DE102011114964A1 - Tool for production of moldings from fiber-reinforced composites, has diaphragm expanded by deployment unit, which are adapted and configured, such that fiber web is pressed at predetermined point against lower die half - Google Patents

Abstract

The tool comprises an upper die half (1) and a lower die half (2). A diaphragm (3) is provided in the upper die half in a state bulging in the direction of lower die half. A fiber web (4) is arranged between diaphragm and lower mold half. The diaphragm is expanded by diaphragm deployment unit (5), which are adapted and configured, such that the fiber web is pressed at a predetermined point (7) against the lower die half by pre-triggered portion (6) of diaphragm and the diaphragm is pressed against the lower die half, by applying resin (9) on the fiber web. An independent claim is included for a method for manufacturing moldings from composites.

Description

The invention relates to an apparatus and a method for producing shaped bodies made of fiber composite materials.

Shaped bodies made of fiber composite materials, such as continuous fiber reinforced parts, are produced today, for example, by the RTM process (resin transfer molding process). In this process, a glass or carbon fiber fabric is placed in a solid tool. After closing the tool, the fibrous tissue is impregnated by means of injection of a matrix material or resin into the mold. Then the resin reacts, hardens and after opening the tool, the hardened part can be removed.

In addition, the Compression-RTM method is also used. This process is similar to the ordinary RTM process, however, the resin is injected even before the tool is completely closed, so that the resin is "stamped" in the further closing operation, i. H. is distributed in the mold and pressed into the fiber web. As a result, a better and faster impregnation of the fiber fabric and a lower distortion of the tissue is achieved because the resin does not have to flow completely longitudinally through the tissue as in the RTM process.

From the DE 10 2009 017 512 A1 For example, an apparatus and a method for producing a composite component are known. The tool described therein comprises a first mold, a second mold and a pressure generating means. A membrane is arranged between the first mold and the second mold, so that a first region is formed between the first mold and the membrane, and a second region is formed between the second mold and the membrane. In the first area a fiber mat is arranged. In the second region, a back pressure can be produced by the pressure generating means, so that the membrane is pressed in the direction of the fiber mat. The fiber mat is either soaked in resin or impregnated with resin. In the manufacture of a composite component, a membrane is placed on the second mold and thereon a fiber mat. Subsequently, the tool is closed so that now the first area and the second area are sealed by seals against the environment of the tool. Following this, the second area between the membrane and the second mold is pressurized via an air supply or fluid supply. Following this, a resin feed takes place in the first region between the membrane and the first tool. By pressing the membrane in the direction of the fiber mat, the shrinkage or the change in volume of the semifinished fiber product resulting from the reaction of the resin during the solidification can be compensated during the injection.

A disadvantage of this type of production, however, is the slow impregnation of the fiber fabric, which leads to long cycle times.

An object of the invention is to provide an improved tool and an improved method for producing molded articles from fiber composites.

This object is achieved by a tool for producing shaped bodies from fiber composites according to claim 1 and by a method for producing molded bodies from fiber composites according to claim 10.

Advantageous developments are the subject of the dependent claims.

According to the invention, the tool or the device for producing shaped bodies from fiber composite materials has a first, for example, upper mold half and a second, for example, lower mold half. On the upper mold half a membrane is mounted, which is vorwölbbar in the direction of the lower mold half, wherein between the membrane and the lower mold half a fiber fabric can be arranged. Furthermore, the tool has a membrane unfolding means for pre-arching the membrane. The tool is characterized in that the membrane and the membrane unfolding means are adapted and formed such that a protruding part of the membrane presses the fibrous web against the lower mold half at a predetermined location and subsequently exerts the membrane from the predetermined location to the fibrous web applies and presses this against the lower tool half. It is alternatively also possible that the membrane is attached to the lower mold half and bulges in the direction of the upper mold half. In this case, the lower mold half is the first mold half. Then, the fibrous tissue may be placed on the membrane, for example, and pressed against the upper mold half at the predetermined location by the leading part of the membrane. In contrast to the pressing of the fiber fabric to the lower mold half, however, the fiber fabric can already rest on the membrane when the fiber fabric is pressed against the upper mold half. Although then presses the membrane, the fiber fabric from the predetermined point, starting from the upper mold half, but then it no longer has to invest in the fiber fabric, since this already rests on her. Generally it is also possible to provide the membrane on the lower mold half.

By first pressing the membrane at the predetermined location on the lower or second mold half, it is possible to first locally fix the fiber mat and thus counteract a later distortion. Preferably, the predetermined location is in the middle of the molded body or in the middle of the lower mold half. In addition, the protrusion of the membrane can already be started during or after closing the tool. However, it is desirable if a complete application of the membrane to the fiber fabric or complete pressing of the fiber fabric to the lower and second mold half takes place only after closing the tool.

It is advantageous if the tool has a Harzinbringvorrichtung applying resin at the predetermined location on the fiber fabric.

By introducing resin at the predetermined location, it is ensured that the membrane presses the fiber mat against the lower tool half at the point where the resin was applied to the fiber mat. As a result of the subsequent application of the membrane to the fiber fabric or pressing of the fiber fabric onto the lower or second mold half, starting from the predetermined point, the resin is displaced away from the predetermined location. This ensures that not all the resin has to flow longitudinally through the fiber mat, but that a portion of the resin can flow along the fiber mat. Thus, a better distribution and faster impregnation of the fiber mat can be done, whereby the cycle times are shortened.

The membrane itself may be made of a non-adhesive material. It is also conceivable to use a self-releasing resin or spraying the membrane with a release agent. Alternatively, however, it is also possible in principle to arrange a film with separating properties between the membrane and the fiber fabric, for example a polyethylene film. This allows demoulding of the molding without damaging the membrane. Accordingly, the above-described membrane unfolded by the membrane unfolding means does not need to come into direct contact with the fiber web. The pressing of the fiber fabric or application of the membrane to the fiber fabric can thus be effected directly by direct contact or indirectly via, for example, a release film.

The application of resin to the fiber fabric can be done before closing the tool and / or after closing the tool. Prior to closing the tool, the resin can be applied from above onto the fiber fabric located on the lower mold half. In this case, the "application" of resin to the fiber web is to be understood literally, i. H. that the resin is applied to the surface of the fiber fabric. Alternatively, however, impregnation of the fibrous web from one side may occur so that localized accumulation of resin on the surface of the fibrous web occurs on the opposite side thereof. The "application" of resin is thus not only in the sense of applying resin directly to a surface to understand, but should also include applying resin by penetration of the fiber fabric, provided that there is also an accumulation of resin on the surface of the fiber fabric.

For applying resin to the fiber fabric, the resin introduction device may advantageously comprise a channel provided in the second, for example, lower mold half and opening at the predetermined location into a space between the membrane and the lower mold half. This ensures that the resin is applied to the fiber mat at the predetermined location and thus forms a local accumulation of resin at the location where the membrane first contacts the fiber web or resin upon deployment.

In a further advantageous embodiment, the membrane unfolding means has a fluid passage provided in the upper mold half, which opens into a gap between the membrane and the upper mold half. This makes it possible to effect the unfolding of the membrane by the supply of a fluid or by a pressurization or flooding of the space between the membrane and the upper mold half. The fluid used may be a liquid, such as water, or a gas, such as air. In this case, the membrane may also be constructed so that it consists of a plurality of chambers which are flooded separately at different speeds to partially control the resin distribution.

The membrane deployment means may comprise a plunger movably mounted on the upper die half and operatively connected at one end thereof to the membrane. The membrane can thus be deployed by moving the plunger by pressing one end either directly or indirectly against the membrane. "Actively connected" is therefore to be understood that the one end of the plunger is in direct contact with the membrane or arranged between the plunger end and the membrane another element is, which can transmit the movement performed by the plunger with or without translation to the membrane. In the case of direct contact of the plunger with the membrane can be achieved, for example, that the membrane is partially rigid or inflexible and acts at this point as a rigid tool upper half.

The membrane deployment means may comprise at least one deployment membrane disposed between the membrane and the upper mold half. This deployment membrane can be designed, for example, in the form of a bladder or a balloon. In this case, the deployment membrane can be arranged so that it is on the one hand in contact with the upper mold half and on the other hand in contact with the membrane. However, the deployment membrane may also be provided between the plunger and the membrane. It is also possible to provide a plurality of membranes next to each other or into each other and to drive them sequentially, for example. By means of such membrane unfolding means described above, a more targeted unfolding of the membrane can take place. This also allows more specific moldings to be realized.

In a particularly advantageous embodiment of the invention, the membrane unfolding means further comprises a control device for controlling and controlling the unfolding of the membrane. This opens up the possibility, for example, of influencing the type or the speed of membrane development.

In order to regulate the unfolding of the membrane, at least one sensor for detecting a state variable can be provided in the tool and the control device can be adapted to control the unfolding of the membrane as a function of the detected state variable. The sensor may be, for example, a pressure sensor. This may be provided at the edge of the fiber fabric and may be designed such that it outputs a signal to the control unit upon detection of a predetermined pressure value in order to stop unfolding of the membrane.

In the context of controlling or regulating the deployment of the membrane, it is particularly advantageous to use a largely incompressible fluid to deploy the membrane. This causes a much better response and therefore leads to a more direct and thus more precise control of the manufacturing process.

It is also desirable if the membrane is at least partially preformed according to the contour of the second mold half. Such preforming of the membrane according to the contour of the second mold half makes it possible to define specific, defined contact points. This ensures a more targeted distribution of the resin on or in the fiber fabric and, for example, also allows the introduction of resin at a plurality of predetermined locations.

According to the invention, a method is also provided for producing a molded part from fiber composite materials in accordance with the mode of operation and the structure of the device described above.

Thus, in the first method, an upper mold half and a lower mold half are provided, wherein on the upper mold half a membrane is mounted, which is vorwölbbar towards the lower mold half. Subsequently, a fibrous tissue is placed on the provided lower half of the mold. Thereafter, the tool is closed by moving the upper mold half to the lower mold half. The method is characterized in that the membrane-folding member is actuated during and / or after closure of the tool to deploy the membrane so that it bulges toward the second tool half such that a protruding portion of the membrane promotes fibrous tissue presses a predetermined point against the lower mold half and then the membrane from the predetermined location, starting from the fiber fabric and this presses against the lower mold half. After curing of the resin, the unfolding of the membrane is reversed and the tool is opened. Subsequently, the finished molding can be removed.

Desirably, prior to contact of the leading portion of the membrane with the fibrous web, resin is applied to the fibrous web at the predetermined location by a resin applicator.

The resin may be applied at the predetermined location prior to closing the tool, closing the tool, or closing the tool.

In the method, the unfolding of the membrane is advantageously controlled on the basis of a predetermined parameter which, for example, corresponds to a contour of the second tool half.

The unfolding of the membrane can be done in this case, for example, in response to a predetermined characteristic, which maps the contour of the second mold half. In this way, it is possible to set the contact speed with which the membrane applies to the fiber fabric in relation to the contour of the lower mold half.

Unfolding control may be accomplished by controlling the supply of hydraulic fluid into the space between the diaphragm and the upper mold half, such as by driving a pump. The contact speed of the membrane to the fiber fabric can thus be set so that it is reduced at problematic sites to ensure adequate impregnation of the fiber fabric. Also conceivable is a gradual reduction in the rate of deployment as the amount of resin displacement decreases, or when the resin must overcome large slopes. However, it is also possible to additionally and / or independently control the actuation of other elements of the membrane deployment means, such as one or more plungers or deployment membranes described above, by the fluid delivery.

It is also possible for the method to determine at least one state variable in the tool and to control the unfolding of the membrane as a function of the at least one state variable. For example, can be done using a pressure sensor, a regulation of the deployment rate of the membrane. It is also possible to stop the unfolding of the membrane upon reaching a predetermined pressure.

The invention will be explained in more detail by means of embodiments with reference to figures.

The 1A to 1C show the structure and operation of a first embodiment of the tool according to the invention schematically in cross section.

2 shows a second embodiment of the present invention schematically in cross section.

3 shows a third embodiment of the present invention schematically in cross section.

4 shows a fourth embodiment of the present invention schematically in cross section.

The 1A shows a tool in the closed position. The tool has an upper mold half 1 and a lower tool half 2 , In the closed state of the tool are the upper mold half 1 and the lower half of the mold 2 at least partially to each other. At the upper half of the mold 1 is a membrane 3 attached. This membrane 3 limited together with the upper mold half 1 a gap 13 , in the one in the upper half of the mold 1 provided fluid passage 12 empties. In the present case, the membrane 3 elastic and made for example of rubber. Furthermore, the membrane 3 sealing on the upper mold half 1 attached so that the gap 13 between the membrane and the upper mold half is fluid-tight. Now occurs a fluid supply through the fluid passage 12 , it is due to the elastic properties of the membrane 3 possible for these to be in the direction of the lower tool half 2 bulges.

In the present embodiment, the lower mold half 2 a recess into which a fibrous tissue 4 is inserted. The tool is designed so that the edge of the fiber fabric 4 with the tool closed between the membrane 3 and the lower half of the mold 2 is trapped. In principle, however, it is also possible to have a positive mold for the lower mold half 2 to choose. Then only the upper half of the mold must be 1 and the membrane 3 be worked as a negative accordingly.

Furthermore, located in the lower half of the mold 2 a resin introduction device 8th in the form of a channel 10 , This channel 10 flows into a room 11 between the upper membrane 3 and the lower half of the mold 2 , Through a mixing and metering device, resin can enter the room 11 be introduced. In the present case takes place in the resin feed through the channel 10 a penetration of the fiber tissue 4 such that is on the fiber fabric 4 a resin accumulation at a predetermined location 7 forms. In order to ensure that the fiber fabric rests against the lower mold half during the introduction of the resin, it is conceivable, following the insertion of the fiber fabric 4 in the lower half of the mold 2 the fibrous tissue 4 first briefly with a punch against the lower mold half 2 to press to cause the fiber fabric to abut the resin application site. However, it is also conceivable not to close the tool completely, so that between the lower mold half 2 and the upper half of the mold 1 a small gap remains and the fiber web 4 not yet between the membrane 3 and the lower half of the mold 2 is trapped. Then the membrane can 3 by a fluid supply through the fluid passage 12 be unfolded provisionally and so the fibrous tissue 4 at the resin application point to the lower mold half 2 be pressed. This step can also serve to preform non-preformed fiber web in the tool before the resin introduction begins. Then then the fluid can be at least partially drained again and the tool can be completely closed. It is also possible, an already preformed fiber fabric 4 in the lower half of the mold 2 use. To the penetration of the fiber fabric 4 to supported, this can also be in the area of the predetermined place 7 be perforated. Alternatively, it is also possible to apply the resin with the tool open at the predetermined location. Then the channel 10 not required and can be omitted.

The production of a shaped body made of fiber composite materials is described in more detail below.

As already with reference to 1A described, is first with the tool open the fiber fabric 4 in the recess of the lower mold half 2 inserted. Subsequently, the tool is by moving the upper mold half 1 on the lower half of the mold 2 closed. Below is the gap 13 between the membrane 3 and the upper half of the mold 1 through the fluid passage 12 supplied a fluid. The gap 13 is thus pressurized. This will start the membrane 3 towards the lower half of the mold 2 bulge. During the protrusion, in the present case, a resin is used simultaneously 9 through the channel 10 in the room 11 between the membrane 3 and the lower half of the mold 2 fed.

As it is in 1B is shown, the bulging of the membrane takes place 3 such that the anticipatory part 6 the membrane 3 first at the point with the fibrous tissue 4 comes into contact, at which the resin 9 was fed. Through the membrane is thereby the resin 9 also outside the fiber tissue 4 displaced towards the fiber tissue margin. In the present embodiment, the resin supply through the channel 10 stopped at the time when the anticipatory part 6 the membrane in contact with the fibrous tissue 4 arrives or this against the lower mold half 2 suppressed. However, it is also possible to unfold the membrane 3 temporarily stop when the anticipatory part 6 the membrane 3 in contact with the fibrous tissue 4 passes, and the supply of the resin 9 through the channel 10 continue for a predetermined time.

After pressing the fiber fabric 4 through the anticipatory part 6 the membrane 3 now becomes the gap 13 further pressurized, so that the membrane 3 unfolded further. Like this in 1C is shown, the membrane settles 3 starting from the first point of contact between the membrane 3 and the fibrous tissue 4 flat to the fibrous tissue 4 to displace the resin further to the outside. By the flat application of the membrane 3 to the fiber tissue 4 at the same time impregnation of the fiber fabric takes place 4 with resin. The gap 13 is now pressurized until the membrane 3 has fully unfolded and completely attached to the fibrous tissue 4 is applied. After a subsequent waiting time or hardening of the resin, the tool can then be opened and the finished part removed.

2 shows another embodiment of the present invention. The structure of the tool according to 2 differs only by the structure of the tool according to the 1A to 1C that on the upper tool half 1 in addition a pestle 14 movably mounted. This pestle 14 is at one end with the membrane 3 in contact and serves to the membrane 3 in the area of the mouth of the canal 10 to press on the lower mold half and thereby secure fixation of the fiber fabric 4 to effect. After fixation of the fiber tissue 4 through the pestle 14 can then the gap 13 between the membrane and the upper mold half 1 be pressurized with a fluid, so that the membrane 3 starting from the stamp on the lower mold half 2 invests. The pestle or stamp 14 here has a slightly rounded surface, with the membrane 3 is in contact. Instead, the contact surface of the plunger 14 with the membrane 3 also be flat.

3 shows yet another embodiment of the invention. The structure of the tool according to 3 differs from the structure of the tool according to 2 that instead of the plunger 14 or stamp a deployment membrane 15 is provided in the form of a bubble or a balloon. This unfolding membrane 15 has a similar effect as the pestle 14 , However, on a complicated mechanism for operating the plunger 14 be waived.

Furthermore, the structure according to 3 a control device 16 and one in the lower half of the mold 2 arranged sensor 17 , The controller is also still with a hydraulic system 18 connected to the fluid passage 12 and with a passage 19 for filling the deployment membrane is in communication. The sensor 17 is in the present case a pressure sensor 17 , By this arrangement, it is possible to unfold the membrane in response to the pressure sensor 17 to determine determined pressure and to stop when reaching a predetermined pressure.

4 shows a further embodiment of the invention. This embodiment differs from that in the 1A to 1C shown embodiments only in that the space 13 between the membrane 3 and the upper half of the mold 1 is formed with two chambers. In each of these chambers opens a channel 12 for supplying fluid. With this arrangement, it is possible to partially control the unfolding of the membrane and thus the resin distribution.

The above embodiments are by no means to be considered as limiting. Rather, the embodiments represent only an exemplary concretization of the invention, as defined in the introductory part of the description or within the scope of the appended claims. In particular, every possible combination of the individual features described, if reasonably possible, should be encompassed by the invention.

LIST OF REFERENCE NUMBERS

1

Upper tool half

2

Lower tool half

3

membrane

4

fiber fabric

5

Membrane deployment means

6

Advancing part of the membrane

7

Predetermined position

8th

Harzeinbringvorrichtung

9

resin

10

channel

11

Space between the diaphragm and the lower mold half

12

Fluid passage

13

Gap between the diaphragm and the upper mold half

14

tappet

15

development of membrane

16

control unit

17

sensor

18

hydraulic

19

passage

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

• DE 102009017512 A1 [0004]

Claims (15)

Tool for producing molded articles from fiber composite materials with an upper mold half ( 1 ) and a lower mold half ( 2 ), one on the upper half of the mold ( 1 ) attached membrane ( 3 ), which are in the direction of the lower half of the mold ( 2 ) is projectable, wherein between the membrane ( 3 ) and the lower mold half ( 2 ) a fibrous tissue ( 4 ), a membrane unfolding agent ( 5 ) for protruding the membrane ( 3 ); characterized in that the membrane ( 3 ) and the membrane unfolding agent ( 5 ) are adapted and configured such that a part projecting during protrusion (FIG. 6 ) of the membrane ( 3 ) the fibrous tissue ( 4 ) at a predetermined location ( 7 ) against the lower mold half ( 2 ) and the membrane ( 3 ) subsequently from the predetermined location ( 7 ) starting from the fiber tissue ( 4 ) and this against the lower mold half ( 2 ) presses. Tool according to claim 1, characterized by a resin introduction device ( 8th ) located at the predetermined location ( 7 ) a resin ( 9 ) on the fibrous tissue ( 4 ) can muster. Tool according to claim 2, characterized in that the resin introduction device ( 8th ) a channel ( 10 ) located at the predetermined location ( 7 ) in a room ( 11 ) between the membrane ( 3 ) and the lower mold half ( 2 ) opens. Tool according to one of claims 1 to 3, characterized in that the membrane unfolding means ( 5 ) one in the upper mold half ( 1 ) provided fluid passage ( 12 ), which is in a space ( 13 ) between the membrane ( 3 ) and the upper half of the mold ( 1 ) opens. Tool according to one of claims 1 to 4, characterized in that the membrane unfolding means ( 5 ) one on the upper mold half ( 1 ) movably arranged plungers ( 14 ), which at its one end with the membrane ( 3 ) is operatively connected. Tool according to claim 1, characterized in that the membrane unfolding means ( 5 ) at least one unfolding membrane ( 15 ), which between the membrane ( 3 ) and the upper half of the mold ( 1 ) is arranged. Tool according to one of claims 1 to 6, characterized in that the membrane unfolding means ( 5 ) a control device ( 16 ) for controlling and regulating the unfolding of the membrane ( 3 ) having. Tool according to claim 7, characterized in that in the tool at least one sensor ( 17 ) is provided for detecting a state variable and that the control device is adapted to the unfolding of the membrane ( 3 ) depending on the detected state variable Tool according to one of claims 1 to 8, characterized in that the membrane ( 3 ) at least partially corresponding to the contour of the second mold half ( 2 ) is preformed. A method of producing a molded part from fiber composites, the method comprising the steps of: providing an upper mold half ( 1 ) and a lower mold half ( 2 ), whereby on the upper mold half ( 1 ) a membrane ( 3 ), which are in the direction of the lower mold half ( 2 ) is bulging; Placing a fiber fabric ( 4 ) on the lower half of the mold ( 2 ) of the tool; Close the tool by moving the upper half of the tool ( 1 ) on the lower mold half ( 2 ); Actuating a membrane unfolding means ( 5 ) during and / or after the closing of the tool, around the membrane ( 3 ) so that they move in the direction of the second tool half ( 2 ) bulges in such a way that a protruding part during protrusion (FIG. 6 ) of the membrane ( 3 ) the fibrous tissue ( 4 ) at a predetermined location ( 7 ) against the lower mold half ( 2 ) and the membrane ( 3 ) subsequently from the predetermined location ( 7 ) starting from the fiber tissue ( 4 ) and this against the lower mold half ( 2 ) presses. A method according to claim 10, characterized in that before contact of the leading part ( 6 ) of the membrane ( 3 ) with the fiber tissue ( 4 ) by a resin introduction device ( 8th ) Resin ( 9 ) at the predetermined location ( 7 ) on the fibrous tissue ( 4 ) is applied. Process according to claim 11, characterized in that the resin ( 9 ) before closing the tool at the predetermined location ( 7 ) is applied. Method according to one of claims 9 to 12, characterized in that the unfolding of the membrane ( 3 ) is controlled by a given parameter. A method according to claim 13, characterized in that the predetermined parameter of a contour of the second mold half ( 2 ) corresponds. Method according to one of claims 9 to 12, characterized in that in the tool at least one state variable is determined and the unfolding of the membrane ( 3 ) is regulated as a function of the at least one state variable.

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