DE102011108157A1 - Molding tool for production of fiber-reinforced plastic components, has electrically insulating molding surfaces, which are designed for limiting molding cavity, where one or both tool sections are made from electrically insulating material - Google Patents

Abstract

The molding tool has two tool sections (1,1') with molding surfaces, where multiple induction devices (2) are formed on one of the tool sections. The molding surface of the tool section is designed to be electrically insulating. The electrically insulating molding surfaces are designed for limiting a molding cavity. One or both the tool sections are made from an electrically insulating material, particular from wood or plastic. Multiple cooling units (3) are provided for the induction devices for cooling the molding surfaces of the tool sections. An independent claim is also included for a method for fabricating fiber reinforced plastic components made of fiber reinforced plastic.

Description

The invention relates to a mold and a method for producing fiber composite plastic components.

From the prior art methods for the production of fiber composite parts are known, in particular, the curing of the plastic is very tedious, so that due to the long cycle times a mass production of FRP components is priced uninteresting. Furthermore, the tool surfaces of the metallic electrically conductive molding tools for FRP components are heated by means of induction coils. This is on the one hand complex in terms of apparatus and, on the other hand, the energy input into the component to be cured in relation is not particularly great.

That's how it describes WO 2005/094127 A1 a mold that is used to heat materials in the industrial production of large-scale objects and allows a variety of forming processes. For this purpose, the tool uses electromagnetic induction. The electromagnetic fields generated by means of inductors are applied to an intermediate element having an inside and an outside, which is arranged between the inductors and the material to be heated.

In the WO 2006/136743 A1 an inductive heating device is disclosed in which at least a portion of the device body, which is intended for heating, consists of a magnetic and heat-conducting material in which there are a plurality of cavities near the surface surrounding a field winding. The heat generated by induction in the walls of the cavities is conducted to the surface of the section to be heated.

The WO 02/38355 A1 discloses a molding tool for plastic and composite materials that allows the materials to be reduced in energy, even at high temperatures, without damaging the mold. The molding tool comprises a molding having a recess and heating means which directly heat the material to be formed without utilizing the thermal conductivity of the molding and / or the recess for heating the material to be formed. The heating means are electrokinetically or magnetodynamically and send an electric current directly or by induction into the material, if this is electrically conductive. The circulation of the stream causes the heating of the material, but does not act on the molded body, since the mold cavities thermally insulate the moldings from the base plate or die, which are heated only slightly or not at all. Therefore, these base members may be made of a common composite material such as epoxy resin.

The WO 2007/031660 A1 describes an induction heating forming apparatus having electrically conductive mold halves. These are shielded, except for a mold cavity, so that an externally applied magnetic field induces currents in the non-shielding coated surfaces of the mold cavity and thus heats them.

Based on this prior art, it is an object of the present invention to provide a simple mold with an improved heating device for heating a matrix-forming plastic system of a fiber composite material, with which the cycle times can be reduced, so that the fiber composite molding produced therein can be mass produced in large numbers.

This object is achieved by a mold with the features of claim 1. Further developments are set forth in the subclaims.

Furthermore, by a method having the features of claim 7, the accelerated production of preforms or molded components from a fiber composite plastic using a cost-effective mold according to the invention is disclosed.

Further developments of the objects are carried out in the respective subclaims.

The mold according to the invention for the production of fiber composite plastic components has at least one tool component with a mold surface and has a plurality of induction devices. In this case, advantageously, at least the mold surface of the tool component is electrically insulating, so that a targeted inductive heating of the fibers can be achieved and only a short warm-up time is required.

Furthermore, in one embodiment it can also be provided that both tool components of the molding tool have electrically insulating mold surfaces and thus delimit a mold cavity which enhances and optimizes the aforementioned effect of direct fiber heating. Suitably, the induction devices are present in at least one of the two tool components. The mold surfaces may be part of one or more tool inserts, which are inserted exchangeably in the tool components and releasably secured. The tool inserts may be formed as thin-walled deposits, on the one hand contain the mold surfaces and on the other hand preferably a flat support surface for have support in the insert tray of the tool component. Here, if necessary, only a small part of the overall tool can be changed in a simple manner. Thus, the tool for the formation of differently contoured preforms or fiber composite plastic components is very variable and versatile.

Instead of forming only the mold surfaces electrically insulating, it can also be provided that one or both tool component (s) consist of an electrically insulating material such as wood or a plastic.

It is also suitable if the molding tool has a plurality of cooling devices for the induction devices in the at least one tool component or that it is equipped alternatively or additionally with cooling devices for cooling the tool component molding surface. The cooling devices can preferably be cooling pipes running parallel to the induction devices, in particular cooling pipes made of copper, or they can be formed by the induction devices designed as pipes, in particular as copper pipes.

Furthermore, the mold has injection means for a matrix-forming plastic system.

With the molding tool according to the invention, the following method for manufacturing components made of a fiber composite plastic can be carried out:
It comprises the steps of providing a fiber material which consists at least partially of electrically conductive fibers. This may preferably be carbon fibers. Then follows the placement of the fiber material with a plastic material on the at least one insulating formed surface of the tool component; when there are two such insulating mold surfaces, the fiber comes to lie therebetween. Now, inducing currents in the electrically conductive fibers by means of the induction devices of the mold. This causes heating of the plastic material surrounding the fibers. After switching off the induction device, it comes to cooling of the plastic system. Depending on the process, this results in a molded component made of fiber composite plastic or a preform.

The method can provide for the continuous cooling of the induction devices with water or the acyclic cooling with air, in particular by flowing through cooling channels which run parallel to the induction devices or are provided by the tubular induction devices themselves. Alternatively or additionally, the fiber composite plastic component can also be cooled during curing, which can be done with the device according to the invention advantageously temporally and / or locally controlled.

Advantageously, the fiber material can be provided as a preform, and the plastic material can be a matrix-forming plastic system during the production of the molded component, which is supplied to the fiber material inserted in the mold before heating and / or is melted or activated during heating and on cooling to form the plastic matrix hardens.

Furthermore, the fiber material for producing the preform may contain fiber layers which consist at least partially of the electrically conductive fibers, in particular carbon fibers. The plastic material may comprise a binder material, in particular a powdered binder material, which is applied to the fiber layers prior to inductive heating in the mold and is melted by the inductive heating, wherein the fiber layers connected and the pliable preform is obtained.

Instead of the cycle times of up to 45 minutes required to date for the processing of fiber-reinforced plastics, the direct heating of the carbon fiber by induction can achieve a very high curing rate with significantly increased process reliability. Thus, the production process for large numbers of copies are suitable. Also preforms and semi-finished products with integrated binder can be obtained in the tool according to the invention in extremely short cycles. The direct heating of the fiber material can be achieved energetically effective rapid curing or curing rates. To reduce costs, reduced tooling costs, both of a component tool and a preform tool, and reduced cycle times contribute.

These and other advantages will be set forth by the following description with reference to the accompanying figure.

The reference to the figure in the description is to aid in the description and understanding of the subject matter. The figure is merely a schematic representation of an embodiment of the invention.

The single FIGURE shows a schematic side sectional view through a mold with inserted fiber material.

The molding tool according to the invention is suitable for the production of preforms or fiber composite plastic molded components and has at least one lower tool component 1 with a mold surface. Preferably, however, the molding tool will be a two-part tool as shown in the figure, whose mold components define a mold cavity in which a fiber material 5 is arranged to form the preform or the mold component.

In the figure, both tool components 1 . 1' the induction devices 2 on, for inductive heating in the fiber material 5 contained electrically conductive fibers, for example carbon fibers or metal fibers used.

In general, it is also possible that only one of the tool components 1 . 1' with the induction devices 2 Is provided. The fiber material 5 , which can be used in the mold, consists or at least sufficiently fibers of an electrically conductive material such as carbon or metal. To form a preform fiber layers, such as fabrics, scrims, mats, nonwovens, knitted fabrics, etc. can be used. In addition to the electrically conductive fibers, the fiber layers may contain reinforcing fibers of other materials, for example gas. For the production of the molded component may be used as a fiber material, a preform or other semi-finished fiber; However, the use of non-pre-impregnated or consolidated fiber materials corresponding to those for forming the preform is also conceivable.

In the electrically insulated mold cavity, in order to produce the fiber composite component, the electrically conductive fibers are formed therein by means of the induction devices 2 inductively heated. The heat generated in this way is used for melting or activating a matrix plastic or binder material likewise introduced into the mold cavity.

Due to the electrical conductivity of the fibers such as the carbon fibers is in these fibers by means of arranged in the tool induction coils 2 induces a current, these fibers heating up due to their electrical resistance. Since the mold cavity is electrically isolated, the field energy can be particularly concentrated on the fibers, so that the warm-up time is very short and the required energy to be applied is very small compared to known devices.

It is particularly advantageous if the entire tool so both tool components 1 . 1' or the above-mentioned tool inserts are made of a non-conductive material, such as wood, plastic and the like, since then concentrates the energy input alone on the fibers. If the mold surfaces or the entire tool are not only electrically insulating but also thermally insulating, which is the case in the case of wood and plastic, and the heat dissipation, which always exists in tool components made of metallic and / or heat conductive materials, is suppressed.

The induction coils 2 are caused by parallel cooling lines 3 For example, cooled from copper. Also conceivable are induction tubes made of copper, so that no separate lines are required, whereby space and effort is saved.

For cooling with water a continuous flow is required due to the otherwise occurring jump in the state of aggregate state.

Alternatively, an air cooling is conceivable, wherein the flow should be especially in the use of preforms acyclic.

Furthermore, cooling channels can 3 be provided, by means of which the process control can be selectively influenced, if desired. Thus, faster or less rapidly curing zones can be achieved in the resulting component to possibly still allow a subsequent forming step. In addition, the cured component or preform can be cooled very quickly and then removed from the tool.

The method is applicable except for the production of a mold component in the production of preforms, wherein the individual fiber layers are sprinkled with binder powder, draped in the mold and then heated inductively. The binder contained melts and consolidates or consolidates the fiber layers, resulting in a pliable or at least partially consolidated preform, depending on the binder type and quantity.

If the mold is used in the production of FRP components in the RTM process, an inductive heating to cure the matrix plastic is followed by an injection step with a matrix-forming plastic, which may, for example, be a resin system. For this purpose, the molding tool can be equipped with a corresponding injection device opening into the mold cavity.

In general, the plastic material used may be a thermoplastic matrix or thermosetting or elastomeric plastics. The same applies to a binder material in the production of preforms. In the case of thermoplastics, inductive heating causes melting, so that the fibers are impregnated by the thermoplastic polymer melt be, whereupon the curing is carried out by cooling. For thermosetting or elastomeric resin systems impregnating the fibrous material, the heating causes activation of the crosslinking reaction leading to the formation of the matrix.

If a thermoplastic is used as the matrix, a later transformation of the cured fiber composite components is also possible.

Thus, according to the invention, a cost-effective tool is provided by the implementation of induction devices and cooling devices in a plastic or wood mold, which allows the cost-effective production of FRP components or their preforms in short cycles and thus suitable for mass production.

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 patent literature

• WO 2005/094127 A1 [0003]
• WO 2006/136743 A1 [0004]
• WO 02/38355 A1 [0005]
• WO 2007/031660 A1 [0006]

Claims (9)

Mold for producing fiber composite plastic components, wherein the mold at least one tool component ( 1 . 1' ) with a mold surface, and wherein the mold comprises a plurality of induction devices ( 2 ), characterized in that at least the mold surface of the tool component ( 1 . 1' ) is formed electrically insulating. Molding tool according to claim 1, characterized in that the molding tool has two tool components ( 1 . 1' ), whose electrically insulating mold surfaces define a mold cavity, wherein the induction devices ( 2 ) in at least one of the tool components ( 1 . 1' ) are present. Mold tool according to claim 1 or 2, characterized in that the one or both tool component (s) ( 1 . 1' ) consist of an electrically insulating material, in particular of wood or a plastic. Mold according to at least one of claims 1 to 3, characterized in that the mold comprises a plurality of cooling devices ( 3 ) for the induction devices ( 2 ) in the at least one tool component ( 1 . 1' ) and / or a plurality of cooling devices ( 3 ) for cooling the tool component molding surface, the cooling devices ( 3 ) preferably parallel to the induction devices ( 2 ) running cooling lines ( 3 ), in particular cooling lines ( 3 ) are made of copper, or by the designed as pipes, especially as copper pipes induction devices ( 2 ) to be provided. Mold according to at least one of claims 1 to 4, characterized in that that the mold comprises injection means for a matrix-forming plastic system. A method for producing fiber composite plastic components from a fiber composite plastic using a molding tool according to at least one of claims 1 to 5, comprising the steps of - providing a fiber material ( 5 ), which consists at least partially of electrically conductive fibers, which are in particular carbon fibers, - arranging the fiber material ( 5 ) with a plastic material on the at least one electrically insulating formed surface of the at least one tool component ( 1 . 1' ) and - heating the plastic material surrounding the fibers by inducing an electric current in the electrically conductive fibers by means of the induction devices ( 2 ) of the molding tool, - hardening of the plastic material after switching off the induction devices ( 2 ) to form a preform, which is formed in at least one further step to a fiber composite plastic component, or forming the fiber composite plastic component. Method according to claim 6, comprising the steps: - continuous cooling of the induction devices ( 2 ) with water or acyclically with air, in particular by flowing through cooling channels ( 3 ) parallel to the induction devices ( 2 ) or through the tubular induction devices ( 2 ) are self-provided, and / or - when curing cooling, in particular temporally and / or locally controlled cooling of the preform or the fiber composite plastic component. A method according to claim 6 or 7, wherein the fibrous material ( 5 ) is a preform, and / or wherein the plastic material in the production of the fiber composite plastic component is a matrix-forming plastic system which - before being heated to the fiber material inserted in the mold ( 5 ) and / or - is melted or activated during heating and cured on cooling to form a plastic matrix. Method according to claim 8, wherein the fibrous material ( 5 ) for producing the preform fiber layers ( 5 ), which consist at least partially of the electrically conductive fibers, in particular carbon fibers, and wherein the plastic material is a binder material, in particular a powdery binder material, which prior to the inductive heating in the mold on the fiber layers ( 5 ) is applied and is melted by the inductive heating, wherein the fiber layers ( 5 ) are joined together to form the preform.

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