five-layer thermoplastic coextruded sheet material having a center (or core) layer or inner layer and outer layers. The symmetric three-layer or five-layer thermoplastic coextruded sheet material provides improved mechanical properties compared to a simple sheet material. One aspect of the present invention is the use of a three-layer or five-layer sandwich cell wall where the center (or core) layer or inner layer is made of a material having a lower density than the material of the outer layer. Thus, it is preferred that the center (or core) layer or inner layer has a significantly lower density than the outer layer. The center (or core) layer or inner layer preferably has a lower density than the outer layer, for example, the center (or core) layer or inner layer can have a density of 30% to 90%, preferably 50 to 70% of the density of the outer layer. Thereby, a good strength / weight ratio is obtained.

[0011] Preferably, the yield strength of the outer layer is greater than the yield strength of the center (or core) layer or inner layer. Thereby, the mechanical properties are improved.

[0012] The center (or core) layer or inner layer can be made by physical foaming or chemical foaming, or by being composed of low-density components. The low-density components can include hollow glass particles.

[0013] The polymer density of the outer layer is preferably in the range of 0.9 to 1.5 or 0.9 to 2 kg / dm 3 . Increasing the polymer density improves the mechanical properties. For example, when the outer layer has a density of 1.6 kg / dm 3 , the center (or core) layer or inner layer can have a density of 1.1 kg / dm 3 . Also, the outer layer can have a density of 1 kg / dm 3 , and the center (or core) layer or inner layer can have a density of 0.9 kg / dm3 It has the following density.

[0014] The thickness of the three - layer or five - layer co - extruded cell wall is preferably 1 mm or less and at least 0.1 mm. The central (or core) layer or inner layer of the co - extruded cell wall preferably has a thickness of 1 / 3 or more, or preferably 1 / 2 or more, most preferably 67% - 90% of the total cell wall thickness. The central (or core) layer can preferably be in the range of 50 - 67% of the total thickness of the symmetric three - layer (ABA) co - extruded sheet material. Each outer layer 6 can preferably be in the range of 25% - 16.5% of the total thickness of the symmetric three - layer (ABA) co - extruded sheet material.

[0015] The outer layer is preferably flat and smooth without out - of - plane non - uniformity compared to the ideal plane of the cell wall, and the non - uniformity of the outer layer is smaller than the thickness of the outer layer. Micro - CT or laser profile sensor scanning is used to measure the out - of - plane non - uniformity compared to the ideal plane of the cell wall.

[0016] The symmetric three - layer or five - layer thermoplastic co - extruded sheet material can be selected from thermoplastic polymers consisting of thermoplastic polymers and / or thermoplastic elastomer polymers, or polyolefins, especially polyethylene or polypropylene, polyesters, especially polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene - 1,2 - furandicarboxylate, polyamides, especially polyamide 6 or polyamide 6,6, polycarbonates, polyether ketones, polyether ether ketones, polyether ether ketones, polyether ketone ketone polyethers, polyether esters, polyphenylene sulfides, polyetherimides, copolymers, and mixtures thereof with or without fillers, reinforcing agents and / or air or gas inclusions.

[0017] The inner core of the symmetric three - layer or five - layer thermoplastic co - extruded sheet material can be a foam such as a mechanical foam or a chemical foam.

[0018] The central (or core) layer or inner layer and the outer layer are preferably composed of the same thermoplastic polymer.

[0019] Embodiments of the present invention provide a method for manufacturing a honeycomb core folded from a sheet material, the method comprising a) direct coextrusion of a symmetric multilayer sheet material and transfer for rotational vacuum thermoforming followed by folding, or b) reheating of a coextruded or laminated multilayer sheet material, and transfer for rotational vacuum forming or sequential compression forming, followed by folding.

[0020] The sheet material is wound onto a drum after direct coextrusion or reheating and can then be unwound from the drum for transfer for folding.

[0021] This method can further include forming a plurality of polygonal cells arranged in an array, each polygonal cell having side cell walls, each polygonal cell being bounded on both sides by a coating layer plane, the side cell walls of each polygonal cell forming a polygonal ring, the side cell walls being composed of the sheet material, and the sheet material being a symmetric three-layer or five-layer thermoplastic coextruded sheet material.

[0022] Symmetric three-layer or five-layer thermoplastic coextruded sheet materials provide improved mechanical properties compared to simple sheet materials.

[0023] This method also includes the use of three-layer or five-layer sandwich cell walls when the central (or core) layer or inner layer is made of a material with a lower density than the material of the outer layer. Thus, it is preferred that the central (or core) layer or inner layer has a significantly lower density than the outer layer. The central (or core) layer or inner layer preferably has a lower density than the outer layer. For example, the central (or core) layer or inner layer can have a density of 30% to 90%, preferably 50 to 70% of the density of the outer layer. Thereby, a good strength / weight ratio is obtained.

[0024] In this method, it is preferable that the yield strength of the outer layer is preferably greater than the yield strength of the central (or core) layer or the inner layer. Thereby, the mechanical properties are improved.

[0025] In this method, the central (or core) layer can be produced by physical foaming or chemical foaming, or by being composed of a low-density component. The low-density component can include hollow glass particles.

[0026] In this method, the polymer density of the outer layer is preferably in the range of 0.9 to 1.5 or 0.9 to 2 kg / dm 3 . Increasing the polymer density improves the mechanical properties. For example, when the outer layer has a density of 1.6 kg / dm 3 , the central (or core) layer or the inner layer can have a density of 1.1 kg / dm 3 . Also, the outer layer can have a density of 1 kg / dm 3 , and the inner core can have a density of 0.9 kg / dm 3 or less.

[0027] In this method, the thickness of the three-layer or five-layer coextruded cell wall is preferably 1 mm or less and at least 0.1 mm. The central (or core) layer or the inner layer of the coextruded cell wall preferably has a thickness of 1 / 3 or more, or preferably 1 / 2 or more, and most preferably 67% to 90% of the total cell wall thickness. The central (or core) layer 8 can preferably be in the range of 50 to 67% of the total thickness of the symmetric three-layer (ABA) coextruded sheet material. Each outer layer 6 can preferably be in the range of 25% to 16.5% of the total thickness of the symmetric three-layer (ABA) coextruded sheet material.

[0028] In this method, the outer layer is preferably flat and smooth without out-of-plane non-uniformity compared to the ideal plane of the cell wall, and the non-uniformity of the outer layer is smaller than the thickness of the outer layer. Use micro-CT or a laser profile sensor scan to measure the out-of-plane non-uniformity compared to the ideal plane of the cell wall.

[0029] For this method, the symmetric three-layer or five-layer thermoplastic coextruded sheet material can be selected from thermoplastic polymers consisting of a thermoplastic polymer and / or a thermoplastic elastomer polymer, or a polyolefin, in particular polyethylene or polypropylene, a polyester, in particular polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene-1,2-furandicarboxylate, a polyamide, in particular polyamide 6 or polyamide 6,6, a polycarbonate, a polyether ketone, a polyether ether ketone, a polyether ether ketone, a polyether ketone ketone polyether, a polyether ester, a polyphenylene sulfide, a polyether imide, a copolymer, and mixtures thereof with or without fillers, reinforcing agents and / or air or gas inclusions, selected from the group consisting of.

[0030] In this method, the inner core of the symmetric three-layer or five-layer thermoplastic coextruded sheet material may be a foam such as a mechanical foam or a chemical foam.

[0031] In this method, the central (or core) layer or the inner layer and the outer layer are preferably composed of the same thermoplastic polymer.

[0032] Embodiments of the present invention provide a method for manufacturing a honeycomb core folded from a sheet material, the method comprising a) direct coextrusion of a symmetric multilayer sheet material and transfer for rotational vacuum thermoforming followed by folding, or b) reheating of the coextruded or laminated multilayer sheet material, and transfer for rotational vacuum forming or sequential compression forming, followed by folding, The method further includes forming a plurality of polygonal cells arranged in an array, each polygonal cell having side cell walls, each polygonal cell being bounded on both sides by a coating layer plane, the side cell walls of each polygonal cell forming a polygonal ring, the side cell walls being composed of a sheet material, the sheet material being a symmetric three-layer or five-layer thermoplastic coextruded sheet material having a central (or core) layer or inner layer and outer layers, the central (or core) layer or inner layer having a density that is 30% to 90%, preferably 50 to 70%, of the density of the outer layer.

[0033] Embodiments of the present invention provide an apparatus for manufacturing a honeycomb core folded from a sheet material, the apparatus comprising a) means for direct coextrusion of a symmetric multilayer sheet material and transfer for rotational vacuum thermoforming and subsequent folding, or b) means for reheating a coextruded or laminated multilayer sheet material and transfer for rotational vacuum forming or sequential compression forming and subsequent folding.

[0034] The apparatus can include means for forming a plurality of polygonal cells arranged in an array, each polygonal cell having side cell walls, each polygonal cell being bounded on both sides by a coating layer plane, the side cell walls of each polygonal cell forming a polygonal ring, the side cell walls being composed of a sheet material, the sheet material being a symmetric three-layer or five-layer thermoplastic coextruded sheet material.

[0035] Further embodiments are disclosed in the detailed description of the invention and the dependent claims. Definitions When evaluating the density of porous plastics and rubbers in this application, the following tests are used. Porous plastics and rubbers - Determination of apparent density (ISO 845:2006), DIN EN ISO 845:2009 - 10 When evaluating the density of porous plastics and rubbers in this application, the following tests are used.

[0036] DIN EN ISO1183-1:2019-09 Plastics - Methods for determining the density of non-cellular plastics - Part 1: Immersion method, pycnometer method and titration method (ISO 1183-1:2019, modified version 2019-05).

[0037] When evaluating the yield strength of porous plastics and rubbers in this application, the following tests are used.

[0038] DIN EN ISO527-1:2019-12 Plastics - Determination of tensile properties such as yield strength - Part 1: General principles (ISO 527-1:2019).

[0039] Figures 1 to 9 show embodiments of the present invention.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Best Mode for Carrying Out the Invention

[0041] Detailed Description of Exemplary Embodiments FIG. 1 shows an overview of the method and apparatus according to an embodiment of the present invention. FIG. 2 shows a single cell from the honeycomb core according to FIG. 1.

[0042] The honeycomb core according to an embodiment of the present invention can include a sheet material such as a symmetric multilayer such as a symmetric three-layer (layer ABA) sheet material or a symmetric five-layer sheet (layer CABAC) material. Any of these materials can be manufactured by co-extruding a first thermoplastic material with a second thermoplastic material. The first thermoplastic material forms the core B, and the second thermoplastic material forms the outer layers A and C.

[0043] These honeycomb cores are all made from a sheet material and can be made using a symmetric three-layer or five-layer sheet according to an embodiment of the present invention.

[0044] FIGS. 2 and 3 show honeycomb cores made of a sheet material to form polygonal cells typically having four or six cell walls, and the sheet material is a symmetric three-layer or five-layer (FIGS. 8 and 9) sheet material according to an embodiment of the present invention. The honeycomb core of the present invention can have cell walls 2 each having a single thickness, or cell walls consisting of 6 and 8, or cell walls consisting of 16, 6 and 8. Alternatively, one cell wall 4 of the honeycomb core can have two layers of the sheet material.

[0045] Embodiments of the present invention can provide a cellular structure such as a folded honeycomb structure, or a method and apparatus for manufacturing the same. In particular, the present invention relates to an improved thermoplastic honeycomb structure, a process and apparatus for manufacturing the same.

[0046] The advantages of the present invention are to utilize forming techniques such as vacuum forming or rotational vacuum forming. Thermoforming can also be used. These can be used as steps in the manufacture of honeycomb cores that enable continuous and cost - efficient production.

[0047] Honeycomb products manufactured according to embodiments of the present invention have improved compression resistance and allow for further reduction in material usage.

[0048] Embodiments of the present invention provide honeycombs that do not spread or expand fan - shaped, for example, from a stack of sheets adhered to each other.

[0049] Embodiments of the present invention provide a honeycomb formed from a plurality of polygonal cells arranged in an array, each polygonal cell having lateral cell walls extending between the vertices of each polygonal cell, each polygonal cell being bounded on two sides by a covering layer plane, and the lateral cell walls of each polygonal cell (sometimes referred to as the side walls of the cell) being composed of sheet material.

[0050] Embodiments of the present invention provide a honeycomb core having rectangular, square or hexagonal cells, whereby the cell walls of such a honeycomb core are composed of at least two materials. In some embodiments, the sheet material for making the honeycomb core has a symmetric three - layer ABA (or for example, a five - layer CABAC having a bonding layer) structure. Preferably, the B layer has a lower density compared to the A or C layer. The outer A layer is preferably smooth. The surface smoothness can be measured by micro - CT (micro - computed tomography) as well as a laser profile sensor.

[0051] The symmetric three-layer or five-layer structure is preferably made by film extrusion, more preferably by co-extrusion of the layers for example. Parameters that can affect the performance of the symmetric three-layer ABA or five-layer CABAC structure can include providing higher strength and rigidity in the outer A and / or C layers. If the density of the inner layer B is lower compared to the outer layers A or C, the performance of the honeycomb core made from the symmetric three-layer ABA or five-layer CABAC structure is significantly mechanically improved. This preferably extruded or co-extruded inner B layer should preferably have a lower density, for example 30% - 90% (optimally 50 - 70%) of the density of the outer layers A, C. The lower density can be provided by low-density components such as a layer B made by physical foaming (e.g., blowing) or chemical foaming, or by adding low-density components such as hollow glass spheres or other low-density fillers. The polymer density of the outer layer can vary from 0.9 kg / dm 3~ to 1.5 kg / dm 3 or even up to 2 kg / dm 3 depending on the type of polymer and the fillers used in the polymer. A lower density of 1.1 kg / dm 3 can be the lower density of the inner B layer when the polymer of the outer layer A or C has a density of 1.6 kg / dm 3 . When the polymer of the outer layer A or C has a density of 1 kg / dm 3 , the inner layer B should have at least 0.9 kg / dm 3 to gain advantages for the weight ratio bending and buckling performance of the cell walls.

[0052] Preferably, the symmetric three-layer ABA or five-layer CABAC sheet material is fed directly into a forming process, of which rotational vacuum forming is an example.

[0053] An alternative is to make the symmetric three-layer or five-layer structure by cast film extrusion, and the three-layer or five-layer structure can be fed directly onto a vacuum forming roller to produce a 3D structure within the extruded / cast sheet.

[0054] For good panel surface quality, the cell size should remain small, and thus the coextrusion wall thickness should preferably be less than 1 mm and at least 0.1 mm to provide a significant cell wall thickness increase.

[0055] To achieve a reasonable low density, the thickness of the central (or core) layer or inner layer in the coextrusion cell wall is at least 1 / 3 of the total cell wall thickness, or preferably at least 1 / 2, and most preferably 67% - 90%. The optimal weight ratio cell wall buckling strength is also a function of the density ratio between different layers. For optimal performance, the weight fraction of the central (or core) layer or inner layer should be between one-third (1 / 3) and one-half (1 / 2) of the total cell wall weight. A large ratio between the density of the material of the outer layer and the density of the material of the central (or core) layer results in a very thin outer layer and a large proportion of the thickness of the inner layer. A larger density ratio is preferred, but difficult to achieve in coextrusion.

[0056] Preferably, all three A, B, and C layers are based on the same thermoplastic polymer or compatible polymers to facilitate the recycling and refeeding of edge trims.

[0057] An additional element is that both the outer A and C layers must be flat and smooth. Foaming of the inner layer B or low-density fillers in the inner layer can result in a non-uniform surface of the outer A or C layer. Use micro-CT or laser profilometer sensor scans to measure out-of-plane non-uniformities compared to the ideal plane of the cell wall. The non-uniformity of the skin layer must be less than the thickness of the skin layer. Figure 7 shows on the left an ideally flat skin 13, 15 made of a 3-layer ABA or 5-layer CABAC (Figure 9) sheet material according to an embodiment of the present invention forming a sandwich cell wall, and on the right a sandwich cell wall having one flat skin 14 and one skin 12 having an out-of-plane non-uniformity greater than the thickness of the skin layer at two points (see arrows) (the same applies to 5-layer CABAC). Such skin layers buckle much earlier under in-plane compressive loads than flat skins.

[0058] For the compression performance of the cell wall and thus for the compression strength of the honeycomb core, it is advantageous if at least one or both of the outer A, C layers are flat and have only smooth thickness variations.

[0059] The first flat and smooth outer A or C layer can be achieved by contacting the smooth surface outside the rotary vacuum forming roller. However, the foaming process and / or the filler can cause local density variations in the inner B layer, which can lead to thickness variations in the inner B layer and a non-uniform second outer A or C layer.

[0060] For the good compression performance of the honeycomb core and the buckling performance of the sandwich cell wall, it has also been found possible and useful for the second outer layer to be flat and smooth.

[0061] This can be achieved by a cooling roller that cools the other side of the coextruded film and flattens the other outer layer before the still hot coextruded film is deformed within the vacuum forming roller.

[0062] There are also other options for flattening the outer A and C layers, such as calendering of the coextruded film after or during the foaming process and before rotary vacuum forming or other vacuum forming.

[0063] In a three-layer ABA cell wall, the B layer should have a lower density. Glass fibers of thermoplastic polymer (2.5 kg / dm 3)Reinforcement typically results in high density. For the other A and C layers, such reinforcement can be used, but for the inner B layer, low density is a more important parameter. This low density allows the inner layer to be thickened without adding much weight, and this greater total thickness provides performance advantages. The density ratio between the inner layer and the other layers is an important parameter of the present invention. This results in a larger cell wall thickness. The thickness of the cell wall is the cube of the buckling resistance of the other A layers of the sandwich cell wall. For the central B layer, fillers such as hollow glass spheres that allow the polymer density to be reduced can be used. Thus, different types of fibers and fillers may be useful for the other A and C layers, but vacuum or plug (i.e., plug-assisted thermoforming) or coextrusion and thermoplastic molding between two mating molds of opposed rollers or ABA cell walls are preferred.

[0064] Referring to FIGS. 1-9, a honeycomb core, i.e., a folded honeycomb core that can use the symmetric multi-layer (3-layer ABA or 5-layer CABAC) sheet material of the embodiments of the present invention, is disclosed.

[0065] Figures 2 and 3 show cross-sections of a flat sheet or web made of a plastically deformable material. This flat sheet can be provided by a symmetric three-layer ABA or five-layer CABAC sheet material according to any of the embodiments of the present invention. The three-layer ABA or five-layer CABAC sheet material according to any of the embodiments of the present invention is a plastically deformable material and is made of a thermoplastic polymer material, a fiber composite material, or the like. The three-layer ABA or five-layer CABAC sheet material according to the embodiments of the present invention is a thermoplastic polymer and / or a thermoplastic elastomer polymer, or a polyolefin, particularly polyethylene or polypropylene, a polyester, particularly polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene-1,2-furandicarboxylate, a polyamide, particularly polyamide 6 or polyamide 6,6, a polycarbonate, a polyether ketone, a polyether ether ketone, a polyether ether ketone, a polyether ketone ketone polyether, a polyether ester, a polyphenylene sulfide, a polyether imide, a copolymer, and a filler, a reinforcing agent and / or a mixture thereof with or without air or gas inclusions, which is composed of a thermoplastic polymer selected from the group consisting of. The inner core of the symmetric three-layer or five-layer thermoplastic coextruded sheet material may be a foam such as a mechanical foam or a chemical foam.

[0066] According to this embodiment, a flat web or sheet (3-layer ABA or 5-layer CABAC according to an embodiment of the present invention) has plastic deformation portions 101, 102 formed therein, mainly perpendicular to the material web. In regions 101 and 102, the material is deformed from the plane of the web, for example, into a polygon, for example, a trapezoid, or a sinusoidal curve, or an arc shape. The deformation portions form ridges 108 and valleys 109, whereby each of them is not continuous. For example, the ridge 108 is composed of a linear series of deformation portions 101, 102, such as a polygon, such as a trapezoid, or a sinusoidal curve, or an arc portion. Preferably, the ridge has an upper surface 115 that can be parallel to the plane of the material web initially (e.g., when formed). The two upper surfaces 115 abut against each other when the three-dimensional structure is rotated (also called "folded") to form honeycomb cells, and thus also form cell walls having twice the sheet thickness.

[0067] The manufacturing direction is preferably as shown in FIG. 1. However, the direction perpendicular thereto (parallel to axes 105 and 106) can equally well be used.

[0068] The deformation parts 101 and 102 are preferably formed by inclining, i.e., rotating, towards each other around the shafts 105 and / or 106, and additionally form U-shaped or V-shaped connection regions 103 and 104. The connection regions or connection parts 103 and 104 separate the deformation parts (bulging parts) 101, 102, for example, polygons in a row of the deformation parts 101, 102, such as trapezoids, or sine curves, or arc parts, etc. One of the connection parts 103, 104 is arranged between the two parts 101, 102, and the connection part 103 alternates with the connection part 104 along the row of the parts 101, 102. The connection regions 103, 104 form intersecting valleys, i.e., are perpendicular to the valley 109. The adjacent intersecting valleys are on both sides of the web material. The rotation of the parts 101, 102 to bring them to the initial position in FIG. 1 is preferably carried out simultaneously with the deformation being arranged on the web of the material. The web material is stretched at the transition between the parts 101 and 102 to form the regions 103 and 104 that are substantially perpendicular to the outer surfaces 115 of the parts 101 and 102. The angle between the surfaces 103, 104 on the different bulging parts 101 and 102 allows a part of the tool to enter and thus allows these parts to be formed. The width direction of the material web preferably extends in the directions of the shafts 105 and 106, and the endless length direction of the material web is continuous along the manufacturing direction at the line 107.

[0069] The deformation of the web or sheet material (3 - layer ABA or 5 - layer CABAC according to an embodiment of the present invention) in regions 101 and 102 serves the purpose of forming a three - dimensional shape that forms the walls of the cell halves of the folded end product. The cells thus formed are structural and load - bearing elements of the folded honeycomb core, and the cell walls extend transversely to the longitudinal direction of the folded end product. The use of a 3 - layer ABA sheet material or a 5 - layer CABAC sheet material according to an embodiment of the present invention improves mechanical performance. The cells formed by folding preferably have a cylindrical cross - section, and the axis of the cylinder extends transversely to the longitudinal direction of the folded end product and the thickness direction of the ultimately produced flat honeycomb core. The basic cross - sectional shape of the cell can be selected, for example, as circular or polygonal, particularly an even - numbered polygon such as a hexagon, as desired. The final cell shape is determined by the shape of the deformation regions 101, 102 of the original web and how they are folded. As shown in FIG. 1, when the web is fully folded, each cell is formed from two half - cells. The cells are arranged in rows. Each final cell is formed by the bottom and sides of two longitudinally adjacent valleys 109 (within the sheet or web material). The half - cells are preferably joined together across the contact upper surfaces 115 from two adjacent ridges 108 (within the web material) in the longitudinal direction. Thus, a folded honeycomb is provided, which is formed from a plurality of cells arranged in rows and has the following characteristics: all are made from a 3 - layer ABA sheet material or a 5 - layer CABAC sheet material according to an embodiment of the present invention, the cells are adjacent to each other in the form of a ring and have lateral cell walls bounded by the coating layer plane towards the two open side faces of the cell, whereby each cell is completely cross - linked or closed on one or the other side of the coating layer plane. The folded honeycomb can be formed from a substantially uncut flat web, i.e., a non - porous continuous sheet such as a 3 - layer ABA or 5 - layer CABAC sheet material according to an embodiment of the present invention. The sheet is extruded, more preferably co - extruded. The plastic deformation of the sheet forms a 3D structure.Thus, the folded honeycomb includes a plurality of 3D structures, such as polygonal, sinusoidal or arcuate portions (101 and 102) formed by plastic deformation, and connection portions (103 and 104) in the plane of the coating layer formed by plastic deformation. At least a part of the cell walls are preferably permanently connected to each other completely or partially, for example by an adhesive or glue or welding.

[0070] The final honeycomb structure is a planar product, and the cells are arranged perpendicular to the plane of the product and over its thickness. The cells on alternating sides of the planar structure are closed by connection portions 103, 104. All cells can be closed by the application of one or more coating layers, for example by laminating the planar product of the invention with a coating sheet. The invention includes within its scope the possibility that the portions (3D structures) 101, 102 in the web forming the cell walls, such as trapezoidal, sinusoidal or circular structures, are not completely perpendicular and / or do not contact each other after folding of the deformed material web, thus forming a structure that is open in-plane in at least one direction.

[0071] Returning to FIG. 1, the manufacturing method continues by further rotating portions 101 and 102 such that the surfaces 115 from adjacent raised portions 108 are adjacent to or preferably in contact with each other. FIG. 1 shows a further intermediate state in the manufacture of the folded honeycomb. The narrowing of the plastically deformed material web results from the folding operation of the material web about the folding lines or axes 105 and 106. The U-shaped or V-shaped connection portions 103 and 104 are unfolded and flattened in a plane perpendicular to the cell walls. The portions 103 and 104 are introduced to avoid substantial deformation of the 3D structure of the material web, such as into a polygon, such as a trapezoid, or into a sinusoidal or arcuate shape, such as the portions 101 or 102.

[0072] FIG. 1 also shows a material that is almost completely folded to form two columns of hexagonal honeycomb cells. As a result of the folding, the adjacent portions 103 (104 respectively) abut against each other as shown in FIG. 1. Then, each honeycomb cell is closed by a connecting portion 103 or 104 on at least one side (bottom side or top side) of each honeycomb cell. That is, the cell has a closed surface formed by the connecting portions 103, 104 at one end. The surfaces 115 can be connected to each other using, for example, an adhesive or a sticky agent, or by welding such as ultrasonic welding. However, this connection is not an essential requirement of the present invention.

[0073] The above process depends on folding a deformed web material (i.e., a 3-layer ABA or 5-layer CABAC sheet material according to an embodiment of the present invention), whereby the method of forming the parts (3D structures) 101, 102 and the connecting parts 103, 104 is carried out to facilitate the folding and rotation processes. FIG. 1 also shows a side view of the formed material web before the folding operation. To facilitate the folding operation, the plastically deformed material web preferably has axes 105 and 106 (around which the material regions 101 and 102 rotate during folding) arranged out of the plane with a positive value of dimension "x" (for further details, see WO 2006 / 053407, especially FIG. 7 thereof). The dimension x is selected such that the portion of the valley (formed by the connection) 103 on the upper surface of the material, or the intersecting valley (formed by the connection) 104, has its lowest apex junction point on the valley axis 106 higher than the apex junction point on the axis 105 of the intersecting valley on the lower surface of the web. The longitudinal force along the manufacturing direction acts through the axes 105 and 106, thereby applying a bending moment around the axes 105, 106. Thereby, the formed material web can be folded by simple compression in the manufacturing direction.

[0074] Manufacturing can be carried out continuously. Preferably, the roller pair is used to press the material web or sheet together in the manufacturing direction. However, a rotary tool, a vibrating translational tool, or a guiding profile can be used to assist or ensure the folding of the web or sheet. Thus, an independent aspect of the present invention is to form a honeycomb folded by non-cutting, continuous, static plastic, optionally non-rotary or plastic rotary forming of a material web. Plastic deformation can be carried out, for example, by rotary vacuum thermoforming or rotary thermoforming without vacuum, or by a 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 an extruder die. The mold has mutually engaging profiles, for example, on each of two mold surfaces, or on rolls running opposite each other.

[0075] The surface of the mold or roller, such as a vacuum roller for thermoforming a material sheet or web, not only forms portions 101 and 102 in the formed material web, but preferably has a relatively complex geometry to allow it to rotate slightly (e.g., 10 - 30°) towards each other. This enables the formation of V-shaped regions 103 and 104, ensuring a shape configured to be vacuum thermoformable and airtight for the material web that can be folded by further rotation (e.g., about 80° - 60°) of regions 101 and 102 around axes 105 and 106.

[0076] Figure 6 shows a side view of a material sheet or web during the folding operation and a cross-sectional view of the folding device according to an embodiment of the present invention. For a semi-closed thermoplastic honeycomb core with a thickness of 8 mm and a cell size cross-section of 6.4 mm open, the speed of the still-unfolded material sheet or web relative to the folded honeycomb core, i.e., the material take-up factor, can be 2.696 in any speed unit, which decreases to 2.5 within the first roller set 120 and then further decreases to 1 within the second roller set 122. The final speed is the throughput speed of the folded honeycomb planar structure.

[0077] The folding unit includes a pair of feed rollers 120, for example, coated with rubber on its outer surface 110. There is a groove 110a inside the outer surface of the feed roller 120. This supply roller is arranged upstream of the guide grid 111 to hold the material web in-plane during folding. Also, a second set or pair of pushing or opposing rollers 122, for example, coated with rubber on its outer surface 112, have similar grooves 112a to apply opposing pressure, which ensures an in-plane compressive force sufficient to enable folding. The compressive force between the lower feed roller and the upper feed roller 120 can reduce the inclination and rotation of regions 101 and 102 towards each other due to elastic deformation. However, in the portion between the feed roller 120 and the pushing opposing roller 122, although not necessarily so, the material web preferably returns to its thermoformed shape without the help of a tool or guide 111a as it continues to be folded. The gating and / or braking mechanism first delays or stops the web. This is opened by the force generated only by the material web at the fully folded stage. It continues to apply frictional force in its open state when the folded web is formed.

[0078] The folded honeycomb is preferably further processed directly into a lightweight sandwich panel by laminating or directly extruding a coating sheet or film 114 on both sides of the honeycomb core, for example, using a laminating roller or belt 123. The apparatus provided by the present invention can include a deformation and folding unit, as well as a core adhesion or welding unit and a laminating unit.

[0079] The web sheet material (3-layer ABA or 5-layer CABAC according to an embodiment of the present invention) can be provided directly from a roll of web material or a stack of sheet materials (3-layer ABA or 5-layer CABAC according to an embodiment of the present invention) to a suitable forming device such as an extruder or co-extruder. Optionally, the web or sheet of material is maintained at or heated to the forming or forming temperature. Regions (3D structures) 101, 102 are formed in the web or sheet material by any suitable process, such as vacuum forming or hot rolling. Instead of using vacuum drawing, opposing shaped pressure plates can be used to apply pressure and heat to a malleable (e.g., high temperature) thermoplastic sheet (3-layer ABA or 5-layer CABAC according to an embodiment of the present invention) to form semi-cells. This makes it possible to use perforated materials that would not be possible if a vacuum were applied. The perforation of the perforated material can be produced simultaneously with the application of pressure or can be made in the sheet (3-layer ABA or 5-layer CABAC according to an embodiment of the present invention) prior to the pressure forming step. Producing a honeycomb core from the perforated sheet (3-layer ABA or 5-layer CABAC according to an embodiment of the present invention) can be good for noise attenuation. Pressure forming can also be used.

[0080] The web material with the 3D structure formed is folded together to form a honeycomb core. Optionally, the lamination of one or more coating layers or other layers is performed either in-line or off-line. For example, post-treatment operations such as cutting the honeycomb material to length or forming it into a shape can be performed by pressing or fixing the honeycomb material to another, such as a metal part.

[0081] The present invention includes a folded honeycomb in which connection regions or portions 103 and 104 are later removed (e.g., during the lamination of a nonwoven coating layer), such as by cutting or melting, so that all cells are open on both sides, thus resulting in a 3D formable sandwich preform.

Claims

1. A folded honeycomb core formed from a plurality of polygonal cells arranged in an array, wherein each polygonal cell has a lateral cell wall, each polygonal cell is bounded on both sides by a covering layer plane, the lateral cell walls of each polygonal cell form a polygonal ring, the lateral cell walls are composed of a sheet material, the sheet material is a symmetrical three- or five-layer thermoplastic co-extruded sheet material having a central (or core) layer or inner layer and an outer layer, the central (or core) layer or inner layer having a density of 30% to 90%, preferably 50% to 70%, of the density of the outer layer.

2. The honeycomb core according to claim 1, wherein the yield strength of the outer layer is greater than the yield strength of the central (or core) layer or the inner layer.

3. The honeycomb core according to claim 1, wherein the central (or core) layer or the inner layer is manufactured by physical foaming or chemical foaming, or by being composed of low-density components.

4. The honeycomb core according to claim 3, wherein the low-density component includes hollow glass particles.

5. The polymer density of the outer layer is 0.9 to 1.5 or 0.9 to 2 kg / dm ３ The honeycomb core according to claim 1, which is within the range.

6. The outer layer is 1.6 kg / dm ３ If it has a density of 1.1 kg / dm³, the central (or core) layer or inner layer is 1.1 kg / dm ３ A honeycomb core according to claim 1, having the density of [value].

7. The outer layer is 1 kg / dm ３ If it has a density of 0.9 kg / dm³, the inner core is 0.9 kg / dm³ ３ The honeycomb core according to claim 6, having the following density.

8. The honeycomb core according to claim 3, wherein the co-extruded wall thickness of the three or five layers is 1 mm or less and at least 0.1 mm.

9. The honeycomb core according to claim 8, wherein the central (or core) layer or inner layer of the co-extruded wall preferably has a thickness of at least 1 / 3 of the total cell wall thickness, more preferably 67% to 90%, or preferably at least 1 / 2 of the total cell wall thickness.

10. The honeycomb core according to claim 1, wherein the outer layer is flat and smooth with no out-of-plane non-uniformity compared to the ideal plane of the cell wall, and the non-uniformity of the outer layer is less than the thickness of the outer layer.

11. The honeycomb core according to claim 1, wherein the symmetrical three- or five-layer thermoplastic co-extruded sheet material is selected from thermoplastic polymers and / or thermoplastic elastomer polymers, or thermoplastic polymers selected from the group consisting of polyolefins, particularly polyethylene or polypropylene, polyester, particularly polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate or polyethylene-1,2-flangecarboxylate, polyamide, particularly polyamide 6 or polyamide 6,6, polycarbonate, polyether ketone, polyether ether ketone, polyether ether ketone, polyether ketone ketone polyether, polyether ester, polyphenylene sulfide, polyetherimide, copolymer, and mixtures thereof with or without fillers, reinforcing agents and / or air or gas-containing materials.

12. The honeycomb core according to claim 11, wherein the central (or core) layer or the inner layer and the outer layer are made of the same thermoplastic polymer.

13. The honeycomb core according to claim 1, wherein the outer layer is composed of a structural thermoplastic material, or the outer layer is composed of a solid thermoplastic material.

14. A method for manufacturing a folded honeycomb core from a sheet material, a) Direct co-extrusion and rotational vacuum thermoforming of symmetrical multilayer sheet materials, followed by folding, b) Reheating of co-extruded or laminated multilayer sheet material, and transfer for rotary vacuum forming or sequential compression forming, followed by folding. Methods that include...

15. The method according to claim 14, further comprising forming a plurality of polygonal cells arranged in an array, each polygonal cell having a lateral cell wall, each polygonal cell being bounded on both sides by a covering layer plane, the lateral cell wall of each polygonal cell forming a polygonal ring, the lateral cell wall being composed of a sheet material, the sheet material being a symmetrical three- or five-layer thermoplastic co-extruded sheet material.

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