DE102016120864A1 - Production of a fiber-plastic composite component - Google Patents

Abstract

The invention relates to the production of a component comprising a fiber-plastic composite by means of a mold (11) having a cavity (14), the fiber-plastic composite having a plastic matrix and reinforcing fibers, the plastic matrix and the reinforcing fibers being introduced into the cavity (14 ), the plastic matrix in the cavity (14) is made to flow, in a sealing region (19) of the cavity (14) the cross-sectional area of the cavity (14) is reduced such that the flow of the plastic matrix is reduced, and in the Sealing region (19) with the reduced cross-sectional area, the plastic matrix is locally cured, so that the cavity (14) in the sealing region (19) is sealed by the cured portion of the plastic matrix to the outside. In this way, a possibility for a simple and reliable sealing of a mold (11) for the production of a fiber-plastic composite component is provided.

Description

The invention relates to a production method for a component comprising a fiber-plastic composite by means of a mold having a cavity and to an arrangement having a curing device and a mold for producing a component which has a fiber-plastic composite with a plastic matrix and reinforcing fibers.

In the automotive industry, the use of lightweight materials with better weight-specific properties, such as fiber-plastic composites (FRP), is steadily increasing. In this context, hybrid structures consisting of a metallic basic structure and a reinforcement made of fiber-plastic composites offer a high level of lightweight construction potential. In these structures, the design can be carried out according to stress and the most expensive fiber-plastic composites is used only in places of highest stress. In addition to the automotive industry such lightweight structures are increasingly used in other industries, such as aerospace technology, in the production of sports equipment and in the wind energy industry.

A limiting factor for the use of fiber-plastic composites or hybrid components in large-scale automotive production is the high production costs. The large-scale production-capable process for FRP components can be distinguished by the Resin Transfer Molding (RTM) process and prepreg pressing become.

In the RTM process, an overpressure is generated, which presses the resin for the plastic to form the fiber-plastic composite in a heated and thus liquid form into the cavity of a mold. Here, relatively high pressure differences can be achieved, so that the production of large-scale components with complex geometries is possible.

An essential feature of prepreg pressing is the use of pre-impregnated FRP semi-finished products. In a first step, the reinforcing fibers are continuously impregnated in a prepreg plant with the matrix resin and rolled up. Subsequently, the individual prepreg layers are layered and pressed together according to the stresses of the subsequent component to form a multilayer composite. Depending on the joining technique to be used, an adhesive film is applied to the top of the prepreg. In the next step, the prepregs are cut to size. The cutting takes place depending on the component geometry of the FRP components. In hybrid components, the prepreg is assembled according to the reinforcement geometry. Finally, the prepregs on the top are provided with a release film and stored in magazines. Depending on the release agent, prepreg pressing of FRP components and indirect prepreg pressing additionally apply a release film on the underside. In actual prepreg pressing, pure FRP components or hybrid components are produced in a prepreg press tool. As a rule, the tool consists of a mold with a sealed cavity in which the curing of the matrix resin is as complete as possible by heating.

Today's hybrid systems, however, have significant disadvantages, in particular due to the integration of the FRP materials, since the processing is usually carried out in less automated or even completely manual processes. The typical production route of hybrid structures consists of the separate production of the metallic or FKV components and the subsequent connection of the materials in a downstream process by welding, riveting, clinching or gluing. In addition to the procedural disadvantages this necessarily brings additional weight of the adhesive in the component component. A time- and cost-efficient production of hybrids, however, can be achieved if the matrix resin is used as an adhesive and thereby the connection between the metal and FKV components and the actual component manufacturing process-integrated done in one step. This manufacturing process is referred to as intrinsic or direct manufacturing of a hybrid component. This means a one-step direct production and thus a significant reduction of production time and effort to a technologically advanced high volume product without downstream joining processes.

For details about the above procedures, refer to the doctoral thesis "Development and production of hybrid components made of metals and fiber composite plastics for lightweight construction in the automobile" by Dipl.-Ing. Dipl.-Wirt.-Ing. Christian Lauter (Faculty of Mechanical Engineering of the University of Paderborn, 2014) and the publication WANG, Z .; RIEMER, M .; KOCH, SF; BARFUSS, D .; GRÜTZNER, R .; AUGENTHALER, F. SCHWENNEN, J .: Intrinsic Hybrid Composites for Lightweight Structures: Tooling Technologies., Advanced Materials Research, 1140, 247-254, 2016 ,

Common to all the aforementioned methods is the use of multi-part molds in which the temperatures required in the process (about 80 ° C to 250 ° C) and pressures (about 3 bar to 40 bar) can be adjusted. A particularly critical problem in this case is the sealing of the molds. From practice different concepts for the sealing of FKV and hybrid tools are known. These include tool concepts without additional sealing elements, such as Dipping or crushing tools. In addition to the low process stability, the sealing effect is often insufficient with such dipping and pinching edge tools, especially at high process pressures. For this reason, mainly tools with silicone-based sealing elements are used. In this case, flexible seals are introduced into a groove in the tool, for example, to seal an upper mold against a lower mold. Since these seals often can not guarantee a process-stable seal in the above-mentioned process parameters, several sealing elements are generally used in succession. The disadvantage here, however, is a high wear, which leads to increased control and maintenance. In addition, the cleaning of the tool grooves is a critical process that limits the service life of the tools.

Proceeding from this, it is the object of the invention to provide a possibility for a simple and reliable sealing of a mold for producing a component having a fiber-plastic composite.

This object is solved by the subject matters of the independent claims. Preferred developments are described in the subclaims.

According to the invention, therefore, a production method for a component comprising a fiber-plastic composite is provided by means of a mold having a cavity, the fiber-plastic composite having a plastic matrix and reinforcing fibers, the plastic matrix and the reinforcing fibers being introduced into the cavity, the plastic matrix in the cavity is made to flow, in a sealing region of the cavity, the cross-sectional area of the cavity is reduced such that the flow of the plastic matrix is reduced, and in the sealing region with the reduced cross-sectional area, the plastic matrix is locally cured, so that the cavity in the sealing region the hardened portion of the plastic matrix is sealed to the outside.

The solution according to the invention thus utilizes the plastic matrix present in the fiber-plastic composite directly for tool sealing, ie for sealing the cavity of the mold for producing the component with respect to the environment. A major advantage of this solution is the ability to completely dispense with separate sealing elements. This enables on the one hand the reduction of tool life and the manufacturing effort as well as the implementation of very complex three-dimensional component and tool structures. In addition, recesses can be introduced with almost any contours and sizes directly in the production in the FKV component. This leads to the elimination of expensive post-processing steps and reduces the waste of expensive semi-finished products.

The solution according to the invention is fundamentally applicable to all types of fiber-plastic composites and hybrid components made of FRP and metals. This applies in particular to polymeric matrices, namely thermoplastic and thermoset systems and for all types of semifinished products, such as fabrics, scrims, knitted fabrics and knits. The semi-finished products may be pre-impregnated (prepregs) or individually, namely as dry fibers and matrix. The initial state may also be fully consolidated, e.g. by means of organic sheets. In the case of hybrid components, basically all types of metals are usable, such as high-strength steels and aluminum, preferably in sheet form. Incidentally, in principle, all types of fibers can be used, such as fibers of carbon, glass, metal, ceramic and natural fibers. Furthermore, in principle, all fiber lengths are possible, that is endless, long and short, which can be used in all orientations, ie unidirectional, multi-directional, isotropic, directional or as a random fiber. Finally, the invention finds application in basically all processes for the production of FRP components, such as infusion and injection processes (Resin Transfer Molding, VARI, SCRIMP, ...), Drapping processes (prepreg presses, wet pressing, ...), flow processes ( GMT, SMC, LFI, ...) and intrinsic processes for the production of hybrid components.

Essential to the invention is that the plastic matrix is locally cured in the sealing area, so that the cavity is sealed in the sealing area by the cured portion of the plastic matrix itself to the outside, so this no longer a separate seal is required. The local curing of the plastic matrix in the sealing area can take place in different ways.

According to a preferred embodiment of the invention, the plastic matrix is cured in the direct thermal induced induced in the sealing area. Preferably this is done by means of a radiation source, e.g. a laser or a UV lamp, or by means of electrical induction. In connection with the electrical induction is particularly preferably provided that metallic additives are introduced into the plastic matrix.

Alternatively, according to a preferred development of the invention, provision is made for the plastic matrix to be cured indirectly thermally induced in the sealing region, preferably by means of a heated or cooled tool. Such a heated tool can eg from a built-in a part of the form of heating consist. With very particular preference, a temperature which clearly exceeds the temperature of the remaining region of the mold is produced by means of such a heated tool. At a temperature of the form of 80 ° C for the actual production of the fiber-plastic composite component having thermosetting Exposidharzsystemen a heated temperature of 300 ° C for local curing of the plastic matrix is preferably produced by means of the heated tool.

Finally, according to another preferred embodiment of the invention, it is also possible to cure the plastic matrix in the sealing area by means of a chemical catalyst which locally increases the reaction rate for curing. In this way, it is possible to dispense with an additional device on the mold for producing the component having the fiber-plastic composite, such as a heater or a radiation source.

According to a preferred development of the invention, it is further provided that in the sealing region the hardened portion of the plastic matrix acts as a seal between two parts of the mold, e.g. between an upper mold and a lower mold. This is particularly preferred if it is an at least two-part mold and a pure FKV component is produced which does not represent a hybrid component and thus has no metal components. Alternatively, it is provided according to a preferred embodiment of the invention that the component which is produced by means of the mold is a hybrid component of the fiber-plastic composite and a metal part and in the sealing region of the cured portion of the plastic matrix as a seal between a part of Form and the metal part acts.

Finally, according to a preferred development of the invention, the reduced cross-sectional area in the sealing region is formed by a gap whose dimension in one dimension is less than 1 mm, preferably less than 0.35 mm, very preferably 0.1 mm or less. In this way, an effective reduction of the flow of the plastic matrix is achieved and at the same time allows a rapid curing of the plastic matrix to seal the cavity of the mold to the outside.

In addition, the invention is in an arrangement with a curing device and a mold for producing a component, which has a fiber-plastic composite with a plastic matrix and reinforcing fibers, wherein the mold has a cavity into which the plastic matrix and the reinforcing fibers are introduced and in the plastic matrix in the cavity can be made to flow, in a sealing region of the cavity the cross-sectional area of the cavity is reduced in order to reduce the flow of the plastic matrix, and in the sealing region with the reduced cross-sectional area the plastic matrix is locally curable by means of the curing device, then in that the cavity in the sealing area is sealed to the outside by the hardened portion of the plastic matrix.

Preferred developments of this arrangement according to the invention result in analogy to the preferred developments of the manufacturing method according to the invention, as described above.

The invention will be further explained with reference to preferred embodiments with reference to the drawings.

• 1 a - d schematisch eine aus dem Stand der Technik bekannte intrinsische RTM-Herstellung eines Hybridbauteil, und
• 2 schematisch die Herstellung eines einen Faser-Kunststoff-Verbund aufweisenden Bauteils gemäß einem bevorzugten Ausführungsbeispiel der Erfindung.

In the drawings show:

• 1 a - d schematically show an intrinsic RTM production of a hybrid component known from the prior art, and
• 2 schematically the production of a fiber-plastic composite component according to a preferred embodiment of the invention.

From the 1 a - d schematically shows a known from practice intrinsic RTM production of a hybrid component 5 made of a metal and a fiber-plastic composite. The preparation takes place by means of a mold 1, which has an upper mold 2 and a lower mold 3, which are assembled in a sealed manner, while a cavity Form 4, by means of which the hybrid component 5 is formed. For sealing between the upper mold 2 and the lower mold 3 silicone-based sealing elements 6 are provided.

In a first step, as in 1a shown, in accordance with the shape of the manufactured hybrid component 5 already suitably formed sheet 7 inserted into the lower mold 3, in which in turn a textile semi-finished product 8 is inserted. In a second, out 1 b apparent step, the lower mold 3 is then closed by means of the upper mold 2, and there is a hybridization by resin injection 9 for the plastic with subsequent curing and bonding. After the in 1c shown demolding is the hybrid component 5 with FKV and metal shares available, as in 1d shown.

This process is carried out at a mold temperature, ie a temperature of the mold 1, of 80 ° C and an injection pressure of 5 bar. In order to allow a leakage of the resin from the mold 1 avoid, the already mentioned silicone-based sealing elements 6 are provided between the upper mold 2 and the lower mold 3. A disadvantage with respect to these sealing elements 6 is an immense wear, which is caused by high chemical and mechanical loads and leads to a large control and maintenance. The resulting changes in the properties of the sealing materials have a negative effect on the reproducibility and on the process reliability during component production as well as on the component quality. Therefore, a new set of sealing elements 6 is often required after only a few components. The change of the sealing elements 6 and the cleaning of the mold in the contact area of the sealing elements thus limit the service life of the tool considerably. In addition, the sealing effect is limited, so that at high pressures sometimes several sealing elements 6 must be inserted one behind the other. This increases process and tool costs. Incidentally, this also limits the usable pressures.

The problem described above is remedied in accordance with a preferred embodiment of the invention, which relates to a thermosetting Exposidharzsystem, characterized in that, as schematically from 2 it can be seen that the exit of the resin 10 from the mold 11 according to the preferred embodiment of the invention is avoided in another way, namely by the plastic matrix-forming resin 11 itself. This will be explained in detail below.

The shape 11 according to the preferred embodiment of the invention is in 2 shown schematically in a border area. The present process according to the preferred embodiment of the invention also takes place at a temperature of 80 ° C of the mold 11 and an injection pressure of 5 bar. The flow direction F of the plastic matrix-forming resin 10 extends as shown by the long arrow in the lower region of 2 shown, from left to right.

Shown is the upper mold 12 together with the formed in the mold 11 cavity 14, in which the plastic matrix forming resin 10 has already been introduced. The part shown here cavity 14 is bounded at the top by the upper mold 12 and at the bottom by a metal sheet 15 of the hybrid component to be produced. In the region of a heating element 16, the cross section of the reduced cavity 14 strong, so that there is only a gap 18 with a height of 0.1 mm here. Compared to the rest of the upper mold 12, the heating element 16 is thermally shielded by means of a Wäremisolierung 17. In this way, the temperature of the remainder of the mold 11 can be maintained at 80 ° C despite the locally acting heating element 16.

The lower end of the heating element 16, in the present case an electric heating cartridge, is therefore only 0.1 mm away from the plate 15 located thereunder. For this reason, the flow of the plastic matrix-forming resin 10 is greatly inhibited in this area. In addition, the heating element 16 heats this area to about 300 ° C. As a result, local curing of the resin 10 forming the plastic matrix occurs in a targeted manner, as a result of which self-sealing by the plastic matrix itself is practically achieved in this sealing region 19. A separate poetry 13 for sealing the gap 18 and thus the cavity 14 to the outside is thus only required as a gas seal, but not to avoid leakage of the resin. Downtime for changing the sealing materials can be avoided by this novel sealing concept.

LIST OF REFERENCE NUMBERS

shape

1

upper mold

2

under the form

3

cavity

4

hybrid component

5

sealing elements

6

sheet

7

semi-finished textile

8th

resin injection

9

resin

10

shape

11

upper mold

12

separate seal

13

cavity

14

sheet

15

heating element

16

thermal insulation

17

gap

18

sealing area

19

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• "Development and production of hybrid components made of metals and fiber composite plastics for lightweight construction in the automobile" by Dipl.-Ing. Dipl.-Wirt.-Ing. Christian Lauter (Faculty of Mechanical Engineering of the University of Paderborn, 2014) and the publication WANG, Z .; RIEMER, M .; KOCH, SF; BARFUSS, D .; GRÜTZNER, R .; AUGENTHALER, F. SCHWENNEN, J .: Intrinsic Hybrid Composites for Lightweight Structures: Tooling Technologies., Advanced Materials Research, 1140, 247-254, 2016 [0007]

Claims (10)

Manufacturing method for a component having a fiber-plastic composite by means of a cavity (14) having mold (11), wherein the fiber-plastic composite has a plastic matrix and reinforcing fibers, the plastic matrix and the reinforcing fibers are introduced into the cavity (14), the plastic matrix in the cavity (14) is made to flow, in a sealing region (19) of the cavity (14), the cross-sectional area of the cavity (14) is reduced such that the flow of the plastic matrix is reduced, and in the sealing region (19) with the reduced cross-sectional area, the plastic matrix is locally cured, so that the cavity (14) in the sealing region (19) is sealed to the outside by the hardened portion of the plastic matrix. Production method according to Claim 1 , wherein the plastic matrix in the sealing region (19) is cured directly thermally induced, preferably by means of a radiation source (laser or UV lamp) or by means of electrical induction. Production method according to Claim 1 , wherein the plastic matrix in the sealing region (19) is cured indirectly thermally induced, preferably by means of a heated or cooled tool area. Production method according to Claim 1 in which the plastic matrix in the sealing region (19) is cured by means of a chemical catalyst which locally increases the reaction rate for curing. Manufacturing method according to one of the preceding claims, wherein in the sealing region (19) the hardened portion of the plastic matrix acts as a seal between two parts of the mold (11). Manufacturing method according to one of Claims 1 to 4 wherein the component is a hybrid component of the fiber-plastic composite and a metal sheet (15) and in the sealing region (19) the cured portion of the plastic matrix acts as a seal between a part of the mold (11) and the metal part. Arrangement with a curing device and a mold (11) for producing a component comprising a fiber-plastic composite with a plastic matrix and reinforcing fibers, wherein the mold (11) has a cavity (14) into which the plastic matrix and the reinforcing fibers can be introduced and in which the plastic matrix can be made to flow, in a sealing region (19) of the cavity (14), the cross-sectional area of the cavity (14) is reduced to reduce the flow of the plastic matrix, and in the sealing area (19) with the reduced cross-sectional area, the plastic matrix is locally curable by means of the curing device, so that the cavity (14) in the sealing area (19) is sealed to the outside by the hardened portion of the plastic matrix. Arrangement according to Claim 7 wherein in the sealing region (19) the reduced cross-sectional area is formed by a gap (18) whose dimension in one dimension is less than 1 mm, preferably less than 0.35 mm, most preferably 0.1 mm or less. Arrangement according to Claim 7 or 8th wherein the curing device comprises a heating element (16) or a cooling element. Arrangement according to Claim 7 or 8th wherein the curing device comprises a radiation source, preferably a laser or a UV lamp.

Images