Method for manufacturing a composite part

Abstract

A method for manufacturing a component from fibre-reinforced plastic has the following steps: providing a forming tool (2) having a tool surface (4), positioning a first layer (6) made from a fabric semi-finished product formed from dry fibres on the tool surface (4), arranging a second layer (8) made from an electrically conductive, resin-permeable grid on the first layer (6), arranging an uppermost layer assembly (12), sealing the assembly consisting of a plurality of layers by means of a closure device (14) to form a shaped part, introducing resin into the shaped part in order to permeate all layers with resin, and curing and removing the component.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a component from fiber-reinforced plastic and an aircraft having at least one such component. Background Technology

[0002] To ensure safe operation, large components made of fiber-reinforced plastics, especially those used in aircraft, are equipped with surge protectors. Such surge protectors are implemented, for example, in the form of a conductive layer embedded in resin. This conductive layer can be bonded to the outside of such large components. In known methods, this can be achieved by combining a resin-containing conductive layer for surge protection with a pre-impregnated, pre-formed, and uncured component (prepreg) and then curing the composite.

[0003] To ensure sufficient resin injection into layers or preforms adjacent to the conductive layer, flow aids are typically used. For example, pads for dispersing resin over large areas are known and are additionally incorporated into the preform. Flow aids are also provided on the surface of the preform that is in contact with the molding die to supply resin to said sides of the preform. To achieve a high surface quality in the resulting part, at least one side of the cured part requires further processing.

[0004] EP 2 222 563 A1 discloses a lightning protection system for aircraft structures made of fiber-reinforced plastic, wherein conductive strips are arranged on the outside of the aircraft structure. Summary of the Invention

[0005] The goal is to be able to manufacture large-sized parts without the need for expensive mobile auxiliary tools, while simultaneously integrating adequate lightning protection and achieving high part surface quality.

[0006] Therefore, the object of the present invention is to propose a method for manufacturing, especially large-sized, components from fiber-reinforced plastics, wherein, although lightning protection is integrated into the material, the component or fiber fabric can be infiltrated without the need for a separate flow aid.

[0007] This objective is achieved by a method for manufacturing components from fiber-reinforced plastics according to the present invention. Preferred embodiments and improvements can be found in the following description.

[0008] The method comprises the following steps: providing a first molding die and a die surface; positioning a first layer made of a fabric semi-finished product formed from dried fibers on the die surface; arranging a second layer made of a conductive, resin-permeable mesh on the first layer; placing an uppermost layer assembly; sealing the entire assembly consisting of multiple layers on the molding die by means of a sealing device to form a molded part; introducing resin into the molded part to permeate all layers with resin; and curing and removing the part.

[0009] The method is, in principle, a resin injection molding (RTM) or vacuum infusion (VARI) method. The method is based on providing a multi-layer component that is sealed to a mold by a sealing device. Here, the sealing device can be a flexible film that is sealed to the surface of the mold by other means. Alternatively, the sealing device can be implemented as a rigid or shape-stable mold segment existing in addition to the aforementioned mold.

[0010] The purpose is to encapsulate multilayer components in a hermetically tight and shape-stable manner on a molding die. A vacuum can then be applied. Next, resin is introduced into the multilayer composite located within the molded part. This can be done simply by the suction force created after optional vacuuming or by applying external pressure to the resin.

[0011] The core aspect of the method according to the invention lies in using a second layer made of a conductive but resin-permeable mesh on a first layer made of a fabric semi-finished product. Integrating this conductive layer results in the desired lightning protection effect of the component. However, the mesh with openings for resin flow is particularly advantageous, as the resin can easily flow through the mesh of the second layer. Using such a conductive layer, which is neither embedded in the resin nor impermeable itself, allows uncured resin to be introduced only from one side of the component to be produced. All layers remain permeated with resin. Therefore, the resin-permeable implementation of this conductive layer facilitates its function as a flow aid. A separate flow aid is thus no longer needed. The conductive layer can be constructed to match known flow aids that are not composed of conductive materials.

[0012] Resin flowing into the upper layer (e.g., the uppermost layer assembly described above) or the lower layer (e.g., the first layer described above) can reach the fibers located on the other side of the second layer via a resin-permeable conductive layer. Therefore, the conductive layer is also permeated by the resin during permeation. The first layer, providing a resin-rich layer after permeation, can be arranged regardless of the resin introduction direction. Thus, the conductive layer and the uppermost layer assembly are embedded together in the resin, eliminating the need for pre-coating of the conductive layer.

[0013] In the sense of this invention, the term "resin" refers to any matrix material suitable for forming fiber composite components with fibrous materials. Furthermore, the matrix material may also include a curing agent (multi-component resin system). In a narrower sense, "resin" can refer to rigid plastics, such as epoxy resin systems. However, the use of thermoplastic plastics should not be excluded.

[0014] The terms “above” and “below” as used within the scope of this disclosure do not necessarily refer to the vertical direction of extension, but should be understood as “the side away from the mold” (above) and “the side towards the mold” (below).

[0015] Furthermore, the resin can be introduced into the entire multilayer assembly and the molded part formed by the molding die and closure device without approaching from both sides. Introduction from a single direction of the assembly is sufficient, for example, against the mold surface. However, it can also be done from another direction. Through advantageous resin diffusion throughout the entire multilayer composite, the surface quality of the resin-coated conductive layer can therefore be directly dependent on the surface properties of the mold surface.

[0016] In an advantageous embodiment, the method further includes a step of evacuating the molded part. Thereby, resin is drawn into individual layers, particularly or solely, by the resulting suction to achieve permeation. This step may be omitted in some cases in the RTM method described above, but it is essential in the vacuum infusion method.

[0017] In an advantageous embodiment, the resin-permeable conductive mesh is a fabric made of a metallic material. To optimize lightning protection performance, the mesh has a specific structure. Such a suitable structure can be determined experimentally or based on existing data. The mesh structure also decisively determines the flow behavior of the resin in the first layer. The simplest variant of the metallic fabric is a two-dimensional fabric, in which the metal fibers, wires, or foils extend only in one plane. To achieve a certain degree of permeability, the fabric has a mesh. The mesh width can be optimized to achieve sufficient permeability not only between adjacent layers but also sufficient lightning protection.

[0018] In one advantageous embodiment, the resin-permeable conductive mesh is a three-dimensional mesh made of metallic material. Compared to two-dimensional structures, the three-dimensional mesh structure tends to provide larger flow openings, thus achieving better permeability. Furthermore, the flow openings can also extend obliquely relative to the main extension plane of the mesh. The three-dimensional structure of the mesh can be manufactured similarly to an extended metal mesh, which is formed by stretching or pulling a base foil or base plate with staggered cross-sections into a three-dimensional, regularly or irregularly curved structure.

[0019] In a preferred embodiment, the metallic material is copper or bronze. These materials have excellent electrical conductivity, making them particularly suitable for lightning protection.

[0020] In another advantageous embodiment, the first layer comprises non-woven fibers. This layer can be made of the same material as the uppermost multilayer assembly. The first layer, for example, consists of oriented fiber bundles. It is possible to use fiber residue to achieve the first layer. The purpose of the first layer is to provide a resin-rich layer that allows the manufactured part to be coated with a varnish layer. Therefore, the resin layer produced by the first layer constitutes the outer side of the part. Due to the lack of additional flow aids when injecting the outer layer, a particularly excellent surface quality can be achieved without additional measures. Furthermore, when opening holes in the part manufactured according to the method of the invention, fiber escape from the uppermost layer assembly should be avoided.

[0021] In an advantageous embodiment, the fibers of the first layer are implemented as short fibers. These short fibers correspond in cross-section and construction to the fibers of the uppermost layer assembly, but have a relatively short length, particularly in the range of a few centimeters. This allows for the production of a very uniform, resin-rich layer in which the fibers generally run in all directions and thus possess high strength.

[0022] Furthermore, the method includes the step of placing an intermediate layer between the conductive, resin-permeable mesh and the uppermost layer assembly, wherein the intermediate layer comprises non-conductive fibers. The non-conductive fibers can be, for example, in the form of glass fibers, aramid fibers, Kevlar fibers, polyester fibers, or similar fibers. This creates an insulating layer between the conductive layer and the actual structural component constituted by the uppermost layer assembly. This insulating layer can prevent damage to the actual structural component in the event of a lightning strike, which is particularly advantageous for plastics containing carbon fibers.

[0023] In the method according to the invention, the layers may further be made of a material that is not heat-resistant, which is decomposed or dissolved when the molding die is heated to cure the part, thereby allowing the uncured resin contained therein to at least partially enter the remaining layers before curing. This minimizes the resin layer thickness at the first layer. A sufficient amount of resin enters the first layer during infiltration. The multilayer composite is compressed by a sealing device and optionally by vacuuming, so that the shape of the bottom layer changes due to fiber decomposition during subsequent heating. The volume of the bottom layer is reduced, and the resin contained therein can enter the adjacent material layers. The remaining resin remains in the bottom layer and ensures a sufficiently smooth surface on the mold-facing side of the part.

[0024] The present invention also relates to an aircraft comprising at least one component manufactured by the method described above.

[0025] The at least one component may be a tail fin, wing, or fuselage component. Attached Figure Description

[0026] Other features, advantages, and applications of the invention will become apparent from the following description of the embodiments and drawings. Hereinafter, all described and / or illustrated features, in themselves and in any combination, constitute the subject matter of the invention, regardless of their relationship to the individual claims or the claims to which they are referenced. In the drawings, the same reference numerals denote the same or similar objects.

[0027] Figure 1 A schematic diagram of a multilayer structure according to the method of the present invention is shown.

[0028] Figure 2 The block diagram illustrates the process of a method for manufacturing a component.

[0029] Figure 3 An aircraft is shown, which has at least one component manufactured by the method according to the invention. Detailed Implementation

[0030] Figure 1 A molding die 2 with a mold surface 4 is shown, on which a part is manufactured. First, a first layer 6, made of a fabric semi-finished product formed from dried fibers, is positioned on the mold surface 4. The first layer 6 is designed to provide a resin layer as smooth and uniform as possible on the outer side of the part. The outer side could, for example, be the outward-facing surface of an aircraft part in later use. The first layer 6 is preferably painted after the part is removed from or from the molding die 2 without further processing.

[0031] A second layer 8 is positioned on top of the first layer. This second layer consists of a conductive, resin-permeable mesh. The second layer can be constructed of a metallic material, particularly copper or bronze. The mesh can be implemented in a two-dimensional manner, such that all components of the layer—material bundles, surface areas, foil segments, and similar components—extend in the same plane. This second layer 8 serves as lightning protection for components manufactured by this method.

[0032] However, alternatively and preferably, the mesh 8 is a three-dimensional mesh with a significantly greater thickness than a simple foil. This second layer 8 can be implemented, for example, as an extended metal mesh. The extended metal mesh has flow openings that allow resin to penetrate not only in the direction toward the molding die 2 but also in the direction away from the molding die. If the resin is distributed, for example, in the first layer 6 and the second layer 8, the resin flow can proceed smoothly primarily from the side toward the molding die 2 to the direction of the uppermost layer assembly 12. Of course, the penetration can also occur in the opposite direction.

[0033] Optionally, an intermediate layer 10 made of non-conductive fibers may also be positioned on this second layer 8. Thus, electrical insulation is formed between the second layer 8 and the uppermost layer assembly 12 located above it.

[0034] The uppermost layer assembly 12 may have one or more fiber layers oriented in the same or different directions. The uppermost layer assembly 12 is used to manufacture a structural component with desired strength. It constitutes the core of the actual component. The fibers used therein may, in particular, be carbon fibers.

[0035] After arranging the different layers shown (which can be collectively referred to as a multilayer composite), a sealing device 14 is placed on the molding die 2. The multilayer composite is surrounded in an airtight manner. Resin can be introduced after optional vacuuming. Although resin can be introduced from the side of the layer assembly away from the molding die 2, it may be desirable to introduce resin from the side facing the mold surface 4. Because all layers allow resin diffusion due to their more or less open structure, resin introduced from one side can be distributed throughout the entire layer assembly. In other words, this means that these layers are collectively and from one direction permeated by resin.

[0036] Here, the second layer 8, in addition to its actual lightning protection function, can also be regarded as a flow aid, allowing resin to permeate the first layer 6 or the uppermost layer assembly 12. In this way, resin can be uniformly supplied across the entire lateral and vertical dimensions of the second layer 8.

[0037] After a sufficient amount of resin is introduced, the component is cured, particularly by a corresponding heat input and while the sealing device 14 is held on the mold surface 4. Here, an optional vacuum can be maintained in particular.

[0038] Components manufactured using this method, due to the uppermost layer assembly, not only possess the desired strength but also have outwardly pointing lightning protection and an insulating layer between the lightning protection layer and the main structural component. No resin input from either side of the layer assembly is required, nor are additional flow aids needed.

[0039] Figure 2The block diagram illustrates the flow of the method according to the invention. First, a molding die 16 is provided, and then a first layer, made of a fabric semi-finished product formed from dried fibers, is positioned 18 on the die surface. A second layer, made of a conductive, resin-permeable mesh, is arranged 20 on the first layer. Next, the uppermost layer assembly is positioned 22 on the mesh. The multilayer assembly or multilayer composite is sealed 24 by means of a sealing device to form a molded part. Then, if desired, a vacuum 26 can be applied. Resin 28 is then introduced, thereby causing penetration 30. After curing 32, the part can be removed 34. Before arranging the uppermost layer assembly, an intermediate layer 36 comprising non-conductive fibers can be arranged or placed.

[0040] at last, Figure 3 An aircraft 38 is shown, having a fuselage 40, wings 42, and a tail 44. One or more components, or only a segment of such a component, can be manufactured, at least in part, by the methods shown above. This reduces the cost of manufacturing such components and optimizes costs.

[0041] Additionally, it should be noted that "having" does not exclude other elements or steps, and "an" does not exclude a plurality. Furthermore, it should be noted that combinations of features already described with reference to one of the above embodiments, as well as other features of the other embodiments described above, may be used. Reference numerals in the claims should not be considered limiting.

Claims

1. A method for manufacturing a component from fiber-reinforced plastic, comprising the following steps: - Provide (16) a molding die (2) having a mold surface (4). -The first layer (6), made of a fabric semi-finished product formed from dried fibers, is positioned (18) on the surface (4) of the mold. - A second layer (8) made of a conductive, resin-permeable mesh is arranged (20) on top of the first layer (6). - Arrange (22) the topmost layer component (12). -The multi-layered component is sealed (24) by means of a sealing device (14) to form a molded part. - Introduce (28) resin into the molded part so that all layers (30) are permeated with resin, and -Cure (32) and remove (34) the component. The first layer (6) is made of a material that is not heat-resistant. The material is decomposed or dissolved when the molding die (2) is heated to cure the component, so that the uncured resin contained therein enters at least partially into the remaining layers before curing.

2. The method according to claim 1, In addition, there is a step of evacuating the molded part (26).

3. The method according to claim 1 or 2, The conductive, resin-permeable mesh is a fabric made of metallic material.

4. The method according to claim 1 or 2, The conductive, resin-permeable mesh described therein is a three-dimensional mesh made of metallic material.

5. The method according to claim 3, The metal material mentioned is copper or bronze.

6. The method according to claim 4, The metal material mentioned is copper or bronze.

7. The method according to claim 1 or 2, The first layer (6) has non-woven fibers.

8. The method according to claim 1 or 2, The fibers in the first layer (6) are short fibers.

9. The method according to claim 1 or 2, Furthermore, it includes the step of placing an intermediate layer (10) (36) between the second layer (8) made of the conductive, resin-permeable mesh and the uppermost layer assembly (12). The intermediate layer (10) has non-conductive fibers.

10. The method according to claim 9, The fibers of the intermediate layer (10) are glass fibers.

11. An aircraft (38) having at least one component manufactured by the method according to any one of claims 1 to 10.

12. The aircraft (38) according to claim 11, wherein at least one of the components is a tail (44), a wing (42) or a fuselage component (40).

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