METHOD FOR PRODUCING A SANDWICH PANEL COMPRISING A REINFORCED FOAM CORE

Abstract

A method for producing a sandwich panel with a reinforced foam core includes inserting rod-shaped, thermoplastic reinforcing elements into a thermoplastic foam material such that the reinforcing elements extend through the foam material. End regions of the reinforcing elements project out of the foam material. The foam material is thermoformed to form a reinforced foam core, wherein the end regions of the reinforcing elements are integrally formed by applying temperature and pressure to the cover surfaces of the foam material and are bonded to the foam material in a fused connection. A thermoplastic cover layer is laminated on either side by applying temperature and pressure to the reinforced foam core on the cover surfaces of the foam material in order to form the sandwich panel, wherein the cover layers are bonded to the reinforced foam core in a fused connection.

Claims

1. A method for producing a sandwich panel comprising a reinforced foam core, comprising: inserting a plurality of rod-shaped, thermoplastic reinforcing elements into a thermoplastic foam material such that the reinforcing elements extend from a first cover surface of the foam material, through the foam material, to a second cover surface of the foam material, wherein end regions of the reinforcing elements project out of the first cover surface and the second cover surface; thermoforming the foam material comprising the reinforcing elements to form a reinforced foam core, wherein the end regions of the reinforcing elements are integrally formed by applying temperature and pressure to the cover surfaces of the foam material and are bonded to the foam material in a fused connection; and laminating a thermoplastic cover layer on either side by applying temperature and pressure to the reinforced foam core on the cover surfaces of the foam material in order to form the sandwich panel, wherein the cover layers are bonded to the reinforced foam core in a fused connection.

2. The method of claim 1, further comprising: forming a plurality of through-holes in the foam material which extend from the first cover surface of the foam material to the second cover surface of the foam material, wherein the reinforcing elements are inserted into the through-holes.

3. The method of claim 2, wherein the through-holes are formed by melting the foam material.

4. The method of claim 3, wherein the foam material is melted using a laser.

5. The method of claim 1, wherein the reinforcing elements are pointed at least at one end region in each case.

6. The method of claim 5, wherein the through-holes are formed by perforating the foam material using the pointed end regions of the reinforcing elements.

7. The method of claim 1, wherein the end regions of the reinforcing elements project to an equal extent out of the first cover surface and the second cover surface.

8. The method of claim 1, wherein the reinforcing elements inserted into the foam material are secured in the foam material by a frictional connection.

9. The method of claim 1, wherein laminating thermoplastic cover layers onto either side of the reinforced foam core facilitates the application of temperature and pressure for thermoforming.

10. The method of claim 1, wherein thermoforming on either side is carried out by a press.

11. The method of claim 1, wherein the laminating on either side is carried out by a press.

12. The method of claim 1, wherein at least one of the reinforcing elements, the foam material and the cover layers each contain a thermoplastic polymer.

13. The method of claim 12, wherein the reinforcing elements, the foam material and the cover layers each contain a same thermoplastic polymer.

14. The method of claim 12, wherein the reinforcing elements contain reinforcing fibers which are embedded in a relevant thermoplastic polymer.

15. The method of claim 12, wherein the cover layers contain reinforcing fibers which are embedded in a relevant thermoplastic polymer.

16. The method of claim 12, wherein a relevant thermoplastic polymer is selected from the group consisting of acrylonitrile butadiene styrene, polyamide, polybutylene terephthalate, polycarbonate, polyether ether ketone, polyetherimide, polyethersulfone, polyethylene terephthalate, polypropylene, polyphenylene sulfide, polyphenylsulfone and polysulfone.

17. A sandwich panel produced using a method comprising: inserting a plurality of rod-shaped, thermoplastic reinforcing elements into a thermoplastic foam material such that the reinforcing elements extend from a first cover surface of the foam material, through the foam material, to a second cover surface of the foam material, wherein end regions of the reinforcing elements project out of the first cover surface and the second cover surface; thermoforming the foam material comprising the reinforcing elements to form a reinforced foam core, wherein the end regions of the reinforcing elements are integrally formed by applying temperature and pressure to the cover surfaces of the foam material and are bonded to the foam material in a fused connection; and laminating a thermoplastic cover layer on either side by applying temperature and pressure to the reinforced foam core on the cover surfaces of the foam material in order to form the sandwich panel, wherein the cover layers are bonded to the reinforced foam core in a fused connection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the following, the present disclosure is described in greater detail with reference to the embodiments set out in the schematic, example drawings, in which:

[0025] FIGS. 1a to 1c are schematic cross-sectional views of a sandwich panel comprising a reinforced foam core during production using a method according to an embodiment of the disclosure herein; and

[0026] FIG. 2 is a schematic flow chart of a method as used in FIG. 1a to 1c.

[0027] The accompanying drawings are intended to provide further understanding of the embodiments of the disclosure herein. They illustrate embodiments and are used in conjunction with the description to clarify the principles and concepts of the disclosure herein. Other embodiments and many of the mentioned advantages will become apparent with reference to the drawings. The elements of the drawings are not necessarily shown true to scale relative to one another.

[0028] In the figures of the drawings, identical, functionally identical and identically operating elements, features and components have been respectively provided with the same reference numerals, unless indicated otherwise.

DETAILED DESCRIPTION

[0029] FIG. 1a through 1c are schematic cross-sectional views of a sandwich panel 10 comprising a reinforced foam core 5 during production using a method M according to an embodiment of the disclosure herein. FIG. 2 in general shows a schematic flow chart of a method M of this type for producing a sandwich panel 10 of this type.

[0030] The sandwich panel 10 essentially comprises a reinforced foam core 5, which has a thermoplastic foam material 2 having a first cover surface 3a and a second cover surface 3b, the foam material 2 being penetrated by a plurality of rod-shaped thermoplastic reinforcing elements 1 in the thickness direction, i.e. from the first cover surface 3a to the second cover surface 3b. The reinforced foam core 5 is connected to the cover surfaces 3a, 3b on either side by one thermoplastic cover layer 6 in each case. A sandwich panel 10 of this type may for example be used for cladding a wall or ceiling of a passenger cabin of an aircraft. Panels of this type can also be used as floor plates, cover plates, etc.

[0031] The reinforcing elements 1, the foam material 2 and/or the cover layers 6 may each contain one or more thermoplastic polymers. In this case, thermoplastic polymers may be the same or different. In particular, the foam material 2 may consist completely or substantially comprise a thermoplastic polymer of this type. In principle, the reinforcing elements 1 and the cover layers 6 may consist completely or substantially comprise a thermoplastic polymer of this type. Depending on the use, the relevant thermoplastic polymer may be selected from the group consisting of ABS (acrylonitrile butadiene styrene), PA (polyamide), PBT (polybutylene terephthalate), PC (polycarbonate), PEEK (polyether ether ketone), PEI (polyetherimide), PES (polyethersulfone), PET (polyethylene terephthalate), PP (polypropylene), PPS (polyphenylene sulfide), PPSU (polyphenylsulfone) and PSU (polysulfone) or the like. Specifically in the field of aviation and aerospace, thermoplastic materials such as PEEK, PEI, PES, PPS, PPSU or PSU are advantageous.

[0032] Furthermore, the reinforcing elements 1 and/or the cover layers 6 may however also contain reinforcing fibers which are embedded in the relevant thermoplastic polymer. Reinforcing fibers may for example be carbon fibers, glass fibers, aramid fibers or the like. A rod-shaped reinforcing element 1 may, for example, accordingly comprise a plurality of reinforcing fibers which are embedded into a matrix made of thermoplastic polymer, e.g. carbon fibers embedded in a matrix made of PEEK or the like. A reinforcing element 1 of this type accordingly forms a kind of rigid pin. Thermoplastic polymer of the pin can be melted by the effects of temperature. In principle, different designs of the pins or the reinforcing elements 1 may be provided, and may be combined with one another in a sandwich panel 10. For example, variants with or without fiber reinforcement, with or without orientation thereof and with various fiber lengths from short to continuous are provided. The plastics matrix of the reinforcing elements 1 may be made of the same or a different plastics material as the foam material 2, it being necessary for the plastics materials used to be mixable at the molecular level in order to form a bond. The reinforcing elements 1 may have a circular cross section, or another cross section. The reinforcing elements 1 are inserted at an angle of 0° merely by way of example; however, other angles are also possible which may be advantageous for certain load directions. Reinforcing elements 1 may in particular be inserted at various different angles, e.g. different insertion angles of between 0° and 75°.

[0033] The method M includes, at M1, inserting a plurality of rod-shaped, thermoplastic reinforcing elements 1 into a thermoplastic foam material 2 such that the reinforcing elements 1 extend from a first cover surface 3a of the foam material 2, through the foam material 2, to a second cover surface 3b of the foam material 2. Here, end regions 4 of the reinforcing elements 1 project out of the first cover surface 3a and the second cover surface 3b. Prior to inserting the rod-shaped, thermoplastic reinforcing elements, the method M may optionally include, at M0, forming a plurality of through-holes 6 in the foam material 2 (not shown in FIG. 1a through 1c) which extend from the first cover surface 3a of the foam material 2 to the second cover surface 3b of the foam material 2. In this case, the reinforcing elements 1 can simply be inserted into the through-holes 6. Here, the through-holes 6 may for example be made by drilling or melting the foam material 2, e.g. using a laser, a particle beam or another suitable auxiliary structure or approach by which energy can be generated in a directed manner in order to melt holes. Alternatively or additionally, it may however also be provided that through-holes 6 are made by perforating the foam material 2 using the reinforcing elements 1. For this purpose, the reinforcing elements 1 may for example have pointed end regions 4, which then accordingly function as nails or drill heads. Following these method steps, the reinforcing elements 1 inserted into the foam material 2 can be temporarily secured in the foam material 2 by a frictional connection, for example. Alternatively or additionally, reinforcing elements 1 may however likewise be held in position by an external device or another auxiliary structure or approach. For example, the reinforcing elements 1 can be inserted into the foam material 2 using a machine and can be held therein by this same machine.

[0034] The method M further includes, at M2, thermoforming the foam material 2 comprising the reinforcing elements 1 to form a reinforced foam core 5. Here, the end regions 4 of the reinforcing elements 1 are integrally formed by applying temperature and pressure to the cover surfaces 3a, 3b of the foam material 2 and are bonded to the foam material 2 in a fused connection, i.e. the method involves fusing the reinforcing elements 1 and the foam material 2. Here, a molding tool may for example be used in order to bring the foam material 2 together with the reinforcing elements 1 into a desired shape. The method M further includes, at M3, laminating a thermoplastic cover layer 6 on either side by applying temperature and pressure to the reinforced foam core 5 on the cover surfaces 3a, b′ of the foam material 2 in order to form the sandwich panel 10. Here, the cover layers 6 are bonded to the reinforced foam core 5 in a fused connection, i.e. the method involves fusing the cover layers 6 and the reinforced foam core 5. Thermoforming and/or the laminating on either side can be carried out by a press 7. In particular, laminating thermoplastic cover layers 6 onto either side of the reinforced foam core 5 facilitates the application of temperature and pressure for thermoforming. FIGS. 1b and 1c show, by way of example, an embodiment of the method M in which both thermoforming (FIG. 1b) and the laminating (FIG. 1c) are carried out by a press 7 in separate steps. The press 7 applies pressure and temperature to the corresponding components (see arrows in FIGS. 1b and 1c). In principle, the two processes may however also be carried out in one method step by the press 7 applying temperature and pressure to the cover layers 6 such that when the press is pressed against the cover surfaces 3a, 3b of the foam material 2 comprising the reinforcing elements 1 inserted therein, sufficient thermal energy is transferred to the foam material 2 and the end regions 4 of the reinforcing elements 1, and therefore they are melted at least in the region of the surface. Here, the reinforcing elements 1 projecting out of the foam material 2 may be heated and reshaped, such that a kind of bead, comparable to a rivet, is formed on the end regions of the reinforcing elements (see FIG. 1b). To form a flat surface, this bead is then pressed into the foam material 2 and fused therewith.

[0035] Using the method according to the disclosure herein, sandwich panels 10 can thus be formed that have a reinforced foam core 5 made of thermoplastic polymers. Usually, it is only thermosetting foam materials that are used to produce sandwich panels, e.g. “tied foam core” methods or similar methods, in which dry fibers are inserted into a thermosetting foam material and are then infiltrated with a plastics matrix. Using the present disclosure, it is now possible to produce thermoplastic sandwich panels having mechanical properties that are comparable to thermosetting sandwich panels or sandwich panels having a honeycomb core. For example, the pressure resistance and shear resistance of the sandwich panels can be optimised by the reinforcing elements 1.

[0036] Furthermore, however, thermoplastic polymers used have many advantages; in particular, they can be formed into almost any shape very easily and with little complexity. By contrast, honeycomb structures can only be handled by machines with difficulty, and therefore they are often processed manually. At the same time, structures that are curved multiple times are very rarely produced in this case. Generally, it is extremely complex to produce honeycomb panels of this type. Sandwich structures comprising cores made of foamed polymers provide more cost-effective processing properties and a wider range of options for shaping. These structures can be brought into almost any conceivable shape. Foam materials made of thermoplastic polymers according to the present disclosure may also be deformed into any shape under the effects of pressure and temperature, and can be joined to thermoplastic cover layers in short cycle times. Therefore, the present methods provide for production of complex-shaped sandwich structures in short cycle times.

[0037] The methods and sandwich panels which have been described can be used in all sectors of the transport industry, for example for aircraft, road vehicles, for rail vehicles or for watercraft. Furthermore, sandwich panels of this type can be used in many other sectors, e.g. in the construction industry and furniture industry, etc.

[0038] In the description above, various features have been combined in one or more examples in order to improve the conciseness of the explanation. However, it should be clear that the above description is purely for illustrative purposes, but is in no way limiting. It covers all alternatives, modifications and equivalents of the various features and embodiments. Many other examples will be immediately and directly clear to a person skilled in the art reading the above description, on account of his knowledge in the art.

[0039] The embodiments have been selected and described in order to be able to set out, in the best possible way, the principles on which the disclosure herein is based, and the possible applications thereof in practice. As a result, persons skilled in the art can modify and use the disclosure herein and the various embodiments thereof in an optimal manner with regard to the intended use. In the claims and the description, the terms “containing” and “having” are used as neutral terms for the corresponding term “comprising”. Furthermore, use of the terms “a”, “an” and “one” is not in principle intended to exclude a plurality of such described features and components.

[0040] While at least one exemplary embodiment of the present disclosure herein(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.