METHOD FOR PRODUCING A COMPONENT FROM A FIBER-COMPOSITE MATERIAL

Abstract

The invention relates to a method for producing a component from a fibre composite material by deforming a thermoplastic organic sheet (2) in a membrane press (1), wherein a mould (4) is arranged in the membrane press (1), wherein at least one organic sheet (2) is positioned on or in the mould as a work piece, and wherein an elastically flexible membrane (11) is flexibly stretched over the mould (4) with the interposition of the organic sheet (2). In this way, the organic sheet (2) is deformed with the formation of the component, wherein the membrane (11) is applied with an under-pressure on the side facing the mould, and with an over-pressure on the side facing away from the mould, such that the organic sheet (2) is shaped onto the mould.

Claims

1. A method of making a part from a fiber composite material, the method comprising the steps of providing a mold a membrane press and placing at least one organic sheet onto or against the mold as a workpiece, stretching an elastically flexible membrane over the mold on the organic sheet, and deforming the organic sheet so as to form the part by applying a subatmospheric pressure to the membrane on its face turned toward the mold and applying a superatmospheric pressure to the face turned away from the mold and thereby shaping the organic sheet against the mold.

2. The method defined in claim 1, further comprising the step of: heating the organic sheet before and/or after being placed into the press.

3. The method defined in claim 1, further comprising the step of: heating the mold or at least a surface thereof turned toward the organic sheet before and/or during the deformation.

4. The method defined in claim 1, further comprising the step of: heating the fluid medium with which superatmospheric pressure is applied to the membrane.

5. The method defined claim 1, wherein the superatmospheric pressure is at least 10 bar.

6. The method defined in claim 1, wherein the organic sheet is a prefabricated semifinished product composed of a plurality of organic layers that are placed together before being introduced into the press.

7. The method defined in claim 6, wherein the organic layers have different fiber orientations.

8. The method defined in claim 6, wherein the organic layers are of different sizes in order to form an organic sheet whose thickness varies over its surface.

9. The method defined in claim 1, wherein the membrane is made of silicone.

10. The method defined in claim 1, wherein the membrane has a thickness of at least 1 mm and/or a stretch-to-break of at least 500%.

11. The method defined in claim 6, wherein the organic layers are offset relative to one another during the deformation, thereby altering an edge geometry of the part.

12. A membrane press for making a part from a fiber composite material, the press comprising: a lower element carrying a mold, an upper element having a pressurizable hood that can be sealed off against the lower element, at least one cylinder that acts on the upper element and/or the lower element to press the elements together, a membrane that can be stretched over the mold, a vacuum pump for applying a subatmospheric pressure to one face of the membrane, and a pressure pump for applying a superatmospheric pressure to the other face of the membrane.

13. The press defined in claim 12, wherein the membrane is secured to the lower element and stretched over the mold.

14. The press defined in claim 12, wherein the membrane is secured when elastically stretched to the pressurizable hood.

15. The press defined in claim 14, wherein the membrane forms with the hood a closed upper chamber above the mold and connected to the pressure pump, and, when the upper element is pressed against the lower element, the membrane forms with the lower element a closed lower chamber connected to the vacuum pump.

Description

[0030] The invention is explained in further detail below with reference to a schematic drawing that illustrates only one embodiment.

[0031] FIG. 1 is a simplified view of a membrane press according to the invention,

[0032] FIG. 2 is a view showing the press of FIG. 1 in another functional position,

[0033] FIG. 3 is a view like FIG. 1 but showing a modified embodiment of the press,

[0034] FIG. 4 is a view showing the press of FIG. 3 in another functional position,

[0035] FIG. 5 shows a first embodiment of a process for shaping a multilayer organic sheet, and

[0036] FIG. 6 shows a second embodiment of a process for shaping a multilayer organic sheet.

[0037] The drawing shows a membrane press 1 for making a part from a fiber composite material. In such a membrane press, a part is manufactured from a fiber composite material by shaping of a thermoplastic organic sheet 2. In this embodiment, the membrane press 1 has a lower element 3 that is embodied as a press table on which a mold 4 is provided as a negative mold of the part to be made. In addition, the press 1 has an upper element 5 that has a pressurizable hood 6 that can be sealed off against the lower element 3. For this purpose, a lower, circumferential front edge 7 of the pressurizable hood 6 can be placed on the press table and is provided with a seal ring 8. A cylinder 9 acts on the upper element 5, and here a piston 10 of the cylinder 9 is connected to the pressurizable hood 6 so that the pressurizable hood 6 is pressed with the cylinder 9, more particularly the piston 10 thereof, against the lower element 3. In addition, the membrane press 1 is equipped with an elastically flexible membrane 11 that can be stretched over the mold 4. Furthermore, a vacuum pump 12 is provided that here is connected to the lower element 3. In addition, a pump 13 capable of generating a superatmospheric pressure is provided that, in this embodiment, is connected to the upper element 5 and/or to the pressurizable hood 6.

[0038] An organic sheet 2 is shaped by placing it onto the mold 4, and the membrane 11 is flexed and stretched over the mold 4 atop organic sheet 2.

[0039] The organic sheet is deformed so as to form the part by application of a subatmospheric pressure by the vacuum pump 12 to the membrane 11 on its face turned toward the mold 4 and by application of a superatmospheric pressure by a pressure pump 13 to its face turned away from the mold 4, so that the organic sheet 2 is shaped against the mold to form the part.

[0040] The organic sheet 2 is heated before being placed into the press 1. In addition, preferably the mold 4 or at least a surface thereof turned toward the organic sheet 2 is heated before and/or during the deformation. Finally, it is advantageous if the fluid medium with which superatmospheric pressure is applied to the membrane is heated. To achieve this, a heater 14 is shown in the drawing. Heaters for heating the organic sheet and for heating the mold are not shown.

[0041] FIG. 1 shows a first embodiment of such a membrane press in which the membrane 11 is secured to the lower element 3 and stretched over the mold 4. FIG. 1 shows the press after the organic sheet 2 has been placed onto the mold 4 and the membrane 11 has been stretched over the mold 4 with interposition of the organic sheet 2. In addition, after placing the organic sheet 2 and after stretching the membrane 11 on the lower element 3, the upper element 5 is lowered and sealed off. Subatmospheric pressure can be generated using the vacuum pump 12 before and/or after lowering of the upper element. After the upper element 5 has been lowered and sealed off against the lower element 3, the superatmospheric pressure is applied to the interior of the pressurizable hood 6. The compressive force with which the membrane press is held closed as the internal pressure increases can be increased successively with rising of the internal pressure and thus adapted thereto. FIG. 2 shows the press after the superatmospheric pressure and the subatmospheric pressure have built up, with the organic sheet 2 deformed.

[0042] FIGS. 3 and 4 show a modified embodiment of such a membrane press in which the membrane is not secured to the lower element 3 but rather to the upper element 5, namely to the pressurizable hood 7 thereof, and elastically stretched. After placing the organic sheet 2 onto the mold 4, the pressurizable hood 6 is lowered and, at the same time, the membrane is stretched over the mold with interposition of the organic sheet 2 (FIG. 4). After the press has been closed, the subatmospheric pressure and the superatmospheric pressure are built up, whereby the organic sheet 2 is deformed and the part produced.

[0043] The organic sheet 2 can be composed of a plurality of individual organic layers 2a that are laminated together to form the organic sheet 2 and deformed in the press. The geometry of the layers 2a can be coordinated with one another such that the individual layers 2a are offset relative to one another during the deformation, thereby altering the edge geometry of the part. This option is illustrated in FIGS. 5 and 6. According to FIG. 5, the individual layers 2a are placed together to form an organic sheet 2 with straight edges. During the deformation, the individual layers are offset relative to one another, so that a part with beveled edges is produced.

[0044] By contrast, FIG. 6 shows an embodiment in which the individual layers 2a of the organic sheet 2 do not lie flush over one another, but rather have offset outer edges so that a part with straight edges without bevels is then formed during the deformation.