Method for producing a fiber composite component for aerospace

Abstract

The invention relates to a method and a molding core for producing a fiber composite component (34), in particular in aerospace, comprising the following method steps: introducing a core sleeve (9) into a molding tool (2) for establishing an outer geometry of a molding core (27) to be formed; filling the core sleeve (9) that is introduced with a vacuum-fixable filling material (21); applying a vacuum to the core sleeve (9) and consequently vacuum-fixing the filling material (21) for forming the molding core (27); and at least partly laying at least one semifinished fiber product (33a, 33b) on the molding core (27) that is formed, for the shaping of the fiber composite component (34) to be produced.

Claims

1. A method for producing a fiber composite component, comprising: providing a molding tool; introducing a core sleeve into the molding tool for establishing an outer geometry of a molding core to be formed, wherein a cross section of the molding core is trapezoidal; providing reinforcing corner profiles in opposing corners of the molding tool, wherein the reinforcing corner profiles include an outer geometry that conforms to an inner geometry of the molding tool; filling the core sleeve with a vacuum-fixable filling material; applying a vacuum to the core sleeve to vacuum-fix the vacuum-fixable filling material, thereby forming a rigid molding core that is compressed within the core sleeve between the portions of the corner profiles, wherein the molding core is elongated and comprises a length along a first axis and a width along a second axis that is orthogonal to the first axis, wherein the length is greater than the width; opening the molding tool and removing the molding core, the core sleeve, and the corner profiles therefrom; applying a release layer to the core sleeve, thereby reducing adhesive attachment of a semifinished fiber composite product to the core sleeve, wherein the release layer is applied on a top surface of the core sleeve and is arranged between the core sleeve and the semifinished fiber composite product; arranging the molding core, the core sleeve, and the corner profiles which are free of semifinished fiber composite product on a planar surface of a base part comprising semifinished fiber composite products, wherein the molding core is arranged so that the first axis is substantially parallel to the planar surface on the base part, and wherein at least two corner profiles are arranged along the longitudinal axis of the molding core one after the other; and laying at least one semifinished fiber product over the molding core, the core sleeve, the corner profiles, and the planar surface of the base part for shaping the fiber composite component to be produced.

2. The method according to claim 1, wherein the filling of the core sleeve takes place by at least one of a gravitational force and a blower stream, acting on the vacuum-fixable filling material.

3. The method according to claim 1, wherein before filling, the core sleeve is held open by at least one of a gravitational force and by a first vacuum pump, acting on an outer surface of the core sleeve.

4. The method according to claim 1, wherein the vacuum for the vacuum fixing is monitored for quality assurance.

5. The method according to claim 1, wherein the vacuum-fixable filling material in the molding tool is compacted, shaken, or combination thereof before the vacuum fixing.

6. The method according to claim 1, wherein providing reinforcing corner profiles comprises providing a braided carbon fiber reinforced plastic (CRP) gusset comprising a carbon fiber reinforced plastic (CRP) braided tube with a centrally drawn-in fiber strand, which is pressed into a triangular shape or an extruded plastic gusset.

7. The method according to claim 1, wherein the molding tool is divided in a longitudinal direction of the molding core.

8. The method according to claim 1, wherein, after ending applying the vacuum, the fixable filling material is removed from the core sleeve.

9. The method according to claim 8, wherein the fixable filling material is removed by at least one of shaking out, flushing out, and extraction by suction method.

10. The method according to claim 1, further comprising at least partially curing the fiber composite component and removing the core sleeve from the at least partially cured portion of the fiber composite component.

11. The method according to claim 1, wherein the core sleeve is formed from an elastic or a flexible material.

12. The method according to claim 1, wherein the core sleeve comprises plastic.

13. The method according to claim 1, wherein the molding core is formed with at least one undercut.

14. The method according to claim 1, wherein the fixable filling material is a sand or a quartz sand.

15. The method according to claim 1, wherein the method for producing the fiber composite component takes a form of at least one of a prepreg and vacuum infusion process.

16. The method according to claim 12, wherein the core sleeve comprises polymide or a PTFE plastic.

17. The method according to claim 1, further comprising removing the corner profiles from the fiber composite component.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is explained in more detail below using preferred exemplary embodiments and with reference to the attached figures of the drawings, in which:

(2) FIG. 1 shows a state of the method in the production of a molding core according to an exemplary embodiment of the present invention that is given by way of example;

(3) FIG. 2 shows a further state of the method in the production of the molding core according to the exemplary embodiment that is given by way of example;

(4) FIG. 3 shows yet another state of the method in the production of the molding core according to the exemplary embodiment that is given by way of example;

(5) FIG. 4A shows a section along a sectional line A-A from FIG. 3 according to the exemplary embodiment;

(6) FIG. 4B shows a section along the sectional line A-A from FIG. 3 according to a further exemplary embodiment of the present invention;

(7) FIG. 5 shows a state of the method in the production of a fiber composite component according to the exemplary embodiment that is given by way of example; and

(8) FIG. 6 shows a further state of the method in the production of a fiber composite component according to the exemplary embodiment that is given by way of example.

(9) In the figures, the same reference numbers refer to identical or functionally identical components unless otherwise stated.

DETAILED DESCRIPTION OF THE INVENTION

(10) FIGS. 1 to 3 show a number of states of the method according to an exemplary embodiment of the present invention.

(11) Arranged in a device 1 is a molding tool 2. The molding tool 2 may have a cross section 3 such as that represented in FIG. 4A. The cross section 3 of the molding tool 2 is formed such that it is essentially trapezoidal. A wall 4 of the molding tool 2 is provided with a multiplicity of small holes 5, in order to prevent sucking in of the core sleeve 9. The introduction of a ventilating film between the core sleeve 9 and the wall 4 to ensure an evenly distributed vacuum is similarly conceivable.

(12) The holes 5 are connected by means of a channel 6 to a hose 7. The hose 7 is in turn connected to a first vacuum pump (not represented). The first vacuum pump makes it possible to generate a negative pressure in an interior space 8 of the molding tool 2.

(13) A preferably elastic and/or flexible core sleeve 9 is introduced into the interior space 8 of the molding tool 2. The core sleeve 9 is formed longitudinally with an upper opening with respect to the effective direction of gravitational force. The core sleeve 9 is preferably produced from a plastic, in particular a polyamide and/or a PTFE plastic. The core sleeve 9 is aligned with its longitudinal axis L along the longitudinal axis of the molding tool 2 and protrudes at its upper end, which has the opening 10, from a closable opening 11 of the device 1.

(14) Preferably, a portion of the core sleeve 9 that has the opening 10 is subsequently pushed through an opening 15 of a plate 12 and fastened there by means of a clamping ring 18.

(15) According to the present exemplary embodiment, the closable opening 11 of the device 1 is closed by the plate 12 and the latter is closed in a sealing manner with respect to the interior space 8 of the molding tool 2 by means of suitable fastening means 13a, 13b.

(16) Before or after that, the first vacuum pump is switched on to generate a vacuum in the interior space 8 of the molding tool 2. This has the effect that a wall 16a of the core sleeve 9 is sucked against an inner surface 17 of the molding tool. Consequently, the core sleeve 9 comes to lie with its wall 16a snugly against the inner surface 17 of the molding tool. The arrows 22 and 23 indicate the direction of flow of the air.

(17) The molding tool 2 is advantageously provided with such a number of holes 5 that the wall 16a of the core sleeve 9 lies completely against the inner surface 17 of the molding tool and against the plate 12 for closing the opening 11. Instead of holes, in the case of a multipart molding tool 2, gaps, in particular in the region of corners of the cross section of the molding tool, between the multiple parts may be used for applying the vacuum. A multipart molding tool 2 has the advantage of easy introduction of the core sleeve 9 and easy removal of the molding core 27 produced from the molding tool 2 and may be advantageously used for this invention.

(18) Subsequently, a vacuum-fixable filling material, for example quartz sand, is fed to the opening 10 of the core sleeve 9 by means of a feeding device 19. The feeding device 19 may be formed for example by a hopper 20, to which the quartz sand is fed by means of gravitational force and/or compressed air.

(19) The filling of the core sleeve 9 with quartz sand 21 is stopped as soon as the core sleeve 9 is adequately filled, that is to say for example just below the opening 10.

(20) A vacuum sealing device 24 is coupled in a sealing manner to the opening 10 of the core sleeve. The vacuum sealing device may in this case have at least to some extent the same components as the feeding device 19.

(21) In a further step, the first vacuum pump is switched off and then allows flowing of the air in the direction of flow opposite to that shown in FIG. 2, indicated by the arrow 25.

(22) Then, a second vacuum pump (not represented) is switched on and sucks air out of the core sleeve, indicated by the arrow 26, and consequently generates a second vacuum inside the core sleeve 9. The wall 16a of the core sleeve 9 then stretches itself firmly around the fixable quartz sand 21 and compresses it.

(23) On account of the prior pretensioning of the core sleeve 9 by applying the vacuum to the outer surface 16b of the core sleeve 9 by means of the first vacuum pump, the core sleeve 9 does not form any folds during the contraction by means of the second vacuum.

(24) The compression of the quartz sand 21 has the effect that the individual grains of the quartz sand engage in one another, and consequently the molding core 27 is formed. As a result of the low compressibility of the quartz sand, the outer shape of the molding core 27 changes only minimally under the effect of the contraction of the wall 16a of the core sleeve 9.

(25) In addition, the molding tool 2 may be shaken in the longitudinal direction of the core sleeve 9, for example before the application of the second vacuum, in order to achieve compaction, and consequently improved strength. This increases the resistance to point loads of the molding core 27 that is formed.

(26) The molding core 27 that is formed has the cross section 28 shown in FIG. 4A.

(27) In addition, as shown in FIG. 4B, reinforcing elements in the form of corner profiles 29a, 29b may be arranged within the core sleeve 9 before the application of the second vacuum.

(28) In a further step, according to the present exemplary embodiment, the opening 10 of the core sleeve 9 is closed, for example welded, by means of the vacuum sealing device. Alternatively, it may be provided that the vacuum remains connected for as long as vacuum fixing is required. Consequently, quality control can be carried out, for example the detection of leaks in the core sleeve 9. If the vacuum sealing device 24 is then moved away, for example upwards, the second vacuum is retained within the core sleeve 9. The plate 12 is then lifted off in a further method step. After the opening of the molding tool 2, the dimensionally stable molding core 27 is removed from it and arranged on a base part 31 comprising a number of fiber mats.

(29) FIGS. 5 and 6 show further states of the method in the production of a fiber composite component according to the exemplary embodiment that is given by way of example.

(30) Two molding cores 27 of an approximately trapezoidal cross section, which have been produced in particular by the method described above, are arranged with their base 32 lying on a base part 31. The base part 31 has at least one layer of a semifinished fiber product.

(31) In a further step, further semifinished fiber products are laid flat on the molding cores 27. The semifinished fiber products 33a, 33b thereby lie with a middle portion on the outer surface 16b of the molding cores 27 and with their ends on the base part 31, that is to say for example on the skin of an aircraft.

(32) Various production methods may be used for producing the fiber composite component. The infusion process is preferably chosen, in order to introduce a matrix, that is to say for example epoxy resin, into the semifinished fiber products 31, 33a, 33b. The prepreg process can similarly be used here.

(33) In a further step, the base part 31 is advantageously cured with the molding cores 27a, 27b and the semifinished fiber products 33a, 33b under the effect of heat and pressure in an oven or autoclave, depending on the process used. It is important here that the core sleeve 9 reliably withstands the process temperature and the process pressure.

(34) The semifinished fiber products 33a, 33b cure for example in a suitable oven or autoclave (not represented) to form stringers 35a, 35b. After curing, the at least partially cured fiber composite component 34 consequently has the two stringers 35a, 35b.

(35) In a further method step given by way of example, after the core sleeve 9 is opened at the end face, a suction tube 38 may be introduced into the opening 10 of the core sleeve 9. The suction tube 38 sucks the quartz sand 21 out of the core sleeve 9, and consequently out of the stringer, illustrated in an exemplary fashion in FIG. 6 for the stringer 35a.

(36) Once the quartz sand 21 has been largely removed, the core sleeve 9 can be drawn out of the stringer in the longitudinal direction, represented in an exemplary fashion in FIG. 6 for the stringer 35b. This is also possible whenever the stringer 35a, 35b has undercuts in the longitudinal direction, that is to say recesses in the stringers that extend transversely to the longitudinal direction of the stringers. Removal of the core sleeve 9 or the molding cores 27 from the mold is consequently ensured in an easy way. After that, the fiber composite component 34 can be further processed or used directly.

(37) The invention is not restricted to the specific method represented in the figures for producing a fiber composite component in aerospace.

(38) For example, the individual sequence of individual method steps of the production method according to the invention can be changed in various ways. The form taken by the individual method steps can also be modified. For example, flushing out of the quartz sand instead of extraction by suction may be carried out before the removal of the core sleeve from the mold. The molding core may also be drawn or pressed out of the stringer as a whole in the longitudinal direction of the said stringer.

(39) Furthermore, the geometry of the molding core can be modified in various ways.

(40) Furthermore, it is also possible for a number of molding cores to be used to form a single molding core, around which fiber composite mats are placed. This allows a more complex geometry to be created by means of the multiplicity of molding cores and consequently more complex fiber composite components to be produced.