DE102004028075B4 - Process for producing a fiber composite semifinished product - Google Patents

Abstract

Method for producing a fiber composite semifinished product (2) for the production of a hollow plastic part comprising the following steps: - producing a plastic part core (1) whose outer contour substantially corresponds to the inner contour of the plastic part to be produced; - arranging an additional core (3) at least in a partial region of the outer contour of the plastic part core (1), wherein the plastic part core (1) and the additional core (3) arranged thereon form a braided core; - Producing a braid by braiding the braided core (1, 3) with fiber material; - Removing the additional core (3) of the plastic core part (1) and - applying the braid to the plastic core part (1) formed in the region of the plastic core part (1) removed additional core of the braid at least one of the plastic core part protruding braid region (7) is characterized in that • as the fiber material, a material is at least partially made of carbon fibers and • the braid before removing the additional core in transition areas between the plastic core part (1) and the additional core (3) on the plastic part core (1) Gluing is fixed.

Description

The present invention relates to a method for producing a fiber composite semifinished product according to the preamble of claim 1.

Such a method sit from the EP 1 342 556 A1 known.

In the design and construction of vehicle components, the component weight is always a limiting condition. Intelligent lightweight construction uses not only steel but also other materials such as aluminum or magnesium. For some time now, the possible applications of fiber-reinforced plastics have been explored, both for body shell skin parts and for structural parts or components of body tread. Due to their low weight and high rigidity, plastic components reinforced with carbon fibers appear very promising. The carbon fibers are injected into the plastic and form a reinforcing or stiffening matrix. The carbon fibers can be present in many ways, for example in the form of a woven fabric, in the form of a multiaxial fabric, in the form of a warp-reinforced, unidirectional semi-finished product, in the form of a knitted fabric, in the form of a knitted fabric etc.

For the production of a fiber-reinforced plastic part, a "preform" must first be produced from the fiber material, which essentially corresponds to the component to be produced and which is then overmoulded in a special injection mold with a resin-hardener mixture, resulting in a plastic component.

Apart from purely flat components, such. B. vehicle roofs, have many components, in particular structural components of vehicles, "fittings" or flange pieces on which the components are connected to other components or to support other components such. As hoses, cables, hinges, etc. are provided. If one wishes to manufacture such complex plastic components, the connecting parts or connecting flanges must also be reproduced from the fiber material before the injection process, in order to achieve a sufficient strength of the connecting parts or connecting flanges. It should be noted that carbon fibers are practically almost non-stretchable. For optimum component strength, however, the carbon fibers of the preform should also not be too long or tangled, but should be as stretched as possible in the preform.

The object of the invention is to provide a method for producing a fiber composite semi-finished product, which is suitable for the later production of a hollow plastic part with a connection piece or with a plurality of connecting pieces or connecting flanges.

This object is solved by the features of claim 1. Advantageous embodiments and further developments of the invention can be found in the dependent claims.

For the production of a hollow plastic part, which has on its outside one or more connecting pieces or one or more connecting flanges, first a fiber composite semi-finished product must be produced, which has a plastic part substantially corresponding shape, d. H. in particular already has the or the connecting pieces or connecting flanges.

For the production of such a fiber composite semi-finished product, a first "core part" is first required, which is referred to below as "plastic core part". The outer contour of the plastic part core corresponds substantially to the inner contour of the plastic part to be produced. According to the invention, in addition to the plastic part core, a second core is used, which is referred to below as "additional core". The additional core is arranged on the outer contour of the plastic part core. The plastic part core and the additional core together form a core element, which is referred to below as "braided core".

The actual production of the fiber composite semi-finished product is done by "braiding" the braided core with fiber material. The term "braiding" is very willing to understand and not limited to a specific "textile structure". The term braiding comprises, in particular, braiding in the narrower sense, but also the production of a woven fabric, a knitted fabric, a knitted fabric and other textile structures. Representing all conceivable textile structures, the terms "braiding", "braiding" or "braiding" are used in the following description and in the patent claims.

After braiding the braid core formed by the plastic sub-core and the additional core, the additional core of the plastic sub-core, d. H. removed from the "braid". Subsequently, the braid is applied to the plastic part core. This can be done for example by smoothing by hand. In the area in which the additional core was arranged during the braiding process, there is an excess of braid after removal of the additional core. The excess braid is z. B. brought by smoothing by hand or by means of a tool in the form of the connecting part or the connecting flange.

While the plastic part core substantially corresponds to the inner contour of the plastic part to be produced, the additional core does not need to have a fixed predetermined shape. It is essential, however, that the additional core is designed such that the braiding has a sufficient fiber length for the production of the desired flange (s). With the additional core so a "braid reserve" is reached, which is just so great that from it or the desired flange can be formed. The geometry of the additional core is designed so that the unwinding lengths of the braid correspond exactly to the later fiber lengths of the fiber composite semi-finished product.

According to a development of the invention, the braid is fixed to the plastic core part before removal of the additional core in transition areas between the plastic core part and the additional core. This can be z. B. by gluing with a double-sided adhesive tape or with an adhesive fleece done. The adhesive tape or the adhesive fleece can already be glued onto the plastic part core before the beginning of the braiding process. The adhesive tape or adhesive has the purpose that the braid after removal of the additional core does not slip on the plastic core part, but remains properly positioned.

The plastic core can be made of different materials. Suitable materials are in particular wax or foundry sand. But also many other materials are suitable. By way of example, the additional core can be an air-tight, inflatable body made of a film material. During the braiding process, the auxiliary body is inflated. To remove the additional core, the gas contained in the additional core or the air contained therein is drained. Alternatively, the additional core can also be made of a plastic foam. Suitable for this is in particular expanded polystyrene, which is also known under the brand name "Styrofoam".

In the following the invention will be explained in connection with the drawing. Show it

1 - 4 various steps in the production of a fiber composite semi-finished product; and

5 An embodiment of a fiber composite semifinished product with a substantially circular cylindrical cross-section and a plate-shaped flange.

The 1 - 4 show a schematic representation of individual steps in the production of a fiber composite semi-finished product 1 , First, a plastic core part 1 manufactured, whose outer contour substantially the inner contour of a fiber composite semi-finished product to be produced 2 equivalent. The plastic part core can be made for example of wax or molding sand. Furthermore, an additional core 3 made, the outside of the plastic part core 1 is arranged. The additional core 3 For example, it may be an inflatable foil core. Alternatively, it may also be a plastic foam core, in particular a core of expanded polystyrene. In the case of the very simple embodiment shown here, both the plastic dividing core 1 as well as the additional core 3 cuboid. The plastic part core 1 and the additional core 3 Together they form a "wickerwork core".

When the braid core is ready, with a fiber material, for. B. braided with carbon fibers of the braided core, thereby obtaining the fiber composite semi-finished product 2 receives. The braid can be a woven fabric, a knitted fabric, a knitted fabric or another textile structure.

After the braiding process, the additional core is removed. To prevent after the removal of the additional core, the fiber composite semi-finished 2 on the plastic part core 1 slipped, before braiding on the plastic part core 1 in the transition region between the plastic part core 1 and the additional core 3 a double-sided adhesive fleece 4 . 5 applied, which ensures that the fiber composite semi-finished 2 on the plastic part core 1 sticks.

After removal or extraction of the additional core 3 will, as in 3 represented, the fiber composite semi-finished product 2 by means of a tool 6 or by hand to the plastic dividing core 1 applied or smoothed. In the embodiment shown here, the fiber composite semi-finished product 2 painted so smoothly and folded that in the lower part of the fiber composite semi-finished product 2 a plate-shaped "braid flange 7 "Forms.

This in 4 shown fiber composite semi-finished products 2 represents a "preform", which can now be introduced into an injection mold and can be overmolded with plastic, in particular with a resin-hardener mixture, resulting in a fiber-reinforced plastic part. After encapsulation of the fiber composite semifinished product 2 becomes the plastic part core 1 removed, so that there is a hollow fiber-reinforced plastic part. The plastic part corresponds in shape substantially to the in 4 shown fiber composite semifinished product, that is, it has a substantially rectangular tube portion and a substantially plate-shaped flange portion. As the plate-shaped flange area 7 is integrally connected to the rectangular portion of the fiber composite semi-finished product, and not, as in the prior art, subsequently formed, results in a comparatively high strength of the flange 7 ,

That in the 1 - 4 Embodiment shown is merely an extremely schematically illustrated embodiment, which explains the basic principle of the invention. Of course, much more complex components with a plurality of flanges or fittings can be made in this way.

5 shows a fiber composite semi-finished product 2 , which takes the form of a circular tube cylinder with a plate-shaped flange 7 and also after the in the 1 - 4 described method was made by braiding a braid core formed by a plastic core and an additional core. After braiding the braid core, the additional core was removed and the fiber composite semi-finished product 2 in the in 5 Form shown reshaped.

Claims (9)

Process for producing a fiber composite semifinished product ( 2 ) for the production of a hollow plastic part, comprising the following steps: - producing a plastic part core ( 1 ), whose outer contour corresponds substantially to the inner contour of the plastic part to be produced; - arranging an additional core ( 3 ) at least in a partial region of the outer contour of the plastic part core ( 1 ), wherein the plastic part core ( 1 ) and the additional core ( 3 ) form a braided core; Producing a braiding by braiding the braid core ( 1 . 3 ) with fiber material; - Removal of the additional core ( 3 ) of the plastic part core ( 1 ) and - applying the braid to the plastic dividing core ( 1 ) in the region of the plastic part core ( 1 ) removed additional core from the braid at least one of the plastic core part protruding braid area ( 7 ) is formed, characterized in that • as a fiber material, a material is used, which consists at least partially of carbon fibers and • the braid before removing the additional core in transition areas between the plastic core part ( 1 ) and the additional core ( 3 ) on the plastic part core ( 1 ) is fixed by gluing. Method according to claim 1, wherein in the area of the plastic part core ( 1 ) removed additional core ( 3 ) from the braid at least one of the plastic part core ( 1 ) projecting flange-like braid area ( 7 ), which reinforces a flange of the plastic part in the plastic part to be produced. Method according to one of claims 1 or 2, wherein the braid after removal of the additional core ( 3 ) on the plastic part core ( 1 ) and in the area of the removed additional core ( 3 ) to one of the plastic part core ( 1 ) protruding flange braid area is folded, which reinforces a flange of the plastic part in the produced plastic part. The method of claim 1 to 3, wherein the fixing is carried out by a double-sided adhesive film or by a double-sided adhesive nonwoven, the or before the braiding on the plastic core part ( 1 ) is applied. Method according to one of claims 1 to 4, wherein the plastic part core ( 1 ) is made of a waxy material. Method according to one of claims 1 to 5, wherein the plastic part core ( 1 ) is made of molding sand. The method of any one of claims 1 to 6, wherein the supplemental core is an inflatable body made of a sheet material, wherein the body is inflated during braiding and fluid is released from the body prior to removal of the supplemental core. Method according to one of claims 1 to 7, wherein the additional core is made of a plastic foam. A method according to any one of claims 1 to 6 or 8, wherein the additional core consists of expanded polystyrene.

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