Abstract:
The present invention provides a method for producing a fiber composite component, the method comprising arranging a first and a second mold in relation to one another in such a way that these together form a first cavity; laying a fiber material on the first and/or second mold; filling the first cavity with a casting material and solidifying the casting material in order to seal the first and second molds to one another and/or to interconnect them; and infiltrating the fiber material with a matrix and curing the matrix to form the fiber composite component.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of and claims priority to PCT/EP2012/054638, filed Mar. 16, 2012, which claims the benefit of and priority to U.S. Provisional Application No. 61/467,181, filed Mar. 24, 2011, and German Patent Application No. 10 2011 006 047.2, filed Mar. 24, 2011, the entire disclosures of which are herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and a device for producing a fiber composite component. 
     BACKGROUND OF THE INVENTION 
     The production of fiber composite components via infusion and injection methods is generally known. For example, in what is known as “resin transfer molding”, a device which comprises a lower and an upper mold is used. A fiber material is arranged in a cavity formed between the two molds, whereupon a vacuum is applied to the cavity and at the same time a matrix under pressure is injected into the cavity. However, it is necessary to seal the two molds to one another beforehand. This is achieved in a known manner by providing elastomeric sealing profiles between the two molds. In order for the seal ensured by means of the sealing profiles to be sufficient to maintain the vacuum, the molds must also be pressed together with a high pressing force. A pressing force of this type is generally provided by complex hydraulics, which are expensive. It has also been found that in some cases sufficient tightness cannot be achieved, despite the high pressing force. 
     In a vacuum infusion method described in DE 10 2007 061 431 A1, a fiber material is arranged on a laminating device and covered with a vacuum film. In order to achieve sufficient tightness between the vacuum film and the laminating device, corresponding sealing tapes, also referred to as “tacky tape”, are inserted between the vacuum film and the laminating device. 
     SUMMARY OF THE INVENTION 
     An idea of the present invention is to provide an improved method and an improved device for producing a fiber composite component, which in particular at least reduce the above-described drawbacks. 
     According to the invention, the following are provided: 
     A method for producing a fiber composite component, comprising the following steps: arranging a first and a second mold in relation to one another in such a way that these together form a first cavity, laying a fiber material on the first and/or second mold, filling the formed first cavity with a casting material and solidifying said casting material in order to seal the first and the second mold to one another and/or interconnect them, infiltrating the fiber material with a matrix and curing said matrix to form the fiber composite component. 
     Additionally, a device for producing a fiber composite component, in particular for carrying out the method according to the invention, comprising a first and a second mold which together form a first cavity, a means for melting a casting material for filling the formed first cavity and solidifying the casting material therein in order to seal the first and the second mold to one another and/or interconnect them, a means for infiltrating with a matrix a fiber material which can be arranged on the first and/or second mold, and a means for curing the matrix to form the fiber composite component. 
     The idea on which the present invention is based consists in providing tightness between a first and a second mold by means of a casting material and/or interconnecting a first and a second mold by means of a casting material. 
     The use of a casting material is associated with the advantage that a very high degree of tightness can be achieved without having to exert a pressing force on the two molds. In addition, by means of the casting material a connection between the first and the second mold can be provided in a simple manner. 
     In particular, when solidified the solidified casting material seals a joint between the first and the second mold. Additionally or alternatively, the solidified casting material interconnects the two molds with a positive fit in the region of their joint. 
     A large number of applications of the method according to the invention and the device according to the invention are contemplated. For example, the two molds can be interconnected and/or sealed to one another in order together to form a substantially planar or contoured laminating device on which a fiber composite component is constructed. The first and the second mold can also be interconnected and/or sealed to one another in order together to form a mold core by means of which a fiber composite component is constructed. In this case, the mold core occupies in particular a cavity of the formed fiber composite component. The two molds can also be interconnected and/or sealed to one another in order to form a second cavity in which the fiber material is infiltrated with the matrix. 
     The order of the steps given in the method claim can be varied. In particular, the step of arranging the fiber material on the first and/or the second mold can take place before or after the step of arranging the first and the second mold in relation to one another in such a way that the first and the second recess together form a first cavity. 
     Advantageous configurations of the present invention emerge from the dependent claims. 
     “fiber material” is understood herein to mean in particular a woven fabric, a non-woven fabric or a fiber mat. “Matrix” is to be understood to mean in particular a thermosetting or thermoplastic matrix. 
     “Infiltration” is to be understood to mean providing the fiber material with a matrix in any manner. In particular, “infiltration” includes infusion and injection methods. 
     According to a configuration of the method according to the invention, the first mold comprises a first recess and the second mold comprises a second recess, which recesses together form the first cavity. As a result, the first cavity is created in a simple manner. Alternatively, it is also possible for only one of the two molds to comprise a recess, which together with a planar face of the respective other mold forms the first cavity. 
     According to a configuration of the method according to the invention, a chamber contains the casting material prior to the filling step, the casting material flowing from the chamber into the first cavity when said material is heated beyond its melting point. As a result, the casting material can be transferred between the chamber and the cavity in a simple manner, in particular merely by controlling the temperature of the casting material. 
     According to a further configuration of the method according to the invention, the chamber is formed in the first and/or the second mold. This results in a compact construction. Alternatively, the chamber can also be provided outside the two molds. 
     According to a further configuration of the method according to the invention, the chamber is arranged above the first cavity prior to the filling step. The casting material thus flows from the chamber into the first cavity automatically under the effect of gravity. 
     According to a further configuration of the method according to the invention, the first and the second recess each comprise an undercut, in such a way that the first and the second mold are interconnected with a positive fit after filling with and solidification of the casting material. As a result, a rigid connection between the first and the second mold can be produced in a simple manner. 
     According to a further configuration of the method according to the invention, the casting material is re-melted after the matrix has been cured, whereby the seal and/or the connection between the first and the second mold is removed. As a result, the seal and/or the in particular positive connection between the first and the second mold can easily be removed again. There is also the option of turning the first and the second mold over prior to re-melting the casting material, in such a way that the first cavity is arranged above the chamber, whereby the casting material flows from the first cavity back into the chamber once it has been melted. 
     According to a further configuration of the method according to the invention, the first and the second mold are arranged in relation to one another in such a way that they together form a second cavity, at least in portions, which cavity receives the fiber material, whereupon the first and the second mold are sealed to one another by filling the first cavity with the casting material and solidifying said casting material. “Together form a second cavity, at least in portions” is to be understood to mean that the first and the second mold can form only a part of a wall defining the second cavity. For example, a third and a fourth mold which are formed in accordance with the first and the second molds can also be provided, in such a way that the second cavity is defined by a total of four molds. The first and the second molds can thus for example be formed as two half-shells which form between them the second cavity. Alternatively, the first, second, third and fourth molds can each be formed as a quarter-shell, which quarter-shells form between them the second cavity. The two molds are preferably also interconnected with a positive fit by filling with the casting material and solidifying it. 
     According to a further configuration of the method according to the invention, a pressure or vacuum is applied to the second cavity in order to infiltrate the fiber material in the second cavity with the matrix. This configuration basically corresponds to what is known per se as “resin transfer molding” (hereinafter “RTM method”). 
     According to a further configuration of the method according to the invention, the fiber material is packed in a film which is sealed from the first and the second mold, whereupon a vacuum is applied in order to infiltrate the fiber material with the matrix. This configuration basically corresponds to the vacuum infusion method known per se and represents an alternative to the RTM method. In the present case, “film” also comprises a semi-permeable membrane. 
     According to a further configuration of the method according to the invention, the fiber material is arranged on the first and/or the second mold prior to the formation of the second cavity. The fiber material is thus preferably arranged on the first and/or the second mold when the molds are open, and the molds are subsequently closed to form the second cavity with the fiber material inside. 
     According to a further configuration of the method according to the invention, the first and/or the second mold have a shell shape. Alternatively, at least one of the two molds can have a U-shaped cross-section. These mold shapes are particularly suitable for forming the second cavity between them. 
     According to a further configuration of the method according to the invention, the casting material has a melting point which is below the decomposition temperature of the matrix. “Decomposition temperature” is to be understood to mean the temperature at which the polymer chains in the matrix thermally decompose. This configuration is advantageous in that, when the first and the second mold are heated after the step of curing the matrix, in order thereby to melt the casting material, a disadvantageous decomposition of the matrix is avoided. 
     According to a further configuration of the method according to the invention, the fiber material and the casting material are heated via the same heater in order to infiltrate and/or cure the fiber material and melt the casting material. Thus, advantageously, only one heater is required. 
     According to a further configuration of the method according to the invention, the casting material is heated via a first heater in order to melt said casting material and the fiber material is heated via a second heater in order to infiltrate and/or cure said fiber material. As a result, the temperature of the casting material can advantageously be controlled independently of that of the fiber material and of the fiber material comprising the matrix. 
     According to a further configuration of the method according to the invention, the casting material is formed as a lead-zinc alloy, in particular having a melting point between 183 and 195° C. Alloys of this type are particularly suitable owing to their low melting point. Alternatively, the casting material could also be formed as a polymer, in particular as a plastics material or silicone. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described in detail below by way of embodiments with reference to the appended figures of the drawings, in which: 
         FIG. 1A to 1C  are each a sectional view through a device according to an embodiment of the present invention in various operating states; 
         FIG. 2A to 2C  are each a sectional view through a device according to a further embodiment of the present invention in various operating states; and 
         FIG. 3  shows a temperature profile for the device according to  FIG. 1A to 1C or 2A to 2C . 
     
    
    
     In the figures, like reference numerals denote like or functionally like components unless stated otherwise. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1A  is a sectional view of a device  100  according to an embodiment of the present invention in a first operating state. 
     The device  100  comprises a first and a second mold  102 ,  104 . According to the present embodiment, the device  100  is formed symmetrically about an axis of symmetry  106 . The following descriptions thus apply accordingly for the right-hand side (not shown in  FIG. 1A ) of the device  100 . 
     According to the present embodiment, the first and the second mold  102 ,  104  are each formed as a half-shell, which half-shells rest against one another along a joint  108  in the closed state shown in  FIG. 1A . The molds  102 ,  104  thus complement one another to form a cylinder, the end faces of which (not shown, since these are located outside the plane of projection) can respectively also comprise a joint corresponding to the joint  108  or be closed in another manner. The molds  102 ,  104  define between them a cavity  110  which, in the operating state shown in  FIG. 1A , is connected to the atmosphere  112  via the joint  108 , which does not ensure pressure-tight closure. 
     The mold  102 , which in  FIG. 1A  is arranged at the top in relation to the ground (not shown), comprises a chamber  114 . In the first operating state shown in  FIG. 1A , the chamber  114  is filled with a casting material  116  in a solid state. Below the chamber  114 , the first mold  102  comprises a recess  118  which is open towards the joint  108 . Opposite the recess  118 , the second mold  104  comprises a recess  120  which is also open toward the joint  108 . When the first and second molds  102 ,  104  are closed, as shown in  FIG. 1A , the recesses  118 ,  120  together form a cavity  122 . The cavity  122  is closed apart from an opening towards the chamber  114 . The recesses  118 ,  120  can comprise an undercut  124 ,  126  at their respective end remote from the joint  108 . Alternatively,  FIG. 2A to 2C  show an embodiment of the device  100  which does not comprise the undercuts  124 ,  126 . 
     The closed state of the molds  102 ,  104  is preceded by an open state of the molds  102 ,  104  in which a fiber material is arranged in the cavity  110 , which is accessible from the outside when the molds  102 ,  104  are open. For better clarity, the fiber material is shown only in  FIG. 1B  and denoted by reference numeral  128 . The fiber material  128  can in particular be a fiber preform which was constructed in a preceding method step and in particular fills the entire cavity  110  (not shown). For example, the fiber preform can consist of a plurality of non-woven layers which are sewn together or interconnected by means of a powder binder. When the molds  102 ,  104  are open, the fiber material  128  is arranged on each of them or only on one of the two molds  102 ,  104 . The molds  102 ,  104  are then brought into their closed state shown in  FIG. 1A to 10 , but the cavity  110  remains connected to the atmosphere  112  via the joint  108  owing to certain leaks. 
     The casting material  116  is then heated. The casting material  116  can in particular be a meltable metal, for example a lead-zinc alloy. The casting material  116  can be heated in a variety of ways. For example, the device  100  can comprise a heater  130  which is formed to heat the first and the second mold  102 ,  104  collectively, the casting material  116  then also being heated. For better clarity, the heater  130  is shown only in  FIG. 1B . Alternatively or additionally, a heater  132  can be provided in the immediate vicinity of the chamber  114  and the cavity  122 , which heater is set up to heat basically only the casting material  116  in the chamber  114  and in the cavity  122  (see  FIG. 1B ). 
     The following descriptions relate to a heating process using exclusively the heater  130 . In this case, the casting material  116  and the fiber material  128  comprising the matrix  134  have basically the same temperature profile, shown in  FIG. 3 . The heater  130  can be integrated into one of the two molds  102 ,  104  or into the two molds  102 ,  104 . 
     Starting from the solid state of the casting material  116 , which at this time S 1  (see  FIG. 3 ) has a temperature T 1  (typically ambient temperature), said casting material is heated to a temperature T 2  at a time S 2 . The temperature T 2  is higher than the melting point T 6  of the casting material  116 . The melting point T 6  is typically 185° C. The temperature T 2  may be 190° C., for example. The casting material  116  then flows downwards into the cavity  122  owing to the effect of gravity and fills said cavity (see  FIG. 1B ). 
     The temperature T 2  of the casting material  116  in the cavity  122  is then reduced again at a time S 3 , in such a way that the casting material  116  assumes the temperature T 3  at a time S 4 . The temperature T 3  is selected in such a way that it is suitable for infiltrating the fiber material  128  with a matrix  134  (see  FIG. 1B ). In other words, at the time S 4  the first and the second mold  102 ,  104  have a temperature T 3  at which the matrix  134  is sufficiently free-flowing to infiltrate the fiber material  128 . The temperature T 3  is typically 120° C. At this temperature the casting material  116  has solidified again and thus seals the joint  108  (see  FIG. 1B ) in a gas-tight and liquid-tight manner. Owing to the undercuts  124 ,  126 , when solid (see  FIG. 1B ) the casting material  116  also rigidly interconnects the molds  102 ,  104  in a direction perpendicular to the joint  108 . 
     In a further method step, a vacuum is then applied to the cavity  110 , which is sealed in a pressure-tight manner apart from a corresponding vacuum connection, and the matrix  134  is conveyed under pressure into the fiber material  128 . The applied vacuum ensures that in particular all the gas bubbles are removed from the matrix  134 , which advantageously influences the quality of the fiber composite component produced. A corresponding vacuum pump for producing the vacuum is denoted by reference numeral  136  in  FIG. 1B . 
     For example, the infiltration of the fiber material  128  with the matrix  134  may be complete at a time S 5  (see  FIG. 3 ), whereupon the temperature of the first and the second mold  102 ,  104  and thus of the fiber material  128  including the matrix  134  is increased to the temperature T 4  at a time S 6 . The temperature T 4  corresponds to a curing temperature for curing the matrix  134 . The curing temperature T 4  is, for example, 180° C. and is thus lower than the melting point T 6  of the casting material  116 , in order not to compromise the tightness of the molds  102 ,  104 . 
     After curing the matrix  134  at a time S 7  (see  FIG. 3 ), the molds  102 ,  104  are rotated in such a way that the cavity  122  is henceforth arranged at the top in relation to the chamber  114  (see  FIG. 1C ). The rotation of the molds  102 ,  104  is indicated by an arrow between  FIGS. 1B and 1C . At a time S 8  (see  FIG. 3 ), the temperature of the casting material  116  is then brought back to the temperature T 2  above the melting point T 6  of the casting material  116 . 
     The temperature T 2  is lower than a decomposition temperature T 5  of the matrix  134 , and so the matrix  134  is not damaged when heated (owing to the heating of the casting material  116 ) at time S 8 . 
     The casting material  116  in the cavity  122  then melts and subsequently flows into the chamber  114  owing to the effect of gravity. The molds  102 ,  104  can thus be re-opened and the then finished fiber composite component  138  (see  FIG. 1B ) removed. 
     From a time S 9  (see  FIG. 3 ), the casting material  116  in the chamber  114  cools from the temperature T 2  back to a temperature below the melting point T 6 , in particular to the temperature T 1  (ambient temperature). The molds  102 ,  104  can then be rotated again and thus brought into the operating state shown in  FIG. 1A . 
     According to an alternative embodiment, the heater  132  can also be provided. In this case, the temperature of the casting material  116  in the chamber  114  and in the cavity  122  can be controlled basically independently of the temperature of the fiber material  128  and of the fiber material  128  including the matrix  134 . The casting material  116  could thus have the temperature profile shown in  FIG. 3  until the time S 4 , while the fiber material  128  is basically at the temperature T 1 , that is to say ambient temperature. In this case, the temperature of the casting material  116  is controlled via the heater  132 . The temperature of the fiber material  128  is then brought to the temperature T 3  in order to make it possible to infiltrate said fiber material with the matrix  134 , which requires sufficient fluidity of the matrix  134 . This is done via the heater  130 , which in this embodiment heats only the cavity  110  comprising the fiber material  128 . In the time frame S 4  to S 7 , the temperature of the casting material  116  can again be the temperature T 1  (ambient temperature) or a slightly higher temperature (owing to the waste heat from the cavity  110 ). When curing of the matrix  134  is complete at time S 7 , the temperature of the fiber material  128  comprising the matrix  134  is lowered to the temperature T 1  (ambient temperature) again, while the temperature of the casting material  116  is increased via the heater  132  to the temperature T 2  to melt the casting material  116 . 
     The temperature T 2  (see  FIG. 3 ) in the time frame S 2  to S 3  can also be above the decomposition temperature of the matrix  134 , since this is only introduced into the cavity  110  afterwards. 
     According to a further embodiment, a film  140  (see  FIG. 1B ) is laid over the fiber material  128  on the inside before or after closing the molds  102 ,  104 . For this purpose, the fiber material  128  is for example arranged in the form of one or more layers (the embodiment having one layer is shown in  FIG. 1B ) on the molds  102 ,  104 . In other words, the fiber material  128  does not fill the cavity  110 , as is preferably the case in the previous embodiment. For better clarity,  FIG. 1B  shows only a short portion of the film  140 . The film  140  is then sealed from the molds  102 ,  104 , for example by means of a sealing tape (not shown). A vacuum is then applied by means of the vacuum pump  136  to the volume formed between the foil  140  and the molds  102 ,  104 . As a result, the matrix  134  is drawn into the formed volume, said matrix then infiltrating the fiber material  128 . In this case, the end faces of the cylinder formed by the first and the second mold  102 ,  104  can be formed in an open, that is to say pressure-conducting manner, since a vacuum does not need to be applied to the cavity  110 . In this case, the configurations described in connection with  FIG. 1A to 1C  apply accordingly. 
       FIG. 2A to 2C  show a further embodiment of the device  100 ,  FIG. 2A to 2C  corresponding to  FIG. 1A to 10 . 
     In contrast to the embodiment according to  FIG. 1A to 10 , in the embodiment according to  FIG. 2A to 2C  each of the molds  102 ,  104  has a U-shaped cross-section. A respective U-shape is made up of two arms  200  (owing to the mode of representation in  FIG. 2A to 2C  only one of the arms  200  is shown) and an arm  202  connecting the arms  200 . This results in a rectangular cross-section for the cavity  110 , in such a way that fiber composite components  138  having a rectangular outer geometry can be produced therein. 
     In addition, each of the recesses  118 ,  120  is semi-circular, in such a way that the cavity  122  has a circular or oval cross-section. The cavity  122  and the recesses  118 ,  120  have no undercut, in such a way that in the state shown in  FIG. 2B  the casting material  116  merely ensures sealing of the joint  108  and does not interconnect the first and the second mold  102 ,  104  with a positive fit, as is the case in the embodiment according to  FIG. 1A to 10 . For the sake of simplicity, the fiber composite material  138  and the components  128 ,  134  thereof are not shown in  FIG. 2A to 2C . 
     Although the invention has been described herein by way of preferred embodiments, it is in no way limited thereto, but rather can be modified in a variety of ways. In particular, the configurations and embodiments described herein for the method according to the invention can be applied accordingly to the device according to the invention and vice versa. Furthermore, in the present case “a” does not rule out a plurality.