WO2015135712A1

WO2015135712A1 - Method for joining a steel part to a fiber-reinforced plastic part by means of a connection element

Info

Publication number: WO2015135712A1
Application number: PCT/EP2015/052814
Authority: WO
Inventors: Dr. Sven JÜTTNER; Thomas Grosse; Andreas Fricke; Dr. Klaus DRÖDER
Original assignee: Volkswagen Aktiengesellschaft
Priority date: 2014-03-14
Filing date: 2015-02-11
Publication date: 2015-09-17
Also published as: DE102014204778A1

Abstract

Method for joining at least two parts (10, 11) to be joined by means of at least one connection element (12), wherein a first part (10) to be joined comprises steel and wherein a second part (11) to be joined comprises a fiber-reinforced plastic, wherein the method comprises the following steps: a) arrangement of the two parts (10, 11) to be joined on one another in such a way that they directly contact one another at least in some regions with their two first lateral surfaces (14, 16) or are connected to one another via an adhesive (18) arranged between the two parts (10, 11) to be joined; b) placing the connection element (12) on a second lateral surface (17) of the second part (11) to be joined; c) heating the connection element (12); d) exerting a force (19) on the connection element (12) until at least two arms (13a, 13b) of the connection element (12) have penetrated the second part (11) to be joined and contact the first lateral surface (14) of the first part (10) to be joined; e) welding the connection element (12) to the first part (10) to be joined.

Description

description

Method for joining a steel part with a fiber-reinforced plastic part by means of a

connecting element

The invention relates to a method for joining a steel-containing joining part with a fiber-reinforced plastic-containing joining part by means of a connecting element.

Furthermore, the invention relates to a body part for a motor vehicle and a

Connecting element for joining a steel-containing joining part with a fiber-reinforced plastic-containing joining part.

State of the art

In the development of motor vehicles lighter structures in the body shop are becoming increasingly important. For this purpose, a wide variety of material pairings make diverse possible

Body structures that a motor vehicle despite increasing demands

Make vehicle safety and occupant comfort easier. This requires specially adapted connection techniques for connecting the body parts made of different materials. For example, it is known to produce bodies in mixed construction of steel, aluminum, thermoplastics, magnesium and fiber composites. As fiber composites find fiber-plastic composite (FKV),

or fiber-reinforced plastic, application. For example, in this regard carbon fiber reinforced plastic (CFRP), or carbon, to call.

Steel body panels are commonly joined together using standard welding techniques such as resistance spot welding and MIG welding. Joining technologies for the connection of different material pairings, for example of steel-containing parts with aluminum-containing parts are based on known mechanical and thermal joining methods. For example, it is known to connect steel-containing parts with aluminum-containing parts by means of punch rivets, nails, screws and clinching with each other. These procedures require, in part, the introduction of previous drilling. Furthermore, it is known that steel parts with aluminum-containing parts by additional connecting elements by means of resistance welding together. Again, this is the introduction of

Drilling necessary to insert the fasteners in the aluminum-containing part.

When using such methods for joining steel-containing joining parts with FVK-containing joining parts, the fiber structures of the FVK-containing joining part are at least partially destroyed by the introduction of holes, rivets or screws. Furthermore, multi-stage joining processes, for example due to the previous introduction of holes, make the automation of the manufacturing process more difficult.

DE 100 60 390 A1 describes a stamped riveting method. In this case, a punch rivet is driven through a first material by means of a punch and connected to a second, resting on a die material. After driving the punch rivet through the first material, the die-side material can be selectively heated.

DE 423 7 361 A1 discloses a connection auxiliary part for the resistance-electric

Welding of aluminum sheet on steel described. It is proposed that the shaft end of the connecting auxiliary part as a cutting edge for punching the own

Through opening is formed.

DE 10 2004 025 492 A1 describes a method for joining two joining parts, for example a steel sheet with a light metal sheet or a plastic component, by means of mechanical driving and welding of a joining element. The joining element is designed for this purpose as a rivet or bolt with a cutting edge.

The fifth of the invention: problem, solution

The object of the present invention is to further improve a method for joining a steel-containing joining part with a fiber-reinforced plastic-containing joining part in such a way that the fiber structure is not or only slightly destroyed and the automation of the manufacturing process is further improved. Furthermore, it is an object of the invention, a body part for a motor vehicle

propose, wherein the body part has at least one steel-bearing joining part and a fiber-reinforced plastic-containing joining part and the fiber-reinforced plastic joining part would not or only slightly destroyed when joining the two parts to be joined.

It is another object of the invention, a connecting element for connecting at least two joining parts, wherein the first joining part comprises steel and the second joining part has a fiber-reinforced plastic, to further improve such that through the

Connecting element when joining the two parts joining the fiber-reinforced

plastic-containing adherend is not or only slightly destroyed.

For this purpose, a method for joining at least two joining parts by means of at least one connecting element is proposed according to the invention. A first joining part has steel or is made of steel. A second adherend comprises a fiber reinforced plastic, such as a carbon fiber reinforced plastic. The method according to the invention has the following steps, wherein no compelling sequence of the steps is predetermined by these method steps: a) Arranging the two joining parts together. In this case, the two joining parts are arranged in such a way that a first side surface of the first joining part is at least partially in direct contact with a first side surface of the second joining part or that the two joining parts are connected to one another via an adhesive arranged between the two joining parts; b) placing the connecting element on a second side surface of the second joining part; c) heating the joining element; d) exerting a force on the connecting element until at least two arms of the connecting element have penetrated the second joining part and are in contact with the first side surface of the first joining part; e) welding the connecting element with the first joining part.

By joining the two joining parts, a firm connection between the two parts to be joined, for example, a force and / or positive connection is made. The first Joining part has steel or is made of steel. For example, the first joining part could be formed as a steel sheet. The second joining part has a fiber-reinforced plastic. Preferably, the second joining part consists of a fiber-plastic composite (FRP). A fiber-reinforced plastic is understood as meaning a material consisting of reinforcing fibers and a plastic matrix. The matrix surrounds the fibers, which are bonded to the matrix by adhesive or cohesive forces. This gives the FKV a

Directional elasticity behavior. The first joining part preferably has a carbon fiber-reinforced plastic (CFRP), or carbon, on.

The two joining parts can have any suitable shape. Preferably, the first joining part and / or the second joining part is at least partially flat,

for example, formed as a sheet. For example, the parts to be joined parts of a

Vehicle body, for example, represent a side panel or a roof.

The connecting element has a suitable material for welding. Furthermore, the connecting element according to the invention has at least two arms. The two arms of the connecting element may protrude from a head of the connecting element, or a side surface of the head of the connecting element. The arms are essentially elongated. Under an elongated training is to be understood that the arms have a greater length than maximum width or maximum

Have diameter. The front ends of the arms are designed for connection to the metallic material of the first joining part. Preferably, the front ends of the arms are designed as a connection sflächen. Due to the elongated design of the arms penetrate the arms while exerting a force on the previously heated connecting element, the fiber material of the second joining without destroying it significantly. After the arms of the connecting element have penetrated the second joining part, they are in contact with the metallic material of the first joining part or the first side face of the first joining part with their front ends, or the connecting surfaces. After welding of the connecting element with the first joining part, a welded connection is formed in the region of the connection surface, or in the region of the contact point between the connection part

Connection surface and the first side surface of the first joining part.

For heating the connecting element in step c), a heat source may be provided. Furthermore, the connecting element can be heated inductively in step c). The welding of the connecting element with the first joining part in step e) can be carried out by means of a suitable welding process. be performed for example by means of resistance welding. Furthermore, the connecting element can be welded to the first joining part by inductive heating.

Due to the special design of the connecting element, or the arms of the connecting element, no pre-drilling, in particular no pre-drilling by the fiber-reinforced material, is necessary for the method according to the invention for joining the first joining part to the second joining part. Thus, due to the special design of the connecting element or the arms of the connecting element, the fiber material of the second joining part is only slightly or not destroyed on the one hand. Furthermore, the manufacturing process is easier and less expensive to automate.

Furthermore, it is preferably provided that in step d) a force on the

Is applied connecting element, so that so that the arms of the connecting element, the second joining part can easily penetrate without destroying the fiber material of the second joining part further.

The order of the process steps essential to the invention can vary at least partially. For example, the heating of the invention element in step c) can also be carried out before placing the connecting element on the second joining part in step b). Preferably, the connecting element is heated in step c) before and / or during the application of the force in step d).

Furthermore, it is preferably provided that the connecting element is welded in step e) by means of resistance welding with the first joining part. For this purpose, for applying an electrical voltage, or welding voltage, a first

Electrode of a welding device connected to the first joining part and a second electrode of the welding device connected to the connecting element. Preferably, the second electrode of the welding device is applied to the head of the connecting element. After applying the electrical voltage, the welding current flows over the head of the

Connecting element through the arms of the connecting element and the first joining part. Thus, between the connection surface of the arms and the first side surface of the first joining part is formed a welded joint. Furthermore, in step c), the connecting element is preferably heated prior to the application of the voltage for resistance welding. Thus, the heating of the connecting element in step c) is a separate process step. This is preferably not to be understood as meaning heating by the welding current during welding of the connecting element to the first joining part. The connecting element is thus heated to a predetermined temperature prior to the beginning of the welding.

Furthermore, it is preferably provided that the force in step d) is exerted on the connecting element by means of a welding device. For example, the force can be exerted on the connecting element by means of welding tongs. Thus, preferably no separate pressure means, or no separate

Pressing device, for exerting the force in step d) on the connecting element necessary. The welding device to be used in step e), for example

Welding tongs, thus can also be provided as a pressure device for exerting the force on the connecting element and for pressing the connecting element, or the arms of the connecting element, in the second joining part.

According to the invention, a body part is further proposed for a motor vehicle, wherein the body part has at least two by means of at least one connecting element interconnected joining parts. A first joining part has steel or is made of steel. A second joining part has a fiber-reinforced plastic. According to the invention, the two joining parts of the body part are connected to one another by means of a method described above.

Furthermore, according to the invention, a connecting element for connecting, or joining, at least two joining parts is provided. A first joining part has steel,

or consists of steel. A second joining part has a fiber-reinforced

Plastic, for example, a koh I en stofff se rve rstä rkte n plastic on. The

Connecting element has a head and at least two protruding from the head arms.

Preferably, the connecting element is integrally formed. For example, the connecting element can be produced in one piece from a semi-finished sheet metal in a simple manner by means of a stamping-forming process. The head of the connection selementes forms the upper part of the connecting element. The head is preferably flat. The protruding arms of the

Connecting element are elongated. By this is meant that the arms of the fastener have a greater length than maximum width or maximum

Have diameter. Preferably, both arms essentially have an identical length. The arms of the connecting element are also preferably substantially perpendicular from a side surface of the preferably flat-shaped head of the connecting element. Thus, the arms of the

Connecting element preferably directed vertically from a side surface of the head of the connecting element. Preferably, the transition between the head and the respective arms of the connecting element is arranged at a distance from the outer edge of the head of the connecting element.

Furthermore, it is preferably provided that the arms at their front ends have attachment surfaces for connection to the second joining part. The attachment area of a sleeve preferably corresponds to 20% to 100%, more preferably 30% to 90%, and most preferably 40% to 80%, of the cross-sectional area of the sleeve in the widest range. Furthermore, it is preferably provided that the connection surface is formed flat and thus the arms have no tip and no cutting edge in the region of their front ends.

Preferably, the connecting element has at least three arms. By providing more than two arms, for example, three arms, tilting of the connecting element after placing the connecting element on the second joining part before exerting a force on the connecting element can be avoided. The preferred connecting element with more than two arms thus provides better stability, or safer support on the surface of the second joining part.

Short descriptions of the drawings

The invention is explained below by way of example with reference to preferred embodiments. They show schematically: Figure 1 is a perspective view of two parts to be joined and a connecting element for connecting the two joining parts, and

2a to b a method for joining two parts to be joined by means of a

Connecting element.

Preferred embodiments of the invention

1 shows a perspective view of two adjoining parts to be joined 10, 1 1. The first joining part 10 comprises a metallic material. The second joining part 1 1 has a fiber-reinforced plastic. The two joining parts 10, 1 1 are parts of a

Body part 100. It is shown in Figure 1, only a section.

For connecting the two joining parts 10, 1 1, a connecting element 12 is provided. The connecting element 12 is integrally formed from a suitable material for welding, namely steel. The connecting element 12 has a substantially flat

formed plate-shaped head 13 with a top and a bottom on. From the bottom extending substantially perpendicular to the bottom of the head 13 three arms 13a, 13b, 13c. The arms 13a, 13b, 13c are elongated with a polygonal cross-section. The length 27 of the arms 13a, 13b, 13c corresponds approximately to the thickness of the second joining part 1 1. The width 26 of the arms 13a, 13b, 13c is constant over most of the length 27 of the arms 13a, 13b, 13c. Only in the front end region of the arms 13a, 13b, 13c, the arms 13a, 13b, 13c are bevelled and have a slightly smaller width 26. The front ends of the arms 13a, 13b, 13c form the connection surface 23 for connection to the metallic material of the first joining part 10.

FIGS. 2a and 2b show the individual method steps for joining a first joining part 10 to a second joining part 11. Both FIGS. 2a and 2b each show a plurality of process steps.

As shown in FIG. 2a, the two joining parts 10, 11 are arranged relative to one another in such a way that they are connected to one another via an adhesive 18 arranged between the two joining parts 10, 11. Thus, the respective first side surfaces 14. 16 of the two joining parts 10, 11 are glued to one another via the adhesive 18. After arranging the two joining parts 10. 1 1 to each other, the connecting element 12 is placed on the second side surface 17 of the second joining part 1 1 and the connecting element 12 is heated by a heat source 26. After placing the connecting element 12 on the second side surface 17 of the second joining part 1 1, the connecting element 12 with the attachment surfaces 23 of the arms 13a, 13b, 13c on the second side surface 17 of the second joining part 1 1.

In Figure 2b, the pressed-in in the second joining part 1 1 connecting element 12 is shown. For this purpose, a force 19 was exerted on the connecting element 12 by the welding device 20, namely a welding tongs, until the arms 13a, 13b, 13c penetrated the second joining part 11. The connecting element 12 is in contact with the first side surface 14 of the first joining part 10 with the attachment surfaces 23 of the arms 13 a, 13 b, 13 c.

Due to the special, in particular elongated design of the arms 13a, 13b, 13c and the heated prior to pressing connection element 12 of the fiber-reinforced plastic of the second joining part 1 1 is not significantly damaged.

After pressing the connecting element 12, the connecting element 12 is located with its head 13, or the underside of the head 13, on the second side surface 17 of the second joining part 1 1. Subsequently, a resistance welding is used

Welded connection between the connecting element 12 and the first joining part 10 made. For this purpose, a voltage 25 is applied to the two welding electrodes 21, 22. As a result of the flow of current through the connecting element 12 and the metallic first joining part 10, a welded connection is produced in the contact region between the connecting surfaces 23 of the arms 13a, 13b, 13c and the first side face 14 of the first joining part 10.

Both for pressing the connecting element 12 in the second joining part 1 1 and also for welding, the welding device 20 is used. Thus, no separate devices are necessary for these two process steps. The force 19 for pressing the connecting element 12 into the second joining part 11 is exerted with the welding tongs. For this purpose, the first electrode of the welding gun is placed on the underside of the composite, or on the second side surface 15 of the first joining part 10. Opposite, the second electrode 22 of the welding apparatus 20 is placed on top of the head 13 of the

Attached connecting element 12. The two electrodes 21, 22 are compressed to exert the force 19 on the connecting element 12. LIST OF REFERENCES 0 body part first joining part

second joining part

connecting element

Head of the connecting element a, 13b, 13c Arm of the connecting element First side surface of the first joining part Second side surface of the first joining part First side surface of the second joining part Second side surface of the second joining part Adhesive

force

welder

first electrode

second electrode

bonding surface

heat source

voltage source

Width of the arms

Length of the arms

Claims

claims

1. A method for joining at least two joining parts (10. 1 1) by means of at least one connecting element (12), wherein a first joining part (10) comprises steel and wherein a second joining part (1 1) comprises a fiber-reinforced plastic, the method following Steps comprises: a) arranging the two joining parts (10, 1 1) to one another such that they are in direct contact with each other at least in regions with their two first side faces (14, 16) or via a joining part (10, 11) between the two joining parts (10, 11) ) arranged adhesive (18) are interconnected,

b) placing the connecting element (12) on a second side surface (17) of the second joining part (1 1),

c) heating the connecting element (12),

d) applying a force (19) to the connecting element (12) until at least two arms (13a, 13b) of the connecting element (12) have penetrated the second joining part (11) and in contact with the first side surface (14) of the first joining part (10), e) welding the connecting element (12) to the first joining part (10).

2. Method according to claim 1,

characterized,

the connecting element (12) is heated in step c) before and / or during the application of the force (19) in step d).

3. Method (100) according to claim 1 or 2,

characterized,

in step e), the connecting element (12) is welded to the first joining part (10) by means of resistance welding, a first electrode (21) of a welding device (20) being connected to the first joining part (10) for applying an electrical voltage and a second electrode (22) of the welding device (20) with the

Connecting element (12) is connected

4. Method (100) according to claim 3,

characterized, in that the connecting element (12) is heated in step c) before the voltage for welding is applied in step e).

5. Method (100) according to one of the preceding claims,

characterized,

that the force (19) in step d) by means of a welding device (20) on the

Connecting element (12) is exercised

6. body part (100) for a motor vehicle, wherein the body part (100) at least two by means of at least one connecting element (12) interconnected joining parts (10, 1 1), wherein a first joining part (10) comprises steel and wherein a second joining part (1 1) comprises a fiber-reinforced plastic

characterized,

that the two joining parts (10, 1 1) by means of a method according to one of

previous claims have been linked together.

7. connecting element (12) for connecting at least two joining parts (10, 11), wherein a first joining part (10) comprises steel and wherein a second joining part (11) comprises a fiber-reinforced plastic,

characterized,

in that the connecting element (12) has a head (13) and at least two arms (13a, 13b) protruding from the head (13).

8. connecting element (12) according to claim 7,

characterized,

the connecting element (12) has at least three arms (13a, 13b, 13c).

9. connecting element (12) according to claim 7 or 8,

characterized,

the arms (13a, 13b) have at their front ends a connection surface (23) for connection to the second joining part (11).