The invention relates to a connection arrangement between a fiber-plastic composite profiled part and a vehicle body frame part.
The invention furthermore relates to a method for producing such a connection arrangement and to a preferred use in motor vehicle manufacturing.
In motor vehicle manufacturing and, in particular, in vehicle body manufacturing, use is increasingly made of lightweight construction materials. These also include fiber-plastic composites, such as, for example, CFRP and GFRP. In addition to flat components, use is increasingly also being made of profiled components formed from a fiber-plastic composite (FPC) (referred to below as fiber-plastic composite profiled parts). Diverse connection arrangements for the insertion or attachment of a fiber-plastic composite profiled part into or to a vehicle body frame structure are known from the prior art. Regarding the prior art, reference is made to patent documents DE 10 2013 002 365 B3, DE 10 2012 112 313 A1 and DE 10 2010 053 843 A1.
The invention is based on the object of providing a connection arrangement of the relevant type which does not have at least one disadvantage associated with the prior art or has said disadvantage at least only to a reduced extent.
This and other objects are achieved by a connection arrangement, a method for producing the connection arrangement, and a preferred use of the connection arrangement according to embodiments of the invention.
A connection arrangement according to the invention between a fiber-plastic composite profiled part and a vehicle body frame part comprises a connector in the form of an intermediate piece which is connected to the vehicle body frame part and has a connection portion which is plug-connected and adhesively bonded to an end of the fiber-plastic composite profiled part, wherein the end of the fiber-plastic composite profiled part is plugged onto the connection portion of the intermediate piece and is adhesively bonded on the inner surface, i.e. on the inner circumferential surface thereof, to the connection portion.
The fiber-plastic composite profiled part and the vehicle body frame part also, in particular, belong to the connection arrangement according to the invention. To this extent, a connection arrangement according to the invention could also be referred to as a component composite.
Unlike the connection arrangements known from the prior art, the intermediate piece, which may also be referred to as attachment piece or adapter, is not plugged with its connection portion or plug-in connection portion onto the end of the fiber-plastic composite profiled part, but rather into same, for which purpose the intermediate piece or the connection portion thereof is correspondingly designed. The adhesive connection exists between the surface portions, which lie flush against one another in an overlapping region, on the outer side or outer circumferential surface of the plugged-in connection portion and the inner side or inner circumferential surface at the open end of the plugged-on fiber-plastic composite profiled part. These surface portions may also be referred to as adhesive surfaces. The direct adhesive connection between the joining partners is thereby very readily protected against external effects. In addition, a highly attractive appearance is produced. Furthermore, advantages arise in the case of the adhesive joining, as is explained in more detail below.
The intermediate piece is preferably formed from a metallic material, preferably from an aluminum or steel material. The intermediate piece can be a forged part, sheet-metal shaped part or cast part, in particular a die cast part. Similarly, the intermediate piece can also be a profiled part formed in particular from aluminum or steel material. It is preferably a continuously cast or extruded profiled part which is cut to size and can be designed, for example, as an open profile (for example as a U profile) or as a closed hollow profile or tubular profile. The intermediate piece is preferably produced integrally (i.e. in one piece), wherein a multi-piece configuration (for example as a welded part) is also possible.
The vehicle body frame part is, in particular, a sheet-metal shaped part, a cast part, a (metallic) profiled part or the like which is formed in particular from an aluminum or steel material. The vehicle body frame part is preferably a hot-formed and, in particular, press-hardened sheet-metal shaped part which accordingly has high material strength. The vehicle body frame part is preferably part of a motor vehicle body and is accordingly inserted into a primary vehicle body structure or vehicle body frame structure. The intermediate piece can be joined in an integrally bonded and/or form-fitting manner to the vehicle body frame part, for example by welding, screwing, riveting or the like, for which purpose the intermediate piece is preferably formed with a suitable connection portion, for example in the form of a welding, screwing or riveting flange. An integral formation of the intermediate piece with the vehicle body frame part is also possible, for example in such a manner that the intermediate piece is integrally formed directly on the vehicle body frame part by forming or primary forming.
The fiber-plastic composite profiled part can be designed as an open profile (or as what is referred to as a half profile), for example as a U profile. The fiber-plastic composite profiled part is preferably designed as a tubular hollow profile (or as what is referred to as a full profile). The fiber-plastic composite profiled part can have a three-dimensional shaping and can be curved or shaped in some other way along its axial longitudinal extent, for example. The fiber-plastic composite profiled part is preferably designed with constant cross sections along its axial longitudinal extent.
It is preferably provided that the outer cross section of the connection section of the intermediate piece does not fully correspond with the inner cross section of a fiber-plastic composite profiled part, designed in particular as a hollow profile, as the result of which, outside the surface portions (on the outer circumferential surface of the plugged-in connection portion and on the inner circumferential surface at the end of the plugged-on fiber-plastic composite profiled part) which lie flush against one another in the overlapping region and are also at least partially adhesively bonded to one another, there are free-running zones or clearances which permit different thermal expansions of the intermediate piece or of the connection portion thereof and of the fiber-plastic composite profiled part transversely with respect to the longitudinal direction or plug-on direction.
The connection portion of the intermediate piece can be designed with at least one plug-in slope or introduction slope which permits simple and damage-free insertion into the open end of the fiber-plastic composite profiled part or plugging of the fiber-plastic composite profiled part onto the connection portion of the intermediate piece. A plug-in slope can be formed, for example, by sharpening or beveling the connection portion of the intermediate piece.
In a particularly preferred development of the invention, the plugged-on fiber-plastic composite profiled part is secured or tightly screwed with at least one flow-hole-forming screw to the connection portion of the intermediate piece. The connection between the fiber-plastic composite profiled part and the intermediate piece therefore takes place by adhesive bonding and by screwing to the end plugged onto the intermediate piece by use of at least one flow-hole-forming screw or flow hole screw screwed in in the overlapping region.
The flow-hole-forming screw which is used preferably has a screw head and a screw shank, wherein the screw shank is formed with a self-forming threaded portion and a flow-hole-forming portion arranged upstream thereof. Flow-hole-forming screws of this type are known from the prior art (see, for example, DE 39 09 725 C1), but have not been used until now for the purpose mentioned. This development of the invention therefore also extends to the new use of at least one flow-hole-forming screw for a corresponding connection arrangement and/or for producing a corresponding connection arrangement.
In an advantageous manner, the use of a flow-hole-forming screw permits non-cutting direct joining without pre-punching or other preparation of the intermediate piece and, in particular, also without pre-punching of the fiber-plastic composite profiled part. As a result, in particular in comparison to other mechanical joining means and joining methods (such as, for example, riveting or conventional screwing), outlays are reduced and cycle times reduced during the production of a connection arrangement according to the invention. Considerable cost advantages are therefore achievable especially in series manufacturing. In addition, a joining or screw connection produced with a flow-hole-forming screw can be subjected to a very high load and is releasable again (for example for carrying out repairs). In addition, the screwing-in of a flow-hole-forming screw can be automated very readily. Furthermore, advantages are also afforded in respect of the corrosion tendency. This is not an exhaustive list of the advantages which are associated with the use of flow-hole-forming screws.
The method according to the invention for producing a connection arrangement according to the invention comprises at least the following acts:                providing a fiber-plastic composite profiled part and an intermediate piece which is formed in particular from metal and has a connection portion, wherein the fiber-plastic composite profiled part and the intermediate piece can be designed in accordance with the explanations above and/or below and wherein it is provided in particular that the intermediate piece is already connected to a vehicle body frame part;        applying an adhesive (wherein it is, in particular, what is referred to as a structural adhesive) to the relevant surface portions (i.e. to the corresponding adhesive surfaces in an overlapping region to be produced) on the outer circumferential surface of the connection portion of the intermediate piece and/or on the inner circumferential surface at the open end of the fiber-plastic composite profiled part;        optionally slightly curing the adhesive;        plug-connecting the intermediate piece to the fiber-plastic composite profiled part by plugging the connection portion into the open end of the fiber-plastic composite profiled part or by plugging the fiber-plastic composite profiled part onto the connection portion of the intermediate piece, wherein, after the plugging-in or plugging-on, a large compensation of tolerances in the plug-on direction or longitudinal direction of the profiled part is made possible; and        carrying out a heat treatment in order to cure the adhesive, wherein the surface portions or adhesive surfaces which lie flush against one another in the overlapping region and are provided with adhesive are pressed against one another because of the relatively great thermal expansion of the intermediate piece formed in particular from metal.        
Accordingly, the method according to the invention makes use of the circumstance, which is disadvantageous per se, that the metal material of the intermediate piece has a higher or more pronounced thermal expansion upon heating than the fiber-plastic composite material of the profiled part. By the end of the fiber-plastic composite profiled part being plugged onto the connection portion of the metallic intermediate piece, the intermediate piece is pressed virtually from the inside against the inner circumferential surface of the fiber-plastic composite profiled part at the adhesive surfaces or contact surfaces in the overlapping region upon heating, thus producing a particularly intimate and firm adhesive connection. The above-explained free-running zones have also proven particularly advantageous here, as a result of which critical material stresses can be prevented during the heat treatment.
The heat treatment can be carried out, for example, by use of a furnace or an inductive heating system. The heat treatment and the curing of the adhesive preferably take place in a drying cycle following cathodic dip coating, i.e. within the scope of a CDC process.
It is preferably provided that the fiber-plastic composite profiled part is tightly screwed with at least one flow-hole-forming screw to the intermediate piece after the plug-connection and prior to the heat treatment, wherein the tight screwing preferably takes place without pre-punching of the intermediate piece and, in particular, also without pre-punching of the fiber-plastic composite profiled part (what is referred to as direct screwing). For this purpose, reference is made in particular also to the explanations above in this regard. The placing or screwing-in of the flow-hole-forming screw preferably takes place in an automated manner. The placing of at least one flow-hole-forming screw serves, in particular, also for the temporary securing of the joining partners until the adhesive has cured.
A connection arrangement according to the invention is preferably used on a motor vehicle body for the attachment of a roof bow in the form of a fiber-plastic composite profiled part to a roof frame. The fiber-plastic composite profiled part forming the roof bow can be designed in accordance with the explanations above and/or below. The intermediate piece belonging to the connection arrangement can be welded, screwed, riveted or connected in another suitable manner to the roof frame. Particularly preferably, it is provided that the intermediate piece is formed integrally with a vehicle body frame part (for example a roof longitudinal member or the like) forming the roof frame or belonging to the roof frame. The vehicle body frame part is preferably a heat-formed and, in particular, press-hardened sheet-metal shaped part.
The invention therefore extends, at least indirectly, also to a motor vehicle body and/or to a vehicle body frame structure with at least one roof bow which is designed as a fiber-plastic composite profiled part and is fastened at least on one side and, in particular, on both sides, i.e. at both of its axial ends, to a roof frame or the like by way of a connection arrangement according to the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.