DE102012001859B4 - Connecting arrangement and method for connecting at least one first component of a carbon fiber reinforced composite material with at least one second component - Google Patents

Abstract

Connecting arrangement of at least one first component (12, 16) made of a carbon fiber reinforced composite material with at least one second component (14, 36), which has at least on its outside a metal which is electrochemically base than carbon, with protection against electrochemical contact corrosion is provided wherein as protection against contact corrosion between the at least one first component (12, 16) and the at least one second component (14, 36) a separating component (34) is arranged, which in contact with the at least one first component (12, 16) a greater resistance to contact corrosion than the at least one second component (14, 36), characterized in that the separating member is formed as an electrically non-conductive ceramic element (34).

Description

The invention relates to a connection arrangement of at least one first component made of a carbon fiber reinforced composite material having at least one second component, which has at least on its outer side a metal which is electrochemically base than carbon, with protection against electrochemical contact corrosion is provided. Furthermore, the invention relates to a method for connecting at least one first such component with at least one second such component.

In the course of lightweight construction efforts in the car industry increasingly carbon fiber reinforced composite materials are used. Such components made of carbon fiber reinforced plastics are characterized by a high electrical conductivity and a noble electrochemical potential. In terms of corrosion, therefore, behave components made of a carbon fiber reinforced composite material such as components made of an electrochemically noble metallic material, such as copper components.

Electrochemically, the carbon in the carbon fiber reinforced composite is more noble than the metal of the second component of the joint assembly. This can lead to electrochemical contact corrosion on the side of the second, metallic component if the first component and the second component are in direct contact with one another and if there is a conductive electrolyte at the connection point. The prerequisite for contact corrosion is that two electrically conductive materials with different electrochemical potential touch each other and moisture. is present. The location of the electronically conductive connection of the components may in this case be quite different from the location touched by the electrolyte.

The electrochemically less noble material of the connection arrangement, that is to say the metal present at least on the outside of the second component, is then accelerated as a result of contact corrosion, this process representing the anodic partial reaction.

Such a contact corrosion can occur, for example, if a direct contact of the component made of the carbon fiber reinforced composite material with the second component, which is formed of an electrochemically base material such as an aluminum alloy. However, the contact between the carbon fiber reinforced composite material and a second component, which has a base corrosion protection layer - for example, a zinc-nickel coating - may occur and lead to contact corrosion in the presence of moisture. Such base corrosion protection layers are used, for example, as corrosion protection of steel screws.

The actual risk of contact corrosion depends not only on the potential difference but also on the electrochemical behavior of the two contact partners, the conductivity of the present, conductive medium and on the geometric design of the components, in particular in the vicinity of the contact area in contact with the electrolyte. The extent of the contact corrosion is also dependent on the kinetics of the anodic and cathodic partial reactions and the area ratio of the base material, in the contact corrosion of the anode, and the nobler material, ie the cathode.

As a protection against electrochemical contact corrosion, it is known from the prior art to laminate the carbon fiber reinforced component in the joining region with a glass fiber reinforced layer prior to bonding to the second component. This is electrically non-conductive, so that the contact corrosion is prevented.

However, such a method of laminating the carbon fiber reinforced composite member with a fiberglass sheet is very expensive.

The DE 10 2007 003 277 A1 describes a rigid body of an aircraft, which has a frame formed of metallic frames, which frame is provided with an outer panel of carbon fiber reinforced composite components. The composite components comprise an outer skin and an inner skin of a CFRP material, between which a composite core element is arranged. As a result, the component is ventilated, and water accumulation in its interior are avoided. Furthermore, such a two-shell construction acts as a heat-insulating, so that a condensation of water inside the fuselage of the aircraft is prevented. This can reduce the amount of protection against the occurrence of corrosion.

This type of protection against electrochemical contact corrosion is associated with a comparatively large manufacturing effort.

From the DE 10 2007 003 276 A1 For example, a connection element for fastening aircraft components in a CFRP-metal hybrid construction is known, which is formed from an electrically non-conductive material such as a fiber-reinforced plastic.

From the DE 10 2006 060 552 A1 It is known to galvanically separate stainless steel components and components from other metals or CFRP.

From the DE 603 03 783 T2 It is known to connect metal components and CFRP composite components with washers made of insulating material and titanium screws.

Object of the present invention is therefore to provide a connection assembly and a method of the type mentioned, which or which easily prevents the risk of contact corrosion.

This object is achieved by a connection arrangement having the features of patent claim 1 and by a method having the features of patent claim 8. Advantageous embodiments with expedient developments of the invention are specified in the dependent claims.

In the connection arrangement according to the invention is provided as protection against contact corrosion between the at least one first component and the at least one second component, a separating member made of an electrically non-conductive ceramic element, which has a greater resistance to contact corrosion in contact with the at least one first component than the at least one second component. Due to the separating component, which can be arranged between the two before joining the first component to the second component, incompatible components are separated from one another with regard to the contact corrosion. Thus, the risk of contact corrosion is reduced or eliminated.

The less susceptible to contact corrosion separation component namely prevents direct contact of the noble surface of the first, formed from the carbon fiber reinforced composite component with the other, less noble metallic surface of the second component. Even if contact corrosion occurs due to contact of the first member with the second member at a location not provided with the partition member, the ion current flowing over the conductive electrolyte of the moisture film must travel a path which is particularly long due to the presence of the partition member , This is accompanied by a higher resistance and thus a lower ion current, so that even in the unlikely event of contact corrosion this is reduced or slowed down.

The abovementioned effects of the separating component are particularly evident if, according to an advantageous embodiment of the invention, the separating component is larger than a region in which the at least one first component and the at least one second component overlap one another in a connecting direction of the components. Then namely a particularly extensive separation of the first component is achieved by the second component.

The separating component is formed according to the invention as an electrically non-conductive ceramic element. Such a ceramic material used for the separating component leads to a complete electrical separation between the first component and the base metal surface of the second component. As a result, the contact corrosion can be completely prevented.

According to an advantageous embodiment of the invention, such a ceramic element may comprise a framework formed of ceramic particles, which is embedded in a matrix which has greater plastic deformability than the framework. When a pressurization of such a ceramic element, the pressure is particularly well passed through the contact of the ceramic particles with each other and distributed. In addition, the matrix, which is plastically easier to deform than the framework ensures that the ceramic element is not too brittle and thus withstand mechanical stresses, especially bending stresses particularly well.

The matrix prevents movement of the ceramic particles under load or pressure, so that the material structure of the ceramic element nevertheless has a particularly high strength. In particular, when the ceramic particles are in close contact with each other and are interlocked with each other, distribution of the pressure acting on the ceramic element under a load, for example by tightening a screw, can be achieved particularly well. Such ceramic elements formed from ceramic and arranged in a matrix particles may also be referred to as ceramic composite elements.

In particular, when a screw passes through the first component as the second component, there is a risk that moisture will penetrate into a gap between a shank of the screw and the wall of a passage opening through which the screw is passed.

This can be counteracted according to a further advantageous embodiment of the invention in that the separating component is provided with a coating formed from an electrically non-conductive material. This coating then penetrates when tightening the screw in the gap and close this one. The coating can in this case in particular be formed from a plastic, for example from a polyamide such as nylon.

Additionally or alternatively, microencapsulated sealing materials may be provided. The separating component can therefore be provided with hollow bodies which are filled with a material designed to seal gaps. For example, hollow bodies formed of a thin plastic material may include an adhesive or the like, and upon the release of the adhesive from the hollow bodies as a result of the pressurization upon connection of the first component to the second component, the adhesive exits and penetrates the gaps.

The at least one second component may be formed as a connecting element, for example as a screw. Such a screw may be formed from an aluminum alloy or formed as a steel screw, which is provided with a corrosion protection layer. In such a connection arrangement, the risk of contact corrosion between the connecting element and the first component is avoided by the separating component in a particularly simple and secure manner.

The at least one second component can also be designed as a component formed from an aluminum alloy, which component is connected to the at least one first component by means of at least one connecting element. Again, the separating component ensures in a simple and safe way that a contact corrosion between the aluminum component and the first component is avoided.

Preferably, the first component and the second component are designed as motor vehicle components. In this case, the separating component ensures in a particularly advantageous manner that the motor vehicle components exposed to the weather are not affected by accelerated contact corrosion.

In the method according to the invention for connecting at least one first component of a carbon-fiber-reinforced composite material with at least one second component, which has a metal at least on the outside, which is less noble than carbon electrochemical, protection against electrochemical contact corrosion is provided. In this case, as a protection against contact corrosion between the at least one first component and the at least one second component, a separating member made of an electrically non-conductive ceramic element is arranged which has a greater resistance to contact corrosion on contact with the at least one first component than the at least one second component , The fact that the separating member can be selectively introduced between the first component and the second component and easily replaced, for example, in case of damage by an undamaged separating component, provides the separating component in a particularly simple manner for an efficient reduction of the risk of contact corrosion.

The advantages and preferred embodiments described for the connection arrangement according to the invention also apply to the method according to the invention and vice versa.

The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of the figures and / or in the figures alone can be used not only in the respectively specified combination but also in other combinations or in isolation, without the scope of To leave invention.

Further advantages, features and details of the invention will become apparent from the claims, the following description of preferred embodiments and from the drawings, wherein identical or functionally identical elements are provided with identical reference numerals. Showing:

1 a prior art connection arrangement of two CFRP components, which are fixed by means of a screw to each other, wherein the screw has an electrochemically base surface;

2 a connection arrangement according to 1 However, each disposed between a screw head and a nut of the screw and one of the CFRP components, a formed of a titanium material separating element according to the prior art;

3 a connection arrangement according to 2 , wherein as separating components ceramic composite separating elements are provided;

4 a connection arrangement according to the prior art, in which an aluminum component is bolted to a CFRP component;

5 a connection arrangement according to 4 in which, however, according to the prior art formed of a titanium material separating elements between the screw head and the CFRP component on the one hand and between the CFRP component and the aluminum component on the other hand are arranged;

6 a connection arrangement according to 5 in which, instead of the separating elements formed from a titanium material, ceramic composite separating elements are used;

7 a connection arrangement according to the prior art, in which there are gaps between the shank of a screw and a CFRP component;

8th a connection arrangement according to 7 in which, however, formed and coated from a titanium material separating elements ensure sealing of the gap;

9 a connection arrangement according to 8th wherein each of the separating elements are formed as coated ceramic composite separating elements; and

10 a schematic and enlarged detail view of a ceramic composite separating element.

At an in 1 shown connection arrangement 10 is a first CFRP component 12 So a formed from a carbon fiber reinforced or carbon fiber reinforced plastic (CFRP) component by means of a screw 14 with a second CFRP component 16 screwed. The screw 14 may be formed of an aluminum alloy, that is, of an electrochemically less noble material than the carbon of the CFRP components 12 . 16 , The screw 14 However, it can also be formed from a steel which is provided with a corrosion protection layer of an electrochemically less noble material as carbon, so it may for example have a zinc-nickel coating.

Due to the carbon in the CFRP components 12 . 16 These are characterized by a high electrical conductivity and a noble electrochemical potential. For a direct contact between a screw head 18 and the first CFRP component 12 In the case of the additional presence of a conductive electrolyte, it occurs between the screw head 18 and the CFRP component 12 to electrochemical contact corrosion, which in 1 schematically by symbols 20 is illustrated. In a similar way, it can be between a nut 22 and the second CFRP component 16 come to contact corrosion.

To prevent this, are in an in 2 shown connection arrangement 24 , in which also the two CFRP components 12 . 16 through the screw 14 connected to each other, between the screw head 18 and the first CFRP component 12 on the one hand and the nut 22 and the second CFRP component 16 on the other hand, as separating components separating elements 26 introduced, which are formed of a titanium alloy. These dividers 26 form in contact with the CFRP components 12 . 16 quickly a dense, corrosion-protective passive layer of titanium oxide, so that in a contact area between these separators 26 and the CFRP components 12 . 16 no contact corrosion occurs. This situation is in 2 as well as in the following figures by arrows 28 illustrated. Titanium separators are known in the art.

No or at most a slight contact corrosion further occurs in the contact area of the screw head 18 to the in 2 upper separator 26 on the one hand or in the contact area of the nut 22 to the in 2 lower separating element 26 on the other hand. This situation is in 2 as well as in the following figures by arrows 30 illustrated.

The separating elements 26 point perpendicular to the direction of connection of the CFRP components 12 . 16 , what a 2 by a directional arrow 32 is specified, an extension which is greater than the contact area of the screw head 18 or the nut 22 on the dividing elements 26 , As a result, even in the case of contact corrosion, an ion current bound to the presence of a moisture film must travel a particularly long distance. Due to the associated high electrical resistance and the intensity of the contact corrosion is reduced.

At the in 3 shown connection arrangement 24 are only instead of the two formed from a titanium material separating elements 26 (see. 2 ) Separating elements 34 provided, which are formed of a ceramic composite material. Such, electrically non-conductive ceramic separators 34 prevent CFRP components due to their particularly good electrical insulation 12 . 16 opposite the base metal outsides of the screw 14 the contact corrosion particularly effective.

At the in 4 shown connection arrangement 10 according to the prior art is the CFRP component 12 by means of the screw 14 with an aluminum component 36 screwed. Accordingly, not only at the contact points of the screw here 14 with the CFRP component 12 but also between the aluminum component 36 and the CFRP component 12 Contact corrosion occur, which in turn is due to the symbols 20 is illustrated.

At the in 5 shown connection arrangement 24 This occurrence of contact corrosion by the provision of a Titanium material formed separating element 26 between the screw head 18 and the CFRP component 12 on the one hand and by the provision of a further such a titanium alloy formed separating element 26 between the CFRP component 12 and the aluminum component 36 on the other hand avoided. Also this latter separating element 26 is perpendicular to the direction of connection greater than an overlap area of the CFRP component 12 with the aluminum component 36 , Separating elements formed from a titanium alloy are known from the prior art.

An in 5 shown further separating element 26 , which is also made of a titanium material and between the nut 22 and the aluminum component 36 is arranged, can also be omitted, since even at the contact of the aluminum alloy of the aluminum component 36 with the electrochemical base coatings of the screw 14 the occurrence of contact corrosion is not to be feared.

At the in 6 shown connection arrangement 24 is essentially the same structure as in the 5 shown connection arrangement 24 , However, here is between the screw head 18 and the CFRP component 12 a ceramic separator 34 intended. Such can also be used instead of between the CFRP component 12 and the aluminum component 36 arranged separating element 26 be provided, which is formed of a titanium alloy. Again, the more ceramic separator 34 omitted, which between the screw head 22 and the aluminum component 36 is arranged.

At the in 7 shown, also known from the prior art connection arrangement 10 is as according to 4 a CFRP component 12 with an aluminum component 36 by means of a screw 14 connected. Here, however, lies between a shaft 38 the screw 14 and the wall of one through the CFRP component 12 and the aluminum component 36 passed through bore a gap 40 in which moisture can penetrate and thus lead to contact corrosion. This is in 7 through corresponding symbols 20 illustrated.

At the in 8th shown connection arrangement 24 prevent coatings 42 , which on the - formed in this embodiment of a titanium material - separating elements 26 are applied, the penetration of moisture into the gap 40 , Such coatings 42 may be formed of nylon, for example.

Additionally or alternatively, microencapsulation of a sealing material, such as an adhesive, may be provided to prevent moisture from entering the gap 40 to prevent. In this case, hollow body with the seal for the gap 40 be formed filled sealing material, and this on the separating elements 26 arranged hollow bodies release their contents when the screw 14 is attracted. At the in 8th shown connection arrangement 24 are the coated or provided with the microencapsulated sealing material separating elements 26 between the screw head 18 and the CFRP component 12 , between the CFRP component 12 and the aluminum component 36 and preferably also between the nut 22 and the aluminum component 36 arranged to also from this side, moisture from entering the gap 40 to prevent.

In the 9 shown connection arrangement 24 is largely the same as in 8th shown, but here is the between the screw head 18 and the CFRP component 12 arranged separating element as an electrically non-conductive ceramic separator 34 educated. However, here also have the separating elements 34 . 26 the coatings 42 and / or the microencapsulation. However, this can be the case between the CFRP component 12 and the aluminum component 36 provided, formed of a titanium material separating element 26 through a ceramic separator 34 be replaced.

10 schematically shows the (uncoated) ceramic separator 34 in an enlarged detail view. Accordingly, this separating element comprises 34 one made of ceramic particles 44 different size and shape formed scaffold, these particles 44 are in close contact and interlocked with each other. The size of the particles 44 may in particular range from the nanometer range to the micrometer range. The shape can be like in 10 by way of example and schematically shown globular or also be spratzig or polygonal. Such ceramic particles 44 may be formed in particular from different oxides, such as a mixture of aluminum oxides, zirconium dioxide and / or silicon dioxide.

The framework of the ceramic particles 44 may be provided by powder mixtures, which may optionally be provided with a binder, such as a dry resin mixture. The ceramic separating elements 34 For example, they can be provided as disks or as a starting material, which can be round or band-shaped, for example.

In the ceramic composite separator 34 is located in the spaces between the particles 44 a matrix material 46 , which may be formed for example by a viscous and curable resin in the ground state. By a poured or molded body of the particles 44 infiltrated with such a viscous material, the porosity of the separating element 34 be greatly reduced. In this case, for example, liquid resin can penetrate under gravity into the interspaces, wherein the process can be supported by applying a vacuum. This can be done at room temperature or during or after sintering of the particles 44 in an oven.

Additionally or alternatively, as the matrix material 46 a gel in the voids between the particles 44 can be introduced, which may be formed in particular by a sol-gel reaction of nanoparticles, said nanoparticles may consist in particular of silicon dioxide.

A machining of the ceramic particles 44 having greening can be done by sawing and / or drilling. The curing of the matrix material 46 can then be done by applying UV light or heat, such as in an oven. Alternatively, a sol-gel reaction of nanopowders may occur during curing. Finally, the separating element 34 be subjected to a grinding treatment to the surfaces, which are in contact with the components 12 . 16 . 36 and / or the screw head 18 or the nut 22 are, possible to provide plan.

The matrix or the matrix material 46 prevents movement of the particles 44 sideways when the separator 34 For example, from the top with a pressure is applied, which in 10 by a pressure arrow 48 is illustrated. Through the contact points of the particles 44 In addition, the pressure is distributed very well from top to bottom, and the separating elements 34 Hold while tightening the screw 14 applied load stood.

LIST OF REFERENCE NUMBERS

10

joint assembly

12

CFRP component

14

screw

16

CFRP component

18

screw head

20

symbol

22

nut

24

joint assembly

26

separating element

28

arrow

30

arrow

32

arrow

34

separating element

36

aluminum component

38

shaft

40

gap

42

coating

44

particle

46

matrix material

Claims (8)

Connecting arrangement of at least one first component ( 12 . 16 ) of a carbon fiber reinforced composite material with at least one second component ( 14 . 36 ), which has at least on its outer side a metal which is less noble than carbon electrochemical, wherein a protection against electrochemical contact corrosion is provided, wherein as protection against contact corrosion between the at least one first component ( 12 . 16 ) and the at least one second component ( 14 . 36 ) a separating component ( 34 ) is arranged, which in contact with the at least one first component ( 12 . 16 ) has a greater resistance to contact corrosion than the at least one second component ( 14 . 36 ) characterized in that the separating component as an electrically non-conductive ceramic element ( 34 ) is trained. Connecting arrangement according to claim 1, characterized in that the ceramic element ( 34 ) one of ceramic particles ( 44 ) formed framework, which in a matrix ( 46 ) is embedded, which has a greater plastic deformability than the framework. Connecting arrangement according to claim 1 or 2, characterized in that the separating component ( 34 ) is greater than an area in which the at least one first component ( 12 . 16 ) and the at least one second component ( 14 . 36 ) in the connection direction ( 32 ) of the components ( 12 . 16 . 36 ) overlap. Connecting arrangement according to one of claims 1 to 3, characterized in that the separating component ( 34 ) - with a coating formed from an electrically non-conductive material, in particular from a plastic ( 42 ) and / or - is provided with hollow bodies which are filled with a material designed to seal gaps. Connecting arrangement according to one of claims 1 to 4, characterized in that the at least one second component as, in particular formed of an aluminum alloy and / or as provided with a corrosion protective layer steel component formed, connecting element ( 14 ) is trained. Connecting arrangement according to one of claims 1 to 5, characterized in that the at least one second component as formed from an aluminum alloy component ( 36 ) is trained, which by means of at least one connecting element ( 14 ) with the at least one first component ( 12 . 16 ) connected is. Connecting arrangement according to one of claims 1 to 6, characterized in that the at least first component ( 12 . 16 ) and the at least one second component ( 14 . 36 ) are formed as motor vehicle components. Method for connecting at least one first component ( 12 . 16 ) of a carbon fiber reinforced composite material with at least one second component ( 14 . 36 ), which has at least on its outside a metal which is less noble than carbon electrochemical, wherein a protection against electrochemical contact corrosion is provided, wherein as protection against contact corrosion between the at least one first component ( 12 . 16 ) and the at least one second component ( 14 . 36 ) a separating component ( 34 ) is arranged, which in contact with the at least one first component ( 12 . 16 ) has a greater resistance to contact corrosion than the at least one second component ( 14 . 36 ) characterized in that the separating component as an electrically non-conductive ceramic element ( 34 ) is formed.

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