DE102023119489A1 - Sandwich panel, component for an interior fitting in a vehicle, and method for producing a curved component - Google Patents

Abstract

A sandwich panel (100) has a first cover layer (110), a second cover layer (120) and a core layer (130). The core layer (130) is arranged between the two cover layers (110, 120) and is connected to both cover layers. The core layer (130) is a thermoplastic foam core. The first cover layer (110) and the second cover layer (120) each contain a phenolic resin-glass fiber mixture. In addition, a method for producing such a sandwich panel is described.

Description

technical field

The present description relates generally to lightweight construction technology, and in particular to the construction of sandwich panels and a method for producing sandwich panels. Furthermore, in particular, the description relates to a component consisting of or comprising such a sandwich panel and a method for producing a curved component from a sandwich panel.

Technical Background

Sandwich panels are preferred for use in lightweight construction because they are comparatively light, but have high specific mechanical strength and resistance to external loads. Sandwich panels have two cover layers and a core layer in between. Due to their construction, sandwich panels are usually manufactured as flat or level elements. Sandwich panels are often manufactured or cut to a specified size or shape, so that they can then be installed in the intended application environment with this size or shape.

Description

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.

This object is achieved by the subject matter of the independent claims. Further embodiments emerge from the dependent claims and from the following description.

According to a first aspect, a sandwich panel has a first cover layer, a second cover layer and a core layer. The core layer is arranged between the first cover layer and the second cover layer and is connected to the first cover layer and the second cover layer. The core layer is a thermoplastic foam core. The first cover layer and the second cover layer each contain a phenolic resin-glass fiber mixture.

A sandwich panel generally consists of two cover layers and a core or core layer arranged between the two cover layers.

Each cover layer has at least one layer of the cover layer material. The cover layers are connected to the core layer on opposite surfaces of the core layer, for example glued. The cover layers 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 cover layers. For example, the cover layers are made of impregnated fiber mesh (in a woven or parallel structure or a combination thereof). Each layer of a cover layer can, for example, contain a glass fiber layer. The fibers can be incorporated into a thermosetting matrix and thus form a layer of the cover layer. For example, the fiber mesh is impregnated in phenolic resin.

The core layer consists of a material with a significantly lower density than the cover layers. The density of the core layer is based on its mass and its volume when installed in the sandwich panel. In order to achieve this comparatively low density, the core layer typically contains cavities. In this case, the core layer contains a thermoplastic foam core.

Foam cores are made 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 has a high mechanical strength and is therefore well suited to absorbing pressure loads. In addition, these foams have a high specific shear strength and specific shear elongation at break.

The stable cover layers distribute compressive loads perpendicular to the surface normal of the sandwich panel evenly over the light core layer, which means that the core layer is able to absorb the compressive loads. In addition, shear loads when the sandwich panels bend are well absorbed by the light material of the core layer. The cover layers, on the other hand, withstand tensile and compressive loads in the plane of the panel.

This structure results in excellent stability of the sandwich panels while keeping them lightweight.

The structure of the sandwich panel described here makes it possible in particular for the sandwich panel to be provided not only as a flat or level component, but to take on almost any geometric shape. Because If the core layer is designed as a thermoplastic foam core, the thermoplastic foam core can be formed and at the same time the phenol resin-glass fiber mixture of the first cover layer and the second cover layer can be glued to the core layer. In this respect, the sandwich panel is, for example, a single or multiple curved sandwich panel. A sandwich panel is multiple curved if it is curved in two or more dimensions.

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

When using a thermoplastic foam core, it may be sufficient if the first cover layer contains a single layer of the phenolic resin-glass fiber mixture mentioned, 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 only contains a single layer, the outer surface of the cover layer is very homogeneous and even.

In a further embodiment, the first cover layer and the second cover layer completely surround the core layer.

This means that the first cover layer and the second cover layer completely surround the core layer together and not necessarily individually. The core layer is therefore completely covered by at least one cover layer, for example, in an edge area or on all of its side surfaces. The first cover layer and the second cover layer preferably overlap. In another embodiment, their edges border on one another. The cover layers preferably completely cover every surface of the core layer.

In a further 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.

In a further embodiment, the sandwich panel has at least one load introduction point.

A load introduction point is used 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 cover layer through the core layer to the other cover layer.

In a further embodiment, the sandwich panel is a multi-curved sandwich panel.

This geometric shape is achieved in particular by the use of the thermoplastic foam core in combination with the phenolic resin-glass fiber cover layer and offers a high quality of the external surfaces.

According to a further aspect, a component for interior fittings in a vehicle is specified. The component consists of or has a sandwich panel as described herein. The component is a spatially curved component.

The sandwich panel described here is particularly suitable for the production of single or multiple curved components because the sandwich panel can be produced in almost any spatially curved shape during the production process described below. This is particularly the case because the core layer is a thermoplastic foam core which can be deformed under the influence of temperature and simultaneously connected to the first cover layer and the second cover layer.

The component can be used for the interior fittings in a vehicle. The vehicle can in particular be an aircraft. The structure of the sandwich panel makes it possible to provide a corresponding component with high specific mechanical strength and high demands on the quality of the outer surface of the component.

• Anordnen einer Kernschicht aus einem thermoplastischen Schaumkern zwischen einer ersten Deckschicht und einer zweiten Deckschicht in einem ersten Schritt; Anbringen einer Temperatur auf die erste Deckschicht, die zweite Deckschicht und die Kernschicht in einem zweiten Schritt; Aufbringen einer formgebenden Druckkraft auf die erste Deckschicht und/oder die zweite Deckschicht in einem dritten Schritt, um die erste Deckschicht, die zweite Deckschicht und die Kernschicht in eine vorgegebene Form zu bringen; Aushärten des Bauteils in einem vierten Schritt.

According to a further aspect, a method for producing a curved component is provided. The method comprises the following steps:

• Arranging a core layer made of a thermoplastic foam core between a first cover layer and a second cover layer in a first step; applying a temperature to the first cover layer, the second cover layer and the core layer in a second step; applying a shaping compressive force to the first cover layer and/or the second cover layer in a third step in order to bring the first cover layer, the second cover layer and the core layer into a predetermined shape; curing the component in a fourth step.

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

The component is manufactured, for example, in a so-called hot-pressing process. This makes it possible to produce one- or multi-dimensionally curved sandwich components. The core layer made of the thermoplastic foam core exerts large-area pressure from the inside on the two cover layers, so that a homogeneous outer surface of high quality is achieved. When the shaping pressure force is applied to the first cover layer and/or the second cover layer in the third step, the thermoplastic foam core presses the two cover layers against the tool that provides the pressure force, which helps to ensure that the manufactured sandwich panel has a homogeneous outer surface that largely corresponds to the surface structure of the surfaces of the tool that exert the pressure force. Because a foam core is used as the core layer, homogeneous properties are achieved in the core with regard to the mechanical resistance and load-bearing capacity of the component.

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

This means that the temperature applied puts the thermoplastic foam core in a state in which it allows plastic deformation. The shaping pressure applied at this time causes the cover layers to be brought into the desired shape together with the core layer and bonded together. When the sandwich panel cools down in this state, it retains its shape.

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 surface of the core layer.

Thus, the core layer is completely surrounded by the two cover layers and there are no edge areas that are susceptible to mechanical stress and wear.

This construction may require that the cover layers protrude beyond the edges of the core layer in a non-curved state so that that part of the cover layers protruding beyond the edges of the core layer can be folded over onto the side surface and pressed against and bonded to it.

In one embodiment, the temperature in the second step is in a temperature range between 120 °C and 150 °C, more particularly the temperature in the second step is between 130 °C and 140 °C.

Short description of the drawings

• 1 eine schematische Schnittansicht einer Sandwichplatte;
• 2 eine schematische Schnittansicht einer Sandwichplatte;
• 3 eine schematische Darstellung eines Bauteils bestehend aus einer Sandwichplatte gemäß 1 oder 2;
• 4 eine schematische Darstellung der Schritte eines Verfahrens zum Herstellen eines gekrümmten Bauteils.

Some details are described in more detail below using the attached drawings. The illustrations are schematic and not to scale. The same reference numerals refer to the same or similar elements. They show:

• 1 a schematic sectional view of a sandwich panel;
• 2 a schematic sectional view of a sandwich panel;
• 3 a schematic representation of a component consisting of a sandwich panel according to 1 or 2 ;
• 4 a schematic representation of the steps of a method for producing a curved component.

Detailed description

1 shows the basic structure of a sandwich panel 100 in a profile view or side sectional view. The sandwich panel 100 has a first cover layer 110 and a second cover layer 120. A core layer 130 is arranged between the first cover layer 110 and the second cover layer 120. The core layer 130 is designed as a thermoplastic foam core. The first cover layer 110 and the second cover layer 120 are made of a laminate, for example glass fiber mesh impregnated with phenolic resin. The cover layers 110, 120 are glued to the core layer 130 to form the sandwich panel 100.

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.

The core layer 130 has a first surface 131 and a second surface 132. The first surface 131 is opposite the second surface 132. The first surface 131 and the second surface 132 form the top and bottom of the sandwich panel 100.

The core layer 130 further has a circumferential side surface 135.

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 easy to see from the illustration that both the first cover layer 110 and the second cover layer 120 protrude laterally beyond the first surface 131 and the second surface 132, respectively. The first cover layer 110 and the second cover layer 120 can thus be pressed laterally onto the circumferential side surface 135.

A normal force F1, which in the representation of the 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 exerted on one of the two cover layers and the entire sandwich panel is pressed against a counterpart, whereby a compressive force presses both cover layers 110, 120 onto the respective surfaces 131, 132 of the core layer and bonds them together.

A lateral force F2 presses 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.

In the example of 2 the cover layers 110, 120 do not overlap, but lie against one another in a contact area 138, in the manner of a butt joint. In this contact area 138, adhesive can also be used, which melts under the influence of temperature (for example in the third step of the method) and bonds the cover layers 110, 120 to one another and to the core layer 130, in particular to the side surface 135.

In the contact region 138, the cover layers 110, 120 can also overlap in order to form a stronger connection with one another. For example, the resulting overlap region between the first cover layer 110 and the second cover layer 120 has a lower height than the height of the core layer 130, wherein the height of the core layer 130 is defined as the distance between the first surface 131 and the second surface 132.

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

Last but not least, it should also be noted that the sandwich panel 100 can in particular be a multiply curved sandwich panel, even if this is in the 1 and 2 is shown as a flat plate. The representations in the 1 and 2 serves the purpose of describing the structural design of the sandwich panel 100 with the two cover layers 110, 120 and the core layer 130.

3 shows a component 200 which consists of a sandwich panel 100 as shown in the 1 and 2 shown. The component 200 is, for example, an interior panel of an aircraft curved in several planes, for example a flap for a luggage compartment in an aircraft.

The component 200 has several load introduction points 140. The load introduction points 140 are arranged so that the component 200 can be mounted in the desired position and moved therein as desired. It is also conceivable that a load introduction point 140 is provided on the component 200 for attaching a handle or a closure. For this purpose, a lateral recess 202 can be provided on the component 200.

Both the core layer 130 and the first cover layer 110 and the second cover layer 120 can be brought into the desired shape before these three components are connected to one another in the process to form the sandwich panel 100. This means that the recess 202 is made in both the core layer 130 and the two cover layers 110, 120 and then the cover layers are connected to the core layer.

4 shows schematically a method 300 for producing a curved component 200, as in 3 shown and consists of a 1 and 2 shown sandwich panel. The method comprises 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 pressure force F1, F2 to the first cover layer 110 and/or the second cover layer 120 in a third step 330 in order to shape 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.

The steps of the method are carried out, for example, in and with a tool, which is not shown separately here. The tool has shaping surfaces on 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 in order to make the core layer malleable. A shaping surface then moves towards the second shaping surface relative to it, so that the components of the sandwich panel placed on it are brought into the desired shape between the two shaping surfaces. The temperature can now be reduced so that the component hardens.

This process can be used to produce multi-curved sandwich components in a lightweight design and meet the following requirements, which are presented in this context relative to other material combinations. These include low costs, the low weight of the manufactured component, the high specific mechanical strengths and a high quality of the external surfaces of the component. Precisely because the core layer consists of a thermoplastic foam core, the core layer presses the cover layers against the shaping surfaces of the tool over a large area, thereby achieving a uniform surface structure of the sandwich component. This is because the thermoplastic foam core is usually produced with blowing agents, a certain internal pressure is created in the foam core beforehand and the contact area between the foam core and cover layers is significantly larger than when using a honeycomb core, for example. Because the foam core lies evenly and over a large area against the cover layers, it does not introduce any undesirable contours into the cover layers. With this structure, it is therefore sufficient if the respective cover layers consist of a single layer of phenolic resin-glass fiber mixture.

Curved sandwich components manufactured using this process can be used, for example, as paneling in the interior of aircraft with high design requirements.

When using thermoplastic foam cores, all design features can be achieved by thermally deforming the foam core during the hot-pressing process to produce the sandwich component with phenolic resin-glass fiber cover layers. The foam core does not have to be thermally formed in a separate step or machined by milling. Edge radii, cutouts or changes in wall thickness are achieved by viscoplastic deformation (pressing) of the foam within a certain temperature range. At coordinated process temperatures, the foam core generates an internal pressure that leads to very good external surfaces of the cured component.

The component produced using this method and based on a sandwich panel as described above can be manufactured inexpensively and provided as a multi-curved component. Because each cover layer consists of a single layer of phenolic resin-glass fiber mixture, the weight can be reduced. Because the side surface of the core layer is also covered by the cover layers, post-processing of the edges is not necessary and the mechanical resistance 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 loads in different directions.

In addition, it should be noted that "comprising" or "having" does not exclude other elements or steps and "a" or "an" does not exclude a plurality. It should also be noted that features or steps that have been described with reference to one of the above embodiments can also be used in combination with other features or steps of other embodiments described above. Reference signs in the claims are not to be regarded as a limitation.

list of reference symbols

100

sandwich panel

110

first top layer

120

second top layer

130

core layer

131

first surface

132

second surface

135

side surface

138

contact area

140

load introduction point

200

component

202

lateral recess

300

Proceedings

310

first step

320

second step

330

third step

340

fourth step

F1

normal force

F2

lateral force

Claims (10)

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. Sandwich panel (100) after 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. Sandwich panel (100) after claim 1 or 2 , the first cover layer (110) and the second cover layer (120) completely surround the core layer (130). Sandwich panel (100) after 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). Sandwich panel (100) according to one of the preceding claims, wherein the sandwich panel (100) has at least one load introduction point (140). Sandwich panel (100) according to one of the preceding claims, wherein the sandwich panel (100) is a multi-curved sandwich panel. Component (200) for an interior fitting in a vehicle, wherein the component (200) consists of a sandwich panel (100) according to one of the Claims 1 until 6 wherein the component (200) is a spatially curved component. 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 pressure 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). Procedure (300) according to claim 8 , wherein the second step (320) and the third step (330) are carried out simultaneously. Procedure (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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