METHOD FOR CONNECTING COMPONENTS, ONE OF WHICH IS MADE OF A FIBER-REINFORCED PLASTIC

Abstract

A method and a connecting element for joining two components, at least one of which is made of a fiber-reinforced composite, are proposed.

Claims

1. A method for joining at least two components (13, 15), wherein at least one component (13) is made of a fiber-reinforced plastic, comprising joining the at least two components (13, 15) to establish a form-fit connection by setting a dome (1) made of a filled plastic, preferably glass fiber-reinforced polyamide or polypropylene, in rotation, oscillation, and/or a circular motion and inserting it into the components (13, 15) to be connected by applying an axial force.

2. The method according to claim 1, wherein at least one of the components (13, 15) to be joined is punched prior to the joining.

3. The method according to claim 1, wherein the rotation, oscillation, and/or circular motion of the dome (1) are/is ended and the dome (1) is subsequently pressed in the axial direction against the components (13, 15) to be connected.

4. The method according to claim 1, wherein the rotation speed, the material of the dome (1), the material fill at the dome (1), the duration of the joining operation (II), and/or the duration of the pressing operation (III) are/is selected as a function of the components (13, 15) to be connected.

5. A dome (1) for connecting at least two components, wherein the dome (1) is made at least partially of a thermoplastic plastic and the dome (1) has a head (5), and wherein the dome (1) is made of a filled plastic, preferably glass fiber-reinforced polyamide or polypropylene, wherein the dome (1) is designed for carrying out the method of claim 1.

6. The dome (1) according to claim 5, wherein the head (5) of the dome (1) is designed for accommodation in a drive device and/or for transmitting torques.

7. The dome (1) according to claim 5, wherein the dome (1) has a central axial borehole (11).

8. The dome (1) according to claim 5, wherein the dome (1) has a shank, preferably a truncated conical shank (3).

9. The dome (1) according to claim 5, wherein the diameter (D.sub.1) of the shank (3) at its end facing away from the head (5) is essentially equal to the diameter of the holes (17, 19) in the components (13, 15) to be connected.

10. The dome (1) according to claim 5, wherein the proportion of filler in the dome (1) is 10 to 50% by weight, particularly preferably 30% by weight.

11. An assembly unit comprising at least two components (13, 15), wherein at least one component (15) is made of a fiber-reinforced plastic, wherein the at least two components (13, 15) are joined by one or more domes (1) made of a filled plastic, preferably glass fiber-reinforced polyamide or polypropylene, using a method according to claim 1.

12. The assembly unit according to claim 11, wherein at least the component (13) that is situated facing away from the head (5) of the dome (1) is made of a fiber-reinforced plastic.

13. The assembly unit according to claim 11, wherein the fiber-reinforced plastic contains a thermoplastic or thermosetting matrix and/or fibers made of carbon, glass, and/or aramid.

Description

[0040] The drawings show the following:

[0041] FIGS. 1 and 2 show two exemplary embodiments of the domes according to the invention,

[0042] FIG. 3 shows two components to be joined together, with holes already introduced,

[0043] FIGS. 4 to 6 show various exemplary embodiments of the method according to the invention for joining the components illustrated in FIG. 3, in various stages,

[0044] FIG. 7 shows the time sequence of the method for joining according to the invention, and

[0045] FIGS. 8 and 9 show further exemplary embodiments of the joining method according to the invention.

[0046] FIG. 1 illustrates a dome which is denoted overall by reference numeral 1. The dome 1 includes a shank 3 having a truncated conical design, and a head 5. One end of the shank 3 facing away from the head 5 has a diameter D.sub.1 that is smaller than a diameter D.sub.2 of the shank 3 in the immediate proximity of the head 5. The diameter D.sub.3 of the head 5 in turn is larger than the diameter D.sub.2 of the shank 3.

[0047] Indicated in the illustration of the head 5 is a hexagon socket 7 which may be used to accommodate the dome 1 in a drive device of a friction welding machine (not illustrated). Of course, other types of torque transmission between a drive device and the dome 1 are possible. For example, the head 5 may be designed as an external hexagon or polygon, and the torque required for the friction welding may be transmitted to the dome 1 in this manner.

[0048] The shank 3 preferably has a conical design, since the design specifies to a certain extent how much material of the shank 3 is heated and melted on (weld filler material) during the joining according to the invention. This is the truncated conical portion of the shank 3, as is apparent from FIG. 4.

[0049] The design of the weld filler material may be appropriately set over a very wide range via the length L of the shank 3 and the cone angle , depending on the requirements of the application.

[0050] On an end 9 of the shank 3 opposite from the head 5, the shank 3 has a concave shape or some other shape so that it is well centered in a predrilled hole 17, 19 in the components to be joined.

[0051] If there are no predrilled holes in the components to be joined, the end 9 of the shank 3 is preferably designed in such a way that the shank 3 bores or introduces the holes into the components.

[0052] FIG. 2 illustrates another exemplary embodiment of a dome 1 according to the invention. Identical components are provided with the same reference numerals, and the statements made concerning the other figures correspondingly apply.

[0053] The essential difference between the dome 1 according to FIG. 2 and the first exemplary embodiment according to FIG. 1 is that the dome 1 according to FIG. 2 has an axial borehole 11, which in the present case is designed as a through hole.

[0054] It is self-evident that the axial borehole 11 may also be designed as a blind hole (not illustrated), for example when gases or liquids are not supposed to flow through the dome 1. It is possible for the axial borehole 11 to be designed as a blind hole, beginning at the end 9 of the shank 3, or for the axial borehole to begin in the head 5 of the dome 1 and to end before reaching the end 9.

[0055] FIG. 3 illustrates by way of example a first component 13 and a second component 15 in cross section. The first component 13 may be a metal sheet, for example, made of a metallic material, while the second component 15 may be made of a fiber composite, for example containing carbon fibers and a thermoplastic matrix. For reasons of simplicity in the illustration, the two components 13 are illustrated as plate-shaped components having multiple mutually spaced holes 17 and 19 which may be introduced into the components 13, 15 in a prior optional method step.

[0056] Alternatively, it is possible for the components 13, 15, without holes, to be placed one on top of the other in the desired position (see FIG. 8).

[0057] It is also possible for only one of the components 13, 15 to be prepunched, and for the two components to be placed one on top of the other in the desired position prior to joining (see FIG. 9).

[0058] The joining operation according to the invention then begins by setting the dome in rotation and/or oscillation. At the same time, the dome penetrates into the components 13, 15, thus producing the required hole or holes.

[0059] The midpoints of the holes 17 and 19 in the two components 13 and 15 are congruent. In the illustrated exemplary embodiment, the diameters of the holes 17 and 19 are also equal, although this is not mandatory. It is also possible for the holes to have different diameters, and for the dome 3 to correspondingly have a stepped shank. This variant is illustrated in greater detail in FIG. 6.

[0060] In many applications, it is not sufficient to connect the two components 13 and 15 using only one dome 1; rather, multiple friction welding connections according to the invention are mounted at a distance from one another, similar to a row of rivets, in order to achieve sufficient strength.

[0061] FIG. 4 illustrates, only by way of example, the joining operation in three stages I, II, and III. Beginning on the left side in FIG. 4, the dome 1 is centered over the previously introduced holes 17 and 19 (I in FIG. 4) and subsequently set in rotation, and at the same time, pressed downwardly with rotation in FIG. 4, first through the hole 17 in the first component 13 and then through the hole 19 in the second component 15.

[0062] This intermediate stage of the joining operation (II in FIG. 4) is illustrated in the middle portion of FIG. 4. It is apparent that the truncated conical portion of the shank 3 is softened and partially removed, due to the rotary motion and the resulting friction between the shank and the holes 17 and 19, until it has a cylindrical shape whose diameter corresponds to the diameter of the holes 17 and 19. As soon as the head 5 of the dome 1 contacts the surface of the first component 13, friction also results at the ring-shaped contact surface between the head 5 and the component 13, and at least the bottom portion of the head 5 correspondingly melts and becomes flowable. The rotation of the dome is subsequently ended, and the so-called compression phase (III in FIG. 4) is initiated. This state is illustrated at the far right in FIG. 4. In this state, only a force F which acts in the axial direction on the head 5 of the dome 1 is exerted on the dome 1, so that the bottom side of the head 5 is optimally joined to the first component 13.

[0063] When the first component 13 is made of a fiber-reinforced plastic, ideally with a thermoplastic matrix, a circular first joining surface 21 results at that location, which due to its geometric dimensions is able to transmit relatively large forces. A cylindrical second joining surface 23 results between the hole 17 in the first component 13 and the shank 3 of the dome 1, and a further, third joining surface 25 which is likewise cylindrical results between the hole 19 in the second component 15 [and the shank 3].

[0064] It is apparent from the listing of the three joining surfaces 21, 23, and 25 and their sizes that a very intensive, load-bearing connection between the dome 1 and the first component 13 and between the dome 1 and the second component 15 may be achieved with the method according to the invention. Since the dome 1 together with its shank 3 has sufficient wall thickness and sufficient strength, high forces may be transmitted between the first component 13 and the second component 15 via the dome 1.

[0065] It is also conceivable to join the two components 13, 15 via the dome 1 without introducing the holes 17, 19 into the components beforehand. It is possible for the dome 1 itself to produce the required installation space, for example by melting onto the components 13, 15 in areas when it is rotationally or oscillatingly driven. This situation is schematically illustrated in FIG. 8. In the stage denoted by reference numeral II, it is apparent how the dome 1 has partially displaced the material of the components 13 and 15 in order to create space.

[0066] In the stage denoted by reference numeral III, a ridge (no reference numeral) which extends around the dome 1 and is joined to same is visible on the bottom side of the component 15. If the components 13 and 15 are not prepunched, these production steps are dispensed with, and the connection between the components 13 and 15 is particularly strong due to the fact that the unmelted core of the dome 1 establishes a form-fit connection, while the melted and subsequently resolidified areas form an integral bond connection.

[0067] FIG. 9 schematically illustrates the joining method according to the invention, using the example of a prepunched component 13 and a component 15 which is not prepunched. In the stage denoted by reference numeral II, it is apparent how the dome 1 has partially displaced the material of the components 13 and 15 in order to create space.

[0068] However, it may still be advantageous to punch the components 13, 15 prior to joining, and to introduce the holes 17, 19 prior to joining. The prior step of punching or introducing the holes 17, 19 may be necessary in particular for metallic components, or for components 13, 15 having a hard cover layer, such as a thermosetting cover layer.

[0069] A high-performance joint connection also results when the first component 13 is made of metal. In that case, however, the joining surfaces 21 and 23 are dispensed with, since the melted-on thermoplastic material of the dome 1 does not form an integral bond connection with a metal of the first component 13.

[0070] However, a force-fit connection then results between the head 5 and the second component 15, so that, similarly to a rivet or screw connection, a secure connection results between the components 13 and 15 with only an integral bonded joining surface 25.

[0071] If such a connection is to be exposed to particularly high stresses, it may be advantageous to provide a through axial borehole 11 in the dome 1, and to provide a screw together with a corresponding nut and a washer in this axial borehole 11. FIG. 5 schematically illustrates such an exemplary embodiment in a greatly simplified manner. In the right portion of FIG. 5, a screw 27 is inserted through the dome 1 according to the invention or the axial borehole 11 thereof, a washer 29 is placed thereon, and a nut 31 is screwed on. The washer 29 has a circumferential collar 30 which ensures that the washer 29 rests on the second component 15 and not on the end 9 of the dome 1. In this exemplary embodiment, a connection capable of bearing extreme load is securely and reliably possible, even with difficult material configurations/material pairings, and no contact corrosion occurs at the screw 27 and nut 31.

[0072] FIG. 6 illustrates another exemplary embodiment of an assembly unit according to the invention and the method according to the invention, in which the holes 17 and 19 have different diameters. Accordingly, the dome 1 has a stepped design. The diameter of a shoulder 33 of the shank 3 is matched to the diameter of the hole 17 in the first component, while the other portion of the shank 3 is matched to the diameter of the hole 19 in the second component. It is thus possible, for example, to enlarge the joining surface 23. It is self-evident that this embodiment functions when the first component is made of a fiber-reinforced composite or a metallic material.

[0073] FIG. 7 schematically illustrates possible time sequences of the method according to the invention in diagram form. Time is plotted on the abscissa.

[0074] A first line 35 qualitatively represents the change over time of the axial force exerted on the dome 1.

[0075] A second line 37 qualitatively represents the change over time of the rotation speed of the dome 1.

[0076] The various method steps are indicated by the numbers I, II, and III corresponding to FIG. 4.