GB2190619A - Moulding a wear resistant surface from metallised carbon fibres - Google Patents

Abstract

A liquid or semi-liquid mixture of a carrier medium and chopped carbon fibres coated with magnetisable metallic material, is fed to an inlet (11) of a moulding device (12) which defines a conical guide path (13) along which the mixture is guided to an outlet (14) at which the body (15) is shaped. The carbon fibres are initially mobile within the carrier medium, and a first magnetising head (17) magnetises the coatings on the chopped carbon fibres, and a second magnetising head (18) located downstream of the first magnetising head orients the magnetised carbon fibres and arranges them to lie alongside each other and extending perpendicularly to the surface portion of the body (15), which position is retained when the mixture sets or cures. <IMAGE>

Description

SPECIFICATION Method and apparatus for forming a metallised carbon fibre wear-resistant surface This invention relates to a method and apparatus forforming a metallised carbon fibre wear-resistant surface.

The invention is primarily concerned with the treatment of metallised carbon fibres in a carrier medium of a body of any predetermined shape, in which the metallised carbon fibres are arranged in or at any predetermined surface portion of the body in such a way as to impartwear-resistancepropertiestothe surface portion. The invention therefore provides a method and apparatusfortreating the metallised carbon fibres while they are still retained in a mobile state in a continuous carrier medium, so asto arrangethefibres in an orderly manner atthe predetermined surface portion whereby they provide wear-resistant properties for the body and subsequently become set in this position.

The invention is applicable to the treatment of bodies of any predetermined shape, so as to provide wear-resistant properties as required on internal and/or external surfaces thereof.

According to one aspect of the invention there is provided a method of forming a body having a predetermined surface portion which is provided with wear-resistant properties by means of metallised carbon fibres arranged at said surface portion, the method comprising: forming a mixture of a liquid or semi-liquid carrier medium and chopped carbon fibres, the carbon fibres being coated with magnetisable metallic material and initially being mobile within the carrier medium; subjecting the mixture to an internal magnetising action in order to magnetise the coatings on the chopped carbon fibres;; applying a further magnetising action to the mixture in a controlled manner in orderto orient and to arrange at least some of the metallised carbon fibres atthe predetermined surface portion so that they lie alongside and extend generally parallel to each other and substantially perpendicular to the surface portion, whereby the metallised ends of the fibres provide wear-resistant properties to said surface; and allowing orcausing the mixture to setorcureso as to secure the metallised carbon fibres in position.

According to a further aspect ofthe invention there is provided apparatus for forming a body having a predetermined surface portion which is provided with wear-resistant properties by means of metallised carbon fibres arranged at said surface portion, the apparatus comprising:: a moulding device having an inlet for receiving a mixture of a liquid orsemi-liquid carrier medium and chopped carbon fibres, the carbon fibres being coated with magnetisable metallic material and initially being mobile within the carrier medium; a guide path defined by the moulding device for guiding the mixture from the inlet to an outlet at which the shaping ofthe body is completed; a first magnetising head arranged along said guide path for subjecting the mixture to an initial magnetising action in orderto magnetise the coatings on the chopped carbon fibres; and a second magnetising head arranged along the guide path downstream of the first magnetising head in orderto apply a further magnetising action to the mixture in a controlled manner so as to orientandto arrange at least some of the metallised carbon fibres atthe predetermined surface portion in which they lie alongside and extend generally parallel to each other and substantially perpendicular to the surface portion, whereby the metallised ends of the fibres provide wear-resistant properties to said surface and are subsequently secured in position when the mixture is caused or allowed to set or cure.

The invention also includes bodies made by the method and apparatus as defined above.

The method and apparatus of the invention may be used to form a body of any desired internal and/or external shape, and having a predetermined surface portion thereof provided with wear-resistant properties by means of metallised carbon fibres. For example, the invention may be used to make a bearing, in which it is important to provide wear-resistant surfaces on the inner and/or outer annularfacesthereof.

Preferably, the mixture contains, in addition to the metallised carbon fibres, chopped carbon fibres which are dispersed throughout the mixture and which enhance the strength of the body.

Preferred magnetisable metallic coatings for the chopped fibres are nickel coatings, though other magnetisable metals e.g. tungsten, and metal combinations may be used.

The invention will now be described in more detail, byway of example only, with reference to preferred embodiments as shown in the accompanying drawings, in which: Figure la is a schematic side view of apparatus for making a composite body with a wear-resistant surface composed of metallised carbon fibres; Figure 1b and icshowin more detail parts ofthe apparatus of Figure la; Figures2a to 2c show details of means for applying magnetic action to a composite material forming the body; Figures 3a and 3b showfurther details of the application of magnetic action; Figure 3c shows diagrammatically the production of an unmetalied surface;; Figure 4shows examples of profiles of bodies which may be formed by means of method and apparatus according to the invention; Figur5 illustrates diagrammatically possible arrangement of predetermined wear-resistant surface portions on a body; and, Figure 6to 13 show detailed views of further means for treating a composite body in orderto obtain wear-resistant surfaces portions provided by metallised carbon fibres.

Referring now to Figures 1 to 3 of the drawings, there will be described method and apparatus for forming a body of composite material having a wear-resistant surface formed by metallised chopped carbon fibres, in that an organised wear-resistant surface is provided on a carbon fibre structure in its plastic state priorto heat and pressure treatment. The apparatus is designated generally by reference 10 and can be used to form a body having a predetermined surface portion which is provided with wear-resistant properties by means of metallised carbon fibres arranged at the surface portion. A mixture of a liquid or semi-liquid carrier medium and chopped carbon fibres is supplied to an inlet 11 of a moulding device 12, the carbon fibres being coated with magnetisable metallic material and initially being mobile within the carrier medium.The moulding device 12 defines a conical guide path 13 along which the mixture is guided under pressure from the inlet 11 to an outlet 14 at which the shaping of a body 15 is completed. In the illustrated embodiment, the body 15 isa tubular body which is applied externally to a prepreg sleeve 16.

Afirst magnetising head 17 is arranged along the guide path 1 3 for su bjecti ng the mixture to an initial magnetising action in order to magnetise the coatings on the chopped carbon fibres. A second magnetising head 18 is arranged along the conical guide path 13 downstream of the first magnetising head 17 in orderto apply a further magnetising action to the mixture in a controlled manner. The further niagnetising action on the now magnetised coatings ofthe carbon fibres operates to orient and to arrange at least some ofthe metallised carbon fibres atthe predetermined surface portion (the outer annular surface in the illustrated embodiment), in which the fibres lie alongside each other and extend generally parallel to each other, and also substantially perpendicular to the surface portion i.e. radially.In this way, the metallised ends ofthe fibres which are arranged at the surface provide the necessary wear-resistant properties for the surface, and the fibre are subsequently secured in position when the mixture is caused or allowed to set orcure.

The surface is produced by nickel coated chopped carbon fibres ofsuitable size, in a composite of chopped carbon fibres in a suitable resin, which is passed through magnetic fields, and laid on a prepreg carbon fibre structure.

The nickel coated carbon fibres, referred to as metalised carbon fibres (MCFs) are one of a group, any of which, if magnetically responsive and hard-wearing, can be used, e.g. tungsten has been successfully used to coat carbon fibres.

As the composite is pressured through a first magnetic field (magnetic head 17), the angle A ensures an increased area for the flux density to influence and a reduced composite density for the MCFs to move through. As the composite moves along the guide path and through angle A apex, a compression takes place, causing an increase in MCFs density at the surface. A second magneticfield (magnet head 18)further treats this surface to increase density and orientation ofthe MCFs.

The No 2 magnetic field coils are subject to a fundamental oscillator whose frequency is summated with a higherfrequencyto match the magnetic impedance of the composite, and the circuit as a whole, whereas No 1 field coil is oscillated to vary the flux density through the composite.

Carbon fibres themselves have no particular magnetic response, although able to function as an electrical conductor. The diameter of a carbon fibre is approximately 0.006 mm (0.0003"). The diameter of a metallised carbon fibre (MCF) by the deposition method (nickel) is approximately 0.06 mm (0.003"), and the length of chopped MCFs required will be 0.5 mm (0.020") approximately.

It should be noted that the MCFs to be magnetised are substantially rigid at the size stated, and the sizes used may be iargerthan asfirst mentioned.

Nickel coated carbon fibres are, due to their structure, exceptionally suitable for magnetic manipulation due to the carbon fibre centre and inherent magnetic sensitivity of the nickel coating.

The arrangement of the MCFs at right angles to the surface is accomplished by: 1 - inducing a polarity in the MCFs.

2/3-using the induced polarity to manipulate the MCFs by magnetic fields, pressure and flow rate.

4- laying on prepreg sleeves to improve shear modulus and use the pregpreg sleeves to drawthe composite through the system to relieve build-up of pressure.

1-to induce a magnetic polarity in the MCFs: a - the MCFs less than 0.5 mm in length and 0.06 mm in diameter are mixed in a composite of the ratio 60% (non-metallised) chopped carbon fibre, 20% chopped MCF of size stated and 20% of a suitable resin.

b-it is the intention to arrange, by magnetic fields, 50% of the chopped MCFs atthe outer or bearing surface, the remaining 50% of chopped MCFs being left random in the composite.

c- the whole composite is fed under pressure through an internallytapered cone, such that the inputarea is equal to the output area atthe end ofthetaper.

d-two magneticfields are located upon the tapered cone; No 1 magnetic field consists of permanent magnetic poles varied by a single frequency such that the North South direction does not reverse but can achieve zero, the net result being pulsating flux in the North pole direction. The No 1 field coils (three) are shown mounted on their respective formers and are connected in parallel. No 2 magnetic field is a fully reversible core driven by field coils from an oscillator whose frequency is summated with a higherfrequencyto compensateforthe head to MCF magnetic impedance.

2-theactionthrough No 1 magneticfieldis: a- as the composite enters the magnetic field a polarity is induced into the MCFs. This polaritywill (generally) be a South pole at the leading edge of an individual MCF, due to the magnetic field bias stated in 1-d.

b- as the MCFstake up alignment in the magnetic field, they are compressed towards the North pole and the composite flow rate increases. This prevents clogging of MCFs atthe North pole.

can the composite expands away from the area of compression, the MCFs retain their location atthe North pole or on outer surface, but the MCF depleted composite moves away from the outer surface as shown.

d- as the whole composite moves down the cone, a compression takes place. Atthe outer surface, the individual MCFswith their induced polarity have a magnetic repulsion when parallel to each other, and this assists in the self-arrangement with respectto each other at the outer surface. The end on end (i.e. North South) attraction produces a general field effect at the outersurface.

3-the action through No 2 magneticfield: a - the No 2 field oscillating at a frequency relative to the flow rate of the composite, radiates a magnetic field across its gap as shown. This field interacts with the induced South poles of the MCFsto: b-(i) draw individual MCFs to the surface (ii) draw individual MCFs into physical contact with each other as they move aboutangleAand leave the No 2 magneticfield, and (iii) squeeze outfrom the surface area resin and carbon fibres as the MCFs move through angle A.

4- when the composite leaves the No 2 magneticfield, it is laid on the prepreg sleeves, which are compressed to the composite. The start ofthe prepreg sleeves are used to draw the whole composite through the former so that friction and over tensions in the flow system are relieved and to avoid high pressures at the input.

Frequencies for No 2 magneticfield forflow rate of 1 cm per sec 0.5-3 khz,summated frequency 27 khz depending upon composite resin to fibre mix and field strength. The interaction of individual MCFs when polarised is shown in Figures 2a - 2c. The orientation by No 2 magneticfield and the following compression brings the MCFs into tight physical contact, causing the individual MCFs to become a whole magneticfield.

The prepreg sleeve(s) are used to draw the composite through the system relieving the system of high compressive stresses. The rate at which the sleeve is drawn through being proportional to material input and required lateral compression.

The magnetic poles do not come into contact with the comnposite, but directtheirfield through a thinned area ofthe non-magnetic alloy former, (Figures 3a and 3b) refers.

Lubrication of the metallised surface to reduce friction with the alloy former can be made at appropriate points under pressure along the former.

Figure 3c shows the production of an un-metalled surface by the use of No 2 magnetic field to projectthe MCFs into the turbulence that is created at angle A by the acceleration of the composite aboutthat angle.

Referring now to Figure 4, with the use of computer design many other profiles can be achieved; given due regard to size all can be internally/externally metalled, and most profiles can be made within each other e.g. a triangularouterwith circular innter. With computer control of the magnetic fields, many patterns can be produced on the external forms and internal forms. In Figure 5there are shown wear-resistantsurface patterns which can be achieved, and also due regard should be given to sub-surface control of metal elements by computer.

Examples of applications ofthe method and apparatus ofthe invention will now be given.

Engine cylinder bore/sleeve Using prepreg mattfor outer surface strength and with the inner surface metalled, the sleeves or bores can be produced which are thin walled, strong and light and can be further treated for surface wear improvement, particularly the newer oval bores that are to be produced for lean burn engines; Reference "Engineering Design", October 1986, Honda, Page 732.

Chemical production pipe Where a chemical has to have an electrical potential across it while it flows through a pipe, then that pipe can be made by this system anbd a conduction path produced from outside to inside, without breaching the surface of the pipe, (i.e. no holesforthe passage of electrical conductors which can cause leaks).

Ball race surround Having produced a circular form from the device that has a metal surface interior and exterior and before heat and compression, then sections parted off as rings can then be placed in heat and pressure device to form a ball race surround or centre.

The system has the ability to produce a malleable form with a cross-section parallel along its length,which can be parted off and altered in shape, and having a metal surface interior or exterior that can be patterned as produced prior to heat and compression.

Overhead conductor rail An overhead conductor rail can be formed using the prepreg matt interior for lateral strength and a suitable electrical conduction type fibre and resin, (although a metallised glass fibre which is cheaperthan carbon fibre can be used, provided the heat is compatible with the glass fibre).

Cam shaft Using a suitably malleable composition, the metalled surfaces as shown, can be moved by pressure to a new profile, which allows further metalling. Although the cam shaft will have a thicker cross-section than a metal cam shaft, additives to the carbon fibre, such as aluminium oxides, etc can improve cross-sectional strength.

Crank shaft As with cam shafts, a lightweight crank shaft can be produced which, although thicker then a metal crank shaft, can within certain limits, produce a stress-bearing crank shaft, with a metalled surface that can be further metalled.

Metal on plastics In the formation of metal surfaces in a plastic matrix nylons, acrylics, polyesters and rubbers, and others that require heat and pressure, the same general system can be used and modified for cooling the standing magneticsfield and the use of high curie point metals, such as ALNICO, (Cp 250 C) > Alnico and similar high temperature curie point permanent magnetic materials, when taken to their curie point and beyond, then reduced in temperature through their curie point to room temperature in the presence of a permanent magnetic field, will align their crystal structure and their magnetic spins, in a mannerthat creates a structurally-aligned permanent magnet.

Alnico can be used with carbon fibres and plastics to construct linear induction motors and other motors.

A nylon or other plastics, and metal bearing A bearing surface using cheaper nylon as main structure and a surface that has a computer-controlled level of metalling, such that the two together- self-lubricating nylon and wear-resistant metals- provide a cheaper and superior bearing, internal and/or external.

With the article heat-treated, cured and cleaned, the metal surfaces can be furthertreated for eitherjoining with other compatible substances, such as hard-wearing material, electrical conduction material, or any other required substance that the article will tolerate.

Electrical conductors in flexible surround In rubber/plasticconveyor belts, the greatest problem in having current-carrying conductors to produce a magnetic field to drive the belt, is the disposal of heat generated within the belt, to the extentthatthe generated heat damages the rubber/plastic surround.

Using thin walled carbon fibre rods of approximately 5 mm diameter (or similar lightweight stress-bearing material that has a conductive surface, such that this system will produce), the heat generated can be removed from the belt by air driven through the hollow rod/conductor.

The thin walled conductor is supported by its surroundings and located radially to the centre, about which the belt end rotates.

Micro-wave guides Ultra/very high radio frequencies use the skin effect of a tube for conduction and propagation.

This system lends itself to the production of these wave guides, as it can produce the very thin skin with varying degrees ofimpedance along its length, as required for this purpose.

The above refers to satellites and their frequencies.

Light-emitting devices; light-carrying devices; solar power devices Light emitting devices, metalled in a manner that allows them to be magnetically orientated, can be placed adjacentto the surface of the profile so that the light detection or emitting part has access to the outside.

Small light-carrying fibres, whose outer surface has been treated with magnetically responsive substance can be controlled through the composite.

Bythe same method, solar power units can be located in the composite, subject to heat/pressure protection, so that a solar power unit embedded in the profile could power circuits within the whole structure.

Pattern generators If one takes a long profile with a metal pattern at the surface and rotates the profile in an adjacent magnetic field, the pattern will translate into a similar wave form from the adjacent magnetic pick-up, which repeats consistantly with rotation ofthe profile and the speed of rotation, in fact, it becomes a Patterngenerator.

The pattern can be changed by changing to another profile. Patterns can betaken by moving the pick-up along the profile, either rotating or non-rotating.

The above refers to inductive pattern making, but a similar process can be made with regard to capacitive pattern making - in fact a combination of both or either can take place at the same time.

Note: The need for patterns is extensive in the computer industry and in the computerised cryptology industry.

The profiles that can be produced and metalled are limited not by shape but by the size of magnets in No 2 magnetic field - i.e. a small interior diameter of form in which a magnetic cannot be physically located, therefore it is immaterial whetherthe profile is flat/curved/radiussed or any combination, either/or internal or external metalling. As long as the magnetic fields can be located, a metal surface can be produced in response to the magnetic influence.

The No 2 magnetic field can be made up of a number of individual magnetsaboutthecircumference because it is the No 2 magnetic field that organises the metal atthe surface. Then computer control ofthese individual fields produces areas of organised metal at the surface.

With the metallised or other carbon fibres organised at right angles to the surface, those fibres have security within the composite.

With No 1 magnetic field, the intention is to polarise the metal elements in the composite and to arrange them at a particular surface or position in the composite.

The No 1 magnetic field can be sectioned to provide control over various areas and in varying degrees of compaction, which reflects through to impedance/resistance of a particular path in conjunction with No 2 magnetic field.

/ Linear induction motors : AC or DC It is with linear induction motors that this structure has advantages, due to its formation of any conductor pattern on a lightweight stress-bearing form, from either an outer form or another form. The conductor pattern can be changed as the composite moves through the system and the composite can be an amalgam of any substance such as carbon fibres/glass fibres, ceramics, aluminium or other oxides, fillers, polymers etc, as long asthewhole mix is viscous and can carry the metallic substance thatwill be drawn into position by the magneticfields.

Taking a bar formed as described, there are two metal surfaces running the length of the barsu rface, separated from each other but connected about the periphery with metal just below the surface, so that a voltage applied to the two metal surfaces running the length ofthe barwill move along the bar, as the current moves about the bar, seeking a parallel path to the previous one.

These currents about the bar set up magnetic fields that are projected from the surface of the bar. An object located upon the bar which has a magneticfield that opposed the field projected from the bar, will be driven by the voltage and its associated magnetic field as the voltage moves along the bar. The object can be of permanent magnet composition, which does not need an applied voltage for it to be moved, or it can take its voltage from the side strips, or a combination of both. If the metal surfaces are given a rotation about the bar, then that rotation will be followed by the object on the bar, so that an object can be given movement along and about the bar. The object can be a pen/marker, a typehead or a locating device in a computer, or a projectile driven by high voltage and spin offthe end ofthe bar.

What is referred to above is the outer surface of a bar, but the same case can be made for the internal part of a bar, as in the case of a projectile. There are other possible patterns of magnetic development with the structure.

The energy consumption of the system is: a) the mixing of viscous composite 20% b) the pressurethroughthesystem 25% c) driving the magneticfields 20% d) heat/compression/curing 30% e) drawing the composite out of the system 5% These are mainly due to the force of atmospheric pressure, friction and gravity- a system operating outside atmospheric pressure would have considerable advantages in reduced energy requirements, uniformity or composite mix with less resin, ease of magnetic response, producing a structure that requires less given massforthe same given strength of structure.

Using the lightweightformers, magnets and other parts, a low energy solar-powered unit could be constructed to operate automatically to produce a given form continuously, and that form could be straight or curved along its axis, depending upon the external control exerted upon its output.

Figures 6to 13 show further details of apparatus for making a composite body with wear-resistant surface provided by magnetically orientated carbon fibre having magnetic metallised coatings. The system shown in Figure 7 is for a multi-layer metallising, which may have uses for circuits within a composite for items such as microchips, and opto electronics.

The individual layers may have different qualities, such as heat resistance in one layer, and stress-bearing in another layer, interleaved by metallised layers which could be patterned for their own particular uses, whether for an electronic circuit or for conductive paths to produce motor action.

With regard to plastics, those that are compatible can be layered and interleaved as described above.

Carbon fibre matrices/composites are now available that include heat resistant elements, and these types of carbon fibre matrices may be interleaved with metallised layers.

Claims (8)

1. A method of forming a body having a predetermined surface portion which is provided with wear-resistant properties by means of metallised carbon fibres arranged at said surface portion, the method comprising: forming a mixture of a liquid orsemi-liquid carrier medium and chopped carbon fibres, the carbon fibres being coated with magnetisable metallic material and initially being mobile within the carrier medium; subjecting the mixture to an initial magnetising action in orderto magnetise the coatings on the chopped carbon fibres;; applying a further magnetising action to the mixture in a controlled manner in orderto orientandto arrange at least some of the metallised carbon fibres atthe predetermined surface portion so that they lie alongside and extend generally parallel to each other and substantially perpendicularto the surface portion, whereby the metallised ends ofthefibres provide wear-resistant properties to said surface; and allowing orcausingthe mixtureto setorcure so asto secure the metallised carbon fibres in position.

2. A method according to Claim 1 in which the mixture contains, in addition to the metallised carbon fibres, chopped carbon fibres which are dispersed throughout the mixture and which enhance the strength of the body.

3. A method according to Claim 1 or Claim 2 in which the magnetisable metallic coatings for the chopped fibres are nickel coatings.

4. Apparatus for forming a body having a predetermined surface portion which is provided with wear-resistant properties by means of metallised carbon fibres arranged at said surface portion, the apparatus comprising: a moulding device having an inlet for receiving a mixture of a liquid orsemi-liquid carrier medium and chopped carbon fibres, the carbon fibres being coated with magnetisable metallic material and initially being mobile within the carrier medium; a guide path defined by the moulding device for guiding the mixture from the inlet to an outlet at which the shaping ofthe body is completed; a first magnetising head arranged along said guide path for subjecting the mixture to an initial magnetising action in orderto magnetise the coatings on the chopped carbon fibres; and a second magnetising head arranged along the guide path downstream ofthefirst magnetising head in orderto apply a further magnetising action to the mixture in a controlled manner so asto orient andto arrange at least some of the metallised carbon fibres at the predetermined surface portion in which they lie alongside and extend generally parallel to each other and substantially perpendicularto the surface portion, wherebythe metallised ends of the fibres porvide wear-resistant properties to said surface and are subsequently secured in position when the mixture is caused or allowed to set orcure.

5. A method according to Claim 1 and substantially as herein described.

6. A method offorming a body having a predetermined surface portion which is provided with wear-resistant properties, the method being substantially as herein described with reference to the accompanying drawings.

7. Apparatus according to Claim 4 and substantially as herein described.

8. Apparatus for forming a body having a predetermined surface portion which is provided with wear-resistant properties, the apparatus being substantially as herein described with reference to the accompanying drawings.