Automatic deposition method for producing a preform by means of fabric tape

Abstract

The invention relates to an automatic deposition method for producing a preform from reinforcing fibres, wherein the reinforcing fibres required therefore are present in a fabric tape and therefore this fabric tape is used as processing material in the automatic deposition method.

Description

[0001] Automatic deposition process for producing a preform using a fabric belt

[0002] Description:

[0003] The invention relates to an automatic deposition method for producing a preform.

[0004] Automatic deposition processes, such as dry fiber placement (DFP), are well known. This process is a fully automated manufacturing process for producing preforms for the construction of fiber-reinforced components.

[0005] Fiber-reinforced, usually unidirectional tapes are placed along a predetermined path on the mostly three-dimensional mold surface using a robot. Individual layers are bonded together with a mostly powder-like binder material using pressure and temperature, resulting in a coherent, manageable fiber preform. Dry fiber placement is a technology for the additive and automated production of dry preforms. The UD tapes used are usually bonded with a binder and are placed directly onto the component surface in a near-net shape and in line with the load path. This results in minimal waste and effective material utilization. The dry preform is then consolidated in a matrix infusion process. A method for producing a preform is known from US Pat. No. 10,406,798.The document discloses a method for forming a preform using AFP (Automated Fiber Placement), in which fiber bundles are placed on top of one another in different directions and then connected by needle punching. US Pat. No. 10,583,615 (D5) proposes a tape material for an ATL (Automatic Tape Laying) or AFP process. The tape material consists of a UD fiber layer to which a nonwoven material is attached on one side. In addition, at least one binder material is distributed on both sides of the UD fiber layer. Carbon fibers are proposed as the fiber material for the UD fiber layer. The use of binder and nonwoven material is intended to fix the fibers of the UD layers in their position during component production. Consequently, in the prior art, wide unidirectional (UD) fabrics are produced and then cut, for example, into strips with the final width of the DFP material (so-called slitting).For example, nonwovens and binder powder are required to hold the individual fiber strands of the DFP fabric together. The slitting process is associated with costs, making such materials comparatively expensive. Furthermore, the highly compact material often makes it difficult to subsequently impregnate the material with the matrix materials in an infiltration process for component production, as these materials exhibit low permeability due to the very straight fiber strands.

[0006] The object of the present invention was therefore to reduce or eliminate these disadvantages of the known prior art. This object is achieved by a method according to claim 1.

[0007] In a method according to claim 1, in an automatic

[0008] A preform made of reinforcing fibers is formed in the deposition process, whereby the reinforcing fibers required for this purpose are present in a fabric tape and this fabric tape is therefore used as processing material in the automatic deposition process.

[0009] Fabric tapes are also not new in general. For example, EP 0193478 describes a fabric tape that has reinforcing fibers in the warp direction and bicomponent threads made of a thermoplastic material in the weft direction. US 5662146 also describes a fabric made of flat carbon fibers that are supposed to be twist-free in the fabric. EP 0909845 describes unidirectional carbon fiber fabrics that are supposed to use particularly thick carbon fiber yarns. US 4680213 describes fabrics that are supposed to have reinforcing fibers as warp threads and a bicomponent thread in the weft thread with a core made of the material of the reinforcing fibers used. The described fabrics are intended to be used directly as textile material; a laying process is not provided for the material. US 6,009,605 also describes the production of a curved tape with a radial weft yarn.Carbon fibers can be used as the fiber material for the tape. The material according to this document is sewn, and a preform is formed by wrapping it around a mold. FR 3 066 429 discloses the production of fibrous preforms by three-dimensional (3D) or multilayer weaving. The thus woven fiber structure is to be wound onto an injection mold that corresponds to the profile of the part to be manufactured.

[0010] Furthermore, DE 10 2011 102 950 describes a device and a method for producing a textile preform, wherein a fiber ribbon or fiber bundle containing carbon fiber is heated. The heating activates a binding agent, which fixes the fiber ribbon or fiber bundle in the preform. It was surprising and unforeseeable that the use of fabric ribbons with reinforcing fibers in an automatic deposition process for producing a preform is possible and achieves good results.

[0011] The automatic deposition process is preferably a dry fiber placement (DFP) process. This process preferably produces a so-called dry preform.

[0012] As can be seen, the idea of ​​using woven tapes as a processing material has the advantage that the processing material can already be produced in the desired width, with the reinforcing threads in the tape fabric being slightly spread out. The previously common additional step of slitting unidirectional fiber layers to the desired width is thus eliminated. Furthermore, the impregnability of the processing material can be influenced by the fabric design and can therefore be controlled using different fabric parameters (e.g. weave type, thread density and thread count of warp and weft). This advantageously provides a process in which the processing material can be better adapted to the preform in terms of width and impregnability, without significantly changing the costs or availability of the processing material.

[0013] In the following, the terms "processing material", "material", "tape fabric", "woven tape" and "tape fabric" are used synonymously. However, these terms refer to a material in which the reinforcing fibers (as warp threads and / or weft threads) are woven with other fibers (which are warp threads or weft threads), whereby the weaving involves the weft thread being alternately guided above and below the warp thread. In a flat woven tape, the woven tape only has one warp layer and one weft layer, which are connected to one another by the woven connection. 3D woven tapes generally have more than one warp layer and / or one weft layer and are therefore not flat woven tapes. The woven tape for the present automatic laying process is further characterized by the fact that the warp threads and the weft threads are each axially aligned within their layer.In an axial alignment, the fibers within the layer are not arranged in a radial arrangement, but are arranged along a straight axis.

[0014] The ribbon fabric required for the process is preferably produced in a ribbon weaving process, preferably using needle ribbon looms. The warp yarn is preferably arranged on a creel, and the weft thread is inserted from the side using a guide needle. Two edge threads are preferably incorporated into the ribbon fabric, which define the ribbon fabric laterally and fix the inserted weft thread on one side in a stitch-forming process. As an alternative to the use of edge threads, the intersection points of the warp and weft can create a frictional connection, resulting in an inherently stable ribbon fabric. Consequently, no binder or nonwoven is required to stabilize the ribbon fabric itself, which makes the ribbon fabric particularly drapable.

[0015] In one embodiment, the ribbon fabric is therefore free of an additional matrix material layer and a nonwoven material deposited thereon.

[0016] In one embodiment, the warp threads of the fabric tape are reinforcing fibers. The fabric tape preferably comprises carbon fibers as warp threads. However, aramid fibers or glass fibers, or mixtures of the aforementioned materials, can also be used as reinforcing fibers. In one embodiment, the weft threads of the fabric tape are made of thermoplastic material and / or carbon and / or glass. The weft threads of the fabric tape are preferably made of polyamide, polyester, carbon (in the form of carbon fibers), and / or glass (in the form of glass fibers).

[0017] In one embodiment, the woven tape has warp threads with a fineness between 50 tex and 4000 tex, preferably between 700 and 1700 tex. In one embodiment, the woven tape has weft threads with a fineness between 20 and 400 dtex, preferably between 30 dtex and 150 dtex. Since the weft threads are significantly finer than the reinforcing fibers in the warp direction, the woven tape has the mechanical properties of a unidirectional tape material, but without its disadvantages (limited width availability, fixation of the reinforcing fibers within the tape via nonwoven fabric or bonding with matrix material).

[0018] In one embodiment, the fabric tape has a fiber area weight of 25 to 1000 g / m 2 , preferably from 50 to 800 g / m 2 , particularly preferably from 180 to 750 g / m 2 , most preferably from 250 to 650 g / m 2 , also preferably from 50 to 100 g / m 2 .

[0019] In one embodiment, the woven tape has a two-component material as the weft thread. For example, the weft thread can consist of a core-sheath thread, wherein the core consists of a material with a higher melting point than the sheath. However, it would also be possible for the weft thread to be formed from different fibers. For example, the weft thread can have at least two different fiber types, wherein the fiber types differ from one another at least in their melting points (one fiber type with a low melting point, one fiber type with a high melting point). When using fibers or fiber materials with different melting points for the weft thread or the weft yarn, the melting temperature of the first component of the weft thread material is preferably in a range from 70 to 150°C and / or the melting temperature of the second component of the weft thread material is in a range above 150°C.The weft thread can also consist of only one component, for example of a fiber type made from a single material or a single material mixture.

[0020] In one embodiment, the fabric tape has a twill weave, plain weave, and / or satin weave, and / or derivatives of these weave types. The weave type can advantageously be used to adjust the fabric density. Fabrics with a high weave density are generally more difficult to impregnate than fabrics with a low weave density. Those skilled in the art know that the fabric density depends not only on the weave but also on the fiber material used and its fineness, as well as the number of threads per cm, and that these parameters influence each other.

[0021] In one embodiment of the concept, the fabric tape has a fabric density ranging from 1 thread / cm to 3 threads / cm. With a high fabric density, the fabric tape is particularly resistant to displacement, allowing for good alignment of the reinforcing fibers in the preform and reducing the risk of displacement of the reinforcing fibers during the deposition process in the DFP process. A low fabric density generally facilitates the impregnation of the fabric material and thus the preform.

[0022] In one embodiment, the woven tape has a weft thread density of 0.25 threads / cm to 5 threads / cm, preferably 0.5 threads / cm to 4 threads / cm. In one embodiment, a core-sheath thread is used as the weft thread. The sheath material of the weft thread consists of a material with a melting point that is (far) below the impregnation temperature for manufacturing the component. During storage, assembly, and processing (in the DFP process), the woven tape is particularly resistant to displacement and easy to handle due to the high weft thread density. Nevertheless, the preform - made from the woven tape - can be very well impregnated because the weft thread melts early on during impregnation, at least in the sheath area, thereby creating passages in the woven tape for the impregnation.Advantageously, the choice of fabric tape can provide a material that is resistant to displacement for the automatic deposition process, without having to accept the disadvantage of poor impregnability.

[0023] In one embodiment, the fabric tape has a nonwoven material on at least one side. The nonwoven material is preferably located on one surface of the fabric tape and is bonded to the fabric tape (for example, by hot melt bonding). In one embodiment, the fabric tape has a coating of matrix material on at least one side. The matrix material is preferably located on an upper side of the fabric tape and preferably has a basis weight-related proportion of 0.25% - 5%. The fabric tape can also have a nonwoven material on both sides (on both surfaces) or have a coating of matrix material on both surfaces. In one embodiment, the fabric tape can also have a matrix material on a first surface and be bonded to a nonwoven material on the second surface.To make the fabric tape suitable for deposition in a DFP process, a powder binder can be applied and / or a nonwoven backing can be applied to the fabric tape to ensure or improve the adhesion of the individual fabric tape layers to one another. If necessary, a nonwoven can also be used purely for impact modification. Preferably, the reinforcing fibers in the fabric tape (preferably the reinforcing fibers within a layer of the fabric tape) are bonded to the warp threads by melt bonding. Particularly preferably, the melt bonding occurs through the weft threads themselves. In one embodiment, melt bonding between the fabric tapes deposited on top of one another in the preform can also occur through the weft threads of at least one of the fabric tapes.Thus, when using a fabric tape with melt-bondable weft threads, not only can a connection to the warp threads be achieved within the fabric tape, but also a melt bond within the preform (different layers of the fabric tape laid on top of each other), whereby a preform made from multiple layers (or plies) of fabric tape layers is stabilized without impregnation with an additional matrix material and without the use of an additional binder material. The use of an additional image material, which must, for example, be sprayed onto the fabric tape or sprinkled on as a powder, is thus advantageously eliminated.In one embodiment, the reinforcing fibers used in the warp direction are connected by melt bonding the weft threads within the fabric tape and in the laying process (preferably a DFP process) a melt bond is additionally made with adjacent layers, for example further fabric tape layers, nonwoven layers, tool surfaces or adjacent material or glass layers or lightning protection layers, through the weft threads.

[0024] In one embodiment of the fabric tape, the reinforcing fibers used in the warp direction are connected to one another by melt bonding the weft threads, whereby at the same time the nonwoven is fixed to the fabric tape by means of the melt bonding.

[0025] In another embodiment, the fabric tape is connected to further layers (for example fabric tape layers laid thereon or further textile or non-textile layers) via a melt bond to the weft threads of the fabric tape, without the weft threads and the warp threads being connected via a melt bond.

[0026] Preferably, the fabric tape has a width in the range from 6 mm to 80 mm, preferably from 10 mm to 70 mm, more preferably from 25 mm to 40 mm.

[0027] A further subject matter of the present invention relates to a preform produced by a method using a fabric tape as described above. Yet another subject matter of the present invention relates to the fabric tape itself for use in the method as described above.

[0028] All statements regarding the process and the fabric tape to be used in this process should therefore also apply to the preform, where appropriate. On the other hand, statements regarding the preform should also apply to the process and the fabric tape, where appropriate.

[0029] The preform is preferably a molded part for producing an aircraft or vehicle component, wherein the preform is impregnated with a resin material (matrix material) to complete the component. Impregnation is preferably carried out under pressure and heat, although the preform can also be evacuated for impregnation. An epoxy resin, for example, can be used as the matrix material. In contrast to sheet molding compounds (SMC), the preform already has the contour of the finished component, whereby the fabric strip has been laid down within the preform to accommodate the load, yet preforms with strong contours can still be produced using the process. By using a fabric strip instead of a unidirectional strip, the preform can have a lower (initial) matrix material content than a preform produced using a DFP process with unidirectional strip material.For example, the preform constructed according to this idea can have an (initial) matrix material content of less than 10 wt% – based on the total fiber area weight of the preform – before impregnation. Furthermore, the preform constructed according to the new process can have a permeability in the range of 5*10'. 13 m 2 up to 5*10' 10 m 2 , preferably from 1*10 -12 up to 2*10' 1 ° m 2 The new preform therefore differs from preforms produced by known DFP processes using unidirectional non-woven fabrics due to its matrix material content and / or its permeability. The concept is described in more detail below with reference to a figure, which represents only one embodiment of the concept and is not to be understood as a limitation of the general concept.

[0030] Figure 1 schematically shows a fabric belt for use in a DFP process. Figure 1 schematically shows a fabric belt 1 comprising weft threads 2 and warp threads 3, 3', 3". Each of the warp threads 3, 3', 3" is preferably a roving of carbon fibers that are laid spread apart next to each other, but not adjacent to each other. The weft threads 2 interweave with the warp threads 3, 3', 3", thus forming the fabric belt 1.

Claims

Claims:

1. Automatic manufacturing method for producing a preform for the construction of fiber-reinforced components, wherein in the manufacturing method reinforcing fiber material is deposited on a tool surface along a predetermined path in a robot-guided manner, characterized in that the reinforcing fiber material is reinforcing fibers and the reinforcing fibers are in the form of a fabric tape (1) with warp threads (3) and weft threads (2), wherein the fabric tape has only one warp layer and one weft layer and the warp threads and the weft threads are each axially aligned within their layer and the preform is formed by the automatic deposition of this fabric tape (1).

2. Automatic manufacturing method according to claim 1, wherein a fabric tape (1) with reinforcing fibers as warp threads (3) is used in the method, wherein carbon fibers are preferably used as reinforcing fibers.

3. Automatic manufacturing process according to at least one of the preceding claims, wherein a fabric tape (1) with weft threads (2) made of thermoplastic material is used in the process, preferably the thermoplastic material consists of polyamide and / or polyester.

4. Automatic manufacturing process according to at least one of the preceding claims, wherein a fabric tape (1) with yarns having a fineness between 50 tex and 4000 tex, preferably between 700 and 1700 tex, is used in the process for the warp threads (3).

5. Automatic manufacturing process according to at least one of the preceding claims, wherein in the process a fabric tape (1) with a fiber area weight of 25 g / m 2 up to 1000 g / m 2 is used.

6. Automatic manufacturing process according to at least one of the preceding claims, wherein in the process a fabric tape (1) with yarns with a fineness between 20 and 400 dtex, preferably between 30 dtex and 150 dtex is used for the weft threads (2).

7. Automatic manufacturing process according to one of the preceding claims, wherein a fabric tape (1) with a twill weave, plain weave and / or satin weave and derivatives thereof is used in the process.

8. Automatic manufacturing process according to one of the preceding claims, wherein a fabric tape (1) with a weft thread density of 0.25 threads / cm to 5 threads / cm, preferably of 0.5 threads / cm to 4 threads / cm, is used in the process.

9. Automatic manufacturing method according to one of the preceding claims, wherein the method uses a fabric tape (1) which is connected on at least one side to a nonwoven material.

10. Automatic manufacturing process according to one of the preceding claims, wherein the process uses a fabric tape (1) which is coated on at least one side with a matrix material, preferably with a matrix material content of 0.25% - 5% based on the weight per unit area. 11.Automatic manufacturing process according to at least one of the preceding claims, wherein the process uses a fabric tape (1) in which the reinforcing fibers are also bonded to the warp threads (3) by melt bonding.

12. Automatic manufacturing process according to at least one of the preceding claims, wherein the process uses a fabric tape (1) which is connected to further layers to form the preform by melt bonding through the weft threads (2) of the fabric tape (1).

13. Automatic manufacturing process according to at least one of the preceding claims, wherein a fabric tape (1) with a width in the range of 6 mm to 80 mm is used in the process.

14. Preform produced by an automatic manufacturing process according to claims 1 to 13.

15. Fabric tape for use in an automatic manufacturing process according to claims 1 to 13.