AU7513100A

AU7513100A - Method for producing a sandwich panel and a body component

Info

Publication number: AU7513100A
Application number: AU75131/00A
Authority: AU
Inventors: Kurt Behre
Original assignee: Alcan Kapa GmbH
Current assignee: 3A Composites GmbH
Priority date: 1999-09-08
Filing date: 2000-09-01
Publication date: 2001-04-10
Also published as: ES2193987T3; WO2001017764A1; TW577811B; CN1131142C; KR20020040802A; EP1210226A1; DE50001653D1; BR0013884A; DE19942922A1; EP1210226B1; MXPA02002552A; CN1373708A; CA2384078A1; JP2003508270A; ATE236012T1

Abstract

The invention relates to methods for producing a light component (a sandwich panel or a component for a vehicle body) that is easy to construct. A plurality of cup-like cavities (18) are embodied in a flexible metal foil (16). An outer layer (12, 24) is applied to each side of the flexible metal foil (16). The opening of each cup-like cavity (18) is first covered by an outer layer (12) and the remaining outer layer (24) is then applied to the free ends of the cavities (18). An already formed sheet metal (24) of the body can be connected to the tip surfaces (26) of the cup-like cavities (18) by means of an adhesive (26) for producing a car body component (22), whereby said sheet metal is used as the remaining outer layer.

Description

WO 01/17764 PCT/EPOO/08562 Method for producing a sandwich panel and for producing a body component 5 The invention relates to a method for producing a sandwich panel and for producing a body component. The invention also relates to a sandwich panel and to a body component produced using a corresponding method. 10 Sandwich panels are known from the prior art, primarily as honeycomb sandwich panels, the honeycomb-like intermediate layer of which comprises a hard aluminum alloy. This layer is made "endless" in a discontinuous 15 method by adhesive bonding by the individual structures. Finally, covering layers are laminated onto both sides of the honeycomb structure. The honeycomb sandwich panels formed in this way cannot be deformed in three dimensions, since the walls of the honeycomb 20 cells are joined to one another. The procedure is discontinuous and therefore relatively uneconomical. In another method for producing a sandwich panel which is known from the prior art, long PET tubes are stuck 25 together to form a bundle. The PET tube bundle obtained in this way is then cut into disks perpendicular to the longitudinal extent of the PET tubes. Finally, covering layers are laminated onto both sides of each individual disk. This method too can only be carried out 30 discontinuously. The invention is based on the object of providing a method which allows sandwich panels and body components to be produced economically with little difficulty. 35 REPLACEMENT SHEET (RULE 26) WO 01/17764 - 2 - PCT/EPOO/08562 Furthermore, it is intended to provide a structurally simple and lightweight sandwich panel and body component. 5 This object is achieved by a method for producing a sandwich panel having the features of patent claim 1. Advantageous and preferred refinements of the method according to the invention form the subject matter of claims 2 to 4. 10 A sandwich panel according to the invention forms the subject matter of patent claim 5. Advantageous and preferred embodiments of the sandwich panel according to the invention form the subject matter of claims 6 15 to 10. The particular advantage of the method according to the invention compared to the methods for production of a sandwich panel which are known from the prior art 20 consists in the fact that the method can be carried out continuously, despite using an intermediate layer made from soft, flexible aluminum material. A sandwich panel according to the invention has a high 25 strength and is extremely lightweight. Moreover, it can be designed so that it can be deformed in three dimensions by using a suitable arrangement of the recesses. 30 Sandwich panels which have been produced in accordance with the invention can preferably be used in automotive engineering (roof linings, rear parcel shelves, etc) and in display technology. 35 The cup-like recesses can be formed by pressing or by deep-drawing. REPLACEMENT SHEET (RULE 26) WO 01/17764 - 3 - PCT/EPOO/08562 To allow the cup-like recesses to be formed without damage to the material, the material of the flexible metal foil preferably has a modulus of elasticity of at least 70 x 103 N/mm2 5 The flexible metal foil expediently consists of Al or an Al alloy or of Cu or a Cu alloy, which is expediently from 10 gm to 200 pm, preferably 20 gm to 100 gm, thick. 10 The cup-like recesses are formed substantially in the shape of an ellipsoid, a sphere, a cylinder, a truncated cone or a truncated pyramid. 15 The covering layers may consist of metal, for example of Al or an Al alloy or of Cu or a Cu alloy, which is preferably from 0.5 mm to 2.0 mm thick. However, the covering layers may also consist of 20 plastic, e.g. of PET or PP or PS or ABS. It is also possible to use a Resopal plate as the covering layer. A Resopal plate of this type is from 0.4 mm to 2.0 mm, preferably 1.3 mm, thick. 25 The covering layers are preferably adhesively bonded to the flexible metal foil. The covering layers may not only be planar but may also 30 be curved, since the intermediate layer can adapt to its shape. Moreover, it may be structured, for example it may have ribs. Finally, it is also possible for a sandwich panel to be 35 formed in multilayer form. For this purpose, a further intermediate layer comprising flexible metal foil with cup-like recesses is applied to one of the covering REPLACEMENT SHEET (RULE 26) WO 01/17764 - 4 - PCT/EPOO/08562 layers, and a further covering layer is secured to the intermediate layer. A method for producing a body component which achieves 5 the object of the invention forms the subject matter of patent claim 11. By contrast to the method according to patent claim 1, in this method the other covering layer is formed directly by the metal body sheet. 10 The laminated structure which is bonded on ensures that the body component has a high strength combined with a low weight. In particular the torsional rigidity is very high. Moreover, the body component according to the invention has good acoustic properties and 15 excellent resistance to corrosion. The adhesive used is preferably an encapsulated, heat--activatable adhesive system which is activated at a temperature of over 165 0 C and then fully reacts. The 20 laminated structure and the metal body sheet are joined by the application of pressure and the simultaneous supply of heat. The body component is then able to withstand temperatures of over 200 0 C. 25 Before the joining operation, encapsulated foam systems or foam systems provided with microcapsules may be introduced between laminated structure and metal body sheet, which foam systems are activated during the joining. This results in good heat and sound 30 insulation. The covering layer is preferably an aluminum sheet. The method according to the invention can be used to 35 produce, for example, car roofs, hoods, trunk lids, doors or other three-dimensionally deformed components as the body components. REPLACEMENT SHEET (RULE 26) WO 01/17764 - 5 - PCT/EPOO/08562 Exemplary embodiments of the invention are explained in more-detail below with reference to drawings, in which: 5 Fig. 1 shows a plan view of an intermediate layer of a first embodiment of a sandwich panel, Fig. 2 shows a first variant of a cup-like recess, Fig. 3 shows a second variant of a cup-like recess, Fig. 4 diagrammatically depicts the procedure involved 10 in a method for producing a sandwich panel, Fig. 5 shows an exploded view of a second embodiment of the sandwich panel, as seen from the side, Fig. 6 shows an exploded view of the sandwich panel shown in Fig. 5, as seen from above, 15 Fig. 7 shows a double-layer intermediate layer, Fig. 8 shows a side view of a third embodiment of a sandwich panel with a double-layer intermediate layer, Fig. 9 shows a side view of a fourth embodiment of a 20 sandwich panel with a double-layer intermediate layer, Fig. 10 shows a laminated structure for producing a car roof, Fig. 11 shows a partial cross section through a car 25 roof, Fig. 12 shows the detail XII from Fig. 11. The intermediate layer 1 shown in Fig. 1 comprises a flexible metal foil, into which a multiplicity of 30 recesses 2 have been stamped with a uniform distribution in one direction. This can be achieved, for example, by pressing or by deep-drawing. The flexible metal foil of the intermediate layer 1 may 35 consist, for example, of Al, an Al alloy or of Cu or a Cu alloy, or other metals which can be drawn or stamped. It is customary to employ metal foils which REPLACEMENT SHEET (RULE 26) WO 01/17764 - 6 - PCT/EPOO/08562 are from 10 pm to 200 gm thick. In most application examples, however, the flexible metal foil is from 20 pm to 100 gm thick. 5 The material used for the flexible metal foil of the intermediate layer 1 preferably has a modulus of elasticity of at least two 2 x 103 N/mm 2 in the case of plastics and 70 x 103 N/mm2 in the case of metals (e.g. aluminum). 10 The cup-like recesses 2 may be in various forms. Two particularly expedient shapes for the cup-like recesses 2 are shown in Figures 2 and 3. 15 The recess 2 shown in Fig. 2 is in the shape of half an ellipsoid, while the recess 2 shown in Fig. 3 is in the shape of half an ellipsoid which has been cut off in a straight line at its free end 8. 20 The cup-like recesses 2 may also be formed in the shape of spheres, cylinders, truncated cones or truncated pyramids. The diameter of the cup-like recesses preferably approximately corresponds to the thickness of the flexible metal foil which has been deformed into 25 the intermediate layer. After the cup-like recesses 2 have been formed in the flexible metal foil in order to form the intermediate layer 1, a covering layer 3 or 4 is applied to both 30 sides of the intermediate layer 1. In the process, at each recess 2, firstly the opening 7 of the recess 2 is closed by one covering layer 3, and only then is the other covering layer 4 joined to the free end 8 of the corresponding recess 2. 35 This is important since closing the opening 7 of the recess 2 by means of the covering layer 3 leads to an REPLACEMENT SHEET (RULE 26) WO 01/17764 - 7 - PCT/EPOO/08562 air cushion being formed in the recess 2, which prevents the recess 2, which consists of flexible material, being compressed when the other covering layer 4 is applied. 5 The latter method steps are diagrammatically illustrated in Fig. 4. The arrows in Fig. 4 indicate the direction of movement of the individual components. The intermediate layer 1 is conveyed continuously in 10 one plane. A covering layer 3, which is coated with an adhesive 9, for example a polyurethane adhesive, on the side which faces the intermediate layer 1 is fed continuously to that side of the intermediate layer 1 which is provided with the openings 7 of the recesses 2 15 and is adhesively bonded thereto, with the result that the openings 7 are closed off by the covering layer 3. The covering layer 4, which is likewise coated with an adhesive 9, for example a polyurethane adhesive, on the side which faces the intermediate layer 1 is fed to the 20 intermediate layer 1 - after the covering layer 3, as seen in the direction of movement of the intermediate layer 1 - and is adhesively bonded to the free ends 8 of the recesses 2. At this time, the openings 7 of the recesses 2 have already been closed off by the covering 25 layer 3. Then, the sandwich structure formed in this way is cut into sandwich panels of the desired size. It is also possible first of all to apply only the covering layer 3 to the intermediate layer 1 on the 30 side of the openings 7, and for this component to be temporarily stored as a laminated structure, which is described in more detail below with reference to Fig. 10. The other covering layer 4 can be applied at a later time. This allows the optional application of a 35 very wide range of covering layers 4. REPLACEMENT SHEET (RULE 26) WO 01/17764 - 8 - PCT/EPOO/08562 The covering layers 3, 4 may consist of metal, e.g. of Al or an Al alloy or of Cu or a Cu alloy. Depending on the particular application, the thickness of the covering layers 3, 4 is normally from 0.5 mm to 2.0 mm. 5 However, it is also possible to use thicker or thinner covering layers 3, 4. The covering layers 3, 4 may also consist of plastics, for example of PET or PP or PS or ABS or may be 10 designed as Resopal plates. In this case, it is preferable to use Resopal plates with a thickness of from 0.4 mm to 2.0 mm. In the second embodiment of the sandwich panel, which 15 is shown in Fig. 5 and 6, the covering layers 3, 4 are not coated with an adhesive. A double-sided adhesive sheet 5 is in each case arranged between the covering layers 3, 4 and the intermediate layer 1. The adhesive sheet 5 is activated by thermal means. 20 It is also possible for an encapsulated adhesive system to, be used as the adhesive. An encapsulated adhesive system is a two-stage adhesive. A first component is activated at, for example, 70-80 0 C. The other component 25 is activated during the deformation to form the component, at a temperature of, for example, 160-180 0 C. This results in a transition from thermoplastic to thermoset. 30 Fig. 7 shows a two-layer intermediate layer 1 having a plurality of upwardly extending recesses 2' and a plurality of downwardly extending recesses 2, which are in each case formed in a flexible metal foil. A row of recesses 2 alternates with an adjoining row comprising 35 recesses 2'. The two metal foils are adhesively bonded to one another, so that one metal foil forms the covering layer which closes off the recesses 2 or 2' of REPLACEMENT SHEET (RULE 26) WO 01/17764 - 9 - PCT/EPOO/08562 the other metal foil. However, it is also possible for the recesses 2, 2' of each metal foil to be closed off by a covering layer and for these covering layers to be joined to one another. 5 The two-layer intermediate layer 1 shown in Fig. 7 is used in the second embodiment of the sandwich panel, which is shown in Fig. 8. In each case one double-sided adhesive sheet 5 or 5' is arranged between the free 10 ends of the recesses 2, 2' and the associated covering layers 3 and 4. The recesses 2, 2' are in each case in the shape of half an elongate ellipsoid. The fact that there are fewer upwardly extending 15 recesses 2' than downwardly extending recesses 2 means that the bending resistance of the sandwich panel in one direction is greater than in the other direction, so that the sandwich panel can be bent in order to adapt its shape according to installation conditions. 20 The third embodiment shown in Fig. 9 differs from the second embodiment with regard to the shape of the recesses 2, 2' which in this case are formed in the shape of a compressed ellipsoid. 25 Fig. 10 shows a laminated structure 10 for the production of the car roof 22 which is shown in Fig. 11 and comprises an aluminum plate 10, an aluminum foil 16, which is provided with cup-like recesses 18, and a 30 deformed metal body sheet 24, which are adhesively bonded to one another. The laminated structure 10 comprises the aluminum plate 12, to the upper surface of which a double-sided 35 adhesive sheet 14 has been stuck. The aluminum foil 16, into which a multiplicity of cup-like cylindrical recesses 18 has been stamped in one direction, is REPLACEMENT SHEET (RULE 26) WO 01/17764 - 10 - PCT/EPOO/08562 adhesively bonded to the opposite side of the adhesive sheet 14 from the aluminum plate 12. The adhesive sheet 14 is activated by thermal means. The adhesive sheet 14 causes the openings 28 of the recesses 18 in 5 the aluminum foil 16 to be closed off in an airtight manner. The end faces 26 of the recesses 18 are planar and run parallel, at one height, to the aluminum plate 12. 10 An encapsulated adhesive system 20, the first component of which has been activated at 70-801C, is applied to the end faces 26 of each of the recesses 18. The other component has an activation temperature of 160-180 0 C. 15 The laminated structure 10 can be temporarily stored in this state. To produce the car roof 22 shown in Fig. 11, the laminated structure 10 is laid, in a press tool, onto 20 the inner side of a metal body sheet 24 which has already been deformed, in such a way that the end faces 26 bear against the metal body sheet 24, the encapsulated adhesive system 20 being arranged between the metal body sheet 24 and the end faces 26. 25 Then, the laminated structure 10 and the metal body sheet 24 are joined under pressure, with heat being supplied at the same time, the temperature of this heat being above the activation temperature of the second 30 component of the encapsulated adhesive system 20. This results in a transition of the adhesive system 20 from the thermoplastic to the thermoset, with the result that a thermally stable bond is formed. 35 The metal body sheets 24 used are preferably steel sheets or aluminum sheets with a thickness of less than 0.6 mm. The thickness of the aluminum plate 12 is REPLACEMENT SHEET (RULE 26) WO 01/17764 - 11 - PCT/EPOO/08562 preferably from 100 to 200 g. The recesses 18 preferably have an external diameter of from 5 to 8 mm, a height of from 2 to 5 mm and are distributed uniformly at intervals of from 2 to 5 mm. As an 5 alternative to the adhesive sheet 14, it is also possible to use a different thermoplastic or encapsulated adhesive. Before the joining operation, encapsulated foam systems 10 or foam systems provided with microcapsules may be introduced between laminated structure and metal body sheet, and these foam systems are activated during the joining. This results in good heat and sound insulation. REPLACEMENT SHEET (RULE 26)

Claims

1. A method for producing a sandwich panel, 5 comprising the following steps: - forming a multiplicity of cup-like recesses in a flexible metal foil, and - applying a covering layer to each side of the flexible metal foil, during which process, at 10 each cup-like recess, first of all the opening is closed by one covering layer, and then the other covering layer is applied to the free ends of the recesses. 15

2. The method as claimed in claim 1, characterized in that the cup-like recesses are formed by pressing or by deep-drawing.

3. The method as claimed in one of the preceding 20 claims, characterized in that the cup-like recesses are shaped substantially in the form of an ellipsoid or a sphere or a cylinder or a truncated cone or a truncated pyramid. 25

4. The method as claimed in one of the preceding claims, characterized in that at least one *of the covering layers is adhesively bonded to the flexible metal foil. 30

5. A sandwich panel having two covering layers (3, 4), which run substantially parallel to one another, and an intermediate layer (1), which extends between the two covering layers (3, 4), characterized in that the intermediate layer (1) has a flexible metal 35 foil which is provided with a multiplicity of stamped in cup-like recesses (2), the openings (7) of which are closed. REPLACEMENT SHEET (RULE 26) WO 01/17764 - 13 - PCT/EPOO/08562

6. The sandwich panel as claimed in claim 5, characterized in that the covering layers (3, 4) are substantially planar. 5

7. The sandwich panel as claimed in claim 5, characterized in that the covering layers (3, 4) are curved and/or structured. 10

8. The sandwich panel as claimed in one of claims 5 to 7, characterized by at least one further flexible aluminum foil having a multiplicity of stamped-in cup-like recesses (2'). 15

9. The sandwich panel as claimed in claim 8, characterized in that the recesses (2) in one metal foil and the recesses (2') in the further aluminum foil extend in opposite directions. 20

10. The sandwich panel as claimed in one of claims 8 or 9, characterized in that a different number of recesses (2, 2') is formed in the two flexible metal foils. 25

11. A method for producing a body component, comprising the following steps: - forming a multiplicity of cup-like recesses, which point in one direction, in a flexible metal foil, 30 - forming a laminated structure by applying a covering layer to that side of the flexible metal foil on which the openings of the cup-like recess are located, - applying an adhesive to the end faces of the 35 recesses, - joining the laminated structure to a metal body sheet, the end faces of the laminated structure REPLACEMENT SHEET (RULE 26) WO 01/17764 - 14 - PCT/EPOO/08562 being adhesively bonded to the metal body sheet by means of the adhesive.

12. The method as claimed in claim 11, characterized 5 in that the laminated structure and the metal body sheet are joined by the application of pressure and the simultaneous supply of heat.

13. The method as claimed in claim 11 or 12, 10 characterized in that the adhesive is an encapsulated, heat-activatable adhesive system.

14. The method as claimed in one of claims 11 to 13, characterized in that, before the joining operation, 15 foam systems, which are activated during the joining, are introduced between the laminated structure and the metal body sheet.

15. The method as claimed in one of claims 11 to 14, 20 characterized in that the covering layer is an aluminum sheet.

16. A body component, having - a flexible metal foil (16), in which a 25 multiplicity of cup-like recesses (18), which point in one direction, are formed, - a covering layer (12) which is applied to that side of the flexible metal foil (16) on which the openings (28) of the cup-like recesses (18) 30 are located, - a metal body sheet (24), which is joined to the end faces (26) of the recesses (18) by means of an adhesive. 35

17. The body component as claimed in claim 16, characterized in that the metal foil (16) and the covering layer (12) consist of aluminum. REPLACEMENT SHEET (RULE 26)