HYBRID COMPOSITE MATERIAL BETWEEN A METAL SURFACE AND A POLYMERIC MATERIAL SURFACE AND PROCESS FOR PRODUCING THE HYBRID COMPOSITE MATERIAL

Abstract

The invention is a hybrid composite material between a first joining partner having a metal surface and a second joining partner having a polymeric material surface. A process for producing a hybrid composite material associated therewith is also described. The hybrid composite material according to the invention is characterized in that the metal surface has microstructured depressions, having a diameter and a structure depth in the micrometer range, the microstructured depressions have metallic surface regions which are furnished entirely with nanostructures, the structure dimensions of which are in the nanometer range, the microstructured depressions are blind holes or throughhole openings fully passing through the first joining partner.

Claims

1. A method for producing a hybrid composite material between a metal surface and a polymeric material surface, comprising: structuring the metal surface with a laser pulse beam having a pulse duration in picoseconds or femtoseconds to produce microstructured depressions extending into the metal surface and each including metallic surfaces including microstructures and nanostructures, the microstructured depressions include one of blind holes or throughhole openings passing through the metal surface and have a thickness to diameter ratio of not less than 5, wherein the nanostructures cover the microstructured depressions; applying polymeric material to the structured metal surface by coating at least part of the metal surface of the metal surface having nanostructures using flowable polymeric material; and solidifying the polymeric material and forming at least one joining connection based on at least one of adhesion and covalent bonds between the solidified polymeric material and microstructured and nanostructured metal surface regions.

2. The method according to claim 1, comprising: focusing a laser beam on the metal surface, deflecting the laser beam laterally so that micromelts are formed at each site on the metal surface, which partially vaporize and subsequently solidify to form microcavities; and directing the laser beam at least once at each microcavity of forming a micromelt with metal vaporization in the microcavity.

3. The method according to claim 2, comprising: directing at least one laser beam on a solidified microcavity so that the laser beam is absorbed at a bottom of the microcavity to cause a metal melt to form which rises up walls of the microcavity and solidifies.

4. The method according to claim 2, comprising: applying a one laser beam at least once to a solidified microcavity so that the laser beam is absorbed at the bottom of the microcavity at which metal is vaporized to form a metal vapor which rises and recondenses on the walls of the microcavity.

5. The method according to claim 2, comprising: applying the laser beam at a surface of a joining partner so that plasmons are excited at least one of thermal, electronic and metallurgical surface tensions are formed which interact with an irradiation field of the laser beam to form the nanostructures.

6. The method according to claim 2, comprising: applying polymeric material of another joining partner including a thermoplastic material to the structured metal surface by pressing the joining partners together under pressure; converting the thermoplastic material of one joining partner into flowable form by application of heat so that the flowable thermoplastic material fills the microstructures and at least partially coats nanostructures on the metallic surface regions of one of the joining partners; and forming that the hybrid composite material by cooling and solidification of the thermoplastic material.

7. The method according to claim 1, comprising: applying polymeric material in a form of the another joining partner comprising a thermosetting material by coating and filling the structured metal surface with the thermosetting material in a flowable state; and forming the hybrid composite material by solidification of the thermosetting material.

8. The method according to claim 1, comprising: using the first joining partner with a previously prepared structured metal surface as an integral component to manufacturing a plastic component comprising a thermoplastic material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In the following text, the invention will be described without limitation of the general inventive thought on the basis of exemplary embodiments thereof and with reference to the drawing. In the drawings:

[0038] FIG. 1 is a representation of the superimposed micro- and nanostructures for joining a plastic with a metal surface, and

[0039] FIGS. 2a, b show scanning electron microscope images of a prestructured metal surface

WAYS TO IMPLEMENT THE INVENTION, COMMERCIAL APPLICABILITY

[0040] FIG. 1 represents a highly simplified hybrid joint between a first joining partner 1 having a metal surface 2 and a second joining partner 3 made from polymeric material. The metal surface 2 of the first joining partner 1 is furnished with microstructured depressions 4, whose maximum diameter d and structure depths S have dimensions between 1 μm and 1000 μm. The microstructured depressions 4 have microstructures M and nanostructures N represented in FIG. 1 on their inner walls 5, which are not illustrated in FIG. 1 and are illustrated in FIG. 2 corresponding to the metallic surface regions assigned to the microstructured depressions 4. The nanostructures N are superimposed over the microstructures M along the microstructured metallic surface regions 5.

[0041] The combination of microstructures M and nanostructures N may be seen in the scanning electron microscope image illustrated in FIG. 2a, which shows a top view of a surface region 5 of the metal surface 2 of the first joining partner 1 structured with the micro and nanostructures M, N. FIG. 2b shows detail of the micro and nanostructured metal surface 2 of the first joining partner reduced in size by factor of 2.

[0042] The aforementioned repeated irradiation of the metal surface 2 with at least one of shorts pulse and ultra-short pulse laser beams leads to the formation of depressions 4 which are below the metal surface 2 and which have a depth-to-width ratio (s/d) of at least a factor of 5. At least the metallic surface regions 5 closest to the individual depressions 4 are furnished with nanostructures N, which are shown as pores or dents in high contrast in the image representation of FIG. 2a.

[0043] The multiple arrangement of depressions 4 disposed side by side creates conical protrusions 6, also called CLPs, Cone Like Protrusions, the surfaces of which are preferably completely covered with nanostructures N. The conical protrusions 6 are formed by medium-sized to high fluences and particularly with short to ultra-short laser pulses in the picosecond and femtosecond range of the laser irradiation.

[0044] When a metal surface made for example of steel which is processed with a laser beam, and which is exposed repeatedly to at least one of short pulse laser beams and ultra-short pulse laser beams. The formation of the microstructured depressions 4 are manifested as single black hole-like structures. Characteristic of the structure formation on a steel surface is a continuously progressive black coloration of the metal surface.

[0045] The nanostructures N which are created in addition to the microstructures M during irradiation with ultra-short pulse lasers causes the surface-volume ratio to be enlarged substantially compared with a metal surface that has only been furnished with microstructures, and the surface area is rendered significantly more reactive to at least one of specific adhesion and covalent bonding than a joining partner that has only been provided with microstructures, so that at least one of the adhesive, covalently binding and bonding effect between a plastic surface and a metal surface structured in such manner is increased substantially or is raised to a technically usable level.

[0046] The metal surface structured according to the invention fulfils the prerequisite for a hybrid composite material with a significantly higher bonding strength, which is based on at least one of the adhesive and covalent bonding forces between the nanostructured microstructures and a polymeric substance or material. Thus in the first instance the microstructures function to create form-fitting bonds which are known per se, for example in the form of mechanical clasping arrangements, which serve to enable inherent, powerful force transfer, while the nanostructures are able to generate surface adhesion forces between the metal surface and the polymeric surface. The nanostructures are able to influence the surface energy of the metal surface significantly without any additives or intermediate layers.

[0047] The embodiment illustrated in FIGS. 2a and b which show the structuring of a metal surface reflects a further advantageous property beside the combination according to the solution of micro- and nanostructures, that is to say the principle of arrangement of self-organizing microstructures in the form of the previously noted CLP conical protrusions 6, each of which form around immediately adjacent micro and nanostructured depressions 4. The application of at least one of short laser pulses and ultra-short laser pulses to the metal surface to be structured is preferably carried out in such manner that the self-organizing microstructures 6 are formed in largely even distribution over an area without any other processing intervention.

REFERENCE LIST

[0048] 1 First joining partner [0049] 2 Metal surface [0050] 3 Second joining partner [0051] 4 Microstructured depressions [0052] 5 Metallic surface region, inner wall of the microstructured depressions [0053] 6 Conical bodies, CLP [0054] M Microstructure [0055] N Nanostructure [0056] d Diameter [0057] s Structure depth