DE102015115782B4 - Mold and method for the manufacture of a molded component - Google Patents

Abstract

Mold (10) for the production of a molded part by supplying heat with a forming tool surface (12) which at least partially corresponds to the geometry of the molded component to be produced and which is designed for depositing a material for producing the molded component, and at least one heating module (20 ), which has at least one electrical resistance heating element (21) which cooperates thermally with the forming tool surface (12) for tempering the deposited molded component, wherein the electrical resistance heating element (21) formed from a fiber material of a fiber composite material and having at least two mutually insulated electrical connections ( 23a, 23b) for electrically contacting the electrical resistance heating element (21) is connected to an electrical voltage source (14), characterized in that the electrical connections (23a, 23b) are formed from an electrically conductive hard foam.

Description

The invention relates to a mold for the production of a molded component, which is produced by supplying heat. The invention also relates to a method for producing such a molded component, in particular a fiber composite component for this purpose.

Due to the high weight-specific strength and rigidity, fiber composites are nowadays indispensable in the aerospace and automotive industries. The fiber material of a fiber composite material entrains the fiber composite component an enormous strength and rigidity in the fiber direction while minimizing weight. As a result, structural components made of fiber composite materials are being manufactured in the meantime in order to save as much weight as possible without incurring structural deficits.

In the production of a fiber composite component, a fiber material is usually penetrated (impregnated, impregnated, infused) with a matrix material and then cured by supplying heat, so that the matrix material together with the fiber material forms an integral unit. By curing the matrix material, the fibers of the fiber material are fixed in their arrangement and thus define the load-bearing path of the component.

In most applications, in the production of fiber composite components for this purpose, a mold is used, which has a forming tool surface on which the fiber material (dry or pre-impregnated) is stored. As a rule, the shaping tool surface has a geometry that at least partially corresponds to the later component geometry. Subsequently, the matrix material passing through the fibers is cured by supplying heat to the mold. One of the most common methods in this case is the retraction of the mold, on the forming tool surface, the fiber material (dry or preimpregnated) is arranged in an autoclave so as to cure by pressurization and temperature control of the matrix material that permeates the fiber material. For this purpose, temperatures of more than 180 degrees are usually used.

However, a disadvantage of this method is the enormous expenditure of energy, which increases disproportionately, in particular, with the size of the component. Because the larger the component to be produced, the larger the mold, so that the total thermal mass to be heated increases significantly and thus more thermal energy is needed to bring the component to the curing temperature. In addition, the equipment costs are very high for larger components, so that the purchase and use of such an autoclave reflected in high component costs.

There are therefore efforts to allow the energy input into the mold component for the purpose of curing the matrix material other than by means of an autoclave. From the DE 10 2012 102 563 A1 For example, a device is known in which the fiber composite material is to be heated by means of a microwave oven. The advantage here is that only the matrix material is heated, while the other components, in particular the mold, just are not heated. As a result, the thermal mass is reduced to the essential. The disadvantage, however, is that such systems, especially for large components are extremely complex and expensive, which greatly limits the use.

It is further known to provide heated molds, in which a temperature of the component takes place via the mold. Thus, it is known, for example, to provide fluid channels within a solid mold in which a tempered fluid is passed, so as to heat the mold. Again, the disadvantage is that again the thermal mass is very large and the entire mold is heated with. Another disadvantage is also that the distance of the channels leads to heat sinks and thus to an uneven heat distribution.

From the US 2005/0196481 A1 is known a mold for the production of fiber composite components, wherein the mold is formed from an electrically conductive carbon foam, which is connected to an electrical voltage source and energized by applying an electrical voltage, so as to temper the forming tool surface of the mold.

Furthermore, resistance heaters are known in which the molds or the tool surface are energized, wherein due to the electrical resistance of the materials used, the surface or the mold are tempered. For example, from the DE 10 2004 042 422 A1 a mold known in which the resistance heating element consists of a fiber material of a fiber composite material, wherein the fiber material is electrically conductive and connectable to a voltage source, so that upon application of an electrical voltage to the fiber material of the resistance heating, a thermal energy input into the deposited on the tool surface fiber composite component is possible , A similar device is also found in the DE 10 2006 058 198 A1 ,

The disadvantage of this device, however, is the fact that on the one hand the contacting of the existing fiber material resistance heating element is extremely difficult and often leads to problems in practice, because due to the materials used (usually copper or CFRP) and the different thermal expansion coefficients especially at high Temperature differences quickly Material fatigue within the mold at the contact points arise. On the other hand, the mold can be heated only in the whole or in very roughly divided areas, with increasing size of the shaping tool surfaces, the risk of HotSpots and temperature sinks is increased. In other words, the larger the shaping tool surface and the associated integrally formed resistance heating element based on a fiber composite material, the greater the temperature gradient for the entire surface. However, this can lead to damage, distortion or inadmissible component geometry deformation of the component during the temperature control of the fiber composite component to be produced and thus to rejects.

It is therefore an object of the present invention to provide an improved mold and an improved method for producing a fiber composite component, with which the most homogeneous possible temperature distribution over the entire forming tool surface and the risk of material fatigue can be reduced in the contact areas.

The object of the present invention is achieved with the features of claim 1 and the method according to claim 13 according to the invention.

According to claim 1, a mold for the production of a mold component is proposed with a shaping tool surface, which at least partially corresponds to the geometry of the molded component to be produced and which is designed for depositing a material for the production of the mold component. Such a shaped component can be, for example, a fiber composite component which is produced from a fiber composite material.

The molding tool furthermore has a heating module which has at least one electrical resistance heating element which thermally interacts with the shaping tool surface for tempering the deposited molding component. In other words, if an electrical voltage is applied to the electrical resistance heating element, this leads to a heating of the resistance heating element due to the electrical power dissipation in the resistance heating element, so that the shaping tool surface is heated and thus the component deposited thereon is heated.

The electrical resistance heating element is formed from a fiber material of a fiber composite material and has at least two mutually insulated electrical connections in order to contact the electrical resistance heating element with an electrical voltage source. The fiber material of the resistance heating element is connected to the electrical terminals of the heating module so that by contacting the electrical connections with an electrical voltage source and applying an electrical voltage to the electrical connections, a current flow from the one electrical connection through the fiber material of the resistance to the other electrical connection is effected. Because of this, the electric resistance heating element can then be heated.

According to the invention, it is now proposed that the electrical connections are formed from an electrically conductive hard foam. Such an electrically conductive rigid foam can be, for example, a carbon foam. The electrically conductive rigid foam of the electrical connections is electrically connected to the fiber material of the resistance heating element such that upon application of an electrical voltage to the electrical terminals formed from the electrically conductive rigid foam, a current flow through the fiber material of the resistance heating element is effected.

Due to the fact that the electrically conductive rigid foam has a similar to the fiber material of the resistance heating element thermal expansion coefficient occurs in the contacting region of the electrically conductive hard foam with the fiber material of the resistance heating during tempering and production of the molded component to significantly lower material stresses, so that the risk of material fatigue in Connection range of electrical connections and resistance heating element can be significantly reduced. At the same time, the weight of the entire mold is reduced by the use of a hard foam, whereby the handling of especially large molds is significantly simplified. However, this is not at the expense of stability, since as a resistance heating element, a fiber material of a fiber composite material is used, which gives the mold together with the rigid foam used as connections the necessary stability and rigidity.

By using a fiber material of a fiber composite material for an electrical resistance heating element can also be the thermal stresses between the heating module on the one hand and a possibly overlying forming tool surface made of a fiber composite material on the other hand also reduce, in the manufacture of a molded component as a fiber composite component due to the highly similar Thermal expansion coefficients of the materials used Tensions between mold and component during the temperature control can be almost excluded.

Under the formulation that the electrical connections are formed from an electrically conductive rigid foam, in the context of the present invention, it is understood that the electrical connections consist of an electrically conductive hard foam or have such an electrically conductive rigid foam, wherein in particular additional contacting elements in order to avoid the electrical Connections with an electrical voltage source, no longer part of the electrical connections in the context of the present invention.

A fiber composite material is understood in particular to mean a matrix material and corresponding fiber material with which a fiber composite component can be produced by hardening the matrix material. The electrical resistance heating element may comprise an electrically conductive fiber material of a fiber composite material, wherein the electrically conductive fiber material module may be embedded in a cured matrix material. Carbon fiber webs, carbon fiber webs or matrix materials / resins / lacquers enriched with electrically conductive particles are also possible constituents of a fiber composite material.

The electrical connections of the heating module are further designed such that they can be connected to an external electrical voltage source. This can be done, for example, by introducing or inserting copper electrodes into the electrically conductive rigid foam of the electrical connections so as to be able to connect the electrical connections to an electrical voltage source. The copper electrodes may be rod-shaped or cylindrical and may be part of the molding tool or of the heating module.

Advantageously, the resistance heating element and at least the electrical connections made of the electrically conductive rigid foam of the respective heating modules form part of the supporting structure of the molding tool.

Advantageously, the electrical resistance heating element is designed such that it lies substantially parallel to the shaping tool surface. Substantially parallel here means that the resistance heating element is arranged so that the current flow is substantially parallel to the surface. Accordingly, the fiber material of the resistance heating element is arranged so that the fiber path or the fiber direction is substantially parallel or coaxial with the forming tool surface.

In an advantageous embodiment, the molding tool has a hard foam core for stabilizing the shape, wherein the at least one heating module, preferably a plurality of heating modules, is arranged between the shaping tool surface and the rigid foam core of the molding tool with the electrical resistance heating element and the electrical connections formed from the electrically conductive rigid foam. By using a hard foam core for the molding tool, the weight of the molding tool as a whole can be drastically reduced, in particular in the case of large components, the rigid foam core having a lower density than the terminals of the heating module formed from the electrically conductive rigid foam.

Advantageously, the rigid foam core of the molding tool forms, together with the resistance heating element and the respective electrical connections made of the electrically conductive rigid foam of the individual heating modules, a part of the supporting structure of the molding tool, in particular the essential part of the supporting structure.

If the hard foam core is likewise formed from an electrically conductive hard foam, the hard foam core is preferably insulated from the heating module and electrical connections.

In a particularly advantageous embodiment, the electrical connections of the at least one heating module form part of the hard foam core of the molding tool.

In a further advantageous embodiment, the fiber material of the resistance heating element is arranged substantially parallel to the shaping tool surface, wherein the fiber material is contacted at two opposite ends with the electrical terminals of the electrically conductive rigid foam. Preferably, the two ends are to be chosen so that they are in the fiber direction, i. the current flow in the fiber direction is effected when an electrical voltage is applied to the electrical connections.

In this case, it is conceivable, for example, for the fiber material to be bent at the two ends and run in the direction of the forming tool (counter to the shaping tool surface), wherein the electrical connections from the electrically conductive rigid foam are then formed on the angled limbs of the fiber material.

It is in principle conceivable that the electrical connections extend parallelepipedally or in another physical form from the fiber material in the direction of the forming tool (opposite to the shaping tool surface), so that a heating module is formed, which also forms a spatial component in addition to the fiber layer of the resistance heating element having the electrical connections from the electrically conductive rigid foam.

In such an embodiment, it is for example very particularly advantageous if between the two electrical connections of the heating module a Heizmodulkern is formed, which is bounded on two opposite sides by the electrical connections and on another side by the resistance heating, wherein the Heizmodulkern preferably from a Hard foam is formed and has a lower density than the electrical connections. If the heating module is inserted into the molding tool, the heating module is then delimited by the molding tool on the opposite side bounding the resistance heating element. If several heating modules are inserted in the form of a mosaic, the heating module core may also be delimited by the adjoining adjoining heating modules.

Advantageously, the rigid foam core of the molding tool together with the resistance heating element, the heating module core and the respective electrical connections made of the electrically conductive rigid foam of the individual heating modules forms part of the supporting structure of the molding tool, in particular the supporting structure.

The Heizmodulkern is electrically isolated from the terminals. Due to the lower density of the Heizmodulkerns compared to the electrical connections can also be achieved that the weight of the heating module is significantly reduced, without sacrificing the stability and rigidity of the heating modules in purchasing.

Advantageously, the electrical connections made of the electrically conductive hard foam have an electrical cross section which is greater than the electrical cross section of the fiber material of the resistance heating element. In this way it can be prevented that due to an applied electrical voltage, the electrical connections are tempered instead of the electrical resistance heating element. Because the electrical connections from the electrically conductive rigid foam generally have a lower, preferably significantly lower density than the fiber material of the resistance heating element.

By adapting the electrical cross-section of the electrical connections, however, the temperature gradient can be adjusted when the heating module is being tempered in the edge regions, which is e.g. is preferably advantageous if the heating module is used in an edge region of the mold.

As already mentioned, it is particularly advantageous if a plurality of separate heating modules are provided, which are arranged in the tool. As a result, the heating range of the molding tool can be adapted to the component size or component geometry so that one and the same molding tool can definitely be used for a plurality of different component sizes. For this purpose, the heating modules are arranged in the mold so that they are particularly solvable and can be removed from the mold or optionally used.

In this case, it is conceivable, for example, for each heating module to be connected and connected separately to the electrical voltage source, wherein heating modules arranged adjacently in the molding tool are provided with electrical insulation with regard to their electrical connections. As a result, the heating modules can be introduced directly adjacent to their electrical connections in the mold, wherein an insulating layer is provided between the electrical terminals of adjacent heating modules.

For this purpose, the molding tool has heating module receptacles into which the heating modules can be inserted, wherein the heating module receptacle has an electrical contact device with which each individual heating module can then be connected via its respective electrical connections of the electrical voltage source. For example, it is conceivable that the electrical contact device has a plurality of rod-shaped copper electrodes which are contacted with the electrical connections of the heating modules so as to connect the heating modules to the electrical voltage source.

However, it is also conceivable that the electrical connections are not provided insulating on their side surfaces, so that adjacent heating modules electrically contact with their respective opposite electrical terminals and so a series connection of the heating modules is possible.

In a further advantageous embodiment, the fiber material of the resistance heating element is interspersed with a hardened matrix material and thus forms the shaping tool surface. However, it is also conceivable for an insulating material layer made of a non-conductive material, for example a non-conductive fiber material such as glass fiber, to be laid over the heating modules (or the heating module) or via the resistance heating element of the respective heating modules and interspersed with a matrix material form non-conductive, shaping tool surface, which is then thermally in operative connection with the resistance heating elements of the heating modules to temper a stored on the forming tool surface mold component.

In an advantageous embodiment, the mold is segmented depending on a component thickness distribution of the molded component to be produced, wherein in particular regions of the mold component are provided with a relation to the rest of the mold component higher component thickness with separate heating modules. These can then be controlled by means of a voltage control separately for applying an electrical voltage so that areas with a larger component thickness receive a higher heat input than other areas. In this way, the mold can be segmented by the heating modules according to the geometry and the component thickness distribution and thus control the heat input for each segment targeted.

• 1 - Schematische Darstellung des erfindungsgemäßen Formwerkzeugs;
• 2 - Schematisch-Perspektivische Darstellung des erfindungsgemäßen Halsmoduls;
• 3 - Detaillierte schematische Darstellung des Heizmoduls.

The invention will be explained by way of example with reference to the attached figures. Show it:

• 1 - Schematic representation of the mold according to the invention;
• 2 - Schematic perspective view of the neck module according to the invention;
• 3 - Detailed schematic representation of the heating module.

1 schematically shows a mold 10 in which a plurality of heating modules 20 , which will be explained later with respect to their construction, are provided. The heating modules 20 are on a hard foam core 11 arranged, the mold 10 to give it sufficient stability with the lowest possible weight. Above the heating modules 20 there is a shaping tool surface 12 , which may be formed for example in the form of a glass fiber or carbon fiber cover layer and the mold 10 lends its formative function. By using a fiber composite material for the forming tool surface 12 Moreover, it is possible to produce a very stable and, moreover, lightweight tool surface, which in total is the mold 10 gives its favorable weight-specific strength and rigidity.

The individual heating modules are in the embodiment of 1 via copper connectors 13 with an electrical power source 14 connected to the so in the heating modules 20 integrated electrical resistance heating element to energize and thus the temperature entry in a on the forming tool surface 12 stored fiber composite component (not shown) to ensure.

The hard foam core and the heating modules 20 For example, in a floor pan 15 of the mold 10 are arranged, wherein the hard foam core 11 for example, using a high-temperature adhesive 16 with the floor pan 15 can be glued. Such a high-temperature adhesive can also be used for bonding the shaping tool surface 12 with the heating modules 20 used, provided the heating modules 20 should be designed fixed and not interchangeable.

It is also conceivable that the heating modules 20 in each case a part of the shaping tool surface 12 form, so that a further top layer is not necessary. Furthermore, the heating modules are variable and detachable in the mold 10 arranged, they can be exchanged if necessary, whereby the heating range can be adapted to the prevailing conditions.

2 shows in a perspective schematic representation of the three-dimensional heating module 20 , On the top of the heating module 20 is the electrical resistance heating element 21 provided, which is formed from a fiber composite material whose fiber material is electrically conductive. In the connection areas 22a and 22b is the electrical resistance heating element 21 with electrical connections 23a and 23b contacted, for example, with the copper compounds 13 out 1 can be connected.

The electrical connections 23a and 23b are made of an electrically conductive hard foam and can thus flow through the electrical resistance heating element 21 when applying an electrical voltage effect. The electrical connections 23a and 23b From the electrically conductive hard foam are formed as a shaped body and have at least in one direction a substantially identical extension to the electric heating element 21 on.

The two electrical connections 23a and 23b are provided mutually electrically insulating. Between the two connections 23a and 23b is a heating module core 24 provided that the two electrical connections 23a and 23b electrically isolated from each other and at the same time the heating module 20 stabilized. This is the Heizmodulkern 24 on one side of the electrical connection 23a limited and on the opposite side of the electrical connection 23b limited, while also one of the two terminals 23a and 23b enclosed upper sides of the Heizmodulkern 24 from the electrical resistance heating element 21 is limited. Will the heating module 20 in the mold according to 1 used, it will be at the to the electrical resistance heating element 21 opposite side of the hard foam core 11 of the mold 10 limited.

Advantageously, the heating module core is likewise formed from a rigid foam, the rigid foam of the heating module core 24 has a lower density than the electrical connections 23a and 23b , Thus, the weight of such a heating module can be further reduced, whereby the weight of the entire mold is reduced overall further.

With such a heating module 20 is a segmentation of the mold surface in different heating zones possible. A heating zone can consist of several of the described heating modules 20 consist. In addition, with such a heating module, a uniform temperature control of the entire surface of the electrical resistance heating element 21 possible, wherein the temperature gradient at the edge regions of the heating module 20 significantly lower compared to conventional methods. Thus, the component can be uniformly tempered during manufacture.

It is thus achieved as uniform as possible heat distribution within the heating module.

3 shows the heating module 20 in a sectional view. In this embodiment, both the electrical connections 23a and 23b as well as the heating module core 24 formed of an electrically conductive hard foam, which may be for example a carbon foam. To avoid an electrical short circuit, the electrical connections 23a and 23b opposite the heating module core 24 using an insulating layer 25 provided electrically insulating. In addition, in the embodiment of 3 the electrically conductive resistance heating element 21 opposite the electrical connections 23a and 23b as well as towards the heating module core 24 using the insulating layer 25 arranged electrically insulated. Only in the transition areas or contacting areas 22a and 22b are the respective electrical connections with the electrical resistance heating element 21 electrically contacted.

In the embodiment of 3 is the electrical resistance heating element 21 bent at an angle towards the mold and contacted the respective connections 23a and 23b on a side surface of the heating module 20 , This is useful, for example, if several heating modules are to be connected in series.

LIST OF REFERENCE NUMBERS

10 -

mold

11 -

Rigid foam core

12 -

tool surface

13 -

copper connector

14 -

electrical voltage source

15 -

floor pan

16 -

Foam adhesive

20 -

heating module

21 -

electrical resistance heating element

22a, 22b -

lands

23a, 23b -

electrical connections

24 -

Rigid foam core

25 -

insulating

Claims (15)

Mold (10) for the production of a molded part by supplying heat with a forming tool surface (12) which at least partially corresponds to the geometry of the molded component to be produced and which is designed for depositing a material for producing the molded component, and at least one heating module (20 ), which has at least one electrical resistance heating element (21) which cooperates thermally with the forming tool surface (12) for tempering the deposited molded component, wherein the electrical resistance heating element (21) formed from a fiber material of a fiber composite material and having at least two mutually insulated electrical connections ( 23a, 23b) for electrically contacting the electrical resistance heating element (21) is connected to an electrical voltage source (14), characterized in that the electrical connections (23a, 23b) are formed from an electrically conductive hard foam. Forming tool (10) after Claim 1 characterized in that the molding tool (10) has a rigid foam core (11) for stabilizing the shape, wherein between the forming tool surface (12) and the hard foam core (11) of the molding tool (10) the at least one Heating module (20) with the electrical resistance heating element (21) and the electrical connections formed from the electrically conductive foam (23a, 23b) is arranged. Forming tool (10) after Claim 2 , characterized in that the electrical connections (23a, 23b) of the at least one heating module (20) form part of the hard foam core (11) of the molding tool (10). Mold (10) according to one of the preceding claims, characterized in that the fiber material of the resistance heating element (21) is arranged substantially parallel to the forming tool surface (12), wherein the fiber material at two opposite ends with the electrical terminals (23a, 23b) is contacted from the electrically conductive foam. Forming tool (10) according to one of the preceding claims, characterized in that between the two electrical terminals (23a, 23b) of the heating module (20) a Heizmodulkern is formed on two opposite sides by the electrical connections (23a, 23b) and another side is limited by the resistance heating element (21). Forming tool (10) after Claim 5 , characterized in that the Heizmodulkern is formed from a rigid foam and has a lower density than the electrical connections (23a, 23b). Mold (10) according to one of the preceding claims, characterized in that a plurality of separate heating modules (20) are provided, which are arranged in the mold (10). Forming tool (10) after Claim 7 , characterized in that each heating module (20) is separately connected or connectable to the electrical voltage source (14), wherein in the mold (10) adjacently arranged heating modules (20) with respect to their electrical connections (23a, 23b) are provided electrically insulating. Forming tool (10) after Claim 7 , characterized in that in the mold (10) adjacently arranged heating modules (20) via their adjacent electrical connections (23a, 23b) are electrically connected to each other. Mold (10) according to one of the preceding claims, characterized in that the mold (10) has a Heizmodulaufnahme, in which one or more heating modules (20) can be used, wherein the Heizmodulaufnahme has an electrical contact means with which the electrical connections (23a , 23b) of the heating modules (20) can be connected to the electrical voltage source (14) when the heating modules (20) are inserted into the mold (10). Mold (10) according to one of the preceding claims, characterized in that the hard foam is an electrically conductive carbon foam. Mold (10) according to one of the preceding claims, characterized in that the fiber material of the resistance heating element (21) is interspersed with a cured matrix material and forms the forming tool surface or that the fiber material of the resistance heating element (21) is interspersed with a cured matrix material and on the Resistance heating a further layer of material is arranged, which is different from the resistance heating element and forms the forming tool surface. Method for producing a fiber composite component with the steps: a) providing a molding tool (10) according to one of the preceding claims; b) depositing fiber material of a fiber composite material on the shaping tool surface (12) of the molding tool (10); and c) curing the fiber material passing through matrix material by tempering the fiber and matrix material by an electrical voltage to the terminals (23a, 23b) of the one heating module (20) or the plurality of heating modules (20) by means of an electrical voltage source (14) is applied , Method according to Claim 13 , characterized in that one or more heating modules (20) in the mold (10) are used in dependence on the geometric dimension of the fiber composite component to be produced. Method according to Claim 13 or 14 , characterized in that depending on a component thickness distribution of the molded component to be produced by the heating modules defined segmentation of the mold and / or controlled by a voltage control the voltage applied to the individual heating modules electrical voltage in dependence on a component thickness distribution of the molded part to be produced.

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