Method and apparatus for the production of a semi-finished product

Abstract

Method for producing a semi-finished product (70) comprising the following process steps: Providing a fiber-reinforced plastic composite (20) having a unidirectionally fiber-reinforced thermoplastic matrix, Heating the fiber-reinforced plastic composite (20) to a temperature at which the matrix is ​​in a plasticized state, and Forming at least one additional material area (22) in the form of folds or loops at a respective predetermined location of the fiber-reinforced plastic composite (20) by a relative movement between the heated fiber-reinforced plastic composite (20) and a depositing device (60) on which the heated fiber-reinforced plastic composite (20) is deposited, or by a relative movement between the fiber-reinforced plastic composite (20) and a heat treatment device (50) that heats the fiber-reinforced plastic composite (20).

Description

[0001] The present invention relates to a method and a device for producing a semi-finished product from a fiber-plastic composite having a unidirectional fiber-reinforced thermoplastic matrix.

[0002] Lightweight components are playing an increasingly important role, particularly in automotive, shipbuilding, and aircraft construction. Component weight is achieved through the use of low-density materials and / or through design features such as honeycomb structures.

[0003] A fiber-reinforced composite with a unidirectional fiber-reinforced matrix is ​​ideal for use in lightweight components due to its low weight and high mechanical strength.

[0004] A fiber composite component for use in lightweight construction, particularly for aircraft or spacecraft, is known, for example, from DE 10 2008 006 523 A1. Such a fiber composite component comprises electrically conductive fibers that are used to improve lightning protection properties or can be coupled to an energy source to de-ice the fiber composite component during flight.

[0005] Further related prior art is known from US 8 771 452 B2, DE 25 18 456 A1 and DE 15 79 027 A.

[0006] Commonly used reinforcing fibers such as glass or carbon fibers cannot be plastically stretched due to their molecular nature. A semi-finished product made of a fiber-plastic composite with a unidirectionally fiber-reinforced matrix also cannot be plastically stretched in the fiber direction, making the use of forming processes such as those known for metal forming impossible.

[0007] The invention is based on the object of providing a method and apparatus for producing a semi-finished product from a fiber-plastic composite having a unidirectionally fiber-reinforced thermoplastic matrix. The semi-finished product should be suitable for further forming with partial stretching in the fiber direction without having to interrupt the reinforcing fibers.

[0008] This object is achieved by a method according to claim 1 and a device according to claim 7.

[0009] According to the invention, at least one additional material region is formed at a respective predetermined location of a fiber-plastic composite comprising a unidirectionally fiber-reinforced thermoplastic matrix. The additional material region allows the fiber-plastic composite to undergo a forming process in which the additional material region at least partially unfolds or stretches without interrupting the fiber flow. This makes it possible to form a semi-finished product made of a fiber-plastic composite into a component that has high strength and low weight.

[0010] The respective additional material region is suitably adapted to the component to be manufactured. According to the invention, the respective additional material region is formed in the form of folds or loops. The fiber-plastic composite preferably contains long fibers or continuous fibers, which allows for the production of components with very high strength.

[0011] To create an additional material area, for example, in the form of folds or loops, the fiber-plastic composite is heated. Heating of the fiber-plastic composite can be achieved by conduction, absorption of radiant energy, or electrical resistance heating. This allows conventional heat treatment processes to be used.

[0012] In a modified embodiment, the fiber-plastic composite is melted directly by applying electrical energy. For this to happen, the fiber-plastic composite must be electrically conductive. This can be achieved either by heating wires within the fiber-plastic composite or by using carbon fibers as reinforcing fibers, which make the entire fiber-plastic composite electrically conductive.

[0013] The fiber-plastic composite is preferably in the form of a tape wound on a spool. This allows for easy transport and storage of the fiber-plastic composite. Furthermore, unwinding the tape from the spool and a subsequent separation process facilitate handling for series production of semi-finished products.

[0014] The separation process can be performed before or after heating the fiber-reinforced plastic composite. This allows the separation process to be optimized for the respective manufacturing process.

[0015] According to the invention, the additional material region is created by a relative movement between the heated fiber-plastic composite and a depositing device on which the heated fiber-plastic composite is deposited, or by a relative movement between the fiber-plastic composite and a heat treatment device that heats the fiber-plastic composite. This allows the shape and dimensions of the additional material regions for forming the semi-finished product to be created in a simple manner.

[0016] The semi-finished product is then preferably subjected to a cooling process. This allows for easy transport of the semi-finished product to a forming device.

[0017] In an alternative embodiment, the semi-finished product is immediately subjected to a forming process while heated. This eliminates the need for reheating the semi-finished product.

[0018] In a preferred embodiment, the semifinished product is deposited on a liner or membrane to form a semifinished component, or is wound around a geometric object, in particular a pipe. In this way, forming processes such as hydroforming can be used.

[0019] Embodiments of the invention are explained in more detail with reference to the drawings, in which: Fig. 1 a device for producing the semi-finished product, and Fig. 2 a schematic view to explain a forming of a semi-finished component.

[0020] As in Fig. 1, a device 100 for producing a semi-finished product comprises a storage device 10 for storing a unidirectionally fiber-reinforced strip 20 with a thermoplastic matrix, a transport device 30, a separating device 40, a heat treatment device 50 and a storage device 60.

[0021] The storage device 10 is configured in the form of a freely rotatably mounted reel on which the tape 20 is wound. In a modified embodiment, the storage device 10 can also store the tape 20 in the form of layers or a spread-out tape. The tape 20 can also be prefabricated, in which case the separating device 40 can be omitted.

[0022] The belt 20 represents the fiber-plastic composite of the present invention and comprises a thermoplastic matrix, e.g., polypropylene, polyamide, or polyester, and long or continuous fibers, e.g., carbon fibers or glass fibers, arranged in the thermoplastic matrix. In the preferred embodiment, the fiber-plastic composite has a high fiber volume content.

[0023] The strip 20 is transported to a heat treatment device 50 by means of the transport device 30, which in the embodiment shown is represented by two rollers 32, 34 arranged opposite one another and pressed against the strip 20. The heat treatment device 50 is designed as a heated nozzle that heats the strip 20 to a temperature such that the strip 20 is brought into a plasticized state.

[0024] In modified embodiments, a heat treatment device 50 is used that operates on the basis of heat conduction, absorption of radiant energy, or electrical resistance heating. Heating of the strip 20 can also be achieved directly by resistance heating, e.g., by heating wires inserted into the strip 20 or by using carbon fibers to reinforce the plastic, which are connected or connectable to an energy source.

[0025] As in Fig. 1, a cutting device 40 is used to cut the strip 20 to length. The cutting device 40, which in the embodiment shown has two counter-rotating knives 42, 44, is arranged upstream of the heat treatment device 50. In a modified embodiment, the cutting device 40 is arranged downstream of the heat treatment device 50.

[0026] After leaving the heat treatment device 50, the strip 20 with the molten matrix is ​​positioned on the deposition device 60. A relative movement between the heated strip 20 and the deposition device 60 forms folds or loops 22, which represent the respective additional material region according to the present invention. The strip 20 formed with folds or loops 22 represents a semi-finished product 70 according to the present invention.

[0027] The respective additional material areas, ie the folds or loops 22, are adapted to the component to be manufactured, wherein, for example, the length of a loop 22 or several loops 22 represents the height of a recess in the component.

[0028] In the embodiment shown, the depositing device 60 is a conveyor belt 62 that is movable in a forward direction V and a reverse direction R running opposite thereto. This creates a relative movement to the belt 20 emerging from the heat treatment device 50 and the depositing device 60, and the folds or loops 22 are formed. In a modified embodiment, in addition to the relative movement in the forward direction V and reverse direction R, a relative movement at an angle to the forward direction V or reverse direction R can occur, so that folds or loops 22 with a changing width are formed in a direction transverse to the forward direction V and reverse direction R.

[0029] A relative movement can also be effected by a laying head (not shown) which positions the strip 20 in the desired manner on the depositing device 60.

[0030] The semi-finished product 70 is subjected to a cooling process by means of a cooling device (not shown).

[0031] The semi-finished product 70 can be further processed using a suitable forming process, such as thermoforming, deep drawing, internal high-pressure forming, or other methods. The folds or loops 22 are adapted in their dimensions to the component to be manufactured. During the forming process, the folds or loops 22 can unfold or stretch completely or partially without interrupting the fiber flow. This gives the manufactured component high strength and low weight.

[0032] In a modified embodiment, a liner 64 or a membrane 64 is provided as the depositing device 60, onto which the semifinished product 70 is deposited to form a semifinished component. In another embodiment, the belt 20 formed with folds or loops 22 is applied to a geometric object, such as a pipe. The liner, the membrane, or the geometric object can also be arranged on the conveyor belt 62.

[0033] Advantageously, the pipe, liner, or membrane is made of a thermoplastic or an elastomer. Depositing it on a pipe, liner, or membrane allows the semifinished product 70 to be deformed by means of a forming process using a liquid or gaseous medium.

[0034] Fig.Figure 2 schematically shows a portion of a semi-finished component 72 comprising a tube wrapped with the band 20 formed with folds or loops 22. In this embodiment, the tube is made of a thermoplastic material. Internal high-pressure forming is used to pressurize the interior space 72a of the heated semi-finished component 72, allowing the desired shape to be achieved. The component manufactured in this way has particularly high strength and low weight.

Claims

[1] Method for producing a semi-finished product (70) comprising the following process steps: Providing a fiber-plastic composite (20) having a unidirectional fiber-reinforced thermoplastic matrix, Heating the fiber-plastic composite (20) to a temperature at which the matrix is ​​in a plasticized state, and Forming at least one additional material region (22) in the form of folds or loops at a respective predetermined location of the fiber-plastic composite (20) by a relative movement between the heated fiber-plastic composite (20) and a depositing device (60) on which the heated fiber-plastic composite (20) is deposited, or by a relative movement between the fiber-plastic composite (20) and a heat treatment device (50) which heats the fiber-plastic composite (20). [2] Method according to claim 1, characterized bythat the fibre-plastic composite (20) contains long fibres or continuous fibres. [3] Method according to one of claims 1 or 2, characterized by that the heating of the fiber-plastic composite (20) is carried out by means of heat conduction, absorption of radiant energy or electrical resistance heating. [4] Method according to one of claims 1 to 3, characterized by that the fiber-plastic composite (20) is in the form of a band (20) which is cut to a predetermined length before or after heating. [5] Method according to one of claims 1 to 4, characterized by that the semi-finished product (70) is cooled after the additional material area (22) has been formed. [6] Method according to one of claims 1 to 5, characterized by that the semi-finished product (70) is placed on a liner or a membrane to form a semi-finished product component (72) or is applied to a geometric object (64), in particular a pipe. [7] Device (100) for producing a semi-finished product (70) from a fiber-plastic composite (20) having a unidirectional fiber-reinforced thermoplastic matrix, with a heat treatment device (50) for heating the fiber-plastic composite (20) to a temperature at which the matrix is ​​in a plasticized state, and a depositing device (60) for depositing the heated fiber-plastic composite (20), wherein the heat treatment device (50) and / or the depositing device (60) are configured to form at least one additional material region in the form of loops or folds at a respective predetermined location of the fiber-plastic composite (20) by a relative movement between the heated fiber-plastic composite (20) and the depositing device (60) or by a relative movement between the fiber-plastic composite (20) and the heat treatment device (50). [8] Device according to claim 7, characterized by a storage device (10) for storing the fiber-plastic composite (20) and a transport device (30) for transporting the fiber-plastic composite (20) from the storage device (10) to the heat treatment device (50). [9] Device according to claim 8, characterized by a separating device (40) for assembling the fiber-plastic composite (20). [10] Device according to one of claims 7 to 9, characterized by a liner, a membrane or a geometric object (64) to which the semi-finished product (70) can be applied to form a semi-finished product component (72).

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