EP2871273B1 - Method for producing a fibre preform - Google Patents

Description

The invention relates to a method for producing a fiber preform for the production of a fiber composite component having a predetermined geometry and outer end contour, wherein the fiber preform is formed from a fiber material. The invention also relates to a manufacturing plant for this purpose.

Components made of a fiber composite material, so-called fiber composite components, have become indispensable in the aerospace industry today. But also in the automotive sector, the use of such materials is becoming more and more popular. In particular, critical structural elements are made of fiber reinforced plastics due to the high weight specific strength and stiffness with minimal weight. Due to the anisotropic properties of the fiber composite materials resulting from the fiber orientation, components can be adapted exactly to local loads and thus enable optimal material utilization in terms of lightweight construction.

In the manufacturing process, in addition to dry semi-finished fiber products such as scrim and fabric, so-called prepregs (semi-finished fiber products preimpregnated with a matrix material) are used. Due to the ever increasing quantities in the production of fiber-reinforced components, there are great efforts to automate the manufacturing process as far as possible without adversely affecting the quality of the manufacturing process or of the components to be produced. The fibrous materials can be dry, ligated, pre-fixed or preimpregnated fabrics, nonwovens, uniaxial or multiaxial Be materials.

Especially in mass production, the aspects of productivity and the conservation of resources must also be taken into account, as they are particularly important here due to the large number of units. So even today, so-called Multiaxialgelege, which are composed of two or more fiber layers, either manufactured with a constant width and basis weight per meter or individually using a Tapelegers or a robot laying device.

The production of multi-axial webs in the form of meter goods with a constant fabric width, for example, offers the advantage of high productivity, even if these have to be tailored to the corresponding fiber web molds. However, the material waste in this type of production of fiber fabrics is particularly large, so that it negatively in weight production, especially in mass production and thus has a significant effect on the component price.

From the DE 10 2010 044 721 A1 a method and an apparatus for producing a semi-finished fiber product is known in which the semifinished fiber product to be produced is broken down into a plurality of model strips and these model strips are then subsequently laid and produced by means of individual fiber strips. Again, there is the corresponding disadvantage that the productivity compared to the production of Multiaxialgelegen by meter goods is extremely low, since the individual parts of the complete model are manufactured one after the other.

From the WO 2009/156385 A2 a method for producing a multi-axial fiber fabric is known in which the individual rovings of the fiber layers in one Spreading process to be processed.

From the WO 2009/042225 A2 a device is known with which semifinished fiber products can be produced from fiber strips, wherein the individual fiber strips are cut during the laying of the fiber strips of a quasi endless band atoque.

From the EP 2 248 659 A1 discloses a method by which the webs of semi-finished fiber strips to be deposited can be calculated so as to generate as small gaps or gaps between the individual strips as possible. This is particularly relevant if the fiber strips are to be deposited on a curved tool surface.

From the WO 2012/104174 A1 there is known a process for producing fiber-reinforced preforms, wherein the preforms are composed of individual sub-elements which are cut by means of a cutting device. Subsequently, the individual cut partial elements are then assembled according to their outer end contour to the fiber preforms.

Against this background, it is an object of the present invention to provide an improved method and an improved apparatus for producing fiber preforms with which the waste can be reduced, so that the proportion of unused material can be kept as low as possible, especially in mass production.

The object is achieved by the method according to claim 1 and the system according to claim 10 according to the invention.

Accordingly, the invention proposes that initially a pattern by dividing the fiber preform geometry into a plurality of sub-elements which, when assembled, are to form the later fiber preform geometry with the predetermined outer end contour. Subsequently, the sub-elements are arranged to form a pattern with which the individual sub-elements are to be cut from a fiber material. The generation of the pattern is carried out in dependence on the outer contour of the individual sub-elements, which are to form the geometry of the later fiber preform. The determination of the geometry and arrangement of the individual sub-elements is carried out with the aid of running on a calculating machine optimization method, taking into account the outer contour of the individual sub-elements in order to minimize the waste between adjacent sub-elements of the pattern. The subdivision of the fiber preform geometry in the individual sub-elements and the generation of the pattern can be done using a microprocessor-controlled pattern determination unit.

The outer contour of the determined sub-elements corresponds to the outer end contour of the fiber preform.

Once the pattern has been produced, the fiber preform is produced from the individual partial elements by cutting the individual partial elements from the fibrous material according to the pattern by placing or depositing the partial elements before, during or after cutting to form the fiber preform. The fiber preform is thus formed with its predetermined geometry and outer end contour. A fiber preform is a semifinished fiber product formed from a fiber material which at least partially contains the later component form of the fiber composite component to be produced.

The optimization method in the sense of the present invention is the solution of an optimization problem such that a desired parameter of the task is minimized with the aid of an objective function.

The parameter to be minimized here is the blend, by which the excess material of adjacent sub-elements in the pattern is understood. The target function can be designed in such a way that it minimizes the parameter blending with the aid of an analytical or a numerical method.

For example, it is expedient and advantageous if the steps of subdividing the geometry and generating the pattern are performed multiple times, each time generating different geometries of the individual subelements in the subdivision of the fiber preform geometry. This is particularly advantageous if the application of the method is not restricted to a predefined material size, for example material width. The patterns produced at each pass are then compared with respect to their respective blends, so that, for example, that particular cutting pattern is used that has the least scrap. According to the invention, the cutting pattern of the sub-elements is further generated as a function of a predetermined fiber angle orientation, a permissible cutting angle of the fiber material and a minimum size of a sub-element. Advantageously, the cutting pattern is produced as a function of a number of layers of the fiber preform to be built up. These boundary conditions can have a significant influence on how the sub-elements are arranged within the pattern, for example, as a rule, the fiber preform must have a predetermined fiber angle orientation and thus the sub-elements can not be cut out arbitrarily from the fiber material. Rather, the sub-elements, depending on the position and arrangement within the fiber preform, must correspond to the predetermined fiber angle orientation. In addition, a permissible cutting angle of the fiber material and the number of layers to be built up of the fiber preform have a relevance with regard to the arrangement of the sub-elements in the cutting pattern with respect to the fiber material.

The fiber preform may, for example, be produced in such a way by initially depositing fiber material of a partial element at least partially. Before it is finally deposited, it is cut according to the pattern at its last cut edge. This is particularly advantageous when the sub-elements are deposited from a fiber endless material, so that the process step of cutting and depositing coincides. The sub-elements inevitably have to be stored next to each other, but in terms of their position within the fiber preform according to pattern.

It is also conceivable that at least a portion of the sub-elements are cut from the fiber material according to the pattern and then the cut sub-elements are stored for the production of the fiber preform. It is advantageous if the cut sub-elements are sorted prior to depositing with respect to their position within the fiber preform and stored sorted in a material storage. Since in the present inventive method now, as known from the prior art, the deposition order for the cutting of the sub-elements is relevant, but the order of the cut elements primarily result from the minimization of the waste, it is particularly advantageous the cut sub-elements are sorted prior to depositing with respect to their position within the fiber preform, so that during the deposition process by means of the fiber laying unit, the individual sub-elements can be successively removed from the material storage and stored. As a result, the productivity of the laying process can be increased despite the increased cost when cutting the partial elements.

In an advantageous embodiment, the fiber preform geometry is subdivided into a plurality of strip-shaped sub-elements having a predetermined strip width and the individual strip-shaped sub-elements as Fiber strips cut one after another from a Faserendlosmaterial. This is desirable, for example, when the laying process for the production of the fiber preform is based on the fact that individual fiber strips are to be laid from a continuous fiber material with a predetermined material width. The pattern is thereby produced by arranging the individual fiber strips one after the other on the fiber endless material, the sequence of the fiber strips on the fiber endless material being determined by means of the optimization method for waste optimization as a function of the outer contours of the fiber strips.

Thus, in this embodiment, the individual fiber strips are arranged with respect to their order so that, for example, identical or similar outer contours, which correspond to a cut edge in the cutting of the fiber strips of the continuous material, are arranged adjacent, whereby the waste is minimized when cutting the fiber strips. Thus, it is conceivable, for example, that the cutting edge between two adjacent fiber strips each form the contiguous outer contours of the fiber strips. In this case, the outer contours would be identical in terms of their cutting process. It is also conceivable, however, for the fiber strips on the continuous filament material to be arranged with respect to their sequence in such a way that those fiber strips are arranged adjacent whose outer contours are congruent within a predetermined tolerance range. This also minimizes waste.

Furthermore, the course of the cutting edge between subelements adjacent to each other in the cutting pattern can be optimized by means of the optimization method, for example by selecting cutting profiles which lead to a minimal scrap, even if the desired outer contour of the subelement is not realized by the cutting edge can be and this can lead to a final contour trimming. While this is at the expense of productivity, it does increase it at the same time significant savings in wastage.

Of course, it is also conceivable that all partial elements or at least one part have a cutting edge which corresponds to the outer contour of the fiber preform. In this way, targeted partial elements can be produced with a finished outer contour, which can increase productivity, as a subsequent contouring is eliminated.

It is conceivable and expedient that firstly all partial elements or at least a part thereof are cut according to the generated pattern and the cut partial elements are temporarily stored in a material storage prior to deposition, so that the entire deposition process can be carried out without the process step of cutting. In this case, it is particularly advantageous if the individual sub-elements are additionally stored temporarily in the material store before they are deposited.

However, it is also conceivable that in each case a sub-element is cut according to the generated pattern and the currently cut sub-element is subsequently deposited for the production of the fiber preform, before a further sub-element is cut. In this case, the step of caching can be saved, which increases the productivity and should advantageously be applied to a smaller number of sub-elements.

In a further advantageous embodiment, the number of sub-elements in the cutting pattern is minimized by means of the optimization method running on the calculating machine. By specifying the minimization of the number of sub-elements, the productivity can be significantly increased since, with fewer sub-elements, the process step of depositing the individual sub-elements is reduced / shortened. With the help of the optimization method can be so with the specifications of a minimum number of sub-elements and a minimum In terms of productivity, it is important to achieve a balance between the waste that needs to be reduced and the amount of waste that needs to be reduced. By appropriate specifications, such as increasing productivity or reducing waste, an optimum can be found here with respect to these specifications.

It is thus advantageously possible, with the aid of the optimization method, to determine an optimum with regard to minimum waste and maximum productivity. For example, it makes little sense if, due to a high number of sub-elements, the waste can be reduced by a few percent, but the productivity is almost halved due to the many sub-elements. By weighting the parameters cut reduction or productivity increase can be placed on one or the other, so as to obtain the best possible pattern for the given boundary conditions.

In an advantageous embodiment, the sub-elements consist of unidirectional, mutually parallel and just prepared continuous fibers. However, it is also conceivable that the sub-elements consist for example of fabric, fleece or multiaxial material. The sub-elements may consist of dry, prebent, pre-fixed or already preimpregnated fiber material. For special layer structures, however, certain sub-elements may also consist of other auxiliary materials, for example binder fleece, visible fabric or special foils. A sub-element advantageously always has two mutually parallel sides. The mutually parallel sides then advantageously run parallel along an existing fiber angle orientation. However, a partial element can also have any outer contour that corresponds to the outer contour of the fiber preform at the position of the partial element. The sub-elements advantageously have uniform widths. So it is advantageously only one or two give different widths of subelements. However, it is also conceivable that significantly more different widths are available or completely dispensed with uniform widths.

Figur 1 -

verschiedene Varianten der Verschnittoptimierung;

Figur 2a, 2b -

Varianten der Schnittwinkeloptimierung;

Figur 3 -

eine vorteilhafte Ausführungsform.

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

FIG. 1 -

different variants of waste optimization;

FIGS. 2a, 2b -

Variants of the Schnittwinkeloptimierung;

FIG. 3 -

an advantageous embodiment.

FIG. 1 shows in three variants A to C the respective material consumption. In this case, a fiber preform 100 is to be produced by means of fiber strips 110, 112, 114 and 116, wherein the respective fiber strips are to be cut out of a continuous fiber material and thus have a predetermined solid material width. The fiber preform 100 has a circular geometry and outer end contour.

In the first variant A, the fiber strips are successively cut off from a continuous filament ribbon of material by means of a substantially rectangular angle of intersection. As can be seen, this variant has the largest waste, since the difference to the outer end contour of the fiber preform 100 is greatest due to the rectangular geometry of the individual fiber strips.

According to the invention, in order to keep the waste as low as possible, the order of the arrangement and the cutting angle is optimized, so that the waste is minimized. In this case, the cutting angles are generated in such a way that the cutting edge resulting from the cutting angle corresponds in each case to two successive fiber strips.

So in variant B is the FIG. 1 shown that the fiber strips 110 and 116 on have at least one side an identical cutting angle, so that these fiber strips 110 and 116 can be arranged on the Faserstreifenendlosmaterial successively and have a common cutting edge. As a result, the material consumption compared to the first variant A can be reduced.

According to variant C of FIG. 1 has been chosen a different arrangement of the fiber strips, which now give common cut edges of the fiber strips 110 and 112 and the fiber strips 114 and 116 and beyond the fiber strips 112 and 116 may also have a common cutting edge. According to this arrangement, the material consumption and thus the waste can be reduced again compared to the variant B.

As in FIG. 1 As shown by optimizing the arrangement and thus optimizing the cutting angle, not only is the waste reduced but also the order of the fiber strips within the fiber preform changed. Thus, in variant B, the central fiber strips 112 and 114 are first arranged on the fiber strip endless material, whereupon the outer left fiber strip 110 and then the outer right fiber strip 116 follow. It can also be seen that the fiber strip 110 has no bevelled cutting angle on its lower side, so that it can be cut off with the cutting edge 114 previously arranged on the fiber strip endless material with a cut edge.

In variant C, the two inner fiber strips are arranged on the fiber strand endless material outside, while the two outer fiber strips are then arranged centrally thereof. As a result, an even greater agreement with the cutting angles can be achieved.

By means of the optimization method, the fiber strips can thus each be different be arranged on the Faserstreifenentlosmaterial, in which case a respective intersection angle between the two fiber strips is determined, which generates a minimum waste.

The generation of the cutting pattern with the aid of the optimization method can thus take place in two stages, on the one hand by an optimal arrangement of the individual fiber strips with respect to their required outer contour to form the outer end contour of the fiber preform 100, and on the other hand by the determination of an optimum cutting edge, so that in the sum of the waste is minimized.

The FIGS. 2a and 2b show two different variants, as two fiber strips can be arranged with their required outer contour, so that there is an optimal angle of intersection. FIG. 2a This is the safest and simplest variant, since the cutting angles of the two fiber strips 210 and 220 do not intersect within the material region. It is irrelevant whether at the cutting edge 212 or 222, the two fiber strips are separated from each other, since in both cases a final contour trimming is necessary and the waste remains the same.

In FIG. 2b For example, both cut angles would intersect within the material area because the two fiber strips 210 and 220 are placed directly adjacent one another. The cutting edge for cutting off the two fiber strips would then take place at the cutting edge 222, wherein the waste when cutting the outer contour for the fiber strip 210 with respect to the variant of FIG. 2a is lower.

FIG. 3 shows an embodiment in which the fiber preform is not generated from a plurality of fiber strips with the same fiber strip width, but by individually tuned sub-elements. The fiber preform 300 with its desired geometry and final contour is in subdivided a plurality of sub-elements 310, 312, 314, 316, 318 and 320, wherein these individual sub-elements are then arranged on a fiber material 330 correspondingly so that the waste is minimized. In this case, a cutting pattern is produced, which has optimally matched cutting contours in the base material in order to reduce the waste while at the same time increasing productivity, since fewer strips have to be deposited and thus less transport effort or less necessary movement of the robotics when depositing the fiber strips lead to a significant reduction in production time.

Claims (15)

1. Method for producing a fibre preform for the production of a fibre composite component with a predefined geometry and final outer contour, the fibre preform being formed from a fibre material, comprising the steps:

   a) producing a cutting pattern by subdividing the fibre preform geometry into a plurality of sub-elements which, put together, form the subsequent fibre preform geometry with the predefined final outer contour, and arranging the sub-elements in a cutting pattern in order to cut the individual sub-elements out of a fibre material on the basis of the outer contours of the individual sub-elements, the trim between adjacent sub-elements of the cutting pattern being minimized by means of an optimization method running on a computer, and

   b) producing the fibre preform from the individual sub-elements by cutting the individual sub-elements in accordance with the cutting pattern produced,

   characterized in that the cutting pattern of the sub-elements is further produced on the basis of a predefined fibre angle orientation, a permissible cutting angle of the fibre material and a minimum size of a sub-element.
2. Method according to Claim 1, characterized in that the cutting pattern of the sub-elements is further produced on the basis of a number of layers of the fibre preform that are to be built up.
3. Method according to Claim 1 or 2, characterized in that the fibre preform is produced in that, firstly, fibre material of a sub-element is at least partly laid down and the at least partly laid-down fibre material is then finally cut in accordance with the cutting pattern.
4. Method according to Claim 1 or 2, characterized in that the fibre preform is produced in that at least some of the sub-elements are cut out of the fibre material in accordance with the cutting pattern, and then the cut sub-elements are laid down to produce the fibre preform.
5. Method according to Claim 4, characterized in that before being laid down, the cut sub-elements are sorted with regard to their position within the fibre preform and are laid down in a sorted manner in a material store.
6. Method according to one of the preceding claims, characterized in that the fibre preform geometry is subdivided into a plurality of strip-like sub-elements with a predefined strip width, and the individual strip-like sub-elements are cut off one after another as fibre strips from a continuous fibre strip material, the cutting pattern being produced in that the individual fibre strips are arranged one after another on the continuous fibre strip material, the order of the fibre strips on the continuous fibre strip material being determined by means of the optimization method for trim optimization on the basis of the outer contours of the fibre strips.
7. Method according to one of the preceding claims, characterized in that the cut edges between respective sub-elements that are adjacent in the cutting pattern are also determined by means of the optimization method for trim optimization on the basis of the outer contours of the sub-elements.
8. Method according to Claim 7, characterized in that the cut edges of the sub-elements correspond to the final outer contour of the respective sub-element.
9. Method according to one of the preceding claims, characterized in that the number of sub-elements in the cutting pattern is minimized by means of the optimization method running on the computer.
10. Production system for producing a fibre preform for the production of a fibre composite component with a predefined geometry and final outer contour, configured to carry out the method according to one of the preceding claims, comprising

    - a cutting pattern determining unit, which is configured to subdivide a predefined fibre preform geometry into a plurality of sub-elements which, put together, form the subsequent fibre preform geometry with the predefined final outer contour, and to produce a cutting pattern for cutting the individual sub-elements out of a fibre material by arranging the sub-elements in the cutting pattern on the basis of the outer contours of the individual sub-elements in such a way that, by means of an optimization method running on the cutting pattern determining unit, the trim between adjacent sub-elements of the cutting pattern is minimized, and

    - a production device which is designed to produce the fibre preform from the individual sub-elements by cutting the individual sub-elements in accordance with the cutting pattern produced,

    characterized in that the cutting pattern determining unit is further configured to produce the cutting pattern of the sub-elements on the basis of a predefined fibre angle orientation, a possible cutting angle of the fibre material and a minimum size of a sub-element.
11. Production system according to Claim 10, characterized in that the cutting pattern determining unit is further configured to produce the cutting pattern of the sub-elements on the basis of a number of layers of the fibre preform that are to be built up.
12. Production system according to Claim 10 or 11, characterized in that the production system is designed, firstly, to cut at least some of the sub-elements in accordance with the cutting pattern produced, to temporarily store the cut sub-elements in a material store before being laid down, and to lay down the temporarily stored sub-elements to produce the fibre preform, or in that the production system is designed in each case to at least partly lay down a sub-element by means of a fibre laying unit and to cut the said sub-element in accordance with the cutting pattern produced before a further sub-element is laid down.
13. Production system according to one of Claims 10 to 12, characterized in that the cutting pattern determining unit is further configured to subdivide the fibre preform geometry into a plurality of strip-like sub-elements with a predefined strip width, so that the individual strip-like sub-elements can be cut off one after another as fibre strips from a continuous fibre strip material, the cutting pattern being produced in that the individual fibre strips are arranged one after another on the continuous fibre strip material, the order of the fibre strips on the continuous fibre strip material being determined by means of the optimization method for trim optimization on the basis of the outer contours of the fibre strips, and the production system further having a material providing device for providing a continuous fibre strip material, the cutting device being designed to cut the fibre strips out of the continuous fibre strip material provided in accordance with the cutting pattern.
14. Production system according to one of Claims 10 to 13, characterized in that the cutting pattern determining unit is further configured to determine the cut edges between respectively successive fibre strips by means of the optimization method for trim optimization on the basis of the outer contours of the fibre strips.
15. Production system according to one of Claims 10 to 14, characterized in that the cutting pattern determining unit is further configured to minimize the number of sub-elements in the cutting pattern by means of the optimization method running on the cutting pattern determining unit.

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