ATTACHING AN OBJECT TO A SUBSTRATE

Abstract

A method of attaching an object to a substrate with a fastener, and an associated fastener. The object is tensible and has an engagement portion. The fastener has a protrusion, which includes thermoplastic material in a solid state. The method includes applying a mechanical pressing force and a mechanical excitation capable to cause a movement of the fastener in a distal direction so that the protrusion penetrates into the substrate and liquefies the thermoplastic material until a flow portion of the thermoplastic material is flowable and penetrates into structures of the substrate. The engagement portion is moved in the distal direction by the movement of the fastener, wherein the movement of the engagement portion in the distal direction causes a tensioning force in the object, and wherein the fastener has a protruding portion extending at least partly into the substrate after the thermoplastic material resolidifies.

Claims

1. A method of attaching an object to a substrate, the method comprising the steps of: providing the obiect, wherein the object is tensible and comprises an engagement portion, providing the substrate comprising a proximal surface, providing a fastener, wherein the fastener comprises at least one protrusion, wherein the protrusion comprises thermoplastic material in a solid state, arranging the fastener, the object and the substrate relative to each other in a manner that the engagement portion of the object is between at least a portion of the fastener and the substrate, applying a mechanical pressing force and a mechanical excitation capable to cause a movement of the fastener in a distal direction in a manner that the at least one protrusion penetrates the proximal surface of the substrate and to liquefy the thermoplastic material to at least one of the fastener and the substrate until a flow portion of the thermoplastic material is flowable and penetrates into structures of the substrate, stopping the mechanical excitation and letting the thermoplastic material resolidify to yield a positive-fit connection between the fastener and the substrate, wherein the engagement portion is moved in the distal direction by the movement of the fastener, wherein the movement of the engagement portion in distal direction causes a tensioning force in the object and wherein the fastener comprises a protruding portion extending at least partly into the substrate after the step of letting the thermoplastic material resolidify.

2. The method according to claim 1, wherein the protruding portion extends to a depth in the substrate that is larger than a thickness of the protruding portion.

3. The method according to claim 1, wherein the step of applying the mechanical pressing force and the mechanical excitation comprises a first sub-step of causing the protrusion to penetrate the proximal surface and to penetrate into the substrate, and a second sub-step of liquefying the thermoplastic material, wherein the first sub-step is prior to the second sub-step and wherein the engagement portion is engaged with the fastener during the first sub-step in a manner that it is moved in the distal direction.

4. The method according to claim 3, wherein the engagement portion is engaged with the protrusion in a manner that it penetrates the proximal surface.

5. The method according to claim 1, wherein the proximal surface is made of a material that is not compressible.

6. The method according claim 3, wherein the proximal surface is made of a material that is compressible

7. The method according to claim 6, wherein the engagement portion is engaged with the fastener in a manner that a penetration of the proximal surface by the engagement portion is prevented.

8. The method according to claim 1, wherein the method comprises a step of changing a compressive strength in a region of the substrate at least locally such that a critical compressive strength needed for the liquefaction of the thermoplastic material is generated.

9. The method according to claim 1, wherein the method comprises a step of compressing a region of the substrate at least locally such that a critical density needed for the liquefaction of the thermoplastic material is generated.

10. The method according to claim 1, wherein the ratio between an extension of the protrusion in the distal direction and a thickness of the protrusion is at least 1.

11. The method according to claim 1, wherein the step of applying the mechanical excitation comprises applying mechanical oscillations along an axis that runs at an angle to the proximal surface.

12. The method according to claim 11, wherein the axis is perpendicular to the proximal surface.

13. The method according to claim 1, wherein the mechanical excitation is mechanical vibration.

14. The method according to claim 1, wherein the step of providing the fastener comprises providing a fastener comprising a fastener body and a protrusion region distally of the fastener body, wherein the protrusion region comprises a plurality of protrusions that comprise the thermoplastic material.

15. The method according to claim 1, wherein the mechanical pressing force and the mechanical excitation are applied locally to at least one of the fastener and the substrate and wherein the step of applying the mechanical pressing force and the mechanical excitation and the step of stopping the mechanical excitation and letting the thermoplastic material resolidify is repeated several times at different positions on at least one of the fastener and the substrate.

16. The method according to claim 1, wherein a first fastener and a second fastener are provided, wherein the object comprises a first engagement portion and a second engagement portion, and wherein the tensioning force in the object is caused by a simultaneous movement of the first and second engagement portions in distal direction; or the movement of the second engagement portion, wherein a fixation of the first engagement portion to the substrate is established by the first fastener prior to the step of applying a mechanical pressing force and a mechanical excitation to the second fastener

17. The method according to claim 1, wherein the object comprising an object proximal surface and an object distal surface and the steps of: arranging the object relative to the substrate such that the object distal surface is in physical contact with the proximal surface of the substrate; arranging the fastener relative to the object and the substrate such that the protrusion is at least partly in contact with the proximal surface of the substrate and such that a distal surface of the fastener is in contact with the object proximal surface.

18. The method according to claim 17, wherein the protrusion that is put in contact with the proximal surface of the substrate during the step of arranging the fastener relative to the object and substrate comprises the thermoplastic material, wherein the protrusion and the distal surface of the fastener are designed such that the flowable portion of the thermoplastic material penetrates into the structures of the substrate during the step of applying the mechanical pressing force and the mechanical excitation and such that the distal surface of the fastener is not able to penetrate the obiect.

19. The method according to claim 17, wherein the distal surface of the fastener and the portion of the object proximal surface that is put in contact with the distal surface of the fastener are designed to engage with one another.

20. The method according to claim 17, wherein the protrusion that is put in contact with the proximal surface of the substrate during the step of arranging the fastener relative to the object and the substrate is a first protrusion and wherein the fastener comprises a second protrusion comprising the distal surface of the fastener that is in contact with the object proximal surface during the step of arranging the fastener relative to the object and substrate.

21. The method according to claim 20, wherein the first protrusion is a protrusion of a first kind comprising the thermoplastic material and the second protrusion is a protrusion of a second kind comprising the thermoplastic material, wherein the shape of the protrusion of the first kind is such that the flowable portion of the thermoplastic material penetrates into the structures of the substrate, and wherein the shape of the protrusion of the second kind is such that a flowable portion of the thermoplastic material penetrates into structures of the object during the step of applying the mechanical pressing force and the mechanical excitation capable to liquefy the thermoplastic material.

22. The method according to claim 1, wherein the substrate comprises a distal surface and wherein the mechanical excitation is applied to the distal surface of the substrate and a force for moving the fastener in the distal direction is applied to the fastener.

23. The method according to claim 1, wherein the step of providing the substrate comprises providing a substrate comprising thermoplastic material and wherein said thermoplastic material liquefies at least partly during the step of applying the mechanical excitation such that a weld is formed between said liquefied thermoplastic material and liquefied thermoplastic material of the fastener after resolidification of the thermoplastic materials.

24. The method according to claim 1, wherein the object comprises anisotropic deformation properties and wherein at least one of the design of the at least one fastener, the number of fasteners and the arrangement of the at least one fastener relative to the object is adapted to the anisotropic deformation properties of the obiect.

25. A for fastener for attaching an object to a substrate by a method according to claim 1, wherein the fastener comprises a fastener body forming a proximal surface and a distal surface, at least one protrusion and thermoplastic material in a solid state, wherein the protrusion protrudes from the distal surface wherein the protrusion comprise the thermoplastic material at outer surfaces, and wherein the fastener is equipped to transfer a movement in a distal direction to a movement of the object in the distal direction.

26. The fastener according to claim 25, wherein the fastener comprises a protrusion of a first kind and a protrusion of a second kind, wherein the protrusion of the second kind is smaller in length than the protrusion of the first kind, wherein the protrusion of the first kind is designed for being anchored in the substrate and the protrusion of the second kind is designed to engage with the object.

27. The fastener according to claim 25, wherein the protrusion consists of the thermoplastic material.

28. The fastener according to claim 25, wherein the at least one protrusion comprises a structure designed and arranged to promote local compression of the substrate when forced into the substrate.

29. The device according to claim 25, wherein the protrusion comprises an extension in distal direction and a thickness, wherein the ratio between the extension in distal direction and the thickness is at least 1.

30. The device according to claim 25, wherein the fastener comprises a protrusion region comprising a plurality of protrusions that comprise the thermoplastic material.

31. The device according to claim 25, wherein at least one of the design of the at least one protrusion, the number of protrusions and the arrangement of the at least one protrusion is suitable to generate an anisotropic tensioning force in the object when the object is attached to the object by the method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0220] Hereinafter, embodiments of the invention are described referring to drawings. The drawings are all schematic and not to scale. In the drawings, same reference numbers refer to same or analogous elements. The drawings are used to explain the invention and embodiments thereof and are not meant to restrict the scope of the invention. Terms designating the orientation like “proximal”, “distal”, etc. are used in the same way for all embodiments and drawings.

[0221] The drawings show:

[0222] FIGS. 1a-1c Sectional views of a fastener, an object and a substrate, wherein the fastener is used to attach the object to the substrate. Three stages of an exemplary method according to the invention are shown;

[0223] FIGS. 2a and 2b Two stages of another exemplary method of attaching the object to the substrate by the fastener in sectional views;

[0224] FIG. 3 An initial situation of an exemplary embodiment of the method;

[0225] FIG. 4 The arrangement and character of the fastener, the object and the substrate at the beginning of the method according to FIG. 3;

[0226] FIG. 5 A bonding location established by the method according to FIGS. 3 and 4;

[0227] FIGS. 6-8 An exemplary embodiment of a fastener used in the method according to FIGS. 3-5;

[0228] FIG. 9 An alternative embodiment of a fastener suitable for use in the method;

[0229] FIGS. 10a-10c Further embodiments of the fastener including a structure for promoting local compression of the substrate;

[0230] FIGS. 11a and 11b A schematic of an object having anisotropic deformation properties and of a fastener adapted to the anisotropic deformation properties;

[0231] FIG. 12 An embodiment of the method in which a sonotrode is applied to the substrate and a force for advancing the protrusion into the substrate is applied to the fastener;

[0232] FIG. 13 Two representative stress-strain-curves for a panel formed by an incoherent material; and

[0233] FIG. 14 An exemplary embodiment of a fastener including a tension structure.

DETAILED DESCRIPTION OF THE INVENTION

[0234] FIGS. 1a-1c show the relative arrangement and interaction of a fastener (1), an object (30) and a substrate (2) at three different stages of an exemplary embodiment of the method.

[0235] A method according to the invention includes providing the fastener 1 including at least one protrusion 9 with thermoplastic material 3 in a solid state, providing the substrate 2 having a proximal surface and providing the object 30 that is to be attached to the substrate 2 by the use of the fastener and that is tensible and includes an engagement portion 38. The method includes further arranging the fastener 1, the object 30 and the substrate 2 relative to each other such that an engagement portion 38 of the object 30 is between at least a portion of the fastener 1 and the substrate 2. The method further includes applying a mechanical pressing force and a mechanical excitation to at least one of the fastener 1 and the substrate 2, wherein the mechanical pressing force and as the case may be the mechanical excitation are capable to cause a movement of the fastener 1 in a distal direction in a manner that the at least one protrusion 9 penetrates the proximal surface 4 of the substrate 2 and wherein the mechanical pressing force and the mechanical excitation are capable to liquefy the thermoplastic material 3 until a flow portion of the thermoplastic material is flowable and penetrates into structures 10 of the substrate 2 prior to stopping the mechanical excitation and letting the thermoplastic material resolidify to yield a positive-fit connection between the fastener 1 and the substrate 2.

[0236] FIGS. 1a and 1b show the situation during the step of causing the movement of the fastener in the distal direction.

[0237] In FIG. 1a, the fastener 1 has not yet engaged with the engagement portion 38 of the object 30 in a manner that the distal movement of the fastener 1 has caused a distal movement of the engagement portion. Hence, the object 30 is not yet tensioned because there is no tensioning force generated by the movement of the fastener and the engagement portion, respectively.

[0238] In FIG. 1b, the fastener 1 interacts with the engagement portion 38 in a manner that the distal movement of the fastener 1 pulls the engagement portion 38 in the distal direction. Portions of the object 30 that are different from the engagement portion 38 cannot move distally or can move distally up to a reduced path only, because the proximal surface 4 of the substrate prevents the portion from following the engagement portion 38. Hence, the object 30 is stretched (tensioned) by a tensioning force (indicated by the black arrow in the Figures) generated by a relative movement between the engagement portion 38 and other portions of the object 30.

[0239] FIG. 1c shows the situation during the step of applying the mechanical pressing force (indicated by the empty arrow) and the mechanical excitation (indicated by the double-sided arrow) to liquefy the thermoplastic material 3 at least partly and to press liquefied thermoplastic material into structures 10 of the substrate 2.

[0240] A protruding portion 91 is not liquefied during the step or does at least not penetrate into the structures 10 of the substrate 2 in order to cause deep-effective anchorage.

[0241] The anchorage of the fastener established after resolidification of the thermoplastic material 3 fixes the relative position of the engagement portion 38 relative to the portions of the object 30 that are different from the engagement portion 38. Hence, the tensioning force is maintained after execution of the method.

[0242] FIG. 1a-1c show further the following optional features: [0243] A compressed region 201. In the embodiment shown, the compression is mainly caused by the protrusion 9. This means the compression is local mainly. However, the object 30 contributes to the compressed region 201 by causing a global compression. [0244] The substrate 2, or at least the portion of the substrate 2 in which the bonding between the fastener 1 and the substrate 2 is established, is compressible.

[0245] FIGS. 2a and 2b show two exemplary embodiments, wherein the substrate, or at least the portion of the substrate 2 in which the bonding between the fastener 1 and the substrate 2 is established, is not compressible.

[0246] In the embodiment shown, the engagement portion 38 engages with a distal portion of the fastener 1 in a manner that moves in the distal direction together with the protrusion 9. In other words, at least a portion of the engagement portion 38 does not move relative to the protrusion 9 during the step of causing a movement of the fastener 1 in a distal direction, at least. In particular, at least a portion the engagement portion 38 penetrates the proximal surface 4 together with the protrusion 9.

[0247] As in the embodiment of FIGS. 1a-1c, the proximal surface 4 prevents that portions of the object 30 that are different from the engagement portion 38 follow the engagement portion 38. Hence, the object 30 is stretched (tensioned) by the tensioning force (indicated by the black arrow in the Figures) generated by the relative movement between the engagement portion 38 and the portions of the object 30 that are different from the engagement portion 38.

[0248] FIG. 2a shows the situation during the step of forcing the protrusion 9 into the substrate 2. FIG. 2b shows the situation during the step of liquefying at least a portion of the thermoplastic material by the mechanical pressing force (indicated by the empty arrow in the Figures) and by the mechanical excitation (indicated by the double-sided arrow).

[0249] FIGS. 2a and 2b show further the following optional features: [0250] A ratio between the length and the thickness of the fastener 1 that is larger than 1. Therein, the length is given by the extension 25 of the fastener in distal direction and the thickness 26 is given by an extension of the protrusion 9 in a direction perpendicular to the distal direction. [0251] A ratio between the depth 95 up to which the protruding portion 91 penetrates into the substrate 2 and a thickness 96 of the protruding portion 91 that is larger than 1. Therein, the depth 95 is measured along the distal direction and the thickness 26 is given by an extension of the protruding portion 91 in a direction perpendicular to the distal direction.

[0252] FIGS. 3-9 show configuration and devices of a further exemplary method.

[0253] In particular, the method and fastener 1 shown are capable in the application of fixing an object 30 being the hook portion of a hook and loop tape to the substrate 2.

[0254] In the embodiment shown in FIGS. 3-5, the hook and loop tape is of the “Velcro”-type. However, the method and fastener disclosed can be used for other objects 30 having similar properties and/or a similar structure than the hook portion.

[0255] FIG. 3 shows the general concept of this application.

[0256] The hook portion 30 includes a hook area 37 that forms a proximal surface 31 of the hook portion 30.

[0257] The fastener 1 is designed to clamp the hook portion 30 to the substrate 2 by the method. In other words, the fastener 1 is designed to yield a positive-fit connection between the fastener and the substrate 2 using the method and to clamp the hook portion 30 to the substrate 2.

[0258] A sonotrode 20 is used to apply the mechanical pressing force and the mechanical excitation, this means the mechanical oscillations in the application shown, to liquefy the flow portion of the thermoplastic material arranged at the protrusions 9.

[0259] FIG. 4 shows a cross-sectional view of an embodiment of the application before fixing the hook portion 30 to the substrate 2 by the fastener 1.

[0260] In the embodiment shown, the fastener 1 has a fastener body 7 of a closed shape that forms an opening 8. The opening 8 is designed in a manner that the proximal surface 31 of the hook portion 30 (this means the hook area 37) is exposed (lies open) after fixing the hook portion 30 to substrate 2 by the fastener 1.

[0261] The fastener 1 includes protrusions 33 of a first kind and protrusions 34 of a second kind. The protrusions of the first and second kind differ in thickness and length, wherein the protrusions 33 of the first kind are larger in thickness and length than the protrusions 34 of the second kind.

[0262] In the embodiment shown, the protrusions 34 of the second kind consist of thermoplastic material 3.

[0263] The shape of the fastener body 7, the shape of the hook portion 30, and the arrangement of the protrusions (33, 34) are adapted to each other in a manner that a circumferential edge of the hook portion 30 is between the protrusions of the first and second kind after arranging the fastener 1, the substrate 2 and the hook portion 30 in the desired manner. In other words, the distal end of the protrusions 33 of the first kind is in contact with the proximal surface 4 of the substrate 2 and the distal end of the protrusions 34 of the second kind is in contact with the object proximal surface 31.

[0264] The design and arrangement of the fastener 1 and the hook portion 30 according to FIG. 4 is particularly suitable for a reliable attachment of the hook portion 30 to the substrate 2.

[0265] However, there are applications in which it may be advantageous to design and arrange the fastener 1 and the object 30, for example the hook portion, in a manner that: [0266] Both, the row of the protrusions 33 of the first kind and the row of the protrusions 34 of the second kind engage with the object 30; or [0267] There is only one row of protrusions. The row of protrusion can engage with the substrate 2 directly or by penetrating the object 30. If the row of protrusion engages with the substrate 2 directly, the fastener body 7 can include a distal surface portion arranged to cause the movement of the engagement portion 38 of the object 30 in distal direction.

[0268] Embodiments including one row of protrusions only or including two rows of protrusions of a different kind do not need to include a fastener 1 having a fastener body 7 of a closed shape that forms an opening 8 as shown in FIG. 4. In other words, the fastener 1 does not need to be a fixation ring or a fixation rectangle as shown in FIGS. 4-9. Rather, the fastener 1 can have any shape suitable for a specific application.

[0269] One can also envisage using at least one fastener 1 including at least one protrusion that is designed to engage with the substrate 2 directly or by penetrating the object 30.

[0270] The most promising design and arrangement of the fastener 1 and the object 30 can depend on the application and/or the strength of the connection between the object 30 and the substrate 2 needed. However, it can also depend on at least one of the properties of the material(s) of which the object 30 is made, the design of the protrusions, and/or the manner the step of applying the mechanical pressing force and the mechanical excitation is performed.

[0271] For example, an embodiment including at least one fastener 1 including at least one protrusion 9 or a fastener 1 including one row of protrusions only, the protrusion or row of protrusion engages with the object 30 can be suitable if the object 30, for example the hook portion, is made of fibers that are stable at the temperatures generated during the method and mechanically stable in a manner that at least a portion of the fibers of the engagement portion 38 is not cut during the method. The manner the step of applying the mechanical pressing force and the mechanical excitation is performed can be adapted to the stability of the fibers.

[0272] Alternatively or in addition, the protrusion(s) 9 can be designed to move through the object 30 without cutting a plurality, in particular without cutting a majority, of the fibers of the engagement portion 38. For example, the protrusion(s) 9 can be pin-shaped.

[0273] Alternatively or in addition, the object 30 can have a density that allows for the material of which the object 30 is made, for example fibers and/or meshes, to be pushed away by the penetrating protrusion(s) 9 rather than being cut by the penetrating protrusion(s) (9).

[0274] FIG. 5 shows the embodiment of the application of FIG. 4 after fixing the hook portion 30 to the substrate 2 by the fastener 1, in detail.

[0275] The protrusions 33 of the first kind have penetrated into the substrate 2, wherein the flow portions of the protrusions 33 of the first kind have penetrated into structures 20 of the substrate 2 and wherein the protruding portions 91 have been formed.

[0276] The protrusions 34 of the second kind have liquefied during the step of applying the mechanical pressing force and the mechanical excitation (the mechanical oscillations, in the case shown). Thereby, the portions of the hook area 37 in the region of former protrusions 34 of the second kind are embedded in the re-solidified thermoplastic material. This causes a fixation of the hook portion 30 to the fastener 1 that is more reliable than a fixation by clamping only.

[0277] In the embodiments shown in the Figures, the engagement portion 38 is the portion of the object 30 that comes into contact with the fastener 1, wherein the engagement portion 38 is of the same kind, for example the same material, structure, etc., as other portions of the object 30. However, one can also envisage an engagement portion 38 that differs from other portions of the object 30. For example, the engagement portion 38 can be of a material and/or designed to be mechanically more stable to withstand forces that appear during the method or during use of an item including the object 30 that is attached to the substrate 2 by the fastener 1.

[0278] FIG. 6a shows an embodiment of the fastener 1 used in the application according to FIGS. 3-5. The fastener body 7 has the shape of a circular ring that delimits the opening 8.

[0279] A fastener 1 according to FIG. 6a causes a tensioning field in the object 30 with field lines running along radial direction only. Hence, the fastener 1 according to FIG. 6a is in particular suitable for objects 30 with isotropic deformation properties. FIG. 6b shows an alternative embodiment of a fastener 1 that is in particular suitable for objects 30 with isotropic deformation properties. The dashed lines in FIG. 6b indicate the relative arrangement of the protrusions 9 and the radial directions along with the field lines of the generated tensioning field run.

[0280] FIG. 7 shows the fastener 1 according to FIG. 6a in detail and FIG. 8 shows a cross-sectional view through a protrusion 33 of the first kind and a protrusion 34 of the second kind.

[0281] The protrusions 33 of the first kind are arranged as an outer ring on the fastener body 7 and the protrusions 34 of the second kind are arranged as an inner ring on the fastener body 7.

[0282] The outer ring of protrusions 33 is designed for being anchored in the substrate 2 by the method.

[0283] The inner ring of protrusions 34 is designed for tautening the hook portion 30 during the method and for holding the hook portion 30 after fixing the hook portion 30 to the substrate 2 by the fastener.

[0284] The protrusions 9 are arranged in the outer and inner ring along radial directions. Such an arrangement of the protrusions 34 of the second kind leads to a concentric pulling force acting on the hook portion 30 during bonding of the fastener 1 to the substrate 2. Hence it prevents folding, for example.

[0285] Protrusions 34 of the second kind can include at least one of the following features in order to fulfill their function of tautening and fixing the hook portion 30: [0286] The distal end of the protrusions 34 of the second kind can be an edge that runs along a radial direction of the fastener body 7 having the shape of a circular ring. The edge can include a slope that is oriented towards the center of the circular ring. [0287] The distal end of the protrusions 34 of the second kind can be rounded in order to prevent damage of the hook portion 30. [0288] The protrusions 34 of the second kind can be thinner than the protrusions 33 of the first kind. Consequently, they liquefy and/or collapse during the step of applying the mechanical pressing force and the mechanical excitation (the mechanical oscillations, in the case shown) causing embedding of the hook portion 30 rather than cutting the hook portion 30.

[0289] The protrusions 34 of the second kind can include fixing spikes as an optional feature. Fixing spikes can engage with the hooks in the hook area 37. Fixing spikes allow for a pre-assembly of the hook portion 30 and the fastener 1. Therefore, they can be advantageous in a step of arranging the fastener 1, the substrate 2 and the hook portion 30 in the desired manner prior to the step of applying the mechanical pressing force and the mechanical excitation (the mechanical oscillations, in the case shown).

[0290] The overall design of the fastener 1 can be adapted to the object 30 to be fixed, in particular its shape and structure, and to the concrete application.

[0291] In particular, the fastener body 7 can have another shape than the shape of a circular ring.

[0292] The protrusions 9 can be arranged differently from the arrangement shown in FIGS. 6 and 7 on the distal surface 28 of the fastener body 7.

[0293] The fastener 1 can include protrusions 9 of one kind only.

[0294] FIG. 9 shows a further design of a fastener 1 for fixing an object 30 to the substrate 2 by the method, in particular a fastener 1 suitable for the application discussed with respect to FIGS. 3-8.

[0295] The fastener 1 shown includes protrusions 9 of one kind only arranged in a protrusion region 90 covering the whole distal surface 28 of the fastener body 7.

[0296] The distal ends of the protrusions 9 are formed by an edge. The edges are oriented parallel to each other.

[0297] Further, the number of protrusions 9 per unit area is increased compared to the fasteners shown in FIGS. 6-9, for example.

[0298] Such an arrangement of protrusions 9 and/or an increase in protrusions 9 per unit area can be advantageous for objects 30 that are fluffy, slack and/or highly stretchable. Textiles are examples of such objects 30.

[0299] FIGS. 10a-c do not only increase locally the density of substrate 2 by the protrusion displacing material of the substrate 2 but also by including structures 24 that are designed and arranged to promote local compression of the substrate 2.

[0300] The structures 24 shown in FIGS. 10a-c are designed and arranged to pull down fibrous material of the substrate 2 and/or to felt such material further and/or to embed the protrusions 9 including such structures 24 better in the material of the substrate 2, for example for distributing load over a larger area.

[0301] The embodiments of the fastener 1 shown in the FIGS. 10a and 10b include so-called barbs 24, i.e., structures that have a shape and are arranged at the protrusion 9 such that they are capable to increase the density of the substrate 2 faced by the protrusion 9 in function of a penetration depth of the protrusion 9.

[0302] The barbs 24 can be arranged at a distal end of the protrusion 9, as shown in FIG. 10a. This leads to a local compression of the substrate 2 that favours the liquefaction of the thermoplastic material 3 arranged around the distal end of the protrusion 9.

[0303] Alternatively or in addition, the barbs 24 can be arranged at the lateral side of the protrusion 9. As an example, FIG. 10b shows drag down barbs that are small compared to the size of the protrusion 9.

[0304] There is no need for a homogenous distribution of the barbs 24 at the lateral side. Rather, the barbs 24 can be arranged such that the liquefaction of the thermoplastic material 3 sets in at certain positions on the protrusion 9 and/or that the penetration of the substrate 2 by liquefied thermoplastic material is restricted along a specific direction.

[0305] In FIG. 10c, the structure 24 designed and arranged to promote local compression of the substrate 2 is given by the shape of the distal end of the protrusion, in particular by having multiple tips that cause catching of fibers, for example.

[0306] In particular, barbs are suitable for use in fibrous substrates 2 where they can collect fibers during penetration and hence increase the density of fibers around the protrusion 9.

[0307] The barbs can be made of the thermoplastic material 3 or a harder material.

[0308] Barbs made of the thermoplastic material 3 can further increase the embedding of the protrusion 9 and the protruding portion 91, respectively.

[0309] FIG. 11a shows an object 30 that includes anisotropic deformation properties. In other words, the object 30 is more tensible along a first direction than along a second direction. In the embodiment shown, the object 30 includes fibers that are bent along the first direction and stretched along the second direction.

[0310] FIG. 11a further indicates possible engagement location by black points.

[0311] FIG. 11b shows an exemplary fastener 1 that is adapted to the anisotropic deformation properties of the object 30 according to FIG. 11a. The protrusions 9 are arranged on a portion of the fastener body 7, only. Further, the protrusions 9 are arranged relative to each other in a manner that a homogeneous tensioning field along the first direction is generated during the method and after attachment of the object 30 to the substrate 2 by the fastener 1 shown.

[0312] FIG. 12 shows a variation of the method in which the substrate 2 is placed between the fastener 1 and the sonotrode 20.

[0313] According to this variation, any force for advancing the protrusion(s) 9 into the substrate 2 is applied to the fastener 1 (indicated by the arrow below the fastener 1).

[0314] The sonotrode 20 is in contact to the distal surface 14 of the substrate 2 and couples mechanical oscillations into the substrate 2. Further, it acts as a support for the substrate 2, but it does not push actively the substrate 2 towards the fastener 1.

[0315] This arrangement of applying the sonotrode to the substrate 2 and any pushing force to the fastener 1 has the effect that the compressed region 201 is generated around the protrusion(s), wherein the compression of the distal surface 14 of the substrate 2 is kept minimal.

[0316] FIG. 13 shows two stress-strain-curves (A and B) that are representative for the experimental results that led to the surprising finding that various incoherent materials are suitable for use in bonding methods relying on the liquefaction of thermoplastic material by the use of a mechanical pressing force and a mechanical excitation, in particular vibrations.

[0317] The relative behaviour of stress-stain curves A and B shows the influence of a changing surface via which load is applied to the material. The indenter of curve B has a larger surface area in contact with the material that the indenter of curve A.

[0318] FIG. 13 shows the observed first region in which the stress depends approximately linear on strain, the observed transition region and the observed second region in which the stress depends approximately linear on strain.

[0319] The straight lines that approximate the approximately linear dependence in the different regions of linear dependencies are represented as dashed lines.

[0320] The strain ε.sub.c at which the slope of the first region of approximately linear dependency and the slope of the second region of approximately linear dependency cross is a characteristic value of the stress-strain behaviour of the material. The characteristic value can be used to define a minimal compression needed in embodiments of the method in which the positive-fit connection is to be established in a substrate material that does—when not compressed—not generate the stress needed for liquefaction of the thermoplastic material.

[0321] FIG. 14 shows an exemplary embodiment of a fastener 1 including a tension structure 100.

[0322] The exemplary embodiment shows a fastener 1 in the shape of a fixation ring including at its distal side an outer ring of protrusions 9, this means of fixation protrusions, and an inner tension ring 100.

[0323] The embodiment of FIG. 14 is a variant of the embodiment shown in FIGS. 6a, 7 and 8, wherein the fixation protrusions 9 are the protrusions 33 of the first kind arranged as the outer ring on the fastener body and the tension ring 100 is a protrusion 34 of the second kind arranged as an inner ring on the fastener body.