DE7715902U1 - Friction element - Google Patents

Description

DipWng. Heinz Bardehte

Patent attorney

B Munich 22, Hemisir. 15 »Te). 29255! Postal address MßRches 2ί »PO Box 4

My reference: S 2507 Munich, the "8 · ^ Sl" 1977

Applicant: Morganite Moämor Ltd.

11 Battersea Church Road
London SW11 3LZ

England

Coal-coal composite

The invention relates to a carbon-carbon composite. She concerns in particular the manufacture of coal-coal composites for aerospace or general applications, especially when high mechanical strength and good thermal conductivity go together with low density are needed. Examples include rocket propulsion nozzles and civil and military applications Supersonic aircraft. *

Composites, in which carbon and graphite fibers have a carbon matrix f reinforce are known and established. The fibers can be randomly distributed or incorporated in an orderly fashion to get 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 cannot be achieved. 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 amount of material waste, with 50% or more being lost.

The problems of insufficient strength that arise only after the completion of the process of preparing the carbon matrix that 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 cloth or fabric structure therein may cause voids in the finished composite can cause a corresponding loss of strength. Without wanting to limit the invention to the theory, in the context of Invention the possible occurrence of these voids can be reduced by preserving the uniformity and uniformity of the pore structure in the material is improved and the size of the gaps that occur in formation

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the continuous carbon fiber need to be filled is reduced.

In the manufacture of composites, the main role of the fiber is to act as a base on which the 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 are light

could be bridged by the deposited carbon. In addition

f play, carbon is easily formed when the vapor is deposited in the fabric

within a multifilament yarn; however, the columns seem

; Sometimes too far between the yarns for the coal to lightly pass them

could bridge to a completely cohesive structure too

• result in 1.

To overcome these difficulties, it was proposed that the ■; To give the structure a better cohesion by needling, sewing or quilting, however, 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 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 superimposing of lengths of a substantially parallel-aligned multifiber array of carbon fibers or a precursor, the invention extending to the method, 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 charcoal into a fiber body, which is caused by repeated laying one on top of the other of lengths of a substantially parallel multi-fiber arrangement made of carbon fibers or carbon fibers Precursors is built.

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 an aspect of the F ^a ~ fibers are Kammgarnzug / roving or roving and winding (batt) JDiese, as described further below, easily fitted and give end products such as brake discs, of 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 the breaking of the continuous filament to form staple strips (sliver) and their conversion into laps or drawstrings 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, a cable with parallel filaments used / can and advantageously also used will. Gladly a preferred embodiment of the invention Therefore, a fiber body is used which is built up from layers of cut parallel lengths of cable with each length in a given layer extending across the body and to adjacent lengths in the Layer adjoins. Such layers lie one on top of the other, the relative orientation being determined by that in the finished body or The mechanical properties required by the composite material are determined; in the case of a brake disc, for example, these are uniform

To give strength in all radial directions.

A body of this type can be placed for a method _f are drawn in which successive lengths of a supply cable via a pressure-receiving sheet or plate and are cut off, while they are placed nachdem.oder? laying the cable lengths. across the panel between one length and the next is graduated by the width taken up by a single one, and the relative orientation of successive layers is determined by relative rotational grading of the layer direction and the growing body of cable as needed.

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 inventor *

In the proposed method, regardless of the representation, j | In the form of the fiber, the fibers can easily be mixed sufficiently to obtain uniform strength without layers of inferior strength. This can be supported, for example, by pressing the body in its construction. A desired increase in the amount of fiber per unit volume is obtained without sacrificing the advantages of a systematic, predetermined orientation of the fibers in the composite. Composites with excellent mechanical properties can be obtained. ι

The most suitable carbon fiber precursor is polyacrylonitrile, however, others such as rayon can also be used. Polyacrylic is first applied by methods known per se, e.g. for 0.5 to 5 hours at 200 to 300 ° C, is oxidized (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 coherent 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 reached 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 manufacture and uses of the various forms of staple fiber are discussed below. The production the staple fibers themselves consist of a continuous filament of polyacrylonitrile or another precursor, such as rayon, is well known. Particularly suitable staple fiber is made according to the applicant's method described in GB patent application 35903/75 (corresponding to DT-OS 26 39 409) is prepared. The content of these patent applications mentioned hereby becomes the subject matter made of the present description.

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

Staple fiber over a system of rollers and other spreading devices, as is customary in textile machines, combs and pulls around a top yarn of essentially 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 of 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 upper thread or roving is laid to form a

% Fiber body depends on the orientation of the fibers, which is required in L of the particular component that the composite is to form. One suitable method is to use a

p feeding head, from which the face yarn is stored, and a% table on which the Obergarnkörper is established, said relative reciprocating movement to take place between the table and the head so that the face yarn is continuously over laid across and increasingly required to Thickness is built up. When the composite material obtained as a product must be radially uniform, 'such as in a brake disc, the table and the head ^can: be rotated relatively at intervals so that the direction of the fiber layers is distributed statistically.

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

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adapted to the invention are known as such. You place material vertically through a suitable and descending device which distributes the body of upper yarn uniformly in ascending layers, the length of the reciprocating trains is adjusted so that it is adapted to the dimensions of the body to be manufactured.

It is favorable that each individual or a specific person should follow suit 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 on to confusion of the already established body avoid and set the table at a suitable angle; the angle for advancing and the number of in any one Orientation applied layers is determined so that the finished end product has 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 multifilament cable _{made of} oxidized polyacrylonitrile of 1.5 denier, were spread out and laid side by side over a square plate measuring 12.7 cm on a side by letting them run 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 compared to 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 method lay-up, which involves laying the fiber by routing it around an array of pins rather than using one Folding head takes place, which is particularly suitable for top yarn.

Example 2 :

In one example, a length of roving is g with a weight of 1.69 / m, made from multi-filament tows of oxidized polyacrylonitrile with 1.5 denier per filament rausein by successively, _{breaking un (3 at} a _ere already described steps, side by side on a A square board with an edge length of 12.7 cm was laid, which it spanned repeatedly in different directions with the help of guide pins 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 kq / c ;: ² (80 psi) for 20 minutes and gave one

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compact body of ο, 51 cm thick with a fiber volume of 38%. The compact body was rigid 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 winding have the same width as the finished composite, "where the lengths whereby adjacent / possible weaknesses there off. While the lap comes in certain lengths and therefore, as with fabric, waste is generated, the structure of the lap is very open and loose and such waste can easily be returned without fiber loss.

The production of laps is inherently 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 lays 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 display 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 happen that is heated to a suitable temperature and applied to the surface of the body to make the fibers

- "1V-

to settle into one another and progressively to form a compact body. If necessary, a heating medium, e.g. superheated steam, passed through.

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 repeated superimposing mentioned above in the broad sense according to the invention is, however, can also be done by laying or winding around a center. 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 can _directly correspond to _{the thickness of the desired} body, the dimension, particularly the width of the strand of face yarn, roving or cable, or two or more strands can be placed 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 the strands and can therefore be described 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 Body of the second stage, to get the one to handle in the course the production and in particular for the formation of the carbon matrix is suitable, further steps are desirable if the compact First stage body is not intended to be held in a jig.

The compact body of the first stage, if it consists of oxidized polyacrylonitrile, can accordingly be pressed, for example, 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 produced 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 may come from the outer circumference or the inner circumference or both are fed to produce a radial fibrous structure parallel to the flat surfaces of the disc, the whole can be achieved easily and precisely by suitable switching devices.

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

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In the case of a body of wound upper yarn or roving, the additional fiber can be either continuous or intermittent Winding of tow from continuous filaments.

When carbonization is based on the laying on of a wound structure, especially when fibers are made from continuous filaments are present, the contraction of the fibers causes a solidification of the structure in addition to a previous one solidification possibly achieved by pressing. If z. B. a brake disc is produced on a central mandrel the contraction of the fibers radial consolidation of the structure when the fibers shrink circumferentially. Further the fibers are kept under tension to a certain extent during carbonization, thereby increasing their ultimate strength is improved.

Example 3:

An example of a part

made using the present aspect of the invention is a 50.8 cm (22 inch) brake disc outer diameter, 14.2 cm (6 inches) inner diameter and 2.3 cm (0.9 inch) thickness. It is made from several rovings, which are wound into a blank of such a size that the necessary skimming between the infiltration or Draw-in steps and 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 around 10 cm in length and itself from an oxidized polyacrylonitrile laser of 1.5 den and the specific density 1.30 to 1.40 g / cm 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 laid on Water or other liquid moistened to remove the fibers of the

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 moistened cable is also shaped so that it is given a cross-section, which allows that when laying successive lengths are close to each other and so the possibility of gaps between the cables in the finished body is reduced. There are several suitable forms. 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, however, if desired, a more volatile liquid can be used or, alternatively, a solution of an adhesive that will remove the body Hold the cables together for the subsequent processing steps and can possibly contribute to the final carbon bond of the composite. 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, for. B. in a 3 to 10% addition, based on the fiber weight, take place; other adhesives can be used, which evaporate when the coal formation begins. The figure shows a blank according to Example 3. Specific examples of such procedures follow, with the first example containing general information that also applies to the refer to other examples.

Example 4

A continuous filament tow made of oxidized polyacrylonitrile, which was slightly moistened by spraying with water, was used.

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The amount of water applied can be according to the quality of the dry tow: if the dry tow already has a certain degree of bonding between the filaments, z. B. by having a suitable dimension that it will keep from separating, is the amount required of added water as little as possible and can be zero. For a cable that easily breaks up into flakes, there must be enough Water can be added to hold the filaments together.

The wetted fiber, which was held under slight tension and whose total length used was measured, then became repeatedly drawn over a receiving plate, successive lengths being trimmed after drawing and the laying of the lengths has been adjusted regularly across the plate so that successive lengths are against one another lay. It can be achieved that consecutive cables side by side without a gap that is wider than some filament diameter is arranged, but also without overlapping. Alternatively, a careful overlap can be used can be generated by 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. Laying oegann 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 deposited layer at 90 °, 35 ° and 0 ° were aligned.

Example 5

A second body was made by adding an additional

2
centered rectangular hole about 6.54 cm

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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 ⁿ AESS fiber cable of 2O.OOO filaments having a fiber density of 1.35 g / cm and a cable weight of 3.49 g / m before (which is the weight of 9 .OOO m of a single filament in grams). In Example 4, 20 layers were laid with 7.3 m of cable per layer and 35 lengths in each layer, the final weight of the body being about 500 g. After compressing the laid body by 20%, the final thickness was 2.54 cm and the fiber volume fraction was 0.37. The body of Example 3 was very similar, but the amount of cable used was slightly higher because of the lack of the 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 up. The weight was 285.8 g and the fiber volume fraction was 2.54 cm Thickness without pressing after laying o, 217.

Example 7 :

A body was made as in Example 5, but with 18 layers that Contained 6.63 m of cable per shift. The directions between the layers were 3o, 6o, 9o, 12o, etc. The final weight the body was 421 g; it was compressed and gave a fiber volume fraction of 0.31 at a thickness of 2.54 cm.

All of the above bodies were great for carbonizing the fiber and subsequent carbon penetration by 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 finishing of the finished, coal drawn-in blank

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on the other hand in carbonizing and possibly graphitizing the fiber and subsequent drawing-in of the continuous carbon phase by methods known per se. The carbonation can e.g. take place at 1,000 to 1,600 ° C and graphitization at 2,000 to 3,000 ° C. The steam application of coal or 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 which neither k to detachment _e i £ _he performs handling in subsequent process steps or 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 hollow | by increasing the number of bridging points between the fibers clear which remain after the carbon impregnation. However, the structural advantages gained from the systematic alignment of the fibers in the body are retained.

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 compressed 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, when placing the body on, a carbon dioxide

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addable resin binder or another adhesive

expose, with particular in connection with bodies laid rope lengths described results.

If desired, continuous lengths of fiber or staple yarn can be laid in a body which is built up ^{in a plane m.} For example, a brake disc may contain spirals of continuous fiber placed in the body at intervals to give the disc as a whole an increase in hoop strength after completion and also to aid in the densification of the structure during the carbonization of the preferred starting material, which, as previously stated , Is polyacrylonitrile in oxidized form. In order to achieve this, the middle part of the body, if it was made without a hole, is cut out and the whole thing is attached via a mandrel between holding plates. The contraction of the spiral of continuous fiber during carbonization gives a radial consolidation of the structure as the strands shrink in the circumferential direction. Furthermore, the fiber inserted in this way is kept under tension at least to a certain extent by the shrinkage tension during carbonization, and its ultimate strength is thereby increased.

Another, separate approach to the difficulties found with fabric composites is 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 from superimposed layers of fabric made of oxidized polyacrylonitrile or other carbon fiber precursors, which is 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 secures important Advantages both in building the pile and in the formation of the compacted bodies from the fabric. It is desirable To use long staple fiber in the fabric, e.g. 4 cm to 6 cm staple, and to pull a long pile of e.g. 1 to 3 cm. The fiber in carbonized fabric is far too brittle to be able to pull such a pile. When the weft side a forerunner fabric with a satin weave, e.g. an eight-string

Body, placed in a suitable device, As is well known in the textile art, a substantial proportion of the staple fiber in the weft can escape from the body of the weft yarn are drawn parallel to the warp. The surface takes on a smooth felt-like appearance (although the fibers of the pile are not felted) and the fabric structure of the cloth is completely covered. Such a pile is under the The name plush pile (shag nap) is known.

When such a fabric is laid on, a compression 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 give it cohesion through the fibers that get stuck in it and that achieved through the compression 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. Eg 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 fabric is used. The pile can be made by compressed air or steam nozzles or mechanically, e.g. by brushing.

In the manufacture of carbon-carbon composites it is preferred uses a woven cloth that has a relatively flat surface. This is preferably done using a Satin fabric achieved. When a pile is erected on a cloth with such a weave, it is mainly attached to the Warp threads erected on one side and on the weft threads on the other side. If the pile means of a continuous The process is erected on a cloth roller, the pile is on the warp surface on which the process is carried out along the length of the The yarn looks shorter than a pile on the weft surface, where the process works 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 around 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 would exist 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 X-ray examination of the final composition has shown that the interlayer delineation, which is common in composites is clearly visible based on ordinary tissue, can hardly be seen. This is done to a usable extent without any special Measures. During the laying up of the plies, however, it is desirable that the pile be placed on the pile at numerous spaced apart locations acted upon by a device which actively caused its penetration into the structure of adjacent layers, e.g. by needles, or by a preferred method in which fine nozzles of compressed air act on the free surface of the stack. The airflow method is particularly suitable for a fabric that is piled only on one side, 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 a 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, 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 satin fabric and made from a staple yarn made of worsted type to give a pile that 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 approximately 100 tex (English punit number for cotton 6,900 denier) with 6 turns / inch (236 turns / m) and ^ -twist.

Another possibility is to use the pile as a key for other, non-woven layers in order to to produce special properties. For example, a continuous filament yarn of oxidized polyacrylonitrile in a spiral can be placed between the or several layers, around the end product made from the composite material Washer 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 consists in the carbonization and graphitization of the fiber with subsequent storage of the continuous carbon phase by means of methods known per se. It can cause vapor deposition of carbon or impregnation with carbonizable material or a combination of the two processes will.

Example 8:

An annular preform 50.8 cm (22 inches) outside diameter was made and 14.2 cm (6 inch) inner diameter of a pleated fabric by using 54

- T3.
Zj

Layers composed, each layer taking the shape of a And gradually realigned to give them equal distribution. The weave 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.

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

Once assembled, the preform was subjected to sufficient pressure to compress it to a thickness of 2.3 cm (0.9 inches) and then below the oxidation temperature (2oo to 300 C) heated until it was dimensionally stable. A preform was produced that had sufficient integrity to be easily to be handled; it has been carbonized using standard procedures applicable to oxidized polyacrylonitrile. It coal impregnation by vapor deposition followed, 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.

Claims (17)

Expectations . ^ Friction elementJ> obtainable through carbon storage into a fiber body which, by repeatedly superimposing lengths of a substantially parallel multi-fiber arrangement of carbon fibers or carbon fiber precursors is constructed. 2. Friction element according to claim 1, characterized in that the arrangement of oxidized polyacrylonitrile fiber or j consists of another precursor and that the body of the Friction element during or after the application at increased Temperature was pressed in order to compact it and to give it cohesion through the penetrating fibers j and the shape created by the compaction. 3. Friction element according to claim 1 or 2, characterized in that that the body contains a carbonizable binder or additional carbon in fiber or particulate form, the was incorporated into the structure of the body. 4. friction element according to claim 3, characterized in that it is obtainable by superimposing several, flat layers and laying the additional fiber in spaces between the layers in the form of a continuous Spiral. 5. Friction element according to one of claims 1 to 4, characterized in that the arrangement is a sliver or roving is laid continuously by folding. 6. Friction element 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. 7715902 04/27/78 7. Friction element according to one of claims 1 to 3, dadurcn gekennzeicnnet that the body is constructed radially, wherein the lengths are either one-on-one or continuously wound around a center point in a spiral. 8. Friction element according to one of claims 1 to 4, characterized in that that the arrangement is a tow of many filaments, the layers of cut parallel Lengths of the cable are built up and each length is given in one Layer extends across the body adjacent to adjacent lengths in the layer. 9. friction element according to claims 8, characterized in that the body is constructed according to a method in which successive Cable lengths are drawn from a supply over a receiving plate, cut off during or after laying the laying of the rope lengths over the plate zv / iscnen one length and the next by the width, which is taken up by a single laid cable is classified, and the relative orientation of successive ones Scanning is determined by relative rotational change in the layer direction and increasing cable body as required will. 10. Friction element from a stack of iiaqen from oxidized Polyacrylonitrile or another carbon fiber precursor, thereby Marked that it was obtained by molding a cohesive body, carbonization and subsequent penetration with coal, in which the layers are placed before being placed on top had a pile on one or both sides to fill the spaces between the layers in the fabric structure. 7715902 04/27/78 11. friction element according to claim 1o, characterized in that it is made by pressing the stack after Laying on at elevated temperature in order to close the fibers of the pile into the spaces in the fabric structure of the fabric bring the body to condense and penetrate it through and to give cohesion to the fibers that have set themselves and to maintain the shape given by the compression. ι 12. Friction element according to claim 1o or 11, characterized in that that the fabric has a satin weave. 13. Friction element according to one of claims 1o to 12, characterized characterized in that the pile has been aligned by blowing before laying the fabric. 14. ReiDungselernent according to one of claims 1o to 13, characterized characterized in that the fabric is piled only on one side and that one can be made by needling or using fine air jets on the unfiled side during laying caused the pile to break through the structure of adjacent layers penetrates through .. 15. Friction element according to one of claims 1o to 14, characterized characterized in that the body contains a carbonizable binder or additional carbon in fiber or particle form that was incorporated into the structure of the body. 16. Friction element according to claim 15, characterized in that when laying numerous flat layers are geo formed and that the additional fiber in the spaces between the Laying layers in the form of a continuous spiral. 17. Friction element according to one of claims 1o to 15, characterized characterized in that the body is constructed radially by placing separate pieces of tissue around a center or spirals up a continuous length. 7715902 04/27/78