DE102012205906A1 - Method for manufacturing dynamic braid pattern for fiber reinforcement element of fiber composite component, involves changing number of nodes with fiber strands or number of fiber strands with constant number of nodes in various regions - Google Patents

Abstract

The method involves changing a number of nodes with equal number of fiber strands or a number of parallel running fiber strands with constant number of nodes in various regions of a fiber composite component depending on an expected load situation during manufacturing fibers reinforcement element. The fiber strands are not interrupted and twisted on a core, where the fiber strands comprise an angle to a longitudinal axis of the core. The angle is influenced by feed speed of the core. Multiple feed plates (3) are moved by gear units (2) and individually or combinedly actuated. The fibers are selected from carbon fibers, glass fibers, aramid and textile fibers, natural fibers and metallic wires. Independent claims are also included for the following: (1) a fiber composite component (2) a radial braiding machine (3) a method for operating a radial braiding machine.

Description

The present invention is a method for varying the weave pattern of fiber-reinforced components without interrupting the braiding process. Further objects are an apparatus for the production of fiber-reinforced components with variable braiding patterns and the use of such components.

Components, in particular fiber-reinforced components, are frequently subjected to varying loads over their dimensions. While at certain component sections, for example, tensile loads prevail, which are particularly well-resisted by unidirectional fiber reinforcements, torsional loads, for example, which are particularly well absorbed by inclined, multiply crossed fiber guides, act on other component sections. It is known that the load-bearing capacity of the fiber-reinforced plastic components depends on both the type, number and direction of the fiber, as well as the number of crossing points of the fibers. Under strong tensile loads, the crossing points can lead to weak points, since at these points the fibers are kinked. On the other hand, crossing points lead to stabilizations of the positions of the fibers to each other and it is possible to form by braiding forms that can not be achieved with winding.

Current methods are to reinforce particularly stressed component areas. This is done, for example, by the use of inserts which absorb part of the load (eg. DE 10 2009 051 459 A1 ). The problem with this is that in addition to a more complex production and the safe power transmission to the depositor must be guaranteed. In addition, load peaks can be expected at the edges of the inserts, which may overload the fiber-reinforced material.

Another procedure ( DE 3344866 A1 ) provides that during a braiding process additional reinforcing fibers are drawn in the axial direction, which should cause increased longitudinal stability. These reinforcing fibers intercept load peaks, but are also present in component sections that do not require such reinforcement.

The DE 102006006337A describes a combination of yarn storage systems that are to be used for the formation of a three-dimensional component. In this process, interleaved reinforcement fiber groups are stabilized by braided or similar thread systems. However, it is not intended that the groups of reinforcing fibers have crossing points, or that the number of such crossing points is varied as a function of the stress.

Methods for producing load-adapted braids are known from the prior art.

The EP 724034B1 describes a device for producing a three-dimensional mesh, in which a plurality of coil paths run parallel, and can change at the coils at defined transfer points between these paths. However, it is not intended to make the transition between different coil paths optional or to change the coil paths by programming the device during the braiding process.

It is therefore the task of proposing a method that allows the number of nodes (fiber crossing points) in the braids of fiber-reinforced plastic components dynamically adapt to the expected load situation in each component section. In addition, a device is required which is capable of producing such dynamic braiding structures.

The terms fibers and fiber strands are used synonymously below. By "parallel fiber strands" is meant fiber strands which are jointly guided at least through subregions of the braid, i. H. they lie directly next to each other on the same side of the crossing fiber strands.

According to the invention the object is achieved by the method according to claim 1. A component produced according to the invention is described in claim 2. The device according to claim 3 is suitable for carrying out the method according to the invention. Claim 7 discloses a method for operating the device. Advantageous embodiments are disclosed in the dependent claims.

The inventive method provides to vary the number of crossing points in the braided fiber reinforcement of components, in particular of plastic components, depending on the expected load situation. In high stress areas, the number of crossing points is reduced. The structure of fiber reinforcement approximates the ratios of wound fiber reinforcement. In areas where a lower load is to be expected, the number of crossing points is increased, so that the stable placement of the fibers on the braid core is very reliable even in bending areas. Moreover, it is possible to eliminate fibers from the braiding process over predetermined component sections.

Due to the intersection of fiber strands in braided fiber reinforcements arise break points of the warp threads, which increase the distance of the weft threads from each other. The fiber coverage of the braided core is thus directly dependent on the number of crossing points.

Conventional braiding methods provide that one or more fiber strands intersect again with one or more fiber strands at a certain angle, often 90 °. The fiber strands are usually braided on a core and thereby have an angle to the longitudinal axis of the core. This angle can be influenced by the feed rate of the core. However, the number of intersecting fiber strands is not affected.

The inventive method now provides that the number of intersecting fiber strands is variable, without interruption, within a component designed. Thus, in areas in which the component must be expected to be subject to high loads, it is preferable for a plurality of fiber strands to run parallel, without crossing with other fiber strands. Advantageously, a very high fiber coverage is achieved. In areas with lower expected load, a higher number of crossings is provided. The number of parallel strands without crossing points decreases, the fiber coverage also decreases.

A further preferred embodiment provides for reducing or increasing the number of parallel fiber strands during the braiding process. This is achieved by a variable number of fiber strands participating in the braiding process. In this way, more or less substantially axially extending fiber strands (standing fibers) can be arranged in sections of the braided component, which are included as needed in the braiding process.

The inventive method for producing dynamic braiding thus varies within a component, the number of nodes with the same number of fiber strands and / or the number of parallel fiber strands with a constant number of nodes, the fiber strands are not interrupted.

The design of how to change the braided pattern across the component dimensions is preferably done in advance on the basis of computer-aided calculations. In these calculations, the load cases are simulated and a suitable variable braiding pattern is determined. In this case, the control data for the computer-aided execution of the method on a braiding machine according to the invention is particularly preferably calculated.

The method according to the invention thus makes it possible to produce fiber composite components with a braided fiber reinforcement and a matrix material surrounding the fiber reinforcement, wherein the fiber reinforcement has different braiding regions as a function of the expected load of the fiber composite component. The braiding areas differ in particular in that, given the same number of fiber strands, the number of nodes varies and / or the number of parallel fiber strands varies with the same number of nodes, with no interruptions of fiber strands between the braiding areas.

The inventive method is suitable in principle for all fiber types for fiber reinforcements of composite materials. In particular for carbon fibers, glass fibers, aramid and textile fibers, natural fibers, metallic wires and even for tapes or band-shaped braided semi-finished products.

Conventional radial braiding machines (braiding wheels) provide bobbins (clappers) arranged on an annular support, which are moved by a circumferential row of driving grooves (impellers) provided with driving grooves. The coil carriers carry the actual coils of which the fiber strands are unwound in the braiding process. The transport discs are driven by one or more, preferably four, motors which transmit the driving force to the transport rollers via gears. The coil carriers move in guide rails. Thus, drive (transport rollers) and guide (rails) are separated for the bobbin. In the center of the annular support, a core is arranged, is braided on and can be moved parallel to the central axis of the carrier, so that one or more layers of braid can be produced one above the other as needed. Optionally, the fibers are redirected to the core via a braiding ring (braiding eye).

The braiding is done by two adjacent bobbins exchange their position, thereby crossing the wound from the coils on the core fibers. Thus, two adjacent coils each belong to a different coil support group, wherein the two coil support groups run in opposite directions on the annular support around the core, and wherein at each position change a crosshairs occurs.

The device for carrying out the method according to the invention now provides that, contrary to the state of the art, no cross-hairs are made at every position change of a bobbin carrier. For this to be possible, the bobbins must move in their movement could happen without it comes to a crosshair.

This is achieved by no longer providing a single row of transport discs, but by providing at least three circumferential rows. The transport discs can be controlled individually or in groups via your drives or the associated gear units. The controller, which takes the coil carrier which path, that is to which adjacent transport disc of the coil carrier is transferred from the current transport disc, is preferably carried out computer-controlled. Each individual bobbin carrier can be handed over to the next or previous transport disk within a circulating row, or it can be transferred to a transport disk in an adjacent row. In this way, any coil carrier can take almost any paths and so highly complex three-dimensional structures are braided. To change the paths, the guide rails in which move the bobbin, turnouts, which determine the transition of the bobbin from a series of transport discs to another. This is preferably done by computer-controlled the way to be taken in the rail is released.

The design of the transport discs corresponds to the known from the prior art embodiments. Furthermore, it is possible to vary the braiding pattern during the braiding process. In this way, depending on the position of the core which is being braided, more or less crossing points of the fibers are produced.

In a preferred embodiment, coil carriers with coils and their fibers can also be taken out of the braiding pattern and virtually parked by the use of further impellers, which can be selectively braked, stopped and restarted. The coils then contribute no fibers to the braid or the fibers extend as so-called standing fibers substantially axially over the core. For this purpose, the braiding wheel preferably has more than three rows of transport discs in at least one section of the braided wheel, the outer rows preferably serving to "park" coil carriers over the entire braiding process or for a predetermined period of time. The transport discs serving the "parking" need not form a complete row on the inner periphery of the wicker wheel. They can also be arranged in only one or more sections. The stopping of the transport discs is preferably carried out via couplings in the gearboxes of the transport discs.

The bobbins are preferred to stop ("parking") driven on the outer vanes and then stopped. The fibers of the coils of this coil carrier are thus not interlaced. To rewrap the fibers, the bobbins are then moved back to the inner vanes, where they then participate in the braiding process again. The fibers of the coils of the meantime parked coil carriers then extend longitudinally (substantially axially) over the component. In the case of repeated lamination of components, wherein the core travels back and forth several times in the braiding wheel, advantageously areas of the core with smaller diameters can be purposefully covered with fewer fibers. (Eg the ends of a pressure tank)

This advantageously not only a change in the braiding pattern during the process but also a change in the number of fibers during the process is possible.

Figures and embodiments

1 schematically shows a conventional braiding pattern according to the prior art, in which two fiber strands are intertwined in each direction. The fiber strands are perpendicular to each other here.

2 schematically shows a braiding according to the invention, in which, during the braiding process, the number of parallel fiber strands was increased from two (area A) to four (area B) dynamically. For ease of illustration, a two-dimensional representation has been chosen. The core, to which such a structure is braided, would in preferred embodiments, for example, extend at an angle of approximately 45 ° to the fiber strands.

3 schematically shows a braiding according to the invention, in which the number of fibers was reduced during the braiding process and then increased again. In region A is a conventional braiding pattern, each with two parallel running fiber strands, which are crossed by two orthogonal extending fiber strands and passed on each changing sides. In area B there is a transition analogous to 2 and four instead of two fiber strands are parallel in one direction. A reduction of the four fiber strands in region C to three parallel fiber strands follows. In this case, the reduction in the number of fiber strands running in parallel is reduced by 4 ) temporarily does not participate in the braiding process. The area C then goes back into an area B by the stave thread ( 4 ) is again included in the braiding process. Shown is only the variation of the parallel fiber strands in one direction. Of course, this can be done in both directions of fiber.

4 shows a schematic section of a complex braid according to the invention, in which the number of parallel fiber strands was varied both in the warp and in the weft direction.

5 schematically shows a section of a wicker ( 1 ). The braiding wheel ( 1 ) has three rows of transport discs ( 3 ) on. Each transport disc ( 3 ) preferably has four grooves, which can detect coil carriers and pass them on to an adjacent transport disc. The transport discs ( 3 ) are driven by drive units ( 2 ), wherein the transport discs ( 3 ) can be controlled individually or in groups. The drive units carry the impellers and are in turn supported by the annular support ( 5 ) of the braiding wheel (radial braiding machine) ( 1 ) held. The control is preferably computerized. In the illustration, only a part of the inner circumference of the annular support ( 5 ) with drive units ( 2 ) and transport discs ( 3 ) equipped. In the actual design, at least three rows of drive units ( 2 ) with transport discs ( 3 ) circumferentially around the entire inner circumference of the annular support ( 1 ) arranged.

6 schematically shows the structure of a wicker wheel according to the invention ( 1 ). The braiding wheel ( 1 ) is different from the one in 5 shown embodiment by the parking areas, the transmission units ( 2a ) as well as transport discs ( 3a ), which serve to park coil carriers that are temporarily not to participate in the braiding process. The coil carriers are controlled by the impellers ( 3 ) to the impellers ( 3a ) in the park areas. Then the impellers ( 3a ) stopped by, for example, in the transmission ( 2a ) a clutch is released.

Embodiment 1 Venturi nozzle (FIG. 7)

7 shows how the braiding patterns can be arranged above a component, in this case a Venturi nozzle, in order to achieve a sample structure adapted to the load as much as possible.

As reinforcement material E-glass fibers with 2400 tex are used. Matrix material is epoxy resin. The number of fibers is 100.

• – Der jeweils gerade Rohrbereich soll eine möglichst hohe Festigkeit und Steifigkeit aufweisen, daher wird ein unverkreuztes Muster (Muster C) gewählt.
• – Bei den Flanschanschlüssen muss die Preform (das trockene Geflecht) noch verschoben werden. Hier ist ein Muster mit vielen Kreuzungspunkte (Muster A) notwendig, damit die Fasern sich nicht zu stark entflechten.
• – Die Durchmesserübergänge sollen eine relativ hohe Festigkeit haben. Hier braucht man aber wenige Kreuzungspunkte, die es ermöglichen, dass man den Flechtwinkel über die Durchmesseränderung anpassen kann. Dies ist bei dem Muster ohne Kreuzungspunkte nicht möglich. Es wurde daher Muster B gewählt.

In this Venturi nozzle, the intentions for the pattern design are as follows:

• - The straight pipe area should have the highest possible strength and rigidity, therefore, an uncrossed pattern (pattern C) is selected.
• - For the flange connections, the preform (the dry mesh) must still be moved. Here is a pattern with many crossing points (pattern A) necessary, so that the fibers do not become too strong.
• - The diameter transitions should have a relatively high strength. Here you need but few crossing points, which make it possible that you can adjust the braid angle on the change in diameter. This is not possible with the pattern without crossing points. Therefore, sample B was chosen.

• – viele Kreuzungspunkte
• – sehr gute Preformstabilität und Drapierbarkeit (Ausbildung der Flansche durch nachträgliches Zusammenschieben des Geflechtes)
• – starke Flechtwinkeländerungen möglich
• – verminderte Festigkeit im Vergleich zu einem Verbund mit gestreckt liegenden Fasern (z.B. Wicklung)
• – hohe Energieaufnahme (Crash), relativ hohe Duktilität bei Verformung, gute Eigenschaften bei komplexen Belastungen

Properties Pattern A:

• - many crossing points
• - very good preform stability and drapability (formation of the flanges by subsequent collapse of the braid)
• - Strong braid angle changes possible
• - reduced strength compared to a composite with stretched fibers (eg winding)
• - high energy absorption (crash), relatively high ductility during deformation, good properties under complex loads

• – wenige Kreuzungspunkte (beliebig einstellbar, an gewünschte Eigenschaften einstellbar, dimensionsabhängig)
• – mäßige Preformstabilität und Drapierbarkeit
• – leichte Flechtwinkeländerungen möglich (Winkel muss über Durchmesseränderungen angepasst werden, trotzdem gute Eigenschaften)
• – Festigkeiten und Steifigkeiten zwischen Muster A und C
• – Energieaufnahme (Crash), Duktilität, Eigenschaften bei komplexer Belastung zwischen A und C

Properties pattern B:

• - few crossing points (arbitrarily adjustable, adjustable to desired properties, dimension-dependent)
• - moderate preform stability and drapability
• - slight braid angle changes possible (angle must be adjusted via diameter changes, nevertheless good properties)
• Strengths and stiffness between patterns A and C
• - Energy absorption (Crash), ductility, properties under complex load between A and C.

• – keine Kreuzungspunkte
• – schlechte Preformstabilität, schlechte Drapierbarkeit
• – kaum Faserwinkeländerungen möglich
• – hohe Festigkeiten und Steifigkeiten (höher als bei gewickelten Bauteilen) hohe mechanische Eigenschaften entscheidend)
• – Energieaufnahme (Crash), Duktilität, Eigenschaften bei komplexer Belastung reduziert im Vergleich zu Muster A und B

Properties pattern C:

• - no crossing points
• - poor preform stability, poor drapability
• - hardly any fiber angle changes possible
• - high strength and stiffness (higher than with wound components) high mechanical properties are crucial)
• - Energy absorption (Crash), ductility, properties under complex load reduced compared to samples A and B.

Embodiment 2 B-pillar (Fig. 8)

8th shows how the Flechtmustervariation invention is used for load-dependent design of a B-pillar for a car.

The reinforcing fiber braid is made of carbon fibers, IMS65, 12k. The number of fibers is 160. The matrix material used is polypropylene (PP).

• – Bereiche zur Aufnahme der Crashenergie (viele Kreuzungspunkte) (Muster A),
• – Bereiche hoher Steifigkeit und Festigkeit für Leichtbau (kaum Kreuzungspunkte), es sind keine Flechtwinkeländerungen und keine komplexen Formänderungen notwendig (Muster C),
• – Bereiche mit höherer Geometriekomplexität und Durchmesserunterschieden (mäßige Anzahl an Kreuzungspunkten); Bereich des T-Stoßes, der nicht ohne Kreuzungspunkte gefertigt werden kann, jedoch eine möglichst hohe Steifigkeit und Festigkeit aufweisen soll (Muster B),
• – Anbindung z.B. für Gurt bringt hohe Beanspruchung senkrecht zur Faserrichtung, hohe Sicherheit bei Crash notwendig (viele Kreuzungspunkte); erhöhte Duktilität und Crashenergieaufnahme notwendig (Muster A).

The structure of the B-pillar is divided into different areas with different requirements, for which suitable braiding patterns are then applied:

• - areas for recording the crash energy (many crossing points) (pattern A),
• Areas of high rigidity and strength for lightweight construction (hardly crossing points), no braiding angle changes and no complex changes in shape are necessary (sample C),
• - areas with higher geometry complexity and diameter differences (moderate number of crossing points); Area of the T-joint, which can not be manufactured without crossing points, but should have the highest possible rigidity and strength (sample B),
• - Connection eg for belt brings high stress perpendicular to the fiber direction, high safety in crash necessary (many crossing points); increased ductility and Crashenergieaufnahme necessary (sample A).

The braiding patterns A, B and C correspond to those described for the Venturi nozzle.

Embodiment 3 Tank (Fig. 9)

9 shows the load-dependent braiding pattern variation using the example of a liquid tank for aerospace applications.

The reinforcing fiber braid is made of carbon fiber, STS40, 24k with a fiber count of 200. The matrix material used is epoxy resin.

In the cylindrical area, many fibers ensure high strength and low overall deformation. (Sample C)

In the transition from the cylindrical region to the pole region there is a strong change in the braiding angle. As many crossing points as possible prevent the fibers from slipping on the core. A high degree of coverage is sought in order to achieve high component strength (sample A).

At the round end areas (Poland), the number of fibers is reduced to 40 (samples B1, B2). Fewer fibers are needed to realize the smaller diameter without causing thickening of the braid. The number of fibers can be varied so that the layer thickness can be adjusted over the round end depending on the requirements. It is thus possible a very homogeneous design of the Polkappenkontur.

The braiding patterns A, B and C correspond to those described for the Venturi nozzle, the pattern B being divided into patterns B1 and B2, and it being understood that the number of fibers of pattern B2 is smaller than that of B1.

LIST OF REFERENCE NUMBERS

1

 braiding

2

 Transmission unit of the transport disc (impeller)

2a

 Transmission unit of the transport disc in the parking area for bobbin carriers

3

 Transport disc (impeller)

3a

 Transport disc (impeller) in parking area for coil carrier

31

 Groove in the transport disc for moving the coil carriers

4

 filler thread

5

 annular carrier of the radial braiding machine

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 102009051459 A1 [0003]
• DE 3344866 A1 [0004]
• DE 102006006337 A [0005]
• EP 724034 B1 [0007]

Claims (8)

Method for producing dynamic braiding patterns for the fiber reinforcement of a fiber composite component, characterized in that in the manufacture of the fiber reinforcement the number of nodes with the same number of fiber strands and / or the number of parallel fiber strands with constant number of nodes in different areas of the fiber composite component in dependence the expected load situation is changed, the fiber strands are not interrupted. A fiber composite component, comprising a braided fiber reinforcement and a matrix material surrounding the fiber reinforcement, the fiber reinforcement having different braiding regions as a function of the expected load of the fiber composite component, characterized in that The braiding areas differ in that, given the same number of parallel fiber strands, the number of nodes varies and / or For the same number of nodes, the number of parallel fiber strands varies, wherein the fiber strands run without interruption between the braiding areas. Radial braiding machine, characterized in that it comprises an annular support which surrounds the core to be wetted annularly, characterized in that the annular support has on its inner circumference at least three parallel rows of drive units with transport discs, wherein the transport discs are suitable fiber coils between two adjacent transport discs to hand over to the same or a neighboring row. Radialflechtmaschine according to claim 3, characterized in that the inner circumference of the annular support has at least partially more than three rows of drive units with transport discs. Radialflechtmaschine according to claim 3 or 4, characterized in that the transport discs are separately controlled by your drive units individually or in groups that can be specified to which adjacent transport disc of the same or an adjacent row, the coil is transferred. Radialflechtmaschine according to claim 5, characterized in that the transport discs can be stopped individually. A method of operating a radial braiding machine according to any one of claims 3 to 6, characterized in that coils are guided past each other on different rows of transport discs, without causing an intersection of the fiber strands of these coils. A method for operating a radial braiding machine according to any one of claims 3 to 6, characterized in that the coils are "parked" by the transport disc, which moves the coil is stopped and the fiber strand of this coil does not participate in any braiding processes until the coil is again in motion is set by the transport disc passes the coil to an adjacent transport disc.

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