Sandwich panels for load-bearing vehicles

Abstract

A sandwich panel for a vehicle, comprising at least a core layer (2) and two fiber layers (7) in contact with and firmly connected to the core layer (2), both sides of which are impregnated with polyurethane, wherein the polyurethane is embedded in the fibers and bonded to the board, and wherein the sandwich panel further comprises at least: a polyether polyurethane foam layer (6) which is completely impregnated with polyurethane and in contact with and firmly connected to the outer surface of at least one fiber layer through the polyurethane; and a surface layer (5) on the outer surface of the polyether polyurethane foam (6) which is not in contact with the fiber layer (7), wherein the surface layer (5) is composed of compressed polyurethane.

Description

Technical Field

[0001] The present invention relates to a sandwich panel for a vehicle capable of carrying a load, such as a battery electric vehicle, a personal car or a small delivery van, a method for producing such a part and the use of such a panel in a vehicle. Background Art

[0002] Personal cars and small transport vehicles may have a trunk or similar area where cargo can be loaded and transported. Floor panels used in such areas must be able to carry high loads. Typically, these panels are made as sandwich panels with a rigid core and skin layers to enhance bending stiffness.

[0003] Three-layer sandwich structures are preferably used in automotive lightweight engineering, where flat and shell-shaped panels are required to withstand high bending loads. In this structure, the upper and lower layers are made of fiber-reinforced composite materials, which provide the composite material with bending strength and are able to withstand the resulting compressive and tensile stresses. The fibers serve as reinforcing components and are connected to each other by a textile structure or an adhesive web.

[0004] Polyurethane (PU) is often used to fix the glass fiber mat and also facilitates lightweight construction due to its controlled foaming properties. In addition to fixing the glass mat, the PU matrix can also be used to bond the honeycomb core to the facing layer in the sandwich structure.

[0005] An example of such a sandwich load floor according to the prior art, for example disclosed in EP1609576, has a cardboard honeycomb core and a glass fiber mat skin, wherein the core and the glass mat are bonded by impregnation with a reactive polyurethane mixture. The layers moistened with the polyurethane are placed in a mold and compression molded into the desired shape. In this molding step, the polyurethane reacts by forming a foam, thereby increasing the pressure in the closed mold. The impregnated foam bonds the layers together. This provides a strong load floor, but with a poor appearance. Although the fibers are embedded in the foam, they are still visible on the surface.

[0006] A big disadvantage of the current process is that the pressure forces the polyurethane material into the interior of the honeycomb structure, rather than filling the cavities formed in the surface decoration or mold surface to provide the desired surface appearance and texture. The gases generated during the foaming process will also form bubble defects on the surface of the produced part. It is therefore impossible to obtain good definition of surface features (such as ribs, designs or beads in the form of wood or leather grain on the surface of the part). Therefore, in practice, these load-bearing floors are covered with an aesthetic layer, such as carpet, for the used or visible surface (called the A surface), and leave a poor back side (called the B surface).

[0007] In some vehicles, if the load being carried is likely to damage or soak the A surface, especially for wet loads or loads with the possibility of liquid spillage, it is foreseeable to turn the load floor to the B surface. Although the fiberglass in the B surface is initially protected, harsh use may damage the foam embedding, for example by scratching, and the fiberglass ends may protrude from the surface and become a hazard, making the B surface worse.

[0008] Adding additional layers to the B surface can provide a better appearance, but will increase the weight of the final part and add complexity to the production process.

[0009] The object of the present invention is to optimize the sandwich panels of the prior art and in particular to obtain a more versatile lightweight alternative to current load-bearing floors, as well as a method of producing such a panel which does not have the known disadvantages in question. Summary of the invention

[0010] This object is achieved by a sandwich panel having the features described in the invention, by a method for producing such a panel having the features described in the invention and by the use of such a panel according to the invention.

[0011] In particular, this is achieved by a sandwich panel for a vehicle, which comprises at least a core layer, which is covered with fiber layers (7) on both sides to form a sandwich, both sides of which are impregnated with polyurethane, wherein the polyurethane is embedded in the fibers and bonded to the core material, characterized in that the sandwich panel further comprises at least: an elastic sheet foam layer based on polyether polyurethane, which is completely permeated and engulfed by the polyurethane and is in contact with and firmly connected to the outer surface of at least one fiber layer through the polyurethane; and a surface layer on the outer surface of the polyether polyurethane foam not in contact with the fiber layer, which surface layer consists of compressed polyurethane, and wherein the polyurethane expands inside the core layer to bond adjacent layers to the core layer without completely filling the core layer structure.

[0012] Surprisingly, by using a polyether polyurethane elastic foam layer on top of the fiber layer before wetting with the polyurethane foam mixture, all layers are well fixed together, the amount of foam in the core layer structure is reduced and the surface clarity is increased. In addition, scratch resistance can be increased. The combination of high elastic polyether polyurethane foam and dense open-cell structure seems to play the role of polyurethane foam guide or foam flow resistance during the compression molding process of the part. However, the structure is initially open enough to obtain good penetration of polyurethane foam through the polyether-polyurethane board foam layer and the fiber layer and on the contact surface between the core layer and the fiber layer, thereby ensuring uniform bonding of all layers. In addition, the foam enables better filling of the surface structure in the mold, and a thick, scratch-resistant and uniform surface layer is formed on the surface of the part through the pressure and temperature enhancement of the mold.

[0013] Preferably, polyether polyol-based elastic polyurethane sheet foams are used. For example, sheet foams produced from polyether polyols and isocyanate TD80, both of which can be optionally modified. If necessary, additional additives such as catalysts, stabilizers, dyes or flame retardants can be added. Amine catalysts can be used as catalysts.

[0014] Alternatively, conventional polyether polyurethane foams modified by combustion may be used, e.g. Promoted flexible polyether polyurethane foams. These foams are typically used in the upholstery and furniture markets and are less well known in the field of automotive trim parts and cladding structures.

[0015] Preferably, the net density of the polyether polyurethane foam is 20 to 26 kg / m 3 .

[0016] Preferably, the polyether polyurethane foam layer has a surface weight of 48 to 240 gsm, preferably 72 to 192 gsm.

[0017] Surprisingly, a thin layer of polyether-polyurethane foam with a thickness of 2 to 10 mm, preferably 3 to 5 mm, is already sufficient to obtain the desired effect of better wetting and impregnation distribution flow of polyurethane on the cover layers of the sandwich stack and inside the 3D surface features.

[0018] Preferably, the foam is resilient and has a 40% compressive strength measured using ISO 3386 between 5.0 and 6.5 kPa.

[0019] The impregnation of the polyether-polyurethane sheet foam and the underlying fiber layer is obtained by wetting these layers with the polyurethane mixture; this is preferably achieved by spraying the mixture. The spray head or the part to be wetted can be moved to obtain a uniform spread of the mixture. Preferably, a higher amount of the mixture can be applied locally to strengthen areas or in areas with increased thickness and / or increased 3D definition or as required.

[0020] To obtain a strong sandwich, both sides of the sandwich stack are wetted.

[0021] A mixture of polyols and isocyanates can be used as the wetting polyurethane mixture, which is premixed just before application. Preferably, when the wetted layer is placed in the heated tool, it contains its full foaming potential so that the pressure and temperature of the closed tool together enable a uniform distribution in all layers and in the surface details.

[0022] The polyurethane-forming mixture typically used in the process of the present invention will typically comprise:

[0023] - at least one polyol component having an average OH number of 300 to 700, comprising at least one short-chain polyol and one long-chain polyol, each polyol having a functionality of 2 to 6;

[0024] - at least one isocyanate;

[0025] -optionally a blowing agent;

[0026] - activator;

[0027] - Optional auxiliary substances, release agents and additives.

[0028] Suitable polyols may be polyester or polyether based.

[0029] US808485 discloses a preferred mixture for wetting the polyether and the fiber layer, the mixture comprising an isocyanate component and a polyol component comprising one or more natural oil-based polyols, which mixture can be used with the present invention according to the present application.

[0030] Preferably, the surface weight of the polyurethane foam used for wetting is 200 to 2000 gsm. If one surface is covered with carpet or other layers, different amounts may be used to wet the A and B surfaces, e.g. 600 gsm for the A surface with carpet and 1400 gsm for the B surface with upholstery.

[0031] Preferably, the reaction rate is optimal at a temperature of 130° C. The temperature conditions of the mold are adjusted accordingly.

[0032] Preferably, the first and second fiber mats are used to cover both sides of the core structure and act as reinforcement layers.The first and second fiber mats are preferably identical, but may consist of different fibers, fiber mixtures or fiber layers.

[0033] Preferably, the first fiber mat and / or the second fiber mat comprises at least one of the following: inorganic fibers such as glass, carbon, basalt or aramid fibers, synthetic fibers such as polyester, polyolefins such as polyethylene or polypropylene, or polyamide fibers, organic regenerated fibers such as viscose, rayon or modal fibers, natural fibers such as hemp, flax, kenaf, bamboo or other cellulosic fibers, animal fibers such as wool fibers or any possible mixture of these fibers. The fibers may be from virgin, recycled or recycled sources.

[0034] Preference is given to using glass fibre mats or mats comprising glass fibres, since this increases the bending stiffness.

[0035] With respect to fibers, both endless filaments and cut filaments forming staple fibers are meant to be within the scope of the present invention.

[0036] Preferably, without foam impregnation, the pad has an area weight of 100 to 900 gsm.

[0037] Preferably, the core layer is a separator having a honeycomb, corrugated or tubular sand structure or a closed cell foam structure.

[0038] The thickness of the core layer is 2 to 30 mm, preferably 5 to 20 mm, preferably the thickness is variable.

[0039] As a preferred core layer, a sheet-type material providing bidirectional support may be used, preferably having openings mainly in the thickness direction of the sheet, such as a tubular, corrugated or honeycomb sheet.

[0040] Preferably, the core layer is made of plastic, for example one of polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyamide, or polyolefin types such as polypropylene or polyethylene, polylactic acid-based materials, polyetheretherketone (PEEK), polycarbonate or natural materials such as paper or cardboard, or of inorganic materials such as aramid or of a combination of natural fibers and resins or of metals such as aluminum.

[0041] The raw material can be folded into an expandable form to reduce storage before production. Therefore, the folded form is unfolded and fixed before the production of the automotive part.

[0042] Paperboard honeycomb is preferred because it is foldable, lightweight and low cost. The paperboard must be strong enough to withstand the pressure during production. Paper weights of 70 to 140 gsm are preferably used.

[0043] Preferably, the honeycomb used has cells with a diameter of 4 to 10 mm, preferably 6 to 8 mm. The cell diameter can be determined based on the final load requirements, scratch resistance of the top surface and the 3D design, and can vary with the paper weight and board thickness used.

[0044] Reducing the cell diameter of the honeycomb makes the part more stable and stiffer. Surprisingly, the 3D definition of the surface is also enhanced, as is the scratch resistance, because the polyurethane foam is compressed more and the skin becomes denser.

[0045] Alternatively, polyester, polypropylene, polyethylene or aramid honeycombs of similar dimensions may be used.

[0046] In a preferred solution, a rigid closed-cell foam, preferably a polyester closed-cell foam, is used as the core layer.

[0047] The impermeable polyester foam core layer has a compression modulus of at least about 30 MPa measured according to ISO 844, preferably a minimum of 55 MPa.

[0048] The polyester foams claimed in accordance with the present invention are based on thermoplastic polyester resins and are preferably made from foamable grades of semi-crystalline polyethylene terephthalate (PET). These thermoplastic polyester resins produce closed-cell foams when they are melt-extruded with suitable chemical or physical blowing agents. The foams can be made from recycled polyester or virgin raw materials or a combination of both. Within the scope of the present invention, polyester (especially polyethylene terephthalate) foams as core layers do not include polyester-based polyurethane (PUR) foams.

[0049] The density of the closed-cell PET foam layer is 60 to 200 Kg / m 3 , preferably 75 to 120 Kg / m 3 .

[0050] After molding, additional layers can be laminated to at least one surface, such as one selected from tufted carpet, nonwoven carpet, knitted layer, foil layer, foam, spray or RIM surface layer, foil, film or scrim layer. Embossments can also be laminated only locally like patches or logos to further enhance aesthetics or functionality, such as anti-slip mats.

[0051] Carpet or other textile surface coverings can be bonded or laminated into the grooves in the sides of the panels to obtain a flush fit and a nice finish to the parts.

[0052] Preferably, an additional surface layer is added to at least one of the surfaces, which is completely or partially covered with an in-mold coating. Examples of such an in-mold coating could be localized logos or text, or technical coatings such as making the part impermeable to water or grease, to obtain a thermally conductive, electrically conductive or electromagnetic shielding layer on at least one of the surfaces.

[0053] Preferably, the reversible board forms a carpet-type layer on one surface and a surface according to the invention on the other surface, which surface optionally has a surface pattern, ribbing or raised edges to further enhance the functionality of the layer. In addition, if the panel is used as a horizontal load-bearing board, such as a floor, load floor or battery cover, drainage holes or guide ribs can be integrated to drain overflowing liquids.

[0054] Other features can be introduced directly into the panel during or after compression molding, such as clips, mounting fixtures, handles, nuts, brackets or reinforcements, etc. These fixtures are preferably made of polyamide or polyester, metal. Optionally, carbon fiber or glass fiber reinforcements can be used.

[0055] A method for producing a sandwich panel according to the invention, comprising:

[0056] - wetting a sandwich stack comprising at least one core layer and two fiber layers, which are in contact with the surface of the core layer on both sides, with a polyurethane-forming mixture comprising a foam stabilizer;

[0057] - placing the wetted sandwich stack in a compression mold;

[0058] -closing the mold and maintaining the mold in a temperature range of 40°C to 200°C to mold the part and harden the polyurethane foam forming mixture to form a molded part, wherein the polyurethane is embedded in the fibers and bonded to the core layer; removing the molded product from the mold, characterized in that the sandwich stack further includes at least one polyether board foam layer covering the outer surface of the fiber layer, wherein on this side the polyurethane mixture is applied on top of the polyether polyurethane foam surface, and the polyurethane penetrates the board foam layer as well as the fiber layer and bonds to the core layer, and wherein during compression of the stack in the closed mold, a polyurethane skin layer is formed on top of the polyether polyurethane foam surface that is not in contact with the fiber layer.

[0059] The method may further comprise the step of in-mould coating an additional layer on top of the skin layer.

[0060] The method may further comprise the step of laminating an additional layer on the skin layer after the thermocompression moulding step, advantageously the residual heat available in the component is used to facilitate the lamination step.

[0061] Where necessary, normal cutting and finishing steps can also be added to the process.

[0062] The floor according to the invention can be used as a load floor (i.e. the main floor of the passenger compartment), as a roof module, an engine hood, a tailgate module, a door module, a floor module, a parcel shelf, a spare wheel cover, an interior component, as a battery or battery pack cover, as a computer or battery box or as a partition. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 Schematic diagram of a car with examples of components that can be produced according to the invention.

[0064] Figure 2 and 3 Schematic layout of material layers in the final product.

[0065] Figure 4 Schematic diagram of the production of a part according to the invention.

[0066] Figure 1 A personal vehicle rear area 20 is partially shown with a load floor that can be produced according to the invention. The load floor can be designed with at least one surface according to the invention, preferably with two surfaces according to the invention. Preferably, the load floor is designed so that it can be flipped between an A side and a B side as opposing surfaces on the load floor panel, wherein one side can be provided with a carpet-type surface, such as a tufted carpet or a non-woven carpet, while the other side can have an exposed surface according to the invention.

[0067] Figure 2 and 3 An exemplary cross section of a sandwich panel (1) according to the invention is shown, which has a honeycomb core (2) with chambers 3 forming open channels between two surfaces of the core. The walls of the channels can be formed from different materials, such as but not limited to paper, paperboard or plastic materials such as polyolefin, polypropylene, polyethylene or polyester based materials and composite materials made of natural fibers and thermoplastics.

[0068] Although the core layer depicted is a honeycomb, other grid forms such as tubular, corrugated, or closed cell foam may be used.

[0069] The core material is preferably covered on both sides with fiber layers (7) to form a sandwich, although the covering layers may be different between the two sides, their tensile strength properties under hot conditions must be uniform to prevent warping of the part.

[0070] At least on one side the covering layer (4) may consist of at least a fiber layer (7) and a polyether polyurethane foam layer (6) which are penetrated and filled with polyurethane foam. The polyurethane foam will form a skin layer (5) on top of the polyether polyurethane foam layer, being pressed into the polyether polyurethane foam layer and into the fiber layer, and a small amount will eventually expand in the top (8) of the open channels of the honeycomb core material, by doing so it also binds the core layer and the other layers together. Due to molding in a compression mold, the covering structure is compressed to form a dense skin layer and an overall strong structural layer.

[0071] The layers so bonded together form a strong sandwich that can withstand high loads on its surfaces without substantially bending or sagging.

[0072] Figure 2 The structure can be used for many different applications and, thanks to the use of polyether polyurethane foam on one or both sides, it is possible to use the panels without any covering layer. The fiber structure of the fiber mats is no longer visible, especially when they are glass fiber mats, and possible damage to the surface will no longer release the fiber contents.

[0073] In addition to the plate's use as a load floor or passenger compartment floor, it can now also be used as a floor in the front trunk (the storage space at the front of an electric vehicle).

[0074] It is also possible to use the board as a battery cover or computer panel or box, as the material is very light weight yet has high stiffness and impact protection. If required, the board can be further locally reinforced with metal beams or metal plates to further enhance the crash protection. It is also possible to introduce crash break lines in the core to enable crash zones when required.

[0075] Figure 3Also shown is a preferred embodiment of a panel according to the invention which is constructed as a reverse load floor, e.g. Figure 1 The main layout and reference numerals are as follows. Figure 2 However, here the reversible load floor has an A surface (A) and a B surface (B), both of which are good enough to form an A-quality surface, but have different functions.

[0076] The A surface in this case is a typical carpet surface with a tufted carpet (17) laminated on the molded part.

[0077] The B surface is now formed of a dense polyurethane skin, wherein the surface contains a decoration in the form of a raised pattern on the surface of the part, with knobs (14) and ribs (15) filled primarily with the polyurethane skin material. In addition, the surface contains a raised edge (16) at the edge of the part, wherein the raised edge is formed primarily of a polyether polyurethane foam layer (6) (not to scale) which rebounds to push the polyurethane foam (5') back into the recess in the mold, further filling the space to form a dense foam (5') and an even denser skin layer (5) on the foam, thereby resulting in a durable edge.

[0078] Figure 4 Schematically shows the main steps in a preferred production process of a sandwich panel according to the invention

[0079] Wetting the material layer (100) on both sides with the polyurethane mixture, in particular by placing the material in sequence below or opposite one or more polyurethane spray heads 12, which can be moved relative to the surface to be covered. The polyurethane can be mixed and metered immediately before spraying, for example using a first metering system (9) for isocyanate and a second metering system (10) for polyol into a mixing unit 11. Additives can be added to the raw materials or directly to the mixing unit;

[0080] Transferring the material stack thus wetted into a heated mold having a first mold half 13a and a second mold half 13b (200), which can be closed together to form the final part;

[0081] Heat compression molding the part (300) by closing the mold and keeping it closed under pressure. The heat of the mold will (further) activate the polyurethane mixture, creating foam pressure, which helps the mixture spread between the layers and form a skin on the surface of the part;

[0082] The part is demoulded (400).

[0083] After demoulding, an additional surface layer, such as a carpet layer, may be placed on top of at least one of the surfaces to create a surface with a good soft surface. For example, a tufted or non-woven carpet layer or fabric, such as a neoprene fabric, may be used. Preferably, a small groove is made in the panel to obtain an even level with the top of the carpet surface when positioned.

[0084] As an additional step, other implements may also be connected to the part, such as handles, hinges, etc., depending on the part and its function.

Claims

1. A sandwich panel for a vehicle, comprising at least A core layer, which is covered on both sides with fiber layers (7) to form a sandwich, and which is impregnated on both sides with polyurethane, wherein the polyurethane is embedded in the fibers and bonded to the core layer material, characterized in that The sandwich panel further comprises at least: a polyether polyurethane foam layer, which is completely permeated and filled with polyurethane and contacts and is firmly connected with the outer surface of at least one fiber layer through polyurethane; and a surface layer on the outer surface of the polyether polyurethane foam layer not in contact with the fiber layer, the surface layer is composed of compressed polyurethane, and the polyurethane expands within the core layer to bond adjacent layers to the core layer without completely filling the core layer structure.

2. The sandwich panel according to claim 1, wherein the surface weight of the polyether polyurethane foam layer is 48 to 240 gsm.

3. The sandwich panel according to claim 1, wherein the surface weight of the polyether polyurethane foam layer is 72 to 192 gsm.

4. The sandwich panel according to claim 1, wherein the polyurethane used for the impregnation is based on polyester or polyether polyols.

5. The sandwich panel according to one of claims 1 to 3, wherein the area weight of the polyurethane used for the impregnation is 200 to 2000 gsm.

6. The sandwich panel according to claim 1, wherein a first fiber mat and a second fiber mat are used to cover both sides of the core structure and act as reinforcement layers, the first fiber mat and the second fiber mat being made of the same or different fibers, fiber mixtures or fiber layers.

7. The sandwich panel according to claim 6, wherein the first fiber mat and / or the second fiber mat comprises at least one of the following: inorganic fibers; synthetic fibers; organic regenerated fibers; natural fibers; or a mixture of these fibers.

8. The sandwich panel according to claim 6, wherein the first fiber mat and / or the second fiber mat comprises at least one of: glass, carbon, basalt or aramid fibers; polyester, polyolefin, or polyamide fibers; viscose, rayon or modal fibers; hemp, flax, kenaf, bamboo or other cellulosic fibers; wool fibers; or a mixture of these fibers.

9. The sandwich panel according to claim 6, wherein the first fiber mat and / or the second fiber mat has an area weight of 100 to 900 gsm.

10. The sandwich panel according to one of claims 1 to 3, wherein the core layer is a separator having a honeycomb, corrugated or tubular sand structure or a closed-cell foam structure.

11. The sandwich panel according to one of claims 1 to 3, wherein the core material is made of plastic, or of inorganic material, or of a combination of natural fibers and resin, or of metal.

12. The sandwich panel according to one of claims 1 to 3, wherein the core material is made of one of the following: polyester, polyamide, or polyolefin type, polylactic acid based material, polyetheretherketone (PEEK), polycarbonate or natural material, or aluminum.

13. The sandwich panel according to one of claims 1 to 3, wherein the core material is made of one of the following: polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polypropylene or polyethylene, or paper.

14. The sandwich panel according to one of claims 1 to 3, wherein the core layer is a honeycomb panel with a pore diameter of 4 to 10 mm.

15. The sandwich panel according to one of claims 1 to 3, wherein the core layer is a honeycomb panel with a pore diameter of 6 to 8 mm.

16. The sandwich panel according to one of claims 1 to 3, wherein the core material is a laminate having a density of 60 to 200 kg / m 3 Polyester closed cell foam board.

17. The sandwich panel according to one of claims 1 to 3, wherein the thickness of the core layer is 2 to 30 mm.

18. The sandwich panel according to one of claims 1 to 3, wherein the thickness of the core layer is 5 to 20 mm.

19. The sandwich panel according to one of claims 1 to 3, further comprising protrusions or surface patterns formed in a skin layer at least on one surface of the panel.

20. The sandwich panel according to claim 19, wherein the protrusions are a decorative protrusion pattern.

21. The sandwich panel according to claim 19, wherein the surface pattern is a wood grain or a leather grain, or a reinforcing rib.

22. The sandwich panel according to one of claims 1 to 3, further comprising an additional layer fully or partially laminated to at least one surface.

23. The sandwich panel of claim 22, wherein the additional layer is selected from one of a tufted carpet, a non-woven carpet, a knitted layer, a foil layer, a foam, a spray or RIM surface layer, a film, a scrim layer or a logo or anti-slip mat.

24. The sandwich panel according to one of claims 1 to 3, further comprising an additional surface layer added to at least one surface, said at least one surface being fully or partially covered with an in-mould coating.

25. The sandwich panel of claim 24, wherein the in-mould coating is one of an aesthetic coating, a coating impermeable to water and / or grease, a thermally conductive coating, an electrically conductive coating or an electromagnetic shielding coating.

26. A method for producing a sandwich panel according to one of claims 1 to 25, comprising: - wetting a sandwich stack comprising at least one core layer and two fiber layers, which are in contact with the surface of the core layer on both sides, with a polyurethane-forming mixture comprising a foam stabilizer; - placing the wetted sandwich stack in a compression mold; - Closing the mold and maintaining the mold in a temperature range of 40°C to 200°C to mold the part and harden the polyurethane foam forming mixture to form a molded part, wherein the polyurethane is embedded in the fibers and bonded to the core layer; removing the molded product from the mold, characterized in that the sandwich stack further includes at least a polyether polyurethane foam layer covering the outer surface of the fiber layer, wherein on this side the polyurethane mixture is applied on top of the surface of the polyether polyurethane foam layer, and the polyurethane penetrates the polyether polyurethane foam layer and the fiber layer and bonds to the core layer, and wherein during compression of the stack in the closed mold, a polyurethane skin layer is formed on top of the surface of the polyether polyurethane foam layer that is not in contact with the fiber layer.

27. Use of a sandwich panel according to one of claims 1 to 25 or produced according to the method according to claim 26 as a roof module, an engine hood, a tailgate module, a door module, a floor module, a parcel shelf, a spare wheel cover, an interior component, as a battery or battery pack cover, as a computer or battery box or as a partition.

Images