Method and apparatus for thermally joining thermoplastic fiber composite components, and cover for a pressurization device suitable for this purpose

Abstract

A method for thermally joining thermoplastic fiber composite components, including jointly covering thermoplastic fiber composite components to be joined, at least in the region of a joining zone, with a pressurization arrangement, which is flexible, at least in some section or sections, and extensive pressurization of thermoplastic fiber composite components to be joined by the pressurization arrangement, with the result that the fiber composite components are pressed against one another, at least in the joining zone. The fiber composite components are welded in the joining zone during pressurization. The pressurization is maintained by the pressurization arrangement until the joining zone solidifies. A cover is also disclosed, in particular a mold or diaphragm, for a pressurization device for thermally joining thermoplastic fiber composite components, and an apparatus for thermally joining thermoplastic fiber composite components.

Claims

1. A method for thermally joining thermoplastic fiber composite components, comprising: jointly covering thermoplastic fiber composite components to be joined, at least in a region of a joining zone, with a pressurization arrangement, which is flexible, at least in some section or sections; extensive pressurization of thermoplastic fiber composite components to be joined by the pressurization arrangement, with a result that the fiber composite components are pressed against one another, at least in the joining zone; welding the fiber composite components in the joining zone during pressurization; and maintaining the pressurization by the pressurization arrangement until the joining zone solidifies; wherein the pressurization arrangement contains electric contacts, and the fiber composite components are welded by resistance welding via the electric contacts; wherein the electric contacts are arranged along the joining zone and welding is performed continuously or in sections along the joining zone by local application of a welding current to the electrical contacts; wherein an electric current flow is generated through mating parts of the fiber composite components to be joined in a thickness direction of the fiber composite components; wherein the pressurization arrangement comprises a vacuum arrangement and pressurization comprises applying a vacuum; and wherein the vacuum arrangement has a flexible vacuum diaphragm, which covers a top side and/or a bottom side of the fiber composite components to be joined, wherein the joint covering, by the vacuum arrangement, of the fiber composite components to be joined comprises applying at least one electrically conductive element as an electric contact in the joining zone, to which electrically conductive element the vacuum diaphragm is connected in an airtight manner, wherein a plurality of electrically conductive elements is provided as contact sections, which electrically conductive elements are each separated electrically from one another and which electrically conductive elements are connected in an airtight manner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure herein is explained in greater detail below by the illustrative, example embodiments indicated in the schematic figures. Here:

(2) FIG. 1 shows a cross-sectional view of an apparatus for thermally joining thermoplastic fiber composite components according to one embodiment;

(3) FIG. 2 shows a longitudinal section through the apparatus shown in FIG. 1;

(4) FIG. 3 shows a longitudinal section through an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(5) FIG. 4 shows a plan view of the apparatus shown in FIG. 3;

(6) FIG. 5 shows a cross-sectional view of an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(7) FIG. 6 shows a longitudinal section through the apparatus shown in FIG. 5;

(8) FIG. 7 shows a plan view of the apparatus shown in FIGS. 5 and 6;

(9) FIG. 8 shows a cross-sectional view of an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(10) FIG. 9 shows a longitudinal section through an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(11) FIG. 10 shows a longitudinal section through a modified apparatus for thermally joining thermoplastic fiber composite components;

(12) FIG. 11 shows a longitudinal section through another modified apparatus for thermally joining thermoplastic fiber composite components;

(13) FIG. 12 shows a longitudinal section through an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(14) FIG. 13 shows a longitudinal section through a modified apparatus for thermally joining thermoplastic fiber composite components;

(15) FIG. 14 shows a cross-sectional view of an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(16) FIG. 15 shows a cross-sectional view of an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(17) FIG. 16 shows a segment of a cross-sectional view of a modification of the embodiment shown in FIG. 15;

(18) FIG. 17 shows a longitudinal section through the apparatus shown in FIG. 15;

(19) FIG. 18 shows a plan view of the apparatus shown in FIG. 17;

(20) FIG. 19 shows a cross-sectional view of an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(21) FIG. 20 shows a plan view of the apparatus shown in FIG. 19;

(22) FIG. 21 shows a longitudinal section through an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment;

(23) FIG. 22 shows a longitudinal section through a modified apparatus for thermally joining thermoplastic fiber composite components;

(24) FIG. 23 shows a longitudinal section through another modified apparatus for thermally joining thermoplastic fiber composite components;

(25) FIG. 24 shows a cross-sectional view of an apparatus shown in FIG. 22 or FIG. 23;

(26) FIG. 25 shows a cross-sectional view of another modified apparatus for thermally joining thermoplastic fiber composite components; and

(27) FIG. 26 shows a cross-sectional view of an apparatus for thermally joining thermoplastic fiber composite components according to another embodiment.

(28) The attached figures are intended to impart further understanding of the embodiments of the disclosure herein. They illustrate embodiments and, together with the description, serve to explain principles and concepts of the disclosure herein. Other embodiments and many of the stated advantages will become apparent with reference to the drawings. The elements of the drawings are not necessarily shown to scale relative to one another.

(29) In the figures of the drawing, identical, functionally identical and identically acting elements, features and components are—unless stated otherwise—each provided with the same reference signs.

DETAILED DESCRIPTION

(30) FIG. 1 shows a cross-sectional view of an apparatus 20 for thermally joining thermoplastic fiber composite components 1, 2 according to one embodiment.

(31) The apparatus 20 has a pressurization arrangement 4 and a welding device 31.

(32) Here, the pressurization arrangement 4 is designed as a vacuum arrangement 8. This has a vacuum diaphragm 9, a suction nozzle 18, which is designed for connection to a vacuum source, e.g. a vacuum pump, and sealing elements 19 for sealing the vacuum diaphragm 9 with respect to the environment.

(33) Thermoplastic fiber composite components 1 and 2 to be joined are arranged with an overlapping joint. Furthermore, electric contacts 5, which are connected airtightly to the vacuum diaphragm 9, are provided in the region of a joining zone 3 of the fiber composite components to be welded, the joining zone being arranged in the region of overlap 38.

(34) By way of example, airtight adhesive tapes 36 are provided here for the airtight connection of the elements of the vacuum arrangement 8. For the sake of clarity, these tapes are depicted purely schematically with a certain clearance but, of course, they actually rest directly on the elements to be connected, in this case the contacts 5 and the vacuum diaphragm 9.

(35) In this embodiment, the joint coverage of the fiber composite components 1, 2 to be joined and the vacuum arrangement 8 comprises applying at least one electrically conductive element 10 as an electric contact 5 in the joining zone 3. To obtain a vacuum arrangement 8, the electrically conductive element 10 is connected airtightly to the vacuum diaphragm 9. The vacuum diaphragm furthermore has a suction nozzle 18, coupled thereto, for connection to a vacuum pump. If a vacuum is applied via the suction nozzle 18, as symbolized by the arrow depicted here, atmospheric pressure acts on the joining zone 3 and thus compresses the fiber composite components 1, 2 in the region of overlap 38 in which the joining zone 3 is situated.

(36) Here, the pressurization arrangement 4 is provided on both sides and fully covers the joining zone 3 both on the top side and on the bottom side. It furthermore extends beyond the region of overlap of the fiber composite components 1, 2. In the embodiment illustrated, by way of example, the pressurization arrangement is in two parts. It is thus sealed off with respect to the two fiber composite components 1, 2 on both sides, in each case individually by the sealing elements 19.

(37) In other embodiments, it would also be conceivable to provide an inflexible mold on the bottom side and to provide the vacuum arrangement 8 only on the top side.

(38) Here, the mounting device 31 is designed with two oppositely arranged welding electrodes, which can be coupled to a welding source. These are welding electrodes that can be moved on the contacts 5 along the joining zone 3. The welding electrodes can be moved independently of the vacuum arrangement 8. The pressure applied by the vacuum arrangement therefore remains constant during and after welding. The pressure is thus maintained until thermoplastic matrix of the fiber composite components 1, 2 solidifies. In this way, welding defects due to air or gas inclusions, which can lead to the formation of pores, are counteracted.

(39) Adjoining the overlap, electrically non-conductive auxiliary inserts 37 are applied on both sides of the joint. These are used to avoid creases in the vacuum diaphragm and thus facilitate airtight connection. The auxiliary inserts 37 can be formed from a material with a sufficiently high melting temperature which is non-conductive and preferably does not stick to thermoplastic matrix, ensuring that they do not melt too during the welding process. The same also applies to the materials of the pressurization arrangement 4 or of the vacuum arrangement 8. As an alternative or in addition, the auxiliary inserts 37 can also be wrapped in non-conductive or insulating film or provided with an insulating coating.

(40) An apparatus 20 of this kind is suitable for a method according to the disclosure herein for thermally joining thermoplastic fiber composite components 1, 2. For this purpose, thermoplastic fiber composite components 1, 2 to be joined are jointly covered with the pressurization arrangement 4 at least in the region of the joining zone 3 in a first step. A further step comprises the extensive pressurization of thermoplastic fiber composite components 1, 2 to be joined by the pressurization arrangement 4, with the result that the fiber composite components 1, 2 are pressed against one another, at least in the joining zone 3. The welding of the fiber composite components 1, 2 in the joining zone 3 during pressurization follows in a further step. The pressurization is then maintained at least until the joining zone 3 solidifies.

(41) To improve the contact between the electric contacts 5 and the fiber composite components 1, 2, the covering of thermoplastic fiber composite components 1, 2 to be joined can comprise the application of a contact paste between the contacts 5 and the fiber composite components 1, 2.

(42) If the pressurization arrangement 4 is provided as a vacuum arrangement 8, as here, the pressurization comprises the application of a vacuum.

(43) FIG. 2 shows a longitudinal section through the apparatus 20 shown in FIG. 1.

(44) Here, the fiber composite components 1, 2 are accordingly shown as continuous in the region of overlap 38, which defines the length to be connected in the joining zone 3 and over which the contacts 5 also extend in a continuous manner. The welding electrodes of the welding device 31 are designed to be longitudinally movable along the contacts 5, as symbolized by the arrows depicted. In this way, the welding along the joining zone 3 is performed continuously by local application of a welding current to the contacts 5, wherein the welding electrodes are moved forwards in parallel along the joining zone 3.

(45) The electrodes are accordingly formed with a surface which slides well on the contacts. In further embodiments, the electrodes can also alternatively or additionally have rollers or brushes designed for moving or sliding contact, for example.

(46) Since the contacts 5 are connected in an airtight manner to the vacuum diaphragm 9, the vacuum remains constant during the welding operation. The vacuum continues to be applied even after the welding process, until the joining zone 3 has solidified at least predominantly. This can be the case, for example, as soon as the joining zone has cooled to below the glass transition temperature of thermoplastic matrix material.

(47) FIG. 3 shows a longitudinal section through an apparatus 21 for thermally joining thermoplastic fiber composite components according to another embodiment.

(48) This embodiment is distinguished by division of the electric contacts 5 into a multiplicity of mutually isolated contact sections 5a, 5b, 5c, . . . , 5n on the top side and 5a′, 5b′, 5c′, . . . , 5n′ on the bottom side. The actual number of mutually isolated contact sections is not limited here, as is indicated by the three dots between 5c and 5n and between 5c′ and 5n′. In this regard, the illustration should be taken as purely illustrative. In the embodiment illustrated, the airtight electrically insulated connection of the contact sections is implemented by airtight adhesive tapes 36, by way of example.

(49) To weld the fiber composite components 1, 2, an apparatus 21 of this type is used to apply a welding current simultaneously to two respectively opposite contact sections 5a, 5a′, 5b, 5b′, 5c, 5c′ or 5n, 5n′ on both sides of the joining zone 3. The welding electrodes of the welding device 31 move forwards substantially in the same way in parallel along the joining zone 3 as described with reference to FIG. 2, and therefore the contact sections are traversed in succession. Here, the current flow of the welding current is always provided in the thickness direction of the fiber composite components and, by virtue of the insulated connection of the contact sections, also cannot be distributed laterally or via other sections of the contacts. This ensures that the welding of the fiber composite components 1, 2 is controlled by a current flow in the thickness direction D of the fiber composite components 1, 2.

(50) FIG. 4 shows a plan view of the apparatus shown in FIG. 3.

(51) In this figure, it can be seen that the fiber composite components 1, 2 are fully covered by the pressurization arrangement 4 in the region of overlap 38. The vacuum arrangement 8 thus produces the vacuum uniformly in the entire region of overlap 38, in particular over the entire joining zone 3.

(52) As can likewise be seen, the contact sections 5a, 5b, 5c, . . . , 5n, which are connected to one another in an airtight and electrically insulated manner, are distributed over the entire width of the joining zone, ensuring that the fiber composite components 1, 2 are welded over their entire width by the depicted longitudinal movement of the welding electrodes. Here, the welding electrodes of the welding device 31 contact the individual contact sections in succession, and therefore the welding of the joining zone is performed in segments.

(53) The seal comprising the sealing elements 19 is provided in such a way as to extend around the joining zone. The pressurization applied by the vacuum arrangement 8 is thus the same in all segments of the joining zone.

(54) FIG. 5 shows a cross-sectional view of an apparatus 22 for thermally joining thermoplastic fiber composite components 1, 2 according to another embodiment.

(55) In this embodiment, a cover in the form of a directionally conductive diaphragm 11 is provided instead of a conventional vacuum diaphragm 9 of the pressurization device. The diaphragm 11 is of substantially flexible and airtight design and differs significantly in its direction-dependent electric conductivity normal to the extent of the main surface thereof. In the directions 15 of extent of the main surface thereof, in contrast, the diaphragm 11 is of electrically insulating design. The diaphragm 11 can therefore be constructed in a substantially simpler way than the vacuum diaphragm 9 since there is no need for interruptions or additional electrically conductive elements.

(56) In this way, it is possible to carry out welding here without additional insulating measures in the joining zone 3.

(57) FIG. 6 shows a longitudinal section through the apparatus 22 shown in FIG. 5.

(58) Here too, welding is performed by a longitudinal movement (symbolized by the arrows) of the welding electrodes of the welding device 31 along the joining zone 3. As a particular advantage, continuous welding is thus made possible by the movement.

(59) By virtue of the direction-dependent electric conductivity of the cover, there is no longer any division into segments in which the fiber composite components 1, 2 can be welded in succession by an apparatus 21 shown in FIGS. 3 and 4. On the contrary, it is always possible, with the apparatus 22 illustrated here, to perform local welding precisely at the location of the joining zone 3 at which a welding electrode of the welding device 31 is situated at a particular time.

(60) Thus, a weld pool of the welding process moves continuously forwards with the welding electrodes along the joining zone. As a result, welding takes place very uniformly and therefore a homogeneous weld seam is achieved.

(61) FIG. 7 shows a plan view of the apparatus shown in FIGS. 5 and 6.

(62) As can be seen, the diaphragm 11 of the cover covers the entire region of overlap 38 here. In particular, there is no need for an interruption in the diaphragm 11.

(63) To provide the airtight and flexible design which is electrically conductive only normally to the main direction of extent, the diaphragm 11 can be a multi-material mix consisting of or comprising conductive and non-conductive materials, wherein the conductive materials connect the two surfaces of the diaphragm 11 electrically to one another and are at least predominantly spaced apart from one another. For example, the diaphragm 11 contains a plastic film with embedded metal particles that span the thickness of the film or an airtight synthetic fiber textile with metal threads introduced therein and passing through the thickness of the textile.

(64) FIG. 8 shows a cross-sectional view of an apparatus 23 for thermally joining thermoplastic fiber composite components according to another embodiment.

(65) In this embodiment, although a diaphragm 11 is provided as a cover, the diaphragm 11 is constructed from two layers 12, 13, in contrast to FIGS. 5 through 7. A first, outer layer 13 is of airtight and flexible design and is designed to be electrically conductive only normally to the main direction of extent. It is, in particular, an airtight or approximately airtight medium, e.g. a film or a textile. The cover has a significant electric conductivity only in the thickness direction. In directions parallel to its surface, however, it does not have any significant electric conductivity.

(66) A second layer 12 is designed to be permeable to air and impermeable to thermoplastic polymer melt. This is, in particular, a semi-permeable medium which is permeable to air but at least virtually impermeable to the melted or liquefied matrix material in a weld pool of the mating parts. Furthermore, the second layer 12, like the first layer 13, has a significant electric conductivity only in the thickness direction. In directions parallel to the surface, however, it does not have any significant electric conductivity.

(67) In the embodiment illustrated, the first layer 13 and the second layer 12 are each sealed off separately with respect to the fiber composite components 1, 2 by sealing elements 19. Here too, the cover is designed as a vacuum arrangement 8. In the event of pressurization by the application of a vacuum to the suction nozzle 18, air that is present between the second layer and the fiber composite components is sucked out through the second layer 12, thus ensuring that a uniform pressure is applied to a joining zone 3 in the same way as with just one layer. With this arrangement, however, it is advantageously possible even for gases liberated in the welding process to be sucked off easily through the second diaphragm during the welding process. In this way, it is additionally possible to avoid or reduce porosity in the welding zone.

(68) FIG. 9 shows a longitudinal section through an apparatus 24A for thermally joining thermoplastic fiber composite components according to another embodiment.

(69) In this embodiment of the apparatus 24A, in contrast to the previous embodiments, welding energy is input by induction into the fiber composite components 1, 2 to be joined. The vacuum arrangement 8A is designed to be permeable to magnetic fields. The fiber composite components 1, 2 are thus welded by alternating magnetic fields which are applied from outside the vacuum arrangement 8A and which induce eddy currents associated with resistance within the fiber composite components. For this purpose, an inductive welding device 32, e.g. in the form of an induction coil, is passed over the joining zone 3 from outside the vacuum arrangement 8A. To achieve this, the mounting device 32 can, for example, move continuously over the joining zone 3, as symbolized by the movement arrow depicted.

(70) In this embodiment, active cooling of the vacuum arrangement 8 is provided. For this purpose, a cooling fluid source 39, in this case, by way of example, in the form of a compressed air supply, is provided, which supplies a continuous flow of cooling fluid 40, in this case, by way of example, compressed air, over the vacuum arrangement 8. This ensures that an energy input in the centre of the joining zone 3, at the interface between the fiber composite components 1, 2, is significantly higher than in the outer region close to the surface.

(71) In other embodiments, other cooling methods or means of conveying cooling fluid, such as cooling ducts or the like, can of course be employed.

(72) FIG. 10 shows a longitudinal section through a modified apparatus 24B for thermally joining thermoplastic fiber composite components 1, 2.

(73) In this embodiment 25, in contrast to the previous embodiments, welding energy is input by a laser beam 10 into the fiber composite components 1, 2 to be joined.

(74) Here, the vacuum arrangement 8B provided is transparent for a predetermined laser radiation of a laser source 33, ensuring that the laser beam passes through. The fiber composite components 1, 2 are thus welded by the laser beam 10, which is introduced from outside the vacuum arrangement 8 and which moves along the joining zone. Since laser weld seams are relatively narrow, multiple parallel welding in the region of overlap 38 is also conceivable in this case.

(75) In this embodiment too, active cooling of the vacuum arrangement 8B is preferably provided, this being designed, by way of example, with a cooling fluid source 39 in the same way as explained with reference to FIG. 9.

(76) FIG. 11 shows a longitudinal section through another modified apparatus 24C for thermally joining thermoplastic fiber composite components.

(77) In this apparatus 24C, in contrast to the previous embodiments, welding energy is input by ultrasound into the fiber composite components 1, 2 to be joined. For this purpose, a welding device 46 in the form of an ultrasonic sonotrode is provided. The vacuum arrangement 8C is designed in such a way that it transmits the ultrasound from the outside into the joining zone. The fiber composite components 1, 2 are thus welded by ultrasound excited from outside the vacuum arrangement 8C by the sonotrode and transmitted via the vacuum arrangement 8C.

(78) In this embodiment too, active cooling of the vacuum arrangement 8 is preferably provided, this being designed, by way of example, with a cooling fluid source 39 in the same way as explained with reference to FIG. 9. Particularly in the case of a vacuum bag or a vacuum diaphragm as a vacuum arrangement 8C, it is possible in this way to avoid sticking.

(79) The vacuum diaphragm and the sonotrode are designed in such a way here that the vacuum diaphragm transmits or conducts the ultrasound into the joining zone.

(80) FIG. 12 shows a longitudinal section through an apparatus 26A for thermally joining thermoplastic fiber composite components 1, 2 according to another embodiment.

(81) This embodiment is once again an apparatus 26A for resistance welding. In this embodiment, however, a welding current is not introduced into the joining zone 3 via the fiber composite components 1, 2 to be joined themselves but via a welding filler material 6. This is a conductive welding filler material 6 of appropriate design which is introduced in the joining zone 3 between thermoplastic fiber composite components 1, 2 to be joined. For example, it can be a conductive thermoplastic prepreg layer.

(82) The pressurization arrangement 4 has electric contacts 5 which are arranged laterally on the joining zone 3 and to which the welding filler material 6 is connected. For this purpose, the welding filler material is guided at the longitudinal end of the joining zone 3 directly to the electric contact 5 connected in an airtight manner to the vacuum arrangement 8. Welding aids in the form of auxiliary inserts 37 for the delimitation of the joining zone 3 are provided laterally with respect thereto.

(83) In the embodiment illustrated, a vacuum arrangement 8 is likewise provided for pressurization. Here too, the pressure is applied before welding.

(84) Welding is performed by applying a welding current to the welding filler material 6, which is heated by the welding current, and the overlapping surfaces of the fiber composite components 1, 2 melts. Owing to the externally acting pressure, the melted surfaces are joined to the welding filler material 6 and are thus welded to one another.

(85) In other embodiments, the welding filler material 6 can be surrounded by an electrically non-conductive layer. Of course, the contact points are excepted from such a layer. An unwanted outflow of current into the fiber composite components is thus avoided. Instead, a current flow exclusively through the welding filler material is ensured, guaranteeing the desired uniform heat distribution across the entire welding filler material 6 and the corresponding melting of the fiber composite components 1, 2. The non-conductive layer is welded along with the remainder of the welding filler material in the joining zone 3. It is formed by glass fiber/thermoplastic prepreg layers, for example, and therefore it does not become conductive even when the matrix of the fiber composite components 1, 2 to be joined melts.

(86) FIG. 13 shows a longitudinal section through a modified apparatus 26B for thermally joining thermoplastic fiber composite components 1, 2 according to another embodiment.

(87) Apparatus 26B differs from the apparatus 26A shown in FIG. 12 in the guidance of the welding filler material 6 by the auxiliary inserts 37. The welding filler material 6 is thereby positioned reliably in the joining zone. Melting of the fiber composite components at the edges is furthermore avoided.

(88) With the modified guidance of the welding filler material 6, there is a change in the position of the electric contacts 5, which in this case are arranged at a lateral edge, next to the auxiliary inserts 37.

(89) In other embodiments, it is also possible for welding to be carried out without the auxiliary inserts 37.

(90) FIG. 14 shows a cross-sectional view of an apparatus 28 for thermally joining thermoplastic fiber composite components 1, 2 according to another embodiment.

(91) In this apparatus 28, there is a further variation of the guidance and contacting of the welding filler material 6. Here, the filler material extends across the joining zone 3 along the fiber composite components 1, 2. Auxiliary inserts 37 are provided at the longitudinal ends of the joining zone 3 in order to delimit the joining zone. The contacts 5 of the pressurization arrangement 4 are then provided in the regions adjoining the joining zone 3. The welding filler material 6 extends from both sides under the auxiliary inserts 37, in each case as far as a contact 5, which is arranged next to the joining zone 3 and by which a welding current is passed into the welding filler material 6.

(92) In the regions of the fiber composite components 1, 2 which adjoin the joining zone and along which the welding filler material 6 is guided beyond the joining zone 3, an insulating element 41 is provided for protection between the surface of the fiber composite components 1, 2 and the welding filler material 6. The insulating element 41 can be applied in the form of an insulating parting film between the welding filler material and the respective fiber composite component, for example, in order to avoid melting outside the joining zone 3.

(93) Here too, by way of example, the pressurization arrangement 4 is a vacuum arrangement 8.

(94) FIG. 15 shows a cross-sectional view of an apparatus 29 for thermally joining thermoplastic fiber composite components 1, 2 according to another embodiment.

(95) In this embodiment, the pressurization arrangement 4 is of fundamentally different construction. Although this is likewise a vacuum arrangement 8 having a suction nozzle 18, a flexible airtight mold 14 is provided here as a cover instead of a vacuum diaphragm, in contrast to the embodiments described above.

(96) In particular, the flexible mold 14 comprises a slightly elastically deformable silicone material, with the result that, when a vacuum is applied to the suction nozzle 18, a uniform surface pressure can be exerted on the joining zone 3, as with a vacuum film.

(97) In the region of the joining zone 3, the mold 14 is provided with conductive elements 42 as electric contacts 5, which extend in the thickness direction from an outer to an inner surface of the mold 14. In particular, these are metal bars, which are molded into the mold 14. These are designed and provided to introduce into the joining zone 3 a welding current applied from the outside by a welding electrode of a welding apparatus 31.

(98) The mold 14 is formed by a top part 16 and a bottom part 17, which are each flexible. In other embodiments, it would also be conceivable to provide an inflexible mold instead of the bottom part 17 and to form only the top part as a flexible mold 14.

(99) Here, the terms top and bottom part are in each case relative to the joining zone 3 and should not be taken as restrictive in respect of an absolute alignment of the mold 14.

(100) In respect of their shape, the top part 16 and the bottom part 17 are each matched to the component contour of the fiber composite components 1, 2, and therefore no welding aid inserts are required. By way of example, the suction nozzle 18 is provided only on the top part 16, although mounting on the bottom part is of course likewise conceivable. Furthermore, the conductive elements 42 in the region of the joining zone 3 are provided equally on the bottom part and on the top part.

(101) The mold 14 furthermore has circumferentially arranged integrated sealing lips 43, and therefore no additional sealing elements or adhesive joints are required here either.

(102) On its inner surface, the mold 14 furthermore has integrated channels for uniform pressure distribution over the covered area. In particular, the channels can be distributed in a net-like manner over the inner surface of the mold 14. In the embodiment illustrated, channels 44 of this kind are also provided in the region of the joining zone 3, by way of example, but this is envisaged only in the case of non-melting outer covering layers of the fiber composite components. If the covering layers of the fiber composite components 1, 2 also melt during welding, no channels are provided in the region of the joining zone.

(103) Overall, the flexible mold 14 is in this way configured to join fiber composite components 1, 2 in succession in a series production process with a comparatively high cycle rate, especially in comparison with a vacuum diaphragm, since no manual sealing or contacting measures are required. Instead, the mold 14 is simply closed after the insertion of the fiber composite component 1, 2 and the vacuum is applied, thus enabling the welding process to be started immediately.

(104) In another embodiment, the metal bars can furthermore be of magnetic design. For this purpose, they can be designed as a permanent magnet or as the core of an electromagnet with a coil wound round the outside.

(105) FIG. 16 shows a segment of a cross-sectional view of a modification of the apparatus 29 of the embodiment shown in FIG. 15.

(106) In this modification, the individual conductive elements 42 are each provided with a single welding electrode or a single controllable section of a welding electrode of a welding device 31′. In this way, differential control of the electrode and hence also of the current transfer into the joining zone 3 via the conductive elements 42 are made possible, contributing to better control of the current flow distribution.

(107) FIG. 17 shows a longitudinal section through the apparatus 29 shown in FIG. 15.

(108) The longitudinal section plane extends along the joining zone 3, along which the welding electrodes of a welding device 31 are guided over the pressurization arrangement 4 in order to weld the fiber composite components 1, 2, as symbolized by the arrows depicted. The welding electrodes are thus brought into contact successively on the outside of the mold 14 with the conductive elements 42 arranged along the joining zone 3, with the result that the elements introduce the welding current into the joining zone 3 at the respective point, depending on the position of the electrodes.

(109) Integrated sealing lips 43 can also be seen in the longitudinal section at the longitudinal ends of the mold 14. The vacuum channels 44 are furthermore also provided at the longitudinal ends of the inner side of the mold 14, which accommodates the fiber composite components 1, 2.

(110) FIG. 18 shows a plan view of the apparatus 29 shown in FIG. 17.

(111) The conductive elements 42 which form electric contacts 5 of the pressurization arrangement 4 are arranged so as to be distributed in a matrix-like or grid-like manner over the joining zone 3. The conductive elements 42 are contacted successively by a longitudinal movement of the welding electrodes of the welding device 31.

(112) In this respect, a grid-like arrangement of the vacuum channels 44 provided on the inner side of the mold 14 is furthermore illustrated schematically in this view. In actual fact, however, the channels 44 are concealed from the outside. The sealing lips 43 running around the circumference of the mold 14 furthermore illustrated schematically, and these are likewise concealed in actual fact.

(113) In other embodiments, the welding energy can also be transmitted to the component surface in the form of ultrasound from a sonotrode via conductive elements 42 in the joining zone 3 which are in the form of metal bars embedded in the mold 14.

(114) FIG. 19 shows a cross-sectional view of an apparatus 30 for thermally joining thermoplastic fiber composite components 1, 2 according to another embodiment.

(115) In this embodiment, a flexible mold 14 is likewise provided as a pressurization arrangement 4. In contrast to the embodiments described above, an additional pressure is applied magnetically in this pressurization arrangement. For this purpose, a magnet arrangement 7 integrated into the mold 14 is provided in the region of the joining zone 3. In this embodiment, pressurization thus comprises the application of magnetic forces.

(116) The magnet arrangement 7 is provided in the region of the joining zone. In the joining zone, the pressurizations by the vacuum arrangement 8 and the magnet arrangement 7 are thus added together.

(117) In the embodiment illustrated, the magnet arrangement is, by way of example, a multiplicity of bar magnets 45 molded into the mold 14, which magnetically compress the mold 14 in the region of the joining zone.

(118) In other embodiments, it would also be conceivable to implement the magnet arrangement 7 by one or more electromagnets.

(119) It is furthermore conceivable to provide the magnet arrangement 7 independently of a vacuum arrangement.

(120) In the embodiment illustrated, in a manner similar to that described with reference to FIG. 13, a welding filler material 6 is inserted in the joining zone between the fiber composite components 1, 2 to be joined. Here, this material is contacted by conductive elements 42, which are arranged laterally with respect to the joining zone, are likewise integrated into the mold 14 and form the electric contacts 5. For this purpose, the conductive elements 42 are arranged in a manner laterally offset next to the joining zone 3. The welding filler material 6 extends through the joining zone 3 into the lateral regions and is contacted there by the conductive elements 42.

(121) By virtue of the overlapping arrangement of the components 1, 2, a first contact 5, which is formed with the conductive elements 42 and is arranged on the right, next to the joining zone 3, in the cross-sectional view illustrated, is provided on the top part 16. A second contact 5, which is formed with conductive elements 42 and is arranged on the left, next to the joining zone, in the cross-sectional view illustrated, is provided in the bottom part 17, on the opposite side of the joining zone 3.

(122) An insulating element 41 for protecting the fiber composite components 1, 2, e.g. in the form of an insulating parting film, is provided in the region of the contacts 5, on a side of the filler material 6 which faces the respective fiber composite component 1, 2.

(123) In a modification of the embodiment illustrated here, it would also be conceivable, when there is no welding filler material in the region of the joining zone, to use the bar magnets 45 extending in the thickness direction through the bottom part and/or the top part simultaneously as electric contacts for conducting a welding current. In this case, the bar magnets 45 would simultaneously be designed as electric contacts 5 for welding the fiber composite components.

(124) FIG. 20 shows a plan view of the apparatus shown in FIG. 19.

(125) In this view, which shows a plan view of the top part 16, the regular grid-like arrangement of the bar magnets 45 provided in the region of the joining zone 3 can be seen, the arrangement ensuring uniform pressure conditions in the joining zone 3.

(126) The conductive elements 42, which are provided as electric contacts 5, are likewise arranged in a grid-like manner and are arranged laterally offset along the joining zone can furthermore be seen. The welding filler material 6 is thus contacted on the long sides of the joining zone 3. To weld the fiber composite components 1, 2, a welding electrode of the welding device 31 accordingly travels in the longitudinal direction along the electric contacts 5 and, in the process, successively contacts the conductive elements 42, as symbolized by the movement arrow depicted. On the opposite side, a second welding electrode of opposite polarity of the welding device 31 moves in parallel thereto in the same way along the electric contacts 5 of the bottom part 17.

(127) During welding and also following the welding operation, during cooling, the bar magnets 45 of the magnet arrangement 7, which are provided in the top part 16 and in the bottom part 17, keep the joining zone 3 under an additional pressurization supplementary to the applied vacuum.

(128) In other embodiments, it would also be conceivable, instead of a bilateral magnet arrangement, to provide unilateral positioning of magnets on one side and a magnetizable medium on the other side.

(129) In all the embodiments, materials provided in the region of the joining zone, e.g. films, molds or textiles, which are in contact with the material of the fiber composite components which is to be welded are preferably embodied in such a way that, even after the melting and cooling of thermoplastic matrix of the parts to be joined, they can be separated therefrom again. For this purpose, they can be treated with a parting agent, for example. As an alternative or in addition, an embodiment consisting of or comprising a non-adhering material or a corresponding coating is also possible.

(130) FIG. 21 shows a longitudinal section through an apparatus 25A for thermally joining thermoplastic fiber composite components 1, 2 according to another embodiment.

(131) This embodiment differs from the embodiment shown in FIGS. 19 and 20 in that the welding filler material 6 is not contacted on the long sides here but on the short sides of the respective longitudinal ends of the joining zone 3. For this purpose, conductive elements 42, which are embedded in the mold 14, are here designed as metal bars and form contacts 5 that contact the welding filler material 6, are provided in the same way as described with reference to FIG. 19. The contacts 5 are coupled to a welding device 47 having fixed electrodes.

(132) In the embodiment illustrated, the contacts 5 and the electrodes of the welding device 47 are provided both on the bottom side and on the top side of the mold 14. In this case, the metal bars can simultaneously be designed as bar magnets. In this way, reliable contacting of the welding filler material 6 between the upper and lower contacts 5 is ensured.

(133) In other embodiments, it is also possible to provide only unilateral contacts 5 for each pole, e.g. only on the top side 16 or the bottom side 17 of the flexible mold 14 or, in the case of a mold 14 that is flexible on only one side, on the top side.

(134) In the embodiment illustrated, the pressurization is provided by a vacuum arrangement 8. A vacuum, which is applied via an air suction nozzle 8 (not visible in the sectional view illustrated), acts uniformly via the channels 44 across the entire joining zone 3, which is sealed off airtightly by the sealing lips 43.

(135) FIG. 22 shows a longitudinal section through a modified apparatus 25B for thermally joining thermoplastic fiber composite components.

(136) In this modification, the pressurization arrangement has, in the joining zone 3, a magnet arrangement 7 having a multiplicity of bar magnets 45 distributed along the joining zone 3 and embedded in the mold 14, as explained in greater detail with reference to FIG. 19.

(137) In principle, the magnet arrangement 7 can be provided as an alternative or in addition to a vacuum arrangement 8 shown in FIG. 21. In the embodiment illustrated, the magnet arrangement 7 is provided in addition to the vacuum arrangement 8.

(138) FIG. 23 shows a longitudinal section through another modified apparatus 25C for thermally joining thermoplastic fiber composite components.

(139) In this embodiment, a welding device 48 is provided with stationary electrodes which extend into the mold 14 at the level of the joining zone 3, at the longitudinal ends of the joining zone 3, to a point directly adjoining the welding filler material 6. Here, the electrodes are fixed to the magnet arrangement 7 in the mold 14 and are pressed together with the welding filler material 6 for reliable contacting.

(140) The pressurization arrangement 4 thus has the magnet arrangement 7, which in this case once again comprises a multiplicity of bar magnets 45, by way of example. In other embodiments, electromagnets can also be provided as an alternative or in addition to bar magnets.

(141) Here too, in addition, a vacuum arrangement 8 as described with reference to FIG. 21 is also provided. In other embodiments, the magnet arrangement 7 can also be provided without a vacuum arrangement 8.

(142) FIG. 24 shows a cross-sectional view of an apparatus shown in FIG. 22 or FIG. 23.

(143) In this illustration, it is possible to see the arrangement of the welding filler material 6 in the overlap between the fiber composite components 1, 2 to be joined. The welding filler material 6 is designed to extend beyond the joining zone 3 or beyond the overlap on the long sides of the joining zone 3. In this way, cooling of the joining zone 3 in the region of the component edges 50, 51 is avoided. Melting of the component edges 50, 51 and complete welding is thus ensured.

(144) Since the component edges 50, 51 also melt, a parting agent 49 is in each case provided adjoining the welding filler material 6 extending beyond the overlap, creating a defined end of the region that has melted beyond the joining zone 3. Here, by way of example, the parting agent 49 is designed as an adhesive tape with a parting coating.

(145) FIG. 25 shows a cross-sectional view of another modified apparatus for thermally joining thermoplastic fiber composite components.

(146) In this embodiment, electrically non-conductive auxiliary inserts 52 are applied directly adjoining the component edges 50, 51, on both sides of the overlapping joint between the fiber composite components 1, 2 and the mold 14, and these are also compressed during the pressurization. Here, the welding filler material 6 is extended partially beyond the auxiliary inserts 52 at the edge of the joining zone 3. Here too, parting agents 49 are provided adjoining the welding filler material 6.

(147) The auxiliary inserts 52 have the same thermal conductivity as the material of the fiber composite components 1, 2, and therefore the heat of welding is transmitted as far as the component edges 50, 51. Thus, the component edges 50, 51 also melt, and a geometry of the weld seam end is defined by the auxiliary inserts 52.

(148) For this purpose, the auxiliary inserts 52 are preferably manufactured from the same material as the fiber composite components and are merely enclosed with a non-conductive film or coating. In this way, a desired complete welding through the component edges 50, 51 with a predefined geometry is made possible.

(149) FIG. 26 shows a cross-sectional view of an apparatus 27 for thermally joining thermoplastic fiber composite components according to another embodiment.

(150) In this embodiment, in comparison with FIG. 25, the arrangement of the welding filler material 6 and of the auxiliary inserts 52 in the region of the joining zone 3 is the same.

(151) However, the apparatus 27 differs decisively in the type of cover for the pressurization arrangement 4, which is not formed here by a flexible mold 14 but by a vacuum diaphragm 9, as described with reference to FIGS. 12 and 13. In this case, the contacts 5 are provided at the longitudinal ends of the joining zone 3 and can be designed in the manner described with reference to FIG. 12 or 13, for example.

(152) Although the disclosure herein has been described fully above by preferred illustrative embodiments, it is not restricted thereto but can be modified in many different ways.

(153) In particular, the following further embodiments are envisioned and possible:

Possible Embodiment 1

(154) Method for thermal welding of thermoplastic fiber composites, wherein the two mating parts to be connected are surrounded airtightly (or approximately airtightly) by a vacuum structure during the welding operation, at least in the welding zone, wherein air is evacuated from this zone by using a vacuum pump or reduced pressure pump, wherein a vacuum or at least a pressure lower than the ambient pressure prevails there, with the result that the compression of the mating parts required for welding is achieved by the pressure difference between the ambient pressure and the internal pressure in the vacuum structure.

Possible Embodiment 2

(155) Method according to embodiment 1, wherein thermal energy required for welding is introduced by using laser energy or electric induction or ultrasound (see FIG. 9 and FIG. 10).

Possible Embodiment 3

(156) Method according to embodiment 1, wherein thermal energy required for welding is introduced by a current flow through the mating parts themselves (see FIGS. 1 to 8 and 14 to 17) or through a filler material (see FIGS. 11 to 13 and 18, 19).

Possible Embodiment 4

(157) Method according to embodiment 3, wherein, in the region where the current is introduced, the vacuum film used in the remaining region (or other vacuum barrier, e.g. a silicone mold) is replaced locally by an electrically conductive medium (e.g. a metal foil, metal pieces or an electrically conductive, approximately airtight textile), wherein the vacuum film (or vacuum barrier) and the electrically conductive medium (e.g. foil or textile) are connected in such a way (e.g. by an adhesive tape) that the (approximate) vacuum tightness of the vacuum structure continues to be maintained.

Possible Embodiment 5

(158) Method according to embodiment 4, wherein the region provided for the introduction of current is divided into segments composed of electrically conductive medium (e.g. metal pieces, foil or textile), wherein the (metal-piece, foil or textile) segments do not touch directly but are connected (approximately) airtightly by an electrically non-conductive intermediate material, with the result that, although a current can flow from an electrode touching segment in the thickness direction into the material to be welded or into the filler material, the current flow cannot propagate sideways into or across other segments.

Possible Embodiment 6

(159) Airtight or approximately airtight medium (e.g. silicone mold, film or textile), wherein this has a significant electric conductivity only in the thickness direction but has no significant electric conductivity in directions parallel to the surface (e.g. of the silicone mold, of the film or of the textile).

Possible Embodiment 7

(160) Semi-permeable medium (e.g. silicone mold, film or textile), which is permeable to air but is (virtually) impermeable to the partially melted or liquefied matrix material of the mating parts and has a significant electric conductivity only in the thickness direction but no significant electric conductivity in directions parallel to the surface (e.g. of the silicone mold, of the film or of the textile).

Possible Embodiment 8

(161) Mold, film or textile according to embodiment 6 or 7, wherein this is composed of a multi-material mix consisting of or comprising conductive and non-conductive materials, e.g. of metal particles embedded in plastic film, metal bars embedded in silicone or metal threads introduced into a synthetic fiber textile, which touched the two surfaces of the mold, film or textile but touch each other only occasionally or not at all in the direction of the surface. Possible embodiment 9. Method according to embodiment 3, 4 or 5, wherein a mold, a film or an approximately airtight textile according to embodiment 6 or 8 is used for the entire vacuum structure or the local inserts in the vacuum structure (see FIGS. 5, 6 and 7).

Possible Embodiment 10

(162) Method according to one of embodiments 1-5 or 9, wherein the electrodes or the other energy sources for introducing heat during the welding operation are moved along the weld seam.

Possible Embodiment 11

(163) Method according to embodiment 10, wherein, where electrodes are used for energization, the electrodes have rollers or brushes which are optimized for moving contact.

Possible Embodiment 12

(164) Method according to the embodiment 11, wherein an electrically conductive paste is provided to improve contacting between the electrodes and the electrically conductive medium of the vacuum bag.

Possible Embodiment 13

(165) Method according to one of embodiments 1-5 or 9-12, wherein an inner vacuum bag consists of a semi-permeable medium (permeable to air but impermeable to matrix material of the mating parts), if appropriate according to embodiment 7 (in the case of resistance welding according to embodiment 3-5 or 10-12), and an outer vacuum bag consists of a medium which is (virtually) impermeable to air, if appropriate according to embodiment 6 (in the case of resistance welding according to embodiment 3-5 or 10-12).

Possible Embodiment 14

(166) Method for thermal welding of thermoplastic fiber composites, wherein the two mating parts to be connected are compressed by magnetic forces during the welding operation, at least in the welding zone, e.g. by bilateral positioning of mutually attracting magnets or by unilateral positioning of magnets and a magnetizable medium on the other side.

Possible Embodiment 15

(167) Method according to one of embodiments 1-13, combined with a method according to embodiment 14.

Possible Embodiment 16

(168) Method according to one of embodiments 14 or 15, wherein a current flow is introduced through the magnets themselves.

(169) The vacuum structure mentioned in embodiment 1 can either consist of film or textile or of a flexible mold on both sides or can consist of one of these on only one side and of an inflexible mold on the other side.

(170) The use of film structures is more practical for small series and prototypes, while, for series applications involving mold parts that are always the same, the use of a flexible mold produced for this purpose saves more time.

(171) The method can be used for spot welds, but the electrodes are preferably moved in a linear manner along a weld seam. It is advantageous if the compression pressure exerted by the vacuum is maintained even during the cooling phase, after the electrodes have moved on. As an alternative, it can also be used for linear welds by a filler material (see FIGS. 11, 12 and 26), in which the electrodes too are not moved but merely rest on both ends. Here, the vacuum or magnetic welding method has the advantage that the pressure can be applied in a uniformly distributed manner over the entire line without using large, expensive and very accurately fitting molds on both sides.

(172) The films, molds or textiles used, which are in contact with the material to be welded, are preferably embodied in such a way that, even after the melting and cooling of the matrix of the parts to be joined, they can be separated therefrom again. They could be treated with a parting agent, for example, or could be composed of a non-adhesive material.

(173) Embodiment 13 and FIG. 8 describe the use of a semi-permeable diaphragm in combination with an outer airtight vacuum bag as a vacuum arrangement. This advantageously makes it easier to extract gases liberated during the welding process. Porosity in the welding zone is thus avoided or reduced. When using resistance welding, both vacuum bags can additionally also be designed to allow the passage of current.

(174) For embodiment 14, both permanent magnets and electromagnets can be used.

(175) The auxiliary inserts 37 shown in the figures (auxiliary welding inserts) make it easier to produce the vacuum arrangement 8 in as much as they prevent the formation of creases in the region of the adhesive tapes in order to facilitate airtight connection. The auxiliary inserts can be formed either from non-conductive material or from conductive material wrapped in non-conductive film or provided with a non-conductive coating.

(176) The auxiliary inserts are composed of a material with a sufficiently high melting temperature, and therefore they do not melt during the welding process. This also applies to the films, molds and textiles used.

(177) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a”, “an” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

REFERENCE SIGNS

(178) 1 fiber composite component 2 fiber composite component 3 joining zone 4 pressurization arrangement 5 electric contact 5a, 5b, 5c, . . . , 5n contact sections 6 welding filler material 7 magnet arrangement 8 vacuum arrangement 9 vacuum diaphragm 10 laser beam 11 diaphragm 12 second layer 13 first layer 14 mold 15 direction of extent of main surface 16 top part 17 bottom part 18 suction nozzle 19 sealing element 20 apparatus 21 apparatus 22 apparatus 23 apparatus 24A; 24B; 24C apparatus 25A; 25B; 25C apparatus 26A; 26B apparatus 27 apparatus 28 apparatus 29 apparatus 30 apparatus 31 welding device 32 welding device 33 welding device 34 welding device 35 welding device 36 adhesive tape 37 auxiliary inserts 38 region of overlap 39 cooling fluid source 40 cooling fluid 41 insulating element 42 conductive element 43 sealing lip 44 vacuum channel 45 bar magnet 46 welding device 47 welding device 48 welding device 49 parting agent 50 component edge 51 component edge 52 auxiliary inserts