Method and apparatus for impregnating a fiber bundle, and method and facility for producing a three-dimensional structure

Abstract

The present invention relates to a method for impregnating at least one fiber bundle (11) with a high-viscosity plastic material (13), said method comprising the following steps: - providing at least one fiber bundle (11) for impregnation formed from a multitude of continuous fibers and providing a plastic material (13) that is molten and highly viscous at a defined use temperature, - impregnating the fiber bundle (11) with the plastic material (13) by continuously guiding the fiber bundle for impregnation through an impregnation cavity (12) filled with the molten plastic material (13), - during the impregnation of the fiber bundle, the molten plastic material in the impregnation cavity is brought into contact with a surface (15) of at least one vibration generator (14) such that acoustic energy is introduced by the vibration generator into the molten high-viscosity plastic material in the impregnation cavity.

Description

Technical Field

[0001] The present invention relates to a method for impregnating at least one fiber bundle with a highly viscous plastic material. The present invention also relates to an apparatus for this purpose. The present invention further relates to a method for producing a three-dimensional structure formed from two or more different materials. The present invention also relates to a facility for producing such a three-dimensional structure.

Background Art

[0002] Due to specific weight-specific strength and stiffness, fiber composite materials have become indispensable as modern materials. However, the combination of fiber materials and plastic materials in three-dimensional (3D) printing also brings new possibilities for producing complex structures, and in this regard, it is not necessary to use isotropic materials. In both the production of fiber composite parts from fiber composite materials and 3D printing with fiber reinforcements, fiber rovings, which constitute a kind of fiber bundle and are formed from a large number of infinite fibers also referred to as filaments, are very frequently used.

[0003] For example, DE102017124352.6 discloses a facility for producing a three-dimensional structure containing two or more different materials. In the process, both a virtually infinite fiber material in the form of roving and a thermoplastic material are supplied to a 3D printing head, and then the 3D printing head opens into a mixing tank in order to impregnate the fiber material with the thermoplastic material in the mixing tank. The material mixture thus formed is then extruded through the outlet of the 3D printing head in order to produce a three-dimensional structure.

[0004] However, the impregnation of virtually infinite fiber rovings with a thermoplastic material is currently not satisfactory, especially when the fiber material is continuously conveyed and extruded, due to the high viscosity of the thermoplastic material and the low permeability of the infinite fibers.

[0005] Practically, it is known and widespread to first spread open the fiber rovings, i.e., to widen the fiber rovings with respect to the width. For this purpose, the fiber rovings are generally guided onto some specially shaped rollers shaped such that the cross-section of the fiber bundle is expanded and thus the distance between the individual filaments is increased. In this way, the required penetration depth of the molten plastic material is reduced and the permeability of the fibers is increased. Next, the molten plastic material is brought into contact with the spread open fibers at one or more positions for a relatively long time under the action of pressure in order to impregnate the spread open fibers.

[0006] For example, EP0712716A1 discloses a method for impregnating endless fibers or fiber bundles with a molten thermoplastic material, wherein the fibers or rovings pass through an impregnation zone having the shape of a damped wave.

[0007] US Patent Application Publication No. 2012 / 0040106A1 discloses a method and apparatus for impregnating a fiber material with a matrix material, in which case the fiber material is introduced into a forming tool and then the matrix material is injected. While the matrix material is being injected into the fiber material, vibrations are generated using a loudspeaker or tone generator in order to improve the result of the impregnation.

[0008] DE102016107956A1 discloses a method for impregnating endless fibers aimed at producing fiber-reinforced semi-finished products, in which method first a plurality of individual fibers are combined to form a common fiber bundle and impregnated with a plastic material. The fiber material impregnated with the plastic material is then extruded onto a cooled roller, which is operatively connected to a sonotrode such that the sonotrode induces ultrasonic vibrations into the fiber material having the matrix material.

[0009] Methods known from the prior art for impregnating fibrous materials, in particular fiber bundles, with a highly viscous plastic material such as a thermoplastic material have various disadvantages. For example, in the case of methods involving fiber opening, a relatively large structural space is required because the fibers have to be deflected multiple times. The maximum allowable bending radius has to be taken into account here so that the fibers are not damaged. The multiple deflections also increase friction and thus the degree of tensile force required for the fibers. This has to be ensured by the process so that the continuous guiding of the fibers is possible. The applied tensile force must not exceed the maximum allowable value here in order to prevent the breakage of the individual filaments of the fiber roving. Processes that do not perform fiber opening or that operate with only a very slight degree of fiber opening reduce the risk of damage to the fibers, but require a long process time for sufficient fiber impregnation.

[0010] Fiber impregnation based on acoustic energy or vibration energy has so far only been known for low-viscosity media. For example, in the case of a highly viscous medium such as a molten thermoplastic material, specific problems arise with regard to the coupling of acoustic or vibration energy into the medium. Therefore, only a small structural space is available, and there is no suitable method available that enables deep impregnation of fiber rovings in a reliable manner in terms of the process for applications where the fibers have to be impregnated with a highly viscous material. SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0011] In view of this background, the object of the present invention is to define an improved method and an improved apparatus that can impregnate fiber rovings, in particular, with a highly viscous plastic material in a reliable manner in terms of process, thereby making it possible to utilize a large structural space or assuming a long process time is not necessary. Similarly, the object of the present invention is to define an improved method for generating a three-dimensional structure and an improved facility that can continuously impregnate fiber rovings with a highly viscous plastic material in order to enable impregnation during printing, particularly in the case of a generative method.

Means for Solving the Problems

[0012] According to the present invention, the above object is achieved by the method according to claim 1 for impregnating a fiber bundle and the apparatus according to claim 11. According to the present invention, the above object is further achieved by the method according to claim 10 for generating a three-dimensional structure and the facility according to claim 17. Advantageous configurations of the present invention can be found in the corresponding dependent claims.

[0013] What is proposed by claim 1 is a method for impregnating at least one fiber bundle with a highly viscous plastic material. For this purpose, first, at least one fiber bundle to be impregnated, formed from a plurality of infinite fibers (known as filaments), and a plastic material that is melted at a predetermined process temperature and is highly viscous are provided. The highly viscous plastic material is here understood to mean, in particular, a plastic material having a viscosity exceeding essentially 8000 mPa·s (millipascal seconds) at the predetermined process temperature. Here, it is necessary to distinguish it from a low-viscosity plastic material having a viscosity up to 300 mPa·s. An average viscosity of 300 mPa·s to 8000 mPa·s is referred to. Thermoplastic materials, as often seen in hybrid 3D printing, often have a viscosity of 300 Pa·s to 10000 Pa·s. Depending on the degree to which the plastic material is sheared when the plastic material comes into contact with the fibers, the viscosity can also be significantly lower than the normal zero-shear viscosity (3000 to 10000 Pa·s). The predetermined process temperature is understood to mean the temperature of the plastic material at which the plastic material is used for impregnation. In the case of a thermoplastic material, this is in particular the temperature at which the plastic material is melted and can thus impregnate the fiber bundle accordingly.

[0014] The fiber bundle intended is then impregnated with a plastic material by continuously guiding the fiber bundle to be impregnated, such as roving, through an impregnation cavity. In the process, a temperature-controlled molten highly viscous plastic material is located in the impregnation cavity, so that when the fiber bundle is guided through the impregnation cavity, the fiber bundle is completely surrounded by the molten plastic material located in the impregnation cavity. Here, the impregnation cavity can be filled with a plastic material so that there is no air in the impregnation cavity during the impregnation process. In this regard, in order to ensure a continuous impregnation operation, it is of course also possible to continuously supply fresh plastic material to the impregnation cavity during the continuous passage of the fiber bundle. Furthermore, it is of course also possible for the impregnation cavity to have a temperature control device in order to heat the impregnation cavity to a predetermined process temperature of the highly viscous plastic material. Thus, it is advantageous if, during the continuous passage of the fiber bundle through the impregnation cavity, fresh plastic material is continuously added to the impregnation cavity and / or the temperature of the plastic material located in the impregnation cavity is continuously controlled in order to maintain the plastic material at a particularly desired process temperature.

[0015] According to the invention, now, during the impregnation of the fiber bundle, the molten highly viscous plastic material located in the impregnation cavity is provided to contact at least one surface of a vibration generator so that acoustic energy is introduced into the molten highly viscous plastic material in the impregnation cavity by the vibration generator.

[0016] For this purpose, at least one oscillator has a surface that comes into direct contact with the molten highly viscous plastic material of the impregnation cavity, and the oscillator is designed to generate vibrations, which are then transmitted to the plastic material in the form of acoustic energy through the surface in contact with the plastic material. The vibrations of the oscillator thus generate sound waves or pressure waves within the molten highly viscous plastic material, and these sound waves or pressure waves cause the highly viscous plastic material to penetrate deeply into the fiber bundle in the process and wet the individual filaments or continuous fibers. In particular, the intermediate spaces between the individual filaments or continuous fibers of the fiber bundle are here occupied by the highly viscous plastic material, and thus a very high impregnation quality can be achieved even when the fiber bundle is continuously guided through the impregnation cavity.

[0017] In this regard, the inventor has recognized that acoustic energy can be introduced into the highly viscous plastic material using an oscillator whose surface is in direct contact with the highly viscous molten plastic material, so that as a result, high-quality fiber bundles or rovings can be impregnated in a continuous process. The structural space required for this is very small, and thus the method according to the invention is particularly suitable for the 3D printing and continuous deposition of continuous fibers. By making the structural space smaller, in particular in the case of the end effector, the mass of the end effector to be moved is reduced, which makes it possible to increase the overall precision of the process.

[0018] The inventor has also recognized that, despite the high viscosity of the molten plastic material, acoustic energy can still be introduced into the plastic material using an oscillator in contact with the plastic material so that the fiber bundle is highly impregnated with the plastic material. This is surprising because the molten highly viscous plastic material requires much more time to recover its shape after mechanical deformation due to viscoelastic effects than a low-viscosity medium. However, high impregnation performance can be achieved.

[0019] According to an advantageous embodiment, the highly viscous plastic material is a thermoplastic material that is highly viscous at a predetermined process temperature at which the plastic material is melted and exists in the form of a melt, that is, it has a viscosity exceeding 8000 mPa·s.

[0020] According to a further advantageous embodiment, the vibration generator generates a vibration amplitude of 1 μm to 150 μm, preferably a maximum vibration amplitude of 40 μm, particularly preferably a maximum vibration amplitude of 35 μm, and / or a vibration frequency of 100 Hz to 100 kHz, preferably a vibration frequency of 15 kHz to 60 kHz, particularly preferably a vibration frequency of 19 kHz to 60 kHz. This enables the introduction of acoustic energy into the highly viscous plastic material, and this acoustic energy guarantees a very high impregnation performance despite the technical challenges of the highly viscous medium. In one specific embodiment, the vibration frequency is 45 kHz or less. In one specific embodiment, the vibration frequency is 19.2 kHz to 19.7 kHz.

[0021] According to a further advantageous embodiment, the oscillator induces real eigenmodes and / or complex eigenmodes of the structure of the impregnation cavity. However, despite the viscoelastic effects of the highly viscous plastic material, it has been found that sufficient acoustic power or acoustic energy can thus be introduced into the plastic material in order to achieve high impregnation performance. In this embodiment, at least a part of the surface of the oscillator is formed by a special vibration structure, preferably a modally vibrating structure, and the oscillator can induce real eigenmodes and / or complex eigenmodes of this structure of the impregnation cavity. One or more such structures are preferably completely covered by the plastic material of the impregnation cavity. Such a structure may be, for example, a mode vibration plate in the impregnation cavity. However, it is also conceivable that such a structure may be a tube having eigenmodes, through which the fiber bundle to be impregnated is guided. This makes it possible to significantly improve the impregnation performance even in the case of highly viscous plastic materials. In this regard, the tube itself may form the impregnation cavity or may be part of the impregnation cavity.

[0022] In that case, the resulting vibration maxima and minima of the above structure act as spatially distributed generators for coupling acoustic energy. According to a further advantageous embodiment, the surface of the oscillator in contact with the molten plastic material has been subjected to a microstructuring pretreatment, a roughening pretreatment, and / or a plasma pretreatment, or is provided such that the adhesion or wetting of the surface of the oscillator with the molten plastic material is improved. By means of such measures for pretreating the surface of the oscillator in contact with the plastic material, corresponding sound waves or pressure waves can be introduced into the molten plastic material in order to achieve the acoustic energy required for the impregnation of the fiber bundle, despite the viscoelastic effect of the highly viscous plastic material, and it has been found that it is possible to improve the adhesion of the surface to the molten plastic material or the wettability of the surface. As a result of increasing the adhesion of the surface of the oscillator in contact with the plastic, the generation of cavities that prevent the transmission of the required acoustic power between the surface of the oscillator and the molten plastic material is prevented, even at high frequencies and / or high amplitudes of the oscillator.

[0023] According to a further advantageous embodiment, the plastic material is physically modified in order to reduce the cohesive forces, and as a result it is possible to improve the wetting of the surface of the oscillator and the cohesive forces are reduced.

[0024] According to a further embodiment, the surface of the oscillator is in contact with the molten highly viscous plastic material, and the fiber bundle in the impregnation cavity is guided through the surface of the oscillator that at least partially surrounds the fiber bundle. Here, the fiber bundle is guided through the cavity of the oscillator, such as a needle hole or an arc, and in this region the oscillator emits acoustic energy into the highly viscous plastic material. In this regard, the fiber bundle can come into contact with the surface of the oscillator at specific points. The specific geometry here ensures that the material is prevented from flowing away or that the vibration energy or acoustic energy is coupled through the overpressure or underpressure zones in an improved manner.

[0025] In the method according to the invention for impregnating a fiber bundle, among other things, in order to improve the results, it can be provided that the fiber bundle is opened, for example, by suitable means upstream of the impregnation cavity or in the impregnation cavity, as allowed by the available structural space. However, in principle, when the method according to the invention is used, it is not necessary to effect the opening of the fibers of the fiber bundle.

[0026] According to one embodiment, it is provided that the molten plastic material is guided or flows through the impregnation cavity together with the fiber bundle. For this purpose, the impregnation cavity may have an inlet for the fiber bundle and an inlet for the molten plastic material, and in one preferred embodiment, the fiber bundle and the molten plastic material are guided into the impregnation cavity through exactly the same inlet. Accordingly, the impregnation cavity may have an outlet for the fiber bundle and an outlet for the molten plastic material, and in one preferred embodiment, the fiber bundle and the molten plastic material are guided out of the impregnation cavity through exactly the same outlet.

[0027] Thereby, it becomes possible to produce, for example, plastic-fiber semi-finished products (such as thermoplastic-fiber semi-finished products) by guiding the fiber bundle and the molten plastic material through, for example, a nozzle or an extruder in the form of the outlet.

[0028] According to one embodiment, it is provided that pressure is applied to the molten plastic material in the impregnation cavity or the molten plastic material is imprinted during the impregnation of the fiber bundle. In this case, the molten plastic material can be under a pressure greater than the ambient pressure. Thus, it is conceivable that the molten plastic material is under a melting pressure of 0.5 MPa to 10 MPa (5 bar to 100 bar) and, in a suitable case, even under a melting pressure up to 40 MPa (400 bar).

[0029] The pressure of the molten plastic material does not oscillate in the kHz range and is an additional pressure determined in particular by the geometry of the flow path and the conveying speed. This is because the introduction of sound into the molten plastic material (melt) also causes a change in pressure. However, this pressure oscillates in the kHz range according to the oscillator. The pressure meant here is independent of the introduction of sound and is introduced in addition to the introduction of sound. Thus, an additional pressure that is independent of the introduction of sound or the introduced acoustic energy is applied to the molten plastic material in the impregnation cavity. The molten plastic material is thus pressurized in addition to the introduction of acoustic energy.

[0030] Here, the molten plastic material can be under a pressure greater than the outlet pressure at the outlet or nozzle outlet, or the outlet pressure downstream of the outlet or nozzle outlet. This enables the nozzle to be arranged with only a very small gap relative to the pressure bed. In this case, since the melt cannot emerge at the free end, for example, there is a pressure of 10 MPa (100 bar) at the nozzle outlet, which is lower than the pressure in the impregnation cavity (e.g., 20 MPa (200 bar)).

[0031] Pushing the molten plastic material can be done, for example, in conjunction with the aforementioned embodiments in which the molten plastic material is guided from the impregnation cavity through the nozzle or extruder together with the fiber material. This makes it possible to achieve a pressure gradient between the inlet and the outlet of the molten plastic material.

[0032] Here, it is advantageous if the melt pressure of the plastic material is lower than the cavitation threshold. Here, it is also possible to increase the melt pressure to some extent, provided that acoustic energy sufficient to reach the cavitation threshold is introduced into the melted plastic material. Surprisingly, in combination with the introduction of acoustic energy into the plastic material by the vibrator, more significant cavitation effects occur and are dispersed in the pushed and melted plastic material, and it has been found that this cavitation effect results in an improved impregnation of the fiber material by the melted plastic material.

[0033] According to the present invention, the above object is further achieved by a method for generating a three-dimensional structure formed from two or more different materials, and the resulting mixed material is ejected by a 3D printing head of a 3D printing system. In this regard, the method includes the following steps, namely, - Supplying a highly viscous plastic material as a first material and a substantially infinite fiber bundle of a fiber material as a second material to a 3D printing facility, - Continuously supplying the two materials to an impregnation cavity of the 3D printing facility in order to impregnate the substantially infinite fiber bundle with the highly viscous melted plastic material, - Extruding the fiber bundle impregnated with the highly viscous plastic material by a 3D printing head, - During the generation of the three-dimensional structure, the substantially infinite fiber bundle is continuously impregnated with the highly viscous melted plastic material by the method as described above.

[0034] In this method, the highly viscous plastic material and the fiber material are supplied to the impregnation cavity, and the two materials are then combined to form a material mixture by impregnating the fiber material in the form of a fiber bundle or roving in the impregnation cavity with the highly viscous plastic material. Next, the fiber bundle thus impregnated is extruded from the 3D printing head to generate a three-dimensional structure.

[0035] Furthermore, the above object is also achieved by an apparatus for impregnating at least one fiber bundle, the apparatus having an impregnation cavity filled or fillable with a highly viscous plastic material, the impregnation cavity having an inlet and an outlet such that a fiber bundle for impregnation can be guided through the highly viscous molten plastic material of the impregnation cavity. Thus, the fiber bundle is introduced into the impregnation cavity by the inlet and guided out of the impregnation cavity by the outlet, and the fiber bundle is impregnated with the plastic material after being guided out of the outlet of the impregnation cavity. The apparatus further has a vibrator, the surface of the vibrator being in contact with or capable of contacting the highly viscous molten plastic material located in the impregnation cavity, the vibrator being designed to introduce acoustic energy into the highly viscous molten plastic material.

[0036] This apparatus is advantageously designed so as to be able to carry out the method for impregnating the fiber bundle described above. In particular, here it may be provided that the surface in contact with or capable of contacting the molten plastic material has a microstructuring treatment, a roughening treatment, and / or a plasma treatment in order to improve the adhesion between the surface of the vibrator and the molten plastic material.

[0037] Similarly, here it may also be provided that the surface of the vibrator has a cavity through which the fiber bundle to be impregnated can be guided when the fiber bundle is being guided through the highly viscous molten plastic material of the impregnation cavity.

[0038] According to a further advantageous embodiment, the cavity on the surface of the oscillator can form a tube through which the fiber bundle can be guided for impregnation with a highly viscous molten plastic material, and the tube can be provided to form a mode vibration structure and / or a vibration structure having a natural mode. By using the mode vibration structure or the vibration structure having a natural mode, it has been found that it is possible to significantly improve the impregnation result despite the high viscosity and viscoelastic effects of the medium. However, such a tube may also itself form an impregnation cavity, so that the roving is guided inside the tube and the highly viscous plastic material is present inside the tube.

[0039] The above object is further achieved by an installation for producing a three-dimensional structure, which installation has a print head having a first material supply for supplying a substantially infinite fiber bundle and at least one second material supply for supplying a plastic material, and in a process in which both the fiber bundle and the plastic material are continuously supplied to the print head, in order to impregnate the fiber bundle with the molten highly viscous plastic material, each material supply opens into a common impregnation cavity of the print head, and the plastic material can be supplied in a still solid state of the substance. Next, the supplied plastic material can be brought to its required process temperature by a temperature control device in the print head, and the plastic material can be made to exist in a molten state. It is of course also conceivable that the molten and temperature-controlled plastic material has already been supplied to the print head. The impregnated fiber bundle can then be extruded from the print head by the outlet of the print head.

[0040] According to the invention, the print head has a device for impregnating the fiber bundle, and provided for this purpose is an oscillator, the surface of which can contact or be brought into contact with the highly viscous molten plastic material located in the impregnation cavity, and the oscillator is designed to introduce acoustic energy into the highly viscous molten plastic material.

[0041] The present invention will be described by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0042]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0043] FIG. 1 shows a highly simplified schematic diagram of an apparatus 10 for impregnating a fiber bundle 11 guided through an impregnation cavity 12. Here, the impregnation cavity 12 is filled with a highly viscous molten plastic material 13 into which the fiber bundle 11 is to be impregnated.

[0044] Furthermore, the apparatus 10 has a vibration generator 14, and the surface 15 of the vibration generator 14 contacts the molten highly viscous plastic material 13. The vibration generator 14 shown in FIG. 1 is a longitudinal vibrator that performs a stroke movement in the form of an amplitude s in order to introduce acoustic energy into the highly viscous plastic material 13 at a predetermined frequency f. In this regard, in the exemplary embodiment in FIG. 1, the direction of the stroke movement is essentially perpendicular to the fiber bundle 11.

[0045] Due to the fact that the surface 15 of the vibration generator 14 directly contacts the molten highly viscous plastic material 13, the vibration generated by the vibration generator 14 can be introduced into the plastic material 13 in the form of acoustic energy in order to improve the impregnation performance of the fiber bundle 11.

[0046] Here, in order to improve the adhesion between the surface 15 of the vibrator 14 and the molten highly viscous plastic material 13, it can be provided that the surface 15 of the vibrator 13 has been subjected to a micro-structuring pretreatment, a roughening pretreatment, and / or a plasma pretreatment. This has the effect that voids that would otherwise impede or even completely prevent the coupling of the vibrations of the vibrator 14 to the plastic material 13 do not occur between the surface 15 of the vibrator 14 and the plastic material 13 during vibration.

[0047] The right side of FIG. 1 shows various possible cross-sectional shapes of the vibrator 14 intended to couple the vibrations generated by the vibrator 14 to the highly viscous plastic material as the surface 15.

[0048] FIG. 2 schematically shows the device 10, in which case the vibrator 14 has a recess that partially or completely surrounds a fiber bundle that is guided through an impregnation cavity in full contact with the highly viscous plastic material in the region of its surface 15 where the vibrator contacts the highly viscous plastic material. Thus, the roving 11 is guided through a kind of "hole" in the longitudinal vibrator having a specific contour geometry, and in the process, the fibers of the roving can contact the surface of the longitudinal vibrator 14 at specific points. The specific geometry prevents the material from being blocked or ensures that the vibration energy is coupled through zones of overpressure and negative pressure in an improved manner.

[0049] FIG. 3 schematically shows a further embodiment of the device 10, in which case the counterpart or counterpart element 16 is positioned opposite the vibrator 14 such that the fiber bundle 11 is guided between the surface 15 of the vibrator 14 and the counterpart 16.

[0050] The counterpart 16 may be, for example, a reflective element, which is arranged in the impregnation cavity 12 and reflects the sound waves coupled by the vibrator 14, and as a result, the influence or action of the sound waves on the impregnation process can be improved.

[0051] Also, it is of course conceivable that the relative object 16 is also a vibrator capable of actively introducing sound waves into the highly viscous plastic material, and the frequencies and amplitudes of the two vibrators 14 and 16 can be adapted so as to maximize the effect of impregnating the roving.

[0052] FIG. 4 shows a very simplified schematic view of an embodiment, in which case slightly opened roving is drawn through the highly viscous plastic material, and located in the impregnation cavity 12 is a mode vibration structure 17 in the form of a vibrator, intended to introduce the corresponding acoustic energy into the highly viscous plastic material. Here, the resulting vibration maxima and minima couple the vibration energy to the highly viscous plastic material in a spatially distributed manner.

[0053] FIG. 5 shows a further exemplary embodiment of a mode vibration structure 18 having eigenmodes, the mode vibration structure 18 being designed to completely surround the roving 11. In this case, the surface of the vibrator is formed by the mode vibration structures 17 and 18, and the vibrator is designed such that the actual eigenmodes and / or complex eigenmodes of these structures 17 and 18 can be induced. Here, these mode vibration structures 17 and 18 are located within the impregnation cavity 12 and can preferably be completely surrounded by the highly viscous plastic material 12. This makes it possible to very effectively introduce the acoustic energy required to improve the impregnation performance into the plastic material. In addition, this type of embodiment requires only a very small amount of structural space and is thus particularly suitable for the production method.

[0054] However, it is also conceivable that the mode vibration structure 18 in the form of the tube shown in FIG. 5 forms the actual impregnation cavity, and thus the tube 18 is the impregnation cavity. For this purpose, the tube 18 has an inlet 19a and an outlet 19b, and as a result, the fiber material 11 is guided into the interior of the tube through the inlet 19a and is also guided out through the outlet 19b. Further, molten plastic material is located inside the tube 18, and acoustic energy is introduced into the molten plastic material by the tube 18 in the form of a mode vibration structure having a natural mode. In this exemplary embodiment, the plastic material is not intentionally located outside the tube, and the plastic material exists only inside the tube together with the fiber material.

[0055] FIG. 6 shows a highly simplified view of the apparatus 10 in a further embodiment. The apparatus 10 comprises an impregnation cavity 12, through which a fiber bundle 11 and a highly viscous plastic material 13 are guided. Further, a vibration generator 14 in the form of a sonotrode projects into the impregnation cavity 12 such that the vibration generator 14 contacts the molten plastic material 13 without contacting the fiber bundle 11 within the impregnation cavity. Thus, acoustic energy can be introduced into the molten plastic material 13 using the vibration generator 14.

[0056] Both the fiber bundle 11 (not impregnated, not fully impregnated, or not sufficiently impregnated) and the molten plastic material 13 are introduced into the apparatus 10 via the inlet 19a, and as a result, the fiber bundle 11 and the molten plastic material 13 can be introduced into the impregnation cavity 12. The fiber bundle 11 impregnated with the plastic material 13 is then guided out of the apparatus 10 through the outlet 19b.

[0057] In this regard, the outlet 19b is designed in the form of an extruder or nozzle for shaping and integrating the plastic material. By shaping the outlet 19b in the form of a nozzle or extruder in contrast to the inlet, a pressure gradient can occur in the plastic material 13 between the inlet 19a and the outlet 19b. Here, the melt pressure may be 1.5 MPa to 10 MPa (15 bar to 100 bar), and may be 40 MPa (400 bar) in appropriate cases.

[0058] In this regard, the inlet 19a is designed for a pressure-tight supply of the fiber bundle 11 and the melted plastic material 13. The outlet 19b can be designed to be pressure-tight here, especially with respect to the melted plastic material.

[0059] In this regard, the vibrator 14 is likewise arranged on the device 10 in a pressure-tight manner with respect to the impregnation cavity 12. Pushing the melted plastic material 13 with pressure or forming a pressure gradient, in combination with the introduction of acoustic energy by the vibrator 14, causes cavitation to occur and disperse in the melted plastic material 13, and this cavitation has the effect of significantly improving the impregnation result. The microjets and / or shock waves (cavitation effect) generated when the cavitation disperses have been found to improve the impregnation, especially when using highly viscous plastic materials.

[0060] The guide element 20 is located between the inlet 19a and the upstream of the outlet 19b to guide the fiber material 11 in the correct position through the impregnation cavity 12. In this case, the sonotrode 14 or the vibrator is arranged between the guide elements 20.

[0061] Here, the vibrator 14 is connected to the device 10 via a pressure-tight attachment 23. The temperature and pressure can be continuously monitored by sensors 22 in the region of the impregnation cavity 12.

[0062] Finally, the impregnated fiber roving 21 is guided out at the outlet 19b. The present invention includes the following aspects. [1] A method for impregnating at least one fiber bundle (11) with a highly viscous plastic material (13), the method comprising the following steps, namely, providing at least one fiber bundle (11) to be impregnated, formed from a plurality of endless fibers, and a plastic material (13) melted at a predetermined process temperature and having high viscosity; impregnating the fiber bundle (11) with the plastic material (13) by continuously guiding the fiber bundle (11) to be impregnated through an impregnation cavity (12) filled with the melted plastic material (13). A method, characterized in that, during the impregnation of the fiber bundle (11), the melted plastic material (13) located in the impregnation cavity (12) contacts the surface (15) of at least one vibrator (14), and acoustic energy is introduced into the melted highly viscous plastic material (13) of the impregnation cavity (12) by the vibrator (14). [2] The method according to 1, characterized in that the highly viscous plastic material (13) is a thermoplastic material. [3] The method according to 1 or 2, characterized in that the vibrator (14) generates a vibration amplitude of 1 μm to 150 μm, preferably a maximum vibration amplitude of 40 μm, particularly preferably a maximum vibration amplitude of 35 μm, and / or the vibrator (14) generates a vibration frequency of 100 Hz to 100 kHz, preferably a vibration frequency of 15 kHz to 60 kHz, particularly preferably a vibration frequency of 20 kHz to 60 kHz. [4] The method according to any one of 1 to 3, characterized in that the vibrator (14) induces the real eigenmode and / or complex eigenmode of the structure (17, 18) of the impregnation cavity (12). [5] The method according to any one of 1 to 4, characterized in that the surface (15) of the vibrator (14) in contact with the melted plastic material (13) for introducing the acoustic energy has undergone a microstructuring pretreatment, a roughening pretreatment, and / or a plasma pretreatment, or is provided so as to improve the adhesion or wetting of the surface (15) of the vibrator (14) with the melted plastic material (13). [6] The method according to any one of 1 to 5, characterized in that the plastic material (13) is physically modified to reduce the cohesive force. [7] The method according to any one of 1 to 6, characterized in that the surface (15) of the vibration generator (14) contacts the melted highly viscous plastic material (13), and the fiber bundle (11) in the impregnation cavity (12) is guided through the surface (15) of the vibration generator (14) that at least partially surrounds the fiber bundle (11). [8] The method according to any one of 1 to 7, characterized in that the melted plastic material (13) is guided or flows through the impregnation cavity (12) together with the fiber bundle (11). [9] The method according to any one of 1 to 8, characterized in that pressure is applied to the melted plastic material (13) in the impregnation cavity (12) during the impregnation of the fiber bundle (11).

[10] A method for generating a three-dimensional structure formed from two or more different materials by a three-dimensional printing head of three-dimensional printing equipment, the method comprising the following steps, namely, Supplying a highly viscous plastic material (13) as a first material and a substantially infinite fiber bundle (11) of a fiber material as a second material to the three-dimensional printing equipment, A step in which the two materials are continuously supplied to an impregnation cavity (12) of the three-dimensional printing equipment in order to impregnate the substantially infinite fiber bundle (11) with the highly viscous melted plastic material (13), A method comprising the step of extruding the fiber bundle (11) impregnated with the highly viscous plastic material (13) by the three-dimensional printing head. A method, characterized in that during the generation of the three-dimensional structure, the substantially infinite fiber bundle (11) is continuously impregnated with the highly viscous melted plastic material (13) by the method according to any one of 1 to 9.

[11] An apparatus (10) for impregnating at least one fiber bundle (11) formed from a plurality of endless fibers with a plastic material (13) that is melted at a predetermined process temperature and has a high viscosity, wherein the apparatus (10) has an impregnation cavity (12) that is filled or can be filled with the high-viscosity plastic material (13), and the impregnation cavity (12) has an inlet and an outlet such that a fiber bundle (11) for impregnation can be guided through the high-viscosity molten plastic material (13) of the impregnation cavity. The apparatus (10) also has a vibrator (14), and a surface (15) of the vibrator (14) is in contact with or can be brought into contact with the high-viscosity molten plastic material (13) located in the impregnation cavity (12), and the vibrator is designed to introduce sound energy into the high-viscosity molten plastic material (13). The apparatus (10) is characterized by this.

[12] The apparatus (10) according to 11, characterized in that the vibrator (14) is designed to produce a vibration amplitude of 1 μm to 150 μm, preferably a maximum vibration amplitude of 40 μm, particularly preferably a maximum vibration amplitude of 35 μm, and / or a vibration frequency of 100 Hz to 100 kHz, preferably a vibration frequency of 15 kHz to 60 kHz, particularly preferably a vibration frequency of 20 kHz to 60 kHz.

[13] The apparatus (10) according to 11 or 12, characterized in that the vibrator (14) is configured to generate vibrations such that the real and / or complex eigenmodes of the structure (17, 18) of the impregnation cavity (12) are induced.

[14] The apparatus (10) according to any one of 11 to 13, characterized in that the surface (15) that is in contact with or can be brought into contact with the molten plastic material has a microstructuring treatment, a roughening treatment, and / or a plasma treatment in order to improve the adhesion and / or wetting of the surface (15) of the vibrator (14) with the molten plastic material.

[15] The apparatus (10) according to any one of 11 to 14, characterized in that when the fiber bundle (11) is guided through the highly viscous molten plastic material (13) in the impregnation cavity (12), the surface (15) of the vibration generator (14) has a cavity through which the fiber bundle (11) to be impregnated can be guided.

[16] The apparatus (10) according to 15, characterized in that the cavity on the surface (15) of the vibration generator (14) forms a tube through which the fiber bundle (11) can be guided for impregnation with the highly viscous molten plastic material (13), and the tube has a vibration structure having a mode vibration structure and / or a natural mode.

[17] Equipment for producing a three-dimensional structure formed from two or more different materials, the equipment having a three-dimensional printing head having a first material supply for supplying a substantially infinite fiber bundle (11) of fiber material and at least one second material supply for supplying a plastic material (13) melted at a predetermined process temperature and having a high viscosity, the first material supply and the second material supply opening into an impregnation cavity (12) of the three-dimensional printing head for impregnating the fiber bundle (11) with the molten high-viscosity plastic material (13), the impregnation cavity (12) being connected in communication with an outlet of the three-dimensional printing head, the outlet being configured to extrude the impregnated fiber bundle (11) for producing the three-dimensional structure, wherein the three-dimensional printing head comprises the apparatus (10) according to any one of 11 to 16.

Description of Symbols

[0063] 10 Device, 11 Fiber Bundle / Roving, 12 Impregnation Cavity, 13 Highly Viscous Plastic Material, 14 Vibration Generator, 15 Surface of the Vibration Generator, 16 Opposite / Opposite Element, 17 Mode Vibration Plate Structure, 18 Mode Vibration Tube with Natural Mode, 19a Inlet, 19b Outlet, 20 Guide Element, 21 Impregnated Fiber Roving, 22 Sensor, 23 Mounting Part with Excellent Pressure Resistance

Claims

**Claim 1** A method for impregnating at least one fiber bundle (11) with a plastic material (13), said method comprising the following steps, namely: providing at least one fiber bundle (11) to be impregnated, formed from a plurality of endless fibers, and a plastic material (13) melted at a predetermined process temperature; impregnating the fiber bundle (11) with the plastic material (13) by continuously guiding the fiber bundle (11) to be impregnated through an impregnation cavity (12) filled with the melted plastic material (13); during impregnation of the fiber bundle (11), the melted plastic material (13) located in the impregnation cavity (12) is characterized in that it contacts the surface (15) of at least one vibrator (14), and acoustic energy is introduced into the melted plastic material (13) of the impregnation cavity (12) by the vibrator (14); characterized in that the vibrator (14) induces the real and / or complex eigenmodes of the structure (17, 18) of the impregnation cavity (12); characterized in that the surface (15) of the vibrator (14) contacts the melted plastic material (13), and the fiber bundle (11) in the impregnation cavity (12) is guided through the surface (15) of the vibrator (14) that at least partially surrounds the fiber bundle (11); A method. **Claim 2** The method according to claim 1, characterized in that the plastic material (13) is a thermoplastic material. **Claim 3** The method according to claim 1 or 2, characterized in that the vibrator (14) produces a vibration amplitude of 1 μm to 150 μm, and / or the vibrator (14) produces a vibration frequency of 100 Hz to 100 kHz. **Claim 4** The method according to claim 3, characterized in that the vibrator (14) produces a maximum vibration amplitude of 40 μm, and / or the vibrator (14) produces a vibration frequency of 15 kHz to 60 kHz. **Claim 5** In order to introduce the acoustic energy, the surface (15) of the vibrator (14) that contacts the molten plastic material (13) has undergone a microstructuring pretreatment, a roughening pretreatment, and / or a plasma pretreatment so as to improve the adhesion and / or wetting of the surface (15) of the vibrator (14) with the molten plastic material (13). The method according to any one of claims 1 to 4, characterized in that.

6. The method according to any one of claims 1 to 5, characterized in that the molten plastic material (13) is guided or flows through the impregnation cavity (12) together with the fiber bundle (11).

7. The method according to any one of claims 1 to 6, characterized in that pressure is applied to the molten plastic material (13) in the impregnation cavity (12) during the impregnation of the fiber bundle (11).

8. A method for generating a three-dimensional structure formed from two or more different materials by a three-dimensional printing head of three-dimensional printing equipment, the method comprising the following steps, namely, Supplying a plastic material (13) as a first material and a substantially infinite fiber bundle (11) of a fiber material as a second material to the three-dimensional printing equipment, A step in which the two materials are continuously supplied to an impregnation cavity (12) of the three-dimensional printing equipment in order to impregnate the substantially infinite fiber bundle (11) with the molten plastic material (13), A method comprising the step of extruding the fiber bundle (11) impregnated with the plastic material (13) by the three-dimensional printing head. During the generation of the three-dimensional structure, the substantially infinite fiber bundle (11) is continuously impregnated with the molten plastic material (13) by the method according to any one of claims 1 to 7. A method, characterized in that.

9. An apparatus (10) for impregnating at least one fiber bundle (11) formed from a plurality of endless fibers with a plastic material (13) melted at a predetermined process temperature, said apparatus (10) having an impregnation cavity (12) filled or fillable with said plastic material (13), said impregnation cavity (12) having an inlet and an outlet such that a fiber bundle (11) for impregnation can be guided through said melted plastic material (13) of said impregnation cavity, said apparatus (10) also having a vibrator (14), the surface (15) of said vibrator (14) being in contact with or capable of contacting said melted plastic material (13) located in said impregnation cavity (12), said vibrator being designed to introduce acoustic energy into said melted plastic material (13). Characterized in that said vibrator (14) is configured to generate vibrations such that the real and / or complex eigenmodes of the structure (17, 18) of said impregnation cavity (12) are induced. Characterized in that the surface (15) of said vibrator (14) has a cavity through which the fiber bundle (11) to be impregnated can be guided when the fiber bundle (11) is being guided through the melted plastic material (13) of said impregnation cavity (12). Apparatus (10).

10. The apparatus (10) according to claim 9, characterized in that said vibrator (14) is designed to produce a vibration amplitude of 1 μm to 150 μm and / or a vibration frequency of 100 Hz to 100 kHz.

11. The apparatus (10) according to claim 10, characterized in that said vibrator (14) is designed to produce a vibration amplitude of at most 40 μm and / or a vibration frequency of 15 kHz to 60 kHz.

12. In order to introduce the acoustic energy, the surface (15) that can contact or be brought into contact with the molten plastic material is subjected to a microstructuring treatment, a roughening treatment, and / or a plasma treatment in order to improve the adhesion and / or wetting of the surface (15) of the vibration generator (14) with the molten plastic material. The apparatus (10) according to any one of claims 9 to 11, characterized in that it has such treatments.

13. The cavity on the surface (15) of the vibration generator (14) forms a tube through which the fiber bundle (11) can be guided for impregnation with the molten plastic material (13), and the tube has a vibration structure having a mode vibration structure and / or a natural mode. The apparatus (10) according to claim 9, characterized in that it has such a structure.

14. Equipment for generating a three-dimensional structure formed from two or more different materials, the equipment having a three-dimensional printing head having a first material supply section for supplying a substantially infinite fiber bundle (11) of a fiber material and at least one second material supply section for supplying a plastic material (13) melted at a predetermined process temperature. The first material supply section and the second material supply section open into an impregnation cavity (12) of the three-dimensional printing head for impregnating the fiber bundle (11) with the molten plastic material (13). The impregnation cavity (12) is connected in communication with an outlet of the three-dimensional printing head, and the outlet is configured to extrude the impregnated fiber bundle (11) for generating the three-dimensional structure. In the equipment, the three-dimensional printing head is provided with the apparatus (10) according to any one of claims 9 to 13. The equipment is characterized in that it has such a configuration.

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