DE2722575A1 - COAL-CHARCOAL COMPOSITE - Google Patents

Description

DIP. Heinz Bardehl 4 Patent attorney

IMKbO 22, Hsmtfr. Κ, ΤΛ 292551 paHntsthHt MCucten 2έ, Fostfacti 4

My reference: P 2507 Munich, the H · Mal ß77

Applicant: Morganite Modmor Ltd.

11 Battersea Church Road
London SW11 3LZ
England

Coal-coal composite

The invention relates to a carbon-carbon composite. She concerns especially the manufacture of carbon-carbon composites for aerospace or general applications, especially if high mechanical strength and good thermal conductivity along with low density are required. examples for this are Missile propulsion nozzles and applications in civil and military supersonic aircraft.

Composites in which carbon and graphite fibers form a carbon matrix reinforce are known and established. The fibers can be randomly distributed or incorporated in an orderly fashion to produce the desired mechanical properties, namely usually high bending

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strength and modulus and high heavy strength, and the carbon matrix can be achieved by vapor deposition, through use a carbonizable material with which a fiber structure is impregnated, or a combination of these two processes getting produced.

A particular area of application for coal-coal composites is the manufacture of high-performance brake discs for aircraft. It has been proposed to cut such slices from a stack of Manufacture layers of woven carbon fiber cloth; however, delamination difficulties arose during manufacture and weak areas in the finished composite, so that the theoretically obtainable strength and shear values not reached v / earth. There is also both the conversion of the fibers into the fabric and the cutting of the slices from the fabric associated with a large waste of material, being 50% or more get lost.

The problems of insufficient strength that arise only after the completion of the process of preparing the carbon matrix, which Several hundred hours can take to become visible, even when steps were taken to make them visible to bind or consolidate the stack of layers, e.g. by pre-oxidized but not carbonized polyacrylonitrile or uses a different precursor and presses the stack at an elevated temperature before or during carbonation.

It is believed that small deformations of the fabric or fabric structure therein can cause voids in the finished composite with a consequent loss of strength. Without wishing to limit the invention to theory, the aim of the invention is to reduce the possible occurrence of these voids by improving the uniformity and uniformity of the pore structure in the material and the size of the voids that are formed

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continuous carbon fiber filling is reduced.

In the manufacture of composites, the main role of the fiber is to act as a base on which carbon deposited by vapor deposition can grow, with the desired mechanical properties theoretically being obtained from the deposited carbon itself. The main problem is therefore to present the fiber in such a way that gaps and
Cavities are avoided that are larger than that they could easily be bridged by the deposited carbon. For example, when vapor is deposited in fabric, carbon is easily formed within a multi-filament yarn; however, the gaps between the yarns sometimes seem too wide for the charcoal to easily bridge them to give a fully coherent structure.

In order to overcome these difficulties it has been proposed to give the structure a better cohesion by needling, sewing or quilting, but these makeshift measures make the
Increased difficulty of the procedure. The applicant therefore takes the view that an improved basic access
is necessary to avoid the presence of gaps right from the start and also to avoid the sensitive material losses,
which occur when using fabric.

According to the invention, therefore, a body of carbon fibers is used in the production of a carbon-carbon composite, which by
repeated (stacking) lengths of a substantially parallel-aligned multifiber array of carbon fibers or a precursor, the invention extending to the process, the laid-up bodies and the finished composites.

The invention therefore relates to a coal-coal composite,

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which is characterized by the penetration or drawing in of carbon into a fiber body, which is caused by repeated laying one on top of the other of lengths of a multi-fiber arrangement of carbon fibers or carbon fiber precursors aligned essentially in parallel is constructed.

According to one embodiment of the invention, the carbon fiber or its precursor is in the form of cohesive arrays of staple fiber; Examples of such a manifestation of the ^Fa ~

(topi
Or worsted yarn / roving or roving and winding (batt) These are easily laid on, as described below, and give end products, e.g. brake disks, with excellent properties. The placement can take place in a surface or, if necessary, around a center point.

However, the applicant has also found that these are different Staple fiber material, while producing excellent results, retains an unnecessary difficulty, namely breaking the continuous filament to form staple strips (sliver) and converting them into laps or slivers and then into the roving. It has now been found that notwithstanding the difficulties encountered in the application of short Lengths of this material occur, use a cable with parallel filaments and also used advantageously will. According to a preferred embodiment of the invention, therefore, a fiber body is used which consists of layers is constructed from cut parallel lengths of cable, each length being in a given layer itself extends across the body and is adjacent to adjacent lengths in the layer. Such layers are on top of each other, where the relative orientation is determined by the mechanical properties required in the finished body or composite; in the case of a brake disc, for example, these are uniform

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To give strength in all radial directions.

A body of this type can be applied by a method in which successive cable lengths from a supply via a receiving board or plate are pulled and cut off after or while they are being applied; the Laying the lengths of cable across the panel or panel between one length and the next is determined by the width of a single one laid down / occupied is divided, and the relative orientation of successive layers is determined by relative rotational division of the layer direction and the growing cable body as required, determined.

A machine particularly suitable for this purpose is described in detail in British patent application filed with a provisional description on May 18, 1977 by Morganite Modmor Ltd. being submitted, being Richard Martin Phillips Ludlow, Donald Robert Lovell, James Stephen Bailey and Sidney Parnell Morris are named as the inventor.

The proposed method is independent of the form of representation The fiber easily achieves sufficient intermixing of the fibers to produce uniform strength without levels of inferior strength to obtain. This can be supported, for example, by pressing the body in its construction. You get a desired one Increase in the amount of fiber per unit volume without the benefits of a systematic, predetermined orientation of the fibers in abandon the composite. So can composites with excellent mechanical properties can be obtained.

The most suitable carbon fiber precursor is polyacrylonitrile, however, others such as rayon can be used. Polyacrylic is first applied by methods known per se, e.g. for 0.5 to 5 hours at 200 to 300 ° C, OKydiert (i.e. subjected to the action of molecular oxygen) and gives a material that can be used as such or

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alternatively, it is first carbonized or graphitized. Such an oxidized material, advantageously for example 1.5 den is strong and has a specific density of 1.30 to 1.40 g / cm possesses, can be applied to form a fiber body, optionally at elevated temperature to form a coherent one Molded, then carbonized and, if necessary, graphitized before the cohesive carbon fiber through Feeding is established.

By pressing, in which the residual plasticity of the oxidized fiber is used, the fibers stick to each other, what enough to keep the body in cohesive shape for the following steps. The compression grows out of the residual thermoplasticity of the oxidized polymer, which enables the fibers to adhere to one another and the retain the shape imposed by compression; it takes place at a temperature sufficient to achieve this thermoplasticity to use. Suitable temperatures below those at which volatiles are released can easily be achieved can be determined in the experiment.

However, as has already been stated, the fiber can already be laid in carbonized or, if desired, graphitized form will. The following is the manufacture and use of the various Forms of staple fibers discussed. The manufacture of the staple fibers themselves from a continuous filament Polyacrylonitrile or another precursor such as rayon is known to v / ohl. Particularly suitable staple fiber is after The applicant's method, which is described in GB patent application 35903/75 (corresponding to DT-OS 26 39 409), is produced. Of the The content of these patent applications is hereby made the subject of the present description.

So a top thread (top) can be made by connecting a cable from precursor material, e.g. polyacrylonitrile fiber, takes, oxidizes, curls, pulls until the fibers break and then the manufactured

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Staple fiber over a system of rollers and other spreading devices, as they are common in textile machines, combs and pulls around a top yarn of substantially more aligned Fiber. The procedure involves pulling and repeatedly disintegrating until a body with substantially aligned fibers of uniform thickness is obtained. A regular body of interrupted loosely arranged, but largely parallel Fibers can thus be obtained, the width and thickness of which depends on the precise process conditions. So can a top thread (top) can then be converted into a roving if necessary. Rovings are particularly suitable for the intended purpose of the invention, as they are usually made ready to be twisted into yarn have a highly oriented structure and a substantially uniform weight per unit length and are free from lint and other debris. Their structure allows easy laying by folding and with the finished body, especially when it is pressed, the staple fiber gives good intermixing of the fibers.

The way in which the top yarn or roving is laid to form a Fiber body depends on the orientation of the fibers required in the particular component that the composite is made of should form. One suitable method is to use a feed head from which the top yarn is deposited and a Table on which the upper twine body is built, with relative reciprocating movements between the table and the head take place, so that the upper thread is constantly laid across and is built up increasingly to the required thickness. If the The composite obtained as a product must be radially uniform, such as in a brake disc, the table and the head can are rotated relatively at intervals so that the direction of the fiber layers is randomly distributed.

Usually the head goes back and forth and the table is rotated as necessary, and suitable folding machines adapted to the purpose

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can be adapted to the invention are known as such. You place material vertically through a suitable and outgoing device that makes the body of upper yarn uniform distributed in ascending layers, with the length of the reciprocating trains is adjusted so that it is adapted to the dimensions of the body to be produced.

It is beneficial to add each individual or a specific one Number of layers on the table and especially with oxidized polyacrylonitrile, at elevated temperature means a plate or roller heated to a suitable temperature and applied to the surface of the body, is pressed, as mentioned above, so that the fibers stick to each other and increasingly form a compact body. If If necessary, a heating medium, e.g. superheated steam, can be passed through.

If the relative positions of the folder and the head and table need to be changed, the top thread will be intermittent held to avoid confusion of the body already made and the table moved to an appropriate angle; the angle of advancement and the number of layers applied in any orientation is determined so that the finished end product possesses the desired radial properties. A suitable number of layers in a brake disc is, for example, 70 to 80, but there are no restrictions on these Counting.

Example 1 :

In a particular example, lengths of top yarn (top) weighing 23.5 g / m, made from a multi-filament cable _{made of} oxidized polyacrylonitrile of 1.5 denier, were spread out and laid side by side over a square plate 12.7 cm on a side by running them over a support bar that crossed the plate. In the end everyone

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crossing the layer of upper yarn was fastened by one pressed a plate on it and then the plate with the press plate was rotated 15 ° clockwise.

A body was built up from 24 layers, each offset by 15 ° from the adjacent layer. Upon completion, the body was pressed at 180 ° C under 5.6 kg / cm ² (80 psi) pressure to give a coherent easy-to-use body 2.54 cm thick, a volume fraction of carbon fiber 0.36 and weight 144 g .

This body was carbonized and steam deposited coal was stored in it in a known manner; he pointed excellent Properties on. The following example is an alternative lay-up method in which the fiber is laid by guiding is done around an array of pins rather than using a folding head, which is particularly suitable for top yarn.

Example 2 :

In one example, a length of roving with a weight of 1.69 g / m, made from multi-filament cables of oxidized polyacrylonitrile at 1.5 ^{denier per filament by successive crimping,} breaking and other steps already described, is placed side by side on a square board of 12 , 7 cm edge length, which it spans repeatedly in different directions with the help of guide pins that are placed around the edge of the board. Successive layers were laid as follows:

a) a layer of parallel strands,

b) one layer offset by 60 ° to layer a),

c) one layer offset by 60 ° to layer a), but in the opposite direction to layer b),

d) another layer like b),

e) another layer like c),

f) another layer like a).

The 6 layers were then pressed at 180 ° C under about 5.6 kg / cn ² (80 psi) for 20 minutes and gave a continuous,

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compact body of ο, 51 cm thick with a fiber volume of 38%. The compact body was stiff and easy to handle, and very useful for the next steps in making a carbon-carbon composite suitable as an end product.

Instead of top yarn or roving, lengths made from a lap of staple fibers can be used. Preferably the coil has the same width as the finished composite, which / possible weak points where the lengths adjoin, turns off. While the winding comes in certain lengths and therefore waste is created, as is the case with tissue, the structure of the However, the lap is very open and loose and such waste can easily be returned without loss of fiber.

The production of laps is in itself in textile technology, e.g. in felt production, where laps up to a width of 1.83 m are known.

For example, a coil suitable for the purposes of the invention can be made are oxidized and crimped by taking a polyacrylonitrile precursor cable, stretching until the fibers break and so makes staple fibers and then places the staple fibers side by side on a crimping bench and roughening them until they are uniform are. A lap consisting of a body of discontinuously loosely arranged but largely parallel fibers can thus be obtained. Its width and thickness depend on the processing conditions and it is essentially when viewed on a viewing screen uniformly. The way in which the winding lengths are applied to form a fiber body depends on the fiber orientation in the specific component is needed that the composite is to form. As before, you can use a table on which a bobbin can be conveniently set up and pressed if necessary. The pressing can be done e.g. with a plate or a roller Geschechen, which is heated to a suitable temperature and applied to the surface of the body to make the fibers

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to settle into each other and progressively to form a compact body. If necessary, a heating medium, e.g. superheated steam.

The pressing of the laid layers in combination with the intermingling of the fibers when the roll is laid gives a Structure that can be easily handled in subsequent processing stages without delamination of the layers.

Above was the laying on of top yarn, roving or winding in planar form Arrangements described. The repetitive superimposing mentioned above in the broad sense according to the invention is, but can also be done by laying or winding around a center point, so that the fiber body is built up radially. In this way top yarn and roving can be used, and even laps if a particularly wide end body is required will. Furthermore, continuous filament tows of any desired number of filaments, such as 10,000 or 20,000, can be used will. The winding can be done by laying concentric rings or by continuous winding, if the superimposed lengths are successive portions of a continuous length of the particular fiber state form.

During the winding procedure with staple fibers, preferably in particular roving for the previously stated reasons, and when winding ^Ka ~ at, the dimension, particularly the width of the strand of face yarn, roving or cable _{of the D ± blocks} correspond _directly to _{the desired} body or two or more strands can be laid side by side if desired.

In the process, sufficient intermixing of the fibers is easily achieved in order to achieve uniform strength in the end product without To achieve areas of lower strength; however, initially has a disc or other body of roving or top yarn less cohesion between adjacent strands than within

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of strands and therefore may have been referred to as a compact body of the first stage. Convenience becomes a body coiled ', although it has even less cohesion.

A structure with complete cohesion, i.e. a compact one Second stage body, suitable for handling in the course of manufacture and in particular for the formation of the carbon matrix If the first stage compact body is not held in a jig, further steps are desirable shall be.

The compact body of the first stage, if it consists of oxidized polyacrylonitrile, can accordingly, for example, be pressed, as already discussed. For example, when a disc made on a spool with umgezogenem edge, the edges can be pressed together, whereby the heat can be supplied by, for example, conductivity, or _by passing superheated steam.

On the other hand, the structure can be made with cohesion and the strength in the radial direction can be improved by Carbon fiber or oxidized precursor fiber passes between adjacent strands, preferably with prior compression of the body. For example, in the case of a disc with a center hole, the fiber can be from the outer circumference or the inner circumference or both are fed to produce a radial fiber structure parallel to the flat surfaces of the disc, the whole can be achieved easily and precisely by means of suitable switching devices.

The fiber can be positively applied by stitching with continuous fiber or staple fiber, or alternatively that can Structures can also be needled without inserted fibers, with the needling process the fibers of adjacent strands through subsequent strands Strands are pulled and left in this position.

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-> 7? 2575

In the case of a body of wound upper yarn or roving, the additional paser can be either a continuous or intermittent winding of tow made of continuous filaments be.

If the carbonization is followed by the laying on of a wound structure, especially if fibers made of continuous filaments are present, the contraction causes the Fibers a consolidation of the structure in addition to a consolidation that may have been achieved beforehand by pressing. If e.g. If a brake disc is produced on a central mandrel, the contraction of the fibers creates a radial consolidation of the structure when the fibers shrink circumferentially. Furthermore, the fibers are kept under tension to some extent during carbonization, thereby increasing their ultimate strength is improved.

Example 3 · An example of a part that is below

Using the present aspect of the invention is a brake disc of 50.8 cm (22 inches) outer diameter, I ¹ 1.2 cm (6 inches) inner diameter, and 2.3 cm (0.9 inch) thickness. It is made from several rovings that are wound up into a blank of such a size that the necessary skimming between the infiltration or drawing-in stages and the reworking to the final size are possible. The fiber from which the roving comes is made from staple fiber, which has no more than 10 % of the fibers less than 3 cm in length and most of them about 10 cm in length, and even from an oxidized polyacrylonitrile fiber of 1.5 denier and the specific Density 1.3o to 1.4o g / cm ^{5 is} made.

The following is the description of the use of cut Cable lengths given to give details of this particularly advantageous aspect of the invention.

The cable is preferably provided with sufficient power before it is applied Water or other liquid moistened to remove the fibers of the

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- 14 -

bels to hold together. It is beneficial if the liquid to Cable is metered in a predetermined amount per unit length while it is withdrawn from the supply, and then can penetrate the cable. Preferably, the wetted cable 30 is also shaped to have a cross-section which enables successive lengths to lie close to one another when laying, and thus the possibility of gaps between the cables in the finished body. There are several suitable shapes. The applicant has z. B. with Lenticular cross-sections worked, some of which were superimposed when placed on top of each other. Trapezoidal cross-sections are preferred because they can lie on top of one another without gaps and allow the fibers to be mixed during pressing. Advantageously, the trapezoids "lean" in opposite directions in alternating layers so that there are no resulting layers Movement to one side or the other occurs when the Body is pressed.

The liquid is advantageously water, but a more volatile liquid can or may be used if desired alternatively, a solution of an adhesive that holds the body of cables together for the subsequent processing steps and, if necessary, for the final carbon binding of the Composite can contribute. Examples of such adhesives are starch, polyvinyl alcohol, phenol, furan or other carbonizable resins or various types of pitch. The application of the resin can e.g. B. in a 3 to Io {igen addition, based on the Fiber weight, made; other adhesives can be used which will volatilize when carbon begins to form.

Specific examples of such procedures follow, with the first example containing general information that also applies to the refer to other examples.

Example 4;

An endless filamentary cable made of oxidized polyacrylonitrile was obtained used, which was slightly moistened by spraying with water.

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The amount of water applied can vary according to the quality of the i of the dry cable: when the dry cable, already has a certain degree of bonding between the filaments, e.g. due to a suitable dimension that keeps it from separating, is the amount of added · ■ required Water as little as possible and can be zero. For a tow that will easily flake, enough water must be added to hold the filaments together. ]

The wetted fiber, held slightly under tension {'» _; and the total length used was measured, was then repeatedly drawn over a receiving plate, with one-; , other successive lengths were cut off after being drawn out and the laying of the lengths was regularly stopped across the plate so that successive lengths lay against one another. It can be achieved that successive tows are placed side by side without a gap wider than a few filaments diameter, but also without overlapping. Alternatively, a careful overlap can be created using a selected amount. In the present case, the cables were laid with a slight overlap so that the lenticular shapes fit into one another and formed a layer of as uniform a thickness as possible.

When a complete layer of cables was laid down, the plate was rotated a predetermined angle. The laying began then again, the lateral displacement being in the opposite direction.

A circular body about 22.2 cm (8 3/4 ") outside diameter was made with successive layers relative to the first layer deposited at 90 °, 35 ° and 0 ° were directed.

Example 5 :

A second piece was prepared by additionally a rectangular hole of approximately 6.5 cm at the center of ¹ J

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the disc was formed. The ability to make such holes and outlines of very different shapes without considerable Generating fiber waste neither during lay-up nor during finishing is an essential characteristic of this aspect the invention.

In Examples 4 and 5, the fiber was in a 1.5 denier fiber tow of 20,000 filaments with a fiber density of 1.35 g / cm and a tow weight of 3.49 g / m (which is the weight of 9,000 m of a single filament in grams). In example 4 were 20 layers with 7.3 m of cable per layer and 35 lengths laid in each layer, with the final weight of the body about 500 g fraud. The final thickness was after compressing the laid body by 2o% 2.54 cm and the fiber volume fraction o.37. The body of Example 3 was very similar, but the amount used was Cable a little higher because of the lack of a hole.

Example 6 ;

A body was, as described in Example 5, but with 13 Layers containing 6.55 m of cable per layer were built. That Weight was 285.8 g and the fiber volume fraction at 2.54 cm thickness without pressing after laying was 0.217.

Example 7 :

A body was built up as in Example 5, but with 18 layers containing 6.63 m of cable per layer. The directions between the layers were 30 °, 60 °, 90 °, 120 °, etc. The final weight of the body was 421 g; he was compressed and surrendered a fiber volume fraction of 0.31 at 2.54 cm thickness.

All of the above bodies were great for carbonizing the fiber and subsequent carbon penetration using known methods Production of blanks suitable for aircraft brake discs.

For all bodies, as described above, either made of staple fiber or cables had been laid, there were steps between laying the body and, if necessary, pressing on the one hand and the final processing of the finished, coal drawn-in blank

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■ -S--

on the other hand in carbonizing and optionally graphitizing the fiber and subsequent drawing in of the continuous Coal phase according to methods known per se. The carbonization can e.g. at 1,000 to 1,600 ° C and the graphitization at 2,000 to 3,000 ° C. The steam application of coal or the impregnation with carbonizable material or a combination of these two methods can be used.

If the applied fiber was pressed, this yielded together with the mixing of the fibers in laying a structure Jer neither a Ablösuny b _e i <handling in subsequent process steps, still leads to a failure in operation. However, if necessary, the laid-up fiber can be supplemented with particulate coals or parallel or randomly distributed appearances of fibers, including chopped fiber, which are incorporated into the body as the laying progresses. Their presence also reduces the possibility of voids remaining after carbon impregnation by increasing the number of bridging points between the fibers. However, the structural advantages gained from the systematic alignment of the fibers in the body remain intact.

It is also possible that the laid body, if for special Purposes necessary, can be modified by using either positive continuous fiber or staple yarn by stitching to ensure that adjacent layers are more firmly bonded together, or by compacting the layers Needles structure without any inserted fiber, the fibers of adjacent layers being drawn or pressed into one another will. Such methods have already been described in connection with wound bodies, where stapling or needling is advantageous occurs radially, but the principle is the same.

It is also possible to use a carbon fiber when placing the body on

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Add a resin binder or other adhesive , with the results described in particular in connection with bodies from laid rope lengths.

If desired, continuous lengths of fiber or staple yarn can be laid in a body that is in one plane is being built. E.g. a brake disc may contain spirals of continuous fiber laid at intervals in the body, to give the disc as a whole a strengthening of the ring strength after completion and also the compression of the structure during the carbonization of the preferred starting material, which, as already found that polyacrylonitrile is in an oxidized form. To achieve this, the midsection of the body is laid on when it was made without a hole, cut out and attached the whole thing over a mandrel between holding plates. The contraction The spiral of continuous fiber during carbonization gives a radial consolidation of the structure as the strands shrink in the circumferential direction. Furthermore, the so-inserted Fiber is held under tension at least to some extent by the shrinkage stress during carbonization and This increases their final strength.

Another, separate approach to the difficulties that arise with Fabric composites found are discussed below.

In addition to needling and basting to improve cohesion such composites, as noted, were suggested in U.S. Patent 3,991,248 prior to construction of the composites to build a pile on carbon fiber cloth or to roughen it.

It has now been found that in spite of the partial filling of the gaps in the cloth structure by the fibers of the pile, the composite materials still cannot be reliably manufactured. Because in some areas a bond to the tissue process

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research has now been carried out to improve it; It has been found that it is crucial to use the pile on fabric of precursor fiber and not carbon fiber as to erect such.

The invention accordingly relates to a carbon-carbon composite made of superimposed layers of fabric made of oxidized polyacrylonitrile or other carbon fiber precursors, which was formed into a coherent body, carbonized and in which coal was subsequently stored, in which the Layers before laying had a pile on one or both sides, around the areas between the layers and in the fabric structure to fill.

Roughening the pile on precursor fabrics ensures important advantages both in building the pile and in formation the compacted body from the tissue. It is desirable to have long staple fiber in the fabric, e.g., 4 cm to 6 cm staple use and pull a long pile of e.g. 1 to 3 cm. The fiber in carbonized fabric is far too brittle to be that such a pile could be drawn. If the weft side of a precursor fabric with a satin weave, e.g. an eight-thread

Köpers, placed in a suitable device, as sxe is well known in the textile field, can be an essential Proportion of staple fiber in which weft yarn is drawn from the body of the weft yarn parallel to the warp. The area takes on a smooth felt-like appearance (although the fibers of the pile are not matted) and the fabric structure of the Cloth is completely covered. Such a pile is known as a plush pile (shag nap).

When such a fabric is laid on, a pressure at elevated temperature can be applied at intervals or on the finished stack to keep the fibers of the pile tightly in the spaces

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to bring the fabric structure of the cloth to condense the body and to him by the fibers that are stuck in it. To give cohesion and that achieved by the compaction To make shape permanent.

It can be placed on a surface or around an axis, by winding a tape continuously or in separate lengths.

The most suitable precursor accessible for pressing is polyacrylonitrile in an oxidized, but not carbonized, form Shape, but other fabrics such as rayon can also be used.

The initially established pile can be "blown" in accordance with a preferred feature of the invention, i.e. in a known manner treated with steam and pressure, which solidifies the pile. It. it is therefore desirable that the pile length of the pile be so is that the fibers that make it up can be oriented in a direction passing through that for the final composite required mechanical properties are determined before the Tissue is used. The pile can be created by compressed air or steam nozzles or mechanically, e.g. by brushing.

In the manufacture of carbon-carbon composites, it is preferred to use a woven cloth which has a relatively flat surface. This is preferably achieved by using a satin fabric . When a pile is built on a cloth with such a weave, it is mainly built on the warps on one side and on the wefts on the other side. When the pile is erected by a continuous process on a cloth roll, the pile on the warp surface on which the process acts along the length of the yarn is shorter than a pile on the weft surface where the process acts across the yarn. Preferably the pile is in

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aligned with the general direction of the chain to avoid interference during reeling for storage.

The pile can then be realigned when the cloth is cut into pieces for laying into a compact body regardless of whether the pile has been roughened on one or both sides.

During laying, the pile forms a mass of fibers between adjacent layers, which is used to fill in the spaces that otherwise there would be between the separate yarns of two adjacent woven fabric structures, thus helping the problem to solve the cavities, which give the end product insufficient strength and a peeling of the layers during manufacture. One Examination of the final composition with X-rays has shown that the interlayer delineation, which is clearly visible in composites based on ordinary fabric, is barely seen can be. This is done to a useful extent without any special measures. During the laying of the layers, however, it is desirable that on the pile at numerous spaced locations by a device that actively penetrates the structure caused by adjacent layers, e.g. by needling, or by a preferred method in which fine nozzles of Apply compressed air to the free surface of the stack. The air flow method is particularly suitable for a fabric that is only on one side is piled, the fabric being laid so that the Air jets strike the undisturbed tissue side. A close one Contact of the plies must be maintained during the procedure.

The above-mentioned methods are preferably carried out on the stack while it is being placed in short intervals or also in position applied for location.

During pressing, the compression of the fibers develops both within the fabric and between the layers, with the fibers establish themselves in each other, what is sufficient to support the body for the subsequent

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To give cohesion to the following steps, as described above in connection with other procedures.

The fabric used may be of any known type, but is preferably a satin fabric and is made from a staple yarn made of worsted type to give a pile which can be easily erected without peeling and weight loss and can also be easily aligned. A suitable yarn is a polyacrylonitrile fiber with a specific density im Range from 1.30 to 1.40 g / cm, staple length no more than 10% under 3 cm and about 100 tex (English fineness number for cotton 6,900 denier) with 6 twists / inch (236 twists / m) and Z-twist.

Another possibility is to use the pile as a key for other, non-woven layers to to produce special properties. For example, a continuous filament yarn of oxidized polyacrylonitrile in a spiral can be placed between the or some layers, around the end product made from the composite material Disc to give increased ring strength due to the shrinkage of the fiber during carbonization in the circumferential direction and to compress the whole structure radially.

The steps between laying the layers and pressing them on the one hand and, for example, reworking the blank on the other hand, consists of carbonizing and graphitizing the fiber with subsequent storage of the continuous carbon phase using methods known per se. Vapor deposition of coal or impregnation with carbonizable material or a combination of the two methods can be used.

example 8th;

There was prepared a annular preform of 5o, 8 cm (22 inch) outer diameter and 14.2 cm (6 inch) inside diameter of a geflorten fabric prepared by mixing 54

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Layers were assembled, each layer having the shape of an annulus and being progressively realigned, to give them equal distribution. The fabric was an eight-string twill with pile on both sides and a weight

2
from 52o g / m. It consisted of o:

of the above structure.

2
from 52o g / m. It consisted of oxidized polyacrylonitrile yarn

Once assembled, the preform was subjected to sufficient pressure to compress it to 2.3 cm (0.9 inches) thick and then below the oxidation temperature (2oo to 300 ° C) heated until it was dimensionally stable. there has been a Preform produced that was cohesive enough to be easily handled; she was following standard procedures that are applicable to oxidized polyacrylonitrile, carbonized. This was followed by carbon impregnation by vapor deposition, wherein there were no signs of delamination during the procedure; an excellent composite was obtained in which the interlayer boundaries between the fabric were essentially indistinct. The composite was after machining used in the required form as a commercial aircraft brake disc.

Example 9 :

A part was made similar to Example 8, but with the layers of fabric were needled when laying on. A satisfactory preform was again produced, as in Example 8 has been carbonized and impregnated.

709851/07 * 1

Claims (17)

Claims 'i. Coal-coal composite, obtainable through coal storage into a fiber body, which by repeatedly laying one on top of the other of lengths of a substantially parallel multi-fiber arrangement of carbon fibers or Carbon fiber precursors is constructed. 2. Composite according to claim 1, characterized in that the arrangement of oxidized polyacrylonitrile fiber or another precursor and that the grain is pressed during or after laying at elevated temperature was to compact it and to give it cohesion through the penetrating fibers and that through the compression generated shape. 3. Composite according to claim 1 or 2, characterized in that the body is a carbonizable binder or additional Contains charcoal in fibrous or particulate form that was incorporated into the construction of the body. 4. Composite according to claim 3, characterized in that the superimposition takes place in several flat layers and the additional fiber is placed in the spaces between the layers in the form of a continuous spiral. 5. Composite according to one of claims 1 to 4, characterized in that that the arrangement is a sliver or roving, which is laid continuously by folding. 6. Composite according to one of claims 1 to 4, characterized in that that the assembly is a wrap laid in layers, each of which is the width of the composite owns. 709851 / 07X1 ORIGINAL INSPECTED 7. Composite according to one of claims 1 to 3, characterized in that the body is constructed radially by the lengths either individually or continuously by spiraling around a center point. 8. Composite according to one of claims 1 to 4, characterized in that that the assembly is a multi-filament tow with the layers of cut parallel lengths of the cable and each length in a given layer extends across the body adjacent to adjacent lengths extends in the layer. 9. Composite according to claim 8, characterized in that the Body was built by a process in which successive lengths of cable from a supply via a receiving Plate can be pulled, cut off during or after laying, laying the rope lengths over the plate divided between one length and the next by the width occupied by a single laid cable and the relative alignment of successive layers by changing the relative rotation of the layer direction and the increasing cable body is determined as needed. 10. Carbon-carbon composite made from a stack of layers of fabric _{made from} oxidized polyacrylonitrile or another carbon fiber precursor that is formed into a cohesive body, carbonized and then interspersed with carbon, in which the layers are placed on one or both of them before being laid Sides had a pile to fill the spaces between the layers and in the fabric structure. 11. The composite of claim 10, made by pressing the After placing the stack at an elevated temperature in order to reduce the 709851/0741 Fibers of the pile tightly into the spaces in the fabric structure of the Bring tissue to the body and condense it through the penetrating and attaching fibers To give cohesion and to maintain the shape given by the compression. 12. Composite according to claim 10 or 11, characterized in that that the fabric has a satin weave. 13. Composite material according to one of claims 10 to 12, characterized in that that the pile was aligned by blowing before laying the fabric. 14. Composite according to one of claims 10 to 13, characterized in that the fabric is piled only on one side and that by needling or application of fine air jets on the unfiled side during laying, the pile caused by the structure of adjacent layers penetrated. 15. Composite according to one of claims 10 to 14, characterized in that that the body contains a carbonizable binder or additional carbon in fiber or particle form, which was incorporated into the structure of the body. 16. The composite according to claim 15, characterized in that numerous flat layers are formed when laying and that the additional fiber is placed in the spaces between the layers in the form of a continuous spiral . 17. A composite according to any one of claims 10 to 15, characterized in that the body is constructed radially by placing separate pieces of tissue around a center or winding a continuous length spirally. 709851/0741