WO2015032982A2

WO2015032982A2 - Draping device for producing a three-dimensional preform of fibrous material

Info

Publication number: WO2015032982A2
Application number: PCT/EP2014/069199
Authority: WO
Inventors: Steffen Maertiens; Tobias Fuerst; Matthias Graf
Original assignee: Dieffenbacher GmbH Maschinen- und Anlagenbau
Priority date: 2013-09-09
Filing date: 2014-09-09
Publication date: 2015-03-12
Also published as: EP3043984A2; AT15268U1; WO2015032982A3; DE102013109854A1

Abstract

The invention relates to a draping device (13) for producing a three-dimensional preform (5) of fibrous material, comprising a female mould (14) reproducing the three-dimensional shape of the preform (5), and one or more mould cores (15) for draping and/or fixing, which are designed to cooperate with the female mould (14). The invention substantially consists in that different mould cores (15) on their surface (16) facing the preform (5), and/or different portions of this surface (16) of at least one mould core (15), have different surface roughnesses and/or roughness values; and or the surface (17) of the female mould (14) facing the preform (5) has portions with a different surface roughness and/or different roughness values.

Description

DRAPING DEVICE FOR MANUFACTURING A THREE-DIMENSIONAL FIBER MATERIAL PREPARATION

The invention relates to a draping device for producing a three-dimensional preform made of fiber material according to the type defined in greater detail in the preamble of claim 1. Furthermore, the invention relates to the use of such a draping device.

In the production of fiber composite components, which are also referred to as fiber-reinforced plastic parts, a common method for industrial use, for example, the so-called RTM method (Resin Transfer Molding) is known. The applied manufacturing process, which ultimately leads to the usable plastic component, consists of several individual processes. First, near-net shape preforms or semi-finished fiber products are produced. These components, which are also referred to as a preform, are typically stacked and / or joined in a so-called preforming process from a plurality of individual layers of woven or fibrous layers, usually in two-dimensional form, for example by stapling, gluing or by methods known from textile technology are, for example, sewing or the like. The resulting stack of individual fabric layers or fiber layers essentially already has the necessary outer contour and typically also any special features with regard to the layer thickness, special fiber progressions and the like. In general, after the stack has been made from the fabric layers, a binder is applied to the fabric layers or is already present between the fibers, for example by impregnating the individual fiber bundles with such a binder before they are further processed into the fabric or fiber layer.

Subsequently, in a draping device which images the desired three-dimensional shape of the preform in a die, the stack of fabric layers is preformed, typically by placing one or more draping and / or fixing punches, which are adapted to cooperate with the die, into the die stack Press to achieve the desired three-dimensional shape. The binder can then be activated, for example by heating and subsequent cooling of the die, so that an at least for the further manufacturing process manageable near net shape configuration of the three-dimensional preform is possible. Draping devices are basically known, for example, from DE 10 2010 027 466 A1 or from DE 10 2010 043 666 A1.

Decisive for the quality of the three-dimensional preform is that the individual layers of the stack come to lie in the die as possible without creases, unwanted draw, undesired stresses or the like, so as to obtain a three-dimensional preform that is as high-quality as possible and homogeneous with respect to the stack.

In the cited documents, therefore, the draping device is, for example, rotated so that the draping and / or fixing punches press the fabric stack into the die from below in order to achieve a lateral tension of the fiber material by means of gravity, so that wrinkles and creases can be easily avoided , However, this is associated with great expense, since on the one hand mold and structure must be rotated accordingly, so that the stamp can be actively raised. In the other cited document positioning pins are provided, which provide a similar effect without the die must be laboriously turned into an overhead position. However, while the die is extremely complex to manufacture, since the pins in their extended position must form an exact level as possible and because all the pins must go back into the die. The die is thus a very complex component, so that the resulting expense is worthwhile only for very large series and adversely allows no flexibility in the die. In addition, this very complex die is extremely susceptible to disturbances during the production process for the preform.

After the production of the three-dimensional preform this is inserted as near-net shape preformed intermediate product in a press for performing the RTM process. Depending on requirements, the three-dimensional preform can still be recut before, punched out at predetermined locations or provided with inserts or the like in order to achieve the most precise contour and functionality of the later fiber-reinforced plastic component. After inserting the three-dimensional preform into the tool, the tool halves are then closed in a manner known per se and the necessary resin is injected into the cavity of the tool in order to impregnate the fiber structure of the three-dimensional preform and to enclose the fibers. After curing of the resin matrix so the finished fiber-reinforced plastic component, which can be removed from the tool.

Since an important step in the production of such fiber-reinforced plastic components is already in the production of the three-dimensional preform, the draping device used has a decisive share in the quality of the later component. The above-described draping devices according to the prior art have the mentioned disadvantages.

The object of the present invention is now to provide an improved draping device, which avoids these disadvantages in particular. According to the invention this object is achieved by a draping device with the features in the characterizing part of claim 1. Further advantageous embodiments of the draping device according to the invention and its use will become apparent from the dependent claims.

In the case of the draping device according to the invention, the draping and / or fixing die or draperies have different surface roughness and / or friction values on their surface facing the preform and / or different regions of this surface of at least one draping and / or fixing die. Additionally or alternatively, the die may also have areas with different surface roughness and / or different coefficients of friction on their surface facing the preform. In the case of the draping device according to the invention, it is thus provided that either different punches with different surface roughness or friction coefficients are formed, or the one and the same punches, in particular if the stamper has a correspondingly complex shaping of its surface facing the preform, has different surface roughness or friction values. Alternatively or preferably in addition to this, the matrix can also be designed in different regions such that it has different surface roughness or friction coefficients. The surface roughness can be detected by metrology, for example by roughness depth, in particular in the form of an average roughness depth, and produced correspondingly in terms of manufacturing technology with regard to the desired values.

By means of such a variation of the surface roughness and / or friction values, it is possible to achieve different slip properties of the fiber material, that is to say the stack of fabric layers, which is optionally provided with a suitable binder. By the arranged in the center of the die stamp, parts of stamps or die surface have a correspondingly smooth surface or coated with a friction reducing material such as polytetrafluoroethylene, in this area a very good sliding of the fibers is achieved at the respective stamp, so that the then typically trained as Drapierstempel stamp the fibers with little friction can easily press into the counter-mold of the die. Other punches or other areas of the punch or die may accordingly be provided with a surface having high surface roughness and / or higher coefficients of friction for the fibrous material, for example a deliberately roughened surface having, for example, a mechanical corrugation or the like, or a corresponding coating for example, with polyurethane, which causes a much higher coefficient of friction for the fiber material than the already mentioned polytetrafluoroethylene.

By placing these punches or areas of punches or the surface of the die preferably in the outer region of the die, it is possible to ensure that the material of the preform is retained here more strongly than by the punches or surfaces with correspondingly smoother or with less friction Surface. The material can then be drawn from the areas in which the stamps are used with the larger surface roughness or the higher coefficients of friction, through the other stamp in the die. As a result, a very clean system is achieved without wrinkling or the like occurs. The structure is much simpler than the structure described in the prior art, for example, the construction with the positioning pins, since only a corresponding surface treatment of the draping and / or fixing punches and / or optionally the surface of the die is necessary to the desired Effect to achieve.

The various properties of the surface with respect to surface roughness and / or coefficient of friction can be achieved very easily by a different processing of the individual surfaces or partial parts of the surface.

In a very favorable development of the draping device according to the invention, it is further provided that at least one of the draping and / or fixing punches is at least partially provided on its surface facing the preform with a resiliently deformable layer or is formed of resiliently deformable material. Such a resiliently deformable layer may for example be an elastomer layer or the like, which covers the surface of the Drapierstempels or which is particularly accurately inserted into a cutout so that it forms a flat surface with the remaining areas of the surface of the Drapierstempels in the deformed state. When draping, then, after an investment of the Drapierstempels has been achieved on the stack of tissues, another feed movement taking advantage of the elasticity of the resiliently deformable material. This allows a further movement of the stack out of the fabric layers, for example, to stretch the material and / or smooth individual wrinkles.

According to an advantageous development of the draping device according to the invention, it is provided that at least one of the draping and / or fixing punches and / or the die is at least partially coated on the surface facing the preform. By such an at least partial coating, the surface properties can be easily changed, for example, by the surface is uniformly machined and then partially coated in a targeted area. The coating may, for example, take place such that the friction and / or the surface roughness is reduced, or, conversely, selective coating may take place in such a way that the friction or the surface roughness is increased, for example by applying a partial polyurethane layer.

In a further very favorable embodiment of the draping device according to the invention, it is now further provided that the surfaces of the at least one draping and / or fixing die facing the preform have different coatings. Different areas of the surface of a single stamp can thus be easily adapted to the different required properties, for example by removing parts of the surface with a friction-reducing coating, for example based on PTFE, and other parts of the surface with a friction-increasing coating, For example, based on polyurethane, are formed. In between, in principle uncoated areas of the surface may remain, which then lie in their properties between the properties of the two coated areas.

In order to minimize the effort with regard to the production of the individual draping and / or fixing punches, however, it can also be provided in a particularly advantageous development of the draping device according to the invention that the surface of each draping and / or fixing punch facing the preform is uniformly m substantially constant surface roughness and / or coefficient of friction is formed, wherein a plurality of draping and / or fixing punches are provided with different surfaces. This structure, in which each of the punches is formed with a uniform surface in itself, is particularly easy to produce the punches, because without masking and the like, the surface can be uniformly processed and / or coated. The fact that now several punches are used in the draping device, the desired property can still be achieved, for example, by the more outer punch have a rougher surface or have higher coefficients of friction than, for example, the centrally arranged stamp. As a result, the fiber material of the later preform is retained accordingly in the edge region of the die and must be drawn and pressed against the larger frictional force in the region of the outer die of the Drapierstempeln inside, which have a corresponding surface with low friction in the die. This results in a very clean preform, without the significant risk of wrinkling or the like.

In a particularly advantageous embodiment of the draping device according to the invention, it is now also provided that at least one of the draping and / or fixing has a direction of movement to the corresponding surface of the die, which from the vertical on the corresponding surface of the die or a deviates from this mediating plane. Such a construction in which at least one of the draping and / or fixing punches is thus moved obliquely, preferably at an angle of more than 5 ° with respect to the vertical to the die, can optimally tension the individual fibers in the stack of fabric layers. The oblique movement, in particular in combination with a resiliently deformable surface of the punch, generates when moving the punch a transverse movement of the fibers or fabric layers on the surface of the die, whereby wrinkles are smoothed and, optionally, alternatively or additionally, a reorientation of the fibers is achieved. This is especially true in combination with the already mentioned elastically deformable material, since then in particular by the residual stroke, which is achieved by utilizing the elasticity, such a transverse movement can be achieved with otherwise already fixed fiber material of the stack of fabric layers.

Further advantageous embodiments of the draping device according to the invention will become apparent from the remaining dependent subclaims and will be apparent from the embodiment, which will be described below with reference to the figures.

Showing:
1 is a schematic representation of an industrial plant for the production of fiber-reinforced molded parts with a previous production of three-dimensional preforms.
Fig. 2 is a schematic representation of a detail of a draping device according to the invention; and
Fig. 3 is a schematic representation of a section of a draping device in an alternative embodiment according to the invention.

In the illustration of Figure 1 is very highly schematic an industrial plant 1 can be seen, which ultimately serves to produce a fiber-reinforced molding 2 by means of a RTM process in a tool 3 in a press 4. In this case, the fiber-reinforced molded part 2 is produced from a preform 5, which is preformed in a three-dimensionally close-to-net shape and which has previously been produced in some schematically illustrated steps. The starting base for the preform 5 is a fiber material, for example in the form of a fabric layer, a fiber fabric or the like. This can be made available, for example, as a roll product via an indicated roller 6.

In a cutting device 7, a single fabric layer or mat, which is not explicitly shown here, is then cut from the roll goods by means of a cutting device 8. Subsequently, this fabric layer is fed via a suitable transport device, which is indicated in principle in the illustration of Figure 1 only by curved arrows, an indicated device 9, in which binder is applied to the fabric layer. This can be done for example by spraying, rolling, dipping or the like. Alternatively to this procedure with the device 9 for applying binder, it would also be possible to preimpregnate the fiber material with a corresponding binder, so that this step can be omitted. However, this is familiar to the person skilled in the art from the general state of the art, so that it need not be discussed further here.

After the order of the binder, or if this step is omitted and the binder is already present in the fiber material, then immediately the fabric layer passes to a stacking device 10, in which the individual fabric layers are stacked to form a stack of fabric layers 11 indicated here. It can also be a stapling, sewing or otherwise connecting the individual layers of fabric at locations where this is useful and necessary for design reasons, can be provided. The fabric layers typically have a near-net shape after cutting in the cutter 7. Nevertheless, even after the stacking of the fabric layers to the stack 11 in the stacking device 10 further trimming, punching out openings or the like can be made, if desired or required.

After the stack 11 has been prepared in this way, in the exemplary embodiment shown here it enters a heating device 12 in which, as indicated here, it is guided via a transport means through an oven, a line with infrared radiation or the like. The stack 11 is thus preheated and the typically thermally activatable binder is activated or liquefied so far that the stack 11 still has a high degree of flexibility, but the fabric layers processed in the stack 11 adhere to one another during cooling.

The core functionality in the production of the three-dimensionally preformed preform 5 now comes to the draping device 13 shown in the next step. The draping device 13 in this case has a die 14, which images the later form of the three-dimensionally preformed preform 5. Via stamp 15 for draping and / or fixing, the stack 11 of fabric layers is now pressed into the shape of this matrix 14 and typically cools by the metallic material of the matrix 14, which is highly thermally conductive and dissipates heat from the stack 11 of the fabric layers , As a result, the binder hardens and there is the three-dimensionally preformed preform 5, which is already formed in its shape near net shape and the shape of the die 14 and the punch 15 follows. In this case, the punches 15 can be used, which hold the fiber material, and / or in particular punches 15 are used as Drapierstempel, which serve for moving the fiber material, for example in the recesses of the die 14.

The preform 5 is as far as dimensionally stable by the cured binder, that this, without losing its shape, at least further transported and optionally stored. However, it has not yet reached its final shape and hardness, this will only be achieved in the subsequent RTM process. The thus preformed in the drapery 13 and ideally glued and hardened in her stack 11 then forms the preform 5, which, as already described above, the press 4 for the RTM process can be supplied.

Now it is so that in particular the Drapierstempeln 15 for pulling the stack 11 on fabric layers of particular importance, since a very uniform feeding or pressing the stack 11 must be made of fabric layers in the recesses of the die 14. Only in this way can wrinkles or unnecessary stresses in the material of the stack 11 be avoided. However, this is a fundamental prerequisite for a good quality of the molded part 2 produced in the RTM process and, associated therewith, a good quality in the fiber-reinforced molded parts 2 produced in this way.

In order to achieve a high-quality impressions or drawing in of the stack 11 on fabric layers, ie ultimately of the fiber material into the die 14 or its recesses, it is provided in the draping device 13 that the individual draping and / or fixing punches on their later preform. 5 or the stack 11 of fabric layers facing surfaces, which are each marked 16 in the illustration of Figure 2, have different surface roughness and / or friction values. In principle, each individual one of the punches 15 may have areas on its surface 16 with specifically different surface roughness or friction coefficients. Ideally, however, the surfaces 16 of the punches 15 are largely homogeneous in themselves, while different punches 15 have different surface roughness or friction values.

In particular, it makes sense if, referring to FIG. 2, the two smaller stamps 15 arranged outside have a higher surface roughness or higher coefficients of friction on their surfaces 16 so as to retain and tension the material of the stack 11 from woven layers. Accordingly, the surfaces with the larger surface roughness or the higher coefficients of friction are denoted by 16 *. The central punch 15 presses or pulls the material of the stack 11 into the recess of the die 14. The central punch 15 has a correspondingly good surface quality with very low surface roughness or a very low coefficient of friction, so that the material slides on it particularly well. Its surface is designated 16 ', it could for example be polished. Fundamentally as an alternative to, but in particular in addition to, the surface of the die 14, which is designated 17 in FIG. 2 and faces the material of the stack 11, can also have regions with different surface roughness and / or different coefficients of friction. This also makes it easier to retract the material of the stack 11 into the recesses, for example when edges and radii around which the material of the stack 11 must flow are polished accordingly and, for example, the surfaces 17 of the die 14 cooperating with the two outer punches 15 likewise are roughened to restrain and tension the material of the stack 11 as it passes through the central punch 15 in the recesses of the die 14.

The surface roughness or friction coefficients must be adapted accordingly to the fiber material used, for example the carbon fibers in a carbon fiber-reinforced molded part 2. To produce a correspondingly large surface roughness or a high coefficient of friction, for example, a processing can be carried out in such a way that the surface has microscopic or even macroscopic corrugations so as to achieve adherence of the fibers to the

surface

16, 17. The fiber material is thereby retained and can be tensioned by the central punch 15 accordingly. As a result, the risk of edges, wrinkles or wrinkles in the material of the stack 11 is significantly reduced. In the case of the described, in the representation of Figure 2 each outer punch 15, such a coating would have to produce a higher coefficient of friction with respect to the fibers of the fiber material than, for example, the surface of the central punch 15 or a coating applied thereto. Conceivable coatings would be in the region of the outer dies 15, for producing a higher coefficient of friction, for example coatings of polyurethane, which have a comparatively high coefficient of friction for the fibers. The central punch 15 could accordingly have a friction-reducing coating, for example based on polytetrafluoroethylene.

The use of

surfaces

16, 17 with different surface roughness and / or friction values thus allows a targeted "flow" of the material of the stack 11 between the surface 17 of the die 14 and the surface 16 of the respective punch 15, so very targeted by a suitable coating or Processing of the

surfaces

16, 17, the uniform and crease-free feeding of the fiber material into the recesses of the matrix 14 can take place.

This particularly good retraction of the material of the stack 11 between the surface 17 of the die 14 and the surfaces 16 of the respective punch 15 can now also be supported by the fact that the surface 16 is provided at least one punch 15 with a resiliently deformable layer or the entire stamp 15 is formed of resiliently deformable material. For example, a deformable elastomer can be inserted into a cutout in a punch 15 formed of metal or plastic, in particular such that in the deformed state a flat surface of the punch 15 is achieved between the area with the elastomer and the adjacent areas. For example, when using rubber or rubbery materials is then simultaneously achieved a surface 16 * with higher coefficient of friction. By means of the elastically deformable material, after the actual feed movement over a residual stroke of the punch 15, a further tensioning and, if appropriate, smoothing of the material of the stack 11 and, if appropriate, a pretensioning or reorienting of the fibers located therein can be achieved using the electricity.

In the representation of FIG. 3, an alternative embodiment of the draping device 13 can now be seen. The individual punches 15 no longer move all perpendicular to the respective, associated surface 17 of the die 14, but partially obliquely to a vertical S, on the corresponding surface 17 of the die 14 or, if this is uneven, a vertical S on one averaged level on this. In the specific exemplary embodiment in the illustration of FIG. 3, in particular the central punch 15, which has a correspondingly smooth surface 16 ', then moves in time in the direction of the die 14. Subsequently, the adjacent obliquely outwardly delivering punch 15, which in particular have rougher surfaces 16 * and thus cause a tensioning of the material of the stack 11 to the outside. Subsequently, the outer punch 15 can be delivered, which also have a surface 16 * with higher surface roughness in the embodiment shown here.

If, in particular, the two punches 15 adjacent to the central punch 15 are provided, in addition to their surface 16 *, with greater roughness or a higher coefficient of friction for the fiber material with a resiliently deformable material, for example as described above, then after the actual infeed via the through The elasticity achievable residual stroke achieved a transverse movement of the material of the stack 11 in the example of Figure 3 to the outside, so that wrinkles easily eliminated and, if necessary, a voltage or reorientation of the fibers can be achieved. If the surface 17 of the matrix 14 and the surface 16 'of the central punch 15 are designed to be correspondingly smooth, then the material can simply flow in, so as to ensure an ideal contact with the surface 17 of the matrix 14. The same applies then for the two externally arranged stamp 15 accordingly. By this structure, optionally with a staggered setting of the individual punches 15 successively, in particular from the inside to the outside, the draping device 13 can thus be further optimized.

The person skilled in the art already knows that the punches 15 have actuators 18 which are suitable for moving the punches in the direction of or away from the die 14. Depending on the orientation of the actuators 18 and the Drapiergeometrie thus results during draping also a corresponding component of movement of the stack 11 in or parallel to the surface of the die.

List of Reference P1464
1 industrial plant
2 molding
3 tool
4 press
5 preform
6 roll
7 cutting device
8 cutting device
9 device
10 stacking device
11 stacks
12 heating device
13 draping device
14 matrix
15 stamps
16 surface of 15
16 * surface (with higher coefficient of friction)
16 'surface (with lower coefficient of friction)
17 surface of 14
18 actuators
S vertical

Named patent literature:
DE 10 2010 027 466 A1
DE 10 2010 043 666 A1

Claims

Draping device for producing a three-dimensional preform (5) made of fibrous material

1.1 of a three-dimensional shape of the preform (5) imaging die (14),

1.2 one or more stamps (15) for draping and / or fixing, which are designed to cooperate with the die (14), characterized in that

1.3 different stamp (15) on its the preform (5) facing surface (16) and / or different areas of this surface (16) of at least one stamp (15) have different surface roughness and / or friction values; and or

1.4 the preform (5) facing surface (17) of the die (14) has areas with different surface roughness and / or friction.
Draping device according to claim 1, characterized in that at least one of the dies (15) on its side facing the preform (5) is facing surface (16) at least partially provided with an elastically deformable layer or formed of resiliently deformable material.
Draping device according to claim 1 or 2, characterized in that at least one of the punches (15) at its the preform (5) facing surface (16) or the preform (5) facing surface (17) of the die (14) at least partially coated is.
Draping device according to claim 1, 2 or 3, characterized in that the preform (5) facing surface (16) of the at least one punch (15) has different coatings.
Draping device according to claim 1, 2 or 3, characterized in that the preform (5) facing surface (16) of each stamp (15) is uniformly formed with a / s substantially constant surface roughness and / or coefficient of friction, wherein a plurality of punches ( 15) are provided with different surface roughness and / or friction on their surfaces (16).
Draping device according to claim 5, characterized in that in the outer region of the die (14) arranged punch (15) have a rougher surface or higher coefficients of friction than centrally arranged drapery and / or Fixierstempel.
Draping device according to one of claims 3 to 6, characterized in that coatings for surfaces (16, 17) with low coefficients of friction comprise polytetrafluoroethylene or polytetrafluoroethylene.
Draping device according to one of claims 3 to 7, characterized in that coatings for surfaces (16, 17) have a higher coefficient of friction polyurethane or polyurethane.
Draping device according to one of claims 1 to 8, characterized in that surfaces (16, 17) with greater surface roughness have a microscopic or macroscopic corrugation.
Draping device according to one of claims 1 to 9, characterized in that surfaces (16, 17), which have a low surface roughness, are made finely ground or polished.
Draping device according to one of claims 1 to 10, characterized in that at least one of the punches (15) has a direction of movement to the corresponding surface (17) of the die (14), which from the vertical (S) or on the with him corresponding surface (17) of the die (14) or a middle plane of the optionally uneven surface corresponding to it (17) of the die (14).
Draping device according to claim 11, characterized in that the deviation of the direction of movement from the vertical (S) is at least 5 °.
Use of the draping device (13) according to one of claims 1 to 12 for producing a three-dimensionally preformed preform (5) for further processing in an RTM process.