METHOD AND PRESS FOR MAKING A PRESS FROM FIBER COMPOSITE

Abstract

The invention relates to a method and a press for producing a component from a fiber composite material by deforming a thermoplastic semi-finished product, in particular an organic sheet (2), in a membrane press (1), wherein a mold (4) has been or is arranged in the membrane press (1), wherein at least one semi-finished product/organic sheet (2) is positioned on top of or against the mold as a workpiece, and wherein an elastically stretchable membrane (11) is preloaded while stretched over the mold (4) with the semi-finished product/organic sheet (2) arranged therebetween. At the same time, the semi-finished product/organic sheet (2) is deformed in order to form the component, in that a vacuum is applied to the membrane (11) on the side facing the mold and a positive pressure is optionally additionally applied to the membrane on the side facing away from the mold such that the semi-finished product/organic sheet (2) is shaped onto the mold. A mold is used which is permeable to air at least in some areas and which is produced, for example, from porous aluminum.

Claims

1. A method of making a part from fiber composite by deformation of a thermoplastic semifinished product in a membrane press, the method comprising the steps of: providing in the membrane press a mold that is at least partially air permeable; placing a semifinished product onto or against the mold as a workpiece; flexibly stretching an elastic membrane over the mold to form a closed space containing the semifinished product; and deforming the semifinished product to form the part by drawing air out of the space through the partially air-permeable mold and thereby applying a subatmospheric pressure to the membrane on its face turned toward the mold, so that the semifinished product is shaped against the mold.

2. The method defined in claim 1, wherein the mold is made of a porous material.

3. The method defined in claim 1, further comprising the step, in order to shape the semifinished product, of: applying to the membrane on the face turned away from the mold by a superatmospheric pressure that is at least 10 bar.

4. The method defined in claim 1, further comprising the step of: heating the semifinished product before or after placement into the press.

5. The method defined in claim 1, further comprising the step of: heating the mold or at least its surface turned toward the semifinished product before or during the deformation.

6. The method defined in claim 3, further comprising the step of: heating a fluid medium that applies the superatmospheric pressure to the membrane.

7. The method defined in claim 1, further comprising the step of: using an organic sheet as the semifinished product.

8. The method defined in claim 7, wherein the semifinished product is a prefabricated semifinished product that is composed of a plurality of layers that are placed together before being placed into the press.

9. The method defined in claim 1, wherein the membrane is made of silicone or has a thickness of at least 1 mm, or a stretch-to-break of at least 500%.

10. A press for making a part from fiber composite, the press comprising: an at least partially air-permeable mold; a lower element against/on which the mold and a thermoplastic sheet atop the mold are supported; an upper element having a pressure case that can be sealed against the lower element; a press cylinder that acts on the upper element or on the lower element, to push the elements together; a membrane that can be stretched over the mold between the elements; and a vacuum pump that applies a subatmospheric pressure through the partially-air permeable mold to one face of the membrane and thereby press the membrane down against the sheet and thereby deform the sheet to conform to a shape of the mold.

11. The press defined in claim 10, wherein the mold is made at least in some areas of a porous light metal.

12. The press defined in claim 10, further comprising: a superatmospheric pressure pump that can apply a superatmospheric pressure to the other face of the membrane.

13. The press defined in claim 10, wherein the membrane is secured to the lower element and can be stretched over the mold, or is secured in an elastically biased manner on the upper element.

14. The press defined in claim 10, wherein the mold is at least partially formed of a porous material having a filter mesh of from 5 m to 250 m or a pore size of from 0.1 mm to 3 mm.

15. The press defined in claim 10, wherein the mold is at least partially made of porous aluminum.

Description

[0035] The invention is explained in further detail below with reference to a schematic drawing, that illustrates only one embodiment. In the figures,

[0036] FIG. 1 is a simplified view of a membrane press according to the invention,

[0037] FIG. 2 shows the press of FIG. 1 in another functional position,

[0038] FIG. 3 shows a modified embodiment of the press according to FIG. 1,

[0039] FIG. 4 shows the press pf FIG. 3 in another functional position,

[0040] FIG. 5 shows a first embodiment of a process for shaping a multilayer organic sheet, and

[0041] FIG. 6 shows a second embodiment of a process for shaping a multilayer organic sheet.

[0042] The figures show a membrane press 1 for making a part from fiber composite. In such a membrane press, a part is manufactured from fiber composite by shaping a thermoplastic semifinished product, for example an organic sheet 2. Here, the membrane press 1 has a lower element 3 formed as a press table supporting a mold 4 that is a negative of the part to be manufactured. Moreover, the press 1 has an upper element 5 that has a hood-like pressure case 6 that can be sealed against the lower element 3. For this purpose, the lower, annular front edge 7 of the pressure case 6 that can be placed on the press table is provided with a circumferential seal 8. A press cylinder 9 acts on the upper element 5; here, the piston 10 of the press cylinder 9 is connected to the pressure case 6 so that the pressure case 6 is pressed by the cylinder 9, more particularly the piston 10 thereof, against the lower element 3. Moreover, the membrane press 1 is equipped with an elastic 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. Moreover, a superatmospheric pressure pump 13 can be optionally provided that here is connected to the upper element 5 and/or to the pressure case 6.

[0043] To shape an organic sheet 2, it is placed on the mold 4, and the membrane 11 is flexed and stretched over the mold 4 on top of the organic sheet 2.

[0044] The organic sheet is deformed so as to deform the part by applying a subatmospheric pressure by the vacuum pump 12 to the face of the membrane 11 facing the mold 4 and by applying a superatmospheric pressure by a superatmospheric pressure pump 13 to the face turned away from the mold 4, so that the organic sheet 2 is shaped against the mold to form the part.

[0045] The organic sheet 2 is heated before being placed into the press 1. Moreover, the mold 4 or at least its surface facing the organic sheet 2 is heated before and/or during the deformation. Finally, it is advantageous if the fluid medium that applies superatmospheric pressure to the membrane is heated. To achieve this, a heater 14 is shown schematically in the figures. Heaters for heating the organic sheet and for heating the mold are not shown.

[0046] 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. Moreover, after placement of the organic sheet 2 and after the stretching of the membrane 11 on the lower element 3, the upper element 5 is lowered and sealed off. The 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 against the lower element 3, the superatmospheric pressure is applied to the interior of the pressure case 6. A provision can be made that the compressive force that holds the membrane press closed as the internal pressure increases is increased successively with rising of the internal pressure and thus adapted thereto. FIG. 2 shows the press after superatmospheric pressure and subatmospheric pressure have built up, with the deformed organic sheet 2.

[0047] 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 pressure case 7 [6] thereof, and elastically biased. After placement of the organic sheet 2 onto the mold 4, the pressure case 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 so that the organic sheet 2 is deformed and the part made.

[0048] The organic sheet 2 can be composed of a plurality of individual organic sheet layers 2a that are placed 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 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 square edges. During deformation, the individual layers are offset relative to one another, so that a part with beveled edges is made.

[0049] By contrast, FIG. 6 shows an embodiment in which the individual layers 2a of the organic sheet 2 are not flush with one another, but rather form an angled edge so that a part with a square edge without a bevel is then created during deformation.

[0050] In principle, the illustrated press can be used to shape not only organic sheets but other thermoplastic semifinished products as well.

[0051] According to the invention, the mold 4 is made of a porous material, particularly of aluminum. A particular advantage of this embodiment is the application of a full-surface vacuum over the entire surface to be shaped.

[0052] In the context of the invention, flat or shaped parts such as aircraft wings, flaps for aircraft wings, etc., can be especially preferably made.

[0053] The figures have been described with reference to the preferred use of organic sheets and/or organic sheet layers. However, other thermoplastic, semifinished (fiber composite) products and, in particular, semifinished products composed of a plurality of individual layers that are placed loosely (in non-consolidated form) into the press can also be processed in the manner shown.