Sandwich panel, component for an interior fitting in a vehicle, and method for manufacturing a curved component

Abstract

A sandwich panel (100) comprises a first face layer (110), a second face layer (120), and a core layer (130). The core layer (130) is positioned between the two face layers (110, 120) and bonded to both. The core layer (130) is a thermoplastic foam core. The first face layer (110) and the second face layer (120) each contain a phenolic resin-glass fiber mixture. A method for manufacturing such a sandwich panel is also described.

Description

Technical field

[0001] This description relates generally to lightweight construction technology, and in particular to the structure of sandwich panels and a method for manufacturing sandwich panels. Furthermore, the description relates specifically to a component consisting of or comprising such a sandwich panel, as well as a method for manufacturing a curved component from a sandwich panel. Technical background

[0002] Sandwich panels are preferred in lightweight construction because they offer high specific mechanical strength and resistance to external loads at a comparatively low weight. Sandwich panels consist of two face sheets and a core layer in between. Due to their construction, sandwich panels are typically manufactured as flat or planar elements. They are often manufactured or cut to a specific size or shape for installation in their intended environment. Description

[0003] It can be considered an object of the invention to provide curved sandwich panels which are characterized by high specific mechanical properties and have a homogeneous and uniform outer surface.

[0004] This problem is solved by the subject matter of the independent claims. Further embodiments are described in the dependent claims and in the following description.

[0005] From a first perspective, a sandwich panel comprises a first facing layer, a second facing layer, and a core layer. The core layer is positioned between the first and second facing layers and is bonded to both. The core layer is a thermoplastic foam core. The first and second facing layers each contain a phenolic resin-glass fiber composite.

[0006] A sandwich panel generally consists of two outer layers and a core or core layer arranged between the two outer layers.

[0007] Each face sheet has at least one layer of face sheet material. The face sheets are bonded to the core layer at opposite surfaces, for example, by gluing. The face sheets are made of stable materials with a higher density than the core layer. Materials such as wood, plastics, or various laminates can be used for the face sheets. For example, the face sheets are made of impregnated fiber braid (in a woven or parallel structure, or a combination thereof). Each layer of a face sheet can, for example, contain a layer of glass fiber. The fibers can be embedded in a thermosetting matrix, thus forming a layer of the face sheet. For example, the fiber braid is impregnated in phenolic resin.

[0008] The core layer consists of a material with a significantly lower density compared to the outer layers. The density of the core layer is determined by its mass and volume when installed in the sandwich panel. To achieve this comparatively low density, the core layer typically contains voids. In this case, the core layer consists of a thermoplastic foam core.

[0009] Foam cores consist, for example, of PVC foam (polyvinyl chloride foam), PET foam (polyethylene terephthalate foam), PMI foam (polymethacrylimide), PPSU foam (polyphenylsulfone), PIR foam (polyisocyanurate), or any other suitable foam. PET foam exhibits high mechanical strength and is therefore well-suited for absorbing compressive loads. Furthermore, these foams exhibit high specific shear strength and specific shear elongation at break.

[0010] The stable face sheets distribute compressive loads perpendicular to the surface normal of the sandwich panel evenly across the lightweight core layer, enabling the core layer to absorb these loads. Furthermore, shear loads are effectively absorbed by the lightweight core material when the sandwich panels are bent. The face sheets, on the other hand, resist tensile and compressive loads within the plane of the panel.

[0011] This design results in excellent stability of the sandwich panels while maintaining a low weight.

[0012] The sandwich panel structure described here allows it to be produced not only as a flat component, but also in virtually any geometric shape. Because the core layer is designed as a thermoplastic foam core, it can be shaped while simultaneously bonding the phenolic resin-glass fiber mixture of the first and second facing layers to the core. Therefore, the sandwich panel can be, for example, a simply curved or multiply curved sandwich panel. A sandwich panel is considered multiply curved when it is curved in two or more dimensions.

[0013] In one embodiment, the first top layer and / or the second top layer each contain a single layer of the phenolic resin-glass fiber mixture.

[0014] When using a thermoplastic foam core, it may be sufficient for the first cover layer to contain a single layer of the aforementioned phenolic resin-glass fiber mixture, because the foam core has a comparatively large contact area with this cover layer (for example, compared to honeycomb cores). Although the first cover layer contains only a single layer, its outer surface is very homogeneous and even.

[0015] In another embodiment, the first cover layer and the second cover layer completely surround the core layer.

[0016] This means that the first and second cover layers together, and not necessarily each individually, completely surround the core layer. Thus, the core layer is completely covered by at least one cover layer, even at its edges or on all its surfaces. Preferably, the first and second cover layers overlap. In another embodiment, their edges abut each other. Preferably, the cover layers completely cover every surface of the core layer.

[0017] In another embodiment, the core layer has a circumferential side surface, wherein the circumferential side surface is covered by the first cover layer or the second cover layer.

[0018] In another embodiment, the sandwich panel has at least one load application point.

[0019] A load introduction point serves to connect the sandwich panel to an adjacent component or to attach a load to the sandwich panel. The load introduction point can, for example, extend from one face layer through the core layer to the other face layer.

[0020] In another embodiment, the sandwich panel is a multiply curved sandwich panel.

[0021] This geometric shape is achieved in particular through the use of the thermoplastic foam core in conjunction with the phenolic resin-glass fiber top layer and offers a high quality of the outer surfaces.

[0022] According to another aspect, a component for the interior of a vehicle is specified. The component consists of, or has, a sandwich panel as described herein. The component is a spatially curved component.

[0023] The sandwich panel described here is particularly suitable for the production of simply or multiply curved components because, during the manufacturing process described below, it can be produced in virtually any spatially curved shape. This is primarily due to the fact that the core layer is a thermoplastic foam core that can be deformed under the influence of temperature and simultaneously bonded to the first and second facing layers.

[0024] This component can be used for the interior of a vehicle, particularly an aircraft. The sandwich panel's construction allows for the production of a component with high specific mechanical strength and high-quality outer surface finish.

[0025] According to another aspect, a method for manufacturing a curved component is specified. The method comprises the following steps: In a first step, a core layer made of a thermoplastic foam core is arranged between a first cover layer and a second cover layer; in a second step, a temperature is applied to the first cover layer, the second cover layer and the core layer; in a third step, a shaping pressure is applied to the first cover layer and / or the second cover layer to bring the first cover layer, the second cover layer and the core layer into a predetermined shape; in a fourth step, the component is cured.

[0026] This process is used to manufacture a sandwich panel as described herein. Steps of the manufacturing process have already been described and explained in detail in connection with the sandwich panel. These steps and details will not be repeated here. Instead, reference is made to the description of the sandwich panel.

[0027] The component is manufactured, for example, using a so-called hot pressing process. This process allows for the production of one- or multi-dimensionally curved sandwich components. The core layer, made of thermoplastic foam, exerts a large-area pressure from the inside onto the two outer layers, resulting in a homogeneous, high-quality outer surface. When the forming pressure is applied to the first and / or second outer layer in the third step, the thermoplastic foam core presses the two outer layers against the tool providing the pressure. This contributes to the finished sandwich panel having a homogeneous outer surface that largely corresponds to the surface structure of the tool's pressure-exerting surfaces. Because a foam core is used as the core layer, homogeneous properties are achieved throughout the core of the component with regard to its mechanical resistance and load-bearing capacity.

[0028] In one embodiment, the second step and the third step are performed simultaneously.

[0029] This means that the applied temperature puts the thermoplastic foam core in a state where it allows for plastic deformation. The forming pressure applied at this time forces the outer layers, along with the core layer, into the desired shape and bonds them together. When the sandwich panel cools in this state, it retains its shape.

[0030] In a further embodiment, in the third step a normal force is applied to the first cover layer and / or the second cover layer, whereby the first cover layer is pressed against a first surface of the core layer and / or the second cover layer is pressed against a second surface of the core layer opposite the first surface. In the third step a lateral force is applied to the first cover layer and / or the second cover layer, whereby the first cover layer and / or the second cover layer is pressed against a side face of the core layer.

[0031] Thus, the core layer is completely surrounded by the two outer layers, and no edge areas susceptible to mechanical stress and wear are created.

[0032] This construction may require that the cover layers extend beyond the edges of the core layer in a non-curved state, so that this part of the cover layers extending beyond the edges of the core layer can be folded over onto the side surface, pressed against it, and thus joined.

[0033] In one embodiment, the temperature in the second step is in a temperature range between 120 °C and 150 °C, and in particular, the temperature in the second step is between 130 °C and 140 °C. Brief description of the drawings

[0034] Some details are described below with reference to the accompanying drawings. The illustrations are schematic and not to scale. Identical reference symbols refer to identical or similar elements. They show: Fig. 1 a schematic sectional view of a sandwich panel; Fig. 2 a schematic sectional view of a sandwich panel; Fig. 3 a schematic representation of a component consisting of a sandwich panel according to Fig. 1 or Fig. 2; Fig. 4 A schematic representation of the steps of a process for manufacturing a curved component. Detailed description

[0035] Fig. Figure 1 shows the basic structure of a sandwich panel 100 in a profile view or side section view. The sandwich panel 100 has a first facing layer 110 and a second facing layer 120. A core layer 130 is arranged between the first facing layer 110 and the second facing layer 120. The core layer 130 is designed as a thermoplastic foam core. The first facing layer 110 and the second facing layer 120 are made of a laminate, for example, fiberglass braid impregnated with phenolic resin. The facing layers 110 and 120 are bonded to the core layer 130 to form the sandwich panel 100.

[0036] Fig. Figure 2 shows the schematic structure of a sandwich panel 100 with a core layer 130, which is completely surrounded by the first cover layer 110 and the second cover layer 120.

[0037] The core layer 130 has a first surface 131 and a second surface 132. The first surface 131 faces the second surface 132. The first surface 131 and the second surface 132 form the top and bottom surfaces of the sandwich panel 100.

[0038] The core layer 130 also has a circumferential side surface 135.

[0039] The first cover layer 110 rests on the first surface 131, and the second cover layer 120 rests on the second surface 132. It is easily seen from the illustration that both the first cover layer 110 and the second cover layer 120 extend laterally beyond the first surface 131 and the second surface 132, respectively. Thus, the first cover layer 110 and the second cover layer 120 can be pressed laterally onto the surrounding side surface 135.

[0040] A normal force F1, which is shown in the representation of the Fig. When force 2 acts on the first cover layer 110, the cover layer presses against the core layer. For example, in a tool (not shown), the normal force is applied to one of the two cover layers and the entire sandwich panel is pressed against a counterpart, thereby creating a compressive force that presses both cover layers 110, 120 onto the respective surfaces 131, 132 of the core layer and bonds them together.

[0041] A lateral force F2 pushes the protruding length of the cover layers towards the side surface 135 so that the core layer is completely surrounded by the cover layer material.

[0042] In the example of the Fig. 2. The cover layers 110 and 120 do not overlap, but are in contact area 138, in the manner of a butt joint. Adhesive can also be used in this contact area 138, which melts under the influence of temperature (for example, in the third step of the process) and bonds the cover layers 110 and 120 to each other and to the core layer 130, in particular to the side surface 135.

[0043] In the contact area 138, the cover layers 110 and 120 can also overlap to form a stronger bond. For example, the resulting overlap area between the first cover layer 110 and the second cover layer 120 has a lower height than the height of the core layer 130, where the height of the core layer 130 is defined as the distance between the first surface 131 and the second surface 132.

[0044] Although the core layer 130 in the example shown has a rectangular cross-section, it should be noted that the core layer can also have a different cross-sectional shape, for example with rounded corners and / or edges.

[0045] Last but not least, it should also be noted that the sandwich panel 100 may in particular be a multiply curved sandwich panel, even if this is described in the Fig. 1 and Fig. 2 is represented as a flat plate. The representations in the Fig. 1 and Fig. Section 2 serves the purpose of describing the structural composition of the sandwich panel 100 with the two outer layers 110, 120 and the core layer 130.

[0046] Fig. Figure 3 shows a component 200, which consists of a sandwich panel 100, as used in the Fig. 1 and Fig. The component shown in Figure 2 is manufactured. For example, component 200 is a multi-plane curved interior panel for an aircraft, such as a flap for a luggage compartment in an airplane.

[0047] Component 200 has several load application points 140. The load application points 140 are arranged such that component 200 can be mounted in the desired position and moved within it as required. It is also conceivable that component 200 has a load application point 140 for attaching a handle or a closure. For this purpose, component 200 may have a lateral recess 202.

[0048] Both the core layer 130 and the first cover layer 110 and the second cover layer 120 can be formed into the desired shape before these three components are joined together to form the sandwich panel 100. This means that the recess 202 is produced in both the core layer 130 and the two cover layers 110 and 120, and then the cover layers are joined to the core layer.

[0049] Fig. Figure 4 schematically shows a method 300 for manufacturing a curved component 200, as described in Fig. 3 is shown and from one in Fig. 1 and Fig.Figure 2 shows a sandwich panel. The method comprises the following steps: 1. Arranging a core layer 130 made of a thermoplastic foam core between a first cover layer 110 and a second cover layer 120 in a first step 310; 2. Applying a temperature to the first cover layer 110, the second cover layer 120 and the core layer 130 in a second step 320; 3. Applying a shaping pressure F1, F2 to the first cover layer 110 and / or the second cover layer 120 in a third step 330 to bring the first cover layer 110, the second cover layer 120 and the core layer 130 into a predetermined shape; 4. Curing the component 200 in a fourth step 340.

[0050] The steps of the process are carried out, for example, in and with a tool, which is not shown separately here. The tool has forming surfaces onto which first a cover layer, then the core layer, and then the second cover layer are placed one on top of the other in the intended relative position. In this position, the components of the sandwich panel are exposed to a predetermined temperature to achieve formability of the core layer. One forming surface then moves relative to the second forming surface, so that the sandwich panel components placed on it are brought into the desired shape between the two forming surfaces. The temperature can then be reduced to allow the component to harden.

[0051] This process enables the production of multi-curved, lightweight sandwich components that meet the following requirements, which are presented here in relation to other material combinations. These include low costs, low weight of the manufactured component, high specific mechanical strength, and high-quality outer surfaces. Because the core layer consists of a thermoplastic foam core, it presses the face sheets against the forming surfaces of the tool over a large area, resulting in a uniform surface structure of the sandwich component. This is because the thermoplastic foam core is typically produced with blowing agents, creating a certain internal pressure within the foam core and resulting in a significantly larger contact area between the foam core and the face sheets compared to, for example, the use of a honeycomb core.Because the foam core lies evenly and over a large area against the outer layers, it does not introduce any unwanted contours into the outer layers. Therefore, with this construction, it is sufficient for each outer layer to consist of a single layer of phenolic resin-glass fiber mixture.

[0052] Curved components manufactured using this sandwich construction method can be used, for example, as interior paneling in aircraft with high design requirements.

[0053] When using thermoplastic foam cores, all design features can be achieved by thermally deforming the foam core during the hot pressing process for manufacturing the sandwich component with phenolic resin-glass fiber facing sheets. This eliminates the need for prior thermal deformation or milling of the foam core in a separate step. Edge radii, cutouts, or changes in wall thickness are achieved through viscoplastic deformation (pressing) of the foam within a specific temperature range. At precisely controlled process temperatures, the foam core generates internal pressure, resulting in excellent surface finishes on the cured component.

[0054] The component produced using this method, based on the sandwich panel described above, can be manufactured cost-effectively and supplied as a multi-curved component. Because each face sheet consists of a single layer of phenolic resin-glass fiber composite, the weight can be reduced. Since the side surface of the core layer is also covered by the face sheets, edge finishing is unnecessary, and the mechanical strength in this area is significantly increased. Due to the use of thermoplastic foam core material, the core is characterized by homogeneous mechanical properties such as strength and load-bearing capacity in different directions.

[0055] It should also be noted that "comprehensive" or "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps of other embodiments described above. Reference numerals in the claims are not to be considered as limitations. Reference symbol list 100 sandwich panels 110 first top layer 120 second top layer 130 core layer 131 first surface 132 second surface 135 mm² side surface 138 Contact area 140 Load introduction point 200 components 202 lateral recess 300 procedures 310 first step 320 second step 330 third step 340 fourth step F1 Normal force F2 Lateral force

Claims

[1] Sandwich panel (100), comprising: a first cover layer (110); a second cover layer (120); a core layer (130); wherein the core layer (130) is arranged between the first cover layer (110) and the second cover layer (120) and is connected to the first cover layer (110) and the second cover layer (120); wherein the core layer (130) is a thermoplastic foam core; wherein the first cover layer (110) contains a phenolic resin-glass fiber mixture; and wherein the second cover layer (120) contains a phenolic resin-glass fiber mixture. [2] Sandwich panel (100) according to claim 1, wherein the first cover layer (110) and / or the second cover layer (120) each contain a single layer of the phenolic resin-glass fiber mixture. [3] Sandwich panel (100) according to claim 1 or 2, the first cover layer (110) and the second cover layer (120) completely surround the core layer (130). [4] Sandwich panel (100) according to claim 3, wherein the core layer (130) has a circumferential side surface (135); wherein the circumferential side surface (135) is covered by the first cover layer (110) or the second cover layer (120). [5] Sandwich panel (100) according to one of the preceding claims, wherein the sandwich panel (100) has at least one load introduction point (140). [6] Sandwich panel (100) according to one of the preceding claims, wherein the sandwich panel (100) is a multi-curved sandwich panel. [7] Component (200) for an interior fitting in a vehicle, wherein the component (200) consists of a sandwich panel (100) according to one of claims 1 to 6; wherein the component (200) is a spatially curved component. [8] Method (300) for producing a curved component (200), the method comprising the following steps: Arranging a core layer (130) made of a thermoplastic foam core between a first cover layer (110) and a second cover layer (120) in a first step (310); Applying a temperature to the first cover layer (110), the second cover layer (120) and the core layer (130) in a second step (320); Applying a shaping compressive force to the first cover layer (110) and / or the second cover layer (120) in a third step (330) in order to bring the first cover layer (110), the second cover layer (120) and the core layer (130) into a predetermined shape; Curing the component (200) in a fourth step (340). [9] The method (300) of claim 8, wherein the second step (320) and the third step (330) are performed simultaneously. [10] Method (300) according to claim 8 or 9, wherein in the third step (330) a normal force (F1) is applied to the first cover layer (110) and / or the second cover layer (120), whereby the first cover layer (110) is pressed against a first surface (131) of the core layer (130) and / or the second cover layer (120) is pressed against a second surface (132) of the core layer (130) opposite the first surface (131); wherein in the third step (330) a lateral force (F2) is applied to the first cover layer (110) and / or the second cover layer (120), whereby the first cover layer (110) and / or the second cover layer (120) is pressed against a side surface (135) of the core layer (130).

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