DE102006025753B4 - Method for introducing reinforcing fibers into a semifinished textile product, semi-finished textile product with incorporated reinforcing fibers, and fiber composite component - Google Patents

Abstract

Method for introducing reinforcing fibers (10) into a textile semifinished product (12) for producing fiber composite components, characterized in that the reinforcing fibers (10) are driven into the textile semifinished product (12) in a mechanically stabilized state, wherein the mechanically stabilized state Impregnating the reinforcing fibers (10) is provided with a liquefied gas and subsequent volatilization of the gas, during which volatilization, the driving of the reinforcing fibers (10).

Description

The The present invention relates to a method for introducing reinforcing fibers in a textile semi-finished product according to the preamble of claim 1, a semi-finished textile product with incorporated reinforcing fibers, as well as a fiber composite component.

Textile Semi-finished products (eg fabrics, scrims, braids, nonwovens, etc.) for example, for the production of fiber-reinforced components, also referred to as "fiber composite components", needed.

The Use of fiber composite components is mainly because of their high specific strength (ratio from strength to weight) in many applications interesting. A fiber composite material is a mixed material, in general consists of two main components, namely a matrix and therein embedded fibers. Through mutual interactions of these Receives components the material higher quality Properties as each of the two individually involved components.

at The production of fiber composite components will be fibers, single-layered semi-finished textile products or multi-layer semi-finished textile products of several such over each other layered layers and in a matrix (eg resin) embedded.

With layered fiber materials can be particularly easily multiaxial reinforcing structure create, in which the fibers in each case in the same or are arranged in different directions. If these layers in Stacking direction are interconnected only by the matrix, So there is a danger of mecha African loads of the component a delamination. An additional reinforcement in the stacking direction ("Z direction") is therefore desirable.

From the DE 196 28 388 A1 is a semi-finished textile in the form of a multi-layer fiber preform for the production of fiber composite components known. In this semi-finished product, fibers of several fiber material layers arranged in the direction of flow are arranged one above the other in the X and Y directions on a carrier layer by means of embroidering in a plurality of layers. In order to achieve a defined reinforcement in the direction of the Z axis on the finished fiber composite component, reinforcing fibers formed at least in regions from further fibers are arranged in the direction of the Z axis by means of embroidering.

This Known method for introducing reinforcing fibers into a textile Semifinished products have a number of disadvantages. A first disadvantage exists in that a special substrate (carrier layer) for fixing the introduced Reinforcing threads is needed. Furthermore allows the known method no introduction of individual reinforcing fibers but only of formed from it linear textile structures such as Yarns or plying. After all does that known method to a considerable mechanical damage of the semi-finished by the embroidery needles used.

A method according to the preamble of claim 1, for introducing reinforcing fibers into a textile semifinished product is known from WO 03/011576 A1 known. In this method, the semi-finished product is first pierced from one side by a rotating pathway ("pathway deposition probe") and inserted a reinforcing fiber in the channel created by the needle in the semifinished product when retracting the needle from the other side.

adversely is in this known method, especially the damage of the Semifinished by a compared to the diameter of the introduced reinforcing fiber relatively thick sized needle to form an insertion channel.

at both known methods leave the needles used cavities, in which z. B. at a later Infiltration with resin material excess resin accumulates, causing the mechanical properties of the finished fiber composite impaired become.

Out the article "Li, Yuan-Yao et al .: Activation studies of vapor-grown carbon fibers with supercritical fluids. In: Carbon, 2001, Bd. 39, pp 2143-2150 "is a Pre-treatment of special carbon fibers known, among others using supercritical fluids including supercritical fluids Carbon dioxide. The known pretreatment serves to improve the adhesion between fiber and polymer matrix in an article to be produced therewith Fiber composite material.

Out the article "Zhao, Xi et al .: A novel method of producing conductive aramid fibers using supercritical carbon dioxide. In: Surface & Coatings Technology, 2006, Bd. 201, pp. 628-636 "is a Pretreatment of a fiber for the purpose of applying an electrical conductive Coating known. Again, this pretreatment can be done using made of supercritical carbon dioxide.

It It is an object of the present invention to provide a method of the beginning specify the type mentioned, in which the above-mentioned disadvantages can be avoided from the prior art and in particular textile Semi-finished products can be produced, by means of which fiber composite components with improved strength can be made.

These Task is solved by a method according to claim 1, a semi-finished textile according to Claim 7 or a fiber composite component according to claim 8. The dependent claims relate advantageous developments of the invention.

The Invention allows in particular the mechanical reinforcement of so-called preforms in fiber composite technology. There will be no special underground needed the semi-finished products or preforms are less damaged and no auxiliaries or residues remain in the preform. The infiltriability does not differ favorably from other resin-free preform types.

By that to a reinforcing fiber or one of several reinforcing fibers existing structure (eg reinforcing thread, "roving" etc.) guided liquefied Gas, a mechanically stabilized "reinforcing fiber needle" is formed, even without prior training of an insertion into the textile semifinished product can be driven or stabbed. In other words, form the reinforcing fibers even in the textile penetrating "needles". If the gas during the Penetration of the reinforcing fibers vaporized into the semi-finished textile, so this gas forms a shell, the facilitates the penetration. After evaporation of the gas remains one in the desired one Direction introduced reinforcing fiber or one of such reinforcing fibers formed reinforcing structure like z. B. a thread in the textile semifinished product.

to Achieve as much as possible effective mechanical reinforcement effect through the reinforcing fibers to be introduced it is advantageous that the liquefied gas surrounding the reinforcing fibers in the reinforcing fibers is allowed to penetrate. In particular, the reinforcing fibers with the liquefied Gas impregnated in such a way be that this gas cavities such as Capillaries in or on the reinforcing fibers, at least for the most part, if not substantially completely filled.

At most, the "reinforcing fiber needle" is slightly thicker as the reinforcing fiber (s) themselves. As a result, the puncture channel remains very small and the surrounding fibers of the semi-finished product are hardly moved. The gas jacket can be a sliding film when driving or piercing form and reduce the resistance. The used gas volatilizes at the end completely by itself from the semi-finished product. The infiltriability will not be affected.

The liquefaction of the gas can by appropriate temperature (cooling) and / or pressurization carried out or supported become.

In a preferred embodiment is liquefied as that Gas liquefied Used carbon dioxide. Carbon dioxide is practically non-toxic in ventilated rooms. the same Advantage can z. B. when using liquefied air or liquefied nitrogen be achieved.

In an embodiment is provided that the liquefied Gas in a (thermodynamic) supercritical Condition to the reinforcing fibers guided becomes. In general, there is a supercritical Condition of a substance then if its temperature above the critical temperature and whose pressure is above the critical pressure and the difference between "gaseous phase" and "liquid phase" is not is more noticeable. In this regard, becomes a supercritical Gas often as supercritical Fluid refers.

Regarding the use of a supercritical liquefied Gas is suitable for. B. again carbon dioxide in practice especially good, since its critical temperature of 31 ° C is about room temperature and thus, this state is essentially alone in a simple manner be achieved by pressurization (critical pressure: about 7.4 MPa) can.

Basically, for the invention Any fiber types are used. In addition to a variety of Natural fibers come as chemical fibers z. As carbon fibers, glass fibers or aramid fibers. If individual fibers as such are to be introduced into the semi-finished textile, so are fibers with cavities, the one impregnation with the liquefied Allow gas preferred (eg porous Man-made fibers). Alternatively or additionally, cavities such as capillaries may also be considered interspaces within one formed from reinforcing fibers reinforcing thread be provided.

In a preferred embodiment becomes the liquefied one Gas under elevated Provided pressure in a dispensing nozzle, from which the reinforcing structure consisting of one or more reinforcing fibers and delivered is driven into the textile semi-finished product. In such a dispensing nozzle can easily the liquefied gas with the reinforcing structure be brought into contact. In the discharge nozzle, it may be z. B. around a nozzle act, driven out of which one or more reinforcing fibers and are driven into the textile semi-finished product.

At a substantially lower pressure (e.g., atmospheric pressure) outside the dispenser nozzle, the vaporization of the gas supplied to the reinforcing fiber (s) begins immediately after the exit of the reinforcing fiber (s) from the dispenser nozzle. In this respect it is favorable to ver Positioning reinforcing semi-finished product immediately behind a dispensing nozzle outlet opening to drive the solidified reinforcing fibers.

A reinforcing fiber or a reinforcing thread formed of a plurality of such fibers z. B. provided as a continuous material and before or after the mechanical Stabilization by the liquefied Gas, and before or after the drift into the semi-finished textile, in individual sections are made up. The length of the individual reinforcing fiber sections can hereby z. B. to the desired Penetration depth or the thickness of the textile semifinished product to be selected adjusted.

at Use of an aforementioned "reinforcing fiber nozzle" can this Nozzle a continuous material (eg filament) supplied which is inside the nozzle with the liquefied gas is brought into contact and which after driving into the textile semi-finished product in the region between the nozzle outlet opening and the semifinished product, in particular z. B. immediately adjacent the nozzle outlet opening and / or immediately adjacent to the surface of the semifinished product, assembled by cutting becomes.

In one embodiment, it is provided that the textile semifinished product is formed from at least one extensively extended fiber material layer with fibers lying in a layer plane and the reinforcing fibers are driven substantially orthogonal to the layer plane. In this case, therefore, in particular the Z-direction can be provided as a reinforcing direction, as this is usually advantageous and in itself from the above-mentioned prior art according to the DE 196 28 388 A1 as well as the WO 03/011576 A1 already known. In the context of the invention, however, should by no means be ruled out that the reinforcing fibers are driven in a different direction, as z. B. may be useful due to the expected on a finished fiber composite component loads.

at the textile semifinished product is in a preferred embodiment to a preform, in the context of the production of a fiber composite component is still brought into a final contour. In a known manner Such a semi-finished product or a preform binder and / or a partially cured Mat rixmaterial included, even before the reinforcing fibers according to the invention be introduced. In another embodiment, the textile Semifinished product first through the reinforcing fibers reinforced and only afterwards infiltrated with the relevant matrix material (eg resin matrix), and cured.

The Type, number and technical realization of infiltration steps and precompacting or compaction steps in the manufacture of the Fiber composite components are in the context of the invention of subordinate Meaning and can be extensively modified. The same applies to the layer structure of a multilayer Semi-finished product (eg several fiber material layers with different from each other Fiber directions) as well as the materials used for the fibers and reinforcing fibers (eg, carbon fibers, natural fibers, etc.) as well as the matrix (e.g. As resins, elastomeric plastics, thermoplastics, etc.).

The inventive method is suitable, for example, for the production of structural components or fittings in the aircraft industry.

The Invention will be described below with reference to an embodiment with reference to the enclosed Drawing further described. In this drawing shows schematically and not to scale:

1 a system for introducing reinforcing fibers into a textile semifinished product.

1 illustrates a "needleless fiber injection system" for introducing a reinforcing fiber 10 in a semi-finished textile 12 for producing a fiber composite component.

In known manner, the semifinished product 12 from a multilayer stack of fabric layers in which fibers are oriented in one direction or predetermined directions, respectively, lying in an XY plane. The stacking direction of the semifinished product 12 corresponds to the Z direction.

The core of the system is a dispensing nozzle or nozzle body 14 , which is supplied in the figure from above with an endless fiber material (see arrow), which is withdrawn from a supply roll, not shown, and which in the illustrated embodiment is a single aramid fiber (reinforcing fiber 10 ). Alternatively, instead of the single fiber 10 z. B. a "roving" can be used.

The reinforcing fiber 10 is driven by a clocked operated (not shown) feed device from above into a cylindrical fiber channel 16 of the nozzle body 14 fed.

The fiber channel 16 has a diameter corresponding to the diameter of the supplied reinforcing fiber 10 is adapted, and runs in the illustrated embodiment in a straight line through an inner nozzle part 18 therethrough.

The inner nozzle part 18 is at least on the exit side (in the figure lower) end under Be Admission of an annular gap 20 from an outer nozzle part 22 surrounded, the lower end of a nozzle outlet opening for the exit of the reinforcing fiber 10 formed. The annular gap 20 is via one or more gas supply passages 24 supplied with liquefied carbon dioxide, which is in the region of the annular gap 20 in pores of the reinforcing fiber 10 penetrates and thus the reinforcing fiber 10 immediately before exiting the nozzle body 14 impregnated with liquid carbon dioxide. In the illustrated embodiment, this is supercritical carbon dioxide with a temperature of some 10 ° C above room temperature and a pressure of about 8 to 10 MPa.

If the material of the reinforcing fiber 10 from the nozzle body 14 exit and there in an "atmospheric environment" (normal conditions) occurs, the carbon dioxide evaporates and allows the fiber material solidify here temporarily.

The solidified fiber material forms in this state a "reinforcing fiber needle", which in the textile semifinished product 12 is driven in and remains after complete evaporation of the carbon dioxide as a reinforcing fiber therein.

For the preparation of the supplied as continuous material reinforcing fiber 10 is a cutting device 26 provided by means of which after the exit of a solidified reinforcing fiber portion of the nozzle body 14 this section is cut off.

In the illustrated embodiment, it is in the semi-finished textile 12 around a precompacted stack of multiple fiber material layers in the XY plane, which forms the plane of extent of the layer stack. The reinforcing fiber 10 is in contrast orthogonal to this semi-finished product, ie in the Z-direction in the semifinished product 12 stabbed.

The introduction of the individual mechanically stabilized fiber sections takes place in cycles: in a first step, a predetermined length of the fiber 10 by means of the feed device through the fiber channel 16 of the nozzle body 14 driven so that one out of the nozzle body 14 emerging fiber section in the semifinished product 12 is stabbed. In a second step, the feed of the fiber 10 briefly stopped, the cutting device 26 operated to cut the already driven fiber portion and the nozzle body 14 moved a bit in the X and / or Y direction. These steps can preferably be carried out completely automatically, in particular in a program-controlled manner repeatedly.

In a variant of such a cyclic operation, which may also be automated, the advancement of the amplification fiber 10 through the nozzle body 14 himself, for this purpose, in a first step out of the in 1 shown position by means of a suitable drive (not shown) is moved in the Z direction down and this case the solidified fiber portion in the textile 12 pushes. During this downward movement of the nozzle body 14 becomes the reinforcing fiber 10 by a (not shown) clamping device relative to the nozzle body 14 fixed. Then in a second step with the nozzle body 14 down with moving cutter 26 for cutting off the reinforcing fiber 10 pressed, the nozzle body 14 together with the cutting device back up to the position according to 1 moved back and moved a little way in the XY plane. Finally, in a third step, the clamping device is released and a portion of the reinforcing fiber 10 with a predetermined length by means of the feed device from the nozzle body 14 pushed out to the bottom.

Common to both operating variants is that always after a relative displacement between the nozzle body 14 and semi-finished textile 12 in the XY plane, the plunge step in the Z direction is repeated. At each cycle of operation, a consolidated reinforcing fiber section is incorporated into the material 12 driven. This is repeated until the desired number and arrangement of reinforcing fiber sections has been introduced.

The use of the schematically drawn nozzle body 14 for driving the reinforcing fiber section is of course to be understood only as an example and can be widely modified in practice.

In particular, it is also possible for a nozzle body 14 including cutting device 26 the illustrated type only for solidifying and making up the reinforcing fiber 10 and a downstream means for driving the reinforcing fiber section provided therewith into the semifinished product 12 provided.

Also, the material of the reinforcing fiber 10 viewed in the axial direction (Z direction) over a larger area than in 1 represented within the nozzle body 14 be brought into contact with the liquefied gas, the z. B. at least as long as the driven per piercing cycle reinforcing fiber length can be.

Finally, a fiber delivery device with a plurality of outlet openings for the simultaneous dispensing or driving of a plurality of reinforcing structures may be provided in the textile semifinished product. Such a dispenser may, for. B. a structurally combined plurality of dispensing nozzles of the type described above, wherein the individual dispensing nozzle z. B. can be supplied via a common LPG supply.

Claims (8)

Process for introducing reinforcing fibers ( 10 ) into a semi-finished textile product ( 12 ) for the production of fiber composite components, characterized in that the reinforcing fibers ( 10 ) in a mechanically stabilized state in the textile semifinished product ( 12 ), wherein the mechanically stabilized state by impregnating the reinforcing fibers ( 10 ) with a liquefied gas and subsequent volatilization of the gas, during which volatilization the driving-in of the reinforcing fibers ( 10 ) he follows. The method of claim 1, wherein as the liquefied gas liquefied Carbon dioxide is used. Method according to one of the preceding claims, wherein the liquefied gas in a supercritical state in the reinforcing fibers ( 10 ) is allowed to penetrate. Method according to one of the preceding claims, wherein the reinforcing fibers ( 10 ) are used in the form of a roving. Method according to one of the preceding claims, wherein the liquefied gas under elevated pressure in a dispensing nozzle ( 14 ), from which one or more reinforcing fibers ( 10 ) out into the semi-finished textile ( 12 ) are driven. Method according to one of the preceding claims, wherein the semi-finished textile product ( 12 ) is formed from at least one extensively expanded fiber material layer with fibers lying in one layer plane (XY) and the reinforcing fibers ( 10 ) are driven substantially orthogonal (Z) to the plane of the layer (XY). Textile semi-finished product ( 12 ) with reinforcing fibers incorporated according to a method according to one of claims 1 to 6 ( 10 ). Fiber composite component, produced by means of a textile semifinished product ( 12 ) according to claim 7.