WO2023175241A1

WO2023175241A1 - Method for joining a metal component and a polymer component and a structure comprising said components

Info

Publication number: WO2023175241A1
Application number: PCT/FI2023/050148
Authority: WO
Inventors: Sean CONNOR; Prabilson KHADKA; Pedro VILACA
Original assignee: Aalto University Foundation Sr
Priority date: 2022-03-15
Filing date: 2023-03-15
Publication date: 2023-09-21
Also published as: WO2023175242A1

Abstract

A structure and method for joining of components of different materials, especially joining a metal component and a polymer component. The solution comprises a through slot extrusion joining of metal to polymer- based component along linear or non-linear path with a continuous extrusion in one continuous linear action of the tool, or in continuous linear action of the tool.

Description

Method for joining a metal component and a polymer component and a structure comprising said components

Background of the invention

The invention relates generally to j oining of components of different materials , and especially to j ointing metal components and polymer components together .

Thereby, a structure and a method implementing such j oining technique are disclosed .

The obj ect of the invention is described in more detail in the preambles of independent claims of the application .

There is a continuously growing need for lightweight design in several industries , mainly in the field of transportation . This need has led to the usage of alternative lighter materials and new solutions . New obstacles arise in search of more lean and efficient designs . One of these obstacles is the need to j oin different types of engineering materials via dissimilar material j oining ( DMJ) methods . Achieving satisfactory physical and chemical performance is difficult in DMJ due to fundamental differences in the physical and chemical properties of the base components . It has been especially challenging for making j oints between metallic and polymeric components . Some techniques and arrangement have been developed for this purpose . However, it has been found that there are drawbacks in the current solutions which limits their usage for industrial scale production .

Brief description of the invention

The idea of the invention is to provide a new and improved concept to j oin metal to polymer .

The characteristic features of the structure according to the invention are presented in the characteri zing part of the first independent claim . The characteristic features of the method according to the invention are presented in the characteri zing part of the second independent claim .

In this document the metal-polymer j oining is based on j oining technique called a Through Slot Extrusion Joining with acronym TSEJ . This acronym TSEJ is used in this document for simplicity reasons and for improving clarity .

TSEJ is a method to produce continuous j oints between a metallic component and a polymeric-based component in an overlap- j oint configuration . The TSEJ method uses a rigid extrus ion die system which forms a continuous linear or non-linear slot through which the metallic component will be forced, or extruded, into the polymeric-based component . The continuous linear or non-linear slot is the aperture , or slit , formed by the inner edges of the rigid extrusion die system . The metallic component is forced by a rigid rotating tool , with a tool probe and a tool shoulder, into the polymeric-based component , through the continuous linear or non-linear slot of the rigid extrusion die system, when this rigid rotating tool is plunged in the metallic component and travels along the same path of the continuous linear or non-linear slot . The portion of the metallic component being mechanically processed by the rigid rotating tool softens as result of the heat energy release during the bulk plastic deformation . Thi s heated and softened portion of the metallic component is then forced through the continuous linear or non-linear slot of the rigid extrusion die system into the polymer-based component . During the processing phase of the TSEJ j oint, the tool shoulder keeps the top surface of the metallic component closed, and the tool probe produces the bulk plastic deformation of the metallic component . As the metallic component is forced into the polymeric-based component , the local interaction between these components results in that the constrained polymeric-based component , reacts by forcing its way into the metallic component , forming a geometrical complex shape in the forced, or extruded, portion of the metallic component resulting in the formation of a hook or crab claws shape . This hook or crab claws shape which is now filled with the polymeric-based component forms a strong mechanical interference , also known as clinching . The j oining mechanisms of TSEJ result from this strong mechanical interference , with the additional contribution of the physical and chemical adhesive and diffusion phenomena at the contacting interface between the metallic component and the polymeric-based component .

The idea of the proposed solution is to provide a structure wherein the mentioned continuous TSEJ j oint forms closed j oint geometry with a j oining path and comprises at least one overlapping section .

On the overlapping section the j oint path is provided with overlapping configuration .

The structure comprises : one or more metallic components ; a polymer-based component ; and a continuous j oint between the metallic component and the polymer-based component . Further, cross-section of the continuous j oint comprises hook configuration made of the metallic component and extruded into the polymer-based component . And the continuous j oint comprises a j oining path forming closed j oint geometry . The continuous j oint further comprises at least one overlapping section wherein the j oint path is overlapping .

An advantage of the disclosed solution is that the closed j oint geometry forms fluid pressure tight j oint between the metal component and the polymer-based component . Further, the closed j oint has excellent mechanical strength properties .

According to an embodiment , the overlapping section of the j oining path is at least partially coincident with the previous j oining path . The j oining path can be cons idered to overlap itself and new j oint section is formed on the previous j oint segment and is using the same path shape . According to an embodiment, the overlapping section of the joining path is crossing the previous joining path segment or area whereby there is at least one intersection in the continuous joint.

According to an embodiment, the continuous joint path comprises at least one linear segment and at least one non-linear segment.

According to an embodiment, the continuous joint path comprises three or more linear segments.

According to an embodiment, the continuous joint path comprises only one curved segment with a radius and forms the overlapping section on a segment portion where the joining started.

According to an embodiment, the continuous joint comprises an exit hole at an end of the joint path and the exit hole is located out of the joining path forming the closed joint geometry. In other words, the exit hole is located at a transverse distance from the closed joint geometry .

According to an embodiment, the exit hole may be located on the joining path forming the closed joint geometry and there may still be the overlapping section. The closed shape geometry may be a circle and the overlapping section may be formed and ended on the previous joint section.

According to an embodiment, the exit hole may be filled by metallic material at least partly and may thereby be blocked.

According to an embodiment, the exit hole is located outside the closed joint geometry.

According to an embodiment, the exit hole is located inside the closed joint geometry. The joint is surrounding the exit hole.

According to an embodiment, the continuous joint is load bearing structural joint. An advantage is that the joint is capable of bearing mechanical stresses. According to an embodiment , the closed j oint geometry formed by the continuous j oint is a fluid pressure tight j oint . The closed j oint may be gas and liquid tight .

According to an embodiment , the structure comprises an extrusion die plate structure between the overlapping metallic component and the polymer-based component . The extrusion die plate structure comprises a slot with a path corresponding to the path of the continuous j oint .

According to an embodiment , the structure comprises two metallic components and the polymer-based component is stacked between the metal lic components . The structure is provided with a double-sided j oint comprising the closed j oint geometries on opposite sides of the structure .

According to an embodiment , the disclosed solution relates also to an embodiment for j oining a metallic component and a polymer-based component together . The method comprises : stacking a metallic component on a polymeric- based component ; placing an extrusion die plate structure between the metallic component and the polymeric-based component ; providing the extrusion die plate structure with a through opening; rotating and plunging a probe of a nonconsumable tool across the thickness of the metallic component ; extruding part of the metallic component through the opening of the extrusion die plate structure into the polymer-based component for forming hooks protruding into the polymeric-based component and forming a j oint between the metallic component and the polymer-based component . The method further comprises : providing the j oint with a continuous j oint path and forming closed j oint geometry; and overlapping the j oining path for forming an overlapping section on the j oint .

According to an embodiment , the method further comprises producing the overlapping section on the ongoing path of the j oint .

According to an embodiment , the method further comprises producing the overlapping section by crossing the previously formed path of the j oint and forming at least one intersection for the j oint .

According to an embodiment , the method further comprises ending the extrusion measures of the metallic component at a distance from the j oining path forming the closed j oint geometry and forming thereby an exit hole out of a line of the j oint path forming the closed j oint geometry .

According to an embodiment , the disclosed solution :

- processes bulk materials into novel structures ;

- does not coat a surface with processed powdered material ;

- does not rely on adaptor components and materials between the metallic component and polymer-based component to be j oined, rather, it j oins the components directly;

- utili zes no interfacial adhes ives by necessity or intent ;

- uses no fasteners to create a j oint ;

- j oins metal to polymer as a primary j oint , with the polymer capable of constituting a structural member ;

- the j oints are created with a combination of mechanical interlocking, adhesive bonding, and diffusion mechanisms ;

- is capable of long, continuous j oints .

The above-presented embodiments and the features they contain may be combined to provide desired configurations .

Brief description of the figures

Some embodiments of the proposed solution are illustrated more specifically in the following figures , in which,

Figure 1 comprises several schematical views in Figures la - Ih and shows the through-slot extrusion j oining process from beginning to end, Figure 2 shows schematically the TSEJ process from beginning to end, progressing from A to D,

Figure 3 comprises subfigures 3a - 3h and shows schematically use of the TSEJ process for producing a T- j oint between the metall ic component and the polymer-based component ,

Figure 4 comprises subfigures 4a - 4c and shows schematically use of the TSEJ j oining technique for producing double sided structures ,

Figure 5 comprises subfigures 5a - 5c and shows schematically use of the TSEJ j oining technique for producing a double sided structure with TSEJ j oint having closed shape geometry,

Figure 6 comprises subfigures A-D and shows schematically some di f ferent cross-sections of hook-type j oints formed by means of the TSEJ process between the metallic component and the polymer-based component ,

Figure 7 comprises subfigures 7a - 7c and shows schematically production of an irregular TSEJ j oint path with non-linear shape,

Figure 8 comprises subfigures 8a - 8c showing schematical side views of some possible tool probe geometries usable in the TSEJ j oining process ,

Figure 9 comprises subfigures 9a - 9e and shows schematically some di fferent extrusion die systems usable in the TSEJ j oining process ,

Figure 10 comprises subfigures 10a - l O i and shows schematically structures comprising closed-form j oining paths and having rectangular, circular, and D or hal f circular shapes ,

Figure 11 is a schematic view illustrating the ability of the TSEJ process to create continuous elongated j oints with desired lengths ,

Figure 12 comprises subfigures 12a - 12 f and shows schematically some embodiments of two-sided j oints ,

RECTIFIED SHEET (RULE 91) ISA/EP Figure 13 shows in top views progress of a closed form 2D j oint geometry,

Figure 14 shows in top views progress of a closed form 2D j oint geometry with an overlap on the j oint path,

Figures 15 and 15a show in top views progres s of a closed form 2D j oint geometry with an intersection on the j oint path,

Figures 16 and 16a show in top views progres s of a closed form 2D j oint geometry with an intersection and wherein an exit hole is inside the closed j oint geometry,

Figures 17 and 17a show in top views progres s of a closed form 2D j oint geometry with an intersection and wherein an exit hole outside the closed j oint geometry,

Figure 18 compri ses subfigures 18a - 18 c and shows schematically some cross-sections of j oints comprising metallic hooks penetrating inside the polymer-based component ,

Figure 19 compri ses subfigures 19a - 19c and shows schematically a cross-section of a T-j oint as well as top and bottom views of the same ,

Figure 20 compri ses subfigures 20 a - 20 c and shows schematically top views of forming a closed form j oint with the mentioned overlapping and crossing features and utili zing the extrusion die structure shown in Figure 20a,

Figure 21 is a schematic cross-sectional picture of a double sided j oint comprising the metallic hooks ,

Figure 22 is a schematic cross-sectional microscope picture of a double-sided j oint , and

Figure 23 i s a picture of a structure comprising a circular continuous j oint with the disclosed overlapping feature and provided with a fluid pressure connection inside the closed loop j oint .

For clarity purposes , some embodiments of the proposed solutions are illustrated in a simplified form in the figures . The same reference numbers are used in the figures to denote the same elements and features . Detailed description of some embodiments

Figure 1 shows the through-slot extrusion joining process from beginning to end. Top: the materials are assembled (1, 2, 3) . Upper middle: the tool (5) is positioned above the pre hole (8) . Lower middle: the tool is rotated, plunged, and translated through the workpiece; the tool probe (5b) penetrates through the thickness of the metal component (1) . Bottom: the tool is extracted from the workpiece, producing the finished joint (7) ; an exemplary embodiment of a joint cross-sectional structure is presented in Detail Ca.

Figure 2 shows the side view of the TSEJ process from beginning to end, progressing from A to D. Arrows illustrate the direction of motion of the tool.

Figure 3 illustrates an exemplary application of a removable extrusion die system to produce a T-joint. The crab-claw (6) is formed at the interface between the metallic component (1) and the polymer-based component (2) . The black arrow illustrates the direction in which the extrusion die system (3) is removed after the joint (7) is formed.

Figure 4 shows the material stack (9) consisting of two metallic components (1) , two extrusion die systems (3) , and one polymer-based component (2) . The assembled stack and finished workpiece are displayed on the right.

Figure 5 shows an exemplary embodiment of a simultaneously processed double-sided TSEJ joint, in which the material stack (9) is metallic-polymeric-metallic components .

Figure 6 depicts exemplary embodiments of structures formed with TSEJ. The crab claw-like structure can develop asymmetrically (left) ; with long and thin structures (middle left) ; short and thick (middle right) ; or short and symmetric rounded claws (right) . The tool geometry (5a, 5b) determines the form of these structures. Figure 7 shows an example of an irregular TSE J joint path. The extrusion slot (4) can take any ID, 2D, or 3D form to define the joining path.

Figure 8 shows exemplary embodiments of different tool probe (5b) geometries, with no intention to exclude other tool probe geometries from the scope of the invention.

Figure 9 illustrates the difference between a monolithic extrusion die system (3a) and a multi-component extrusion die system (3b) , and how the extrusion die system (3) may seat into a groove in the polymer component surface (2a) .

Figure 10 shows exemplary embodiments of TSEJ implementation in 2D closed form joining paths. The paths can consist of linear and/or non-linear sections, with the multi-component extrusion die system (3b) defining the joining path via the location of the slot (4) .

Figure 11 illustrates visually the ability of the TSEJ process to create continuous joints an any non-zero length .

Figure 12 depicts additional example embodiments of a two-sided joint (9) . Non-linear and irregular joining paths are depicted. Two processing tools (5) are used to create opposing joints simultaneously into a single polymer-based component (2) .

Figure 13 shows an example of a closed form 2D joint geometry with no overlap outside of the plunge and exit holes .

Figure 14 shows an example of a 2D joint geometry including a section of re-processed material, past the initial plunge location up to the exit hole in white. This is denoted with an arrow next to the joint.

Figure 15 shows an example of a 2D joint geometry which includes an area of intersection between a newly processed zone and a previously processed zone. Figure 16 shows an example of a closed form 2D joint geometry where the process is initiated and ended within a closed joint geometry.

Figure 17 shows an example of a closed form 2D joint geometry where the location of intersection can be formed at locations of oblique angled intersection.

Figure 18 presents three examples of real-world cross sections of TSEJ joints produced with a 5 mm thick metal component on top, and a 5 mm thick polymer-based component on the bottom.

Figure 19 presents a real-world T-joint made between a metallic component and a polymer based component with a removable extrusion die system (3) . The top image is a cross-section, and the lower images are the top and bottom side of the finished component.

Figure 20 presents the top surface of a closed-form two-dimensional joint (7) . A polymer-based component (2) is visible underneath the metal component (1) through the hole in the center of the part.

Figure 21 presents a double-sided two-dimensional TSEJ joint (7) with the metal (1) and polymer-based (2) components of the material stack (9) visible from the near side .

Figure 22 presents the cross section of a doublesided TSEJ joint with the full material stack (9) visible.

Figure 23 presents a double side joint with circular path resulting in a closed gas-tight closed domain with end of path overlapping the starting of the path. There is a pressure connector inside the circular joint so that the arrangement is ready to be mechanically tested for internal pressure resistance.

TSEJ is a method to produce continuous joints between a metallic component (1) and a polymer-based component (2) in an overlap- oint configuration. The TSEJ method uses a rigid extrusion die system (3) which forms a continuous slot (4) through which the metallic component (1) will be forced, or extruded, into the polymer-based component (2) . The continuous slot (4) is the aperture, or slit, formed by the inner edges of the rigid extrusion die system (3) . The metallic component (1) is forced by a rigid rotating tool (5) , with a tool probe (5a) and a tool shoulder (5b) , into the polymer-based component (2) , through the continuous slot (4) of the rigid extrusion die system (3) , when this rigid rotating tool (5) is plunged in the metallic component (1) and travels along the same path of the continuous slot (4) . The portion of the metallic component (1) being mechanically processed by the rigid rotating tool (5) softens as result of the heat energy release during the bulk plastic deformation. This heated and softened portion of the metallic component (1) is then forced through the continuous slot (4) of the rigid extrusion die system (3) into the polymer- based component (2) . During the processing phase of the TSEJ joint (7) , the tool shoulder (5b) keeps the top surface of the metallic component (1) closed, and the tool probe (5a) produces the bulk plastic deformation of the metallic component (1) . As the metallic component (1) is forced into the polymer-based component (2) , the local interaction between these components results in that the constrained polymer-based component (2) , reacts by forcing its way into the metallic component (1) , forming a geometrical complex shape in the forced, or extruded, portion of the metallic component (1) resulting in the formation of a hook or crab claws shape (6) . The process evolutes in a quasi-conserva- tion of volume, so no significant voids are formed in the joining zone. The hook or crab claws shape (6) which is filled with the polymer-based component (2) forms a strong mechanical interference, also known as clinching. The joining mechanisms of TSEJ result from this strong mechanical interference, with the additional contribution of the physical and chemical adhesive and diffusion phenomena at the contacting interface between the metallic component (1) and the polymer-based component (2) .

The TSEJ cycle develops along the following sequence :

-The metallic component (1) , the polymer-based component (2) with the rigid extrusion die system (3) in between, are brought together and clamped in overlap- j oint, or T-joint configuration;

-To prevent the formation of flash, during the initial plunge of the tool probe (5a) of the rigid rotating tool (5) , a pre-hole (8) may be opened in the metallic component (1) at the start position of the TSEJ joint (7) . This pre-hole (8) can be cylindrical or conical. This prehole (8) can be blind or through. This pre-hole (8) can be larger, smaller, or equal to the diameter of the tool probe (5a) ;

-The tool probe (5a) of the rigid rotating tool (5) , is plunged at the start position of the TSEJ joint (7) until the tool shoulder (5b) contacts the top surface of the metallic component (1) ;

-Upon a given dwell time, that can be equal to zero seconds or more, the rigid rotating tool (5) travels along the path of the continuous slot (4) , with constant or variable travel speed;

-At the end position of the TSEJ joint (7) , the rigid rotating tool (5) is extracted from the metallic component ( 1 ) ;

-The consolidated TSEJ joint (7) and inherent structural system is extracted from the clamping.

The hook or crab claws shape (6) formed by the metallic component (1) in interaction with the polymer-based component (2) can have the following configurations: -Configuration of a hook, where only one of the sides of the extruded portion of the metallic component (1) extends into the polymer-based component (2) ;

-Configuration of a symmetrical crab claw, where both sides of the extruded portion of the metallic component (1) extends equally into the polymer-based component (2) ;

-Configuration of an asymmetrical crab claw, where both sides of the extruded portion of the metallic component

(1) extends differently into the polymer-based component

(2) .

The width of the continuous slot (4) is greater than zero, and it can be constant or variable. The continuous slot (4) can follow a one-dimensional, two-dimensional, or three-dimensional path.

The rigid extrusion die system (3) can be made of one (e.g., monolithic die (3a) ) , or more components (e.g., strips (3b) ) , which define an inner continuous slot (4) . After the TSEJ cycle is completed, if the rigid extrusion die system (3) if made of multiple components, it may be kept, within the joint, or it may be extracted.

The rigid extrusion die system (3) can be fully, or partially, embedded in the metallic component (1) , or in the polymer-based component (2) , or partially embedded in both the metallic component (1) and the polymer-based component (2 ) .

The surface of the polymer-based component (2) , facing the joining domain, can be flat, or have one or more shallow grooves, to mate with the fully, or partially embedded rigid extrusion die system (3) .

The surface of the metallic component (1) , facing the joining domain, can be flat, or have one or more shallow grooves, to mate with the fully, or partially embedded rigid extrusion die system (3) .

The rigid extrusion die system (3) is made of high- strength material compared with the strength of the metallic component (1) and the polymer-based component (2) . The rigid extrusion die system (3) is made with minimum thickness, as long as it provides rigidity effect to act as rigid, i.e. non-def ormable, extrusion die.

The joint configuration between the overlapping metallic component (1) and the polymer-based component (2) can be overlap- oint or T-joint. In an overlap- j oint configuration the rigid extrusion die system (3) is positioned in-between the metallic component (1) and the polymer-based component (2) . In a T-joint configuration the rigid extrusion die system (3) is positioned parallel, under and in contact with the metallic component (1) , while the polymer- based component (2) is positioned perpendicular to the metallic component (1) .

In TSEJ, the TSEJ joint (7) length is longer than zero, with no maximum length. A TSEJ joint (7) can include zones of overlap and/or intersection with previous TSEJ joint (7) processed zones.

The rigid rotating tool (5) can be made in one single component or made of multicomponent assembled together, namely a tool probe (5a) and a tool shoulder (5b) .

The length of the tool probe (5a) and the plunged position of the rigid rotating tool (5) during the manufacturing of the TSEJ joint (7) , is such that the tip of the tool probe (5a) can be positioned above, below, or at the level of the rigid extrusion die system (3) .

Two metallic components (1) , with one polymer-based component (2) in between, may be used to form the metal- polymer-metal stack with double-side TSEJ joint (9) . The metal-polymer-metal component stack has two opposing TSEJ joints (7) with a rigid extrusion die system (3) in between each metal-polymer joint interface. One rigid rotating tool (5) can be applied sequentially, to create one continuous joint per side of the material stack. In alternative, two rigid rotating tool (5) can be applied simultaneously to create the stack metal-polymer-metal with double-side TSEJ joint (9) . The opposing TSEJ joints (7) may be directly opposite each other or may constitute two partially or completely different joining paths on either side of the material stack.

The parameters controlling the process TSEJ are the following :

1. Geometry of the tool probe (5a) ;

2. Geometry of the tool shoulder (5b) ;

3. Rotation speed of the tool (5) , or of the probe (5a) , if the shoulder (5b) is static;

4. Plunging speed or plunging force of the tool (5) ;

5. Plunging depth of the tool (5) ;

6. Dwell time at the maximum plunge depth, in plunging force or vertical position control;

7. Extraction speed of the tool (5) ;

8. Travel speed of the tool (5) , if the probe (5a) is continuous plunged in the metal component (1) , traversing along the path of the slot (4) in the extrusion die system (3) ;

9. Offset distance between the central axis of the tool (5) and the center of the slot (4) ;

10. Material and thickness of the extrusion die system (3) ;

11. Dimensions (including thickness) and form of the extrusion die system (3) ;

12. Width of slot (4) of the extrusion die system (3) ;

13. Path and orientation of the slot (4) of the extrusion die (3) ;

14. Material and thickness of the metal component (1) ;

15. Material and thickness of the polymer-based component (2 ) .

List of reference numerals: I. Metallic component

2. Polymer-based component

2a. Shallow groove (optional) in polymer component (2) , to mate with the extrusion die system (3)

3. Rigid extrusion die system (thin and rigid plate compared with the metal (1) and the polymer (2) , at processing thermomechanical conditions)

3a. Monolithic, or single component extrusion die system (3)

3b. Multi-body extrusion die system (3) consisting of multiple components to constitute the system

4. Slot, or aperture, formed by the extrusion die system (3)

5. Non-consumable and rigid joining tool

5a. Probe of the non-consumable and rigid welding tool (5)

5b. Shoulder of the non-consumable and rigid welding tool (5)

6. Hook or crab claw shape formed by the extruded portion of the metallic component into the polymer-based component when viewed on a cross section parallel to the processing path

7. TSE J j oint

8. Blind- or through-hole style pre-hole used at (or in the vicinity of) the plunge location

9. Metal-polymer-metal stack with doubleside TSEJ joint

10. Exit hole

II. Overlapping section

Ila. Coincident overlapping section 11b. Crossing overlapping section

12. Intersection

13. Joint start

14. Joint end 15. Pressure connection

Let it be mentioned that the disclosed coincident overlapping feature may be implemented also in the structures disclosed in Figures 5, 10 and 12. Thus the feature may be utilized in differently shaped and formed structures.

The figures and their description are only intended to illustrate the inventive idea. However, the scope of protection of the invention is defined in the claims of the application .

Claims

1. A structure comprising: at least one metallic component; a polymer-based component; and a continuous joint between the metallic component and the polymer-based component; cha ra ct e r i z ed in that, cross-section of the continuous joint comprises hook configuration made of the metallic component and extruded into the polymer-based component; the continuous joint comprises a joining path forming closed joint geometry; and wherein the continuous joint further comprises at least one overlapping section wherein the joint path is overlapping .

2. The structure according to claim 1, c h a r a c t e r i z e d in that, the overlapping section of the joining path is at least partially coincident with the previous joining path.

3. The structure according to claim 1, c h a r a c t e r i z e d in that, the overlapping section of the joining path is crossing the previous joining path whereby there is at least one intersection in the continuous joint.

4. The structure according to any one of the previous claims 1 - 3, c h a r a c t e r i z e d in that, the continuous joint path comprises at least one linear segment and at least one non-linear segment.

5. The structure according to claim 1, c h a r a c t e r i z e d in that the continuous joint comprises an exit hole at an end of the joint path; and the exit hole is located out of the joining path forming the closed joint geometry.

6. The structure according to claim 5, c h a r a c t e r i z e d in that, the exit hole is located outside the closed joint geometry .

7. The structure according to claim 5, c h a r a c t e r i z e d in that the exit hole is located inside the closed joint geometry .

8. The structure according to any one of the preceding claims 1 - 7, c h a r a c t e r i z e d in that the continuous joint is load bearing structural j oint .

9. The structure according to any one of the preceding claims 1 - 8, c h a r a c t e r i z e d in that the closed joint geometry formed by the continuous joint is a fluid pressure tight joint.

10. The structure according to any one of the preceding claims 1 - 9, c h a r a c t e r i z e d in that, the structure comprises an extrusion die plate structure between the overlapping metallic component and the polymer-based component; and the extrusion die plate structure comprises a slot with a path corresponding to the path of the continuous j oint .

11. The structure according to any one of the preceding claims 1 - 10, c h a r a c t e r i z e d in that, the structure comprises two metallic components; the polymer-based component is stacked between the metallic components; and wherein the structure is provided with a doublesided joint comprising the closed joint geometries on opposite sides of the structure.

12. A method for joining a metallic component and a polymer-based component together, the method comprises: stacking a metallic component on a polymeric-based component ; placing an extrusion die plate structure between the metallic component and the polymeric-based component; providing the extrusion die plate structure with a through opening; rotating and plunging a probe of a non-consumable tool across the thickness of the metallic component; extruding part of the metallic component through the opening of the extrusion die plate structure into the polymer-based component for forming hooks protruding into the polymeric-based component and forming a joint between the metallic component and the polymer-based component; cha ra ct e r i z ed by providing the joint with a continuous joint path and forming closed joint geometry; and overlapping the joining path for forming an overlapping section on the joint.

13. The method according to claim 12, c h a r a c t e r i z e d by producing the overlapping section on the ongoing path of the joint.

14. The method according to claim 12, c h a r a c t e r i z e d by producing the overlapping section by crossing the previously formed path of the joint and forming at least one intersection for the joint.

15. The method according to claim 14, c h a r a c t e r i z e d by ending the extrusion measures of the metallic component at a distance from the joining path forming the closed joint geometry and forming thereby an exit hole out of a line of the joint path forming the closed joint geometry .