Sandwich-Composite Component for Aircraft Interiors

Abstract

The invention relates to a sandwich composite component (1) for the interior of a passenger aircraft. One problem to be solved by the invention is that of proposing a cost-effectively produced sandwich composite component which is suitable for the interior of a passenger aircraft and fulfils current fire protection requirements. The layer structure of the sandwich composite component (1) according to the invention comprises: a core layer (10) made of polymer foam; a reinforcing layer (20) comprising fiber composite material; and in addition at least one functional layer (50); wherein said layers of the layer structure are integrally bonded to each other, in particular by an adhesive bond. The fiber composite material of the reinforcing layer (20) comprises a woven or laid fabric made of reinforcing fibers and a polymer matrix, which has a higher density than the polymer foam of the core layer (10). Furthermore, the at least one functional layer (50) comprises a metal foil, in particular an aluminium foil, which has a thinner layer thickness than the reinforcing layer (20).

Claims

1. A sandwich composite component (1) for the interior of a passenger aircraft, comprising a layer structure in a sandwich construction having a core layer (10) made of polymer foam; a reinforcing layer (20) comprising fiber composite material; and at least one functional layer (50); wherein these layers of the layer structure are substance bonded to each other; wherein the fiber composite material of the reinforcing layer (20) comprises a woven fabric made of fibers or a laid fabric made of fibers, and the fiber composite material of the reinforcing layer (20) comprises a polymer matrix that has a higher density than the polymer foam of the core layer (10), and the at least one functional layer (50) comprises a metal foil that has a smaller layer thickness than the reinforcing layer (20).

2. The sandwich composite component (1) according to claim 1, wherein the sandwich composite component (1) meets fire protection requirements for aircraft interior materials according to an EASA specification with regard to flammability, smoke density and/or heat release.

3. The sandwich composite component (1) according to claim 1, wherein the sandwich composite component (1) meets requirements according to EASA specification CS 25.853 (d) with regard to heat release and heat release rate, and in particular has a heat release rate HRR of ≤65 kW/m.sup.2 and a heat release HR of ≤65 kW*min/m.sup.2, determined according to CS 25.853 (d) and Appendix F, Part IV.

4. The sandwich composite component (1) according to claim 3, wherein the sandwich composite component (1) has an average heat release rate HRR of ≤45 kW/m.sup.2 and/or an average heat release HR of ≤40 kW*min/m.sup.2, determined according to CS 25.853 (d) and Appendix F, Part IV.

5. The sandwich composite component (1) according to claim 1, wherein with regard to smoke emission properties, the sandwich composite component (1) has an average specific optical smoke density Ds of <100 after 4 minutes determined according to ASTM test method F814-83.

6. The sandwich composite component (1) according to claim 1, wherein the reinforcing layer (20) is arranged between the functional layer (50) and the core layer (10) in the layer structure.

7. The sandwich composite component (1) according to claim 1, wherein the layer structure further comprises a separating layer (30) comprising a thermoplastic material.

8. The sandwich composite component (1) according to claim 7, wherein the separating layer (30) is arranged between the reinforcing layer (20) and the functional layer (50).

9. The sandwich composite component (1) according to claim 1, wherein the functional layer (50) consists of an aluminium foil, in particular a non-structural aluminium foil, having a thickness of between 7 μm and 300 μm, preferably between 7 μm and 100 μm.

10. The sandwich composite component (1) according to claim 1, wherein the core layer (10) is prefabricated as a rigid foam board or a rigid integral foam board.

11. The sandwich composite component (1) according to claim 1, wherein the sandwich composite component has a weight per unit area of <2.5 kg/m.sup.2, wherein the core layer (10) has a density of 20 to 300 kg/m.sup.3.

12. The sandwich composite component (1) according to claim 1, wherein the core layer (10) is made from or consists of polyurethane foam, in particular PUR and/or PIR.

13. The sandwich composite component (1) according to claim 1, wherein the core layer (10) is made from a PVC, PET, EPS, PE and/or PMI foam.

14. The sandwich composite component (1) according to claim 1, wherein the core layer (10) is made from or consists of a combination of at least two foams selected from: polyurethane, PVC, PET, EPS, PE or PMI foam.

15. The sandwich composite component (1) according to claim 1, wherein the layer structure comprises on one side of the core layer (10) the at least one functional layer (50) as a first functional layer and the reinforcing layer (20) as a first reinforcing layer, and on the other side of the core layer (10) a second functional layer (50) and a second reinforcing layer (20), wherein the first and the second functional layers (50) consist of an aluminium foil, which has a smaller layer thickness than the first reinforcing layer (20).

16. The sandwich composite component (1) according to claim 1, wherein the layer structure comprises at least one functional layer (50) made of metal foil on each side of the core layer (10).

17. The sandwich composite component (1) according to claim 1, wherein the reinforcing layer (20) comprises a fiber composite material, which is made from a prefabricated prepreg.

18. The sandwich composite component (1) according to claim 1, wherein the metal foil of the functional layer (50) comprises perforations.

19. The sandwich composite component (1) according to claim 1, wherein the layer structure comprises the following layer sequence: one first functional layer (50) comprising an aluminium foil; an adhesive ply (40) as one adhesive layer; a first separating layer (30) comprising a thermoplastic layer; the reinforcing layer as a first reinforcing layer (20) made of fiber composite material; the core layer (10) made of polymer foam, a second reinforcing layer (20) made of fiber composite material; a second separating layer (30) comprising a thermoplastic layer; an adhesive ply (40) as another adhesive layer; one second functional layer (50) comprising an aluminium foil; wherein these layers of the layer structure are substance bonded to each other.

20. An interior composite panel of an aircraft, the interior composite panel comprising or consisting of a sandwich composite component (1) according to claim 1.

21. Use of the sandwich composite component (1) according to claim 1 in an interior area of a passenger aircraft used by passengers and/or the crew.

Description

[0067] Further details, features and advantages of the invention can be taken—without restricting the generality of the above-mentioned features—from the following, more detailed description of preferred exemplary embodiments with reference to the attached drawings. These show, in a schematic diagram in each case, a partial vertical section of:

[0068] FIG. 1: a first embodiment of the sandwich composite component according to the invention;

[0069] FIG. 2: a second embodiment of the sandwich composite component according to the invention;

[0070] FIG. 3: a third embodiment of the sandwich composite component according to the invention;

[0071] FIG. 4: a fourth embodiment of the sandwich composite component according to the invention;

[0072] FIG. 5: a fifth embodiment of the sandwich composite component according to the invention; and

[0073] FIG. 6: a sixth embodiment of the sandwich composite component according to the invention.

[0074] FIG. 1 is a schematic view of a first embodiment of the sandwich composite component 1 according to the invention. The illustrated sandwich composite component 1 is a flat panel with a layer structure that is mirror-symmetrical to the mid-level in cross-section. The layer structure comprises an inner core layer 10, which is arranged between two reinforcing layers 20. On the outside of each reinforcing layer 20, a separating layer 30 is arranged. On the outside of each separating layer 30, an adhesive ply 40 and a functional layer 50 are located, the adhesive ply 40 integrally bonding each functional layer 50 to the adjacent separating layer 30.

[0075] The core layer 10 in FIG. 1 is in the form of a prefabricated rigid foam board made of polyurethane foam, and preferably has a density of approx. 40 to 80 kg/m.sup.3. The rigid foam board can comprise additional plies made of aluminium foil, one on each side, each having a thickness of between 50 μm and 90 μm (not shown). The core layer 10 has a significantly greater layer thickness or wall thickness in the transverse direction than each of the other layers and in particular keeps the two reinforcing layers 20 at a distance from each other according to the sandwich principle. The core layer can have a layer thickness of, e.g., 10 mm. Thanks to the core layer 10 made of PU foam, the sandwich composite component 1 also provides heat and sound insulation.

[0076] The two reinforcing layers 20 are technically identical and comprise a glass fiber composite with a phenolic resin matrix, wherein the proportion by weight of the matrix in the composite is, e.g., approximately 50%. The thickness of the reinforcing layers 20 here is discernibly greater than 150 μm, typically greater than 300 μm, generally mm. The reinforcing layers 20 are the mechanically load-bearing layers of the layer structure and are responsible for the high strength of the sandwich composite component 1. The density of the matrix per se can be approximately 1200 kg/m.sup.3, and the density of the reinforcing fibers per se approximately 2400 kg/m.sup.3. The combined density of the composite material of the reinforcing layer 20 lies between the two values and can be approximately 1800 kg/m.sup.3 with a proportion by weight of approximately 50%. Low-density reinforcing fibers, such as, e.g., carbon, cotton, viscose, thermoplastic and/or high-performance thermoplastic fibers can likewise be employed. The combined density of the composite material in this case can be lower than 1800 kg/m.sup.3.

[0077] The two separating layers 30 are likewise technically identical and comprise a film made of polyvinyl fluoride. The preferred product example according to Table 1 comprises Tedlar® TWH10BE 3 (DuPont, USA) as the polyvinyl fluoride film.

[0078] The two fire-protecting functional layers 50 are likewise identical, and in FIG. 1 they consist of an aluminium foil. The thickness of the aluminium foil is between 7 μm and 90 μm, e.g., 50 μm. An alloy from the 5xxx series according to EN 573-3/4, e.g. alloy 5052, is preferably employed as the aluminium foil. To facilitate production, the aluminium foil or functional layers 50 may have perforations with a diameter of <2 mm in a grid arrangement with a square grid dimension of approximately 20-25 mm. The aluminium foil of the functional layer 50 is non-structural in the mechanical sense. It contributes surprisingly effectively to improving the properties of the sandwich composite component 1, in particular the secondary fire properties, in the event of a fire. In FIG. 1, the aluminium foil represents the outer layer of the layer structure.

[0079] The layers of the layer structure are bonded to each other in a manner that is known per se, wherein, e.g., adhesive plies 40 made of a thermosetting resin or thermoset can be used.

[0080] The sandwich composite component 1 is preferably produced cost-effectively by a suitable press method, in particular by pressing the layer structure and curing in a hot pressing technique. This method is particularly advantageous if the sandwich composite component 1 is planar, and prefabricated reinforcing layers 20 in the form of prepregs are used. In the exemplary embodiment according to FIG. 1, prepregs were used for producing the reinforcing layers 20. The layers of the layer structure are laid in the above sequence and introduced into a hot press, where they are pressed together and cured in one step. The prepreg layers cure under the action of heat and integrally bond to the adjacent foam core 10 and the polyvinyl fluoride film 30. The adhesive plies 40 likewise cure and bond the polyvinyl fluoride film 30 to the aluminium foil 50. The layer structure, which may have been only pre-cured, can be completely cured by a subsequent thermal treatment in an oven at a temperature of up to 250° C., at which both the adhesive ply 40 and the matrix of the reinforcing layers 20 are completely cured.

[0081] It is likewise possible initially to prepare a laminate from the prepreg of the reinforcing layer 20, the polyvinyl fluoride film of the separating layer 30, the adhesive ply 40 and the aluminium foil of the functional layer 50 by hot pressing, and in the next step to bond said laminate to the core layer 10, e.g., a prefabricated rigid foam board.

[0082] For non-planar components in particular, a prefabricated rigid foam board of the core layer 10 can be placed in an open mold, a glass fiber layer laid on top of the rigid foam board and the arrangement covered with a polyvinyl fluoride film of the separating layer 30. Negative pressure is then generated under a film, e.g., approximately a 75-90% vacuum. A liquid matrix for the reinforcing layer 20 can in this case be introduced by resin infusion between the separating layer 30 and the core layer 10 under the effect of the vacuum, such that the glass fibers are impregnated with the resin and excess resin is removed by suction. The matrix can cure partially or completely at ambient temperature. If necessary, the matrix of the reinforcing layer 20 can be completely cured by a subsequent thermal treatment in an oven at an elevated temperature, up to approximately 250° C. In a further alternative production method, the reinforcing layer 20 can first be produced in a closed mold in a vacuum injection process or an RTM process. The mold can be heated in an oven or autoclave. Furthermore, the reinforcing layer 20 can also be produced by hand lay-up.

[0083] The suitably prefabricated reinforcing layer 20 with optional separating layer can then be bonded by a suitable technique to a prefabricated core layer 10 and the functional layers 50 to form the finished sandwich composite component 1. A not yet completely cured semi-finished product comprising the layer structure described above can also be bent to a desired shape and may be cured by a hot curing method. The production technique and the order in which the layers are produced are not important, in principle.

[0084] Technical data for a product example are given in the table below according to the layer sequence:

TABLE-US-00001 TABLE 1 (technical data for product example) Product example: sandwich composite board for the interior of a passenger aircraft Layer Type Functional layer Aluminium foil, layer thickness 50 μm, with perforations Adhesive ply Epoxy-based adhesive Separating layer Polyvinyl fluoride film Reinforcing layer GFRP: glass fiber reinforced composite with phenolic resin matrix (prepreg), approximately 50% fiber content, layer thickness 0.5 mm Core layer Rigid foam board made of PUR foam, layer thickness 10 mm Reinforcing layer GFRP: glass fiber reinforced composite with phenolic resin matrix (prepreg), approximately 50% fiber content, layer thickness 0.5 mm Separating layer Polyvinyl fluoride film Adhesive ply Epoxy-based adhesive Functional layer Aluminium foil, layer thickness 50 μm, with perforations

[0085] A sandwich composite component 1 constructed according to FIG. 1 and with the data according to Table 1 can in particular meet or exceed the fire protection requirements for aircraft interior materials according to EASA specification CS 25.853 a, d.

[0086] Tests on a sandwich composite component 1 produced according to FIG. 1 and Table 1 gave the following results: [0087] the sandwich composite component 1 has a heat release rate HRR of 39.9 kW m.sup.2 and a heat release of 23.3 kW min m.sup.2 (determined according to the provisions of Appendix F, Part IV of EASA specification CS 25); [0088] the sandwich composite component 1 according to FIG. 1 has a specific optical smoke density Ds=56 after 4 min. (determined according to ASTM test method F814-83); and [0089] the sandwich composite component 1 has an average flame time of 3 s after removal of the flame source, an average burn length of 43 mm and an average flaming time of drippings of 0 s, or none (each determined according to the provisions of CS 25.853 a and Appendix F, Part I of EASA specification with a vertical test arrangement).

[0090] FIG. 2 is a second possible embodiment of the sandwich composite component 2 according to the invention. The layer structure of the illustrated sandwich composite component 2, unlike the sandwich composite component 1 according to FIG. 1, comprises a reinforcing layer 22 made of benzoxazine resin/glass fiber composite on each side of the core layer 10 made of polyurethane foam. A functional layer 50 made of aluminium foil is arranged directly on the outside of each reinforcing layer 22. The matrix of the reinforcing layer 22 integrally bonds the reinforcing layer 22 to the core layer 10 and to the functional layer 50. The sandwich composite component 2 needs no separating layers or additional adhesive plies, since the benzoxazine-resin matrix can be directly bonded to the aluminium foil. Alternatively, however, the sandwich composite component can also comprise a fluoroplastic ply as the upper decorative layer 33, which is bonded to the aluminium foil by an adhesive ply 40 made of a thermoset, as shown by the variant of the sandwich composite component 2′ in FIG. 3.

[0091] FIG. 4 shows a schematic sandwich composite component 4 according to the invention as a further possible embodiment. The layer structure of this sandwich composite component 4, unlike the sandwich composite component 1 according to FIG. 1, was built up using a reinforcing layer 24 in the form of a laminate. A reinforcing layer 24 made of phenolic resin/glass fiber composite laminate was bonded on to each side of the core layer 10 made of polyurethane foam, i.e., a completely cured and no longer reactive laminate of phenolic resin/glass fiber composite was integrated into the layer structure. Because the phenolic resin in the laminate is completely cured before being incorporated into the layer structure, the laminate is bonded on to both sides of the core layer 10 by means of an adhesive ply 40 made of, e.g., a thermoset. A functional layer 50 made of aluminium foil is bonded to the structure on the outside of each reinforcing layer 24, in each case by means of a further adhesive ply 40 made of e.g. a thermoset. This variant of the sandwich composite component 4 needs no separating layers. Depending on the material of the adhesive ply, the layer structure can be cured at ambient temperature or at a higher temperature.

[0092] FIG. 5 shows a variation with a sandwich composite component 4′ wherein, in addition to the layer structure according to FIG. 4, a further reinforcing layer 24 made of the phenolic resin/glass fiber composite laminate is applied externally on each side by means of a further adhesive ply 40 in each case.

[0093] FIG. 6 shows as a variant a sandwich composite component 1′, wherein the functional layer 50 made of aluminium foil has been applied directly on to each side of the rigid foam core layer 10, which is located centrally in a cross-section of the sandwich composite component 1′, by means of adhesive plies 40 made of a thermoset. Furthermore, a separating layer 30 made of a thermoplastic polymer is bonded on to the outside of each functional layer 50 by means of an adhesive ply 40 in each case. A reinforcing layer 20 made of phenolic resin/glass fiber composite prepreg is arranged on the outside of each separating layer 30. This layer structure of the sandwich composite component 1′ according to FIG. 6 can also be pressed in a hot press in order to cure the matrix of the reinforcing layer 20 and the adhesive plies 40.

LIST OF REFERENCE NUMERALS

[0094] FIG. 1, FIG. 6: [0095] 1; 1′ sandwich composite component [0096] 10 core layer [0097] 20 reinforcing layer [0098] 30 separating layer [0099] 40 adhesive ply [0100] 50 functional layer [0101] FIG. 2, FIG. 3: [0102] 2, 2′ sandwich composite component [0103] 10 core layer [0104] 22 reinforcing layer [0105] 50 functional layer [0106] 40 adhesive ply [0107] 33 decorative layer [0108] FIG. 4, FIG. 5: [0109] 4; 4′ sandwich composite component [0110] 10 core layer [0111] 24 reinforcing layer [0112] 40 adhesive ply [0113] 50 functional layer