NEW COMPOSITE ARTICLE

Abstract

The present invention relates to a composite article comprising at least two layers (A) of component a) and at least one layer (B1) of component b). The respective layers (A) and (B1) are alternately linked together. The component a) has a compressive modulus of at least 10 MPa and can, therefore, be considered as a comparably rigid component, which can be also assigned as rigid core element, in contrast thereto the component b) has a compression stress value at a compression of 40% of not more than 20 kPa. By consequence, component b) can be considered as a comparably flexible (elastic) component. Therefore, the composite articles according to the present invention can be considered as semi-flexible materials due to the combination of alternating rigid and flexible segments (layers) within those composite articles. The composite articles according to the present invention may further comprise at least one layer (B2) of component b), which layer is also alternately linked together with the respective layers (A). In addition, at least one layer (B2) crosses at least one layer (B1) with an angle α in the range of 0°<α<180°, wherein both layers (B1) and (B2) are made of component b). The present invention further relates to a method for producing those composite articles as well as to the use of those composite articles in composite applications, for example, wind rotor blades or boat hulls or insulation applications, for example for curved walls or roofs or between rafters.

Claims

1.-17. (canceled)

18. A composite article comprising at least two layers (A) of component a) and at least one layer (B1) of component b), wherein the respective layers (A) and (B1) of components a) and b) are alternately linked together and wherein component a) has a compressive modulus of at least 10 MPa and component b) has a compression stress value at a compression of 40% of not more than 20 kPa.

19. The composite article according to claim 18, comprising at least one further layer (B2) of component b), wherein i) the respective layers (A) and (B1) of components a) and b) are alternately linked together, ii) the respective layers (A) and (B2) of components a) and b) are alternately linked together, and iii) at least one layer (B2) of component b) crosses at least one layer (B1) of component b) with an angle α in the range of 0°<α<180°.

20. The composite article according to claim 18, wherein the component a) has a tensile elongation in the range of not more than 25% or the component b) has a tensile elongation of at least 60%

21. The composite article according to claim 20, wherein the component a) has a tensile elongation in the range of 5 to 10% or the component b) has a tensile elongation of 100 to 1000%.

22. The composite article according to claim 18, wherein the component a) is at least one material selected from polyvinylchloride (PVC), polyethylene terephthalate (PET), polyurethane (PUR), polystyrene, a copolymer of styrene and acrylonitrile (SAN), a mixture of PVC and PUR, phenolic foams, polyimide foams, PEEK, PSU, PES-foams, PIR, PP (Neopolen P) or PS/PE-copolymer foams (E-Por).

23. The composite article according to claim 22, wherein component a) is PET.

24. The composite article according to claim 18, wherein the component b) is at least one polymer selected from a thermoplast, a thermoset, a crosslinked polymer or an at least partially closed cell foam.

25. The composite article according to claim 24, wherein the component b) is polyethylene terephthalate (PET), polyurethane, polyvinylchloride, vinyl nitrile, EVA foams, PLA-foam (Ecovio), TPU foam (Infinergy), PE (Neopolen E), olefin foams (EPM, EPDM, for example Armaflex), TPEs on the basis of ether, esther, amide, olefin, like hytrel, arnitel, pebax, a polyalkylene or a melamine/formaldehyde condensate.

26. The composite according to claim 25, wherein the polyalkylene is polyethylene (PE).

27. The composite article according of claim 18 comprising a plurality of layers (B1) and the individual layers (B1) are arranged in parallel.

28. The composite article according to claim 27, wherein the parallel arranged layers (B1) have the same distance to each other, the parallel arranged layers (B1) are all made of the same material as component b) or the parallel arranged layers (B1) have the same dimensions.

29. The composite article according to claim 27, wherein the composite article additionally comprises a plurality of layers (B2) and the individual layers (B2) are arranged in parallel.

30. The composite article according to claim 29, wherein the parallel arranged layers (B2) have the same distance to each other, the parallel arranged layers (B2) are all made of the same material as component b) or the parallel arranged layers (B2) have the same dimensions.

31. The composite article according to claim 27, wherein the layers (B1) and (B2) form a monitoring grid, wherein the angle α is 90° or the individual grid units have the same size or the parallel arranged layers (B1) as well as the parallel arranged layers (B2) are all made of the same material as component b).

32. The composite article according to claim 18, wherein the individual layers (A), (B1) and optionally (B2) are linked together by welding, thermal welding, solvent welding, gluing, adhering, spraying or in situ foaming.

33. The composite article according to claim 18, wherein the individual layers (A) and (B1) are made as panels of the same size in two dimensions, whereas the third dimension of the layer (B1) is not more than 20% of the third dimension of the layer (A).

34. The composite article according to claim 33, wherein the panels are rectangular planar plates.

35. The composite article according to claim 33, wherein the individual rectangular planar plates forming the layers (A) are alternately linked together via a layer (B1) in between the respective transverse sides of the individual rectangular planar plates.

36. A method for producing a composite article according to claim 18 comprising: a) linking one side of a first layer (A) with one side of a first layer (B1) in order to obtain an intermediate (I), b) linking one side of the intermediate (I), which side originates from the first layer (B1), to one side of a second layer (A) in order to obtain a composite article made of two layers (A) and one layer (B1), wherein the layers (A) and (B1) are alternately linked together, c) optionally linking one side of a second layer (B1) with one side of the composite article according to step b), which side of the composite article originates from a layer (A), in order to obtain a composite article made of two layers (A) and two layers (B1), wherein the layers (A) and (B1) are alternately linked together, wherein the step c) is optionally repeated at least once in order to obtain composite articles with a plurality of layers (A) and (B1) under the proviso that within each repetition of step c) either a further layer (A) or a further layer (B1) are alternately linked to one side of the respective composite article of the previous step, which side of the composite article originates from the respective other layers (A) or (B1), in order to obtain the alternate order of layers (A) and (B1) within the composite article.

37. The method according to claim 36, wherein the individual layers (A) or (B1) are made as panels of the same size and the panels are rectangular planar plates.

38. The method according to claim 37, wherein the individual rectangular planar plates forming the layers (A) and (B1) are linked together via the respective largest sides of the individual rectangular planar plates.

39. The method according to claim 36 comprising the additional step d): d) cutting the composite article (CA1) obtained according to steps a) to c) in an angle α0° relative to the linking area of the individual layers (A) and (B1) into at least one smaller composite article (CA2).

40. The method according to claim 39, comprising the additional steps e) and optionally f): e) linking one side of the smaller composite article (CA2) with one side of a first layer (B2) in order to obtain an intermediate (12), which in turn is linked via its side originating from layer (B2) to a further composite article (CA3) in order to obtain a composite article (CA4), wherein i) the respective layers (A) and (B1) of components a) and b) are alternately linked together, ii) the respective layers (A) and (B2) of components a) and b) are alternately linked together, and iii) at least one layer (B2) of component b) crosses at least one layer (B1) of component b) with an angle α in the range of 0°<α<180°, f) optionally repeating step e) at least once using at least one composite article (CA2), (CA3) or (CA4) and at least one further layer (B2) in order to obtain composite articles (CA5) comprising a plurality of layers (A), (B1) and (B2).

41. The method according to claim 39, wherein the composite article (CA1) is cut in an angle α=90° or the further article (CA3) is identical in respect of its dimensions to the smaller composite article (CA2).

42. The method according to claim 40, wherein the composite article (CA4) or the composite article (CA5) obtained according to steps a) to e) and optionally f) is cut in an angle α≠0 relative to the linking area of the individual layers (A) and (B2) into at least one smaller composite article (CA6).

43. The method according to claim 42, wherein the composite articles (CA4) or (CA5) are cut in an angle α=90°.

44. A method for producing A) airplane wings, wind rotor blades, boat hulls, trains, busses, cars and other composite sandwich structures, or B) an insulation material. employing a composite article according to claim 18.

Description

[0027] The present invention is specified further hereinafter,

[0028] The composite article according to the present invention comprises at least two layers (A) of component a) and at least one layer (B1) of component b), wherein the respective layers (A) and (B1) of components a) and b) are alternately linked together and wherein component a) has a compressive modulus of at least 10 MPa and component b) has a compression stress value at a compression of 40% of not more than 20 kPa.

[0029] This means that the composite article according to the present invention comprises a minimum of three layers, wherein two of the layers originate from component a) and one layer originates from component b). The three-layered composite article can be considered as the “smallest unit” of composite articles according to the present invention. Such a composite article is shown in FIG. 1A. However, the composite articles according to the present invention may comprise a plurality of individual layers (A) and (B1). FIG. 2 shows an example of such a “larger unit” of a composite article according to the present invention comprising layers (A) and (B1). There is no upper limit for the number of individual layers (A) and (B1) and optionally, as described below and depicted in (for example) FIG. 4, for the layers (B2). However, the total number of individual layers is governed by the respective layers (A) and (B1) of components a) and b) since they are alternately linked together. A plurality of individual layers may mean, for example, 2, 3, 4, 5, 10, 20, 50 or even more individual layers.

[0030] However, it is also possible that the articles according to the present invention may comprise some intermediate layers made of materials different than those of components a) or b). Such additional layers may be, for example, included into individual layer (A) or it may be placed/positioned in between a layer (A) and a layer (B1). However, it is preferred that the composite articles according to the present invention do not comprise any additional layers to layers (A) of component a), layers (B1) of component b) and optionally layers (B2) of component b).

[0031] The components a) and b), which form the respective layers (A) or (B1), respectively, differ in respect of their individual mechanical properties. Whereas component a) shows a rather high compressive modulus of at least 10 MPa, since it is a rather rigid material, component b) has a comparable low compression stress value at a compression of 40% of not more than 20 kPa, since it is a rather flexible/elastic material. Materials falling under the definition of component a) and b) according to the present invention are known to a person skilled in the art. Furthermore, a person skilled in the art knows the meaning of “compressive modulus” and “compression stress value” as such, as well as methods for measuring a compressive modulus and a compression stress value of a material. The compressive modulus of component a) and the compression stress value of component b) of the present invention are determined by DIN-norms, such norms are known to a person skilled in the art.

[0032] For component a) the compressive modulus is determined according to DIN EN ISO 844 (German version of October 2009, DIN ISO 844: 2009; total of 10 pages; in particular: item 9.4). For component b) the compression stress value at a compression of 40% is determined according to DIN EN ISO 3386-1 (German version of September 2010; total of 14 pages EN ISO 3386-1:1997+A1:2010). Both norms describe the determination of stress-strain characteristics in compression.

[0033] It is preferred that the component a) is at least one material selected from polyvinylchloride (PVC), polyethylene terephthalate (PET), polyurethane (PUR), polystyrene, a copolymer of styrene and acrylonitrile (SAN), a mixture of PVC and PUR, phenolic foams, polyimide foams, PEEK, PSU, PES-foams, FIR, PP (Neopolen P) or PS/PE-copolymer foams (E-Por), more preferably component a) is PET or a mixture of PVC and PUR, most preferably component a) is PET.

[0034] The component b) is preferably at least one polymer selected from a thermoplast, a thermoset, a crosslinked polymer and/or an at least partially closed cell foam, more preferably the component b) is polyethylene terephthalate (PET), polyurethane, polyvinylchloride, vinyl nitrile, EVA foams, PLA-foam (Ecovio), TPU foam (Infinergy), PE (Neopolen E), olefin foams (EPM, EPDM, for example Armaflex), TPEs on the basis of ether, esther, amide, olefin, like hytrel, arnitel, pebax, a polyalkylene and/or a melamine/formaldehyde condensate, the polyalkylene is preferably polyethylene (PE).

[0035] In one embodiment of the present invention the component b) is an epoxy resin.

[0036] As mentioned above, the composite articles according to the present invention may comprise a plurality of layers (B1) and the individual layers (B1) are preferably arranged in parallel, preferably the parallel arranged layers (B1) have the same distance to each other, the parallel arranged layers (B1) are all made of the same material as component b) and/or the parallel arranged layers (B1) have the same dimensions.

[0037] The form and the size (dimensions) of the individual layers (A), (B1) and, as described below, optionally (B2) may be the same or different. It is preferred that in a composite article according to the present invention, the individual layers (A) are each of the same dimension, the same holds true for the individual layers (B1) and optionally (B2). However, the size (dimensions) between an individual layer (A) on the one hand and individual layer (B1) and/or optionally layer (B2) on the other hand are preferably different, especially in one dimension (x-direction in relation to a rectangular coordinate system).

[0038] In one embodiment of the present invention, one dimension of a composite article (z-direction) is in the range of 5 to 100 mm. In case of a rectangular planar plate within this embodiment, the respective dimensions of the individual layers (A), (B1) and optionally (B2) have each the same value. Within this embodiment, the z-direction (z-dimension) is smaller than the x-direction (x-dimension) and the y-direction (y-dimension) as depicted in, for example, the composite articles CA2 within FIG. 3 as well as the composite article CA6 within FIG. 5. The respective value for the dimension in z-direction (for each layer) is made for the flat (unbended) form of the respective composite article.

[0039] It is also preferred that the individual layers (A) and (B1) are made as panels of the same size in two dimensions, whereas the third dimension of the layer (B1) is not more than 20%, preferably between 5% and 15% of the third dimension of the layer (A). More preferably the panels are rectangular planar plates. Such an embodiment of the present invention is depicted in FIG. 6B, left hand side. The respective values for the dimensions of the layers (B1) in relation to the layer (A) are made for the flat (unbended) form of the respective composite article according to the present invention.

[0040] It is even more preferred that the individual rectangular planar plates forming the layers (A) are alternately linked together via a layer (B1) in between the respective transverse sides of the individual rectangular planar plates as shown in the left hand side picture of FIG. 6D.

[0041] As mentioned above, composite articles according to the present invention may comprise at least one further layer (B2), which is also made of component b) as the layers (B1). The respective component b) within the layers (B1) on the one hand and (B2) on the other hand may be the same or different. It is preferred that component b) is the same within both types of layers (B1) and (B2). The number of individual layers (B1) and (B2) within a composite article of the present invention may be the same or different. The number of individual layers (B2) is not directly connected to the number of individual layers (A) and (B1) as shown above. The relation between the optional layer (B2) of component b) in connection with the layers (A) and (B1) in a composite article according to the present invention is as follows: [0042] i) the respective layers (A) and (B1) of components a) and b) are alternately linked together, [0043] ii) the respective layers (A) and (B2) of components a) and b) are alternately linked together, and [0044] iii) at least one layer (B2) of component b) crosses at least one layer (B1) of component b) with an angle α in the range of 0°<α<180°.

[0045] In one embodiment of the present invention, the composite article additionally comprises a plurality of layers (B2) and the individual layers (B2) are arranged in parallel, preferably the parallel arranged layers (B2) have the same distance to each other, the parallel arranged layers (B2) are all made of the same material as component b) and/or the parallel arranged layers (B2) have the same dimensions, most preferably the layers (B1) and (B2) form a monitoring grid, wherein the angle α is 90° and/or the individual grid units have the same size and/or the parallel arranged layers (B1) as well as the parallel arranged layers (B2) are all made of the same material as component b).

[0046] The individual layers (A), (B1) and optionally (B2) can be linked together in any way known to a person skilled in the art. Such a method for linking together the individual layers can be done, for example, by welding, thermal welding, solvent welding, gluing, adhering, spraying and/or in situ foaming, preferably by thermal welding or adhering, most preferably by thermal welding. Thermal welding can be, for example, carried out as described in WO 2012/016991.

[0047] In one embodiment of the present invention, it is preferred that the components a) and b) also have a specific value for the respective tensile elongation in addition to the above mentioned values for compressive modulus and compression stress value at a compression of 40%. Tensile elongation as such as well as methods for determining parameters are known to a person skilled in the art. Tensile elongation values for components a) and b) of the present invention are determined according to the ASTM Standard Test Method C297/C297M-04 (reapproved 2010).

[0048] In one embodiment of the present invention the component a) has a tensile elongation in the range of not more than 25%, preferably in the range of 1 to 20%, more preferably of 2 to 15%, most preferably of 5 to 10%, and/or the component b) has a tensile elongation of at least 60%, preferably in the range of 80 to 5000%, most preferably of 100 to 1000%.

[0049] Another subject of the present invention is a method for producing a composite article as defined above. This method comprises the steps a) to c) as follows: [0050] a) one side of a first layer (A) is linked with one side of a first layer (B1) in order to obtain an intermediate (I), [0051] b) one side of the intermediate (I), which side originates from the first layer (B1), is linked to one side of a second layer (A) in order to obtain a composite article made of two layers (A) and one layer (B1), wherein the layers (A) and (B1) are alternately linked together, [0052] c) optionally linking one side of a second layer (B1) with one side of the composite article according to step b), which side of the composite article originates from a layer (A), in order to obtain a composite article made of two layers (A) and two layers (B1), wherein the layers (A) and (B1) are alternately linked together, [0053] wherein the step c) may be repeated at least once in order to obtain composite articles with a plurality of layers (A) and (B1) under the proviso that within each repetition of step c) either a further layer (A) or a further layer (B1) are alternately linked to one side of the respective composite article of the previous step, which side of the composite article originates from the respective other layers (A) or (B1), in order to obtain the alternate order of layers (A) and (B1) within the composite article.

[0054] Within this method, it is preferred that the individual layers (A) and/or (B1) are made as panels of the same size and the panels are rectangular planar plates, preferably the individual rectangular planar plates forming the layers (A) and (B1) are linked together via the respective largest sides of the individual rectangular planar plates.

[0055] The method according to the present invention may comprise the additional step d): [0056] d) the composite article (CA1) obtained according to steps a) to c) is cut in an angle α≠0° relative to the linking area of the individual layers (A) and (B1) into at least one smaller composite article (CA2).

[0057] Furthermore, the method according to the present invention may additionally comprise steps e) and optionally f): [0058] e) one side of the smaller composite article (CA2) is linked with one side of a first layer (B2) in order to obtain an intermediate (I2), which in turn is linked via its side originating from layer (B2) to a further composite article (CA3) in order to obtain a composite article (CA4), wherein [0059] i) the respective layers (A) and (B1) of components a) and b) are alternately linked together, [0060] ii) the respective layers (A) and (B2) of components a) and b) are alternately linked together, and [0061] iii) at least one layer (B2) of component b) crosses at least one layer (B1) of component b) with an angle α in the range of 0°<α<180°, [0062] f) optionally step e) may be repeated at least once using at least one composite article (CA2), (CA3) or (CA4) and at least one further layer (B2) in order to obtain composite articles (CA5) comprising a plurality of layers (A), (B1) and (B2).

[0063] Within the inventive method, it is preferred that the composite article (CA1) is cut in an angle α=90° and/or the further article (CA3) is identical in respect of its dimensions to the smaller composite article (CA2).

[0064] Furthermore, it is preferred that the composite article (CA4) or the composite article (CA5) obtained according to steps a) to e) and optionally f) is cut in an angle α≠0 relative to the linking area of the individual layers (A) and (B2) into at least one smaller composite article (CA6), preferably the composite articles (CA4) or (CA5) are cut in an angle α=90°.

[0065] Another subject-matter of the present invention is the use of a composite article as defined above [0066] A) in airplane wings, wind rotor blades, boat hulls, trains, busses, cars and other composite sandwich structures, and/or [0067] B) as insulation material.

[0068] The composite article is for example used as insulation material for curved walls or roofs or between rafters.

[0069] FIG. 1A shows a composite article according to the present invention, which is assigned as (CA1). The composite article (CA1) comprises two layers (A) and one layer (B1), wherein the respective layers (A) and (B1) are alternately linked together.

[0070] FIG. 1B shows an intermediate (I), which comprises only one layer (A) and only one layer (B1). Such an intermediate (I) is formed in step (a) of the method for producing a composite article according to the present invention. In order to arrive at a composite article according to the present invention, such as the composite article (CA1) as shown in FIG. 1A, the intermediate (I) as depicted in FIG. 1B has to be additionally linked with a second (further) layer (A). The linkage has to be carried out with such a side of the intermediate (I), which originates from the first layer (B1) in order to arrive at a composite article in which the respective layer (A) and (B1) are alternately linked together (alternating linking order of the respective layers).

[0071] FIG. 2 visualizes the method for producing a composite article according to the present invention, wherein the respective composite article (CA1) already comprises several individual layers (A) and (B1), which are alternately linked together. In other words, optional step c) of the method for producing a composite article according to the present invention has then been carried out several times. As it can be seen from FIG. 2, step c) of the method according to the present invention will be repeated once again in order to arrive at an even bigger composite article of the present invention comprising 7 layers (A) and 6 layers (B1), which are alternately linked together.

[0072] It has to be noted that in the context of the present invention a composite article, such as the one shown in FIG. 2, may comprise individual layers (A) and/or (B1) and/or optionally (B2), which differ in respect of the respective components a) or b). For example, the composite article as shown in FIG. 2 may comprise one or two individual layers (A), which are made of a first material falling under the definitions of component a), whereas the remaining individual layers (A) are made of a different material falling under the definition of component a). The same holds true for the respective layers (B1) and/or (B2) as shown, for example, in FIG. 4, which layers are made of material falling under the definition of component b).

[0073] In the present invention, it is preferred that the respective composite articles comprise individual layers (A) and/or (B1) and/or optionally (B2), which are made of the same material of component a) or component b), respectively. It is furthermore preferred that both layer (B1) and layer (B2) is made of the same material falling under the definition of component b).

[0074] As it can be seen from FIG. 3, the composite article (CA1) according to the present invention as shown, for example, in FIG. 2, can be cut to smaller parts. Both composite articles (CA1*) and (CA2) as shown in FIG. 3 are composite articles according to the present invention, since both composite articles (CA1*) and (CA2) comprise at least two layers (A) of component a) and at least one layer (B1) of component b), which layers (A) and (B1) are alternately linked together. The cutting as envisualized in FIG. 3 was carried out at an angle α of 90° (relative to the linking area of the individual layer (A) and (B1)).

[0075] As shown in FIG. 4, the smaller composite article (CA2), the same as depicted in the upper part of FIG. 3, can be linked together—via a layer (B2) of component b)—to another composite article in order to arrive at a composite article having both layers (A) and (B1) alternately linked together, and layers (A) and (B2) alternately linked together, wherein at least one layer (B2) of component b) crosses at least one layer (B1) of component b) with an angle α in the range of 0°<α<180°. Preferably, the angle α is 90° as depicted in FIG. 4.

[0076] It has to be noted that the composite article (CA5) depicted on the right hand side of FIG. 4 does not necessarily have to be employed in connection with composite article (CA2) in order to arrive at a composite article having layers (A), (B1) and (B2). The composite layer (CA5) is already such a specific composite layer comprising layers (A), (B1) and (B2), wherein at least one layer (B2) crosses at least one layer (B1) with an angle α in the range of 0°<α<180°. Instead of the composite article (CA5) as shown on the right hand side of the embodiment according to FIG. 4, only a single (individual) layer (A) may be employed in order to arrive at (obtain) a composite article having layers (A), (B1) and (B2), wherein (at least) one layer (B2) of component b) crosses at least one layer (B1) of component b) with an angle α in the range of 0°<α<180°.

[0077] As shown in FIG. 5, such a composite article (CA5) according to the present invention may itself be cut again into smaller pieces. The composite article (CA6), as depicted in the upper part of FIG. 5, was cut out of the composite article (CA5) as obtained from FIG. 4 in an angle α=90°. The remainder of composite article (CA5) as obtained from FIG. 4 is assigned in FIG. 5 (lower part) as composite article (CA5*). Both composite articles (CA5*) and (CA6) of FIG. 5 are identical in respect of the number and chemical composition of the respective layers (A), (B1) and (B2), but the two composite articles differ in respect of their dimensions, since composite article (CA6) is smaller (in respect of the z-dimension) compared to composite article (CA5*).

[0078] FIG. 6 shows a comparison for “S-curve bending behavior” of individual panels or composite articles, respectively. FIG. 6A reveals a (one-layered) panel, which is a rectangular planar plate having slits on one side of the panel surface. The left hand side of FIG. 6A shows the respective panel in unbended (planar) form/position, whereas the right hand side reveals the S-curve bending behavior of the respective panels. As it is shown on the right hand side of FIG. 6A, the behavior in terms of both a complex two-dimensional and a complex three-dimensional draping can be considered as rather bad.

[0079] As shown in FIG. 6B, the slits on one side of the respective panel can be even broadened to obtain gaps or grooves on one side of the respective panel. The panel is not entirely cut into three equal parts, but on the lower end of the panel there is still some amount of the panel material left to combine the three parts of the upper side of this panel into one body. As it can be seen by comparing the right hand side picture of FIG. 6B with the respective right hand side picture of FIG. 6A, the S-curve bending behavior has improved a bit.

[0080] In contrast to the panel according to FIG. 6A, the respective panel according to FIG. 6C has slits on two opposing surface sides of the respective panel. Again, the left hand side picture of FIG. 6C shows the panel in planar (unbended) form, whereas the right hand side picture shows C-curve bending behavior. This behavior is improved further compared to the respective behavior of the panel with grooves on one side as shown in FIG. 6B.

[0081] However, the by far best S-curve bending behavior can be obtained with the composite articles according to the present invention as shown in FIG. 6D on the right hand side. As it is shown on the left hand side of the picture of FIG. 6D for the planar (flat/unbended) form/position of the respective composite article, the composite article contains three layers (A) of component a) and three layers (B1) of component b), wherein the respective layers (A) and (B1) are alternately linked together. FIG. 6D visualizes an embodiment of the present invention, wherein individual rectangular planar plates forming the layers (A) are alternately linked together via a layer (B1) in between the respective transverse sides of the individual rectangular planar plates of the layer (A). It is also shown in FIG. 6D (on the left hand side) that the composite articles according to this embodiment of the present invention are made of individual layers (A) and (B1) with the same size in two dimensions, whereas the third dimension of the layer (B1) is not more than 20% of the third dimension of the layer (A). The third dimension can be considered as the x-direction of a rectangular coordinate system. Due to the very flexible (highly elastic) component (B1) the individual layers (A) and (B1) are fixed together in a very stable way and the composite article as such shows a superior S-curve bending behavior in terms of both a complex two-dimensional and a complex three-dimensional draping.

[0082] The invention is illustrated hereinafter further by the examples.

[0083] The following calculations illustrate the problem of liquid polymer resin consumption in panels/composite articles according to the prior art:

[0084] Calculation for a core material with a typical thickness of 20 mm and a density of 100 kg/m.sup.3 and a typical liquid polymer density of 1000 kg/m.sup.3.

[0085] The pure core material weight is 1 m.sup.2×0.02 m×100 kg/m.sup.3=2 kg

Standard Resin Uptake at the Upper and Lower Surface +1 kg:

[0086] No slits, but resin uptake on the surface of roughly 0.5 kg/m.sup.2 for both sides of the sandwich (2 m.sup.2)

Case I) 2-Dimensional Curvature (Tubular)

[0087] a) Additional resin uptake through fresh surface after 1 dimensional cutting (defined by processing tools) +1 kg:

[0088] If the rigid core material is slit in 1 dimension e.g. every 20 mm with a slit breadth of 0 mm then the additional surface created in the fifty slits will be 50×2×20 mm*1 m=2 m.sup.2. This additional surface will cause an additional resin uptake of 1 kg/m.sup.2.

[0089] b) Additional resin uptake in voids after 1 dimensional slitting (defined by processing tools) +1 kg:

[0090] If the rigid core material is slit in 1 dimension e.g. every 20 mm with a slit breadth of 1 mm then this volume will be filled and the weight increase of 50×0.02 m×0.001 m×1 m*1000 kg/m.sup.3=1 kg will show even if the material is lying flat.

[0091] c) Additional resin uptake in voids in tubular curvature (defined by component geometry) +0.4 kg:

[0092] If the slit material is bend in a tubular shape like e.g. the root section or the leading edge of a rotor blade then the voids caused by the slitting will open up even further due to the bending of the material. For a tubular shape where material of a thickness B and a length L is bend into a tubular shape with a much larger diameter D, then the additional void opening up has a volume share of (Pi( )B*B*L)/(Pi( )*D*B*L)=B/D. For a 20 mm core material in shape of a tube of 1 m diameter, the additional void percentage is 2%. This again translates into an additional weight increase of 2%*1000 kg/m.sup.3/100 kg/m.sup.3=20% or 0.4 kg out of 2 kg.

[0093] Case II) 3-Dimensional Curvature (Spherical)

[0094] a) Additional resin uptake through fresh surface after 2 dimensional cutting (defined by processing tools) +2 kg:

[0095] If the rigid core material is slit in 2 dimensions e.g. every 20 mm with a slit breadth of 0 mm then the additional surface created in the fifty slits will be (50+50)×2×20 mm*1 m=4 m.sup.2. This additional surface will cause an additional resin uptake of 2 kg/m.sup.2.

[0096] b) Additional resin uptake in voids after 2 dimensional slitting (defined by processing tools) +2 kg:

[0097] If the rigid core material is slit in 2 dimensions e.g. every 20 mm with a slit breadth of 1 mm then this volume will be filled and the weight increase of roughly (50+50)×0.02 m×0.001 m×1 m*1000 kg/m.sup.3=2 kg will show even if the material is lying flat.

[0098] c) Additional resin uptake in voids in spherical curvature (defined by component geometry) +1.2 kg:

[0099] If the slit material is bent in a spherical shape like e.g. the pressure dome in an airplane then the voids caused by slitting will open up even further due to the bending of the material. For a spherical shape where material of a thickness B is bend into a spherical shape with a much larger diameter D, then the additional void opening up has a volume share in relation to the core material of (2π( ).D.B2)/(⅓π( ).Math.D2.Math.B)=6.Math.B/D. For a 30 mm core material in shape of a sphere of 3 m diameter, the additional void percentage is 6%. This again translates into an additional weight increase of 6% 1000 kg/m.sup.3/100 kg/m.sup.3=60% or 1.2 kg of 2 kg.