Fibre spreading

Abstract

A method of spreading fibres, the method comprises providing a continuous fibre bundle having an initial width W.sub.a and causing the fibre bundle to run, in a running direction, through tensioning means and past or through fluid flow means, the tensioning means intermittently varying the tension in the fibre bundle and the fluid flow means producing a fluid flow through the fibre bundle as the tension varies in the fibre bundle, whereby the width of the fibre bundle increases to a spread width W.sub.b. Apparatus (1) is also disclosed, which apparatus (1) comprises a tensioning means (3) to intermittently vary the tension in the fibre bundle (2) and a fluid flow means (4) for producing a flow of fluid through the bundle (2).

Claims

1. A method of spreading fibres, the method comprising providing a continuous fibre bundle having an initial width W.sub.a and causing the fibre bundle to run, in a running direction, through a tensioner and a contact member, the tensioner intermittently varying the tension in the fibre bundle and the contact member comprising a microfibre fabric arranged to contact the fibre bundle, whereby the width of the fibre bundle increases to a spread width W.sub.b.

2. The method according to claim 1, wherein the microfibre fabric comprises a nap arranged in a direction opposite to the running direction of the fibre bundle.

3. The method according to claim 1, further comprising a binder breaker member configured to break or loosen binder in and/or on the fibre bundle.

4. The method according to claim 1, comprising restricting the fibre bundle width after the fibre bundle has run through the tensioner.

5. The method according to claim 1, wherein the fibre bundle comprises glass fibres.

6. The method according to claim 1, comprising causing or providing a ratio of spread width W.sub.b to the initial width W.sub.a of greater than 5:1.

7. The method according to claim 1, wherein the fibre bundle comprises plural filament fibres each having a diameter and the fibre bundle comprises an average spread thickness T.sub.b, comprising causing or providing a ratio of the average spread thickness T.sub.b to the diameter of individual filament fibres of between about 4:1 and 1:1.

8. The method according to claim 1, comprising translating the tensioner in the running direction of the fibre bundle.

9. An apparatus for spreading fibres, the apparatus comprising a tensioner and a contact member, the tensioner being arranged to intermittently vary the tension in a continuous fibre bundle running therethrough and the contact member comprising a microfibre fabric arranged to contact the fibre bundle thereby to increase the width of the fibre bundle from an initial width W.sub.a to a spread width W.sub.b.

10. The apparatus according to claim 9, wherein the microfibre fabric comprises a nap arranged in a direction opposite to the running direction of the fibre bundle.

11. The apparatus according to claim 9, wherein the tensioner comprises one or more tensioning rollers, and the microfibre fabric is located on and/or around the one or more of or all of said one or more tensioning rollers.

12. The apparatus according to claim 9, further comprising a binder breaker member configured to break or loosen a binder in and/or on the fibre bundle.

13. The apparatus according to claim 12, wherein the binder breaker member comprises a tortuous pathway through which the fibre bundle runs or is configured to run.

14. The apparatus according to claim 9, wherein the apparatus comprises an accumulator configured to restrict the fibre bundle width.

15. The apparatus according to claim 14, wherein the accumulator is located downstream of the tensioner.

16. The apparatus according to claim 9, wherein the spread width W.sub.b has a ratio to the initial width W.sub.a of greater than 5:1.

17. The apparatus according to claim 9, wherein the fibre bundle comprises plural continuous filament fibres each having a diameter and the fibre bundle comprises an average spread thickness T.sub.b and wherein the average spread thickness T.sub.b has a ratio to the diameter of individual filament fibres of between about 4:1 and 1:1.

18. The apparatus according to claim 9, wherein said tensioner is arranged to translate, in use, in the running direction of the fibre bundle running therethrough.

19. The apparatus according to claim 9, wherein said tensioner comprises one or more tensioning rollers which are moving or are movable in order to intermittently increase and decrease tension in the fibre bundle.

20. The apparatus according to claim 19, wherein one or more or all of said one or more tensioning rollers rotates or is rotatable about its or their central axis or axes.

Description

(1) Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

(2) FIG. 1 is a side view of an apparatus according to a first embodiment of the invention;

(3) FIG. 2 is a plan view of the apparatus of FIG. 1;

(4) FIG. 3 is a side view of components of the apparatus of FIG. 1 in a first condition;

(5) FIG. 4 is a sectional side view taken along the plane indicated by A-A in FIG. 2;

(6) FIG. 5 is a plan view of the component of the apparatus shown in FIG. 4;

(7) FIG. 6 is a perspective view of the component of the apparatus shown in FIG. 4;

(8) FIG. 7 is a side view of components of the apparatus of FIG. 1 in a second condition;

(9) FIG. 8 is a side view of various arrangements of rollers on creels according to the invention;

(10) FIG. 9 is a side view of an apparatus according to a second embodiment of the invention;

(11) FIG. 10 is a plan view of the apparatus of FIG. 7;

(12) FIG. 11 is a sectional side view taken along the plane indicated by B-B in FIG. 9;

(13) FIG. 12 is an end view of the component shown in FIG. 10; and

(14) FIG. 13 is a partial sectional view of FIG. 8 taken from the area C;

(15) FIG. 14 is an SEM micrograph of the microfibre fabric shown in FIG. 8;

(16) FIG. 15 is a photograph of a fibre bundle running over a micro-fibre fabric; and

(17) FIG. 16 is a graph of results of fibre spreading.

(18) Referring now to FIGS. 1 and 2, there is shown an apparatus 1 for spreading fibres according to a first embodiment of the invention, the apparatus 1 comprising a bobbin 20 for supply of a continuous fibre bundle 2, a tensioning apparatus 3 and a fluid flow apparatus 4.

(19) The fibre bundle 2 comprises, in and embodiment, plural continuous carbon fibres held together by a binding agent. The fibre bundle 2 is supplied from the supply bobbin 20 and runs through the apparatus 1 to a take up reel 5, as will be described further below.

(20) The tensioning apparatus 3 comprises first, second and third tensioning creels 30a, 30b, 30c each of which comprise first and second tensioning rollers 31a, 31b. The tensioning apparatus 3 also comprises a damping mechanism 32, located upstream of the tensioning creels 30a, 30b, 30c, which includes a pair of freely rotatable damping rollers 32a, 32b. Rotational axes (indicated by a +) through the supply bobbin 20, each of the tensioning creels 30a, 30b, 30c, each of the tensioning rollers 31a, 31b, the damping rollers 32a, 32b and the take up reel 5 are parallel to one another and thereby orthogonal to the running direction R of the fibre bundle 2.

(21) The first, second and third tensioning creels 30a, 30b, 30c are each connected to a motor (not shown) operable to independently drive rotation of each of the tensioning creels 30a, 30b, 30c. The first and second tensioning rollers 31a, 31b of each of the tensioning creels 30a, 30b, 30c are freely rotatable and are not driven. The third tensioning creel 30c is downstream of the first tensioning creel 30a with the second tensioning creel 30b located therebetween (in the running direction R).

(22) Referring now to FIG. 3, there is shown a view of the tensioning creels 30a, 30b, 30c of the apparatus 1 shown in FIG. 1. The tensioning rollers 31a, 31b, which are formed from acetal and have a smooth major circumferential surface, are cylindrical and each have a diameter ‘d’. The rotational axis of the second tensioning creel 30b is offset by a distance ‘a’ from a plane ‘P’ defined by the rotational axes of the first and third tensioning creels 30a, 30c. The rotational axis of the first tensioning creel 30a is spaced from the rotational axis of the third tensioning creel 30c by a distance ‘b’. The rotational axis of the second tensioning creel 30b is located an equal distance between the rotational axes of the first and third tensioning creels 30a, 30c. The first and second tensioning rollers 31a, 31b are located toward the periphery of the first tensioning creel 30a. The rotational axes of the first and second tensioning rollers 31a, 31b are located in the first tensioning creel 30a such that the rotational axis thereof is located in a plane defined by the rotational axes of the first and second tensioning rollers 31a, 31b. The rotational axes of the first and second tensioning rollers 31a, 31b are each spaced by a distance ‘c’ from the rotational axis of the first tensioning creel 30a. Although only the arrangement of the first and second tensioning rollers 31a, 31b on the first tensioning creel 30a is described it will be appreciated that first and second tensioning rollers 31a, 31b are similarly arranged on the second and third tensioning creels 30b, 30c, which will not therefore be described further herein.

(23) The above-described dimensions a, b, c and/or d may be selected in order to suit the specific type of fibre bundle 2 which is to be processed. Without wishing to be bound by any particular theory we believe that increasing the distance between any two points of contact between the fibre bundle 2 and the tensioning rollers 31a, 31b alters the amount of spreading of the fibre bundle 2. Moreover, increasing the distance between points of contact of the fibre bundle 2 and the tensioning rollers 31a, 31b beyond a threshold value may result in the spread filaments of the fibre bundle 2 coalescing back together, e.g. de-spreading. The dimensions a, b, c and/or d may be selected, for example, based at least in part on the profile (for example the cross-sectional profile) of a fibre bundle 2 to be processed and/or of the binder content and/or of the filament quantity and/or diameter within said fibre bundle 2.

(24) Referring now to FIGS. 4, 5 and 6, there is shown various views of the fluid flow apparatus 4 shown in FIGS. 1 and 2. The fluid flow apparatus 4 includes a housing 40 comprising a base 41, side walls 42, end walls 43 and a lid 44. One of the end walls 43 has a curved outer face 43a so that the fluid flow apparatus 4 may be located in close proximity to the take up reel 5. A fluid flow outlet 45 through the base 41 of the housing 40 is fluidly connected to a source of vacuum (not shown). The fluid flow apparatus 4 further includes a retention baton or member 46, fitted at both of its ends into opposed, vertical slots 47 in facing portions of the side walls 42 of the housing 40. The retention baton or member 46 is free to move toward and away from the fluid flow outlet 45 (vertically, in this embodiment) within the slots 47.

(25) The housing 40 has an open top which the lid 44 is configured to partially cover and to provide a partial seal thereagainst, thereby to provide a fluid flow inlet 48. The fluid flow inlet 48 is in fluid communication with the fluid flow outlet 45 thereby defining a fluid flow path F. The pressure and velocity of the fluid flow varies along the flow path F, with a relatively lower pressure and greater velocity toward the fluid flow outlet 45. The lid 44 is substantially flat and comprises a generally rectangular shape in plan with two triangular wings protruding from one side thereof. The lid 44 is configured to permit substantially free and unhindered passage of the fibre bundle 2 as it runs between the side walls 42 of the housing 40 and the lid 44. The inner surface 43b of the end walls 43 taper toward the fluid flow outlet 45 (as shown in FIG. 6). Conveniently the inner surface 43b of the end walls 43 may be curved from the inlet 48 to the outlet 45 or they may taper linearly. In any case, the cross sectional area of the aperture decreases in the direction of the fluid flow path, from the housing entrance 48. In embodiments the cross sectional area may reduce by over 50, 60 or 70%, for example from 50 to 90%, for example from 60 to 85%.

(26) The take up reel 5 is cylindrical and is connected to a motor (not shown) operable to drive rotation of the take up reel 5. Although the fluid flow apparatus 4 is shown as being spaced from the take up reel 5 in FIGS. 1 and 2 it will be appreciated that this spacing has been provided in order to more clearly show the apparatus 1 and that in practice the fluid flow apparatus 4 may be located directly adjacent the take up reel 5 (e.g. at a minimal distance therefrom).

(27) The apparatus 1 is prepared for use by feeding a free end of the fibre bundle 2 between the damping rollers 32a, 32b of the damping mechanism 32, over the first tensioning creel 30a, under the second tensioning creel 30b, over the third tensioning creel 30c, into the housing 40 of the fluid flow apparatus 4, under the retention baton or member 46, out of the housing 40 of the fluid flow apparatus 4 and onto the take up reel 5 to which the free end of the fibre bundle 2 is attached.

(28) In use, the fibre bundle 2 is drawn through the apparatus 1 in a running direction R via motor driven rotation of the take up reel 5, whilst the fibre bundle 2 is simultaneously supplied from the supply bobbin 20 via motor (not shown) driven rotation thereof. The fluid flow apparatus 4 is connected to a source of vacuum (not shown) and the third tensioning creel 30c is rotated in a clockwise direction (as shown by the arrow in FIG. 1) by a motor (not shown). In this way, at the point of contact between the fibre bundle 2 and a tensioning roller 31a, 31b of the third tensioning creel 30c, the third tensioning creel 30c is rotating in the running direction R of the fibre bundle 2.

(29) As the fibre bundle 2 is drawn through the apparatus 1 the first and second tensioning creels 30a, 30b and the tensioning rollers 31a, 31b of all of the tensioning creels 30a, 30b, 30c are caused to rotate due to frictional forces between the fibre bundle 2 and the outer surfaces of the tensioning rollers 31a, 31b. Alternatively, the first and/or second tensioning creels 30a, 30b may be rotated by a motor (not shown), for example where the first tensioning creel 30a is rotated in the same direction as the third tensioning creel 30c and/or the second tensioning creel 30b is rotated in the opposite direction. Without wishing to be bound by any particular theory we believe that fibre bundles 2 having a relatively higher percentage of binding agent and/or a type of binding agent configured to bind the filament fibres together relatively more strongly may be spread more effectively by driven rotation of more than just the third tensioning creel 30c.

(30) Referring now to FIG. 7, there is shown a view similar to that of FIG. 3 showing the tensioning creels 30a, 30b, 30c of the apparatus 1. In FIG. 7 each of the tensioning creels 30a, 30b, 30c have rotated by 90 degrees about their rotational axes relative to their orientation as shown in FIG. 3. Therefore, the rotational axes of the tension rollers 31a, 31b of each tensioning creel 30a, 30b, 30c have also moved, in this case such that the distance e between the rotational axis of the first tension roller 31a on the first tensioning creel 30a to the rotational axis of the second tensioning roller 31b on the second tensioning creel 30b is relatively reduced. Additionally, the distance f between the rotational axis of the second tensioning roller 31b on the second tensioning creel 30b and the first tensioning roller 31a on the third tensioning creel 30c is relatively reduced.

(31) In the orientation of tensioning rollers 31a, 31b shown in FIG. 3 the fibre bundle 2 path length through the tensioning apparatus 3 is decreased relative to the orientation of the tensioning rollers 31a, 31b shown in FIG. 3. Consequently, tension in the fibre bundle 2 relatively increases when the orientation of the tensioning rollers 31a, 31b moves towards the orientation shown in FIG. 3. The tension in the fibre bundle 2 relatively decreases when the orientation of the tensioning rollers 31a, 31b moves towards the orientation shown in FIG. 6.

(32) It will be appreciated by one skilled in the art that although only two orientations of tensioning rollers 31a, 31b are shown in FIGS. 3 and 7 the tensioning rollers 31a, 31b will, in use, pass through a sequence of continuously changing orientations as each of the tensioning creels 30a, 30b, 30c rotates. Furthermore, the orientations of tensioning rollers 31a, 31b shown in FIGS. 3 and 7 are for explanatory purposes only and it will be appreciated that, in practice, the tensioning rollers 31a, 31b may not in fact pass through the specific orientations which have been shown in FIGS. 3 and 7. Even further, it will be appreciated that the tensioning creels 30a, 30b, 30c may not all rotate at the same angular velocity and that therefore, although the tensioning creels 30a, 30b, 30c shown in FIG. 7 are described as having rotated by the same angle (i.e. 90 degrees), relative to the orientation shown in FIG. 3, this is for explanatory purposes only. Indeed, some of the tensioning creels 30a, 30b, 30c may not rotate at all once the apparatus 1 has entered a state of equilibrium, in use. For example, where tensioning creels 30a and/or 30b are not driven by a motor one or both of said tensioning creels 30a, 30b may not rotate when the apparatus is in equilibrium.

(33) By way of the above-described rotation of the tensioning creels 30a, 30b, 30c a tension in the fibre bundle 2 is intermittently caused to increase and decrease. Furthermore, the tensioning rollers 31a, 31b translate in the running direction R of the fibre bundle 2, for example such that the tensioning rollers both carry and tension the fibre bundle at the same time. Advantageously, it has been found that an apparatus provided with tensioning means (e.g. the tensioning rollers 31a, 31b) which translates in the running direction R of the fibre bundle 2 at least partially mitigates against damage to filament fibres within said fibre bundle 2. Moreover, provision of such a tensioning means which translates in the running direction R of the fibre bundle 2 provides for a greater degree of control over the variance of tension generated in the fibre bundle 2 compared with a system in which the tensioning means does not translate in the running direction R of said fibre bundle 2.

(34) The damping mechanism 32 prevents the fibre bundle 2 from being pulled back upstream towards the supply bobbin 20 whilst also mitigating, at least partially, any vibrations generated in the fibre bundle 2 by the intermittently increased and decreased tension generated therein. The damping mechanism 32 further acts as an orienting guide to the fibre bundle 2 towards the tensioning creels 30a, 30b, 30c.

(35) From the third tensioning creel 30c the fibre bundle 2 runs downstream to the fluid flow apparatus 4. When the tension in the fibre bundle 2 is relatively decreased that portion of the fibre bundle 2 within the fluid flow apparatus 4 is caused or allowed to move to or toward a lesser pressure and greater velocity of fluid flow within the flow path F, e.g. due to the effect of the air flow therethrough and/or due to the mass of the retention baton or member 46 acting against the fibre bundle 2. Consequently, the retention baton or member 46 freely moves, in concert with the fibre bundle 2, within the slots 47, toward the fluid flow outlet 45. That portion of the fibre bundle which is within the fluid flow apparatus 4 is spread, e.g. further spread, by the action of the air flowing therethrough and thereagainst.

(36) When the tension in the fibre bundle 2 is relatively increased, via the tensioning apparatus 3, the portion of the fibre bundle 2 within the fluid flow apparatus 4 is caused to move to or toward a greater pressure and lesser velocity of fluid flow within the flow path F, e.g. by being pulled via the relatively increased tension within the fibre bundle 2. The retention baton or member 46 is pulled toward the lid 44, in concert with the fibre bundle 2, within its slots 47. Without wishing to be bound by any particular theory it is believed that frictional forces between the surface of the retention baton or member 46 and the fibre bundle 2 substantially retains the fibre bundle 2 in its further spread width (e.g. at a greater width relative to the fibre bundle 2 width prior to its further spreading in the fluid flow apparatus 4). Furthermore, the retention baton or member 46 provides a smooth surface against and/or under which the fibre bundle 2 runs and/or is tensioned. Moreover, via pivoting against the retention baton or member 46 the fibre bundle 2 may be substantially free of the lid 44 when the fibre bundle 2 is a state of increased tension (via the tensioning apparatus). The retention baton or member 46 may therefore be considered to be a part of either or both the fluid flow apparatus 4 and the tensioning apparatus 3.

(37) The thus spread fibre bundle 2 then exits the fluid flow apparatus 4 and is collected on the take up reel 5, with, in some cases, a continuous release sheet (not shown) formed of paper, located between successive plies of spread fibres.

(38) Without wishing to be bound by any particular theory it is believed that there is a pressure differential within the fluid flow apparatus 4, which may be caused by the shape of the housing 40 and/or the ratio of the sizing of the fluid flow inlet 48 to the fluid flow outlet 45. Consequently, there the air flow in the flow path F has a relatively lesser pressure toward the fluid flow outlet 45. Consequently, the velocity of air flow in the fluid path F within the fluid flow apparatus 4 is relatively greater toward the fluid flow outlet 45. Hence, moving a portion of the fibre bundle 2 toward the fluid flow outlet 45 moves that part of the fibre bundle 2 into air flow in the flow path F having relatively greater velocity. This air flow advantageously acts to bend the filament fibres against which it acts prior to passing between said filament fibres. The passage of the air flow through the fibre bundle 2 acts to generate gaps between the filament fibres, thereby moving individual filament fibres perpendicular to their length (e.g. width wise) and consequently spreading the fibre bundle 2. Use of a fluid flow apparatus 4 advantageously minimises the generation of air-borne fibre bundle 2 waste matter because such matter is instead drawing through the fluid flow apparatus 4.

(39) Test Results

(40) Multiple fibre bundles 2, each comprising 12,000 continuous filament carbon fibres with a diameter of 7 μm each, bound by a binder, were spread using the above-described apparatus 1 and method.

(41) The fibre bundles 2 had an initial width W.sub.a of 7 mm, was spread to an intermediate width W.sub.i of 25 mm after running through the tensioning apparatus, before being spread to a final spread width W.sub.b of 70 mm after running through the fluid flow apparatus and being collected on the take up reel 5. The spread width W.sub.b has a ratio to the initial width W.sub.a of 10:1. The fibre bundles 2 have an average spread thickness Tb of 8.4 μm, which has a ratio to the diameter of individual filament fibres of 1.2:1 demonstrating that this simple apparatus is able to achieve a near monolayer spread.

(42) Provision of the fluid flow apparatus 4 downstream of the tensioning apparatus 3 has been found to be particularly beneficial. By running the fibre bundle 2 through the tensioning apparatus 3 prior to the fluid flow apparatus 4 said fibre bundle 2 is at least partially spread before entering the fluid flow apparatus 4. Without wishing to be bound by any particular theory it is believed that the binder in the fibre bundle 2 is at least partially broken and/or removed by passage through the tensioning apparatus 3. Therefore, when the fibre bundle 2 runs through the fluid flow apparatus 4 the fibre bundle 2 is more effectively spread and consequently is spread to a greater width (relative to a condition where the binder had not previously been at least partially broken and/or removed). Furthermore, it is believed that by at least partially pre-spreading the fibre bundle 2 prior to running it through the fluid flow apparatus 4 the effect thereof is enhanced.

(43) Referring now to FIG. 8, there are shown various suitable arrangements of tensioning rollers 31 on tensioning creels 30, with one, two, three, four, five or six tensioning rollers 31 provided on each tensioning creel 30. It will be appreciated by one skilled in the art that these arrangements are provided for illustrative purposes only and that the number and/or positioning of the tensioning rollers 31 on the creel 30 may vary from the arrangements shown.

(44) Referring now to FIGS. 9 and 10, there is shown an apparatus 11 for spreading fibres according to a second embodiment of the invention, wherein like references (identified by a preceding ‘1’) depict like features which will not be described herein further. The apparatus differs from the apparatus shown in FIGS. 1 and 2 in that it includes contact elements 6 and an accumulator 7 but does not include a fluid flow apparatus.

(45) The fibre bundle 12 comprises plural continuous glass fibres held together by a binder resin.

(46) The tensioning apparatus 13 differs from the tensioning apparatus 3 of the embodiment shown in FIGS. 1 and 2 in that it does not comprise a fluid flow apparatus 4. Furthermore, the apparatus 11 also includes a binder breaker 33 and a tensioner 34.

(47) The binder breaker 33, shown in FIGS. 11 and 12, includes a series of tension rolls 33a attached at their free ends to a housing 33b. The tension rolls 33a are formed from aluminium and are coated with PTFE in order to prevent damage to fibre bundle 12 as it is passed thereover. The tension rolls 33a are freely rotatable about their rotational axis and are arranged such that the fibre bundle 12 follows a tortuous path over and under successive tension rolls 33a. The binder breaker 33 further includes an orienting loop 33c which has a smooth and rounded inner surface and is located on an outer surface of the housing 33b.

(48) The tensioner 34 includes a hook or roll connected to a spring configured to bias the fibre bundle 2 in a direction which is generally orthogonal to its running direction R.

(49) The accumulator 7 includes a beam with guides 70 projecting orthogonally from its major surface, where the distance between the guides provides a constriction of a known width (transverse to the running direction R of the fibre bundle 2).

(50) The accumulator 7 is located downstream of the tensioning apparatus 13 and upstream of the take up reel 15. The tensioner 34 is located upstream of the tensioning creels 130a, 130b, 130c and downstream of the supply bobbin 120. The binder breaker 33 is located upstream of the tensioner 34 and downstream of the supply bobbin 120.

(51) The contact elements 6 comprise microfibre fabric 60. The microfibre fabric 60 is located on and around the outer surfaces of each of the tensioning rollers 131a, 131b. In an embodiment each of the rollers 131a, 131b (being those supported on each of the creels 130a, 130b, 130c) are provided with microfibre fabric 60. In other, albeit less preferred embodiments, at least some of the rollers 131a, 131b on one or more creels 130a, 130b, 130c will be provided with microfiber fabric 60.

(52) As shown in FIG. 13, the microfibre fabric 60 comprises a multitude of protruding fibres 61 which project generally orthogonally from the main surface 62 of the microfibre fabric 60. The protruding fibres 61 are generally oriented in a similar direction, referred to as the nap of the microfibre fabric (shown in FIG. 11 by arrow N). The microfibre fabric 60 is oriented on each of the tensioning rollers 131a, 131b such that its nap is facing a direction opposite to the running direction R of the fibre bundle 12. An image of the microfibre fabric 60 is shown in FIG. 14 where the protruding fibres 61 protrude from a main surface 62 by approximately 1 mm. In this embodiment the protruding fibres 61 are grouped together in plural bundles although one skilled in the art will appreciate that this need not be the case.

(53) The apparatus 11 is prepared for use by feeding a free end of the fibre bundle 12 from the supply bobbin 120 through the orienting loop 33c and along the tortuous path between the tension rolls 33a of the binder breaker 33, back around the supply bobbin 120 and then under the hook or roll of the tensioner 34, over the first creel 130a, under the second creel 130b, over the third creel 130c, through the accumulator 7 and onto the take up reel 15 to which the free end of the fibre bundle 12 is attached.

(54) In use, the fibre bundle 12 is drawn through the apparatus 11 in a running direction R via motor driven rotation of the take up reel 15 (as described above), whilst the fibre bundle 2 is simultaneously supplied from the supply bobbin 120 via motor (not shown) driven rotation thereof. All three creels 130a, 130b, 130c are rotationally driven by a motor (not shown). The first and third creels 130a, 130c are driven in a different (e.g. a clockwise) direction to the second creel 130b (e.g. which is driven in an anticlockwise direction). The tensioning rollers 131a, 131b, which may freely rotate about their rotational axes, intermittently contact the fibre bundle 12 in the manner described above. Without wishing to be bound by any theory we have found that it is particularly advantageous that the microfibre fabric 60, located around the tensioning rollers 131a, 131b, moves in the same direction as the running direction R of the fibre bundle 12 because this relatively reduces damage to the filament fibres within the fibre bundle 12 (compared to movement opposed to the running direction R of the fibre bundle 12).

(55) The intermittently increased and decreased tension generated in the fibre bundle 12 by the tensioning apparatus 13, spreads the fibre bundle 12 as described above in relation to the embodiment shown in FIGS. 1 and 2. In addition, the protruding fibres 61 of the microfibre fabric 60 act to further spread the fibre bundle 12.

(56) Passage of the fibre bundle 12 through the binder breaker 33 advantageously breaks (or at least begins to break) the binder which initially binds the individual fibres of the fibre bundle 12 together. Additionally, passage through the binder breaker 33 provides an additional tensioning of the fibre bundle 12. The tensioner 34 enhances and/or maintains tension in the fibre bundle 12. The tensioner 34 may maintain a minimum level of tension in the fibre bundle 12. Without wishing to be bound by any particular theory it is believed that breaking the binder (or beginning to break the binder) via the above-described mechanical system produces a fibre bundle 12 having filament fibres with improved (e.g. less reduced) physical and/or mechanical properties compared to fibre bundles 12 in which the binder is broken via pyrolysis. Post-pyrolysis fibres are commonly more fragile and susceptible to breaking. Furthermore, the above-described mechanically generated breaking of the binder does not negatively impact the environment, in contrast to the breaking of the binder through the use of solvents, which are detrimental to the environment.

(57) Without wishing to be bound by any particular theory it is believed that the protruding fibres 61 of the microfibre fabric 60 press against, and in some cases through, the fibre bundle 12 as it runs thereover (as shown in FIG. 15). In this way the protruding fibres 61 of the microfibre fabric 60 advantageously separate adjacent fibres of the fibre bundle 12 and consequently spread, e.g. further spread, said fibre bundle 12. Without wishing to be bound by any theory we believe that orientation of the nap N of the microfibre fabric 60 in a direction opposite to the running direction R of the fibre bundle 12 at least partially enhances the effect of the microfibre fabric 60 thereagainst.

(58) The fibre bundle 12, which may be in an overly spread state (i.e. spread beyond a desired level of spread—for example beyond an ideal monolayer), passes through the constriction of the accumulator 7 which guides the fibre bundle 12 into a reduced or desired spread width W.sub.b. The spread fibre bundle 12 is then collected on the take up roller 15, preferably with a paper release sheet (not shown) thereunder. The accumulator 7 may act to mitigate gaps between adjacent glass fibres.

(59) Test Results

(60) Multiple fibre bundles 12 of glass fibres each having a diameter of 24 μm, bound by a binder of epoxy resin at 0.5% w/w, were spread using the above-described apparatus 11 and method. The take up reel 15 was driven to rotate at an angular velocity of 3 rpm, whilst the first, second and third tensioning creels 130a, 130b, 130c were, respectively, driven to rotate at angular velocities of 70, 40 and 80 rpm.

(61) Averaged results from processing of the multiple fibre bundles 12 revealed that the fibre bundles 12 had an initial width W.sub.a of 4.09 mm, and a final spread width W.sub.b of 25.54 mm after running through the accumulator 7 and being collected on the take up reel 15. The spread width has a ratio to the initial width of 6.24:1. However, due to the presence of binder and the physical condition of the fibre bundle the bundles to be spread are not an idealised fibre bundle with each fibre close-packed with adjacent fibres. Indeed, each fibre had a diameter of 24 μm which lead to a ratio of average spread thickness Tb to the diameter of individual filament fibres of less than 2:1, meaning that the spread fibre bundle was at or approaching an idealised ‘monolayer’. The results are shown in FIG. 16.

(62) In a comparative test, where no microfiber was provided on the tensioning creels the maximum fibre spread was about 3 times, clearly demonstrating the efficacy of the microfibers.

(63) Tensile Testing

(64) Fibre bundle 12 spread by the above described apparatus 11 was cut to form 30 samples each of 50 mm length. Additionally, fibre bundle 12 as supplied (i.e. without being spread) was cut to firm samples of 500 length each. Each sample was then individually tested to failure at room temperature using an Instron 5566 tensile testing machine with a crosshead speed of 0.2 mm/min.

(65) Result: The average peak load for non-spread fibre bundle 12 was found to be 984 N, whilst the average peak load for the spread fibre bundle 12 was found to be 878 N. The spread fibre bundle 12 therefore demonstrates a reduced tensile strength relative to non-spread fibre bundle 12, with the difference being on average 106 N or a decrease of 12%. The difference in tensile strength between the spread and non-spread fibre bundle 12 was therefore found to be negligible. Without wishing to be bound by any particular theory it is believed that the non-spread fibre bundle 12 has a relatively higher tensile strength at least in part due to twisting and tangling within the non-spread fibre bundle 12 (which are untwisted and/or untangled during spreading). When a fibre of a non-spread fibre bundle 12 breaks the free, broken ends may become entangled amongst adjacent twisted fibres thereby at least partially preventing retraction of said broken ends from the non-spread fibre bundle 12. Consequently, the broken thread of the non-spread fibre bundle 12 may continue to provide a partial resistance against a tensile load. In contrast, a broken fibre in a spread fibre bundle 12 has a substantially reduced probability of entanglement amongst adjacent fibres and consequently the broken fibre may not provide a partial resistance against a tensile load. Consequently, it has been found that spreading fibre bundle according to the invention results in spread fibre bundle 12 with minimal damage and reduced mechanical properties.

(66) As will be appreciated, features of each of the above embodiments may be combined within a single apparatus for spreading fibres. For example, it is quite conceivable that any of the above-described features and/or the following features may be included in or with the first embodiment of the present invention: an accumulator 7, contact elements 6, a binder breaker 33 and/or a tensioner 34.

(67) It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, although a vacuum source (e.g. a source of negative pressure) has been described this need not be the case and the fluid flow apparatus 4 may additionally or alternatively comprise one or more sources of positive pressure. Additionally or alternatively, although the fluid is described as air in the above embodiments this need not be the case, and additionally or alternatively the fluid may be water or any other suitable fluid.

(68) Additionally or alternatively, the tensioning apparatus 3, 13 may comprise more than three tensioning creels 30a, 30b, 30c, 130a, 130b, 130c, for example four, five, six, seven, or more tensioning creels. Where more than three tensioning creels are provided, some, none or all of the additional tensioning creels may be rotationally driven by a motor. Additionally or alternatively, each of the tensioning creels 30a, 30b, 30c, 130a, 130b, 130c may comprise only one tensioning roller 31a, 31b, 131a, 131b or may comprise more than two tensioning rollers 31a, 31b, 131a, 131b (for example, as shown in FIG. 8). Where more than two tensioning rollers 31a, 31b, 131a, 131b are provided on one, some or all of the tensioning creels 30a, 30b, 30c, 130a, 130b, 130c the tensioning rollers 31a, 31b, 131a, 131b may be arranged in any suitable orientation about the rotational axis of each tensioning creel 30a, 30b, 30c, 130a, 130b, 130c. Additionally or alternatively, the tensioning rollers 31a, 31b, 131a, 131b need not be formed from acetal but may instead by formed from any suitable substance, for example a plastic or a metal, or a metal or other material coated with a plastic or any other suitable coating.

(69) Additionally or alternatively, although the slots 47 of the fluid flow apparatus 4 are described above as vertical they need not be and may instead have any other suitable orientation. Additionally or alternatively, the slots 47 may define a curve or arc, at least in one or more part of their length. Additionally or alternatively, the retention baton or member 46 may be biased by a biasing means, e.g. a spring, toward or away from the fluid flow outlet 45 within the slots 47. Additionally or alternatively, the retention baton or member 46 may be driven or drivable, e.g. by an actuator, toward or away from the fluid flow outlet 45 within the slots 47.

(70) Additionally or alternatively, although only one fluid flow apparatus 4 is described in relation to the embodiment shown in FIGS. 1 and 2 this need not be the case and instead any suitable number of fluid flow apparatus 4 may be provided. Furthermore, where more than one fluid flow apparatus 4 is provided, the additional fluid flow apparatus may be provided at the same or a similar location in the apparatus 1 or may be located in alternative locations, for example upstream of the tensioning apparatus 3.

(71) Additionally or alternatively, although only one accumulator is shown in the embodiment shown in FIGS. 8 and 9 this need not be the case and instead any suitable number of accumulators may be provided, for example 2, 3, 4 or more. Where more than one accumulator is provided the apparatus 11 may further include a tensioning arm located between each accumulator, where the tensioning arm may be configured to maintain or retain a tension in the fibre bundle 12.

(72) Additionally or alternatively, the apparatus 1, 11 may include one or more measuring apparatus, which may be located downstream of the tensioning apparatus and/or downstream of the fluid flow apparatus (where provided) or at any suitable location. The measuring apparatus may be configured to measure one or more parameters of the fibre bundle 2, 12, for example the width or thickness thereof.

(73) Additionally or alternatively, although the fibre bundle 2 described above in relation to the embodiments shown in FIGS. 1 and 2 is described as including plural continuous carbon fibres this need not be the case and instead the fibre bundle 2 may include any suitable type of fibres, for example, glass fibres, ceramic fibres, aromatic polyamide fibres or any combination thereof (with or without carbon fibres). Additionally or alternatively, although the fibre bundle 12 described above in relation to the embodiments shown in FIGS. 8 and 9 is described as including plural continuous glass fibres this need not be the case and instead the fibre bundle 2 may include any suitable type of fibres, for example, carbon fibres, ceramic fibres, aromatic polyamide fibres or any combination thereof (with or without glass fibres).

(74) It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.