Connection element, connection arrangement, method for producing a connection element and method for producing a connection arrangement

Abstract

A connection element includes a composite component with a cured epoxy resin, a first layer including a first thermoplastic polymer and an intermediate layer arranged between the composite component and the first layer, the first layer containing both the cured epoxy resin of the composite component and the first thermoplastic polymer of the first layer. The first thermoplastic polymer has a melting point above a curing temperature of the epoxy resin and is soluble at a temperature of at least 150? C. in the epoxy resin used for producing the composite component.

Claims

1. A connection element comprising: a composite component comprising a cured epoxy resin; a first layer comprising a first thermoplastic polymer; an intermediate layer arranged between the composite component and the first layer and containing both the epoxy resin of the composite component and the first thermoplastic polymer of the first layer; wherein the first thermoplastic polymer has a melting point, in particular a glass transition temperature, above a curing temperature of the epoxy resin; wherein the first thermoplastic polymer is soluble at a temperature of at least 150? C. in the epoxy resin used for producing the composite component; wherein the curing temperature of the epoxy resin is up to 180? C.; wherein the glass transition temperature of the first thermoplastic polymer is higher than 185? C., in particular higher than 200? C.; and wherein the epoxy resin extends into the intermediate layer, from the composite component towards the first layer, in a form of a number of volume portions which are mutually adjacent or interconnected at least in part, wherein the volume portions are configured as bubbles and have, in a region of the intermediate layer that is adjacent to the composite component, a diameter or a volume that is greater than in a region of the intermediate layer that is adjacent to the first layer.

2. The connection element of claim 1, wherein the first layer is provided externally on the composite component.

3. The connection element of claim 1, wherein the first layer consists of the first thermoplastic polymer.

4. The connection element of claim 1, wherein the first thermoplastic polymer is selected from at least one of a group consisting of polyetherimide, polysulphone, polyphenylsulphone, polyhydroxyether, and polycarbonate.

5. The connection element of claim 1, wherein the first layer has a thickness in a range of greater than 50 micrometers (?m) to less than or equal to 300 ?m.

6. The connection element of claim 5, wherein the thickness of the first layer is in a range of from 100 ?m to 150 ?m.

7. The connection element of claim 1, wherein the composite component comprises a fiber-reinforced plastics material.

8. The connection element of claim 7, wherein the fiber-reinforced plastics material is configured as a carbon-fiber-reinforced plastics material.

9. The connection element of claim 1, wherein the composite component comprises a sandwich structure comprising a fiber-reinforced plastics material cover layer.

10. The connection element of claim 9, wherein the fiber-reinforced plastics material cover layer is a carbon-fiber-reinforced plastics material cover layer.

11. The connection element of claim 1, comprising a second layer having a second thermoplastic polymer arranged on the first layer.

12. The connection element of claim 11, wherein the second thermoplastic polymer is selected from at least one of a group consisting of polyetheretherketone, polyethersulphone, polyamide, and polyphenylsulphone.

13. The connection element of claim 1, wherein the intermediate layer has a thickness in a range of from 20 micrometers (?m)to 100 ?m or from 30 ?m to 80 ?m.

14. The connection element of claim 13, wherein the thickness of the intermediate layer has a is in a range of from 30 ?m to 80 ?m.

15. The connection element of claim 1, wherein the intermediate layer comprises a continuous concentration transition from the epoxy resin to the first thermoplastic polymer.

16. The connection element of claim 1., wherein the diameter of the volume portions in the region of the intermediate layer that is adjacent to the composite component is greater than 1 micrometer (?m) and is less than 1 ?m in the region of the intermediate layer that is adjacent to the first layer.

17. The connection element of claim 16, wherein the diameter of the volume portions in the region of the intermediate layer that is adjacent to the composite component is in a range of from 1 ?m to 20 ?m.

18. The connection element of claim 16, wherein the diameter of the volume portions in the region of the intermediate layer that is adjacent to the first layer is less than 0.1 ?m.

19. A connection arrangement comprising: a connection element comprising: a composite component comprising a cured epoxy resin; a first layer comprising a first thermoplastic polymer; and an intermediate layer arranged between the composite component and the first layer and containing both the epoxy resin of the composite component and the first thermoplastic polymer of the first layer; wherein the first thermoplastic polymer has a melting point, in particular a glass transition temperature, above a curing temperature of the epoxy resin; wherein the first thermoplastic polymer is soluble at a temperature of at least 150? C. in the epoxy resin used for producing the composite component; wherein the curing temperature of the epoxy resin is up to 180? C.; wherein the glass transition temperature of the first thermoplastic polymer is higher than 18? C., in particular higher than 200? C.; and wherein the epoxy resin extends into the intermediate layer, from the composite component towards the first layer, in a form of a number of volume portions which are mutually adjacent or interconnected at least in part, wherein the volume portions are configured as bubbles and have, in a region of the intermediate layer that is adjacent to the composite component, a diameter or a volume that is greater than in a region of the intermediate layer that is adjacent to the first layer; and a component connected to the connection element, wherein the component is welded to the first layer of the connection element.

20. The connection arrangement of claim 19, wherein the component is welded to the first layer of the connection element by friction welding.

21. The connection arrangement of claim 20, wherein the component is welded to the first layer of the connection element by circular vibration friction welding.

22. A connection arrangement comprising: a connection element comprising: a composite component comprising a cured epoxy resin: a first layer comprising a first thermoplastic polymer: an intermediate layer arranged between the composite component and the first layer and containing both the epoxy resin of the composite component and the first thermoplastic polymer of the first layer and a second layer comprising a second thermoplastic polymer arranged on the first layer; wherein the first thermoplastic polymer has a melting point, in particular a glass transition temperature, above a curing temperature of the epoxy resin, wherein the first thermoplastic polymer is soluble at a temperature of at least 150? C. in the epoxy resin used for producing the composite component; wherein the curing temperature of the epoxy resin is up to 180? C.; wherein the glass transition temperature of the first thermoplastic polymer is higher than 185? C., in particular higher than 200? C.; and wherein the epoxy resin extends into the intermediate layer, from the composite component towards the first layer, in a form of a number of volume portions which are mutually adjacent or interconnected at least in part, wherein the volume portions are configured as bubbles and have, in a region of the intermediate layer that is adjacent to the composite component, a diameter or a volume that is greater than in a region of the intermediate layer that is adjacent to the first layer; and a component connected to the connection element, wherein the component is welded to the second layer of the connection element.

23. The connection arrangement of claim 22, wherein the component is welded to the second layer of the connection element by friction welding.

24. The connection arrangement of claim 23, wherein the component is welded to the second layer of the connection element by circular vibration friction welding.

25. A method for manufacturing a connection element, the method comprising: providing a raw composite component comprising at least one uncured epoxy resin; applying a first layer comprising a first thermoplastic polymer to the raw composite component, the first thermoplastic polymer having a melting point, in particular a glass transition temperature, above a curing temperature of the epoxy resin; and curing the raw composite component at a temperature of at least 150? C., the first thermoplastic polymer dissolving at a temperature of at least 150? C. in the at least one uncured epoxy resin, wherein the curing temperature of the epoxy resin is up to 180? C., and wherein the glass transition temperature of the first thermoplastic polymer is higher than 185? C., in particular higher than 200? C.

26. A method for producing a connection arrangement, the method comprising: providing a connection element comprising: a composite component comprising a cured epoxy resin: a first layer comprising a first thermoplastic polymer: an intermediate layer arranged between the composite component and the first layer and containing both the epoxy resin of the composite component and the first thermoplastic polymer of the first layer wherein the first thermoplastic polymer has a melting point, in particular a glass transition temperature, above a curing temperature of the epoxy resin; wherein the first thermoplastic polymer is soluble at a temperature of at least 150? C. in the epoxy resin used for producing the composite component; wherein the curing temperature of the epoxy resin is up to 180? C., and wherein the glass transition temperature of the first thermoplastic polymer is higher than 185? C., in particular higher than 200? C. and welding a component, which is configured to be connected to the connection element, to the first layer of the connection element by friction welding.

27. The method of claim 26, wherein the friction welding is implemented in a form of vibration friction welding.

28. The method of claim 27, wherein the vibration friction welding is implemented in a form of circular vibration friction welding.

29. A method for producing a connection arrangement, the method comprising: providing a connection element comprising: a composite component comprising a cured epoxy resin; a first layer comprising a first thermoplastic polymer; an intermediate layer arranged between the composite component and the first layer and containing both the epoxy resin of the composite component and the first thermoplastic polymer of the first layer; and a second layer comprising a second thermoplastic polymer arranged on the first layer; wherein the first thermoplastic polymer has a melting point, in particular glass transition temperature, above a curing temperature of the epoxy resin; wherein the first thermoplastic polymer is soluble at a temperature of at least 150? C. in the epoxy resin used for producing the composite component; wherein the curing temperature of the epoxy resin is up to 180? C.; and wherein the glass transition temperature of the first thermoplastic polymer is higher than 185? C., in particular higher than 200? C.; and welding a component, which is configured to be connected to the connection element, to the second layer of the connection element by friction welding.

30. The method of claim 29, wherein the friction welding is implemented in a form of vibration friction welding.

31. The method of claim 30, wherein the vibration friction welding is implemented in a form of circular vibration friction welding.

32. A method for producing a connection arrangement comprising: providing a connection element produced by a method comprising: providing a raw composite component comprising at least one uncured epoxy resin; applying a first layer comprising a first thermoplastic polymer to the raw composite component, the first thermoplastic polymer having a melting point, in particular glass transition temperature, above a curing temperature of the epoxy resin; and curing the raw composite component at a temperature of at least 150? C., the first thermoplastic polymer dissolving at a temperature of at least 150? C. in the at least one uncured epoxy resin; wherein the curing temperature of the epoxy resin is up to 180? C.; and wherein the glass transition temperature of the first thermoplastic polymer is higher than 185? C., in particular higher than 200? C.; and welding a component, which is configured to be connected to the connection element, to the first layer of the connection element by friction welding.

33. The method of claim 32, wherein the friction welding is implemented in a form of vibration friction welding.

34. The method of claim 33, wherein the vibration friction welding is implemented in a form of circular vibration friction welding.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic sketch of the structure of a connection of a composite component to a thermoplastic layer comprising the intermediate layer/mixing zone of thermoplastic and epoxy, after curing;

(3) FIG. 2A is a scanning electron microscope image of an etched cross section polish of a mixing zone;

(4) FIG. 2B is an enlarged view of the cross section polish of FIG. 2A in the region of the intermediate layer;

(5) FIG. 2C is an additionally enlarged view of the cross section polish of FIG. 2B;

(6) FIG. 3A is an FTIR spectrum of an example epoxy resin;

(7) FIG. 3B is an FTIR spectrum of an example intermediate layer;

(8) FIG. 3C is an FTIR spectrum of an example first thermoplastic polymer;

(9) FIG. 4A is a schematic perspective view of a raw composite component and a first layer;

(10) FIG. 4B is a schematic perspective view of an example connection element according to the disclosure herein, for example a thermoplastic/EP (epoxy resin) CFRP composite;

(11) FIG. 5 shows an example pressure and temperature cycle for producing a connection element in an autoclave;

(12) FIG. 6 is a perspective drawing of an example connection arrangement;

(13) FIG. 7 is a schematic drawing of the movement sequence of a component during circular vibration friction welding;

(14) FIG. 8 is a schematic side view of an example connection arrangement;

(15) FIG. 9 shows a temperature progression over time during the circular friction welding of a component to the connection element;

(16) FIG. 10 is a light microscope image of an etched cross section polish of an example connection arrangement;

(17) FIG. 11 is a schematic drawing of an example connection element comprising a first and a second layer;

(18) FIG. 12A is a schematic view of two connection elements according to FIG. 11 to be connected; and

(19) FIG. 12B shows the connection elements of FIG. 12A when connected.

(20) In the drawings, unless otherwise specified, like reference numerals denote like or functionally equivalent components.

DETAILED DESCRIPTION

(21) FIG. 1 is a schematic sketch of the structure of a connection of a composite component to a thermoplastic layer comprising the intermediate layer/mixing zone of thermoplastic and epoxy, after curing.

(22) The connection element 1 comprises a composite component 2, a first layer 4 and an intermediate layer 6.

(23) The composite component 2 comprises a cured epoxy resin 3 and a further material 13. The further material 13 may for example be carbon fibers. In this case, the composite component is a carbon-fiber-reinforced plastics material component.

(24) The first layer 4 comprises a first thermoplastic polymer 5 having a melting point above the curing temperature of the epoxy resin 3. In particular, the first layer 4 contains a polyetherimide as the first thermoplastic polymer 5. Alternatively or additionally, the first layer may for example also contain polysulphone, polyphenylsulphone, polyhydroxyether and/or polycarbonate. In some embodiments, the first layer 4 comprises or consists at least predominantly of polyetherimide.

(25) The intermediate layer 6 is arranged between the composite component 2 and the first layer 4. It contains both the cured epoxy resin 3 of the composite component 2 and the first thermoplastic polymer 5 of the first layer 4.

(26) The intermediate layer 6 has a measurable thickness 11 and a continuous concentration transition from the epoxy resin 3 to the first thermoplastic polymer 5. This continuous concentration transition is implemented in that the epoxy resin 3 extends into the intermediate layer 6 from the composite component 2 towards the first layer 4 in the form of a number of mutually adjacent volume portions 12 which are interconnected in part. The volume portions 12 have a larger diameter and a larger volume in a region of the intermediate layer 6 adjacent to the composite component 2 than in a region of the intermediate layer 6 adjacent to the first layer 4.

(27) Additionally, for example small bubbles 15 comprising thermoplastic material are provided diffused into the epoxy resin 3 of the composite component 2. This can result in a thickness 10 of the total concentration transition which is greater than the thickness of the intermediate layer 6 formed with the volume portions 12.

(28) FIG. 2A shows a scanning electron microscope image of an etched cross section polish of an example connection element 1.

(29) To produce the sample prepared in this manner, an appropriate sample was initially cut and polished. To etch the sample, a durable, fluff-free cloth was soaked with DCM (dichloromethane) and wiped over the polished sample once or twice. A tear 14 visible in the microscope image is a result of the etching (an artefact).

(30) It can be seen here that the intermediate layer 6 is formed between the composite component 2 and the first layer 4.

(31) It can further be seen that the composite component is passed through by a number of carbon fibers 13.

(32) FIG. 2B is an enlarged view of the cross section polish of FIG. 2 in the region of the intermediate layer 6.

(33) The distribution of the different-size bubble-shaped volume portions 12, having greater diameters in a region of the intermediate layer 6 adjacent to the composite component 2 and smaller diameters in a region of the intermediate layer 6 adjacent to the first layer 4, can clearly be seen here in the intermediate layer 6. The larger diameters are in a range between 1 ?m and 20 ?m, whilst the smaller diameters are below 1 ?m.

(34) Additionally, the small thermoplastic bubbles 15 diffused into the epoxy resin 3, which have a diameter in the micrometre range, and the carbon fibers 13 contained in the epoxy resin 3 are visible here.

(35) FIG. 2C is an additionally enlarged view of the cross section polish of FIG. 2. This enlarged view shows the phasing out of the intermediate layer 6 in a region adjacent to the first layer 4.

(36) The volume portions 12 in the form of small bubbles are shown, and have a diameter less than 1 ?m in the region shown at the right edge of the picture, which is approximately in the centre of the intermediate layer. In the centre of the detail shown, the diameters are already less than 0.1 ?m or 100 nm. The size of the volume portions becomes continuously smaller and smaller until the first layer 4, and finally is formed small on the left half of the detail shown as far as the resolution limit of the scanning electron microscope. In particular, in a region not shown, the volume portions may become smaller as far as individual molecules of the epoxy resin.

(37) FIG. 3A shows an FTRI spectrum of an example epoxy resin. The spectrum is recorded using an FTIR microscope suitable for spectral analysis.

(38) Here, the two relatively wide peaks of the spectrum (OH bands) shown on the left side of the graph are characteristic of the spectrum of the epoxy resin.

(39) FIG. 3C shows an FTIR spectrum of an example first thermoplastic polymer. This spectrum has no peaks on the left side of the graph, but has three characteristic peaks on the right side (at approximately 1700 cm.sup.?1).

(40) FIG. 3B shows an FTIR spectrum of an example intermediate layer. The spectrum detected in this case has the two peaks as per the left side of the graph of FIG. 3A for the epoxy resin as well as the three peaks as per the right side of the of FIG. 3C for thermoplastic polymer. It is thus evident that both the epoxy resin and thermoplastic polymer are present in the intermediate layer.

(41) In preliminary experiments, different thermoplastic polymers were evaluated in the first layer using a G1c test. This gave the following advantageous polymers: polyetherimide, polysulphone, polyphenylsulphone, polyhydroxyether and polycarbonate.

(42) In the G1c test, the mode 1 energy release rate (G1c) or the energy required for tear propagation [J/m.sup.2] is measured on a prepared sample, for example in accordance with ASTM D 5528-01 or DIN EN 6033. A percentage variation ?G1c in the energy release rate for samples comprising different thermoplastic polymers in the first layer may for example be referenced to an unmodified CFRP material (0% variation).

(43) As a result of the analysis, in exemplary embodiments the first thermoplastic polymer is selected from at least one of a group consisting of polyetherimide, polysulphone, polyphenylsulphone, polyhydroxyether and polycarbonate. For these materials, it can be seen from the G1c test that the energy release rate of the intermediate layer is increased by comparison with the unmodified CFRP.

(44) Particularly, polyetherimide (PEI) may be used as the first thermoplastic polymer. On the one hand, the highest energy release rates are achieved therewith in the G1c test, indicating a high mechanical load-bearing capacity and quality of the connection of the composite component to the first layer by way of the intermediate layer. On the other hand, polyetherimide usually has a high melting point or glass transition temperature, for example in particular of 217? C. according to ISO 11357. Polyetherimides are thus a high-temperature thermoplastic which is soluble in the epoxy resin.

(45) Aside from the stated group, a construction of the first layer comprising further thermoplastic polymers is also possible, although lower energy release rates as measurable by the G1c test are achieved. Thus for example polyethersulphone, polyphenylsulphone and/or polyamide are also conceivable as the first thermoplastic polymer.

(46) FIG. 4A is a schematic perspective view of a raw composite component 2 and a first 4.

(47) The first layer 4 is for example formed as a polyetherimide layer having a thickness 7 in a range of greater than 50 ?m to less than or equal to 300 ?m, in some embodiments in the range between 100 ?m and 150 ?m. In the state shown, the first layer 4 has not yet been applied to the raw composite component 2.

(48) The raw composite component 2 comprises for example a carbon fiber lattice and an uncured epoxy resin.

(49) To produce the connection element 1, the first layer 4 is applied externally to the raw composite component 2. Subsequently, the raw composite component 2 is cured at a temperature above 150? C. at least at times.

(50) FIG. 4B is a schematic perspective view of a connection element 1.

(51) In the curing process, the polyetherimide dissolves in the as yet uncured epoxy resin at high temperatures from 150? C. upwards. When the epoxy resin cures completely, the polyetherimide subsequently precipitates out again, resulting in the intermediate layer 6. The first layer 4 is thus firmly connected to the composite component 2 via the intermediate layer 6 after curing.

(52) A weldable portion, which can be used for attachment to a further material or a further component, is created externally on the composite component 2 using the first layer 4.

(53) FIG. 5 shows an example pressure and temperature cycle for producing a connection element 1 in an autoclave. For other materials, autoclave-free processes (RTM, VAP etc.) are also possible.

(54) This is a purely exemplary cycle, usually used for curing raw composite components containing a carbon fiber lattice and an epoxy resin, shown in a pressure-temperature diagram. Temperatures above 150? C. are sometimes operated in the autoclave. For different materials, other very difficult cycles may be required (autoclave, RTM, VAP etc.). The curing process is sometimes also adapted in a component-specific manner.

(55) At the start of the cycle, a vacuum is initially generated in a component cavity sealed off from the interior of the autoclave. The progression of the vacuum is shown by the curve V in the diagram. Subsequently, in the autoclave, the pressure P, likewise shown with its own curve, is increased to an operating pressure, for example of 7 bar. Starting from a particular pressure P of for example 1 bar in the autoclave, the vacuum V of the component cavity is reduced, for example to 0.2 bar. In parallel with the increase in the pressure P in the autoclave, a temperature T, likewise represented by its own curve, is increased with a predetermined growth, for example 1 to 3? C. per minute, to a first temperature, for example approximately 110? C. The first temperature is maintained for a first duration, for example approximately 60 minutes. Subsequently, the temperature T is further increased at the increase rate of the predetermined growth to a second temperature, for example approximately 180? C. This second temperature is maintained for a second duration, for example approximately 120 minutes. Subsequently, the temperature T is continuously lowered at a predetermined decrease rate, for example at 2 to 5? C. per minute, to a third temperature, for example 60? C. To end the cycle, the pressure is released from the autoclave.

(56) The temperature specifications on the cycle may for example be subject to a tolerance of ?5? C. The time specifications are for example subject to a tolerance of ?5 minutes.

(57) FIG. 6 is a perspective drawing of a connection arrangement 100.

(58) The connection arrangement 100 contains the connection element 1 of FIG. 4B comprising the composite component 2 and the first layer 4 connected thereto via an intermediate layer 6 and containing a first thermoplastic polymer, for example polyetherimide.

(59) Further, the connection arrangement 100 comprises a component 101 to be connected to the composite component 2. This may for example be a composite material attachment part. Other constructions of the component 101 are equally possible.

(60) The component 101 has an attachment region 102 and a foot portion 103. The attachment region 102 comprises for example a screw thread and serves to connect the connection arrangement to another structure or component by screwing. Other constructions of the connection region 102 are also possible.

(61) The foot portion 103 of the component 101 is welded to the first layer 4 of the connection element by friction welding. In a some embodiments, the method of circular vibration friction welding is used for the friction welding.

(62) FIG. 7 is a schematic drawing of the movement sequence of a component during circular vibration welding.

(63) In circulator vibration friction welding, the supply of energy is introduced by a relative movement of the joining parts to be connected by a circular oscillation movement. This is illustrated here by the component 101 shown in dashed lines in different positions on a circular path and the circular arrow representing the circular movement.

(64) During the circular oscillation movement, either only one of the parts to be welded or alternatively both parts to be welded may move. The parts do not rotate relative to one another, but merely move on a circular path. The circular vibration friction welding is commonly also known as orbital friction welding.

(65) In the illustration shown, the component 101 moves along the circular oscillation movement without rotating, as can be seen from the position of the groove 104 on the left edge of the foot portion 103 of the component 101.

(66) Advantageously, the limitations of conventional rotational friction welding, in which only approximately rotationally symmetrical components can be welded, are not present in circular vibration friction welding. Thus, unlike in rotational friction welding, the components do not have to be rotationally symmetrical in circular vibration friction welding, but may be of any desired shape.

(67) As a further advantage over rotational friction, in which the relative speed of a point on the surface is dependent on the diameter of the component, there is no such dependency in circular vibration friction welding. Instead, the speed of a point is merely dependent on the circular path of the circular movement, all points of the faces to be welded moving at the same speed. Thus, particularly uniform introduction of energy is achieved.

(68) FIG. 8 is a schematic side view of a connection arrangement 100.

(69) The arrangement can be produced by welding the component 101 to the first layer 4 of the connection element 1 by circular vibration friction welding, in particular using a stationary circular welding system.

(70) The friction welding of the connection arrangement 100 can be seen from the outside as a result of the friction weld flash 105 which typically occurs in circular vibration friction welding.

(71) The friction weld flash 105 predominantly contains thermoplastic polymer material of the first layer 4 of the connection element 1. The formation of the friction weld flash 105 brings about the advantage that impurities are also expelled from the weld zone together with the friction weld flash. It is therefore not necessary to clean the surfaces of the first layer and the component to be connected in advance. As a further advantage, as a result of the friction weld flash 105, any bumps or curvatures in the surfaces to be welded of the first layer and the component to be connected are levelled or evened out, ensuring a continuous welded connection between the connection element 1 and the component 101.

(72) The first layer 4 of the connection element 1 is therefore of a thickness 7 which makes possible the friction weld flash 105 required for the welding.

(73) If the composite component 2 has a curvature, the surface of the first layer is also curved in a corresponding manner. In this case, the thickness of the first layer 4 has to be matched to the curvature so as to ensure complete welding of the foot portion 103 of the component 101 to the connection element 1.

(74) FIG. 9 shows a temperature progression over time during the circular vibration friction welding of a component to the connection element.

(75) Here, the temperature TW is plotted against time during the circular vibration friction welding for welding the component 101 at various locations within the connection element 1.

(76) For this purpose, a component 101 formed as shown in FIGS. 6 to 8 was welded to a planar connection element 1 which has a first layer 4.

(77) The curve TW 1 qualitatively shows a temperature progression in a region below the first layer 4 or in the region of the intermediate layer 6 at an edge region of the joining zone. Maximum temperatures of for example less than 250? C. are reached here. Above a curing temperature TH of the epoxy resin, the temperature progression only moves for a short period of a few seconds, which is for example less than 5 seconds including heating to the maximum and cooling.

(78) The curve TW 2 shows the temperature progression in a region below the first layer 4 in the centre of the joining zone. In this case, there is a maximum temperature in the range of the curing temperature TH of the epoxy resin.

(79) The curve TW 3 shows the temperature progression in the composite component 2 between a first and a second fiber layer of the fiber lattice of the composite component 2. Here, the temperature is always less than the curing temperature TH of the epoxy resin throughout the welding process.

(80) Thus, in the region of the intermediate layer 6, a temperature above the curing temperature TH of the epoxy resin is only reached at the edge of the joining zone and only briefly. Advantageously, as a result of the local introduction of heat, the welding process therefore takes place externally on the first layer 4 in a manner which keeps the temperature sufficiently low in the epoxy resin 3 of the composite component that this does not cause damage to or degradation of the epoxy resin.

(81) FIG. 10 is a light microscope image of an etched cross section polish of a connection arrangement 100.

(82) Here the sample has been prepared in a manner as described with reference to FIG. 2A.

(83) The connection arrangement 100 comprises the connection element 1 comprising the various portions of the composite component 2, the first layer 4 and the intermediate layer 6 formed in between.

(84) The component 101, here formed by way of example as a glass-fiber-reinforced component, is welded to the first layer 4 externally and therefore in a material connection thereto. The glass fibers 106 can be seen individually in the image.

(85) FIG. 11 is a schematic drawing of a connection element 1 comprising a first layer 4 and a second layer 8.

(86) Here, in addition to the composite component 2 and the first layer 4, the connection element 1 comprises a second layer 8 materially connected to the first layer 4. This contains a second thermoplastic polymer 9 different from the first thermoplastic polymer 5. By the second thermoplastic polymer 9 or the second layer 8, the surface properties of the connection element 1 can be influenced.

(87) For example, the second layer may contain polyetheretherketone as a second thermoplastic polymer. Alternatively or additionally, polyethersulphone, polyamide and/or polyphenylsulphone may for example also be contained in the second layer 8. Alternatively or additionally, further thermoplastic polymers may be comprised by the second layer.

(88) The second layer 8 may be formed for example so as to improve the chemical stability of the connection element. Further, the second layer 8 may also be formed so as to establish compatibility for welding a component of which the material is not compatible with the first thermoplastic polymer 5 or is less suitable for welding by comparison with the second thermoplastic polymer 9.

(89) Providing the second layer 8 is advantageous in particular if the properties thereof are desired, but the second thermoplastic polymer 9 of the second layer 8 does not itself dissolve in the epoxy resin 3 of the composite component 2. The first layer 4 comprising the first thermoplastic polymer 5 thus acts as an adhesion promoter between the epoxy resin 3 and the second layer 8.

(90) Further, the welding properties of the connection element 1 may also be influenced using the second layer 8. For example, the second layer 8 may contain a thermoplastic polymer 9 which has a lower-viscosity melt and/or a lower melting point than the first thermoplastic polymer 5, in such a way that a component 101 can be welded to the connection element 1 in a simpler manner. Further, in particular, in this way two connection elements 1, each formed using one of the composite components, can be welded together in a simpler manner to connect two composite components.

(91) For example, the first layer contains polyetherimide and has a thickness of 100 ?m, whilst the second layer contains polyetheretherketone and has a thickness of 125 ?m. The first layer thus provides attachment to the epoxy resin 3 of the composite component 2, the second layer acting as an outer functional layer.

(92) FIG. 12A is a schematic view of two connection elements according to FIG. 13 to be interconnected.

(93) Two connection elements 1 can be welded together well by way of the respective second layer 8, which here by way of example has better welding properties than the first layer 4.

(94) For welding the two connection elements 1, they are for example positioned with the respective second layers 8 thereof on top of one another in an overlap region. By friction welding, for example circular vibration friction welding, the two second layers 8 are subsequently interconnected over the entire area to form a shared second layer 8.

(95) FIG. 12B shows the connection elements of FIG. 12A in a connected state.

(96) The shared second layer 8 extends continuously over the overlap region of the two connection elements 1. Thus, a reliable connection between the two connection elements 1 is provided in a very simple manner. In particular, in this way the two composite components 2 containing epoxy resin are connected at a high strength in a simple manner by a reliable process.

(97) Although the present disclosure has been described herein by way of exemplary embodiments, it is not limited thereto, but can be modified in various ways.

(98) For example, further thermoplastic polymers beyond those mentioned in the embodiments or different configurations of the mentioned thermoplastic polymers as materials for the first or second layer are conceivable. Further, different epoxy resins from the epoxy resin mentioned in the embodiment are also conceivable for the composite component.

(99) The composite component need not necessarily be a carbon-fiber-reinforced component. It may equally be a glass-fiber-reinforced component or a different type of composite component comprising an epoxy resin component. Further, it may also be a sandwich structure, at least a cover layer of the sandwich structure including the epoxy resin.

(100) 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.