METHOD FOR PRODUCING A PARTIALLY FLAT FROM A FIBER COMPOSITE MATERIAL

Description

TECHNICAL FIELD

[0001] The invention relates to a method for producing a component and to such a component. BACKGROUND OF THE INVENTION

[0002] Many different processes have been established for the production of components made of fiber-reinforced plastics. Typically, large-format components, such as fuselage shells for commercial aircraft, are manufactured using molds onto which a fiber fabric is applied and cured. The fiber fabric can be generated using automated devices. Individual fiber webs or fiber mats are gradually applied, making it easy to create customized thicknesses and fiber patterns. The fabric applied to the mold is subjected to pressure and often heating, causing the matrix material surrounding the fibers to harden, thus producing a rigid component.

[0003] In addition to the use of thermosetting resin as a matrix material, thermoplastic matrix materials are also known. Similar methods and processes can be used for these.

[0004] Due to the individual fiber and thickness distributions, generating fiber layups for the production of large-format components is very complex and time-consuming. Furthermore, high demands are placed on automated fiber deposition devices, which increase with increasing component dimensions. While manufacturing processes for producing fiber composite components at higher speeds are known, these are only capable of producing components with a constant thickness.

[0005] EP 1 899 149 A1 describes a method for manufacturing a shell-shaped component made of carbon fiber-reinforced plastic with local reinforcement zones and stiffening elements, such as fuselage or wing shells of aircraft. It involves arranging hardened doubles on a partially cured shell, applying hardened stiffening elements, and placing partially cured angle brackets against the stiffening elements. After curing, the component is created, which has reinforcement zones and stiffening elements. SUMMARY OF THE INVENTION

[0006] The scope of the protection is determined by the subject matter of the main claims. Further developments can be found in the subclaims. The invention is defined in claim 1 and claim 8.

[0007] The object of the invention is to provide a manufacturing method for producing components made of fiber composite materials at higher speed and with variable thickness.

[0008] It is an object of the invention to propose a method for producing a large-format component in which, despite locally different component thicknesses, manufacturing processes that are as continuous as possible can be used, which can provide components made of a fiber composite material at high speed and quality.

[0009] The object is achieved by a method for producing a component according to claim 1. Advantageous further developments and embodiments can be found in the subclaims and the following description.

[0010] A method according to claim 1 for producing a component is proposed.

[0011] The first planar fabric thus has a single, consistent thickness throughout. At the same time, the first planar fabric also determines the surface area of the component to be produced by the method according to the invention. The first planar fabric is therefore to be understood as a type of base that provides a smooth outer skin, particularly in the manufacture of an aircraft fuselage shell.

[0012] Due to its simple geometry, the production of such a first flat fabric can be achieved using a manufacturing process that is particularly efficient, fast, and cost-effective. For example, a process based on a double-belt press is suitable, in which impregnation or resin impregnation and consolidation are carried out in a single step.

[0013] Alternatively, the pre-impregnated fiber ribbons can be deposited in an automated process, for example, using AFP (Automated Fiber Positioning). The individual resin-coated fiber ribbons could be bonded together using ultrasound, laser irradiation, or localized heating to create a closed composite.

[0014] Another alternative could be an automated fiber positioning process ("AFP"). Here, too, individual, pre-impregnated fibers could be bonded together using ultrasound.

[0015] To locally influence the component thickness, one or more second flat fabrics are produced. In this context, it should be noted that the first fabric determines the minimum thickness of the component. A reduction in the component thickness cannot be achieved; only an increase in the component thickness can be achieved by arranging the second fabrics. The thickness of the first fabric therefore corresponds to the smallest local thickness of the component to be manufactured.

[0016] The same processes can be used to produce the second scrim as for the first. However, due to the multitude of possible variations of the second scrim, a double-belt press may not necessarily be preferable. Consequently, automated deposition processes can be used, allowing the production of highly customized, small-format second scrims. Consolidation or curing is not necessarily required. Rather, individual elements can be bonded together using ultrasound.

[0017] To manufacture the component, the second fabrics are positioned in those areas of the inner surface of the first fabric where the local thickness must be increased compared to the local minimum thickness, for example, due to anticipated structural and mechanical loads. A mold capable of accommodating these components is used to assemble the individual fabrics.

[0018] The molds that are suitable for this purpose can be implemented in different ways. On the one hand, molds with a mold surface that accommodates the first fabric with its outer side are conceivable. All other components are arranged on a side of the mold facing away from the mold surface. Other molds, however, can have a mold surface or the like that directly accommodates, for example, the stiffening components mentioned below, onto which the second fabrics and the first fabric are then arranged. This will be discussed in more detail with reference to further embodiments below.

[0019] Finally, the composite of the first and second layers is consolidated, at least by applying pressure. This means that the composite is placed between the mold and another device, and consolidation is achieved, particularly by pressing. This is often accompanied by heating. Whether using a thermoplastic matrix material or a thermosetting resin, this ultimately results in a consolidated component.

[0020] The particular advantage of the method according to the invention is that a very large base part can be manufactured in a separate, highly efficient, and rapid process, after which more customized additional second fabrics used to increase thickness can be manufactured and attached in a significantly smaller format using automated processes. Overall, the component manufacturing process is significantly simplified because very large-format fiber deposition devices are no longer necessary, which are very cost-intensive due to the size of the components to be manufactured when high precision is required even over large component dimensions. Likewise, the method according to the invention allows even larger-format components to be manufactured than with currently known methods. It is conceivable that fuselage shells or fuselage shell halves with a length of well over 20 m could be manufactured using such a process.The design and configuration of such components can, however, be influenced by the method according to the invention by adapting the topology of the fiber structure to simplify production.

[0021] At this point, it should be noted that the individual layers, i.e. the first layers and / or the second layers, preferably have a symmetrical layer structure so that tension or deformation is avoided.

[0022] In an advantageous embodiment, the at least one first planar layer comprises an even number of first planar layers.

[0023] The at least one first layer and the second layers are preferably made of a thermoplastic, fiber-reinforced plastic. The matrix material can therefore be a thermoplastic, for example, polyamide, PEKK, PEEK, or PPS. One advantage of using a thermoplastic is the ability to at least partially melt the matrix material through heating and pressure, so that the individual components of the composite already exhibit a certain degree of dimensional stability before consolidation and subsequently bond together firmly.

[0024] The method further comprises providing a plurality of stiffening elements and positioning the stiffening elements on the inside of the first layer prior to consolidation. Providing the stiffening elements may comprise simply providing purchased stiffening elements. However, it would also be conceivable to produce such stiffening elements using a process for manufacturing components from a fiber composite material. The goal is to provide suitable stiffening elements that are arranged in a material-locking manner on the inside of the first planar layer. Subsequently, the composite of the first layer, the second layers, and the stiffening elements is consolidated, at least by applying pressure.

[0025] According to the invention, the production of the at least one first layup comprises the production of an even number of first flat lays with an outer first layup and an inner first layup, wherein the positioning of the second layup comprises the introduction of at least a portion of the second layup between the outer first layup and the inner first layup. Both first layups have an inner side and an outer side. The outer side of the inner first layup faces the outer first layup, while the inner side of the outer first layup faces the inner first layup. Consequently, both first flat lays form the basis of the component to be produced, wherein a portion of the second layup is enclosed by the two first layups for local reinforcement. The surfaces determined by both first layups are very continuous and closed, which has a positive effect on the strength of the component.When consolidating the composite of the above-mentioned components, it is important to ensure that the shape of, for example, the outer first layer, which forms an outer surface of a fuselage shell, is kept true.

[0026] The above-mentioned stiffening elements are preferably positioned on the inside of the inner first layer before consolidation.

[0027] Preferably, the inner first fabric and the outer first fabric have a layer structure that is symmetrical to one another. Particularly preferably, the inner and outer fabrics have a layer structure that is symmetrical to one another. This can prevent distortions or deformations in the component to be produced after initial consolidation. In particular, both first fabrics should have an identical thickness, an identical number of layers, and identical materials.

[0028] An advantageous embodiment further comprises the positioning of one or more of the second or third layups on an inner side of the inner first layup. This allows for further local reinforcements to be generated. Since these are not located between two closed first layups, significantly greater cross-sectional changes can occur. For example, 90° transitions or surface gradients with a ratio of 1:20 can be used where necessary. Such second layups would lead to deformations, tensions, cavities and thus to delamination under load between two first layups, so that such second layups should be arranged in particular on the inner side of an inner first layup. The size of such second layups could be selected such that automated fiber deposition processes can be avoided and, in particular, double-belt presses can be used.

[0029] In a further advantageous embodiment, the second layers arranged on the inner side of the inner first layer are formed symmetrically to the second layers arranged between the two first layers. This means that the layers have fiber directions that are symmetrical to one another.

[0030] The production of the at least one first fabric can preferably be carried out using a double-belt press. Any desired length of workpiece can be produced in such a press. For example, a fiber material can be coated or impregnated with a matrix material and consolidated. The double-belt press has two parallel belts that exert a desired pressure on a semi-finished product passing through the device. As explained above, large, plate-shaped components can be produced from a fiber composite material with a constant thickness. The double-belt press is particularly suitable when using a fiber composite material with a thermoplastic matrix material.

[0031] The production of the second fabric can be carried out at least partially using an automated fiber deposition process. This allows for more complex outer contours of the second fabric. Furthermore, such processes can be used for more customized design, especially with smaller dimensions of the second fabric.

[0032] The composite could be formed on a mold, with the composite subsequently being enclosed between the mold and a pressure block, and the composite being consolidated by the action of mechanical pressure from the pressure block toward the mold. The pressure block can have a certain degree of flexibility, so that when the composite is pressed onto a solid mold, the components of the composite are pressed together. When using two first layers, small hollow spaces may still exist in the composite, which can be eliminated by adapting the shape, particularly of the inner first layer, during pressing.

[0033] It is conceivable that an inner first layer could be three-dimensionally adjusted in its shape before the composite is formed on the mold. The same applies to the stiffening components, which could be shaped into a desired three-dimensional form before positioning.

[0034] If the method according to the invention is used to manufacture a part of an aircraft fuselage, for example, a fuselage shell, the method could further comprise embedding a lightning protection layer. This layer could be implemented as a global layer with a uniform thickness and extending over the entire component.

[0035] In an advantageous embodiment, consolidation can be carried out using a process selected from a group of processes comprising press consolidation, vacuum consolidation, and autoclave consolidation. Press consolidation was already mentioned above. Consolidation in an autoclave results in uniform pressurization of the composite while simultaneously heating it. However, the size of the autoclave into which the composite is inserted must be adapted for this purpose. Alternatively, it is also conceivable to cover the composite with a vacuum film and evacuate the space between the mold and the vacuum film. This allows the ambient pressure surrounding the mold to press the composite against the mold. This could be comparatively simple if the ambient pressure is mechanically sufficient.

[0036] It is preferred if the first, second and third layers are made of a thermoplastic, fiber-reinforced plastic.

[0037] The invention further relates to a component according to claim 8.

[0038] The component further comprises a plurality of stiffening elements arranged on the inner side of the at least one first layer. The composite of the at least one first layer, the second layers, and the stiffening elements is then consolidated at least by applying pressure.

[0039] Furthermore, the component has two first layers and at least a part of the second layers is arranged between the first layers.

[0040] Furthermore, the component has an even number of first planar layers made of a fiber composite material with a constant thickness, an outer side and an inner side, wherein the first layer has a surface area that determines the surface area of the component, a plurality of second and third planar layers made of the fiber composite material, wherein the surface area of the second and third layers is less than that of the first planar layer, and a plurality of stiffening elements, wherein the second layers are arranged in such regions of the inner side of the outer first layer and the third layers are arranged in such regions of the inner side of the inner first layer where a local thickness must be increased to increase the local strength, wherein the stiffening elements are arranged on the inner side of the first layers, and wherein the composite of the first layers,the second and third layers and the stiffening elements are consolidated at least by applying pressure.

[0041] According to the invention, the component is manufactured using a method mentioned above. This component can, in particular, be a fuselage shell, a wing shell, a tail shell, or another flat component of an aircraft. SHORT DESCRIPTION OF THE CHARACTERS

[0042] Further features, advantages, and possible applications of the present invention will become apparent from the following description of the exemplary embodiments and the figures. All described and / or illustrated features, individually and in any combination, constitute the subject matter of the invention, regardless of their composition in the individual claims or their references. In the figures, the same reference numerals continue to represent the same or similar objects. Fig. 1 shows a process in a schematic, block-based representation. Fig. 2 shows a partial section of a component to be manufactured. Fig. 3 shows an aircraft and a fuselage shell of the aircraft as a component to be manufactured. Fig. 4 , 4A , 5 and 5A show the application of different forming tools. DETAILED REPRESENTATION OF EXEMPLARY EMBODIMENTS

[0043] Fig. 1 shows a method 2 according to the invention for producing a component in a schematic, block-based representation. The method 2 begins, by way of example, with the production 4 of at least one first planar fabric made of a fiber composite material with a constant thickness, wherein the first fabric has a surface area that determines the surface area of the component. Subsequently, simultaneously or in a preceding step, the production 6 of a plurality of second planar fabrics from the fiber composite material takes place, wherein the surface area of the second fabrics is less than that of the first planar fabric. Subsequently, simultaneously or in a preceding step, the provision 8 of a plurality of stiffening elements takes place.

[0044] For simplicity, these three steps, 4, 6, and 8, are marked as consecutive steps. However, as explained, they can also be performed in a different order.

[0045] Once these components—i.e., the at least one first planar fabric, the second planar fabrics, and the stiffening elements—are present, they are positioned accordingly to form a composite of components. The second fabrics are positioned 10 in those areas of an inner side of the first fabric where a local thickness needs to be increased to increase local strength.

[0046] Subsequently, or in a preceding step, stiffening elements are positioned 12 on the inside of the first layer, followed by consolidation 14 of the composite of the first layer, the second layers, and the stiffening elements, at least with the application of pressure. For the sake of simplicity, process steps 10 and 12 are also designated as subsequent steps. However, the order in which these steps are performed may depend, in particular, on the shape of the mold.

[0047] The production 4 of the at least one first planar fabric may comprise the production 16 of an outer first fabric and the production 18 of an inner first fabric. The positioning 10 of the second fabric may then consequently comprise the insertion 20 of at least a portion of the second fabric between the outer first fabric and the inner first fabric.

[0048] Additionally, one or more of the second layers can be positioned 22 on the inside of the inner first layer to achieve further local stiffening. These can also be equipped with stronger shape transitions than the second layers arranged between the first layers.

[0049] Fig. 2 shows an exemplary layer structure of a component 42 to be manufactured in a partial section. Here, in the drawing plane below, an outer first layer 24 is shown, which is equipped with a series of layers 24a, 24b, ..., 24f. At a distance from this, an inner first layer 26 is provided, which has several layers 26a, 26b, ..., 26f. It is intended that the layers 24a to 24f and the layers 26a to 26f are symmetrical to one another. This means that the fiber directions of the individual layers are the same as the distance between the first layers 24 and 26 increases.

[0050] A second layer 28 is arranged between the two first layers 24 and 26, which, for example, has a series of layers 28a, 28b, 28c, and 28d. It is preferred that surface transitions in the second layer 28 run very smoothly, so that surface gradients of at most 1:200 are achieved. By pressing on the inner first layer 26 or the outer first layer 24, the second layer 28 is enclosed flush.

[0051] In this context, the sides of a composite 30 comprising the shown interlaces are to be designated as follows. A side 32 of the outer first interlace 24 facing away from the inner first interlace 26 is to be designated as the outer side 32. The opposite side is the inner side 34. A side of the inner first interlace 26 facing the outer first interlace 24 is an outer side 36, and an opposite side is an inner side 38. Arranged on the inner side 38 of the inner first interlace 26, by way of example, is a row of further second interlaces 40, which provide additional reinforcement for the component. With these non-enclosed second interlaces 40, larger surface gradients of, for example, up to 1:20 can be realized.

[0052] It is preferred that the second layers 40 on the inner side 38 of the inner first layer 26 are formed symmetrically to the second layers 28 between the first layers 24 and 26.

[0053] As an example of a component 42 to be manufactured, the representation of an aircraft 44 in Fig. 3 The component 42 could be a fuselage shell having several window cutouts 46 and a door cutout 48. In areas around the window cutouts 46 and the door cutout 48, there may be local thickenings, which could be realized, for example, with second layers 28 and 40. Fig. 2 With the topology shown, it is possible to realize local thickenings using second layers 28 and still provide large-format components in efficient and rapid manufacturing processes as flat components with a uniform thickness.

[0054] Fig. 4 and 4Ashow a first variant of a molding tool 50, which has a rigid base 52, on which stiffening elements 54 in the form of stringers are initially arranged. These are later directed toward an inner side of the component 42. The inner first fabric 26, which is three-dimensionally adapted in its contour in some partial areas 56, is positioned on the stringers 54. This makes it possible to arrange the enclosed second fabrics 28 between the stringers 54 or both below and between the stringers 54, so that they lead to a local thickening.

[0055] The outer first layer 24 is then arranged. By previously adjusting the contour of the inner first layer 26, the outer side 32 of the outer first layer 24 remains in its planned shape. The outer side 32, which represents, for example, an outer surface of the fuselage shell 42, can thus be placed flush with the other components. By subsequently pressing the outer first layer 24 on using a pressure block 58, consolidation can be carried out without the outer first layer 24 changing its shape. The enclosed second layers 28 can also be provided with a final, three-dimensional contour, or they can be placed largely flat and only brought into their intended shape by pressing on the pressure block 58.

[0056] The representations in Fig. 4 and 4Aare merely exemplary; other scrims are also possible, and a lightning protection layer (not shown) could also be integrated. Furthermore, instead of a pressure block 58, a vacuum film could also be applied, so that air is sucked out between the vacuum film and the rigid base 52, so that the air pressure surrounding the mold 50 acts on the composite 30.

[0057] Fig. 5 and 5A show another mold 60. This has a rigid base 62 on which the outer side 32 of the outer first layer 24 is positioned. Adjoining this are the enclosed second layers 28, onto which the inner first layer 26 is positioned. Subsequently, the stiffening components 54 are attached. A pressure block 64 then serves to press the stiffening elements 54 and the inner first layer 26 together, particularly while simultaneously heating them to consolidate the component.

[0058] Additionally, it should be noted that "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be noted that features described with reference to one of the above embodiments can also be used in combination with other features of other embodiments described above. Reference signs in the claims are not to be considered as limitations. REFERENCE SYMBOL

[0059] 2Process 4Producing a first flat scrim 6Producing second flat scrims 8Providing stiffening elements 10Positioning second scrims 12Positioning stiffening elements 14Consolidating 16Producing outer first scrim 18Producing inner first scrim 20Introducing second scrim between first scrim 22Positioning second scrim 24Outer first scrim 26Inner first scrim 28(enclosed) second scrim 30Composite 32Outer side of the outer first scrim 34Inner side of the outer first scrim 36Outer side of the inner first scrim 38Inner side of the inner first scrim 40Second scrim 42Component 44Aircraft 46Window cutout 48Door cutout 50Mold 52Rigid base 54Stiffening elements 56Partial areas of the inner first scrim 58Pressure block 60Forming tool 62Rigid base 64Pressure block

Claims

1. Method (2) of producing a component (42), having the steps of: - producing (4) an even number of first planar scrims (24, 26) having an outer first scrim (24) and an inner first scrim (26) from a fibre composite material having a constant thickness, an outer face (32, 36) and an inner face (34, 38), where the first scrims (24, 26) have an areal extent that determines the areal extent of the component (42), where a side of the outer first scrim (24) facing away from the inner first scrim (26) shall be referred to as the outer face, and the opposite side as the inner face, and where a side of the inner first scrim (26) facing the outer first scrim (24) shall be referred to as the outer face, and an opposite side as the inner face; - producing (6) a plurality of second planar scrims (28, 40) from the fibre composite material, where the areal extent of the second scrims (28, 40) is less than that of the first planar scrim (24, 26); - positioning (10) the second scrims (28, 40) in those regions of the inner face (34, 38) of the first scrim (24, 26) where a local thickness has to be increased in order to increase local strength, where the positioning of the second scrims (28, 40) comprises the introducing of at least a portion of the second scrim (28, 40) between the outer first scrim (24) and the inner first scrim (26); - providing (8) a plurality of reinforcing elements (54); - positioning (12) the inner first scrim (24, 26) on the reinforcing elements (54), where the contour of the inner first scrim (24, 26) is three-dimensionally adapted in some regions (56) and the enclosed second scrims (28, 40) are disposed either between the reinforcing elements (54) or beneath and between the reinforcing elements (54) such that they locally lead to thickening, and subsequently arranging the outer scrim (24); and - consolidating (14) the composite (30) composed of the first scrims (24, 26), the second scrim (28, 40) and the reinforcing elements (54) at least by applying pressure.

2. Method (2) according to Claim 1, wherein the inner first scrim (26) and the outer first scrim (24) have a mutually symmetrical ply structure.

3. Method (2) according to either of the preceding claims, wherein the composite (30) is formed on a forming tool (50, 60), wherein the composite (30) is subsequently enclosed between the forming tool (50, 60) and a pressure block (58, 64), and wherein the composite (30) is consolidated by the action of mechanical pressure by the pressure block (58, 64) in the direction of the forming tool (50, 60).

4. Method (2) according to any of the preceding claims, wherein the shape of an inner first scrim (26) is adapted three-dimensionally before the composite (30) is formed on a forming tool (50, 60).

5. Method (2) according to any of the preceding claims, wherein the consolidating (14) is performed by a process selected from a group of processes comprising: - press consolidation, - vacuum consolidation, and - autoclave consolidation.

6. Method (2) according to any of the preceding claims, wherein the first scrims (24, 26) and the second scrims (28, 40) are produced from a fibre-reinforced thermoplastic.

7. Method (2) according to any of the preceding claims, wherein the component (42) is a fuselage shell, a wing shell, a tail shell or another planar component (42) of an aircraft (44).

8. Component (42) produced by a method according to Claims 1 to 7, comprising: - an even number of first planar scrims (24, 26) having an outer first scrim (24) and an inner first scrim (26) produced from a fibre composite material having a constant thickness, an outer face (32, 36) and an inner face (34, 38), where the first scrims (24, 26) have an areal extent that determines the areal extent of the component (42); - where a side of the outer first scrim (24) facing away from the inner first scrim (26) shall be referred to as the outer face, and the opposite side as the inner face; - where a side of the inner first scrim (26) facing the outer first scrim (24) shall be referred to as an outer face, and an opposite side as an inner face; - a plurality of second planar scrims (28, 40) produced from the fibre composite material, where the areal extent of the second scrim (28, 40) is less than that of the first planar scrim (24, 26), wherein the second scrims (28, 40) are disposed in those regions of the inner face (34, 38) of the first scrim (24, 26) where a local thickness has to be increased in order to increase local strength, and where at least a portion of the second scrim is disposed between the outer first scrim (24) and the inner first scrim (26); - wherein the component (42) further comprises a plurality of reinforcing elements (54) disposed on the inner face (34, 38) of the at least one first scrim (24, 26); - wherein the inner first scrim (26) is disposed on the reinforcing elements (54), where the contour of the inner first scrim (26) is three-dimensionally adapted in some regions and the enclosed second scrim is disposed either between the reinforcing elements (54) or beneath and between the reinforcing elements (54) such that they locally lead to thickening; and - wherein the composite (30) composed of the at least one first scrim (24, 26) and the second scrim (28, 40) and the reinforcing elements (54) is consolidated by applying pressure.