Method for producing a material composite composed of metal and plastic to form a plastic-metal hybrid component

Abstract

The invention relates to a method for producing a material composite composed of metal and plastic to form a plastic-metal hybrid component, in which method, to improve the adhesion of the metal surface and at least one plastic component, stochastically random macroscopic and/or microscopic undercuts are made by means of short-pulse laser radiation in the metal surface in order to roughen it, these undercuts each being filled at least partially with the at least one plastic component in an injection moulding process such that said plastic component engages into the macroscopic and/or microscopic undercuts, wherein, following the roughening of the metal surface and before and/or during the injection moulding process for the at least one plastic component, at least the roughened surface of the metal is heated to a temperature which, during processing, lies in the range of room temperature up to 100 C. above the processing temperature of the plastic.

Claims

1. A method for producing a material composite composed of metal and plastic to form a plastic-metal hybrid component, wherein, to improve the adhesion of the metal surface and at least one plastic component, macroscopic undercuts with microscopic undercuts having stochastically random roughness shapes are introduced by means of short-pulse laser radiation into the metal surface in order to roughen it, said undercuts each being filled at least partially with the at least one plastic component in an injection moulding process, such that said plastic component engages in the random undercuts, wherein, following the roughening of the metal surface before and/or during the injection moulding process for the at least one plastic component, at least the roughened surface of the metal is heated to a temperature which, during processing, lies in the range from room temperature up to 100 C. above the processing temperature of the at least one plastic component, wherein the at least one plastic component is compounded with additives to increase its bonding strength to the roughened and heated metal surface.

2. The method according to claim 1, wherein the temperature to which the roughened surface of the metal is heated lies in the range from 100 C. below up to the processing temperature of the at least one plastic component.

3. The method according to claim 1, wherein the heating of the roughened metal surface of the metal takes place to a temperature which is higher than the glass transition temperature.

4. The method according to claim 1, wherein the temperature to which at least the roughened metal surface of the metal is heated is selected dependent on parameters such as process duration, viscosity of the melt and fineness and depth of the roughening of the metal surface.

5. The method according to claim 1, wherein, to generate the macroscopic undercuts of the metal surface by means of the short-pulse laser radiation, use is made of a scanner with an adapted focal length of the scanner optics and a beam guide.

6. The method according to claim 5, wherein the scanner is continuously moved at a predetermined speed relative to the metal surface to be roughened and its movement is superimposed with an axial movement of a robot, wherein the scanner optics at the same time guides the laser beam in a continuous loop over the metal surface in its working field and a uniform roughening (structuring) is generated continuously with a continuous relative movement on the entire metal surface.

7. The method according to claim 1, wherein the heating of the metal takes place inside the injection moulding tool.

8. The method according to claim 1, wherein the heating of the metal takes place outside the injection moulding tool in a furnace.

9. The method according to claim 1, wherein the heating of the metal takes place inductively.

10. The method according to claim 1, wherein the heating of the metal takes place by variable temperature regulation.

11. The method according to claim 1, wherein the heating of the metal takes place by means of water, oil or gas in an internal high-pressure forming process.

12. The method according to claim 1, wherein thermoplastics are used for the at least one plastic component.

13. The method according to claim 12, wherein thermoplastic polymers such as polyamides, polyesters, polyacetals, polybutylene terephthalate and polyolefins such as polypropylene or polyethylene or mixtures thereof or polyamides such as polyamide 6 or polyamide 6.6 or polyphenylene oxide or polyether imide are selected as thermoplastics.

14. The method according to claim 1, wherein thermosetting plastics are used for the at least one plastic component.

15. The method according to claim 1, wherein elastomers or elastomer-like plastics are used for the at least one plastic component.

16. The method according to claim 1, wherein the injection moulding process with the at least one plastic component takes place under an at least partial vacuum.

17. The method according to claim 1, wherein the at least one plastic component is compounded with fillers and reinforcing materials.

18. The method according to claim 17, wherein, as fillers and reinforcing materials, use is made of those that reduce the length expansion coefficient of the at least one plastic component.

19. The method according to claim 1, wherein glass fibres, carbon fibres, aramide fibres or natural fibres of flax, hemp or sisal are used as fibres for reinforcing the at least one plastic component.

20. The method according to claim 19, wherein fibres with a fibre length of less than 1 mm or less than 0.4 mm or short glass fibres are used.

21. The method according to claim 19, wherein fibres with a fibre length in the range from 1 mm to 30 mm or long glass fibres are used.

22. The method according to claim 19, wherein, as reinforcing materials, use is made of polymer-based reinforcing systems such aramide fibres, which have a negative thermal expansion coefficient along the fibre orientation.

23. The method according to claim 1, wherein, when use is made of steel, aluminium or other metals and highly reinforced thermoplastic plastic is used as a plastic component, the roughened steel surface is heated before the injection moulding process with the highly reinforced thermoplastic plastic to a temperature in the range from 100 C. below up to melt temperature in processing.

24. The method according to claim 1, wherein an aluminium workpiece is used as the metal of the material composite, wherein, after roughening of the aluminium surface, the aluminium workpiece is formed under conditions of internal high pressure into an aluminium component before the injection moulding with the at least one plastic component and the arising forming heat of the aluminium is used for heating the roughened aluminium surface for the injection moulding process with the at least one plastic component, said process taking place directly in the same tool.

25. The method according to claim 1, wherein the production of the material composite of the plastic-metal hybrid component is simulated numerically depending on the process parameters: heating at least of the roughened surface of the metal to a temperature, process duration of the injection moulding, temperature-dependent viscosity of the melt and fineness and depth of the roughening (structuring) of the metal surface.

26. A method for producing a material composite composed of metal and plastic to form a plastic-metal hybrid component, wherein, to improve the adhesion of the metal surface and at least one plastic component, stochastically random macroscopic and/or microscopic undercuts are introduced by means of short-pulse laser radiation into the metal surface in order to roughen it, said undercuts each being filled at least partially with the at least one plastic component in an injection moulding process, such that said plastic component engages in the macroscopic and/or microscopic undercuts, wherein, following the roughening of the metal surface before and/or during the injection moulding process for the at least one plastic component, at least the roughened surface of the metal is heated to a temperature which, during processing, lies in the range from room temperature up to 100 C. above the processing temperature of the at least one plastic component, wherein the at least one plastic component is compounded with additives to increase its bonding strength to the roughened and heated metal surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is now explained by reference to the figures of the drawings. In these figures:

(2) FIG. 1 shows a microscopic representation of a structuring of the metal surface of a first metal-polymer composite,

(3) FIG. 2 shows a microscopic representation of a structuring of the metal surface of a second metal-polymer composite,

(4) FIG. 3 shows a REM image of the structuring of the metal surface,

(5) FIG. 4 shows a diagrammatic representation of a structuring of the metal surface of an aluminium/glass fibre-reinforced polymer composite,

(6) FIG. 5 shows a diagrammatic representation of a structuring of the metal surface of a metal/glass fibre-reinforced polyamide composite, wherein the unfilled regions are marked,

(7) FIG. 6 shows a diagrammatic representation of a structuring of the metal surface of a steel/glass fibre-reinforced polyamide composite,

(8) FIG. 7 shows an image of a test body of a plastic-aluminium hybrid component after a destructive test,

(9) FIG. 8 shows a diagrammatic representation of the optics of a scanner during its movement,

(10) FIG. 9 shows a diagrammatic representation of the scanner movement in the working field, and

(11) FIG. 10 shows a flow chart of an embodiment of the method according to the invention, from which the optimisation of the bonding strength of the plastic-metal hybrid component emerges.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(12) The invention is now explained by reference to the figures of the drawings. In the latter:

(13) FIGS. 1 and 2 each show a microscopic representation of a laser structuring of the metal surface of a first and second metal-polymer composite to be produced in each case with varying spacings and depths of the laser structuring, which has been generated to prepare the jointing area of the respective metal-polymer composite. As a REM image according to FIG. 3 shows, the laser structuring is applied in a two-dimensionally extending manner onto metal surface 3 for its roughening, wherein the size of the area is dimensioned according to the forces to be transferred by the respective metal-polymer composite to be produced. The laser structuring takes place by means of short-pulse laser radiation, whereinas can clearly be seen from FIGS. 1 to 3stochastically random macroscopic and/or microscopic undercuts are introduced into the metal surface in order to roughen the metal surface. During the jointing of the metal-polymer composite in an injection moulding process, the macroscopic and/or microscopic undercuts are at least partially filled with the polymer component, in such a way that an engagement of the latter in the macroscopic and/or microscopic undercuts takes place for the marked improvement in adhesion of the metal surface and the polymer component.

(14) A CT cross-sectional image of the jointing area of an aluminium/glass fibre-reinforced polyamide composite can be seen in FIG. 4, wherein the aluminium with the laser-structured surface and the undercuts and the glass fibre-reinforced polyamide material, with which the undercuts are filled, are represented above. Since the laser structuring of the aluminium surface cannot be fully ventilated during the injection moulding process, small unfilled residual parts remain (shown dark in the representation), which however can be avoided by the use of a partially evacuated injection moulding tool.

(15) FIG. 5 shows a detail image of the jointing area of a steel/glass fibre-reinforced polyamide composite, wherein the metal is marked dark at the bottom, the polyamide medium grey at the top, the glass fibres in the latter in bright grey and the regions of the metal/glass fibre-reinforced polyamide composite not filled with glass fibre-reinforced polyamide in white. Here too, before the jointing of the metal/glass fibre-reinforced polyamide composite in the injection moulding process, stochastically random macroscopic and/or microscopic undercuts are introduced by means of short-pulse laser radiation into the metal surface in order to roughen it. In order to reinforce the polyamide, use may be made of short fibres with a length of 1-2 mm before the injection moulding process and/or long glass fibres with lengths up to 30 mm before the injection moulding process. With the aid of a partially evacuated injection moulding tool, complete filling of the laser structuring of the roughened metal surface with the glass fibre-reinforced polyamide can be achieved, so that a very high load-bearing capacity of the metal/glass fibre-reinforced polyamide composite is ensured.

(16) Complete filling of the laser structuring of the roughened metal surface with the glass fibre-reinforced polyamide can be achieved with the aid of a partially evacuated injection moulding tool, so that a very high load-bearing capacity of the metal/glass fibre-reinforced polyamide composite is ensured.

(17) In a similar way, FIG. 6 shows a detail image of the jointing area of a steel/glass fibre-reinforced polyamide composite, wherein steel is shown below and the glass fibre-reinforced polyamide material above and the undercuts of the laser-structured steel surface filled by the latter are represented. For the filling of the undercuts and the cavities of the laser-structured steel surface in the injection moulding process, it is necessary to prevent premature setting of the plastic material, especially when use is made of highly viscous plastics. It is therefore necessary to heat, e.g. by induction, the steel surface roughened by means of short-pulse radiation before the jointing process or during the jointing process.

(18) For example, a temperature of the steel of approx. 250 C. has been shown to be very well suited in a combination of steel with highly reinforced polyamide 66, wherein the temperature can lie approx. 50 lower or 30 C. higher depending on the type of the polyamide used, such as for example suitable for high temperatures, crash-resistant etc.

(19) FIG. 7 shows a photographic image of a plastic-metal hybrid component as a test body after a destructive test, wherein the base width of 5 mm of the plastic component can be seen on a metal plate measuring 40 mm70 mm. If, for example, an internal high-pressure formed aluminium component is to be connected to a plastic component, the forming heat of the aluminium can be used in an integrated jointing process, so that there is no need for additional heating thereof before the jointing.

(20) In connection with the test body, it has been shown that the fillers and reinforcing materials of the plastic components used, which by their nature can penetrate into the cavities of the laser-structured metal surface, can contribute to an improved force transfer in the proximity of the interface of the composite.

(21) In order to prevent corrosion of the jointing area of the plastic-metal hybrid component, a frame of elastomer material surrounding the jointing area can first be injected when use is made of a two-component injection moulding process, after which the thermoplastic or thermosetting plastic component is deposited directly onto the laser-structured metal surface of the jointing area, by means of which a composite stable under load is produced. Alternatively, the elastomer frame can also be deposited, following the production of the composite, around the latter by means of a suitable process such as for example injection moulding for the purpose of sealing.

(22) A diagrammatic representation of the optics of a scanner during its movement emerges from FIG. 8, said scanner being used with an adapted focal length of the scanner optics and a beam guide for the stochastically random introduction of the macroscopic and/or microscopic undercuts in the metal surface for the roughening thereof by means of short-pulse laser radiation.

(23) The mechanical structure of scanner optics 1 as such is known. According to the method according to the invention, scanner 2 is moved continuously at a predetermined speed (arrow v) relative to metal surface 3 to be roughened, wherein its movement is at the same time superimposed with an axial movement of a robot (not shown). Scanner optics 1 guides laser beam 4 in a continuous loop over the metal surface in its working field (x, y) 5, wherein a uniform stochastic roughening (structuring) is continuously generated with continuous relative movement on the entire metal surface to be structured.

(24) As can be seen from FIG. 8, a laser beam 4 emitted from a laser light cable 6 of scanner optics 1 is guided via a collimator 7, the laser optics and a deflection mirror 8 disposed downstream of the latter in the beam direction to a galvanometer scanner system comprising an X-axis scanner 9 and a y-axis scanner 10 and is deflected from the latter via a plane field lens 11 disposed downstream in the beam guide onto the working field of the metal surface to be structured. When scanner optics 1 is installed on a robot arm, the jointing area to be roughened can be moved away with the aid of a spacing control.

(25) FIG. 9 illustrates that the scanner optics performs a predetermined relative movement with respect to the workpiece surface to be structured, wherein, as emerges from FIG. 9, the scanner optics guides the laser beam in a continuous loop over a closed structure of the workpiece surface in its working field (x, y). By the superimposition of the two movements, targeted stochastic structural shapes of the metal surface to be structured, which are matched to the subsequent loading direction, can be generated with different depths. The shape and the depth of the generated laser structuring can be defined by changing the guidance (shape) and/or the speed of the beam movement and simultaneous adaptation of the laser parameters such as for example power and/or repetition rate. Depths of the structuring of several 100 m up to 1 mm are possible. The adaptation of the injection moulding process to the nature of the jointing partner and the specified loading profile is thus possible.

(26) FIG. 10 illustrates the possibilities of an optimisation of the bonding strength of a material composite composed of metal and plastic to be produced according to the invention to form a plastic-metal hybrid component. According to test specifications of a testing station (block A) of the material composite to be produced, a change in the metal structuring (block B) as well as a modification of the used plastic granulate (block C) of the respective corresponding jointing partner, metal or plastic component, is possible by means of a respective so-called external optimisation (directional arrow I and II). Furthermore, according to the test specifications of the material composite to be produced (block A), after introduction (directional arrow III) of the metal component with the laser-structured surface (block B) into an injection moulding tool (block D) for its heating (block E) inside the latter, and after introduction (directional arrow IV) of the plastic granulate (block C) into the injection moulding tool (block D) for the purpose of producing a melt (block F) of the plastic granulate before the jointing of the two jointing partners in an injection moulding process (block G), a change in the metal temperature (directional arrow V) or a change to the melt temperature (directional arrow VI) is possible by way of a respective internal corresponding optimisation, so that the injection moulding process (block G) is initiated after inputting optimised values from the heating of the metal component (directional arrow VII) and from the melt of the plastic component (directional arrow VIII) and the material composite is produced with an optimised bonding strength, said material composite being removed from the injection moulding tool (block D) and fed once again (directional arrow IX) to the testing station (block A).

LIST OF REFERENCES NUMBERS

(27) 1 scanner optics 2 scanner, galvanometer scanner 3 metal surface to be roughened 4 laser beam 5 working field of the scanner optics 6 laser light cable 7 collimator 8 deflection mirror 9 X-axis scanner 10 Y-axis scanner 11 plane field lens v arrow for the speed of the scanner Block A testing station of the workpiece composite to be produced Block B change in the metal structuring Block C change in the plastic granulate Block D injection moulding tool Block E heating Block F melt Block G injection moulding process Arrow I external optimisation of the change in the metal structuring Arrow II external optimisation of the change in the plastic granulate Arrow III introduction of the metal component with a laser-structured surface into the injection moulding tool Arrow IV introduction of the plastic granulate into the injection moulding tool Arrow V change in the metal temperature Arrow VI change in the melt temperature Arrow VII internal optimisation of the heating of the metal component Arrow VIII internal optimisation of the change in the melt temperature Arrow IX feeding of the material composite to testing station A