Method for joining two joining partners and workpiece composite produced according to the method

Abstract

The invention relates to a method for joining two components, in which, in a first step (1), a retaining structure (11) with an arrangement of recessed retaining elements (110) is incorporated into a joining surface of a first component (10) made of solid material, and in a second step (2), a layer of material that is flowable upon application and subsequently solidifies is applied as a second component (20), which penetrates the recessed retaining elements (110) and, after solidification, is held in place by the retaining structure (11), as well as to a workpiece composite produced according to the method. The retaining structure (11) is incorporated by means of waterjet cutting.

Description

[0001] The invention relates to a method for joining two joining partners, in which, in a first step, a retaining structure with an arrangement of recessed retaining elements is incorporated into a joining surface of a first joining partner made of solid material, and in a second step, a layer of material that is flowable during application and subsequently solidifies is applied as a second joining partner, which penetrates the recessed retaining elements and is held in place by the retaining structure after solidification, and to a workpiece composite produced according to the method.

[0002] A method for joining two components of this type is disclosed, for example, in DE 10 2014 008 815 A1. In this process, a composite material of metal and plastic is produced by roughening the metal surface with short-pulse laser radiation to improve adhesion. A plastic layer is then applied to the resulting holding structure, which features macroscopic and / or microscopic undercuts, using an injection molding process. This plastic layer is then held in the recessed retaining elements of the holding structure. A similar method and a composite material are disclosed in US 2022 / 0347938 A1, wherein the holding structure is incorporated into the metal surface of the first joining partner using ultrashort laser pulses and features micro- and nanostructures.

[0003] US patent 2021 / 0331448 A1 discloses a method for manufacturing a hybrid component from a metal component and a plastic component, in which an adhesive layer is applied to hold the plastic component on the metal component.

[0004] US Patent 2011 / 0123711 A1 presents a method for manufacturing a hybrid component from a metal and a polymer material, in which a polymer layer is first applied to the surface of an object such as a silicon wafer, a stainless steel part, nickel, or a nickel alloy, which has a microstructure. The polymer layer with this microstructure is then removed and coated with a thin metal layer using a deposition process.

[0005] Other methods for joining components using a structured surface include structuring by abrasion or etching, structuring by machining, additive processes, and structuring without addition or subtraction by electron beam structuring.

[0006] A summary of various other joining processes for joining partners such as metals and polymers can be found in the publication by Lambiase, F.; Scipioni, SI; Lee, CJ.; Ko, DC-; Liu, F.: A State-of-the-Art Review on Advanced Joining Process for Metal-Composite and Metal-Polymer Hybrid Structures. Materials 2021. DOI: 10.3390 / ma 14081890.

[0007] The aforementioned joining methods are subject to various limitations and associated disadvantages. For example, radiation-based methods, such as laser structuring, require pretreatment of the joining surfaces, and the structuring process leads to a change in the material's microstructure due to heat input. Other methods that introduce heat into the material can also influence its properties and, for example, lead to embrittlement. In some methods, the bond is limited to an intermediate layer. Joining methods using macroscopic form-fit techniques, such as machining or additive manufacturing, are limited to specific materials and geometries and are relatively expensive. Clinching requires a deformable material for joining. Other methods, such as riveting, require additional external joining elements. Still other methods, such as friction riveting, require high joining forces.

[0008] The present invention is based on the objective of providing a method for joining joining partners that results in the broadest possible applicability in the production of composite components, and of making composite components produced in this way available.

[0009] This problem is solved by a method having the features of claim 1 or by a composite component manufactured according to this method.

[0010] According to the invention, the holding structure is incorporated by means of water jet cutting in the method.

[0011] The insertion of the holding structure into the first joining partner by means of waterjet cutting can be applied to many different materials, whereby a wide variety of designs of the holding structure can be produced, which can be largely adapted to the material of the first joining partner and to the properties of the second joining partner.

[0012] Advantageous embodiments of the method include the fact that at least part of the retaining elements are incorporated obliquely at an angle of incision (α) between 10° and 80° with respect to the adjacent surface of the first joining partner, in particular between 20° and 70° and preferably between 30° and 60°.

[0013] Further advantageous adjustment options for achieving the best possible joint result from varying the cutting angle (α) along the depth profile of the respective retaining element. The inclined cutting angle relative to the surface creates undercuts perpendicular to the surface or the corresponding surface section, which result in particularly high pull-out forces perpendicular to the surface.

[0014] Furthermore, if adjacent retaining elements are directed towards each other or away from each other in their course in the depth direction, then in addition to high joining forces perpendicular to the surface, high joining forces or pull-off forces are also achieved in the lateral direction.

[0015] An advantageous match to the flowability of the second joining partner can be achieved by ensuring that the opening width of the holding elements is between 0.5 mm and 3 mm, in particular between 0.8 mm and 2 mm.

[0016] Further advantageous adjustment options depending on the material types of the first and / or the second joining partner result from the fact that the cutting depth of the holding elements in their depth direction lies between 1 mm and 15 mm, in particular between 2 mm and 10 mm.

[0017] Further advantageous coordination options regarding the properties of the joining partners consist of the fact that the retaining elements are designed as continuous or interrupted straight or wavy lines or circular or random lines when viewed from above on the surface of the first joining partner.

[0018] Various advantageous composite components can be provided by the fact that the first joining partner comprises at least one material from the material groups of electrically conductive or semiconducting materials, electrically non-conductive materials, thermally conductive materials, thermally insulating materials, transparent materials and opaque materials.

[0019] Further advantageous composite components for various applications can be provided by using a second joining partner that comprises a material from the groups of thermoplastic polymers, thermosetting polymers, elastomers, ceramics, and metallic materials, each with or without additives. Suitable additives or fillers, particularly for the plastic, include glass and carbon filaments, carbon nanotubes, metal powders, or ceramic powders, each with a filler content adapted to the intended application (e.g., between 20 and 80 vol%, or 30 and 60 vol%).

[0020] Advantageous variations of composite components also arise from the use of material particles in the form of short fibers or particles as additives, whose maximum expansion is less than the clear opening width of the retaining elements.

[0021] For the production of the holding structure, especially depending on the material of the first composite partner, an advantageous measure is to add abrasive particles to the water jet, such as garnet sand, olive sand and / or corundum.

[0022] The retaining structure or elements incorporated by waterjet cutting, in addition to their macroscopic geometry (opening width, depth, direction, course), also exhibit microscopic structures or roughness on their boundary surfaces. These contribute to increasing the bonding forces between the two joining partners by allowing the second partner to grip them with the injected material. Furthermore, closer examinations (e.g., in cross-sectional images) have shown that, depending on the material, the retaining elements do not always continue in a straight line in the depth direction, but rather change direction, thereby reducing the cutting angle with respect to the surface. This also allows the joining forces to be favorably influenced.

[0023] The invention is explained in more detail below using exemplary embodiments with reference to the drawing. The Fig. Figure 1 schematically shows three process steps in the joining of two joining partners using waterjet cutting.

[0024] In the first process step 1, a retaining structure 11 with retaining elements 110 is incorporated into a surface of the first joining partner 10 by means of a water jet device 30 (not fully shown). The retaining elements 110 are cut by means of a water jet 32 ​​or cutting jet formed by a jet nozzle 31, preferably not completely penetrating the first joining partner 10. To obtain a grippy retaining structure 11, the water jet 32 ​​is preferably supplied at a cutting angle α, which is, for example, between 10° and 80°, in particular between 20° and 70°, and preferably between 30° and 60° with respect to the surface, or, in the case of a curved surface, with respect to the tangent to the surface in the region of the inlet opening of the cut, recessed retaining element 110.In this way, several retaining elements 110 are incorporated into the surface of the first joining partner 10 as a retaining structure 11, wherein the retaining elements 110 are advantageously directed towards each other in the cross-section of the first joining partner 10, either converging towards each other in the depth direction, as shown in the illustration of process step 2, or moving away from each other, wherein several such retaining elements 110, which may also have different cutting angles α, cutting depths and / or opening widths b, can be arranged suitably distributed over the surface of the first joining partner 10 to achieve the most grippy retaining structure 11 possible.

[0025] In the second process step 2, a flowable material 20', for example a polymer material such as thermoplastic or thermoset plastic (thermoset), is applied over a surface area via a material feed nozzle 40 to the surface of the first joining partner 10, which is provided with the holding structure 11, in order to form the second joining partner 20, which subsequently solidifies. As shown in the middle illustration in Fig. Figure 1 shows that during this application process of the flowable material 20', a part penetrates the holding elements 110 as filling elements 21, so that the second joining partner 20 is held stably on the first joining partner 10 after solidification.

[0026] The lower representation of the Fig.Figure 1 shows the third process step 3 with the second joining partner 20 applied to the first joining partner 10, whereby the filling elements 21 have penetrated the retaining elements 110 of the retaining structure 11. Due to the retaining elements being oriented towards each other in the depth direction, undercuts result, which generate high holding forces and pull-off forces both perpendicular to the surface and in the lateral direction.

[0027] The retaining elements 110 of the retaining structure have, for example, a length in the depth direction or at the relevant inclination to the surface of the first joining partner 10 of, for example, between 1 mm and 15 mm, or between 2 mm and 10 mm, also depending on the material of the first joining partner 10 and / or the second joining partner 20. The opening width of the retaining elements is, for example, between 0.5 mm and 3 mm, or between 0.8 mm and 2 mm, also depending on one or both joining partners 10 or 20. Along the surface of the first joining partner 10, the retaining elements 110 can have different continuous or interrupted shapes, for example, wavy, rounded, jagged, or meandering, or the like, or they can run in a straight line, whereby high retaining forces are generated, particularly by their undercuts in the depth direction.The limiting side surfaces of the retaining elements 110 exhibit microscopic roughening as a result of the cutting processes, which contributes to increasing the joining forces. As investigations by the inventors have shown in cross-sectional images, the retaining elements 110 are usually not straight in the depth direction, but are often curved away from the surface normal, whereby such deformations are also material-dependent and can likewise contribute to improving the holding forces.

[0028] The waterjet cutting process allows for a wide variety of materials as the material for the first joining partner 10, including, for example, various metals, electrically non-conductive materials such as glass and non-conductive ceramics, thermally insulating or non-insulating materials, and the like.

[0029] Different materials can also be used for the joining partner, such as the aforementioned thermoplastic or thermosetting plastics, or other materials that are sufficiently flowable before application to penetrate the retaining elements 110 of the retaining structure 11 effectively during application and subsequently solidify to form the component composite of the first and second joining partners 10, 20. The second joining partner 20 can be provided with suitable additives, e.g., fibrous or particulate, with varying degrees of filler. The fiber particles or particles must be small enough to penetrate the retaining elements 110 without clogging them and thus preventing the penetration of the liquid material. Suitable additives include, for example, glass and carbon filaments, carbon nanotubes, and metal or ceramic powders.

[0030] To carry out the cutting process efficiently, suitable abrasive particles, such as garnet sand, olive sand or corundum, are added to the water jet, which are appropriately matched to the material of the first joining partner 10.

[0031] In an experimental investigation of the process, a holding structure consisting of two cuts with a cutting angle α of 45° to the surface of the first joining partner 10 and a depth of 1 mm was introduced into an aluminum sheet. The sheet was then overprinted with a layer of short carbon fiber-reinforced polyetheretherketone using SEAM (Screw Extrusion Additive Manufacturing). The process suitability was demonstrated by tensile shear tests. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2014 008 815 A1

[0002] US 2022 / 0347938 A1

[0002] US 2021 / 0331448 A1

[0003] US 2011 / 0123711 A1

[0004] Cited non-patent literature

[0000] Lambiase, F.; Scipioni, SI; Lee, C.J.; Ko, DC-; Liu, F.: A State-of-the-Art Review on Advanced Joining Process for Metal-Composite and Metal-Polymer Hybrid Structures. Materials 2021. DOI: 10.3390 / ma 14081890

[0006]

Claims

[1] Method for joining two joining partners, in which, in a first step (1), a holding structure (11) with an arrangement of recessed holding elements (110) is incorporated into a joining surface of a first joining partner (10) made of solid material and, in a second step (2), a layer of material which is flowable during application and subsequently solidifies is applied as the second joining partner (20), which penetrates into the recessed holding elements (110) and, after solidification, is held by means of the holding structure (11), characterized by that the holding structure (11) is incorporated by means of water jet cutting. [2] Method according to claim 1, characterized by that at least some of the holding elements (110) are incorporated obliquely with respect to the adjacent surface of the first joining partner (10) at an incision angle (α) between 10° and 80°, in particular between 20° and 70° and preferably between 30° and 60°. [3] Method according to claim 1 or 2, characterized by that the cutting angle (α) changes over the depth profile of the respective holding element (110). [4] Method according to claim 1 or 2, characterized by that adjacent holding elements (110) are directed towards each other or away from each other in their depth direction. [5] Method according to one of the preceding claims, characterized by that the opening width (b) of the holding elements (110) is between 0.5 mm and 3 mm, in particular between 0.8 mm and 2 mm. [6] Method according to one of the preceding claims, characterized by that the cutting depth of the holding elements (110) in their depth direction is between 1 mm and 15 mm, in particular between 2 mm and 10 mm. [7] Method according to one of the preceding claims, characterized bythat the holding elements (110) are designed as a continuous or interrupted straight or wavy line or as circular or random lines in a plan view of the surface of the first joining partner (10). [8] Method according to one of the preceding claims, characterized by that the first joining partner (10) comprises at least one material from the material groups of electrically conductive or semi-conductive materials, electrically non-conductive materials, thermally conductive materials, thermally insulating materials, translucent materials and opaque materials. [9] Method according to one of the preceding claims, characterized by that the second joining partner (20) comprises a material from the group of thermoplastics, thermosetting plastics, elastomeric plastics, ceramic materials and metallic materials, each with or without additives. [10] Method according to claim 9, characterized by that material particles in the form of short fibres or particles are used as additives, the maximum expansion of which is smaller than the clear opening width of the holding elements (110). [11] Method according to one of the preceding claims, characterized by that abrasive particles are added to the water jet (32). [12] Workpiece composite produced using the method according to one of claims 1 to 11.

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