GB2492594A - Tow placement apparatus and method - Google Patents

Abstract

A tow placement head for forming a variable angle tow composite structure comprises a pinch arrangement 8,102 to receive a tow tape and pass it to a compaction shoe 9 to press it against a surface on which the tow tape is to be laid. Shear deformation is applied to a portion of the tow tape between the compaction shoe and the pinch arrangement. The pinch arrangement may be immovable relative to the compaction shoe, the compaction shoe allowing tow tape to slide over its surface which may comprise PEEK or high molecular weight polyethylene. Alternatively, this may be achieved by allowing movement between the pinch arrangement and the compaction shoe and or between the pinch arrangement and the tow material adhered to the surface. An abutment surface 91 of the compaction shoe 9 may have a fixed angular relationship to the pinch region or may be rotatable relative to the pinch region. The placement head may include a tow tape cutter, width regulator and/or a backing member collector. An endless backing member may be provided. The pinch arrangement may inhibit movement of tape across its width, and may comprise abutting shoes or an abutting shoe and roller.

Description

Title: Tow Placement Apparatus and Methods Descrintion of Invention Embodiments of the present invention relate to a composite material tow placement apparatus and methods. Specifically embodiments of the present application relate to composite material tow placement apparatus for the manufacturing of the composite materials with variable fibre orientation.

Composite materials are used in many industries to produce lightweight and strong structures with advantageous stiffness properties. Composite materials comprise a matrix material forming a matrix holding elongate reinforcement elements. The matrix material is typically formed from a thermosetting resin and the reinforcement elements are typically carbon fibres -although other matrix materials and reinforcement elements may be used.

Many structures formed from composite materials are formed using tapes or tows of substantially parallel carbon fibres. The tape or tow may be pre-impregnated with the matrix material or the matrix material may be added at a later juncture. In particular, the tapes or tows are laid on a mould structure in layers. The laid-up mould structure is then heated, for example in an autoclave, under pressure to polymerise the matrix material and form a substantially rigid structure corresponding with the mould structure in shape.

A conventional tow placement apparatus may comprise a tow source arranged with respect to a tow placement head. Elongate reinforcement elements are, in this example, pre-impregnated with a resin matrix material. The elongate reinforcement elements forming the tow extend from the tow source to the tow placement head. The tow placement head presses the elongate reinforcement elements and resin matrix material against the mould structure -to adhere the tow to the mould structure. Substantially parallel lines of the tow can be laid onto the mould structure by moving the head in a controlled manner along shifted or parallel paths across the mould structure -the tow being cut at the end of each path.

Tows are easily laid on simple flat mould structures using straight lines of tow laid adjacent each other. More complex non-flat mould structures can also be used -in which case a series of tow placement heads which are moveable with respect to each other or a tow placement head having a profile which mirrors the profile of the mould structure may be used.

Advantageous structures are achieved by the careful control of the positioning of the reinforcement elements on the mould structure. Ideally, the reinforcement elements are evenly spaced from each other and parallel to each other. This is comparatively easily achieved using conventional techniques where the reinforcement elements are laid along substantially straight paths. However, since conventional tow placement techniques use in-plane bending deformation of the reinforcement elements by rotating the tow placement head and keeping the axis of a compaction roller of the tow placement head perpendicular to the tow laying direction, process-induced defects such as localised fibre buckling and resin pocket are inevitably caused.

For the formation of some structures it is desired to lay reinforcement elements along paths which include curves. In such structures the angle of the tow path with respect to an axis of the structure is varied; thus, techniques to achieve such structures may be referred to as variable angle tow techniques.

Differences between the tow paths and the actual path of the reinforcement elements in those tows cause structural defects in the resulting structure.

Different methods are used to achieve variable angle tow paths which each suffer from similar structural defects when implemented using conventional techniques. For example, one such method is a shifting method in which adjacent tows are laid having a substantially identical shape but offset from each along a predetermined reference direction. Another such method is a parallel method in which each tow is laid roughly parallel to the adjacent tow path.

As will be appreciated, tow paths following a parallel laying method will inevitably cause the localised fibre buckling and resin pockets on the inside of the curved tow paths, although there are no overlaps. However, parallel methods are not widely used because the radius of curvature of the tow path needs to be reduced towards the inside of the curvature, which means there is a limitation on the plate size which can be produced. The tow paths following a shifting method to make a variable angle tow composite structure will inevitably include overlaps in which a first tow following a variable angle path will overlap over a length with an adjacent tow, causing the localised defects due to the in-plane bending deformation of the tow element. To avoid excessive overlap, a tow may be cut. The overlapping tows represent structural defects as do areas adjacent the cut ends of the tows -as these do not include any reinforcement elements and are rich in matrix material Examples of conventional tow placement techniques resulting in in-plane bending deformation of the tow element can be found in 7. Gurdal and B.F.

Tatting, "Tow-placement technology and fabrication issues for laminated composite structures," AIAA 2005-2017, 461h AIAA/ASME/ASCE/AHS!ASC Structure, Structural Dynamics & Materials Conference, 16-21 April 2005, Austin, Texas; B.F. Tatting and Z. Gurdal, Design and manufacture of elastically tailored tow placed plates," NASA Technical Report NASA/CR- 2002-211919, 2002; and D.C. Jegley, B.F. Tatting and Z. Gurdal, "Automated finite element analysis of elastically-tailored plates," NASA Technical Report NASA/CR-2003-21 2679, 2003, for example.

Other structural defects occur, for example, because of the reinforcement fibre buckling on the inner part of a tow path curve, movement of the reinforcement elements, and matrix material rich regions between the tows on a curve of the tow.

Other tow laying techniques, such as an embroidery based techniques suffer from similar problems which are compounded by the use of irregular stitching to hold the reinforcement elements to a backing felt, flexibility of the backing felt, and movement of the reinforcement elements due to tension within the stitches used to hold the reinforcement elements to the backing felt.

US6453962 discloses an apparatus which is used to form pre-impregnated tow material. In accordance with the teachings of this prior art document, a pair of pinch rollers are provided upstream in the direction of movement of the reinforcement elements of a pair of combination rollers which are configured to press resin matrix material against the elongate reinforcement elements (to combine the two materials). The pinch rollers are configured to move with respect to the combination rollers to alter the angle of the part of the elongate reinforcement fibres between the pinch and combination rollers with respect to the part of the reinforcement fibres held by the combination rollers. The document provides no teachings regarding the laying of the resulting tow on a mould structure and the teachings are, therefore, irrelevant to arrangements and techniques for laying the resulting tow -the disclosed apparatus being unsuitable for such a purpose. In addition, complex arrangements are required in order to alleviate issues concerning slack in the reinforcement elements as a result of varying roller rotational rate requirements.

Furthermore, the fixed width of the combination and pinch rollers limits the degree of wave which can be achieved in pre-impregnated material produced using this apparatus. In addition, there is no means disclosed to allow each tow path within a structure to have a different angle variation with respect to a reference axis.

Embodiments of the presently claimed invention seek to ameliorate one or

more problems associated with the prior art.

An aspect of the present invention provides a tow placement head member to lay a tow tape comprising reinforcement fibres and a matrix or binder material, the tow placement head member being for use in the formation of a variable angle tow composite structure and comprising: a pinch arrangement configured to receive a tow tape and to allow the tow tape to pass therethrough; and a compaction shoe configured to receive tow tape from the pinch arrangement and to press the tow tape against a surface on which the tow tape is to be laid, wherein the pinch arrangement is configured to apply shear deformation to a portion of the tow tape between the compaction shoe and the pinch arrangement.

The pinch arrangement may be moveable with respect to the compaction shoe.

The pinch arrangement may be immoveable with respect to the compaction shoe and the compaction shoe is configured to permit the tow tape to slide over a surface thereof.

The pinch arrangement may be configured to inhibit movement of the tow tape across a width of the pinch arrangement.

The pinch arrangement may include a pair of shoes resiliently biased towards abutment with each other.

The pinch arrangement may comprises a tow feed roller and a tow feed shoe configured to guide the tow tape towards the compaction shoe.

The member may further comprise a tow tape.

The matrix or binder material of the tow tape may be a thermoplastic or thermoset resin material.

The member may further comprise a heating element and an adhesion roller configured to form the tow tape by impregnating reinforcement fibres with a matrix or binder material.

The member may further comprise a tow width control arrangement configured to adjust a width of the tow tape.

The member may further comprise a backing member collection arrangement configured to receive a backing member from the tow tape.

The member may further comprise an endless backing member configured to receive matrix or binder material from a source of matrix or binder material and deliver the matrix or binder material to the compaction shoe.

The member may further comprise a matrix or binder material nozzle configured to receive matrix or binder material from the source of matrix or binder material and to deliver the matrix or binder material to the endless backing member.

The member may further comprise a cutting arrangement configured to cut the tow tape.

The cutting arrangement may comprise a support member and a cutting member configured to move between an extended and a retracted position with respect to the compaction shoe.

The cutting member may be configured for movement with respect to the support member.

Another aspect of the present invention provides a tow laying arrangement comprising a member as above.

The tow laying arrangement may further comprise a plurality of such members.

Another aspect of the present invention provides a method of laying a tow tape on a surface, the method comprising: providing a pinch arrangement and a compaction shoe; passing a first portion of a tow tape through the pinch arrangement;providing a compaction shoe; receiving the first portion of the tow tape from the pinch arrangement and pressing the first portion of the tow tape against a surface using the compaction shoe; applying shear deformation to a second portion of the tow tape, the second portion of the tow tape being between the compaction shoe and the pinch arrangement; and pressing the second portion of the tow tape against the surface using the compaction shoe.

The method may further comprise applying shear deformation to a third portion of the tow tape, the third portion of the tow tape being between the compaction shoe and the pinch arrangement; and pressing the third portion of the tow tape against the surface using the compaction shoe.

Embodiments of the present invention are described herein, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a schematic view of elements of an embodiment; Figure 2 shows a schematic view of a tow placement head member of an embodiment; Figure 3 shows a schematic view of a part of an embodiment; Figure 4 shows a portion of a compaction shoe of an embodiment; Figure 5 shows resin material used by embodiments; Figure 6 shows a schematic of a tow width control arrangement of an embodiment; Figures 7 to 9 show the operation of a cutting arrangement of an embodiment; Figures 10 and 11 show elements of embodiments; Figure 12 shows a schematic view of motors of embodiments; Figure 13 shows a tow laying arrangement of an embodiment; and Figure 14 shows a schematic view of elements of another example of the embodiment.

With reference to figure 1, an embodiment comprises a tow laying arrangement 1. The tow laying arrangement 1 includes, in this embodiment, a tow placement head member 2 coupled to a tow source coupling arrangement 3 and a resin source coupling arrangement 4. In an embodiment, the tow source coupling arrangement 3 and resin source coupling arrangement 4 form part of the tow placement head member 2. In an embodiment, the tow source coupling arrangement 3 and/or the resin source coupling arrangement 4 are remote from the tow placement head member 2 (as schematically shown in figure 1).

The tow source coupling arrangement 3 is configured to receive a tow source 5. The tow source 5 may, for example, comprise a spool of tow material 51 such as a plurality of elongate reinforcement elements. The reinforcement elements may comprise carbon fibres.

The resin source coupling arrangement 4 is configured to receive a resin source 7. The resin source 7 may comprise a spool of a resin material 71 in the form of a film of resin material 711 adhered to a backing member 712 (see figure 5). The film of resin material 711 and backing member 712, therefore, form a resin tape. Removal of the backing member 712 of the resin tape from the film of resin material 711 reveals an adhesive resin material surface 713 which can be used to adhere the film of resin material 711 to, for example, a surface 13 of a mould structure 14.

It will be understood that various different matrix materials may be used in accordance with embodiments of which a resin material 71 is just one example. It will be further understood that embodiments of the present invention could use a binder material instead of a matrix material (such as a resin material 71) which is intended to hold the re-enforcement fibres of the tow material 51 with respect to each other only temporarily. The binder material may also be a resin material. Impregnation of the tow material 51 with a binder material may be termed partial impregnation".

The tow source coupling arrangement 3 and the resin source coupling arrangement 4 are configured to provide tow material 51 and resin material 71 to the tow placement head member 2, or a part thereof. The tow placement head member 2 is arranged, in an embodiment, to combine the tow material 51 and the resin material 71 to form a combined tow and resin material 714.

In an embodiment the tow material 51 and resin material 71 are combined in a part of the tow laying arrangement 1 which may be remote from the tow placement head member 2.

With reference to figure 2, the tow placement head member 2 may comprise, in an embodiment, a tow feed rollei 8, a compaction shoe 9, and a tow feed shoe 10 all of which are coupled to a main body 21 of the tow placement head member 2. In an embodiment, the tow placement head member 2 may further comprise a heating element 17 and an adhesion roller 18 which are both coupled to the main body 21 of the tow placement head member 2.

In an embodiment, the heating element 17 comprises a roller which is coupled to an electrical supply, wherein the supply of electricity to the roller causes the temperature of the roller to increase towards a predetermined temperature -the roller being configured for rotational movement with respect to the main body 21 of the tow placement head member 2.

A thermostat or other temperature regulation device (not shown) may be provided to regulate the temperature of the heating element 17 to a predetermined temperature. The heating element 17 may, in an embodiment, comprise a shoe instead of a roller, the shoe being fixed against rotation with respect to the main body 21 of the tow placement member 2. The predetermined temperature is preferable sufficient to cause the resin material 71 to soften and/or at least partially melt.

The adhesion roller 18 is positioned with respect to the heating element 17 such that material passing between the adhesion roller 18 and the heating element 17 is pressed by the adhesion roller 18 against a surface of the heating element 17 in operation of the tow placement head member 2.

Accordingly, in an embodiment, the adhesion roller 18 is mounted on a carriage 181 which is configured for rotation with respect to the main body 21 of the tow placement member 2. The carriage 181 may be secured to an axle 182 which is attached to the main body 21 of the tow placement member 2 and about which the carriage 181 may rotate with respect to the main body 21 of the tow placement member 2. In an embodiment, the carriage 181 is configured for linear movement with respect to the heating element 17.

In an embodiment, the adhesion roller 18 is spaced apart from the heating element 17 by a predetermined, fixed, distance.

The adhesion roller 18 is, in an embodiment, a fixed shoe which is rotationally immobile with respect to the carriage 181.

The adhesion roller 18 is, in an embodiment, resiliently biased towards abutment with the heating element 17. A resilient biasing arrangement (not shown) may be provided -such as a helically wound spring, a pneumatic actuator, a hydraulic actuator, or a magnetic arrangement -to provide this resilient biasing. The resilient biasing arrangement may act on the carriage 181.

The adhesion roller 18 and the heating element 17 are arranged with respect to the tow source 5 and the resin source 7 such that the adhesion roller 18 and the heating element 17 receive tow material 51 and resin material 71 from their respective sources 5,7. In operation of the tow placement head member 2, the resin material 71 passes over a surface of the heating element 17 and is guided by the heating element 17 towards the adhesion roller 18. The tow material 51 is guided towards the heating element 17 such that the tow material 51 contacts the resin material 71 guided by the heating element 17.

The arrangement of the adhesion roller 17 and heating element 18 is such that the passing of the tow material 51 and resin material 71 therebetween is permitted. The tow material 51 is pressed against and into the resin material 71 by the adhesion roller 18 and the heating element 17. Accordingly, combined tow and resin material 714 is formed.

In an embodiment, the tow feed roller 8 and tow feed shoe 10 are arranged to receive the combined tow and resin material 714 therebetween and to deliver the combined tow and resin material 714 towards the compaction shoe 9.

With reference to figure 3, the tow feed roller 8 may comprise a cylindrical roller mounted for rotation with respect to the main body 21 of the tow placement head member 2. The tow feed roller 8 may be mounted for rotation about a first axis which extends in a first direction relative to the main body 21 of the tow placement head member 2. The tow feed roller 8 has an outer circumferential surface which is configured to guide tow material 51 towards the compaction shoe 9.

In an embodiment, rotation of the tow feed roller 8 is driven by a tow feed roller motor 81 (see figure 12) which is mounted to the tow feed roller 8 by a first shaft; the tow feed roller motor 81 is configured to drive rotation of the first shaft and, therefore, the tow feed roller 8 to regulate the tension of the backing member 712 during operation of the embodiment. The first shaft may be coupled to the tow feed roller 8 through a plurality of gears and/or belts.

The tow feed shoe 10 is, in an embodiment, an elongate finger (see figure 3) which is arranged adjacent the tow feed roller 8. The tow feed shoe 10 has a proximal end 101 and a distal end 102 which oppose each other across a length of the tow feed shoe 10. In an embodiment, the tow feed shoe 10 is mounted to the main body 21 of the tow placement head member 2 such that the tow feed shoe 10 is rotatable with respect to the main body 21 of the tow placement head member 2 about a second axis which extends in the first direction (and which is generally parallel to the first axis). Accordingly, a shaft 106 may be provided which mounts the tow teed shoe 10 to the main body 21 of the tow placement head member 2 such that the tow feed shoe 10 is rotatable with respect to the main body 21 of the tow placement head member 2. The shaft 106 may be provided towards the distal end of the tow feed shoe 10. In an embodiment, the tow feed shoe 10 may be mounted for linear movement with respect to the main body 21 of the tow placement head member 2. The mounting may be such that the distal end 102 of the tow feed shoe 10 is resiliently biased into abutment against the tow feed roller 8.

The resilient biasing may be achieved, in an embodiment, through the use of a resilient biasing arrangement 105 which may take the form of a helically wound spring positioned to act on a part of the main body 21 of the tow placement head member 2 and the tow feed shoe 10, for example.

The region of the tow feed shoe 10 adjacent the distal end 102 thereof, in an embodiment, includes an inclined surface such that a depth of the tow feed shoe 10 decreases towards the extreme distal end 102 of the tow feed shoe 10. The inclined surface may be profiled to at least partially correspond with a degree of curvature of the tow feed roller 8.

The tow feed shoe 10 may be curved to improve clearance between the tow feed shoe 10 and the surface 13 of the mould 14. A curved tow feed shoe 10 may improve the ability of the tow placement head 2 to be used in relation to three dimensional mould surface.

The tow feed shoe 10 is arranged to direct the combined tow and resin material 714 towards the compaction shoe 9. The tow feed shoe 10 may be configured to direct the combined tow and resin material 714 along a surface of the tow feed shoe towards the distal end 102 thereof.

In an embodiment, the tow feed shoe 10 includes guiding protrusions (not shown) which define or partially define a channel through which the combined tow and resin material 714 is to travel. The guiding protrusions are separated across a width of the tow feed shoe 10 and are configured to hinder movement of the combined tow and resin material 714 sideways (i.e. perpendicular to the normal direction of travel) off the surface of the tow feed shoe 10 over which the combined tow and resin material 714 is travelling.

In an embodiment in which the resin source 7 comprises a source of resin material 71 in the form of a film of resin material 711 and a backing member 712, the tow feed shoe 10 is configured to direct the combined tow and resin material 714 towards the compaction shoe 9 such that the backing member 712 is immediately adjacent the tow feed shoe 10 between the film of resin material 711 and the tow feed shoe 10.

In an embodiment, the tow placement head member 2 further comprises a backing member collection roller 12 which is configured to collect the backing member 712 which has been separated from the film of resin material 711.

The backing member collection roller 12, in an embodiment, comprises a cylindrical roller which is driven about a third axis in a rotational manner (the third axis being, in an embodiment, parallel with the first and/or second axes).

The rate at which the backing member collection roller 12 collects the backing member 712 may, in an embodiment, be synchronised or substantially synchronised with the rate at which the resin source 7 delivers resin material 71. This synchronisation or substantial synchronisation may be achieved through a mechanical coupling which may include one or more gears and/or belts. In an embodiment, a backing member collection motor 124 may be provided to drive rotation of the backing member collection roller 12.

The backing member collection roller 12, the tow feed shoe 10, and the compaction shoe 9 are, in an embodiment, arranged such that, at the distal end 102 of the tow feed shoe 10, the backing member 712 is detached from the combined tow and resin material 714 and passes towards the backing member collection roller 12 in operation of the tow placement head member 2.

In an embodiment, a first and a second backing member drawing rollers 121,122 are provided. The first and second backing member drawing rollers 121,122 are coupled to the main body 21 of the tow placement head member 2 and configured for rotation with respect thereto about respective fourth and fifth axes -these axes being generally parallel to the first and/or second axes in an embodiment.

The first and second backing member drawing rollers 121,122 are configured to receive the detached backing member 712 from the tow feed shoe 10 and to pass the detached backing member 712 towards the backing member collection roller 12.

The first and second backing member drawing rollers 121,122 are positioned with respect to each other such that the detached backing member 712 passes, during operation of the tow placement head member 2, between the two rollers 121,122 and is drawn past a surface of each of the two rollers 121,122 byrotation ofthe rollers 121,122.

The first and second backing member drawing rollers 121,122 may be positioned such that surfaces of each of the two rollers 121,122 generally abut against each other when there is no backing member 712 therebetween. The first and second backing member drawing rollers 121,122 are, therefore, configured to draw the backing member 712 from the tow feed shoe 10 towards the backing member collection roller 12.

The first and second backing member drawing rollers 121,122 are coupled to a backing member drawing motor 123 which may be coupled to one or both of the first and the second backing member drawing rollers 121,122. The coupling may be through one or more gears and/or one or more belts.

It will be appreciated that the backing member drawing rollers 121,122 can be driven in a rotational manner such that the backing member 712 is drawn therebetween at a rate which is substantially independent of the quantity of backing member 712 which has been collected by the backing member collection roller 12.

In an embodiment, the backing member collection roller 12 is positioned such that a backing member 712 may be drawn, along with the film of resin material 711 adhered thereto, by the first and second backing member drawing rollers 121,122, around the extreme distal end 102 of the tow feed shoe 10 (on a first side 103 thereof). At the extreme distal end 102 of the tow feed shoe 10, the drawing of the backing member 712 around the distal end 102 of the tow feed shoe 10 aids in the separation of tow material 51 impregnated with the film of resin material 711 from the backing member 712. The film of resin material 711 and the tow material 51 are directed towards the compaction shoe 9 and the backing member 712 continues to be drawn (in operation of the tow placement head member 2) back towards the proximal end 101 of the tow feed shoe 10 on a second side 104 of the tow feed shoe 10 (the first 103 and second 104 sides of the tow feed shoe 10 opposing each other across a depth of the tow feed shoe 10).

Thus, in accordance with embodiments, the tow material 51 impregnated with the thin film of resin material 711 is directed by the tow feed roller S and the tow feed shoe 10 towards the compaction shoe 9.

The combined tow and resin material 714 passes, in operation, between the tow feed roller 8 and the tow feed shoe 10 and is compressed by the roller S and shoe 10. The region in which the tow feed roller 8 and tow feed shoe 10 compress the combined tow and resin material 714 is referred to herein as the pinch region 16.

It will be understood that the at least the distal end 102 of the tow feed shoe 10 and the tow feed roller 8 should, in an embodiment, include a surface formed of a material which is sufficiently elastically deformable in a radial direction to apply even pressure on the tow material 51 impregnated with the film of resin material 711 but still prevent substantial slippage of the combined tow and resin material 714 across a width of the tow feed roller S (and hence also to prevent substantial slippage across a width of the tow feed shoe 10.

The tow material 51 impregnated with the film of resin material 711 passes from the pinch region 16 towards the compaction shoe 9. The compaction shoe 9 is arranged with respect to the main body 21 of the tow placement head member 2 such that the compaction shoe 9 may be abutted against the surface 13.

The compaction shoe 9 (see figure 4) has a width which extends in a direction which is generally perpendicular to the direction of travel of the tow material 51 impregnated with the film of resin material 711 over the compaction shoe 9.

The compaction shoe 9 may be formed from or coated with a material with low friction coefficient and high wear resistance; this material may be polyether ether ketone or high molecular weight polyethylene -for example. The compaction shoe 9 may have a substantially rectangular cross-sectional shape (as depicted).

The compaction shoe 9 includes an abutment surface 91 which is configured for abutment against the surface 13 of a mould. The abutment surface 91 may be substantially flat (as depicted) or may be curved. The abutment surface 91 extends across all or part of a width of the compaction shoe 9.

The abutment surface 91 is formed from or coated in a material which does not adhere with the film of resin material 711. Thus, the tow material 51 impregnated with the film of resin material 711 which is directed towards the compaction shoe 9 in operation of the tow placement head member 2 is permitted to pass over the abutment surface 91 between the abutment surface 91 and the surface 13 of the mould.

In an embodiment, the compaction shoe 9 has a generally rectangular cross-section with a protrusion extending from a main body of the shoe 9 adjacent the abutment surface 91. The protrusion may be positioned so as to extend the abutment surface 91.

The compaction shoe 9 may be resiliently biased towards a first position such that abutment of an abutment surface 91 of the compaction shoe 9 against the surface 13 causes movement of the compaction shoe 9 in direction away from the first position against the biasing force. The resilient biasing of the compaction shoe 9 towards the first position may be achieved by the use of a resilient biasing arrangement 92 such as a helically wound spring positioned to act against a part of the main body 21 of the tow placement head member 2 and the compaction shoe 9. The resilient biasing of the compaction shoe 9 -if provided -may be used to control the force which the compaction shoe 9 applies to the surface 13 during operation. The force may be restricted to avoid damage to the tow tape 15.

The resilient biasing arrangement 92 may comprise a flexible part (not depicted) of the compaction shoe 9 which elastically deforms on abutment of the abutment surface 91 and the surface 13 of the mould. The flexible part of the compaction shoe 9 may be configured for elastic deformation in a plurality of axes. Accordingly, in an embodiment, the flexible part of the compaction shoe 9 permits the abutment surface 91 of the compaction shoe 9 to follow a generally uneven, non-planar surface 13 of a mould.

The compaction shoe 9 is configured such that the tow material 51 impregnated with the film of resin material 711 passes over the abutment surface 91 of the compaction shoe 9, between the surface 13 and the compaction shoe 9, in operation -as discussed above. The compaction shoe 9 presses the tow material 51 impregnated with the film of resin material 711 against the surface 13 such that the tow material 51 impregnated with the film of resin material 711 is adhered to the surface 13. In an embodiment, the adhesive resin material surface 713 of the tow material 51 impregnated with the film of resin material 711 is pressed against the surface 13 to provide adhesion between the tow tape 15 and the surface 13.

Thus, as will be appreciated, the compaction shoe 9 may be drawn across the surface 13 to lay tow tape 15 on the surface 13.

The resin material 71 and the tow material 51 may be drawn from their respective sources 7,5 by movement of the tow placement head member 2 with respect to the surface 13 and adhesion of the tow material 51 impregnated with the film of resin material 711 to the surface 13.

In addition, rotation of the tow feed roller 8 and/or the backing member drawing rollers 121,122 and/or the backing member collection roller 12 may also draw or contribute to the drawing of the tow material 51 and resin material 71 from their respective sources 7,5. In an embodiment, the backing member drawing rollers 121,122 and/or the backing member collection roller 12 provide the main force drawing the tow material 51 and resin material 71 from their respective sources 7,5.

In an embodiment, the abutment surface 91 of the compaction shoe 9 has a width which is greater than a width of the tow material 51 impregnated with the thin film of resin material 711 (the width of the abutment surface 91 of the compaction shoe 9 being generally perpendicular to the direction of travel of the tow material 51 impregnated with the thin film of resin material 711 with respect to the compaction shoe 9).

The tow material 51 impregnated with the thin film of resin material 711 is pressed by the compaction shoe 9 against the surface 13 such that the tow material 51 impregnated with the thin film of resin material 711 adheres to the surface 13. The force applied by the abutment surface 91 to the tow material 51 impregnated with the thin film of resin material 711 in the pressing action also assists in reducing wrinkles in the laid tow material 51 impregnated with the thin film of resin material 711 on the surface 13.

The abutment surface 91 of the compaction shoe 9 is configured, in an embodiment, to permit the tow material 51 impregnated with the thin film of resin material 711 to slide thereover in such that the tow material 51 impregnated with the thin film of resin material 711 is pressed against the surface 13 by a different part of the width of the abutment surface 91 of the compaction shoe 9. This action holds the adhered tow material 51 impregnated with the thin film of resin material 711 against the surface 13 but offsets the tow material 51 impregnated with the thin film of resin material 711 in the pinch region 16 with respect to the tow material 51 impregnated with the thin film of resin material 711 immediately adjacent the compaction shoe 9.

Thus, if the tow material 51 impregnated with the thin film of resin material 711 which is adhered to the surface 13 immediately adjacent the compaction shoe 9 extends along a first path, the tow material 51 impregnated with the thin film of resin material 711 between the compaction shoe 9 and the pinch region 16 extends along a second path which is at an angle with respect to the first tow path; however, as will be appreciated, the plurality of elongate reinforcement fibres of the tow material 51 will all be substantially parallel to each other in this section of the tow material 51 impregnated with the thin film of resin material 711.

The tow material 51 impregnated with the thin film of resin material 711 has, therefore, been subjected to shear deformation; this is shown diagrammatically in figures 6 and 7. In figure 10, a substantially straight tow path has been followed with little or no axial movement of the pinch region 16 with respect to the path of the tow material 51 impregnated with the film of resin material 711 adhered to the surface 13 immediately adjacent the compaction shoe 9 (axial movement being movement along a longitudinal axis of the pinch region 16 generally horizontal in the depiction in figures 10 and 11). In figure 11, a curve in the tow path is desired. Therefore, from the configuration shown in figure 10, the pinch region 16 has been moved axially with respect to the path of the tow material 51 impregnated with the film of resin material 711 adhered to the surface 13 immediately adjacent the compaction shoe 9. In this example, the compaction shoe 9 has also moved in unison with the pinch region 16. The tow material 51 impregnated with the film of resin material 711 has slid along a width of the abutment surface 91 of the compaction shoe 9 such that the tow material 51 impregnated with the film of resin material 711 now passes over a different, but overlapping, width of the abutment surface 91 of the compaction shoe 9. The tow material 51 impregnated with the film of resin material 711 is held from movement along the width of the pinch region 16 -by the tow feed roller 8 and the tow feed shoe 10. Therefore, shear deformation is induced in the tow material 51 impregnated with the film of resin material 711 between the compaction shoe 9 and pinch region 16.

In figures 10 and 11 the tow material 51 impregnated with the film of resin material 711 is shown by a schematic representation of the reinforcement elements therein. In figure 11 the paths of the reinforcement elements (in schematic form) beneath the compaction shoe 9 (as depicted) have been shown in phantom. The pivot line of the tow material 51 impregnated with the film of resin material 711 will depend on the form of the abutment surface 91 of the compaction shoe 9. In the schematic depiction in figure 11 this pivot line has been shown as aligned with the edge of the compaction shoe 9 adjacent the pinch region 16. This may not be the case.

Further movement of the compaction shoe 9 with respect to the surface 13 causes the abutment surface 91 of the compaction shoe 9 to move over the tow material 51 impregnated with the film of resin material 711 which extends along the second path. The tow material 51 impregnated with the film of resin material 711 is, therefore, adhered to the surface 13 following the second path.

The greater the offset between the position of the compaction shoe 9 with respect to the pinch region 16 the greater the angle between the first and second paths. Furthermore, as the angle between the first and second paths is increased, so a width of the tow material 51 impregnated with the film of resin material 711 will decrease -the elongate reinforcement fibres remain substantially parallel to each other and the tow material 51 becomes thicker as fibres move above or beneath other fibres in the tow material 51.

Therefore, it will be understood that curved tow paths may be achieved by continual variation of the offset between the positions of the compaction shoe 9 with respect to the pinch region 16.

The maintenance of the reinforcement elements substantially parallel to each other aids in the reduction of defects in the resulting composite structure.

Furthermore, the variation in the width of the tow material 51 impregnated with the film of resin material 711 dependent on the offset between the position of the compaction shoe 9 with respect to the pinch region 16 (and, hence, the angle of the second tow path with respect to the first tow path -as discussed above) allows tow material 51 impregnated with the film of resin material 711 to be laid in curved adjacent paths with minimal overlap or resin rich regions.

The reinforcement elements forming the tow material 51 may, in embodiments, split into narrower widths during the shearing operation of embodiments of the invention. This splitting reduces shear buckling of reinforcement elements which cross paths and, hence, the number of wrinkles in the laid tow tape 15.

It has been found that decreasing the distance between the abutment surface 91 of the compaction shoe 9 and the pinch region 9 has advantageous results in the form of reduced wrinkles in the laid tow tape 15. It has been found that a distance between the near edge of the abutment surface 91 of the compaction shoe 9 and the pinch region 16 of less than about 1mm is particularly advantageous. The distance (height in the depicted examples) between a plane of the abutment surface 91 and a parallel plane of the tow feed shoe 10 is, in an embodiment, between about 0.5mm and about 1mm.

It will be understood that embodiments can be used to achieve smoother thickness variations in resulting composite structures than would otherwise be achievable.

In an embodiment of the present invention, there may not be a separate source 5 of tow material 51 from the source 7 resin material 71. In particular, the tow material 51 may be pre-impregnated with the resin material 71. A source of this pre-impregnated tow material may be provided in the place of the source of resin material 7. The pre-impregnated tow material may also have a backing member adhered to one side thereof which may be removed to reveal an adhesive surface -much like examples of the resin material 71 discussed above. The pre-impregnated tow material is directed to the pinch region 16 in much the same manner as the resin material 71 in the above described embodiment. Other aspects of embodiments of the invention described above may be common to embodiments using the pre-impregnated tow material -as will be appreciated.

Embodiments of the present invention may be used to provide variable angle tow composites using the shifting technique discussed above with fewer defects than might otherwise be possible with prior apparatus. In addition, embodiments allow for greater angle variations than may otherwise be possible using prior techniques.

In an embodiment, there is a fixed angular relationship between the edge of the abutment surface 91 of the compaction shoe 9 adjacent the pinch region 16 and the tow feed shoe 10 and to feed roller 8.

In an embodiment, restricted rotational movement of the abutment surface 91 is permitted about an axis which is substantially perpendicular to the usual direction of travel of the tow tape 15 past the abutment surface 91 and which is generally parallel to a width of the tow tape 15 at the abutment surface 91 -such that the abutment surface 91 moves towards and/or away from the pinch region 16.

In an embodiment, restricted rotational movement of the abutment surface 91 is permitted about an axis which is substantially aligned with the usual direction of travel of the tow tape 15 past the abutment surface 91 -such that the abutment surface 91 moved from side-to-side with result to the pinch region 16.

In an embodiment, restricted rotational movement of the abutment surface 91 is permitted about an axis which is substantially perpendicular to the usual direction of travel of the tow tape 15 past the abutment surface 91 and which is generally parallel to a depth of the tow tape 15 at the abutment surface 91 -such that a first end of the abutment surface 91 may advance towards the pinch region 16 whilst a second end of the abutment surface 91 retreats from the pinch region 16, and vice versa.

In an embodiment the heating element 17 may comprise a semi-conductor heater with positive temperature coefficient that can self-regulate the surface temperature of the element 17.

It will be appreciated that the heating element 17 may be used to increase the flexibility of the materials being laid during the laying process.

In an embodiment, a tow width control arrangement 19 is provided (see figure 6). The tow width control arrangement 19 is configured to regulate the overall width of the combined tow and resin material 714 before the material 714 reaches the tow feed shoe 10 and tow feed roller 8 in use. The tow width control arrangement 19 may, therefore, be positioned adjacent the heating element 17. The tow width control arrangement 19 is, in an embodiment, coupled to the main body 21 of the tow placement head member 2.

In an embodiment, the tow width control arrangement 19 (see figures 2 and 6 for example) is positioned to receive combined tow and resin material 714 from the adhesion roller 18 and heating element 17. In an embodiment, the tow width control arrangement 19 is positioned to deliver combined tow and resin material 714, of regulated width, to the tow feed shoe 10 and tow feed roller 8.

In an embodiment, the tow width control arrangement 19 comprises a boom 191 from which extends a pair of adjustable members 192. Each of the pair of adjustable members 192 extend from the boom 191 towards the combined tow and resin material 714. A regulated width is defined between each of the pair of adjustable members 192.

The pair of adjustable members 192 is configured to guide outer edges of the combined tow and resin material 714 towards each other by abutment therewith. As the combined tow and resin material 714 has been heated by the heating element 17, the material 714 is malleable and parts of the material 714 may be moved with respect to the backing member 712-e.g. slid over a surface of the backing member 712. Thus, the combined tow and resin material 714 may be manipulated to regulate the width of the material 714 on the backing member 712.

In an embodiment, a tow cutting device 20 comprising a support member 201 and a cutting member 202 is provided (see figures 7-9). The support member 201 and cutting member 202 comprise a cutting arrangement. The cutting member 202 is coupled to the support member 201 for movement therewith in a first direction between a first and a second position. The first position of the support member 201 is in an extended position such that a support pad 203 of the support member 201 projects beyond a plane of the abutment surface 91 in the direction of the surface 13 of the mould 14 in operation -see figures 8 and 9. The second position of the support member 201 is a retracted position such that the support pad 203 does not project beyond the plane of the abutment surface 19 -see figure 7.

The cutting member 202 is configured for movement with respect to the support member 201 in a second direction between a first and a second position. In an embodiment, the second direction is generally parallel to the direction of movement of the tow material 51 impregnated with the film of resin material 711 at the compaction shoe 9. In the first cutting member position, the cutting member 202 is spaced apart from the support pad 203 of the support member 201 (see figure 8). In the second cutting member position, the cutting member 202 abuts the support pad 203 of the support member 201 (see figure 9). The first cutting member position is, in an embodiment, therefore, a stowed position and the second cutting member position is, in an embodiment, therefore a cutting position.

Therefore, to cut the tow material 51 impregnated with the film of resin material 711, the main body 21 of the tow placement head member 2 may be moved away from the surface 13 of the mould 14. The support member 201 (and cutting member 202) may be moved from the first to the second support member position. The tow material 51 impregnated with the film of resin material 711 extends from the surface 13 to which it is adhered to the pinch region 16. The cutting member 202 is then moved from the first cutting member position to the second cutting member position. The cutting member 202 cuts the tow material 51 impregnated with the film of resin material 711 against the support pad 203. The cutting member 202 and support member 201 may subsequently be returned to their respective first positions.

In an embodiment, an endless backing member 712 is provided -see figure 14. In accordance with this embodiment, which is otherwise substantially similar to the above described embodiments, the backing member collection roller 12 of previous embodiments is replaced with a resin nozzle 23 coupled to the resin source 7. The resin nozzle 23 directs resin from the resin source 7 to the endless backing member 712 to coat a portion of the endless backing member 711 with a thin film of resin material 711. The coated portion of the endless backing member 712 is directed to the heating element 17 and the adhesion roller 18 -at which combined tow and resin material 714 is produced (generally as discussed above).

The resin material in this embodiment is a sticky resin material. The resin source 7 may comprise a source of powder resin or B-staged resin. The resin nozzle 23 may include a resin heating element configured to heat resin material from the resin source prior to the delivery of the resin material to the surface of the portion of the endless backing member 712.

In an embodiment, the tow laying arrangement 1 includes a plurality of tow placement head members 2 as described herein (see figure 13). The plurality of tow placement head members 2 may be configured in an array so as to lay respective tow tapes 15 of tow material impregnated with the thin film of resin material 711 onto the surface 13 with each tow tape 15 being adjacent another of the tow tapes 15. The distance between any two tow placement head members 2 may be controllable independently of the distance between another two tow placement head members 2 such that multiple tow tapes 15 may be laid with different tow paths at the same time.

In an embodiment, the tow feed roller 8 and the tow feed shoe 10 are moveable with respect to the compaction shoe 9 along an axis which is generally perpendicular to the direction of travel of the tow tape 15 therethrough such that the pinch region 16 moves with respect to the compaction shoe 9 to impart shear deformation to the tow material 51 impregnated with the thin film of resin material 711 therebetween.

In an embodiment, the tow feed roller 8 and the tow feed shoe 10 are moveable (with respect to the compaction shoe 9) in unison such that the pinch region 16 moves with respect to the compaction shoe 9 to impart shear deformation to the tow material 51 impregnated with the thin film of resin material 711 therebetween.

Accordingly, an offset is achieved between the path of the tow material 51 impregnated with the thin film of resin material 711 adhered to the surface 13 immediately adjacent the compaction shoe 9 and the tow material 51 impregnated with the thin film of resin material 711 immediately adjacent the pinch region 16. Movement of the compaction shoe 9 relative to the relative to the surface 13 to cause the abutment surface 91 of the compaction shoe 9 to apply a force to the tow material 51 impregnated with the thin film of resin material 711 which is between the compaction shoe 9 and the pinch region 16 causes this part of the tow material 51 impregnated with the thin film of resin material 711 along a new tow path to be adhered to the surface 13. Thus, it will be appreciated that much the same effect is achieved to one or more of the embodiments discussed above.

The tow feed roller S and the tow feed shoe 10 form a pinch region 16 as discussed above in accordance with embodiments of the present invention.

The pinch region 16 may, in accordance with embodiments, be defined by other pinch arrangements which serve to hold the tow material 51 impregnated with the thin film of resin material 711 therebetween and to prevent substantial axial movement of the tow material 51 impregnated with the thin film of resin material 711 with respect to the pinch arrangement so that shear deformation of the tow material 51 impregnated with the thin film of resin material 711 between the compaction shoe 9 and the pinch region 16 can be generated by movement of the pinch region 16 with respect to the compaction shoe 9 and/or movement of the pinch region 16 with respect to the tow material 51 impregnated with the thin film of resin material 711 adhered to the surface 13 immediately adjacent the compaction shoe 9 (the movement being generally perpendicular to the direction of travel of the tow material 51 impregnated with the thin film of resin material 711 through the pinch region 16).

As used herein a tow tape 15 comprises reinforcement fibres and a matrix material such as tow material 51 impregnated with the thin film of resin material 711. References to the film of resin material 711 should be construed as references to a matrix material unless otherwise stated.

It will be appreciated that, in embodiments, one or more re-direction rollers 22 are provided to redirect the path of the backing member 712, the tow material 51, the resin material 71, and/or the tow material 51 impregnated with the thin file of resin 711.

It will be appreciated that, in accordance with embodiments, the tow placement head member 2 may comprise an impregnation arrangement 6 (to form the combined tow and resin material 714), a shear deformation inducing arrangement (to induce shear deformation on tow material 51 impregnated with the film of resin material 711 prior to adhesion to a surface 13 of a mould 14), a tow width control arrangement 19, and a tow cutting device 20 -see figures 1 and 13.

In an embodiment, the compaction shoe 9 comprises a roller configured for rotation about an axis.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (1)

1. <claim-text>CLAIMS: 1. A tow placement head member to lay a tow tape comprising reinforcement fibres and a matrix or binder material, the tow placement head member being for use in the formation of a variable angle tow composite structure and comprising: a pinch arrangement configured to receive a tow tape and to allow the tow tape to pass therethrough; and a compaction shoe configured to receive tow tape from the pinch arrangement and to press the tow tape against a surface on which the tow tape is to be laid, wherein the pinch arrangement is configured apply shear deformation to a portion of the tow tape between the compaction shoe and the pinch arrangement.</claim-text> <claim-text>2. A member according to claim 1, wherein the pinch arrangement is immoveable with respect to the compaction shoe and the compaction shoe is configured to permit the tow tape to slide over a surface thereof.</claim-text> <claim-text>3. A member according to claim 1, wherein the pinch arrangement is moveable with respect to the compaction shoe.</claim-text> <claim-text>4. A member according to any preceding claim wherein the pinch arrangement is configured to inhibit movement of the tow tape across a width of the pinch arrangement.</claim-text> <claim-text>5. A member according to any preceding claim, wherein the pinch arrangement includes a pair of shoes resiliently biased towards abutment with each other.</claim-text> <claim-text>6. A member according any of claims 1 to 4, wherein the pinch arrangement comprises a tow feed roller and a tow feed shoe configured to guide the tow tape towards the compaction shoe.</claim-text> <claim-text>7. A member according to any preceding claim, further comprising the tow tape.</claim-text> <claim-text>8. A member according to claim 7, wherein the matrix or binder material of the tow tape is a thermoplastic or thermoset resin material.</claim-text> <claim-text>9. A member according to any preceding claim further comprising a heating element and an adhesion roller configured to form the tow tape by impregnating reinforcement fibres with a matrix or binder material.</claim-text> <claim-text>10. A member according to any preceding claim, further comprising a tow width control arrangement configured to adjust a width of the tow tape.</claim-text> <claim-text>11. A member according to any preceding claim, further comprising a backing member collection arrangement configured to receive a backing member from the tow tape.</claim-text> <claim-text>12. A member according to any of claims 1 to 10, further comprising an endless backing member configured to receive matrix or binder material from a source of matrix or binder material and deliver the matrix or binder material to the compaction shoe.</claim-text> <claim-text>13. A member according to claim 12, further comprising a matrix or binder material nozzle configured to receive matrix or binder material from the source of matrix or binder material and to deliver the matrix or binder material to the endless backing member.</claim-text> <claim-text>14. A member according to any preceding claim, further comprising a cutting arrangement configured to cut the tow tape.</claim-text> <claim-text>15. A member according to claim 14, wherein the cutting arrangement comprises a support member and a cutting member configured to move between an extended and a retracted position with respect to the compaction shoe.</claim-text> <claim-text>16. A member according to claim 15, wherein the cutting member is configured for movement with respect to the support member.</claim-text> <claim-text>17. A tow laying arrangement comprising a member according to any preceding claim.</claim-text> <claim-text>18. The tow laying arrangement according to claim 17, further comprising a plurality of members according to any of claims 1 to 16.</claim-text> <claim-text>19. A method of laying a tow tape on a surface, the method comprising: providing a pinch arrangement and a compaction shoe; passing a first portion of a tow tape through the pinch arrangement; providing a compaction shoe; receiving the first portion of the tow tape from the pinch arrangement and pressing the first portion of the tow tape against a surface using the compaction shoe; applying shear deformation to a second portion of the tow tape, the second portion of the tow tape being between the compaction shoe and the pinch arrangement; and pressing the second portion of the tow tape against the surface using the compaction shoe.</claim-text> <claim-text>20. A method according to claim 19, further comprising applying shear deformation to a third portion of the tow tape, the third portion of the tow tape being between the compaction shoe and the pinch arrangement; and pressing the third portion of the tow tape against the surface using the compaction shoe.</claim-text> <claim-text>21. A tow placement head member substantially as herein described with reference to the accompanying drawings.</claim-text> <claim-text>22. A tow laying arrangement substantially as herein described with reference to the accompanying drawings.</claim-text> <claim-text>23. A method substantially as herein described with reference to the accompanying drawings.</claim-text> <claim-text>24. Any novel feature or combination of novel features disclosed herein.</claim-text>