METHOD AND APPARATUS FOR IMPREGNATING A FIBRE BUNDLE AND METHOD AND FACILITY FOR PRODUCING A THREE-DIMENSIONAL STRUCTURE

Abstract

The invention relates to a method for impregnating at least one fibre bundle (11) with a high-viscosity plastics material (13), said method comprising the following steps: •—providing at least one fibre bundle (11) for impregnation, formed of a multiplicity of continuous fibres, and providing a plastics material (13), melted at a mandated operating temperature and of high viscosity, and •—impregnating the fibre bundle (11) with the plastics material (13), by guiding the fibre bundle for impregnation continuously through an impregnation cavity (12), filled with the melted plastics material (13), •—where during impregnation of the fibre bundle, the melted plastics material within the impregnation cavity is contacted with a surface (15) of at least one oscillation generator (14) in such a way that sonic energy is introduced by said oscillation generator into the melted high-viscosity plastics material in the impregnation cavity.

Claims

1. A method for impregnating at least one fiber bundle with a highly viscous plastics material providing at least one fiber bundle to be impregnated, wherein the at least on fiber bundle is formed from a multiplicity of endless fibers, providing a plastics material which is molten and highly viscous at a predefined process temperature, and impregnating the at least one fiber bundle with the plastics material by continuously guiding the at least one fiber bundle to be impregnated through an impregnation cavity which is filled with the plastics material while the plastics material is in a molten and highly viscous state, wherein, during the impregnation of the at least one fiber bundle, the plastics material located in the impregnation cavity is in contact with a surface of at least one vibration generator such that sound energy is introduced into the plastics material while the plastics material is in the molten and highly viscous state.

2. The method as claimed in claim 1, wherein the plastics material is a thermoplastic material.

3. The method as claimed in claim 1 wherein the vibration generator generates a vibration amplitude of between 1 μm and 150 μm, and/or wherein the vibration generator generates a vibration frequency of between 100 Hz and 100 kHz.

4. The method as claimed in claim 1 wherein the vibration generator induces real and/or complex eigenmodes of a structure of the impregnation cavity.

5. The method as claimed in claim 1 wherein the surface of the vibration generator in contact with the molten plastics material is subjected to a microstructuring, roughening and/or plasma pretreatment or is provided such that adhesion and/or wetting of the surface of the vibration generator with the plastics material is better than if no treatment of the surface is provided.

6. The method as claimed in claim 1 wherein the plastics material is physically modified so as to reduce forces of cohesion.

7. The method as claimed in claim 1 wherein the at least one fiber bundle in the impregnation cavity is guided through the surface of the vibration generator, and wherein the surface of the vibration generator at least partially encloses the at least one fiber bundle while the surface of the vibration generator is in contact with the plastics material while it is in the molten and highly viscous state.

8. The method as claimed in claim 1 wherein the plastics material is guided or flows through the impregnation cavity together with the at least one fiber bundle.

9. The method as claimed in claim 1 further comprising applying a pressure to the molten plastics material in the impregnation cavity during the impregnation of the at least one fiber bundle.

10. A method for producing a three-dimensional structure which is formed from two or more different materials by a three-dimensional (3D) printhead of a 3D printing installation, comprising: feeding a plastics material in a molten and highly viscous state as a first material and a virtually endless fiber bundle of a fiber material as a second material to the 3D printing installation, wherein the first material and the second material are continuously fed to an impregnation cavity of the 3D printing installation in order to impregnate the virtually endless fiber bundle with the plastics material, extruding the fiber bundle impregnated with the plastics material from a 3D printhead of the 3D printing installation, wherein, during the production of the three-dimensional structure, the virtually endless fiber bundle is continuously impregnated with the plastics material by the method as claimed in claim 1.

11. A device for impregnating at least one fiber bundle, which is formed from a multiplicity of endless fibers with a plastics material which is molten and highly viscous at a predefined process temperature, comprising: an impregnation cavity, into which the plastics material in a molten and highly viscous state has been filled or can be filled, wherein the impregnation cavity has an inlet and an outlet configured in such a way that the at least one fiber bundle to be impregnated is guided through the plastics material in the impregnation cavity that is in the molten and highly viscous state, and a vibration generator which has a surface in contact with or can be brought into contact with the plastics material located in the impregnation cavity that is in the molten and highly viscous state, wherein the vibration generator is designed to introduce sound energy into the plastics material that is in the molten and highly viscous state.

12. The device as claimed in claim 11, wherein the vibration generator is designed to generate a vibration amplitude of between 1 μm and 150 μm, and/or to generate a vibration frequency of between 100 Hz and 100 kHz.

13. The device as claimed in claim 11, wherein the vibration generator is configured to generate vibrations in such a way that real and/or complex eigenmodes of a structure of the impregnation cavity are induced.

14. The device as claimed in claim 11 wherein the surface which is in contact with or can be brought into contact with the plastics material while in the molten and highly viscous state has a microstructuring, roughening and/or plasma treatment in order to improve the adhesion and/or wetting of the surface of the vibration generator with the plastics material.

15. The device as claimed in claim 11 wherein the surface of the vibration generator has a cavity, through which the at least one fiber bundle to be impregnated is guided when the at least one fiber bundle is being guided through the plastics material of the impregnation cavity that is in the molten and highly viscous state.

16. The device as claimed in claim 15, wherein the cavity of the surface of the vibration generator forms a tube through which the at least one fiber bundle is guidable in order to be impregnated with plastics material, wherein the tube has a modally vibrating structure and/or a vibrating structure with eigenmodes.

17. An installation for producing a three-dimensional structure formed from two or more different materials, comprising: a 3D printhead which a first material feed for feeding a virtually endless fiber bundle of a fiber material and at least one second material feed for feeding a plastics material, which is molten and highly viscous at a predefined process temperature, an impregnation cavity into which the first material feed and the at least one second material feed of the 3D printhead open into in order to impregnate the fiber bundle with the plastics material while in a molten and highly viscous state, wherein the impregnation cavity is communicatively connected to an outlet of the 3D printhead, wherein the outlet is configured to extrude an impregnated fiber bundle to produce the three-dimensional structure, and wherein the impregnation cavity is part of a device as claimed in.

18. The device of claim 11 wherein the vibration generator generates a vibration amplitude of 1 to 40 μm.

19. The device of claim wherein the vibration generator generates a vibration frequency of 15 to 60 kHz.

Description

[0047] The invention is explained by way of example with reference to the appended figures, in which:

[0048] FIG. 1 shows a schematic illustration of the device according to the invention for impregnating;

[0049] FIG. 2 shows a schematic illustration of the device in a first embodiment;

[0050] FIG. 3 shows a schematic illustration of the device in a second embodiment;

[0051] FIG. 4 shows a schematic illustration of the device with a modally vibrating structure;

[0052] FIG. 5 shows a schematic illustration of the impregnation cavity with eigenmodes;

[0053] FIG. 6 shows a schematic illustration of an impregnation cavity with an outlet nozzle.

[0054] FIG. 1 shows a greatly simplified schematic representation of a device 10 for impregnating a fiber bundle 11 which is guided through an impregnation cavity 12. Here, the impregnation cavity 12 is filled with a highly viscous and molten plastics material 13 with which the fiber bundle 11 is to be impregnated.

[0055] Furthermore, the device 10 has a vibration generator 14, a surface 15 of which is in contact with the molten and highly viscous plastics material 13. The vibration generator 14 shown in FIG. 1 is a longitudinal vibrator, which performs a stroke movement in the form of an amplitude s in order to introduce the sound energy into the highly viscous plastics material 13 at a predefined frequency f. In this respect, in the exemplary embodiment in FIG. 1 the direction of the stroke movement is essentially perpendicular to the fiber bundle 11.

[0056] By virtue of the fact that the surface 15 of the vibration generator 14 is in direct contact with the highly viscous and molten plastics material 13, the vibrations generated by the vibration generator 14 can be introduced into the plastics material 13 in the form of sound energy in order to improve the impregnation performance of the fiber bundle 11.

[0057] It can be provided here that the surface 15 of the vibration generator 13 is subjected to a microstructuring, roughening and/or plasma pretreatment in order to improve the adhesion between the surface 15 of the vibration generator 14 and the molten and highly viscous plastics material 13. This has the effect that no cavities, which impede or even entirely prevent coupling of the vibrations of the vibration generator 14 into the plastics material 13, form between the surface 15 of the vibration generator 14 and the plastics material 13 during the vibrating.

[0058] The right-hand side of FIG. 1 shows various possible cross-sectional shapes of the vibration generator 14 which, as the surface 15, are intended to couple the vibrations generated by the vibration generator 14 into the highly viscous plastics material.

[0059] FIG. 2 schematically shows the device 10, in the case of which the vibration generator 14 has a recess, which partially or completely encloses the fiber bundle guided through the impregnation cavity, specifically in full contact with the highly viscous plastics material, in the region of its surface 15, by way of which the vibration generator is in contact with the highly viscous plastics material. The roving 11 is accordingly guided through a type of “hole” in the longitudinal vibrator which has a particular profile geometry, wherein in the process the fibers of the roving can be in contact with the surface of the longitudinal vibrator 14 at certain points. The particular geometry prevents the material from being closed off or ensures that the vibration energy is coupled in through zones of excess pressure and negative pressure in an improved manner.

[0060] FIG. 3 schematically shows a further embodiment of the device 10, in the case of which a counterpart or a counterpart element 16 is situated opposite the vibration generator 14 in such a way that the fiber bundle 11 is guided through between the surface 15 of the vibration generator 14 and the counterpart 16.

[0061] The counterpart 16 may be for example a reflection element, which is arranged in the impregnation cavity 12 and reflects the sound waves coupled in by the vibration generator 14, as a result of which the influence or the action of the sound waves on the impregnation process can be improved.

[0062] It is of course also conceivable that the counterpart 16 is likewise a vibration generator that can actively introduce sound waves into the highly viscous plastics material, wherein the frequency and amplitude of the two vibration generators 14 and 16 can be matched such that the greatest possible effect of impregnating the roving can be achieved.

[0063] FIG. 4 shows a highly simplified schematic view of an embodiment, in the case of which a slightly spread-open roving is pulled through a highly viscous plastics material, wherein located in the impregnation cavity 12 is a modally vibrating structure 17 which, in the form of a vibration generator, is intended to introduce corresponding sound energy into the highly viscous plastics material. Here, the vibration maxima and vibration minima that arise couple the vibration energy into the highly viscous plastics material in a spatially distributed manner.

[0064] FIG. 5 shows a further exemplary embodiment of a modally vibrating structure 18 with eigenmodes, which is designed such that it completely encloses the roving 11. In this case, the surface of the vibration generator is formed by the modally vibrating structures 17 and 18, wherein the vibration generator is designed in such a way that real and/or complex eigenmodes of these structures 17 and 18 can be induced.

[0065] Here, these modally vibrating structures 17 and 18 are located within the impregnation cavity 12 and can preferably be completely enclosed by the highly viscous plastics material 12. This makes it possible to introduce the sound energy required to improve the impregnation performance into the plastics material very effectively. In addition, an embodiment of this type only requires very little structural space and is accordingly suitable especially for generative methods.

[0066] However, it is also conceivable that the modally vibrating structure 18 in the form of a tube, shown in FIG. 5, forms the actual impregnation cavity, and therefore the tube 18 is the impregnation cavity. For this purpose, the tube 18 has an inlet 19a and an outlet 19b, with the result that the fiber material 11 is guided through the inlet 19a into the interior of the tube and is guided out again through the outlet 19b. Furthermore located inside the tube 18 is the molten plastics material, wherein the sound energy is introduced into the molten plastics material through the tube 18 in the form of a modally vibrating structure with eigenmodes. In this exemplary embodiment, intentionally no plastics material is located outside the tube; said plastics material is present only in the tube, together with the fiber material.

[0067] FIG. 6 shows a greatly simplified illustration of the device 10 in a further embodiment. The device 10 has an impregnation cavity 12, through which the fiber bundle 11 and the highly viscous plastics material 13 are guided. Furthermore, the vibration generator 14 in the form of a sonotrode protrudes into the impregnation cavity 12 in such a way that the vibration generator 14 is in contact with the molten plastics material 13 without making contact with the fiber bundle 11 in the impregnation cavity. The vibration generator 14 can thus be used to introduce sound energy into the molten plastics material 13.

[0068] Both the fiber bundle 11 (which is not impregnated, not completely impregnated or not sufficiently impregnated) and the molten plastics material 13 are introduced into the device 10 via an inlet 19a, with the result that the fiber bundle 11 and the molten plastics material 13 can be introduced into the impregnation cavity 12. The fiber bundle 11 impregnated with the plastics material 13 is then guided out of the device 10 from an outlet 19b.

[0069] In this respect, the outlet 19b is designed in the form of an extruder or a nozzle for shaping and consolidating the plastics material. By shaping the outlet 19b in the form of a nozzle or an extruder by contrast with the inlet, a pressure gradient can be created in the plastics material 13 between the inlet 19a and the outlet 19b. Here, the melt pressure may be between 15 bar and 100 bar, if appropriate 400 bar.

[0070] In this respect, the inlet 19a is designed for the pressure-tight feed of the fiber bundle 11 and the molten plastics material 13. The outlet 19b may be designed here to be pressure-tight, in particular with respect to the molten plastics material.

[0071] In this respect, the vibration generator 14 is likewise arranged on the device 10 in a pressure-tight manner with respect to the impregnation cavity 12.

[0072] Imprinting the molten plastics material 13 with a pressure or forming a pressure gradient can have the effect, in conjunction with the introduction of the sound energy by the vibration generator 14, that cavitations form and disperse in the molten plastics material 13, which cavitations result in a significant improvement in the impregnation result. It has been found that the microjets and/or shock waves (cavitation effects) which are produced when the cavitations disperse result in an improvement in the impregnation, in particular when using highly viscous plastics materials.

[0073] Guide elements 20 are located between the inlet 19a and upstream of the outlet 19b in order to guide the fiber material 11 at the correct position through the impregnation cavity 12. In this case, the sonotrode 14 or the vibration generator is arranged between the guide elements 20.

[0074] Here, the vibration generator 14 is connected to the device 10 via a pressure-tight attachment 23. The temperature and the pressure can be continuously monitored via a sensor 22 in the region of the impregnation cavity 12.

[0075] Finally, the impregnated fiber roving 21 is guided out at the outlet 19b.

LIST OF REFERENCE SIGNS

[0076] 10 Device [0077] 11 Fiber bundle/roving [0078] 12 Impregnation cavity [0079] 13 Highly viscous plastics material [0080] 14 Vibration generator [0081] 15 Surface of the vibration generator [0082] 16 Counterpart/counterpart element [0083] 17 Modally vibrating plate structure [0084] 18 Modally vibrating tube with eigenmodes [0085] 19a Inlet [0086] 19b Outlet [0087] 20 Guide elements [0088] 21 Impregnated fiber roving [0089] 22 Sensor [0090] 23 Pressure-tight attachment