GB2221900A

GB2221900A - Elongate carbon materials

Info

Publication number: GB2221900A
Application number: GB8913043A
Authority: GB
Inventors: Susuma Takahashi; Hitoshi Yoshinaga; Mochimasa Zusho
Original assignee: Kanto Yakin Kogyo Co Ltd
Current assignee: Kanto Yakin Kogyo Co Ltd
Priority date: 1988-06-08
Filing date: 1989-06-07
Publication date: 1990-02-21
Anticipated expiration: 2009-06-07
Also published as: JPH0359200B2; GB8913043D0; JPH01314793A; GB2221900B

Abstract

The present invention provides a method of preparing elongate carbon fibre reinforced materials by the compression of a preform of an elongate bundle of carbon fibres impregnated with carbonous resins, by keeping the preform under tension and by braiding over the preform as it progresses, threads which are also kept under tension, and optionally removing the threads after the materials have been carbonized or simultaneously when the materials are carbonized. The invention also provides the products of such processes and endless lengths of carbon fibre-reinforced materials. <IMAGE>

Description

Elongate Carbon Materials The present invention relates to a method of making elongate materials from dense carbon fibres and also to said materials.

Conventional methods for manufacturing elongate carbon-fibre reinforced materials and the problems associated therewith may be illustrated by reference to the preparation of such a material of 2mm in diameter and 200mm in length. The carbon fibres are prepared in a bundle, impregnated with thermosetting carbonaceous resin as a binder and dried.The bundle is placed in a mould having a groove cavity of the above dimensions, heated to 1500C and hardened at a pressure of about 30MPa. The bundle thus shaped is heated to 600"C under a nitrogen atmosphere, and then densified by heating it at a different heat elevating speed further to a temperature in excess of 1,0000C. When an extremely dense structure is required, the bundle is coated again with resin, and subjected to a further heat treatment at 1.0000C.

Thus, it is extremely difficult to obtain a stick-like bundle of long length, as conventional methods inevitably employ moulds for shaping and hardening the bundle.

When materials made from dense carbon fibres are used for artificial satellites, especially in rocket nozzles for example, the structure of the compounds has to be extremely dense. However, in cases where the compound is utilised as high temperature-resistant material in common industrial fields, their purpose is generally to replace metallic parts unable to withstand high temperatures. Therefore, the carbon compound does not need to be extremely highly densified when it is used in such fields.

An object of the invention is, therefore, to provide a method of preparing an elongate material made of carbon fibre-reinforced carbon compounds having a tensile strength which can hardly be obtained by conventional 2 thermal resistant alloys, such as lOKg/mm at a temperature of 1,2000C.

Therefore, in a first aspect, the present invention provides a method for making a length of carbon fibre reinforced material, comprising impregnating a bundle of carbon fibres with a suitable binder and winding one or more threads about the bundle under tension before hardening and heating. Preferably, the bundle is also kept under tension at least during the winding of the threads.

It will be appreciated that a prime advantage of this invention is that the requirement for a mould is dispensed with, allowing potentially endless lengths of carbon fibre reinforced rope to be made.

The 'threads' may be of any suitable material and primarily serve to bind the bundle together before it is set. Preferably, a number of threads are used to form a braid about the bundle and not only serve to bind the bundle but to squeeze out air and excess binder. If desired, the threads may be removed after the bundle is stablised, for example by dissolution, burning or melting.

The products of the method also form a part of the invention, and the invention also provides a seamless, endless length of carbon fibre reinforced material, optionally bound by one or more threads. The invention further provides a length of carbon fibre reinforced material bound by one or more threads. As used above, 'seamless' means without junctures along the length of the rope, or other such material, such as where individual lengths have had to be joined, and 'endless' means without limit with regard to possible length.

Carbon fibres for use in accordance with this invention are suitably those available in the market and having a tensile strength of 100-500Kg/mm2 at a temperature of 1.000-3,0000C. Binders are suitably selected in accordance with the purpose of the elongated material, and preferably, from thermoplastic resins such as pitch, and thermosetting resins, such as phenol and furan resins.

In one aspect of the invention, an elongated preform is first made by bundling carbon fibres of a number necessary to constitute a desired wire diameter, and impregnating the bundle with a dissolved or molten resin. Threads are entwined over the elongated preform so that a braid with said preform as a core is formed.

The preform is hardened and shaped while it is compressed circumferentially inwardly by the braid, and then subjected to a heat treatment according to the binder employed.

Unlike the conventional method, which cannot prepare continuously elongated materials, the method of the invention presses out air and excessive resins contained in a bundle of carbon fibres, after it has been impregnated with the resins, by forming the braid over the bundle so that the braid compresses the bundle inwards circumferentially. Threads to form the braid are entwined while being axially stretched. Therefore, the tensile force applied on the threads works upon the bundle first longitudinally and then compressedly transversely to its axis. It is a characteristic feature of this invention that an elongate compound can be continuously prepared.

While the principal purpose of the braiding is to exert a circumferential as well as axial compression force on the preform, the braiding can also perform other objects. According to the material selected for the threads, the threads can perform a specific task, or if desired, they can be dissolved, melted, or burned from the compound after heat-treatment.

The accompanying drawing illustrates an embodiment of the method of the invention. in which a braider is illustrated diagrammatically by its thread-supplying reels.

In the specific embodiment of the invention described below, wire coils for a mesh belt for a high-temperature heating furnace are prepared.

A bundle 2 is loaded on a reel 1, the bundle consisting of, in this instance, six small-diametered bundles, each consisting of 12,000 carbon fibres. The bundle 2 is continuously passed through a bath 3 containing resins melted at 2400C, and wound up by a coil-shaping mandril 7. The resins are conveniently thermoplastic pitch.

The bundle thus impregnated with the pitch is circumferentially and also axially compressed and stretched by glass threads supplied from reels 4 and formed into braids while the bundle is continuously fed to the mandril 7. Air and excessive pitch contained in the bundle are purged from the bundle as it is compressed, and the bundle 5 is subjected to heat-treatment at 3000C as it passes through a furnace 6. The bundle 5 is then wound up on the mandril, which has a flattened ellipse cross-section, thus forming an elongated continuous coil 8, which is cooled.

A mesh belt was assembled by using the coil 8 with linear sticks of carbon-fibre reinforced carbon compound which had been prepared in a way similar to the above-described method. The mesh belt was heated in a nitrogen atmosphere up to 2,5000C after having been passed through 6000C and then 1.0000C.

The mesh belt thus prepared ran well through a high temperature furnace kept at 2,5000C and under a high tensile strength with a heavy load.

While the above embodiment describes the preparation ofa continuous wire, other sticks, rods, cables and pipes can readily be made in accordance with the method of the invention.

Claims

1. A method for making a length of carbon fibre reinforced material, comprising impregnating a bundle of carbon fibres with a suitable binder and winding one or more threads about the bundle under tension before hardening and heating.

2. A method according to claim 1 wherein the bundle is also kept under tension at least during the winding of the threads.

3. A method of preparing an elongated shape of carbon fibre reinforced carbon materials, which comprises; impregnating an elongated bundle of carbon fibres with carbonous binders by continuously passing it through said binders, forming braids of threads over the bundle as the bundle is transferred, and heating the bundle, while the bundle is compressed circumferentially by the braids, and while the bundle and the braids are kept under a tensile force.

4. A method as claimed in Claim 1, 2 or 3, in which the binder comprises a thermoplastic resin or a thermosetting resin.

5. A method as claimed in Claim 1, 2 or 3, in which the binder comprises pitch or phenol or furan resins.

6. A method as claimed in any preceding claim in which the threads comprise carbon, metallic, ceramic and/or organic fibres.

7. A method as claimed in any preceding claim in which the threads are removed from the bundle when or after the bundle is or has been subjected to heat-treatment, by dissolving, melting, or burning out the braids.

8. A method as claimed in claim 7 in which the threads are removed from the bundle by dissolving, melting, or burning.

9. A process for producing carbon fibre reinforced materials, without the need for a compression mould, substantially as described herein.

10. A carbon-fibre reinforced material produced in accordance with the method of any preceding claim.

11. A seamless, endless length of carbon fibre reinforced material, optionally bound by one or more threads.

12. A length of carbon fibre reinforced material bound by one or more threads.

13. Carbon fibre reinforced material according to any of claims 10 to 12 substantially as described herein.