DE102011102950A1 - Laying head, useful for the deposition of fiber assemblies for the manufacture of textile preforms, comprises at least fiber supply device, placing roller and heating device for heating of thermally activatable bonding agent - Google Patents

Abstract

Laying head, which at least partly consists of carbon fibers, comprises at least a fiber supply device (3), a placing roller (4) and a heating device for the heating of a thermally activatable bonding agent for the fixation of the textile preform. The laying head comprises two contact surfaces, which are contacted by the fiber arrangement fed through the fiber supply device and conducted through the laying head to the discard roll. Laying head, which at least partly consists of carbon fibers, comprises at least a fiber supply device, a placing roller and a heating device for the heating of a thermally activatable bonding agent for the fixation of the textile preform. The laying head comprises two contact surfaces, which are contacted by the fiber arrangement fed through the fiber supply device and conducted through the laying head to the discard roll. The two contact surfaces run in a electrically conducting manner as pair of electrodes and is connected with a power supply (6), where the electrically conductive carbon fibers of the fiber assembly between the pair of electrodes forms a heating track (7) of the laying head, which provides the heating device of the laying head. Independent claims are also included for: (1) a laying system for placing and fixing of fiber assemblies for producing textile preforms, comprising the laying head and a means for moving the laying head relative to a substrate, on which the fiber assemblies are stored; and (2) deposition of fiber assemblies, which at least partly consist of carbon fibers, for the manufacture of textile preforms using the laying head, comprising supplying the fiber assembly to the laying head by means of the fiber supply device, setting a current to the pair of electrodes, heating the fiber assemblies due to the internal resistance of the carbon fibers, depositing the fiber assembly by the placing roller and fixing to a substrate by thermal activating of the bonding agent under formation of the textile preform.

Description

The invention relates to a laying head and a corresponding method for depositing fiber arrangements for the production of textile preforms, which consist at least partially of carbon fibers.

For the production of textile preforms tissue or scrims are used in the prior art. The disadvantage is often a result of cutting these relatively expensive materials. Laying heads are therefore increasingly being used for laying down the fibers as scrim, which deposit the lower-cost raw fibers on a substrate and thus avoid waste as well as load path-compatible fiber layers. The fibers are provided with a thermally activatable binder or prepregs in which the fibers are already provided with binder and heated by means of a heat source such as an infrared radiator, a laser or a heated deposition roller of the laying head. The fiber is fixed on a substrate with a depositing roller. The cooled binder fixes the spreading of the fiber and the adhesion to the substrate.

A technical challenge is still to control and regulate the heating to soften or activate the binder. In particular, by heating the pressure or Ablegerolle it can lead to contamination of the role by depositing binder material on the roll; this can further disrupt the process and affect product quality. In order to heat and activate the binder, additional equipment has been required so far, such as infrared radiators, lasers, or heating devices integrated in the depositing roller.

Also the DE 10 2007 012 608 B4 describes an apparatus and a method for producing a preform for a force flow compatible fiber composite structure. There is a corresponding sliver piece, which may comprise carbon fibers, cut from a sliver, arranged at a predetermined receiving position by means of a laying device and positioned and further placed by means of a binder material. There, the binder is activated via the laying head, which has a heating device, and accordingly heats the sliver piece to which the binder is applied as it passes through the laying head.

Furthermore, from the DE 10 2008 019 147 A1 a method for the production of fiber preforms is known, with which several dry fiber assemblies can be stored simultaneously next to each other. For this purpose, several dry fiber rovings are at least partially fed to one another at different speeds from one another independently of one another at the same time, and then simultaneously deposited side by side directly on the mold or on already deposited fiber rovings. In addition, it is described there to provide the dry fiber rovings before depositing with a thermoplastic binder, which can be activated by different heaters. Based on this prior art, the object is to provide a depositing device for carbon fiber containing fiber assemblies, which allows the rapid laying and fixing of carbon fibers on a substrate in a trouble-free process, the device should be structurally simple.

This object is achieved by a laying head with the features of claim 1.

Furthermore, this object is achieved by a laying system with the features of claim 7.

In addition, it is desirable to provide a correspondingly optimized, trouble-free deposition process.

This object is achieved by the method having the features of claim 9.

Further developments of the laying head, the laying system and the method are carried out in the respective subclaims.

An inventive laying head for depositing fiber assemblies with carbon fibers to produce textile preforms therefrom with a thermally activatable binder comprises fiber feeding means for feeding the fibers to a depositing roller and two contact surfaces leading from the feeding means fed through the fiber feeding means to the depositing roller through the laying head Fiber arrangement can be contacted. These two contact surfaces are designed to be electrically conductive as a pair of electrodes and connected to a power source. The electrically conductive carbon fibers contained in the fiber arrangement, which are guided between the contact surfaces and contact them, can form a heating path of the device between the pair of electrodes thus created, ie a distance along which a current flow applied to the carbon fibers by the electrode pair as a result of the internal resistance the carbon fibers leads to the heating of the same. The heated carbon fibers thus provide the necessary heating for the thermally activated binder, wherein the energy input is advantageously concentrated on the binder immediately surrounding the fiber, and surrounding areas of the substrate on which the fibers are deposited, are not affected. This is advantageous an intrinsic heater in the abzulegenden Fiber arrangement created that can be realized in a simple manner and which allows the fiber array can be quickly placed on a substrate by the targeted by the current flow and rapid heating of the electrically conductive carbon fibers themselves. The heater is very easy to build and takes up relatively little space to complete; the establishment of additional heaters deleted.

In a preferred embodiment, the laying head has a deflection roller arranged in the fiber feed direction upstream of the laying roller. Instead of static contact surfaces form here advantageously easy and space and components sparingly, the guide roller and the Ablegerolle the two contact surfaces and are electrically conductive designed as a pair of electrodes and connected to the power source. Here, therefore, the heating of the device by the contained in the fiber assembly electrically conductive carbon fibers, which are guided between the guide roller and the Ablegerolle and contact them formed.

Alternatively, the electrode pair may be formed by only one of the rollers, be it a pulley or the depositing roller, and a static contact surface. Also, the heating section between two pulleys, which are both arranged upstream of the depositing roller can be realized. The second pair of deflection rollers designed as electrodes can then be arranged directly in front of or upstream of the depositing roller in the laying head.

In a further embodiment of the laying head, the power source can be operatively coupled to a control device. This ensures that the amount of heat generated by the electrically conductive carbon fibers is selectively adjustable, so that a defined melting and consequently a defined adhesion to the substrate on which the fiber is to be stored, is achieved.

Due to the defined melting and thus the prevention of heat transfer to other areas of the substrate, the carbon fibers are sufficiently fixed, however, the preform remains so limp that it can be easily pressed into a desired shape.

The fiber assembly may be a sliver or a fiber bundle, a so-called roving, which either contains or consists entirely of carbon fibers.

The thermally activatable binder may be a powdered or liquid binder that has been applied to the fiber assembly. Accordingly, it is favorable if, in a further embodiment of the laying head, this comprises an application device for the pulverulent or liquid binder.

Alternatively or additionally, the binder may also be provided by binder filaments contained in the fiber assembly.

Preferably, however, the fiber assembly is passed unhindered through the laying head where it is heated and deposited on the substrate, which comprises or consists of the thermally activatable binder. Such a substrate may be a thermoplastic binder fleece. The heated in the laying head of the invention fiber assembly is pressed by the depositing roller on the thermoplastic substrate and thus fixed. The thermoplastic material of the substrate is heated only immediately and locally around the fibers, so that contamination of the deposition roller is minimized.

A laying system according to the invention for depositing and fixing fiber arrangements, which consist at least partly of carbon fibers, with which the fibers can be automatically deposited on a substrate for the production of textile preforms, comprises a laying head according to the invention and means for moving the laying head relative to the substrate on which the fibers are deposited. The laying system is suitable for the production of flat textile preforms without cutting, but can also be used to reinforce finished 3D preforms on the load path.

In one embodiment, the laying installation can have a plurality of laying heads which are arranged parallel and / or in series and / or offset from one another. Thus, large-area textile preforms can be created quickly.

Furthermore, it can be provided that the laying system according to the invention comprises one or more pressure devices which are coupled to the laying head (s). In this case, the pressure device is arranged trailing the laying head and has means for exerting on the deposited from the laying head on the substrate fiber assembly (s) a predetermined pressure. Thus, advantageously, this contact pressure, which fixes and compacts the fibers on the substrate, need not be exerted by the depositing roller of the laying head. This is particularly advantageous in the variant in which the heated fibers are deposited on a binder fleece, since now the Ablegerolle less dirty or not at all and thus no bovine material gets into the interior of the laying head. The pressing device arranged downstream of the laying head presses the deposited hot fibers into the binding fleece so that it locally melts and fixes the fibers.

• – des Zuführens der Faseranordnung mittels der Faserzufuhreinrichtung in den Legekopf, sodann
• – Strom an das Elektrodenpaar anlegen, das durch die zwei von der Faseranordnung kontaktierten Kontaktflächen in dem Legekopf gebildet wird, mittels einer Stromquelle, die entsprechend mit den beiden Kontaktflächen verbunden ist, und
• – Bereitstellen der von den Carbonfasern der Faseranordnung gebildeten Heizstrecke zwischen den Kontaktflächen, dadurch
• – Erwärmen der Faseranordnung infolge des inneren Widerstands der Carbonfasern, und dadurch thermisches Aktivieren des Bindemittels, das von der abzulegenden Faseranordnung umfasst ist,
• – Ablegen der Faseranordnung mittels der Ablegerolle und Fixieren auf einem Substrat durch thermisches Aktivieren des Bindemittels, wobei der Textilvorformling gebildet wird.

The method according to the invention for depositing fiber arrangements which consist at least partly of carbon fibers in order to produce textile preforms, also referred to as textile preforms, using a laying head according to the invention therefore comprises the steps:

• - The feeding of the fiber assembly by means of the fiber feeder in the laying head, then
• - Apply current to the electrode pair, which is formed by the two contacted by the fiber array contact surfaces in the laying head, by means of a power source which is connected to the corresponding two contact surfaces, and
• - Providing the heating line formed by the carbon fibers of the fiber assembly between the contact surfaces, characterized
• Heating the fiber assembly due to the internal resistance of the carbon fibers, and thereby thermally activating the binder comprised by the fiber assembly to be deposited,
• - Laying the fiber assembly by means of the Ablegerolle and fixing on a substrate by thermally activating the binder, wherein the textile preform is formed.

The thermal activation of the binder may, in the case where the binder is included in the fiber assembly, take place already in the laying head from the heating section, when the carbon fibers are heated to a temperature sufficient therefor. Otherwise, when using a substrate, which dar- or provides the binder, the thermal activation takes place only by the deposition of the heated fiber assembly on the substrate.

In the case of pure carbon fiber preforms, maximum homogeneity is advantageously achieved with the method according to the invention, which is advantageous for further processing and also permits defined statements regarding the material quality.

These and other advantages will be set forth by the following description with reference to the accompanying figure. The reference to the figure in the description is to aid in the description and understanding of the subject matter. The figure is merely a schematic representation of an embodiment of the invention. It shows

1 a side sectional view of a laying head according to the invention,

2 a perspective view of a laying head according to the invention with a pressure device of a laying system according to the invention.

The invention relates to a laying head for the production of textile preforms, which consist at least partially of carbon fibers. In order to provide such preforms, laying heads are used in which binder-provided fiber arrangements, also referred to as fiber bundles or rovings, are applied to each other layer by layer, whereby a preform is created. The binder must be heated and thereby activated, then the rovings can be placed in a form with pressure applying Ablegerollen and pressed so that they are fixed to each other. The laying down of the fiber arrangements can be done in accordance with load, even adapted to complicated Kraftflussverläufe. Depending on the load profile, the textile preforms created by laying down the fiber arrangement may thus be unidirectional scrim or multiaxial scrim. The fiber arrangements used must be at least partially formed of carbon fibers, but it may also contain other reinforcing fibers such as glass, aramid or a polyester in the fiber assembly.

Furthermore, it is conceivable for the thermally activatable binder to be present, for example, in the form of thermoplastic fibers which form part of the fiber arrangement. Alternatively or in addition to such binder fibers, the binder may be a powdery melt binder which may be applied to the dry fiber rovings in dust form, for example, by electrostatic charging of the fiber assembly or binder dust. It may also be contemplated to use a liquid binder in which the dry fiber assemblies are dipped or sprayed, rolled or painted onto the dry fiber assemblies. For the purpose of application of the binder, the laying head according to the invention may comprise a corresponding device, but the binder may also be included in the fiber arrangement in advance, before the fiber assembly is fed to the laying head.

Preferably, however, a substrate is used for depositing the fiber assembly, which consists of or contains the binder, so that the fibers heated in the laying head according to the invention are fixed directly there when deposited on the substrate by locally heating the binder. The laying head advantageously remains binder-free, soiling in the laying head is avoided. The binder substrate may be a thermoplastic binder web; but also the use of thermosetting resin systems, especially in dry powder form, is not excluded.

To avoid difficult to control melting of the binder as well as contamination by binder residues on the laying or pressure roller and at the same time to the heater simplified, a device has been proposed according to the invention, as outlined in the single figure:
The laying head shown there has a deflection roller 5 upstream of the depositing roller 4 on, and upstream of the pulley 5 a fiber feeder 3 on which the fibers are in the form of a fiber array 1 , For example, in the form of a roving, the laying head are supplied. The pulley 5 and the offshoot role 4 are electrically conductive as a pair of electrodes 4 . 5 executed and with a power source 6 connected. So can those in the fiber assembly 1 or in the roving contained carbon fibers between the pulley 5 and the offshoot role 4 from one through the power source 6 flowed through. Thus, the electrically conductive carbon fibers of the fiber assembly 1 between the pulley 5 and the offshoot role 4 a so-called "heating section" 7 which represents the heating device for heating the thermally activatable binder of the laying head. The current-carrying carbon fibers heat up due to the internal resistance. The thus formed intrinsic heater of the laying head is therefore very easy to build and takes up relatively little space in the laying head. The term "intrinsic" makes it clear that the heating device of the laying head does not require an external device, but virtually comes from the inside, namely by the heating section through a course section of the fiber arrangement in the laying head itself between the deflection roller 5 and the offshoot role 4 in conjunction with the current applied by the pulley 5 and offshoot roller 4 , which are designed as electrodes, is realized.

The thus heated fiber assembly 1 can then by means of the Ablegerolle 4 on a binder substrate 2 deposited and there by the local heating of the binder substrate 2 be fixed, which may be about a binder fleece made of a polyamide. One such example would be a high-performance polyamide binder fabric with a relatively low activation temperature as Spunfab ^® PA 1,541th

Alternatively, however, the heating of a thermally activated binder that in the fiber assembly 1 is included, along the heating route 7 respectively.

Due to the limited heating distance 7 The energy input focuses exclusively on the fiber arrangement 1 itself, so that the heating does not affect the surrounding area, substrate 2 or fiber layers already deposited thereon, on which the fiber arrangement 1 is filed.

The temperature caused by the energization of the heating system 7 can be achieved by a control device connected to the power source 6 is connected to be set very precisely, so that a defined melting of the in the fiber assembly 1 contained binder and therefore a defined adhesion of the fiber assembly 1 on the substrate 2 or be achieved on the already deposited fiber layers.

A laying installation for the production of fabric preforms without waste or also for load path-compliant reinforcement of finished 3D preforms comprises one or preferably several laying heads according to the invention, the laying installation having means for moving the laying head (s) relative to a substrate on which the fiber arrangements are to be deposited. The substrate, for example a binder fleece, rests on a support structure which is made of aluminum or an abrasive paper, for example. The relative movement between the laying head and the substrate can be produced by a laying head guided over a static substrate or vice versa by the substrate guided past below the laying head.

Thus, for example, a substrate web under a plurality of parallel and / or staggered and / or staggered laying heads of a laying plant are performed, which deposit the fiber assemblies on the substrate, where they are fixed due to the thermally activated binder. In general, however, the laying heads can also be present on controllable mobile arms, so that they can be guided over the substrate.

A laying system with several laying heads can also be modular. Furthermore, a laying installation can be equipped with cutting units which cut the formed textile preform in the desired manner.

In 2 is a section of a laying system for storing and fixing fiber arrangements to see that a laying head with a Ablegerolle 4 shows, by means of a not visible here fiber assembly on the substrate 2 filed and heated according to the invention in the laying head. You can see the electrical connections 4 ' . 5 ' , via which the two contact surfaces of the electrode pair are connected to a current source (not shown here). In this variant does not form the Ablegerolle 4 one of the contact surfaces, but there are provided for deflection rollers or statically formed contact surfaces in the laying head, via the contacts 4 ' . 5 ' connected to the power source.

The relative movement between the laying head and the substrate 2 is indicated by the block arrows a, a ', where a illustrates a movement of the laying head, while a' indicates the alternative substrate movement. Regardless of which variant is selected, pass from the laying head on the Ablegerolle 4 on the substrate 2 deposited fibers the laying head downstream pressure device 10 which the required Applying pressure to the fibers heated in the laying head, so that these on the substrate 2 be fixed. The pressure device 10 can, as in 2 outlined, simply by a pinch roller 11 be realized, which, as shown, for example, with a spring 12 coupled to the pinch roller 11 with a certain pressure over the deposited fibers to lead. For example, feed rates of up to 300 mm / sec can be achieved when laying fibers.

The molding of the preform remains possible because of the defined melting and the thus prevented or reduced heat transfer to other areas of the substrate 2 Although the carbon fibers are sufficiently fixed, the created textile preform still remains so limp that it can be easily pressed into a desired shape.

The best homogeneity and quality of the preform is achieved with pure carbon fiber arrangements, which can therefore be handled particularly well during further processing, in particular since more general statements about the material characteristics can be made on account of the homogeneity.

Thus, the laying head according to the invention and the method that can be carried out for depositing fiber arrangements for the production of textile preforms enables improved product quality while at the same time simplifying the manufacturing apparatus and with improved process reliability, since, for example, the failure of the depositing roller no longer occurs due to contamination by binders. The temperature for activation of the binder can be controlled quickly and directly by the applied current flow, wherein the heating takes place directly at the point where it is needed, namely in the fiber itself. The use of additional structures for heating the binder is eliminated.

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 102007012608 B4 [0004]
• DE 102008019147 A1 [0005]

Claims (10)

Laying head for depositing fiber arrangements ( 1 ) for the production of textile preforms, which at least partially consist of carbon fibers, wherein the laying head at least one fiber feed device ( 3 ), an off-take role ( 4 ) and a heating device for heating a thermally activatable binder for fixing the textile preform, characterized in that the laying head comprises two contact surfaces, which from the through the fiber feed device ( 3 ) fed through the laying head to the Ablegerolle ( 4 ) guided fiber arrangement ( 1 ), wherein the two contact surfaces are electrically conductive as a pair of electrodes ( 4 . 5 ) and with a power source ( 6 ), wherein the electrically conductive carbon fibers of the fiber arrangement ( 1 ) between the pair of electrodes ( 4 . 5 ) a heating line ( 7 ) of the laying head, which provides the heating device of the laying head. Laying head according to claim 1, characterized in that the laying head at least one deflection roller ( 5 ) in Faserzuführrichtung upstream of the Ablegerolle ( 4 ), wherein at least one of the deflection rollers ( 5 ) and / or the depositing roller ( 4 ) forms at least one of the two contact surfaces. Laying head according to claim 1 or 2, characterized in that the power source ( 6 ) is operatively coupled to a control device, wherein an amount of heat provided by the electrically conductive carbon fibers via a means of the power source ( 6 ) adjustable current flow is adjustable. Laying head according to at least one of claims 1 to 3, characterized in that the binder - is a powdered or liquid binder, which on the fiber assembly ( 1 ), or - is provided by binder filaments which are in the fiber arrangement ( 1 ), or - by a substrate ( 2 ) on which the fiber arrangement ( 1 ), the substrate ( 2 ) is in particular a thermoplastic binder fleece. Laying head according to claim 4, characterized in that the laying head comprises an application device for the powdered or liquid binder. Laying head according to at least one of claims 1 to 5, characterized in that the fiber arrangement ( 1 ) is a sliver or a fiber bundle having a plurality of carbon fibers. Laying plant for depositing and fixing fiber arrangements ( 1 ) for the production of textile preforms, which at least partially consist of carbon fibers, comprising a laying head and means for moving the laying head relative to a substrate on which the fiber arrangements ( 1 ) are to be placed, characterized in that the laying head is a laying head according to at least one of claims 1 to 6. Laying installation according to claim 7, characterized in that the laying installation comprises - a plurality of laying heads arranged in parallel and / or in series and / or offset from one another, and / or - at least one pressure device ( 10 ), which is arranged to follow the laying head and coupled thereto, wherein the pressure device ( 10 ) Medium ( 11 . 12 ) for applying a predetermined pressure to that of the laying head ( 10 ) on the substrate ( 2 ) filed fiber arrangement ( 1 ) having. Method for depositing fiber arrangements ( 1 ) which are at least partially made of carbon fibers, for the production of textile preforms using a laying head according to one of claims 1 to 6, comprising the steps of - the laying head feeding the fiber arrangement by means of the fiber supply means ( 3 ) - applying a current to the pair of electrodes ( 4 . 5 ) formed by the two contact surfaces defined by the fiber arrangement ( 1 ) are contacted by means of a power source ( 6 ) connected to the two contact surfaces and providing the carbon fibers of the fiber assembly ( 1 ) formed heating section ( 7 ) between the two contact surfaces, thereby - heating the fiber assembly ( 1 ) due to the internal resistance of the carbon fibers, - depositing the fiber arrangement ( 1 ) by the depositing roller ( 4 ) and fixing on a substrate ( 2 ) by thermally activating the binder to form the textile preform. Method according to claim 9, wherein the thermal activation of the binder, which is to be deposited by the fiber arrangement ( 1 ), from the heating section ( 7 ) is carried out in the laying head or wherein the thermal activation of the binder, by the substrate ( 2 ) is formed by depositing the heated fiber assembly ( 1 ) on the substrate ( 2 ) he follows.

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