Method for connecting hollow profiles

Abstract

A method is provided for connecting hollow profiles (1-4) in a joint (10) to produce a load-bearing structure (5). The method includes placing ends of hollow profiles (1-4) in a mold and pressing the ends together with at least one semi-finished product to connect the ends of the hollow profiles to the semi-finished product.

Claims

1. A method for producing a load-bearing structure, comprising: providing a semi-finished composite body having a plurality of plug-in regions each of which has an open end and one open side, the semi-finished composite body being formed from a first fiber/plastic composite material; placing the semi-finished composite body in a mold; placing ends of profiles in the open sides of the plug-in regions of the semi-finished composite body, each of the profiles having a hollow portion formed from a second fiber/plastic composite material and a rigid foam core filling and reinforcing all of the respective hollow portion; and pressing the plug-in regions of the semi-finished composite body together with the ends of the profiles in the plug-in regions of the composite body in the mold to connect a plurality of sides of the ends of the profiles firmly to the semi-finished composite body; and heating the regions of the semi-finished composite body that have been pressed to the ends of the profiles sufficiently to cross link plastic of the first fiber/plastic composite material to plastic of the second fiber/plastic composite material to form the load-bearing structure.

2. The method of claim 1, wherein the semi-finished product comprises at least one moldable and curable sheet-like fiber/plastic composite semi-finished product, the step of pressing comprising connecting the ends of the profiles to the sheet-like fiber/plastic composite semi-finished product in the mold and curing.

3. The method of claim 2, wherein the sheet-like fiber/plastic composite semi-finished product is a sheet molding compound.

4. The method of claim 1, wherein the second fiber/plastic composite material comprises carbon fibers.

5. The method of claim 1, wherein the semi-finished product is formed from a similar material to or the same material as the profiles.

6. The method of claim 1, further comprising mounting end pieces onto ends of the profiles remote from the semi-finished composite body.

7. The method of claim 1, wherein the end pieces are formed from metal.

8. The method of claim 7, wherein the end pieces are formed from magnesium or aluminum.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a load-bearing structure according to the invention having hollow profiles connected firmly with mutually facing ends in a joint.

(2) FIG. 2 is a perspective view of an embodiment of the joint of FIG. 1.

(3) FIG. 3 is a perspective view of a variant of the joint from FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) Four hollow profiles 1 to 4 are illustrated in perspective in FIG. 1. To produce a load-bearing structure 5, the hollow profiles 1 to 4 are connected firmly together at their mutually facing ends in a joint 10. The hollow profiles 1 to 4 have end pieces 11 to 14 at their ends remote from the joint 10.

(5) The end pieces 11 to 14 may serve to produce metal joints for attaching the load-bearing structure 5 to further (not illustrated) load-bearing structure elements. The metal joints are formed for example from aluminum or magnesium. In contrast thereto, the joint 10 is formed from a fiber-reinforced plastics material.

(6) The hollow profiles 1 to 4 are formed from a carbon-fiber-reinforced plastics material. To increase stability, the hollow profiles 1 to 4 have a foam core in their interior. The foam core is preferably a rigid foam core made of a plastic material.

(7) The hollow profiles 1 to 4 having the foam core are manufactured for example by pultrusion, prepreg compression molding or RTM. Pultrusion is the name given to a method in which fiber-reinforced plastic profiles can be produced quickly and easily.

(8) Prepreg is the name given to a semifinished product having a plastic matrix in which fibers, in particular continuous fibers, are embedded. The plastic matrix is preferably a resin that is not yet cured.

(9) The letters RTM stand for resin transfer molding and denotes a method also referred to as transfer molding. Compared with compression molding, a molding material is injected into a mold during transfer molding and cures under heat and pressure.

(10) The hollow profiles 1 to 4 are supported from the inside by the foam core. As a result, the strength and rigidity of the hollow profiles 1 to 4 can be increased considerably. In addition, the fiber content of the hollow profiles 1 to 4 can be reduced because the foam core contributes to the stability.

(11) A sheet molding compound SMC may be used to produce the joint 10. The sheet molding compound SMC advantageously contains carbon fibers. The carbon-fiber-containing SMC also is referred to as a C-SMC. The hollow profiles 1 to 4 can be connected firmly together by way of the SMC.

(12) The connection between an SMC semifinished product and the hollow profiles 1 to 4 can be carried out by adhesive bonding. Particularly advantageously, however, the connection between the hollow profiles 1 to 4 and the SMC semifinished product is achieved by direct pressing of the SMC semifinished product together with the hollow profiles 1 to 4 placed in the mold.

(13) The same material preferably is used to produce the hollow profiles 1 to 4 and the SMC semifinished product during the manufacture of the joint 10. As a result, undesired stresses in the finished load-bearing structure 5 can be prevented. Furthermore, on account of the press fit, the application of the adhesive can be dispensed with.

(14) A composite body 20 that can produce the joint 10 is illustrated in perspective in FIG. 2. The composite body 20 has a total of four openings 21 to 24 that can accommodate the mutually facing ends of the hollow profiles 1 to 4 in FIG. 1.

(15) The openings 21 to 24 are open on their underside. This makes it easier to place the hollow profiles 1 to 4 in the mold with the composite body 20. During placing in the mold (not illustrated), the composite body preferably is arranged with its underside up.

(16) A composite body 30 that also can be used to produce the joint 10 in FIG. 1 is illustrated in perspective in FIG. 3. The composite body 30 comprises a total of four openings 31 to 34 to accommodate the mutually facing ends of the hollow profiles 1 to 4. In contrast to the composite body 20 illustrated in FIG. 2, the openings 31 to 34 in the composite body 30 illustrated in FIG. 3 entirely surround the mutually facing ends of the hollow profiles 1 to 4.

(17) During the manufacture of the load-bearing structure 5, the hollow profiles 1 to 4 easily are plugged with their mutually facing ends into the openings 31 to 34 in the composite body 30. The hollow profiles 1 to 4 in the plugged-in state then are pressed together with the composite body 30 and preferably heated to produce, or cure or crosslink, the joint 10 in FIG. 1.