EP1673486B1 - Method for the production of a composite material and the utilization thereof - Google Patents

Description

The invention relates to a method for producing a composite material.

Modern gas turbines, in particular aircraft engines, must meet the highest demands in terms of reliability, weight, performance, economy and service life. In recent decades, aircraft engines have been developed, particularly in the civil sector, which fully meet the above requirements and have achieved a high degree of technical perfection. Among other things, the selection of materials and the search for new, suitable materials play a decisive role in the development of aircraft engines.

The most important materials used today for aircraft engines or other gas turbines are titanium alloys, nickel alloys (also called superalloys) and high-strength steels. The high-strength steels are used in particular for shaft parts and gear parts and for compressor casings and turbine casings. Titanium alloys are typical materials for compressor parts, nickel alloys are suitable for the hot parts of the aircraft engine.

A very promising group of future generations of aircraft engine material is so-called fiber-reinforced composites. Modern composites have a carrier material, which may be formed as a polymer, a metal or a ceramic matrix, as well as embedded in the carrier material fibers.

The present invention relates to the production of a composite material in which the carrier material is formed as a metal matrix. Such a material is also called a metal matrix composite material - called MMC for short. For high-strength MMC materials using titanium as the substrate, component weight can be reduced by up to 50% over traditional titanium alloys. Reinforcements used are fibers having high strength and high modulus of elasticity.

Such fiber-reinforced composite materials are already known from the prior art. So revealed the EP 0 490 629 B1 a preform for a composite with a film, the film having a groove and a thread-like reinforcement disposed in the groove, and wherein the preform has the shape of a ring or a disc. To produce a multilayer composite structure, according to the EP 0 490 629 B1 proceeded so that several such preforms are superimposed, wherein the preforms are solidified under heat and pressure to form a completely dense composite material. Other composites and methods of making the same are known from EP 0 909 826 B1 , of the US 4,697,324 and the US 4,900,599 known.

The document US 2002/0031678 A1 also discloses a method for making a composite over film-like preforms having a groove and a reinforcing fiber inserted into the groove. The groove is cut by cutting into the film, wherein the film is clamped on a rotating tool or workbench. For the completion of the actual composite material, several films provided with fibers are stacked on each other and consolidated materially. Safe testing of the multilayer material for fiber breaks or material cracks is practically impossible.

On this basis, the present invention is based on the problem to provide a novel method for producing composite materials, with which an exact position of the fibers and a low scrap of material can be achieved.

This problem is solved by a method for producing a composite material having the features of patent claim 1. In this case, slices of carrier material and at least one fiber embedded in the carrier material are joined together. According to the invention, each slice of fiber is consolidated separately, then the consolidated slices are stacked and joined by a joining step.

Preferably, a recess is introduced into the disc, the depth of which is greater than the diameter of the fiber, such that, when a fiber is inserted into the recess, webs of carrier material protrude beyond the fiber.

The disks are stacked in such a way that the fibers of the stacked disks protrude radially differently into the carrier material in a radially outer section for strength-optimizing toothing.

Preferred embodiments of the invention will become apparent from the dependent subclaims and the following description.

Fig. 1:

eine Scheibe aus Trägermaterial in schematisiertem Querschnitt;

Fig. 2:

einen stark vergrößerten Ausschnitt aus der Scheibe gemäß Fig. 1 mit einer in die Scheibe eingebrachten Ausnehmung;

Fig. 3:

die Anordnung gemäß Fig. 1 mit einer in der Ausnehmung eingelegten Faser;

Fig. 4:

eine Scheibe aus Trägermaterial mit einer eingebetteten Faser in schematisiertem Querschnitt;

Fig. 5:

das Detail V der Fig. 4;

Fig. 6:

mehrere übereinander angeordnete Scheiben aus Trägermaterial mit eingebetteten Fasern in schematisiertem Querschnitt,

Fig. 7:

einen Ausschnitt aus der Anordnung gemäß Fig. 6; und

Fig. 8:

einen erfindungsgemäßen Verbundwerkstoff in schematisiertem Querschnitt.

Embodiments of the invention will be described, without being limited thereto, with reference to the drawings. In the drawing shows:

Fig. 1:

a disc of carrier material in a schematic cross section;

Fig. 2:

a greatly enlarged section of the disc according to Fig. 1 with a recess made in the disc;

3:

the arrangement according to Fig. 1 with a fiber inserted in the recess;

4:

a disc of carrier material with an embedded fiber in a schematic cross section;

Fig. 5:

the detail V of the Fig. 4 ;

Fig. 6:

several superimposed discs of carrier material with embedded fibers in a schematic cross-section,

Fig. 7:

a section of the arrangement according to Fig. 6 ; and

Fig. 8:

a composite material according to the invention in a schematic cross section.

With reference to Fig. 1 to 8 The details of the composite material according to the invention and of the method according to the invention for producing the composite material will be described in greater detail below.

The composite material produced according to the invention has a carrier material made of titanium or a titanium alloy as well as a plurality of fibers embedded in the carrier material. The fibers are preferably silicon carbide ceramic fibers. The composite material according to the invention is formed from a plurality of discs of carrier material, wherein a fiber is embedded in each disc. Several such disks with a fiber embedded therein are stacked and bonded together to form the composite. For embedding the fiber in the respective disc of carrier material, a recess is made in the disc. In the recess, the corresponding fiber is inserted and surrounded on all sides by carrier material, so that the fiber is embedded in the disc.

Fig. 1 shows a disc 10 of support material, namely titanium, in a highly schematic cross-section. In a central region, the disc 10 has a bore 11th

To produce the composite material, a recess is introduced into a front side 12 of the pane 10 after a first step of the method according to the invention. Fig. 2 shows a greatly enlarged detail of the disc 10 in the region of the end face 12. In the recess 13, which is introduced into the end face 12 of the disc 10, is a spiral groove. The spiral groove therefore extends exclusively on an end face 12 of the disc 10 from the inside to the outside.

After the spiral-shaped recess 13 has been introduced into the upper side 12 of the disk 10, a fiber 14 is inserted into the spiral-shaped recess 13. Fig. 3 can be seen that webs 15 protrude from carrier material with fiber 14 inserted over the fiber 14. The depth of the spiral recess 13 is therefore greater than the diameter of the fiber 14.

Through the recess 13 an exact guidance for the fiber 14 is provided. The position of the fiber 14 within the disk 10 or within the carrier material is thereby predetermined exactly.

In a further step of the method according to the invention, the arrangement according to Fig. 3 subjected to a superplastic forming process. For this purpose, the disc 10 or the substrate is heated to a forming temperature and uniaxial pressing the webs 15 are so superplastic reshaped that subsequently the fiber 14 in the sense of Fig. 5 Surrounded on all sides by carrier material and thus the fiber 14 is embedded in the carrier material. Fig. 5 can be seen that the position of the fiber 14 is maintained even after the superplastic forming of the webs 15. In superplastic forming, the carrier material is compacted.

Fig. 4 shows a disc 10 made of carrier material with the fiber 10 embedded in the disc 10 in a highly schematic cross-section. The fiber 14 is surrounded on all sides by carrier material and thus embedded in the carrier material.

For the production of the actual composite material in a next step of the method according to the invention in the sense of Fig. 6 a plurality of discs 10 with embedded in the discs 10 fibers 14 arranged one above the other and stacked in this manner annular or cylindrical. The stacked and stacked disks 10 are then joined by diffusion welding under low axial pressure or connected to each other. This will ultimately provide the composite.

Before the stacking of the discs 10 in the sense of Fig. 6 Preferably, an examination of the discs 10 with the fibers 14 embedded in the discs 10 for cracks in the carrier material and for breaks in the fibers 14. This review can done with ultrasound, X-ray or tomography. If such a crack or break found, the disc 10 is discarded. If it is determined during the inspection that there is no crack or break in the fiber 14, then the disc 10 can be used for stacking.

Fig. 7 shows a section of the arrangement according to Fig. 6 in the range of three superimposed and interconnected slices 10. So can Fig. 7 it can be seen that the fiber 14 embedded in a disk 10 extends radially offset from the fibers 14 of the two adjacent disks 10. As a result, a hexagonal packing of the fibers 14 can be achieved. As Fig. 7 can be removed, a fiber 14 extends spirally within a disc 10, that in cross-section, the resulting center points of the fiber 14 of a disc 10 between the corresponding centers of the fiber 14 of an adjacent disc 10 are arranged.

Fig. 6 It can be seen that each fiber 14 within each disc 10 terminates at a distance to an outer, lateral end of the respective disc. According to Fig. 6 this distance is different for each slice. Adjacent to the inner opening 11, however, the lateral distance of the fibers 14 to the opening 11 is the same. Due to the different lateral distances between the fibers 14 and the radially outer, lateral end of the discs 10, gradual changes in the elastic properties of the composite can be achieved. Furthermore, a toothing between the unreinforced and fiber reinforced areas of the composite is achieved, which positively affects the strength properties.

Fig. 8 shows a highly schematic cross section through a composite material according to the invention. This was prepared as described above. According to Fig. 8 In an internal section 16 of the composite material, the fibers 14 are embedded in the carrier material. In an outer section 17, however, only the carrier material is present. This means that in the outer portion 17 is present only titanium. This is advantageous if the composite material is subjected to further processing, for example by milling should. When milling, namely the fibers 14 may not be damaged. A subsequent milling of the composite is therefore only in the range of section 17 into consideration, in which only the carrier material is present. Furthermore, can Fig. 8 again the detail be taken that the fibers 14 adjacent to the inner opening with the same distance from the opening end, at the outer end, however, adjacent to the section 17, in which only the carrier material is present, this distance is formed differently. The radial gradation of the fibers 14 in the section 16 relative to the section 17 effects a strength-optimizing toothing with the carrier material.

According to the above-described method according to the invention for the production of the composite material, the procedure is thus roughly as follows:

In a first step, a plurality of discs made of carrier material, namely titanium, on a front side thereof provided with a spiral-shaped recess. In a second step, a fiber made of silicon carbide is inserted into this spiral recess. Subsequently, in a third step, the disc with the fiber inserted into the disc is consolidated by superplastic forming. Subsequently, the fiber is surrounded on all sides by carrier material or embedded in the carrier material. In a next step, the discs thus produced with fibers embedded in the discs are checked for cracks in the carrier material and fractures in the fibers. If this test shows that there is neither a crack nor a fiber break, the corresponding discs are stacked in rings. The stacking of a plurality of rings is then subjected to a diffusion welding in a further step of the method according to the invention, so that adjacent disks are joined together. After completion of this joining step can be done in a further step, a finishing of the composite material, for example by milling.

The inventive method is reliable and inexpensive. The method according to the invention is a fully automated process with integrated verification and thus quality assurance. Since each disc can be inspected for quality, defects in the composite can be timely be recognized and thus avoided. Scrap is reduced with it. Another advantage is the fact that an exact position of the fibers in the composite material is predetermined and adhered to. In addition to the preferred spiral arrangement of the fibers in the composite and more complex fiber guides, for example, star-shaped fiber guides are possible. In the invention can be dispensed with a titanium coating of the fibers, as required in the prior art. Another advantage is that no extremely long fibers need to be used. By guiding the fibers in recesses, fibers of finite length can be used.

The composite material produced according to the invention is accordingly distinguished by an exact position of the fibers within the carrier material. The composite material is formed by a plurality of joined discs of carrier material, wherein within each disc a spirally extending fiber is embedded. The fibers terminate at a distance from a lateral, radially outer end of the composite, so that in an outer region of the same only the carrier material is present, in which area a subsequent milling of the composite material can take place.

For the sake of completeness, it should be noted that a plurality of fibers can also be embedded in a recess, and that a plurality of interleaved recesses can also be introduced into a disk, wherein each of these recesses can in turn receive one or more fibers. However, the illustrated embodiment, in which each disc has a recess for receiving a fiber, is preferred.

The composite material produced according to the invention is particularly suitable for use as a material in the manufacture of rings with integral blading for aircraft engines, which are also referred to as bladed rings (blings).

Claims (8)

1. Method for the production of a composite material assembled from a plurality of disks (10) of substrate, wherein each disk (10) is preferably provided with at least one recess (13) to accommodate at least one fibre (14), comprising the following steps:

   a) provision of a plurality of disks (14) of substrate;

   b) creation of at least one recess (13), preferably in each disk (10), followed by the placement of at least one fibre (14) in each recess (13) of the relevant disk (10);

   c) consolidation of the relevant disk (10), whereby the fibre(s) (14) is (are) surrounded on all sides by the substrate or embedded into the substrate of the relevant disk (10);

   d) stacking of consolidated disks (10);

   e) joining the stacked disks (10) in a joining step.
2. Method according to claim 1, characterised in that in step b) a recess (13) is created in the disk (10), the depth of which is greater than the diameter of the fibre (14), so that, following the placement of the fibre (14) in the recess (13), webs (15) of substrate project above the fibres (14).
3. Method according to claim 1 or 2, characterised in that in step c) the substrate with the fibre(s) (14) placed therein is subjected to a superplastic forming process, so that the fibre(s) (14) is (are) surrounded by substrate on all sides.
4. Method according to any of claims 1 to 3, characterised in that in step d) the disks (10) of substrate with at least one fibre (14) embedded therein are placed on top of one another and stacked in particular to form a ring or a hollow cylinder.
5. Method according to any of claims 1 to 4, characterised in that in step d) the disks (10) are stacked such that the fibres (14) of the stacked disks (10) extend into the substrate to different degrees in a radially outer section (17) to provide a strength-optimising keying.
6. Method according to any of claims 1 to 5, characterised in that in step e) the stacked disks (10) are joined by diffusion welding.
7. Method according to any of claims 1 to 6, characterised in that the disks (10) of substrate with at least one fibre (14) embedded therein are, before being joined to other disks, checked for breaks in the fibre(s) or cracks in the substrate and in that the disk is rejected on detection of a crack or break.
8. Method according to any of claims 1 to 7 for the production of rotationally symmetrical, annular or disk-shaped components with integrated blading, i.e. of so-called bladed rings (blings) or bladed disks (blisks).

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