Lightweight panel containing corrugated elements

Description

AREA OF INVENTION

[0001] The present invention relates to a multilayer composite comprising a corrugated lightweight panel element consisting of interconnected wood fibers. The invention further relates to the use of the multilayer composite. BACKGROUND OF THE INVENTION

[0002] It is known to use composite materials to produce multilayer composites that have relatively high mechanical stability compared to their weight.

[0003] CH 254025 relates to a multilayer composite comprising two face plates and a core layer in between, the core layer comprising at least one layer of folded veneer.

[0004] DE 42 01 201 relates to semi-finished or finished products made of wood, which are manufactured from plate-shaped surface elements. The plate-shaped elements may be zigzag-shaped.

[0005] DE 10 2008 022 806 relates to a lightweight panel with a wavy wood veneer layer. The waves can be zigzag-shaped.

[0006] BE 547 811 relates to a core layer consisting of two zigzag-shaped wooden elements arranged between two cover layers.

[0007] DE 10 2008 022805 A1 concerns a corrugated veneer panel and lightweight panels constructed from it. The corrugated structure of the wood elements used can be zigzag, sinusoidal, or trapezoidal.

[0008] EP 1 923 209 relates to a lightweight composite panel with outer layers and a middle layer, wherein the middle layer is arranged at an angle to the plane of the lightweight composite panel.

[0009] These prior art multilayer composites have in common that the core layer has a loose structure. When a force is applied perpendicular to the surface of the multilayer composite, it exhibits a damping effect, since the core layer can be compressed, at least partially.

[0010] One disadvantage of loosely layered cores can be that they may exhibit low homogeneity, caused by relatively large cavities in the core layer.

[0011] Lightweight panels with improved stability are described in EP 2 660 408 A1 and WO 2015 / 067362.These patent applications relate to a core layer suitable for a multilayer composite comprising at least one cover layer and a core layer, wherein the cover layer is arranged such that it at least partially covers the core layer and is firmly connected to it, wherein the core layer comprises elements made of wood having plate-shaped areas arranged in a zigzag pattern, wherein a plate-shaped zigzag area of ​​one element shares a common edge with an adjacent plate-shaped zigzag area of ​​the same element, such that the zigzag-shaped wood element is formed, wherein zigzag-shaped elements are arranged in the core layer such that two such edges of two different elements intersect at an angle other than zero, and wherein the two elements are firmly connected to each other at the point of intersection.

[0012] EP 2 488 337 B1 (WO 2011 / 079920) relates to a process for producing a particle-based element, namely a particleboard or fiberboard, wherein the element can be wavy in a longitudinal direction or wavy in a longitudinal direction and a lateral direction respectively.

[0013] EP 1 758 733 B1 (WO 2005 / 113230 A1) relates to a sandwich element comprising at least two face layers and at least one middle layer arranged between the face layers in the form of a periodically recurving doubly curved shell structure with opposing principal curvatures, a method for its manufacture and use.

[0014] EP 2 873 522 discloses a method for producing a composite panel and a composite panel.

[0015] EP 1 272 715 (WO 00 / 58581 A1) discloses a composite component having a non-planar composite track.

[0016] EP 3 126 110 (WO 2015 / 149942) discloses a method for producing a wave-shaped wooden element.

[0017] JPH10-278014 reveals a wavy plate made of plant fragments. TASK OF INVENTION

[0018] Due to the constantly increasing demand for lightweight panels with high stability under load, the object of the present invention is to provide suitable products, in particular products that possess the highest possible strength and load-bearing capacity at the lowest possible weight. Furthermore, these lightweight panels should be cost-effective to manufacture, especially through the integration of the manufacturing technology into existing production facilities. SUMMARY OF THE INVENTION

[0019] This problem is solved according to the invention with a multilayer composite as defined in claim 1. Preferred embodiments are defined in the claims directly dependent on claim 1. The use is defined in the claim indirectly dependent on claim 1.

[0020] The terms used below in quotation marks are defined in accordance with the invention. BRIEF DESCRIPTION OF THE FIGURES

[0021] The figures show Fig. 1 showing a schematic side view of a wave-shaped element, at least one wave, here a sinusoidal wave; Fig. 2 a top view of the wave-shaped element of the Fig. 1 , where the solid lines symbolize wave crests (positive half-wave) and the dashed lines symbolize wave troughs (negative half-wave); Fig. 3 shows a top view of a lightweight component of the Fig. 2 ,when the wave crests and wave troughs are themselves deformed in a wave-like shape; Fig. 4 a side view of the element of Fig. 3 , when the second wave is superimposed by a third wave. Fig. 5 shows a schematic perspective representation of the arrangement of Fig. 3 . DETAILED DESCRIPTION OF THE INVENTION Lightweight panel elements

[0022] An element which can be used to produce a multilayer composite according to the invention is arranged such that it extends along a surface – in particular a flat surface – wherein the element has a first wave-like progression along the surface with an elongation that varies along a first direction of propagation, wherein wave crests of the top and wave troughs of the bottom of the element are arranged parallel to each other along a second direction, wherein this second direction lies at an angle α with 0° < α ≤ 90°, preferably approximately 90°, to the first direction and along this surface, wherein the element consists of interconnected wood fibers.

[0023] Thus, both the top and bottom surfaces of the element are part of a wave. The wave crests are located on the top surface, and the corresponding wave troughs are located on the bottom surface. The wave crests can also be referred to as wave tops.

[0024] The term "Element" This refers to a component or part of the multilayer composite according to the invention in the form of a lightweight panel. In the following, this element will also be referred to as a lightweight panel element.

[0025] The term "Wave" In physical terms, the element is illustrated by a spatially expanding vibration. In their broadest sense, the terms describe "Wave" or "Wave structure"' or "wavy" or "wavelike" The wave contains at least one crest and one trough. Therefore, in a mathematical sense, the wave has at least one positive and one negative half-wave.

[0026] The terms used also include repeating wave-like structural units within the element.

[0027] In mathematical terms, a wave can be characterized by its elongation, amplitude, and the plane of oscillation of the positive or negative half-wave, i.e., the wave crest and trough. Characterization via wavelength, i.e., the length of a wave crest and the subsequent wave trough, is also possible. The transition between a wave crest and a wave trough can be characterized—depending on the wave's shape—by an inflection point in the wave's path or by a straight segment.

[0028] The wave can be varied with respect to its amplitude or wavelength, or both. This allows the thickness of the core layer in the lightweight panel to be influenced, as well as its stiffness. Conversely, the stiffness of the lightweight panel can also be influenced by panel parameters such as the thickness of the wave (i.e., the thickness of the corrugated or wave-like element in the lightweight panel), the particle and fiber geometry within the element, the density of the elements in the panel, and the degree of bonding between the elements and with the surface layers of the panel.

[0029] The wave can be either a transverse (straight line) or a radially propagating or extending wave.

[0030] The shape of the wave can take on any conceivable structure.

[0031] In one embodiment, the wave is in the form of a sine function or a function similar to a sine function, i.e., it is in the form of a sine function and / or is sinusoidal. The following terms "sinusoidal" or "sinusoid" Used synonymously.

[0032] In another embodiment, the shaft is designed in the form of a triangular oscillation. The term "Triangular oscillation" also includes the term "triangle-like oscillation".

[0033] In another embodiment, the shaft is designed in the form of a sawtooth oscillation. Such an oscillation can also be described as a tilting oscillation.

[0034] In another embodiment, the shaft is designed in the form of a rectangular oscillation.

[0035] The waveforms mentioned are known in physics and can also be described mathematically.

[0036] In another embodiment, the wave has different waveforms, i.e. at least two, or three or four waveforms selected from: triangular oscillation, sinusoidal oscillation, sawtooth oscillation or rectangular oscillation.

[0037] In one embodiment, these waves can be arranged in any order within the wave-shaped element along a common direction of propagation.

[0038] In another embodiment, two or more of the aforementioned types of vibration can also superimpose in a common direction of propagation and form a correspondingly new waveform.

[0039] For example, a trapezoidal oscillation can be created through suitable superposition.

[0040] The wave shape in the wave-like element can also be described by stating that the wave-like element, in the form of a lightweight panel element, has plate-shaped areas, whereby a plate-shaped area in the wave-like element shares a common edge with an adjacent plate-shaped area in the wave-like element, such that the element is wave-shaped. Thus, the plate-shaped areas, including the edge, form a wave.

[0041] The term "plate-shaped areas" This includes areas formed in the form of surfaces. The surfaces can be flat, i.e., planar, or uneven, i.e., not planar, preferably curved, preferably convex or concave, or corrugated.

[0042] The term "Edge" includes terms such as "Transition zone between two adjacent plate-shaped areas"This transition area can be a sharply defined edge. The term also includes an edge that is shaped like a curved surface or like a flat (planar) surface. Thus, the term includes "Edge" A sharp edge in the form of a line, as well as a wavy or undulating edge in the form of a curved plane or a curved area between two plate-like areas, are included. Thus, the plate-like areas in the wave-like element form a wave-like structure, i.e., a wave trough is followed by a wave crest and vice versa.

[0043] Preferably, edges formed by adjacent plate-shaped areas in the wave-shaped element are aligned parallel to each other.

[0044] The term "curved surface"This means a convex surface, a concave surface, or a surface that has both convex and concave parts. In particular, the term means... "curved" also "continuously curved".

[0045] Thus, a wave-shaped element is also disclosed which has plate-shaped areas, wherein a plate-shaped area in the wave-shaped element forms a common edge between itself and an adjacent plate-shaped area in the wave-shaped element, such that the element is wave-shaped, wherein (a) the plate-shaped areas are flat surfaces and the edge formed between the flat surfaces is a line.Such a wave can be described as a zigzag wave; or (b) the plate-shaped areas are flat surfaces and the edge formed between the flat surfaces is a curved surface; or (c) the plate-shaped areas are flat surfaces and the edge formed between the flat surfaces is a flat surface; or (d) the plate-shaped areas are curved surfaces and the edge formed between the curved surfaces is a curved surface, preferably a convex surface; or (e) the plate-shaped areas are curved surfaces and the edge formed between the curved surfaces is straight; or (f) the plate-shaped areas are curved surfaces and the edge formed between the curved surfaces is a flat surface.

[0046] In one embodiment, the shaft has at least one, two, three, four, five, or six of the waveforms (a) to (f).

[0047] In one embodiment, the element is formed from (c') an element (c) such that the wave, viewed in longitudinal section, has repeating units in the form of a trapezoid; or (d') elements (d) such that the wave, viewed in longitudinal section, has repeating units in the form of a sine function or a sinusoidal function.

[0048] The good compressive and shear strength and stiffness of elements (a) to (f) or of a core layer containing these elements or of a multilayer composite containing the core layer can be significantly improved if the core layer contains or consists of elements (d') in particular.

[0049] Such waveforms are known and are described in EP 2 660 408 A1 and WO 2015 / 067362. For further explanation, explicit reference is made to these documents.

[0050] In an embodiment according to the invention, the at least one positive and negative half-wave, i.e. the wave crest and the wave trough, are superimposed by a second wave.

[0051] This also means that the first wave, and therefore the lightweight panel element, is deformed or warped, forming the second wave.

[0052] The shape of the second wave can be chosen independently of the shape of the first wave from among the shapes described above in relation to the first wave.

[0053] In one embodiment, if the first wave propagates in a Cartesian coordinate system with the spatial axes x, y and z in the x-direction and the plane of vibration lies in or parallel to the x,z-plane, the plane of vibration of the first wave is perpendicular to the plane of vibration of the second wave, wherein the second wave propagates in the y-direction and the plane of vibration lies in or parallel to the y,z-plane.

[0054] In a preferred embodiment, if the first wave propagates in a Cartesian coordinate system with the spatial axes x, y and z in the x-direction and the plane of vibration lies in or parallel to the x,z-plane, the plane of vibration of the first wave is perpendicular to the plane of vibration of the second wave, wherein the second wave propagates in the y-direction and the plane of vibration lies in or parallel to the x,y-plane.

[0055] In another preferred embodiment, the second wave, and thus the lightweight panel element, is further deformed and shaped to form the third wave.

[0056] Thus, the second wave, and therefore also the first wave, is superimposed by a third wave.

[0057] Of course, it is also conceivable to superimpose the third wave, and thus also the first and second waves, with a fourth wave, or to superimpose the fourth wave, and thus also the first, second and third waves, with a fifth wave, etc.

[0058] The shape of the third wave can be chosen independently of the shape of the first and second waves from among the shapes described above in relation to the first and second waves.

[0059] Preferably, the plane of vibration of the third wave runs parallel to the plane of vibration of the first wave.

[0060] In another embodiment, the plane of vibration of the first wave and the plane of vibration of the second wave are perpendicular to each other, with the plane of vibration of the third wave being parallel to the plane of vibration of the first wave.

[0061] In a preferred embodiment, if the first wave propagates in a Cartesian coordinate system with the spatial axes x, y and z in the x-direction and the plane of vibration lies in or parallel to the x,z-plane, the plane of vibration of the first wave is perpendicular to the plane of vibration of the second wave, wherein the second wave propagates in the y-direction and the plane of vibration lies in or parallel to the x,y-plane, and the plane of vibration of the third wave lies in or parallel to the y,z-plane, wherein the third wave propagates in the y-direction.

[0062] With such an embodiment, the stability of the elements, and thus the stability of the lightweight panel, can be further improved. Such an element exhibits a comparatively increased stiffness, since a type of [missing information] is incorporated into the element. "Stiffening ribs" is generated. In addition, the triple corrugation further reduces the probability of wave crests or troughs of adjacent superimposed elements sliding into each other during the production of the lightweight panel, if these elements have the same or similar basic orientation.

[0063] The wave-shaped element consists of interconnected wood fibers.

[0064] The term "fiber" refers to a structure that is thin and flexible relative to its length. Preferably, the length-to-diameter ratio should be at least between 3:1 and 10:1.

[0065] The lightweight panel element contains an adhesive. The adhesive bonds the fibers together to increase strength.

[0066] The invention further discloses a lightweight panel element extending along a surface – in particular a flat surface – wherein the lightweight panel element has a first wave-like progression along the surface with an elongation that varies along a first direction of propagation, wherein wave crests of the top and bottom of the lightweight panel element are arranged parallel to each other along a second direction, wherein this second direction lies at an angle α with 0° < α ≤ 90°, preferably approximately 90°, to the first direction and along this surface, and wherein a second wave-like progression of a second wave of the lightweight panel element is superimposed on this first wave-like progression, such that the wave crests of the first wave-like progression exhibit further undulation along at least this second direction, and wherein the lightweight panel element consists of interconnected wood fibers. Production of wave-shaped elements

[0067] Lightweight panel elements suitable for the invention as defined above can generally be produced by a method comprising at least stages (A) and (B) or (A) and (C): (A) Arranging fibers such that the fibers touch each other; (B) Pressing the touching fibers of stage (A) in a pressing tool, wherein the pressing tool is designed such that the corrugated element obtained after pressing has the first wave or the second wave or the third wave; or (C) Pressing the touching fibers of stage (A) in a pressing tool and guiding the pressed fibers and / or chips through a profiling tool, wherein the profiling tool is designed such that the lightweight panel element obtained after passing through has the first wave or the second wave or the third wave.

[0068] Thus, the element obtained in stages (B) or (C) can have the first wave, the first wave superimposed by the second wave, or the first wave superimposed by the second wave, with the second wave in turn being superimposed by the third wave.

[0069] In one embodiment, it is possible to arrange the fibers in the pressing tool in stage (A). Thus, stage (A) has stage (A1) and stage (B) has stage (B1): (A1) Arranging fibers such that the fibers touch each other, wherein the fibers are arranged in a pressing tool; (B1) Pressing the touching fibers of stage (A1) in the pressing tool, wherein the pressing tool is designed such that the wave-shaped element obtained after pressing has the first wave or the second wave or the third wave.

[0070] In another embodiment, it is possible to arrange the fibers in stage (A) in such a way that the fibers touch each other, and to press them flat or evenly and then to feed the pressed material to stage (B).

[0071] Therefore, level (A) then has level (A2) and level (B) has level (B2): (A2) Arranging fibers such that the fibers touch each other, the fibers being compressed to form a flat arrangement; (B2) Compressing the compressed fibers of stage (A2) in a pressing tool, the pressing tool being designed such that the corrugated element obtained after compression has the first wave or the second wave or the third wave.

[0072] The lightweight panel element can be manufactured according to a process comprising at least stages (A) and (B) or (A) and (C): (A) Arranging wood fibers such that the fibers are oriented; (B) Pressing the contacting fibers of stage (A) in a pressing tool, wherein the pressing tool is designed such that the lightweight panel element obtained after pressing has the first wave or the second wave or the third wave; or (C) Pressing the contacting fibers of stage (A) in a pressing tool and guiding the pressed fibers through a profiling tool, wherein the profiling tool is designed such that the lightweight panel element obtained after passing through has the first wave or the second or the third wave.

[0073] The wood fibers used in stage (A) for the production of the lightweight component are, for example, generated in the wood processing industry.

[0074] In one embodiment, the pressing tool of stage (B) has protrusions and depressions that at least partially contact the fibers during pressing. Using suitable protrusions and depressions, the first and second, and optionally the third, wave of the lightweight panel element can be designed according to the invention, preferably embossed.

[0075] Suitable pressing devices and methods for forming elements comprising a shaft are known, for example, from EP 2 488 337 B1. Suitable pressing devices for manufacturing the lightweight panel element can be designed accordingly.

[0076] In one embodiment, the pressing tool of stage (B) has no protrusions or depressions. In this case, no wave structure is imprinted into the fibers or chips. They can then be guided through a suitable profiling tool in stage (C), which then forms the wave structure.

[0077] In one embodiment, the profiling tool of stage (C) has one or more profiling rollers. Using suitable profiling rollers, the shafts of the lightweight panel element can be designed according to the invention.

[0078] The pressures used during pressing can be adjusted to the requirements. In one embodiment, the pressure is in the range of 5 to 15 MPa. The use of higher or lower pressures is possible in other embodiments.

[0079] In stage (A), the fibers are at least partially contacted with an adhesive. This further increases the stability of the elements.

[0080] The element produced using this method is not limited in its dimensions. Round or rounded lightweight panel elements, as well as polygonal lightweight panel elements, can be manufactured.

[0081] Preferably, rectangular lightweight panel elements are manufactured, defined by a length and width.

[0082] In one embodiment, pressed fibers are used in stage (B) or (C) which are dimensioned such that the ratio of length to width of the manufactured lightweight panel element is in the range of 2 : 1 to 50 : 1, more preferably in the range of 2 : 1 to 40 : 1.

[0083] In one embodiment, the lightweight panel element contains the product of length x width in the range of 10 mm x 5 mm to 3000 mm x 1000 mm.

[0084] Thus, in one embodiment, relatively small lightweight panel elements as well as track-shaped lightweight panel elements can be manufactured.

[0085] In a further embodiment, relatively large lightweight panel elements, which are preferably designed in a strip-like form, can be subjected to a comminution step if relatively small lightweight panel elements are to be produced from these strip-like elements.

[0086] Relatively small lightweight panel elements preferably have a length x width product in the range of 10 x 5 mm to 200 x 100 mm, more preferably 10 x 5 mm to 100 x 50 mm, and more preferably 10 x 5 mm to 50 x 25 mm. The term "Length" This means the shortest distance between the beginning and end of the wave-like element in the longitudinal direction of the element. The term "Width" This means the distance between the side edges perpendicular to the longitudinal direction of the element.

[0087] Preferably, in stage (A) fibers are used in the process which are dimensioned such that the element obtained according to the process according to stages (B) or (C) has a thickness in the range of 0.1 to 5 mm, preferably 0.2 mm to 3.5 mm, more preferably 0.2 mm to 2 mm.

[0088] The term "Thickness" This refers to the smallest distance between two opposing surfaces of a wave-shaped element. These surfaces are separated by the thickness of the plate-like areas or the edge.

[0089] The thickness of the corrugated sheet does not necessarily have to be the same at all points along the shaft. It is possible that the crests and troughs, or even the straight sections between them, may have different thicknesses. Furthermore, the pressing technique used may result in areas of varying thickness within the shaft.

[0090] Preferably, the method is carried out such that the recesses and protrusions of the pressing tool of stage (B) or the profile of the profiled tool of stage (C) are selected such that the wave height of the lightweight panel element is in the range of 1 to 20 mm, preferably 2 to 12 mm, more preferably 2 to 8 mm.

[0091] The terms "wave height" This means the smallest distance between two imaginary, parallel planes between which the wave-shaped element can be arranged such that the waves lie between these planes.

[0092] In a particularly preferred embodiment, the thickness of the wave-shaped element is in the range of 0.2 to 5 mm and the wave height is in the range of 2 to 15 mm.

[0093] In another particularly preferred embodiment, the thickness of the wave-shaped element is in the range of 0.2 to 2 mm and the wave height is in the range of 2 to 8 mm.

[0094] The lightweight panel elements produced according to the method preferably have a bulk density in the range of 150 to 430 kg / m 3<.

[0095] The manufactured wave-shaped elements possess excellent load-bearing capacity, so that they can be used as or for a loose core layer or in multilayer composites with a loose core layer, which in turn allow a high load-bearing capacity at a relatively low density. Core layer, exhibiting wave-shaped elements

[0096] Core layers as disclosed herein feature lightweight panel elements as defined above, or feature lightweight panel elements manufactured according to a process as defined above.

[0097] The term "core layer" This means a layer which, in addition to the lightweight panel elements, also has cavities, i.e., a loose structure.

[0098] The term "Layer"becomes synonymous with the term "Location" used.

[0099] In one embodiment, the lightweight panel elements are arranged in the core layer in at least a first and a second layer and are at least partially bonded together.

[0100] In another embodiment, the at least one first and second layer each contain a plurality of lightweight panel elements.

[0101] In one embodiment, the lightweight panel elements are arranged at least partially randomly in the first layer and the second layer. This embodiment is particularly advantageous when the lightweight panel elements have relatively small dimensions.

[0102] In a further preferred embodiment, the at least one first and second layer of the core layer each contain only one lightweight panel element. Preferably, in this embodiment, strip-shaped lightweight panel elements are used.

[0103] In this embodiment, the angle between the first direction of the first wave in the first layer and the first direction of the first wave in the second layer can be 90°. The term "Angle of 90°" It also allows deviations of ± 10°. Methods for producing a core layer such as defined above

[0104] The present disclosure relates to a process for producing a core layer as defined above, comprising at least the stages (D) to (F): (D) Arranging at least one lightweight panel element as defined above, or manufactured according to a method as defined above, wherein the at least one corrugated element forms a first layer; (E) Arranging at least one second lightweight panel element as defined above, or manufactured according to a method as defined above, on the first layer, wherein the at least one lightweight panel element arranged on the first layer forms a second layer, such that the first and the second layer at least partially form two superimposed layers; (F) At least partially bonding the lightweight panel elements to each other.

[0105] The at least one lightweight panel element is arranged in step (D) on a suitable support. The support is preferably a material with a flat surface on which the element(s) can be arranged.

[0106] The process may further comprise at least stage (E1): (E1) Arranging at least one further lightweight panel element as defined above, or manufactured according to a process as defined above, on the second layer of stage (E), wherein the lightweight panel element arranged on the second layer forms at least partially a third layer, such that the second and third layers form at least partially two superimposed layers.

[0107] The secure connection of the step (F) can be facilitated by applying pressure. This pressure is preferably in the range of 0.02 MPa to 4.0 MPa, more preferably in the range of 0.01 to 3.0 MPa. multi-layer composite

[0108] The invention discloses a multilayer composite, comprising at least a first cover layer or a first and a second cover layer and a core layer, wherein the core layer is a core layer as defined above, or a core layer is produced as described above, wherein the core layer is bonded to the first cover layer or the first cover layer and the second cover layer, wherein the core layer is located between the first and the second cover layer when the multilayer composite comprises the second cover layer.

[0109] This means that the first top layer, or the first and second top layers, are bonded to the core layer over their entire surface.

[0110] In one embodiment, the first or the second or the first and the second cover layer each have two sides spaced apart by a thickness, and the side which is bonded to the at least one element is profiled.

[0111] The profile can have a wave-like structure. The profile can be applied to the surface layer using suitable tools.

[0112] This has the advantage that additional cavities can be introduced into the multi-layer composite to save weight, without adversely affecting the stability of the composite too much.

[0113] Preferably, the first facing layer or the second facing layer or the first facing layer and the second facing layer independently comprise a material selected from: veneer, wood panel such as engineered wood panel or solid wood panel, particleboard, fiberboard, plywood panel, plastic panel, plasterboard, sheet metal, fiber cement board, and from two or more thereof.

[0114] Preferably, at least one top layer is flat, i.e., has a level surface.

[0115] The surface layers are not limited in terms of their shape.

[0116] Preferably, at least one top layer has a square or rectangular shape.

[0117] The dimensions of the top layer are not limited.

[0118] Preferably, for rectangular shapes, the width and length are each in the range of 0.50 m to 5 m, more preferably in the range of 1 to 3 m.

[0119] In an embodiment according to the invention, the multilayer composite has a core layer which merely comprises or consists of a wave-shaped lightweight element as defined in claim 1.

[0120] Accordingly, the invention also relates to a multilayer composite, comprising at least a first cover layer or a first and a second cover layer, a core layer and cavities between the core layer and the cover layer or the cover layers, wherein the core layer comprises or consists of only a lightweight panel element as defined above, or a lightweight panel element manufactured according to a method as defined above, wherein the core layer is bonded to the first cover layer or the first cover layer and the second cover layer, wherein the core layer is located between the first and the second cover layer when the multilayer composite comprises the second cover layer. Production of a multilayer composite

[0121] If the core layer of the multilayer composite has only one lightweight component or consists of only one lightweight component, a process can be used to manufacture the lightweight composite which only involves arranging and bonding the one lightweight component on the first cover layer, with the second cover layer optionally being bonded to the core layer. Deformed core layer

[0122] In one embodiment, the core layer, as defined above or produced according to the method defined above, can be subjected to a compression forming step, whereby three-dimensional objects can be produced. For this purpose, the core layer can be deformed in a suitable press tool. This deformation can take place during the production of the core layer as well as afterward.

[0123] In one embodiment, only the edges of the core layer are deformed, preferably by compression. This makes it possible to seal the cavities at the edges of the core layer. This compression forming can be carried out during the assembly of the core layer, but also after assembly in a subsequent stage, for example by thermally softening the adhesive at the edges. This embodiment has the advantage that a bar structure can be introduced into the core layer or its edges.

[0124] Compression allows for the outer part of the core layer to be given a convex, or rounded, profile. This is often desirable, for example, in high-quality furniture components.

[0125] In another embodiment, not only the edge area but also additionally or separately from the edge area, other areas of the core layer can be pressure-deformed.

[0126] A method for producing three-dimensional wooden objects by pressure forming is described in DD 271870 and DE 101 24 912. The process conditions mentioned therein can also be applied to the core layer according to the invention.

[0127] Thus, a deformed core layer is disclosed, comprising lightweight panel elements as defined above, or comprising lightweight panel elements manufactured according to a method as defined above, wherein the lightweight panel elements are at least partially deformed, producible by a method comprising at least stage (U): (U) compression deformation of the core layer as defined above or of the core layer manufactured according to a method as defined above. Deformed multilayer composite

[0128] In one embodiment, the multilayer composite according to the invention, as defined above or produced according to the method defined above, can also be subjected to a compression forming step, whereby three-dimensional objects can be produced. This compression forming can be carried out in a manner defined above.

[0129] Accordingly, the invention thus discloses a deformed multilayer composite, comprising at least a first cover layer or a first and a second cover layer, wherein the core layer is a core layer as defined above, or a core layer is produced according to a method as defined above, wherein the core layer is bonded to the first cover layer or to the first and the second cover layer, wherein the core layer is located between the first and the second cover layer when the multilayer composite has the second cover layer, wherein the core layer and the first cover layer or the core layer, the first and the second cover layer are at least partially deformed, comprising at least the stage (V): (V) compression deformation of the multilayer composite as defined above, or of the multilayer composite produced according to a method as described above. Uses

[0130] The invention relates to the use of a multi-layer composite as defined above in structural engineering, building construction, prefabricated construction, finishing, interior finishing, for sound and heat insulation, for interior fittings, furniture, doors and door panels, decorations, in vehicle construction, caravan construction, ship interior finishing, aircraft interior finishing and in packaging technology. EXAMPLES

[0131] Elements that aid in understanding the invention are shown schematically in the drawings. They are explained in more detail below with reference to the figures in the drawings. Figures

[0132] Fig. 1Figure 1 shows a schematic side view of a lightweight component featuring at least one wave, in this case a sinusoidal wave. The wave propagates in the x-direction in a Cartesian coordinate system, with the plane of oscillation of the wave lying in or parallel to the x,z-plane. The wave can also be described as consisting of plate-shaped regions a and b, which enclose a common edge c between them. The plate-shaped regions are curved, and the edge is also a curved surface. Fig. 2 shows a top view of the x,y-plane of the lightweight component of the Fig. 1 , where the solid lines symbolize wave crests (positive half-waves) and the dashed lines symbolize wave troughs (negative half-waves). Fig. 3 shows a top view of the x,y-plane of the lightweight component of the Fig. 2 ,where the wave crests and troughs of the first wave are distorted, i.e., superimposed by a second wave, which is sinusoidal. Here, if the first wave propagates in a Cartesian coordinate system with the spatial axes x, y, and z in the x-direction and the plane of oscillation of the first wave is parallel to the x,z-plane, the plane of oscillation of the first wave is perpendicular to the plane of oscillation of the second wave, where the second wave propagates in the y-direction and the plane of oscillation lies in or parallel to the x,y-plane. Fig. 4 shows a side view of a lightweight panel element starting from the lightweight panel element of the Fig. 3 ,where the second wave is distorted, i.e., superimposed by a third wave, the third wave being sinusoidal. Here, if the first wave propagates in a Cartesian coordinate system with the spatial axes x, y, and z in the x-direction and the plane of oscillation is parallel to the x,z-plane, the plane of oscillation of the first wave is perpendicular to the plane of oscillation of the second wave; if the second wave propagates in the y-direction and the plane of oscillation lies in or parallel to the x,y-plane; if the plane of oscillation of the third wave lies parallel to the y,z-plane, the third wave propagates in the y-direction. Fig. 4 It also shows a side view of a lightweight panel element starting from the lightweight panel element of the Fig. 2 ,where the first wave is deformed, i.e., superimposed by a second wave. Here, if the first wave propagates in a Cartesian coordinate system with the spatial axes x, y, and z in the x-direction and the plane of oscillation lies in or parallel to the x,z-plane, the plane of oscillation of the first wave is perpendicular to the plane of oscillation of the second wave, where the second wave propagates in the y-direction and the plane of oscillation of the second wave lies in or parallel to the y,z-plane. Fig. 5 shows a schematic perspective representation of the arrangement of Fig. 3 . The sinusoidal first wave is superimposed by a sinusoidal second wave, or the wave crests and wave troughs of the sinusoidal first wave are themselves sinusoidally wavy. Application example (not according to the invention)

[0133] In one application example, large-format, 5 mm thick surface layers made from a mixture of particleboard surface chips and particleboard adhesive were pressed using a correspondingly profiled, heated press plate at a pressing temperature of 180 °C and a pressing time of 4 minutes. The wave height was 3.5 mm with a wavelength of 6 mm.

[0134] In parallel, large-format corrugated elements with the same corrugation dimensions and a thickness of 0.6 mm, made from the same base material, were produced using a correspondingly profiled pair of press plates. After pressing, the crests and troughs of the corrugations were coated with adhesive in a roller gluing machine. This was followed by cutting into 40 mm wide strips using roller cutters and then breaking into particles 30 to 45 mm long. These particles (lightweight panel elements) were then spread in layers by a spreading machine onto the previously produced top layer, with the corrugation profile facing upwards, up to a height of 28 mm. Finally, the top layer was applied, and the press package was compressed to a thickness of 25 mm at a temperature of 180 °C.

[0135] A lightweight panel with a density of 250 kg / m 3< and a closed surface that can be coated with veneer or foil was obtained.

Claims

1. Multi-layer composite, comprising at least a first cover layer or a first and a second cover layer, a core layer and cavities between the core layer and the cover layer or the cover layers, wherein the core layer consists of a lightweight panel element, where the lightweight panel element extends along a - in particular flat - surface, wherein the lightweight panel element has a first wave-shaped course of a first wave running along the surface with an elongation that changes along a first direction of propagation, in which wave crests of the top and bottom of the lightweight panel element are arranged in parallel to one another along a second direction of propagation, wherein this second direction of propagation being at an angle α with 0° < α < 90°, preferably approximately 90°, to the first propagation direction and along the surface, wherein the core layer is bonded to the first cover layer or the first cover layer and the second cover layer over the surface, the core layer being located between the first cover layer and the second cover layer if the multilayer composite has the second cover layer, and wherein the cover layer or one of the cover layers is flat, wherein the lightweight panel element has a thickness in the range of from 0.1 to 5 mm, wherein the term "thickness" means the smallest distance between two opposite surfaces of the lightweight panel element, characterized in that the lightweight panel element consists of wood fibers and adhesive and that the wood fibers are connected to one another with the aid of the adhesive to increase the strength of the lightweight panel element.

2. Multilayer composite according to claim 1, wherein a second wave-shaped course of a second wave of the wave-shaped lightweight panel element is superimposed on the first wave-shaped course such that the wave crests and wave troughs of the first wave-shaped course have a further corrugation along at least the second propagation direction.

3. Multilayer composite according to claim 1 or 2, wherein a third wave-shaped course of a third wave is superimposed on the second wave-shaped course of the second wave.

4. Multilayer composite according to one of claims 2 or 3, wherein, when the first wave propagates in a Cartesian coordinate system with the spatial axes x, y and z in x-direction and the oscillation plane of the first wave is parallel to the x,z-plane, the oscillation plane of the first wave is perpendicular to the oscillation plane of the second wave, wherein the second wave propagates in the y-direction and its oscillation plane is parallel to the y,z-plane.

5. Multilayer composite according to one of claims 2 or 3, wherein, when the first wave propagates in a Cartesian coordinate system with the spatial axes x, y and z in x-direction and the oscillation plane of the first wave is parallel to the x,z-plane, the oscillation plane of the first wave is perpendicular to the oscillation plane of the second wave, wherein the second wave propagates in the y-direction and its oscillation plane is parallel to the x,y-plane.

6. Multilayer composite according to claims 3 and 5, wherein the oscillation plane of the third wave is parallel to the y,z-plane, wherein the third wave propagates in the y-direction.

7. Multilayer composite according to one of the preceding claims, wherein the wave height is in the range of from 1 to 20 mm, wherein the wave height is defined as the smallest distance between two imaginary planes being in parallel to one another, between which the wave-shaped element can be arranged such that the waves lie between these planes.

8. Multilayer composite according to one of the preceding claims, wherein the adhesive is selected from the group consisting of: glutin, casein, urea formaldehyde, phenol formaldehyde, resorcinol formaldehyde, melamine formaldehyde, polyvinyl acetate and polyurethane.

9. Multilayer composite according to one of the preceding claims, wherein the lightweight panel element is in the form of a web.

10. Multilayer composite according to one of the preceding claims, wherein each wave is in the form of a sine function or a function which is similar to a sine function, i.e. it is in the form of a sine function and / or is sinusoidal.

11. Multilayer composite according to claim 10, wherein the first cover layer or the second cover layer or the first cover layer and the second cover layer independently from one another comprises / comprise a material selected from: veneer, wood panel such as wood-based panel or solid wood panel, chipboard, fiberboard, plywood panel, plastic panel, plasterboard, sheet metal, fiber cement panel, and two or more of these.

12. Use of a multilayer composite according to one of claims 1 to 11 in shell construction, building construction, prefabricated construction, finishing, interior construction, for sound and heat insulation, for interior fittings, furniture, doors and door panels, decorations, in vehicle construction, caravan construction, ship interior construction, aircraft interior construction and in packaging technology.