DE102012015183A1 - Permanent and reliable joint formed between fiber-reinforced plastic components of motor vehicle, has rivet sleeve formed of fiber-reinforced plastic, and interlayer insulating layer bonded between components - Google Patents

Abstract

The joint has rivets (6) for connecting two components (2,4) to each other. The rivet has a rivet sleeve (8) and a mandrel (10). The rivet sleeve is formed of a soft, easily deformable plastic material, such that during the setting operation of the rivet only a small setting forces occur, so that delamination of the component (2) is avoided. The rivet sleeve is formed of fiber-reinforced plastic such that the conductive or glass fibers are oriented in the longitudinal direction (14). The interlayer insulating layer (30) is formed and bonded between the components over the entire surface. An independent claim is included for method for forming permanent and reliable joint between fiber-reinforced plastic components.

Description

The invention relates to a joint connection between two components, in particular for a motor vehicle, of which at least one consists of a laminate of fiber-reinforced plastic. The invention further relates to a blind rivet for such a joint connection and a method for forming such a joint connection.

Due to the aspired lightweight construction, especially in the automotive sector, efforts are being made to use fiber composite materials in the motor vehicle which exhibit very good mechanical properties with a low specific weight. In comparison to steel sheets still commonly used in mass production today, such fiber composite materials, for example CFRP components, can be fastened to one another or to other components only with great effort. Due to the high level of automation in the automotive industry, a joining process must allow a high process cycle and, moreover, be fault-tolerant with regard to alignment inaccuracies of the components to be joined.

Proceeding from this, the object of the invention is to enable a joint connection between two components, in particular components for the motor vehicle sector, in which at least one of the components is a fiber composite component.

The object is achieved according to the invention by a joint connection with the features of claim 1.

Preferred developments are laid down in the subclaims. The object is further achieved by a blind rivet and a method for forming such a joint connection according to claims 10 and 11.

The joint connection is formed between a first and a second component, wherein at least the first component is a laminate of a fiber-reinforced plastic. This component is, in particular, a carbon-fiber-reinforced component (CFRP component). The two components are further connected to each other by means of blind rivets, which each have a rivet and a rivet mandrel. The rivet sleeve is formed from a comparatively soft, easily deformable plastic. In particular, the plastic has a lower hardness and thus easier deformation than the fiber-reinforced plastic component. The plastic is chosen such that the Blindniet-setting process no damage to the component made of fiber-reinforced plastic, in particular no so-called delamination occurs.

Investigations have shown that in the blind rivet connection of a laminate component due to the high forces occurring at the rivet setting process at the hole edge of the pre-punched component damage occurs very quickly, in particular a detachment of outer layers of the laminate (delamination), resulting in a total of Damage to the component leads. By the. Choosing a comparatively soft plastic are on the one hand the forces required for the setting process compared to, for example, metallic blind rivets (steel rivets) significantly reduced. In addition, due to the soft material at the edge of the hole, no voltage peaks occur which lead to delamination.

The plastic used here is preferably a thermoplastic, in particular a polyamide. The polyamide 46 (PA 46) has proved to be particularly useful here.

Furthermore, in a favorable manner via the soft sleeve, a seal, so that the rivet joint sealingly connects the components. The sealing effect is achieved by the sleeve by this sealingly nestles during the setting process to the harder components as well as the harder residual mandrel. The blind rivet is also preferably resistant to corrosion.

In the case of motor vehicles, when using CFRP components, conventional metal sheet metal components, for example made of sheet steel or other metallic carrier components, which must be mechanically connected to the CFRP components, are also usually used. In an expedient development, therefore, the joint connection as a hybrid connection between a metal component, in particular steel component, such as a steel sheet, and a fiber-reinforced plastic component (laminate) is formed.

Alternatively to such a hybrid compound, the blind rivet connection described here is expediently also suitable for a joint connection in which both components are made of a fiber-reinforced plastic, in particular of the identical material.

Especially with hybrid compounds, additional problems arise due to the different material properties of the two components. Among other things, the different coefficients of thermal expansion represent problems for a permanent connection. As a result, high alternating forces occur in the longitudinal direction of the blind rivet in the event of temperature changes, which makes special Requirements on the continuous service capability to avoid a release of the blind rivet connection due to this cycling over time.

In a preferred embodiment, it is therefore provided that the rivet sleeve is used made of a fiber-reinforced plastic with a fiber content, for example in the range of 30 to 50%. The fibers are oriented in a preferred embodiment in the longitudinal direction. Through these measures, despite the use of the comparatively soft plastic material, a high strength is achieved in the longitudinal direction, so that the alternating stresses can be reliably absorbed.

Conveniently, the blind rivet, in particular the rivet sleeve is formed electrically insulating. This is of particular importance in particular in the above-described hybrid connections between components made of different materials, in particular when connecting a metal component to a CFRP component. A conductive connection between the two components would in fact lead to corrosion of the metallic component, so that the joint connection would be damaged overall over time.

In order to ensure the electrical separation, non-conductive fibers, in particular glass fibers, are therefore provided in an expedient embodiment as fibers. Because of the usual production method of the rivet sleeves in a thermoplastic injection process, the fibers in the plastic material are distributed substantially the same, so in particular are also at least partially on the outer surface. When using, for example, carbon fibers, these would lead to a certain electrical conductive connection between the two components. Due to the manufacturing process by means of thermal spraying also takes place at the same time the preferred orientation of the glass fibers in the longitudinal direction of the rivet.

Due to the soft, for example, in comparison to steel rivet rivet, the trained Blindnietverbindung for receiving only relatively low shear or shear forces acting perpendicular to the longitudinal direction formed. However, this is particularly critical in motor vehicles, for example, in terms of a required crash safety. Therefore, it is provided in a preferred development that the Blindnietverbindung the two parts to be joined is supplemented by an adhesive compound. In particular, the two components are glued together over their entire surface. Therefore, an intermediate layer of an adhesive is expediently arranged over the entire surface between the two components.

Overall, therefore, it is generally provided that an intermediate layer is formed between the components, which is in particular also electrically insulating. As already stated, a direct contact connection between a CFRP component and a metallic component is critical due to the associated corrosion problems. This intermediate layer is preferably formed as the adhesive layer. By using a glass-fiber reinforced plastic rivet sleeve with such an adhesive interlayer, therefore, a high-strength and permanently resistant joint connection is formed, in particular in a hybrid connection between components of different materials, which can also be formed in a series production process without damaging the sensitive laminate component.

In order to enable a reliable joining, especially in a series production with high cycle speed, the components are pre-punched before the formation of the rivet, wherein a respective pair of holes, so two associated holes in the two components, are aligned with each other. Since in any case a hole offset between these two holes of the hole pair is to be avoided, otherwise the rivet connection can not be reliably made of high quality, for a reliable setting process, the one hole has a larger hole diameter than the second hole of the hole pair. Deviations from the axis-parallel alignment of the two holes to each other are therefore compensated by the enlarged diameter, without the blind rivet runs obliquely and not parallel to the axis.

In addition, it is further provided that a thus formed radial clearance between a hole edge of the larger hole and the rivet sleeve is filled with adhesive. The rivet sleeve preferably covers with its setting head the larger hole, so that the free space is covered upwards by the latter. The free space is preferably completely filled with adhesive. An excess adhesive preferably penetrates into a possibly existing intermediate space between rivet sleeve and the second component, so that in addition an improved sealing is achieved. Such, adhesive-supported blind rivets, for example, from the DE 10 2008 026 356 A1 refer to.

In the joint connection, therefore, the two components are preferably both bonded together over the entire surface and, in addition, the radial clearance formed is filled with adhesive.

The adhesive is in particular a thermosetting adhesive.

Nowadays, in the production of motor vehicle components, the procedure is usually such that the entire body is immersed in a bath for applying a protective lacquer, namely in a so-called cathodic dip bath (cathodic dip coating). In this bath, a temperature in the range of about 180 to 190 ° C prevails. The body is immersed in it for about half an hour.

The blind rivet must be suitably temperature resistant in order to withstand this load, d. H. the blind rivet is temperature resistant and has a heat resistance of at least 190 ° C for at least 0.5 hours.

To form the joint connection, therefore, the adhesive is first applied in particular as an intermediate layer between the two components, the components are superimposed and then the blind rivets are set. In the next process step, the component compound prepared in this way is subjected to a temperature treatment to cure the adhesive and, in particular, immersed in the cathodic dip bath. Curing thus preferably takes place in the cathodic dip bath. The blind rivets, via which the two components are connected to each other, therefore serve in particular also for fixing the two components together until the adhesive has cured.

In addition, the blind rivets also contribute in finished joint connection to the strength of the joint connection. This applies in particular to the forces occurring in the axial direction, ie perpendicular to the component surfaces. The forces parallel to the connecting plane between the two components are usually already very well received via the adhesive bond. Especially since the CFRP components have as laminate components impregnated with plastic resin tissue, which is preferably in all directions in the same way resilient.

The rivet mandrel preferably has increased strength compared to the rivet sleeve. In particular, it is made of stainless steel. Basically, a rivet mandrel made of steel can be used. However, under certain circumstances there is the problem of corrosion, especially at the breaking point of a residual mandrel after the setting process.

In a preferred development of the blind rivet is generally designed such that the largest possible contact surface are formed both on the sides of the setting head and on the sides of the closing head to keep the surface pressure per unit area low, to avoid damaging the CFRP component as possible.

In an expedient embodiment, it is provided for this purpose that the wall of the rivet sleeve to be deformed via the mandrel head is comparatively large. Thus, a comparatively thick-walled rivet sleeve is used to form the widest possible closing head. The comparison refers here to conventional steel rivets. In particular, it is provided that the wall thickness of the rivet sleeve in comparison to the diameter of the mandrel is very large and, for example, at least 70% of the diameter of the mandrel and beyond, for example, greater than the diameter of the residual mandrel.

The object is further achieved by a blind rivet for such a joint connection. For this purpose, the blind rivet preferably comprises a rivet sleeve made of a plastic reinforced with non-conductive fibers and a stainless steel rivet mandrel, wherein the wall thickness of the rivet sleeve corresponds to at least 0.7 times and preferably at least 1 times the diameter of the rivet mandrel. Such a trained blind rivet is particularly suitable for the connection of components in which at least one component consists of a fiber-reinforced plastic, on the one hand to avoid damage (delamination) of this component and on the other hand form a permanently reliable joint connection. This applies in particular to a hybrid connection between components of different materials (metal / CFRP component).

The object is further achieved by a method for forming such a joint connection. In principle, the pre-punched components are brought one above the other to form the joint connection, so that the holes of a respective hole pair are aligned with one another. Subsequently, the blind rivets are placed in a respective pair of holes. In this case, the method preferably has the features of claim 11.

To form the joint connection according to claim 11, the procedure is such that the curable adhesive is applied to at least one of the components over its entire surface over its entire surface. Subsequently, the second component is positioned as accurately positioned as possible to the first component, so that the holes for the blind rivets are aligned as possible. Then the blind rivets are inserted into the respective through holes and set. For this purpose, it is pulled with the aid of a setting tool on the rivet mandrel in the longitudinal direction, so that the mandrel head is pulled into the rivet sleeve and this is thereby formed to form the closing head. The rivet mandrel travels on reaching a predetermined setting force at a predetermined breaking point, which is usually arranged in the interior of the rivet, so that a residual mandrel in the rivet remains. Subsequently, the assembled components, which may in particular also be the subject of a complex component, for example an entire body, immersed in a hot cathodic dip bath and subjected there to a paint job. In this treatment, the thermosetting adhesive cures completely between the components to be joined.

The setting process is automated, in particular fully automatic, for example, within a production line and with a blind riveting robot (as he, for example, in WO2006 / 056255 A1 described), which automatically moves to the required position and fully automatically performs the setting process embodiments of the invention will be explained in more detail with reference to the figures. These show each in schematic representations:

1 a joint connection between two components according to a first embodiment and

2 a joint connection between two components according to a second embodiment variant.

The joint connection has in each case at least two components permanently connected to one another, namely a first component 2 , in particular a CFRP component and a second component 4 , in particular a steel component. The two components 2 . 4 are using a blind rivet 6 connected with each other. This includes a rivet sleeve 8th and a rivet mandrel guided in the rivet sleeve 10 , The rivet sleeve 8th even has a setting head 12 on, which is designed in the manner of a flat perforated disc and to the longitudinal direction 14 a sleeve shaft 16 followed. The diameter d1 of the setting head is preferably significantly larger, in particular by more than a factor of 2 than the diameter d2 of the sleeve shaft in order to achieve the largest possible contact surface and thereby the surface pressure force on the setting head in the exemplary embodiment 12 facing CFRP component 2 keep as low as possible.

The rivet sleeve 8th consists of a comparatively soft plastic material, in particular polyamide 46 , The plastic is fiber-reinforced and contains glass fibers 18 , preferably in the longitudinal direction 14 are oriented. This achieves the rivet sleeve 8th a very high tensile strength in the longitudinal direction 14 , The glass fibers are at least in the area of the sleeve shaft 16 in the initial state (not shown) before the actual setting and forming process of the blind rivet 6 preferably exclusively in the longitudinal direction 14 oriented.

In the rivet sleeve 8th is centrally a rivet thorn 10 taken, which has a broadened thorn head 22 and a subsequent mandrel shaft 24 having. The in the 1 and 2 shown joint connections show the set state in which the mandrel head 22 after the actual setting process already in the rivet sleeve 8th is retracted. During setting process, the rivet mandrel 10 using a setting tool upwards in the longitudinal direction 14 in the rivet sleeve 8th retracted, leaving these at the bottom of the two components 2 . 4 is deformed and a closing head 26 formed. Upon reaching a predetermined tensile force travels the mandrel shaft 24 at a predetermined breaking point 28 preferably dimensioned to be within the rivet sleeve 8th is arranged.

The rivet thorn 10 In this case, it is preferably made of metal, in particular a corrosion-resistant metal. such as stainless steel. As a result, corrosion problems in particular at the predetermined breaking point 28 avoided. By using a rivet sleeve in comparison to the material 8th significantly higher-tensile material (metal, stainless steel) also has the advantage that the overall strength of the blind rivet is improved, in particular the Scherzugfestigkeit. Because of the soft plastic material of the rivet sleeve, this has only a low shear tensile strength in the transverse direction perpendicular to the longitudinal direction 14 on. At the same time is the use of a high strength material for the rivet mandrel 20 uncritical with regard to the load on the CFRP component during the setting process, since only the rivet sleeve 8th on the CFRP component 2 immediately applied.

Overall, the setting forces are due to the use of the plastic rivet sleeve 8th especially compared to steel rivets low, so that a comparatively gentle rivet setting process takes place, so that damage to the surface of the CFRP component 2 , in particular a so-called delamination, is avoided.

In the case of the hybrid connection between the CFRP component shown here 2 and the steel component 4 is the CFRP component 2 preferably to the setting head 12 oriented. Basically, this can also be the closing head 26 be oriented. However, due to the deformation of the rivet sleeve occur here 8th other forces, so that the risk of delamination is greater here.

As an alternative to the illustrated hybrid connection, both components exist 2 . 4 made of a fiber-reinforced plastic. Overall, therefore, is the rivet sleeve 8th sufficiently soft and also chosen with regard to their dimensions such that even on the closing head 26 there is no danger of delamination.

Of particular importance for this is the lowest possible surface pressure. To these too on the side of the closing head 26 to achieve the formation of a comparatively wide closing head is sought. For this purpose, the wall thickness w of the sleeve shaft 16 chosen significantly larger than commercially available steel or aluminum rivets. This is expressed in particular in that the wall thickness w is at least 0.7 times and preferably at least 1 times the diameter d3 of the mandrel shaft 24 of the rivet thorn 10 equivalent. In the exemplary embodiment, the ratio of w / d3 is about 1.5.

To improve the resistance to shear loads are the two components 2 . 4 additionally glued together over the entire surface. This is between the two components 2 . 4 an intermediate layer 30 formed of adhesive K. This is a thermosetting adhesive.

In the embodiment of 1 show the two components 2 . 4 each set holes 32A . 32B with the same diameter, which are aligned with each other.

In contrast, in the embodiment of the 2 that the setting head 12 facing upper component 2 a larger hole diameter 11 on as the lower the closing head 26 facing slot 32B with a hole diameter 12 , This results in the upper component 2 a radial clearance 34 between the outer jacket of the rivet sleeve 8th and the inner wall of the setting hole 32A , Also this radial clearance 34 is filled with glue, leaving the free space 34 up through the setting head 12 is completed. The adhesive K is preferably complementary in the setting process in a gap between the rivet and the hole edge of the lower setting hole 32B pressed. This is a particularly efficient seal in the longitudinal direction 14 achieved. A seal is already in accordance with the joint connection 1 given due to the relatively soft plastic material of the rivet 8th , which clings to the components almost sealingly.

For the components 2 . 4 these are in particular motor vehicle components, in particular body components. When used in the automotive industry, process-reliable series production is of decisive importance with regard to economic applicability. The blind rivets are therefore preferably set automatically by means of setting tools. To form the joint connection are those with a variety of setting holes 32A . 32B trained components 2 . 4 provided and at least one is coated over the entire surface with the adhesive K. Subsequently, the two components 2 . 4 superimposed, so their holes 32A , B are aligned with each other. The next step will be the blind rivets 6 set, so that the components 2 . 4 already fixed to each other. Finally, the glue is cured. This is preferably done by immersing the components in a coating bath (cathodic dip bath), where the curing of the adhesive takes place due to the temperature of about 180 ° C. prevailing in this bath and thus the final formation of the joint connection.

LIST OF REFERENCE NUMBERS

2

CFRP component

4

Steel member

6

Rivet

8th

rivet sleeve

10

Mandrel

12

setting head

14

longitudinal direction

16

sleeve shank

18

glass fibers

22

mandrel head

24

spike shaft

26

closing head

28

Breaking point

30

interlayer

32A, 32B

insertion hole

34

radial clearance

d1

Diameter setting head

d2

Diameter sleeve shaft

w

Wall thickness / sleeve

d3

Diameter of mandrel shaft

l1

Hole diameter CFK component

l2

Hole diameter steel component

K

adhesive

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008026356 A1 [0019]
• WO 2006/056255 A1 [0032]

Claims (11)

Joining connection between a first and a second component ( 2 . 4 ), in particular for a motor vehicle, wherein at least the first component ( 2 ) is a laminate of a fiber-reinforced plastic, wherein the components ( 2 . 4 ) with the help of at least one blind rivet ( 6 ) and the blind rivet ( 6 ) a rivet sleeve ( 8th ) and a rivet mandrel ( 10 ), wherein the rivet sleeve ( 8th ) is formed of a plastic, such that the forces occurring during Blindnietsetzen not to a delamination of the component ( 2 ) made of fiber-reinforced plastic leads. Joining connection according to Claim 1, in which the second component ( 4 ) is a metal component. Joining connection according to one of the preceding claims, in which the rivet sleeve ( 8th ) consists of a fiber-reinforced plastic, wherein the fibers ( 18 ) longitudinal ( 14 ) of the rivet sleeve ( 8th ) are oriented. Joining compound according to claim 3, wherein as fibers ( 18 ) electrically non-conductive fibers, such as glass fibers are used. Joining connection according to one of the preceding claims, in which the two components ( 2 . 4 ) are additionally glued over the entire surface with the help of an adhesive (K). Joining connection according to one of the preceding claims, wherein the components ( 2 . 4 ) is pre-punched components, wherein by a respective pair of holes of the blind rivet ( 6 ) and the holes ( 32A . 32B ) of the hole pair have different hole diameters (l1, l2), wherein a radial clearance ( 34 ) between a hole edge of the larger hole ( 32A ) and the blind rivet ( 6 ) is filled with adhesive (K). Joining compound according to claim 5 or 6, wherein the adhesive (K) is a thermosetting adhesive. Joining connection according to one of the preceding claims, in which the rivet mandrel ( 10 ) is made of stainless steel. Joining connection according to one of the preceding claims, in which the wall thickness (w) of the rivet sleeve ( 8th ) at least 0.7 times and preferably at least 1 times the diameter (d3) of the rivet mandrel ( 10 ) corresponds. Blind rivet ( 6 ) for a joint connection according to one of the preceding claims, which has a rivet sleeve ( 8th ) of one with non-conductive fibers ( 16 ) reinforced plastic and a rivet mandrel ( 8th ) made of stainless steel, wherein the wall thickness (w) of the rivet sleeve ( 8th ) corresponds to at least 0.7 times and preferably at least 1 times the diameter (d3) of the rivet mandrel. Method for forming a joint according to one of claims 1 to 9, in which the components ( 2 . 4 ) with the introduction of an intermediate layer ( 30 ) are brought together from a curable adhesive (K), then with the help of several blind rivets ( 6 ) are fixed together in particular according to claim 10 and that then the components ( 2 . 4 ) are introduced into a hot cathodic dip bath, so that the adhesive (K) hardens.

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