WO2011067390A1

WO2011067390A1 - Production of a 3d textile structure and semi-finished fiber product made of fiber composites

Info

Publication number: WO2011067390A1
Application number: PCT/EP2010/068875
Authority: WO
Inventors: Florian H. Gojny; Heide Gommel; Thomas Putz; Tobias Schmidt
Original assignee: Sgl Carbon Se
Priority date: 2009-12-04
Filing date: 2010-12-03
Publication date: 2011-06-09
Also published as: US20120301695A1; DE102009047491A1; CA2782718A1; EP2507039A1

Abstract

The invention relates to a method for producing a 3D textile structure having contours that are matched to the 3D textile structure by means of folding a 2D textile structure.

Description

Production of a 3D textile structure and semi-finished fiber products

made of fiber composites

The present invention relates to a method for producing a 3D textile structure, as well as semifinished fiber products from fiber composites and their use. For the production of composites fibers in the form of woven or non-woven textile structures, as well as in the form of individual, loose fibers can be used. The use of fabrics offers the advantage that fibers can also be introduced into the composite in large quantities and with a comparatively uniform distribution. In addition, the use of a fabric offers the advantage that the fibers are embedded in the fabric and usually require no further attachment to each other. A disadvantage, however, is that the production of a fabric is associated with high costs, especially when using delicate or difficult-to-weave fibers. Fiber fabrics have the advantage over fabrics that they are usually far less expensive to produce. At the same time, however, fiber fabrics have only a very poor cohesion, which makes processing of fiber layers, especially on an industrial scale, much more difficult. To improve the cohesion of fibrous layers, for example, fiber layers can be bonded, be joined or forfeited by hot-melt binding threads or be joined together by needling.

However, a compound of fiber layers by needling leads only to comparatively low loadable fiber layers, while a compound by gluing or using hot melt binding threads carries the risk that at higher temperatures cohesion of the fiber fabric in sufficient strength is no longer given, as the adhesive or melt or decompose the hot-melt binding yarns. There is therefore a need in the art for the development of a further process which makes it possible to produce three-dimensional fiber halves. witnesses made of fiber composites and in which the individual starting material components of the composite, namely the fiber material components, the matrix material component and the fastener components are coordinated.

The attached figures show in an illustrative and non-restrictive manner a fiber-web reinforced composite according to the invention and a plurality of fiber webs produced as intermediates during the process according to the invention:

Fig. 1 shows the folding of scrim in 2 D structures.

Fig. 2 shows the folding of scrim in 3D structures.

The object of the invention is therefore to provide a method for producing a 3D textile structure (three-dimensional semi-finished fiber products, preforms) with contours matched to the 3D textile structure by folding a 2D textile structure.

A 2D structure is created in a fabric by right-angled crossing of warp and weft threads. In a context, a 2D structure is achieved by arranging one or more fiber layers on top of each other with different fiber orientation and interconnecting them by means of a warp thread system. Particularly preferably, the folding takes place accordion-like, by which the textile semifinished product is obtained. In each case, the 2D structure is folded on the basis of the introduced folding contours, so that always the same side of the goods meets each other. This creates a zig-zag fold similar to a concertina. It is further particularly preferred that the 2D textile structure has pleat-supporting gaps which facilitate the construction of the semifinished fiber product to a near-net shape. Preferably, the textile structure consists of the group of scrims, fabrics, braids, knits, felts, nonwovens, combinations of the like and other planar structures (eg films). Optionally, the scrim is coated with a binder, so that after the folding process by a thermal forming process, a stabilized preform such as a leaf spring is obtained.

The textile structure preferably consists of glass fibers, carbon fibers, aramid fibers, ceramic fibers, other polymer fibers (for example polyester, H D polyethylene or polyamides), metallic fibers or mixtures of the aforementioned fibers.

The term "carbon fiber" as used in the present application includes any carbon fiber derived from a carbonaceous raw material fiber, for example, a polyacrylonitrile-based fiber, a polyacetylene-based fiber, a fiber-based fiber polyphenylene, a pitch-based fiber or a cellulose-based fiber, this term in particular comprising fibers having a carbon content of more than 75% by weight, preferably more than 85% by weight, preferably greater than 92% by weight, based in each case on the total weight of the fiber.

Production processes for polyacrylonitrile fibers, pre-oxidized polyacrylonitrile fibers and carbon fibers produced therefrom are described, for example, in the publication by E. Fitzer, LM Manocha, "Carbon Reinforcements and Carbon / Carbon Composites", Springer Verlag, Berlin, 1998, ISBN 3-540- 62933-5, p. 10-24, as well as in the documents US 4,001,382, US 6,326,451, EP 0 384 299 B1 and US 6,054,214.

A process for the production of phenolic resin fibers, as well as a production of binding threads from these threads are known to a person skilled in the art. In addition, such processes are described, for example, in DE 2 308 827 and DE 2 328 313. As ceramic fibers, for example for fiber layers, for example, oxidic and / or non-oxidic fibers based on one or more compounds containing at least one, preferably at least two of the elements carbon, silicon, boron, titanium, zirconium, tungsten, aluminum and Nitrogen include, are used.

The term "fiber layer" as used in the present application encompasses any layer or layer of fibers of any materials or mixtures of materials. In particular, a fiber layer can be a unidirectional layer or a device layer, ie a fiber layer which has, for example, a multiplicity of filaments or yarns, which usually extend in parallel or substantially parallel in one direction. This can for example be done by spreading a rope or any parallel filament or yarn arrangement. In addition, the term fiber layer also includes fiber layers with any arrangement or any course of filaments or fiber sections of shorter length, for example a nonwoven layer. In particular, the fiber layers may also have different length and / or width dimensions or a different shape. Preferably, the ceramic fibers consist entirely or at least 90% by weight, based on the total weight of the ceramic fiber, of compounds comprising at least two of carbon (C), silicon (Si), boron (B), titanium (Ti), zirconium (Zr ), Tungsten (W), aluminum (AI) and nitrogen (N). In particular, ceramic fibers can be used in which the sum of the contents of C, Si, B, N, Al, Zr, Ti, W more than 50 wt .-%, preferably more than 83 wt .-%, preferably more than 85 wt %, in particular more than 95 wt .-% of the total weight of the ceramic fibers, wherein the content of one or more of C, Si, B, N, Al, Zr, Ti, W can be 0 wt .-%.

For example, fibers, in particular high-temperature-resistant fibers, based on Si, C, B, N, Al or compounds thereof (these fibers also being described, for example, in document DE 197 11 829 C1 as "Si / C / B / N fibers". and in particular ceramic fibers based on compounds containing at least two These elements comprise, used. Such fibers are described for example in the document DE 197 1 1 829 C1.

Ceramic fibers may be selected, for example, at least one compound selected from alumina, zirconia, SiNC, SiBNC, SiC, B ₄ C, BN, Si ₃ N _4, TiC, WC, and include mixtures thereof or therefrom completely or at least 90 wt .-%, preferably at least 93 wt .-%, based on the total weight of the fibers consist. In particular, ceramic fibers may be basalt fibers and / or glass fibers or a mixture thereof with other ceramic fibers.

Particularly preferably, the contours are alleys and / or knitting patterns which allow the intended folding. This is done by omitting one or more fiber yarns in the 0 ° direction or by a splitting of the textile by modification of the connecting knitting threads.

Due to the scrim of the invention with alleys, which are introduced in the longitudinal and / or transverse direction, the folding is made possible in the first place, especially in heavy sites. A single fiber layer or unidirectional layer may have a basis weight in a range of, for example, 50 g / m ² to 500 g / m ² , preferably in a range of 150 g / m ² to 2000 g / m ² . Depending on the desired end product, it may be particularly preferable to select one or more fiber layers or unidirectional layers having a surface-related weight of at least 305 g / m ² .

When using carbon fibers and / or their precursor fibers, both fibers which were obtained starting from polyacrylonitrile but also starting from pitch or phenolic resin fibers gave a fiber layer of very good mechanical strength.

The diameter of the filaments of at least one fiber layer or unidirectional layer, preferably all fiber layers or unidirectional layers, may be in a range of, for example, from 6 to 8 μιτι. At least one fiber layer is preferably more than 70% by weight, more preferably more than 87% by weight, particularly preferably more than 98% by weight of fibers selected from carbon fibers, precursor fibers of carbon fibers, Ceramic fibers and mixtures thereof, based on the total weight of the respective fiber layer.

In addition to carbon fibers, their precursor fibers, as well as ceramic fibers, the fiber layers may comprise any fibers that one skilled in the art can select based on his general knowledge and the teachings of the present invention.

The textile structure preferably consists of at least 50% fibers in the main loading direction of the three-dimensional semifinished fiber product to be produced. Preferably, the flat textile structure is coated after working with a matrix system or with multiple matrix systems (liquid / solid) and / or impregnated through.

The content of the matrix system for coating and / or impregnating the flat textile structure is preferably at least 0% to 70%. Preferably, the textile structure includes soluble polymers (e.g., PVA, polyphenoxy).

The textile structure can be improved by applying chemical, physical

(chemical reaction, pressure and / or temperature) and / or mechanical

Solidification methods (sewing, needling) in a three-dimensional

Semi-finished fiber preforms are transformed.

The flat (quasi two-dimensional) textile structure having a basis weight of 100-5000 g / m ² , preferably 500-2300 g / m ² , is obtainable by a process according to one or more of the preceding claims.

The basis weight is preferably locally adapted by reducing or increasing the amount of fiber in the planar (quasi two-dimensional) fiber structure or by a separate process step. The three-dimensional semi-finished fiber product can be infiltrated and cured with thermosetting and / or thermoplastic resins. Fiber scrims with very advantageous properties can be obtained, for example, if at least one fiber layer, in particular a unidirectional layer, preferably all fiber layers, have a number of filaments ranging from 0.5 K (500 filaments) to 500 K (500,000 filaments ) lies. Preferably, the number of filaments of a fiber layer or unidirectional layer in a range of 1 K (1000 filaments) up to 400 K (400 000 filaments), preferably in a range of 12 K (12 000 filaments) up to 60 K (60 000 filaments).

Fiber clays with advantageous material properties and comparatively low production costs can furthermore be obtained if one or more fiber layers, in particular unidirectional layers which comprise polymer fibers, in particular organic polymer fibers, or mixtures thereof, are used. For some applications it may also be advantageous to use polyacrylonitrile-based fibers, viscose-based fibers to make at least one fiber layer. For example, one, two, three or more of the fiber layers may be wholly or at least 80% by weight polyacrylonitrile fibers and / or viscose fibers, based on the total weight of fibers in the fiber layer.

Fiber scrims with different material properties can be obtained by making scrims comprising two, three, four, five, six, seven, eight, or any number of fiber layers and / or unidirectional plies. In order to obtain highly resilient material, it may be advantageous for a unidirectional layer to extend in a different longitudinal direction than the unidirectional layer arranged above and / or below this unidirectional layer. Preferably, all present in a fiber fabric unidirectional layers extend in each case a different longitudinal direction. In this case, it may be advantageous if at least the longitudinal direction of a unidirectional layer is at an angle of at least 30 °, preferably at least 45 °, preferably at least 60 °, in particular. particular 85 - 90 ° to the longitudinal direction of at least one subsequent unidirectional layer forms.

If the unidirectional layers each have mutually different longitudinal directions, biaxial fiber scrims are obtained when using two unidirectional layers, triaxial fiber scrims when using three unidirectional layers, quadraxial fiber scrims when using four unidirectional layers. Preferably, when using two or more unidirectional plies, the two or more further unidirectional plies are arranged such that their respective longitudinal directions to the 0 ° direction form angles of opposite sign, the angle being equal (and the angles being for example + 60 ° / May be -60 ° or + 45 ° / -45 °) or different, or their respective longitudinal directions to the 0 ° direction are at angles of 0 ° and 90 °.

Preferably, a 0/90 layer is produced on a leveling machine, in which at least 90% of the fibers, more preferably 95% of the fibers, are arranged in the 0 ° direction. The width and the fiber basis weight of the invention according to the invention depend on the fiber titer used, the intended layer structure, the resulting number of layers and their width.

It is a surprising advantage of the method according to the invention that the full width of, for example, a fast-running folding machine can be used. This represents, for example, a particular advantage over tape looms.

Resins which are particularly useful for impregnating fiber webs include, for example, phenolic resins, epoxy resins, benzoxazine resins, cyanate ester resins, polyester / inylester resins, furan resins, polyamide resins, polyimide resins, polyacrylate resins, and the like derived derivatives and their mixtures. Inorganic impregnating agents may additionally be used to impregnate the fiber scrim, with liquid silicon, SiC precursor polymers, in particular silazanes, SiC precursor oligomers and mixtures thereof, being particularly suitable for impregnating fibrous webs.

The term "SiC precursor polymer" as used in the present invention describes any compound having a molecular weight greater than about 300 g / mol, which comprises silicon, as well as carbon and / or nitrogen, and for example a content from 10 to 99 wt .-% of Si, based on the total weight of the compound, may have. The term "SiC precursor oligomer" as used in the present invention describes any compound comprising silicon, as well as carbon and / or nitrogen, having at least two silicon atoms and a molecular weight of up to and including about 300 g / mol, and may, for example, have a content of from 10 to 99% by weight of Si, based on the total weight of the compound. Preferably, an SiC precursor polymer or an SiC precursor oligomer when heated to a temperature of greater than 150 ° C under an inert atmosphere at least partially converts to SiC. In the case of an impregnation of fibrous webs, for example, very good results can be obtained if at least one compound selected from the group consisting of oligosilazanes, polysilazanes, oligocarbosilazanes, polycarbosilazanes, oligosilanes, polysilanes, oligoborocarbosilazanes, polyborocarbosilazanes, methyl-oligosiloxanes, Methylpolysiloxanes, oligocarbosilanes, polycarbosilanes, oligoborosilazanes, polyborosilazanes, oligo (dialkyl) silicones, poly (dialkyl) silicones, oligosiloxanes, polysiloxanes, for example poly (dialkyl) siloxanes, such as poly (dimethyl) siloxanes, for example poly (diaryl ) siloxanes, such as poly (di-phenyl) siloxanes, for example poly (monoalkyl-monoaryl) siloxanes, such as poly (monomethyl-monophenyl) siloxanes, their derivatives and mixtures thereof are used. The terms oligosilazanes, oligocarbosilazanes, oligosilanes, oligoborocarbosilazanes, methyl-oligosiloxanes, oligocarbosilanes, oligoborosilazanes, oligo (dialkyl) silicones, oligosiloxanes, etc. include any oligomer falling under the respective term and composed of at least two monomer units means any oligomer, starting from a dimer, to compounds having a molecular weight up to and including about 300 g / mol.

The terms polysilazanes, polycarbosilazanes, polysilanes, polyborocarbosilazanes, methylpolysiloxanes, polycarbosilanes, polyborosilazanes, poly (dialkyl) silicones, polysiloxanes, etc. include any polymer covered by the respective term which has a molecular weight of more than about 300 g / mol having.

A fiber fabric may moreover be impregnated both with inorganic impregnating agents and with resins, preferably synthetic resins. For example, adjacent portions of a fiber fabric may be impregnated with one or more inorganic saturants and / or one or more resins. For example, impregnation in several layers or in a series of impregnations with one or more inorganic impregnating agents and / or with one or more resins can be carried out and / or impregnation can be carried out using mixtures of one or more inorganic impregnating agents and resins , The choice of curing conditions takes into account the requirements of the chosen impregnating agent.

The curing of the impregnated fiber fabric can be carried out in a curing temperature range of at least 40 ° C, at a curing temperature in the range of 50 to 260 ° C, preferably 80 to 200 ° C. The curing may preferably take place before the start and / or at least during a partial period of the curing period under pressure, for example by pressing at least one surface section of at least one surface of the impregnated fiber laminate with a pressing tool. The curing period may, for example, be at least 1 minute, preferably between 10 minutes and 8 hours, preferably between 15 minutes and 3 hours. The period of curing under pressure may, for example, be in a range of at least 1 minute, preferably between 10 minutes and 8 hours, preferably between 15 minutes and 3 hours. The pressing pressure may be, for example, at least 0.01 MPa, preferably 0.01 MPa to 100 MPa. The content of the resin and / or inorganic impregnating agent, based on the total weight of the non-impregnated fiber fabric, may range from 5 to 85% by weight, preferably from 25 to 65% by weight, more preferably from 30 to 45% by weight .-% lie.

The fiber fabric can be soaked, for example, to saturation of the fiber fabric. In particular, liquid resins or molten resins ("hot melt resin"), which may, for example, be phenolic resins, may be used.

Hardening and impregnation may be carried out using any method known to those skilled in the art. Very advantageous results can be obtained if the impregnation is carried out by immersion in a dipping bath or by a film transfer process. For example, these process steps may be performed continuously, that is, the fabric may, for example, be unrolled from a roll, passed through one or more ovens of a suitable temperature and atmosphere, such as 400 ° C or more under an inert atmosphere, and Subsequently, a resin bath and / or a bath with an inorganic impregnating agent, and / or a roller calender and / or another impregnating device can be used. This can be followed by curing, whereby a composite material is obtained, the matrix of which is reinforced by a fiber layer, for example a carbon fiber layer. The curing step can be carried out either continuously or discontinuously. The cured resin and / or cured inorganic saturant performs several functions in the post-cured composite material. First, the resin makes connections between the ropes and threads of the fiber fabric and fixes their position in the fabric. Depending on the use of composite material, the fiber fabric may be completely or partially embedded in a matrix comprising a cured resin and / or inorganic impregnating agent, and / or completely or partially coated with a film of resin and / or inorganic impregnating agent covering only individual fibers, and / or partially free of resin. The cured binder also causes a mechanical reinforcement of the fiber fabric. After curing and / or pressing, a fiber-laid reinforced composite or a fiber-laid reinforced composite product may be obtained.

In the context of the present application, a fiberglass-reinforced composite product is a partially or preferably completely cured fiber-laid reinforced composite material which has optionally been subjected to further processing steps, for example to cutting, to an exciting shaping, etc. In the context of the present application, a hardened fiber-laid reinforced composite material is also referred to as a green body.

Optionally, the partially or fully cured fiber scrim reinforced composite, even without an intervening step of recovery, or the partially or fully cured fiber scrim reinforced composite product may be subjected to further process steps, such as i.a. a thermal treatment, for example, for carbonization or graphitization, or be subjected to a further heating and / or pressing.

A thermal treatment can be carried out in a first temperature range (frequently also referred to as "carbonization") and can be, for example, by heating to the exclusion of oxidizing substances, ie either under an inert atmosphere, inert gas or under wrapping the material to be fired with a getter acting, the oxidizing media, especially oxygen scavenger at a temperature or in a temperature range in the range of about 800 ° C to about 1250 ° C, preferably from 850 ° C to 950 ° C, especially from 880 ° C to 920 ° C. , respectively. The thermal treatment in the first temperature range can take place during a period of, for example, at least 30 minutes, preferably at least 8 hours, in particular from 30 minutes to 96 hours. For thermal treatment in a first temperature range ("carbonization"), within the scope of the teaching of the present invention, any method known to a person skilled in the art can be used, for example a solid phase pyrolysis. In order to achieve a good coke yield, a heating phase, for example with a comparatively low temperature gradient in the range from 300 to 600 ° C. of not more than 4 ° C. per hour, can be carried out beforehand or it can be coked under pressure. The final temperature in this process step can not exceed 1250 ° C, for example.

The thermal treatment in a first temperature range may be subjected to both a fully cured and partially cured fiber scrim reinforced composite.

After thermal treatment in the first temperature range, a composite is obtained whose matrix comprises carbon and is reinforced with a carbon fiber fabric ("carbon fiber reinforced carbon", CFC).

As an alternative to the thermal treatment in the first temperature range or in addition to this, in particular according to this, a thermal treatment in a second temperature range (often referred to as "graphitization") can take place. The thermal treatment in a second temperature range ("graphitization") can be carried out by any method known to a person skilled in the art. In particular, heating in an inert atmosphere at a temperature in the range of about 1251 ° C to 3000 ° C, preferably 1800 ° C to 2200 ° C for a period of, for example, at least about 30 minutes, preferably at least 8 hours, especially 30 minutes to 96 hours.

In a thermal treatment in the first and / or second temperature range, the resin layer shrinks due to the weight loss due to the elimination of volatile components. The composite material obtained after the thermal treatment is characterized by a high temperature resistance.

After thermally treating the scrim reinforced composite or composite product, a thermally treated fiber scrim reinforced composite or composite product may be obtained. Optionally, the composite material obtained after one or more thermal treatments in a first and / or second temperature range, in particular a composite material comprising carbon fiber reinforced carbon, may additionally be subjected once or more times to a post-treatment, in particular a post-compaction, in which the composite material is at least once impregnated, in particular impregnated with a carbonizable agent, and / or at least once again a thermal treatment in a first and / or second temperature range (which is also commonly referred to as Nachbrand) is subjected. The densification, in particular the steps of impregnation and thermal treatment, can in principle be carried out within the scope of the teaching of the present invention by any method known to a person skilled in the art. The term post-densification as used in the present invention refers to any treatment of a material or workpiece that results in maintaining or increasing the density of the treated material or workpiece. Advantageously, an increase in density can be achieved by such a post-treatment aftertreatment. The impregnation and the thermal treatment can be carried out particularly advantageously under the conditions explained above and below. For impregnation, for example, the so-called vacuum pressure method can be used.

As the impregnating agent, all known for an impregnation of parts which comprise carbon or consist thereof, known substances, for example substances with a coke yield of more than 30 weight percent, for example synthetic resins, in particular thermosetting resins or pitches and derivatives derived therefrom, and mixtures of resins and pitches and / or pitch derivatives. In particular, phenolic resins of the novolac or resol type, furan resins or impregnating pitches may find use. A thermal treatment in a first and / or second temperature range, as defined above, after the impregnation, the so-called afterburning, takes place with the exclusion of oxidizing substances, in particular under an inert atmosphere.

Before and / or after the thermal treatment in a first and / or second temperature range, a heating or cooling, for example, 8 to 10 hours, for example, to room temperature (20 ° C), take place. Exemplary and preferred time periods and temperature ranges for a thermal treatment in a first and / or second temperature range are explained in detail above. In this process step, one or more additional carbon casings should be applied to the already existing casing, and cracks remaining in the first casing should be present after the first carbonization step and pores are closed. Depending on the intended protective effect for the fibers, this impregnation and afterburning process can also be repeated several times,

preferably 1 to 3 times. Application specific may be advantageous for optimization of the composite, a thermal treatment in a first temperature range, in which a carbonization can take place, nor a thermal treatment in a second temperature range under an inert atmosphere, in which a graphitization can be done nachzuschalten. The implementation of such a measure is only optional. In most cases, the final temperature 3000 ° C, especially 2400 ° C during graphitization is not exceeded. Preferably, work is carried out at temperatures of 1800 to 2200 ° C. All known graphitization methods can be used for this step. The post-compaction described above, which initially comprises impregnation and then firing, can be repeated one or more times.

The number of densifications to be carried out depends on the desired target density of the carbon fiber reinforced carbon ceramic, and may be carried out one or more times, for example two, three or four times or more, preferably in an immediately successive manner. Preferably, the steps of impregnation and subsequent firing are each carried out three times. After densification, for example, densities of 1, 30 - 1, 60 g / cm ³ , preferably from 1, 30 - 1, 55 g / cm ³ can be achieved.

Furthermore, the composite material obtained after one or more thermal treatments and / or additionally densified as described above, fiberglass-reinforced carbon can also optionally have a gas phase coating by the CVD method (CVD = Chemical Vapor Deposition) or by the CVI method. Process (CVI = Chemical Vapor Infiltration) with protective layers of high-melting substances such as pyrocarbon, TiC, TiN or SiC are provided. Any CVD / CVI method known to a person skilled in the art can be used in the context of the present invention. CVD / CVI methods are used For example, in the document DE 39 33 039 A1 or in the publication E. Fitzer et. al., Chemie-Ingenieur-Technik 57, No. 9, pp. 737-746 (1985).

In addition, the composite material comprising a carbon fiber-reinforced carbon comprising, after a thermal treatment in a first and / or second temperature range and / or additionally densified as described above and / or additionally coated by the CVD method or by the CVI method, may optionally comprise a composite material Be subjected to silicization. Such a method is described for example in the publication E. Fitzer et. al., Chemie-Ingenieur-Technik 57, No. 9, pp. 737-746 (1985).

In the context of the present invention, siliciding can be carried out in accordance with any method known to a person skilled in the art. Particularly high quality composites can be obtained, for example, when the siliciding is carried out in the temperature range of 1450 ° C to 2200 ° C, preferably in the temperature range of 1650 ° C to 1750 ° C under an inert atmosphere. In particular, it is possible to work in the temperature range from 1650 ° C. to 1750 ° C. under reduced pressure. After reaching the siliciding temperature, the time for infiltrating and reacting for SiC may be at least 10 minutes, for example 10 minutes to 1 hour.

In the case of siliciding without the use of vacuum can be silicided in particular at temperatures of 2100 ° C to 2200 ° C under an inert atmosphere. The sum of infiltration and reaction time can also be at least 10 minutes, for example between 10 minutes and one hour, in the case of siliconizing without the use of a vacuum.

Advantageously, the above-described silicates can be carried out using the so-called wicking technique. Here are the bodies to be siliconized on porous, based on the silicon very absorbent carbon bodies, the lower part is in liquid silicon. The silicon then rises through these wick bodies into the bodies to be silicided, without the latter having direct connection to the silicon bath. The above-explained steps of the post-compression, in particular by impregnation and optional, subsequent thermal treatment in a first and / or second temperature range, the siliciding and the gas phase coating can each be repeated one or more times and combined with one another in any desired order.

Particularly high quality composites can be obtained, for example, if, after the step of curing and optionally pressing the impregnated fiber fabric and a thermal treatment in the first temperature range at which carbonation can take place, the above-described steps of impregnation and thermal treatment in a first and / or second temperature range, can be achieved by the re-densification, at least once, preferably one to three times, preferably three times. Optionally, then, in addition, a siliconization or a gas phase coating or a siliconization followed by a gas phase coating can be carried out. The gas phase coating may in particular be carried out with mixtures comprising carbon or carbon, by means of a CVD or CVI method, as described above.

Preferably, the three-dimensional semifinished fiber product is due to the low

Weight that provides high flexibility and resilience for leaf springs or profiles (e.g., T-profiles or stringers) for the aerospace, automotive, wind energy and sporting goods industries.

The textile structure is preferably already adapted or processed in the planar (quasi two-dimensional) textile structure for shaping the three-dimensional semifinished fiber product close to its final contour (for example, contouring or recesses).

Claims

Claims 1. Method for producing a 3D textile structure with contours matched to the 3D textile structure by folding a 2D textile structure.

2. The method according to claim 1, characterized in that the contours are alleys and / or knitting patterns.

3. The method according to one or more of the preceding claims, characterized in that the folding is accordion-like.

4. The method according to one or more of the preceding claims, character- ized in that the 2D textile structure having folding supporting gaps, which facilitate the construction of semi-finished fiber to the near-net shape.

5. The method according to one or more of the preceding claims, characterized in that the 2D textile structure from the group of scrim, tissue, braids, knits, felts, nonwovens, combinations of the like and other planar structures.

6. The method according to one or more of the preceding claims, characterized in that the 2D textile structure consists of glass fibers, carbon fibers, arabid fibers, ceramic fibers, other polymer fibers, metallic fibers or mixtures of the aforementioned fibers.

7. The method according to one or more of the preceding claims, wherein

at least one fiber layer to more than 70 wt .-%, preferably more than 87 wt .-%, more preferably more than 98 wt .-% consists of fibers selected from carbon fibers, precursor fibers of carbon fibers, ceramic fibers and mixtures thereof , based on the total weight of the respective fiber layer.

8. The method according to one or more of the preceding claims, wherein the textile structure consists of at least 50% of the fibers in the main loading direction of the produced three-dimensional semi-finished fiber product.

9. The method according to one or more of the preceding claims, wherein the textile structure is coated with a matrix system or with a plurality of matrix systems and / or by impregnated.

10.A method according to claim 9, wherein the content of the matrix system for coating and / or Durchimprägnierung the flat textile structure is at least 0% to 70%.

11. The method according to one or more of the preceding claims, wherein the textile structure includes soluble polymers.

12. The method according to one or more of the preceding claims, wherein the textile structure can be transformed by applying chemical, physical and / or mechanical solidification methods in a three-dimensional semi-finished fiber product.

13.3D textile structure having a weight per unit area of 100-5000 g / m ^2, preferably 500 2300 g / m ^2, obtainable by a process according to one or more of the preceding claims.

14.3D textile structure according to claim 13, wherein the basis weight is locally adjusted by reducing or increasing the amount of fiber in the sheet-like fiber structure or by a separate process step.

15. A three-dimensional semifinished fiber product, which is infiltrated with thermosetting and / or thermoplastic resins and cured, prepared by a process according to one or more of claims 1 to 12.

16. Three-dimensional semi-finished fiber product according to claim 15 for the production of leaf springs or profiles for the field of aerospace, for the automotive sector, for wind energy and sporting goods.

17.3D textile structure according to one or more of claims 13 or 14, wherein this is already adapted to the near-net shape design of the three-dimensional semi-finished fiber product in the flat textile structure.