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Title:
WOVEN COMPOSITE MADE BY ADDITIVE MANUFACTURING
Document Type and Number:
WIPO Patent Application WO/2019/092217
Kind Code:
A1
Abstract:
A 3D-printed, woven composite material is formed from a continuous filament. The woven material may comprise two sets of parallel segments formed from the same continuous filament, wherein the parallel segments of the first set cross the parallel segments of the second set in an under-over pattern. A unit cell of the pattern may comprise N segments of the first set and M segments of the second set, and if segment n 1 of the first set crosses segment m of the second set and segment n 2 of the first set crosses more segments of the second set than segment n 1 , segment n 2 may also cross segment m for all n 1 ,n 2 ∈ N and all ∈ M. A method and apparatus for producing such a woven composite material are also disclosed.

Inventors:
DOWLING, Denis (National University of IrelandBelfield, Dublin 4, IE)
DICKSON, Andrew (National University of IrelandBelfield, Dublin 4, IE)
Application Number:
EP2018/080834
Publication Date:
May 16, 2019
Filing Date:
November 09, 2018
Export Citation:
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Assignee:
UNIVERSITY COLLEGE DUBLIN, NATIONAL UNIVERSITY OF IRELAND (Belfield, Dublin 4, IE)
International Classes:
B33Y10/00; B29C64/141; B29C70/22; B29C70/38; B32B5/02; B32B5/26; B33Y30/00; D03D15/02; D03D25/00; B32B27/34
Domestic Patent References:
WO2017100783A12017-06-15
Foreign References:
US20170015060A12017-01-19
US20170246814A12017-08-31
Download PDF:
Claims:
CLAIMS

1 . A 3D-printed, woven composite material formed from a continuous filament. 2. The 3D-printed, woven material of claim 1 wherein the woven material comprises two sets of parallel segments formed from the same continuous filament, and wherein the parallel segments of the first set cross the parallel segments of the second set.

3 . A 3D-printed, woven composite material comprising:

a first set of parallel segments; and

a second set of parallel segments, segments of the second set being arranged to cross segments of the first set in an over-under pattern, and

wherein a unit cell of the pattern comprises N segments of the first set and M segments of the second set, and wherein if segment nj of the first set crosses over segment m of the second set and segment n2 of the first set crosses over more segments of the second set than segment n segment n2 also crosses over segment m for all n n2 E N and all m E M.

4. The 3D-printed, woven composite material of any preceding claim wherein the filament comprises a fibre with a binder coated or impregnated thereon, and wherein optionally the binder is a polymeric matrix material, and wherein optionally the fibre is a carbon fibre yarn, glass fibre, or Kevlar.

5. The 3D-printed, woven material of any of claims 2 to 4 wherein a weave spacing of adj acent segments of at least one set is selected such that the binder joins one segment to the adj acent segment without a gap therebetween.

6. The 3D-printed, woven material of any of claims 2 to 4 wherein a weave spacing of segments in the woven material is selected so as to produce a porous structure with gaps between adj acent filament segments.

7. The 3D-printed, woven material of any preceding claim wherein the material has at least one of an aperture therethrough and a cavity therein, the aperture or cavity passing through a plane of the woven material. 8. The 3D-printed, woven material of claim 7 as it depends on any of claims 2 to 6 wherein the segments are diverted away from being parallel in the region of the aperture or cavity so as to form the aperture or cavity.

9. The 3D-printed, woven material of any preceding claim wherein the material has a regular, repeating weave pattern.

10. The 3D-printed, woven material of claim 9 as dependent on claim 7 or claim 8, wherein the filament is / the segments are diverted away from the regular, repeating weave pattern in the vicinity of the cavity or aperture.

1 1. The 3D-printed, woven material of any of claims 2 to 10 wherein a plurality of segments of the first set each pass under one or more segments of the second set and over one or more segments of the second set and a plurality of segments of the second set each pass under one or more segments of the first set and over one or more segments of the first set.

12. The 3D-printed, woven material of any of claims 2 to 1 1 wherein each set of segments comprises two or more subsets of segments with a gap between segments of adjacent subsets being greater than a spacing between adjacent segments of one subset. 13. The 3D-printed, woven material of claim 12 wherein all segments of each subset of the first set each pass under one or more segments of the second set and over one or more segments of the second set and all segments of each subset of the second set each pass under one or more segments of the first set and over one or more segments of the first set. 14. The 3D-printed, woven material of claim 12 or claim 13 wherein the gap between adjacent subsets is filled by one or more flyer segments, the flyer segments optionally being present in only a single plane.

15. The 3D-printed, woven material of any preceding claim wherein the material comprises only one continuous filament, the continuous filament forming all segments of the material.

16. A method of making a composite material comprising using a 3D printing system to lay a continuous filament along a path so as to weave a structure. 17. The method of claim 16 comprising extruding the continuous filament from a nozzle of the 3D printing system to form the weave directly, without any movement or rearrangement of the filament being needed to obtain the weave.

18. The method of claim 16 or claim 17, the weaving a structure comprising:

extruding the continuous filament from a nozzle of the 3D printing system to form a first set of parallel segments, and a second set of parallel segments, segments of the second set being arranged to cross segments of the first set in an over-under pattern.

19. The method of claim 18, wherein the extruding the continuous filament from the nozzle is arranged to form a regular pattern comprising a repeating unit cell, and wherein the extruding comprises alternating between extruding one or more segments of the first set and one or more segments of the second set to build up each unit cell.

20. A method of making a composite material comprising using a 3D printing system to lay a continuous filament along a path, the method comprising extruding the continuous filament from a nozzle of the 3D printing system to form a first set of parallel segments, and a second set of parallel segments, segments of the second set being arranged to cross segments of the first set in an over- under pattern. 21. The method of any of claims 16 to 21 wherein the filament comprises a fibre with a binder coated or impregnated thereon.

22. The method of claim 21 wherein the binder is a polymeric matrix material and the method comprises heating the filament so as to melt the binder prior to laying the filament.

23. The method of any of claims 16 to 22 wherein the path is selected so as to weave a structure with at least one of an aperture therethrough and a cavity therein, the structure being at least substantially planar and the aperture or cavity passing through a plane of the woven structure. 24. The method of claim 23 wherein the aperture or cavity is formed without breaking the continuous filament.

25. The method of claim 23 or claim 24 wherein the aperture or cavity is formed by directing the path around the intended aperture location.

26. The method of any of claims 16 to 25 comprising selecting a weave spacing of filament segments in the woven material so as to produce a porous composite with gaps between adjacent filament segments. 27. The method of any of claims 16 to 26 wherein laying the continuous filament comprises:

(i) printing a first set of conjoined parallel segments of the filament;

(ii) printing a second set of conjoined parallel segments of the filament, wherein the parallel segments of the second set cross the parallel segments of the preceding set; and

(iii) repeating steps (i) and (ii),

and wherein each set is joined to the preceding set such that the filament is unbroken.

28. The method of any of claims 16 to 27, further comprising arranging the path so as to accommodate one or more sensors and/or tags within the structure.

29. An apparatus arranged to make a 3D-printed, woven composite material formed from a continuous filament, the apparatus comprising:

a forming surface;

a 3D printing head arranged to have the continuous filament extruded therefrom and being movable in a direction perpendicular to the forming surface and biased towards the forming surface such that the 3D printing head can move away from the forming surface to move over one or more segments of the continuous filament already present on the forming surface and back towards the forming surface when no such segments are present; and

a control system arranged to cause the 3D printing head to extrude:

a first set of parallel segments; and

a second set of parallel segments, segments of the second set crossing segments of the first set in an over-under pattern.

30. The apparatus of claim 29, wherein the apparatus does not include any tool or device for moving segments of the continuous filament once extruded.

Description:
WOVEN COMPOSITE MADE BY ADDITIVE MANUFACTURING

The invention relates to a method and system for manufacturing a woven composite material and to the material formed. More specifically, the material may be formed by 3D printing. In particular, but not exclusively, the material formed may be manufactured so as to have apertures in desired locations, without compromising material strength.

In the prior art, loom fabricated and tailor pathed composite preforms are known. These are then impregnated with a resin to hold the fibres together. Figure 1 shows two examples 100 of prior art composites.

The top image 1 10 shows a Laystitch net preform prior to resin infusion (non-woven, made from a continuous fibre). A close-up image 1 10a illustrating how Laystitch works is also provided - sewing type machines are used to stitch a fibre into place on a fabric backing sheet. Laystitch is a non- woven process and relies on a polymer matrix for inter-layer interaction. The bottom image 120 shows the current standard for complex part production; cutting of parts from a large loom-produced carbon fibre sheet (woven, discontinuous fibres).

US 2016/0305051 Al discloses a method for producing 'interlaced' composites by 3D printing, with two arrays of depositing heads. One array (a weft inserter) lays multiple (discontinuous) weft filaments, the other array (warp heads) lays multiple (discontinuous) warp filaments crossing the weft filaments at an angle.

The standard definition of "woven" is used herein - fabric or a fabric item formed by interlacing long threads passing in one direction with others at an angle (often a right angle) to them. In US 2016/0305051 Al , the warp heads move relative to each other between weft insertions to control the weave geometry - the separate warps and wefts are laid in stages, so allowing an under-over pattern to be formed. The interlaced composite of US 2016/0305051 Al is therefore a woven composite material.

According to a first aspect of the invention, there is provided a 3D-printed, woven composite material formed from a continuous filament.

As used herein, "woven" means having filament segments of a first set passing in one direction with filament segments of a second set at an angle (often a right angle) to them, the filaments being arranged so as to form an under-over structure. At least some, and in many embodiments the majority, of deposited segments are deposited on multiple planes in a single pass of a printing head or nozzle to form the under-over structure. The skilled person will appreciate that forming a woven material by 3 D printing a single continuous filament infers limitations on the woven material itself, as only certain weave patterns, like those disclosed herein, allow the formation of an under-over pattern from a single printed filament, and in particular without requiring any lifting, bending or other movement of the deposited filament between its deposition and the setting or curing of the composite material.

The skilled person will appreciate that embodiments disclosed herein allow the continuous filament to be deposited on multiple planes on each pass of a printing head or nozzle, so forming an under- over structure of crossing segments of the same continuous filament - i.e. a woven structure is built up using only a single filament to provide both "warp" and "weft" segments.

The 3D-printed, woven material of the first aspect may comprise two sets of parallel segments formed from the same continuous filament. The parallel segments of the first set may cross the parallel segments of the second set, optionally at a right angle thereto.

According to a second aspect, there is provided a 3D-printed, woven composite material comprising: a first set of parallel segments; and

a second set of parallel segments, segments of the second set being arranged to cross segments of the first set in an over-under pattern, and

wherein a unit cell of the pattern comprises N segments of the first set and M segments of the second set, and wherein if segment nj of the first set crosses over segment m of the second set and segment n 2 of the first set crosses over more segments of the second set than segment n segment n 2 also crosses over segment m for all n n 2 £ i and all m £ M. In embodiments in which the pattern is a repeating pattern, the unit cell repeats across the woven composite. The unit cell is a repeating unit that makes up the repeating pattern, and may for example be square or rectangular. In embodiments in which the pattern is not a repeating pattern, the unit cell may correspond to the entire woven composite. The skilled person will appreciate that such a weave pattern may allow the composite material to be formed from a continuous filament.

In some embodiments, N≥M>2, and optionally >3. In some embodiments, N and M may be equal. The over-under pattern may be a repeating over-under pattern. In such embodiments, each unit cell of the repeating pattern may comprise N segments of the first set and M segments of the second set. In such embodiments, adj acent segments of the first set within the unit cell may be labelled n 1 .... n N in order. The number of segments of the second set passed over by each segment of the first set may increase from n } to n N , optionally linearly. For example, in embodiments in which N=M, n t may cross over one fewer segment of the second set than n i+1 , and correspondingly may pass under one more segment of the second set than n i+1 .

The segments may be provided by conjoined parts of a 3D printed filament. The skilled person will appreciate that the woven composite material may be cut after it is formed, so cutting the filament / separating the filament into two or more separate filaments.

Advantageously, the skilled person will appreciate that embodiments of the invention may provide benefits relative to prior art techniques in that shape can be tailored for individual parts and irregularities or features such as apertures, cavities, slots and shaped edges can be produced with little, if any, disruption to the process or change to the apparatus. The invention may provide particular advantages in composite materials that include any 'irregularity' compared to, or deviation from, a block or sheet or panel. Further, as the composite material is created by 3D printing, with no loom (in which a comb-like device is often used to push fibres together) or movement of the filament once extruded from the print head, fibre crimp may be reduced as compared to various prior art techniques.

The skilled person will appreciate that there is a wide range of potential applications for such tailorable composite materials. Applications may include:

• Brackets and fittings (e.g. for aerospace applications);

• Bicycle frames;

• Light weight frames (e.g. for drone or light aircraft applications);

• Composite structural inserts for joint reinforcement;

· Composite scarf repairs;

• Composite fastening inserts;

• Internal medical fixations;

• Stent devices; and

• Bespoke repair patches.

The filament may comprise a fibre with a binder coated or impregnated thereon.

The binder may be a polymeric matrix material. The fibre may be a reinforcing fibre, such as carbon fibre yarn, glass fibre, Kevlar ® , basalt, jute, bamboo or nylon fibre.

The woven material may comprise multiple sets of parallel, or approximately parallel, segments formed from the same continuous filament. Segments of one set may cross the segments of the preceding set. The segments may cross at an angle of around 90 ° . A weave spacing of adjacent filament segments of at least one set may be selected such that the binder joins one segment to the adjacent segment without a gap therebetween. A weave spacing of filament segments in the woven structure of at least one set may be selected so as to produce a porous structure with gaps between adjacent filament segments.

The woven material may have at least one aperture therethrough. The woven material may have a cavity therein.

The woven material may have multiple apertures and/or cavities.

Segments of the filament may be diverted away from their course, for example away from being parallel and/or away from a regular, repeating pattern, in the region of the aperture or cavity so as to form the aperture or cavity.

The woven composite material may be at least substantially planar (e.g. a sheet), and one or more apertures and/or cavities may pass through a plane of the woven composite material.

The aperture or cavity may have a width of at least the breadth of the filament, and optionally may have a width of 2 to 20 times the breadth of the filament.

The 3D-printed, woven material may have a regular, repeating weave pattern.

In embodiments with a cavity and/or an aperture, the filament / the segments may be diverted away from the regular, repeating weave pattern in the vicinity of the cavity or aperture.

A plurality of segments of the first set may each pass under one or more segments of the second set and over one or more segments of the second set.

A plurality of segments of the second set may each pass under one or more segments of the first set and over one or more segments of the first set. Each set of segments may comprise two or more subsets of segments with a gap between segments of adjacent subsets being greater than a spacing between adjacent segments of one subset.

All segments of each subset of the first set may each pass under one or more segments of the second set and over one or more segments of the second set and all segments of each subset of the second set may each pass under one or more segments of the first set and over one or more segments of the first set.

In embodiments with a gap between adjacent subsets, the gap may be filled by one or more flyer segments, the flyer segments optionally being present in only a single plane. The flyer segments may pass either: under all segments of the other set; or over all other segments of the other set.

The 3D-printed, woven material may comprise only one continuous filament, the continuous filament forming all segments of the material. The 3D-printed, woven material may consist of the one continuous filament, and optionally a binder.

According to a third aspect of the invention, there is provided a method of making a composite material comprising using a 3D printing system to lay a continuous filament along a path so as to weave a structure.

The method may comprise extruding the continuous filament from a nozzle of the 3D printing system to form the weave directly, without any movement or rearrangement of the filament being needed to obtain the weave. The weaving the structure may comprise:

extruding the continuous filament from a nozzle of the 3D printing system to form a first set of parallel segments, and a second set of parallel segments, segments of the second set being arranged to cross segments of the first set in an over-under pattern. The extruding the continuous filament from the nozzle may be arranged to form a regular pattern comprising a repeating unit cell. The extruding may comprise alternating between extruding one or more segments of the first set and one or more segments of the second set to build up each unit cell.

According to a fourth aspect of the invention, there is provided method of making a woven composite material comprising using a 3D printing system to lay a continuous filament along a path, the method comprising extruding the continuous filament from a nozzle of the 3D printing system to form a first set of parallel segments, and a second set of parallel segments, segments of the second set being arranged to cross segments of the first set in an over-under pattern. The under-over pattern may be as described in the second aspect.

The method may comprise extruding the continuous filament from a nozzle of the 3D printing system, without any movement or rearrangement of the filament being needed to obtain the woven material. The filament may comprise a fibre with a binder coated or impregnated thereon.

The binder may be a polymeric matrix material. The method may comprise heating the filament so as to melt the binder prior to laying the filament.

The path may be selected so as to weave a structure with at least one of an aperture therethrough and a cavity therein.

The aperture or cavity may be formed without breaking the continuous filament.

The aperture or cavity may be formed by diverting the continuous filament around the intended aperture or cavity location.

The aperture or cavity is formed by directing the path around the intended aperture location.

The method may comprise selecting a weave spacing of filament segments in the woven structure so as to produce a porous composite with gaps between adjacent filament segments.

The laying the continuous filament may comprise:

(i) printing a first set of conjoined parallel segments of the filament;

(ii) printing a second set of conjoined parallel segments of the filament, wherein the parallel segments of the second set cross the parallel segments of the preceding set; and

(iii) repeating steps (i) and (ii).

Each set may be joined to the preceding set such that the filament is unbroken.

According to a fifth aspect of the invention, there is provided an apparatus arranged to make a 3D- printed, woven composite material formed from a continuous filament. The apparatus comprises: a forming surface;

a 3D printing head arranged to have the continuous filament extruded therefrom and being movable in a direction perpendicular to the forming surface and biased towards the forming surface such that the 3D printing head can move away from the forming surface to move over one or more segments of the continuous filament already present on the forming surface and back towards the forming surface when no such segments are present; and

a control system arranged to cause the 3D printing head to extrude:

a first set of parallel segments; and

a second set of parallel segments, segments of the second set crossing segments of the first set in an over-under pattern. The apparatus may not include any tool or device for moving segments of the continuous filament once extruded.

The under-over pattern may be as described in the second aspect.

The control system may be arranged to move the printing head in only one plane, that plane optionally being parallel to the forming surface. Movement perpendicular to the forming surface may not be influenced or controlled by the control system, but rather only by the biasing means and interactions between the printing head and already-laid segments or other obstacles on the forming surface.

The skilled person will appreciate that, whilst tailored fibre placement has been adopted by several industries (e.g. aerospace), fibre path generation is generally a lengthy process, based upon modelling of the required parts under theoretical loading conditions with Finite Element Analysis (FEA). This leads to parts being expensive compared with loom woven composites. Loom woven laminates offer a more general purpose product with more isotropic mechanical properties, making them usable in a wider range of situations. Loom woven laminates are typically produced in large pieces and sold in large quantities. The user then cuts these sheets to suit the part and the cut parts are assembled using adhesive or fasteners. There has been little work performed on a hybrid system that can encompass benefits of both production methods. The 3D printing system in combination with a fibre/polymer filament, as disclosed herein, provides the capability to combine these two methods.

Embodiments of the invention include and can produce net shape woven structures (main body) and tailored pathing for features (holes and cavities) in a single process. Tailored structures can be produced for a wider range of products. These structures may exhibit increased mechanical reliability and lower waste material, translating to lower cost.

The skilled person will appreciate that features described with respect to one embodiment may be applied to any other embodiment as appropriate, mutatis mutandis.

There now follows by way of example only a detailed description of embodiments of the present invention with reference to the accompanying drawings in which: Figure 1 (PRIOR ART) shows two prior art composite materials;

Figure 2A shows a woven composite material of an embodiment of the invention;

Figure 2B shows a close-up of a portion of the woven composite material of Figure 2A; Figure 3 is a schematic illustration of a path for a filament suitable for producing the woven composite material shown in Figures 2A and 2B;

Figure 4 shows a loosely woven composite material of another embodiment of the invention;

Figure 5 shows the manufacture of a woven composite material of another embodiment of the invention;

Figure 6 shows the finished woven composite material of Figure 5 ;

Figure 7A is a schematic illustration of a path for a filament suitable for producing a woven composite material with an aperture therethrough;

Figure 7B shows a woven composite material made using the filament path of Figure 7A;

Figure 8 shows a woven composite material like that in Figure 7B but with a smaller aperture;

Figure 9A shows a woven composite material of another embodiment, with an aperture;

Figure 9B shows the manufacture of a woven composite material of an equivalent embodiment to that of Figure 9A, but without an aperture;

Figure 10A shows the woven composites of Figures 9A and 9B alongside a third woven composite equivalent to that of Figure 9A, but with a smaller aperture;

Figure 10B illustrates the results of tensile strength tests performed on the three woven composites shown in Figure 10A;

Figure 11A shows a woven composite of another embodiment;

Figure 11B shows a close-up of a portion of the woven composite of Figure 1 1A, with a fastener inserted through the aperture;

Figure 11C shows a close-up of a portion of another woven composite, with a fastener inserted through the aperture;

Figure 12 is a schematic illustration of a path for a filament suitable for producing the woven composite material of Figure 9A; Figure 13 is a schematic illustration of a method of an embodiment; Figure 14 is a schematic illustration of another method of an embodiment;

Figure 15A shows a woven composite with an embedded chip;

Figure 15B shows a woven composite with a partially embedded sensor; Figure 15C shows a woven composite with a fastener;

Figure 16A shows a schematic plan view of a woven composite of an embodiment alongside cross-sectional views in two different locations; Figure 16B shows the schematic plan view of the woven composite of Figure 16A with an order of deposition of the segments marked;

Figure 16C shows a schematic plan view of the woven composite of Figure 16A at four different printing stages;

Figure 16D shows a schematic plan view of a different woven composite from that shown in Figure 16A;

Figure 16E shows a schematic plan view of a different, less regular, woven composite from that shown in Figure 16A;

Figure 17 shows an image of a woven composite similar to that shown schematically in Figure 16A, with a different unit cell size; Figure 18 shows schematic cross-sectional views of a woven composite at two stages during printing; and

Figure 19 shows an image of a cross-section of a stacked woven composite. In the figures, like reference numerals are used for like features.

Figure 4 shows a loose-weave composite material 400 in accordance with an embodiment of the invention. Simple manual programming was employed to create the simple woven structure 400 shown in Figure 4. A continuous filament 401 , also referred to as the fibre 401 , or yarn 401 , is used to make the woven composite material of this embodiment. In the embodiment being described, the fibre 401 is a pre- impregnated carbon fibre yarn, in this case having a Nylon 66 matrix as a construction material (procured from Markforged™). The skilled person will appreciate that other reinforcing fibres 401 could be used in other embodiments.

In this embodiment, the woven material 400 was manufactured by passing the yarn 401 through a heated nozzle so as to melt the polymer and allow the yarn 401 to be formed into the desired shape. The yarn 401 can therefore be said to have been 3D printed, as the nozzle acts as a 3D printer, building up the woven structure by laying the yarn 401 in place along a path / printing the yarn 401 in a weave pattern. The polymer around the yarn 401 is then cooled and sets, holding the yarn 401 in place.

The skilled person will appreciate that the weave produced differs from what is known in the textile space as a plain weave, as a fibre row always remains outside the woven structure (i.e. without any part of the fibre overlapping it). Such a fibre row may be referred to as a "flyer". The skilled person will appreciate that the fibre row(s) outside of the woven structure are generally the last rows printed by the 3D printer (uppermost rows, if the material is in the horizontal plane as shown). A CNC printing system may be used.

This pathing therefore does not utilise the standard Weft- Warp configuration (over-under knitting technique) and allows the same filament 401 to be used to form the entire structure. No movement or rearrangement of any printed segment of the fibre is required to form the weave. Further, the entire structure is arranged to be formed using a single nozzle / printing head.

The skilled person would appreciate that is possible to stack these layers or rows of the yarn 401 indefinitely so as to form parts of any shape and thickness (not possible with loom woven or laystitched methods), as is illustrated in Figure 19 and discussed in more detail below.

In the embodiment shown in Figure 4, the material 400 comprises multiple sets 402, 404 of segments formed from the same continuous filament 401. Within each set 402, 404, the segments are at least substantially parallel to each other. The parallel segments of one set 402 cross the parallel segments of the other set 404, in this embodiment at an angle of around 90 ° .

In the embodiment shown in Figure 4, each set 402, 404 comprises multiple subsets of grouped segments, with a space between the groups. In the embodiment being described, each subset comprises three segments. The skilled person will appreciate that there may be more or fewer segments per subset, or no subsets, in other embodiments. In the embodiment shown in Figure 4, a subsequent set with the same orientation also comprises multiple subsets of grouped segments, with a space between the groups, but the subsets are offset such that the subsets of the later set overlie the space of the earlier set. Between the sets 402, 404, the filament 401 passes between one segment and the next, in this embodiment taking the form of an approximately semi-circular loop 408 or U-shape.

At the end of one set 402, the filament 401 passes between the last segment in one set and the first segment of the following set, in this embodiment taking the form of an arc of a circle of approximately 270 ° 408a.

In the embodiment shown in Figures 2 A, 2B and 3, an algorithmic script was created to allow a simple parametric weave to be generated without the need for manual input of commands. A tighter, more consistent weave 200 than that shown in Figure 4 400 can be obtained without manual input.

Two sets 202, 204 of segments which cross each other, and in particular which are perpendicular to each other, are present.

In the embodiment shown in Figures 2 A, 2B and 3, there is only one segment per subset (this may alternatively be seen as there not being subsets in this embodiment).

In the embodiment being described, the segments of the first set 202 are sufficiently closely spaced that there is no gap between segments; they touch and the polymer matrix forms a join along their lengths.

In the embodiment being described, the segments of the second set 204 are less closely spaced such that there is a small gap 206 between segments; this may be desirable, for example in embodiments in which porosity is desired. Small gaps 206 between fibres 201 are the result of rows, in this case parallel rows, having a spacing between them, leaving a gap which may run for the full length of the sample 200.

The woven structure 200 is again formed from a continuous fibre 201. The fibre curves 208 between segments, so as to get from the end of one to the start of the next on a continuous path.

Figure 3 illustrates the path 300 generated and used to control movement of the nozzle 310 so as to generate the material 200 shown in Figures 2A and 2B.

In the embodiment being described, the code produced by the algorithm is arranged to output a generic Gcode command. This code type is currently a universal language for Computer Numerical Control (CNC) systems. The Gcode toolpaths can be utilised with any CNC based system (such as previously mentioned Stitch and Tape laying systems). This would enable these systems to produce a woven structured sheet with smart pathing around weave exclusions (i.e. holes and cavities), as is described in more detail below. The skilled person would appreciate that any suitable programming language or style may be used in other embodiments.

In various embodiments of the invention, a 3D printing system for multi-layered woven composite builds upon this baseline logic, depositing multiple woven layers atop each other to form 3D parts. In the embodiments being described, the nozzle 310 is moved along a single, continuous path (the toolpath or fibre path). The woven structure can therefore be formed from a continuous filament 201, 401. The skilled person will appreciate that the path is therefore distinct from paths used in prior art weaving techniques as 3D printing cannot easily allow weaving around/behind already-laid segments, and use of a single nozzle 310 (as opposed to separate warp and weft nozzles) is sufficient.

Toolpaths of the embodiments being described generate a tabbed area around the desired geometry of waste material (Selvedge). This is a common occurrence in the textile industry. In the embodiments being described, this section is removed after weaving. In the Composites Industry, selvedge is present in both loom-fabricated and tailor-pathed composite preforms, as demonstrated in Figure 1. The structure is known as a 'Net Shape Preform' prior to the selvedge removal.

As used herein, "overrun" is used to describe the waste material or selvedge found around the edges of the woven composite.

Edge portions (selvedge) such as the loops 408 and 408a shown in Figure 4 may be trimmed off after manufacture, or indeed during manufacture. These regions extending beyond the body of the weave may be described as over-run. The skilled person will therefore appreciate that the fibre 201 , 401 may no longer be continuous in the finished product. However, the weave pattern resulting from the continuous fibre path remains.

In some embodiments, the selvedge may not be removed, and indeed may be used as part of the load-bearing, to produce a waste less product. The skilled person will appreciate that the toolpath generation may be modified so as to change the shape of the selvedge to increase its utility.

The purpose of selvedge 408, 408a is to allow the filament 401 to get from the end of one segment to the beginning of the next without breaking the fibre path. The skilled person will appreciate that for a stiffer, less flexible, fibre a larger selvedge area is likely to be needed to allow for a more gradual curve. The use of selvedge may decrease the risk of fibre damage during deposition, as compared to cutting the filament on each pass.

In one embodiment, a script was written to allow for the production of rectangular laminates of any size. Parameters that can be altered include: Weave spacing, Sheet size, overrun length, number of overlaps per length.

In the embodiment being described, this script was run using Excel, however the skilled person will appreciate that this may be transferred to a mathematical programming system such as MATLAB or any other suitable program, which may facilitate more complex structure creation.

Figure 5 illustrates the manufacture of a woven composite 500, with a machine head 510 moving a nozzle so as to print the continuous filament 501. Loops 508 between sets of segments of the continuous filament 501 can again be seen (selvedge).

As Figure 5 shows the incomplete woven composite 500, there are gaps 509 between the sets of segments which are due to be filled with further segments.

Figure 6 shows the finished woven composite 500. Both ends 501 a, 501b of the filament 501 can be seen.

In the embodiments shown in Figures 2 to 6, the woven composite follows a regular, repeated, weave pattern. For example, the woven composite 500 can be seen to have a repeating pattern of squares formed by the weave path - 25 squares are arranged in a 5 by 5 grid, each square having what appears as a lighter triangle and a darker triangle due to the different angle of the uppermost segments of that square and lighting angle for the photograph. In alternative embodiments, the weave pattern may not be repeated and/or may not be regular.

The path design methodology allows for the inclusion of apertures, for example circular hole features 710, passing through the plane of the woven composite/of the weave path. The skilled person will appreciate that such apertures 710 may facilitate the integration of embedded components during multi-laminate printing.

The apertures 710 may be formed by deviating from the regular, repeated, weave pattern in the desired aperture location. The path of the continuous filament 701 deviates from the regular pattern where it would otherwise cross the desired aperture location to instead go around the desired aperture location, forming an edge of the aperture 710. The skilled person will appreciate that the diversion of segments around the aperture location may increase a fibre density around the edge of the aperture 710 as compared to that in an undisrupted portion of the weave, so reinforcing an edge of the aperture. Holes of various sizes were printed to determine the viability of feature sizes. Using the selected filament type and the chosen pathing method, holes of 2mm diameter and smaller were mostly unprintable, and holes greater than 15mm in diameter led to fibre snagging and lessened the weave ' s integrity.

Current industrial fasteners (aerospace and automotive) are typically in the range of 5- 12 mm in diameter, making the embodiments described herein applicable as a direct replacement for loom woven composite sheeting, as the hole size tolerances are suitable.

The skilled person will appreciate that the possible hole sizes and tolerances may vary for different fibres, nozzles and/or pathing methods.

The skilled person will appreciate that hole size can be changed in sequential layers during 3D printing, for example so as to form a tunnel though, or a blind cavity within, a 3D woven structure.

The skilled person will appreciate that the tailorable size and shape of the weave structures generated means that the embodiments described could also be applied for reinforcement patches, for example to be integrated into existing vacuum bagging processes. Repair patches can be printed to size and fitted with adhesive or fasteners to a damaged composite surface as a form of repair patch. The skilled person would appreciate that cost and production time may be lower using embodiments of the present invention, as compared with vacuum applied pre -prepared patches.

Figure 7A illustrates a weave path 750 similar to that used for the woven composite 500 of Figures 5 and 6, but with an incorporated aperture 702. Overrun/selvedge regions 754 can be seen along the edges of the woven structure. The aperture 702 passes through a plane of the weave path 750.

Figure 7B shows the woven composite 700 formed by printing using the weave path 750 shown in Figure 7A. The aperture 710 can be seen in the middle of the woven composite 700.

An aperture 710 is defined in this context as a purposeful deviation of fibres 701 to produce a localised opening in the weave 700. In the embodiment shown, the segments are otherwise parallel in the body of the structure, and the deviation is away from parallel in order to create the aperture 710.

In the embodiment being described, fibre density is increased around the edge of the aperture 710. The fibre density around the edge of the aperture is dependent on the size of the aperture; increasing size leads to increasing density using the pathing algorithm shown (i.e. the area around the aperture has several paths of fibre stacked therefore making it thicker and more dense). The skilled person will appreciate that other pathing algorithms may divert the fibre segments further or differently in order to keep fibre density more even across the woven structure 700. However, the skilled person will also appreciate that the increased fibre density provided by the embodiment being described may beneficially reinforce the aperture 710.

Figure 8 shows a substantially square woven structure 800 similar to that shown in Figure 7B but with a smaller aperture 810 relative to the fibre 801 and weave 800 size.

Figure 9A shows a substantially rectangular woven structure 900a comprising a printed aperture 910.

Figure 9B shows a substantially rectangular woven structure 900b, made using the same pathing approach as for that 900a shown in Figure 9A, but without a printed aperture 910. In Figure 9B, the woven structure 900b is not quite complete - a machine head 910 is pictured moving a nozzle so as to print the continuous filament.

Figure 10A shows the woven structure 900a with an aperture, as shown in Figure 9A, alongside the woven structure 900b without an aperture, as shown in Figure 9B. In addition, a third woven structure 900c is shown - this woven structure 900c is identical to that 900b shown in Figure 9B, but an aperture of the same size and in the same position as that printed in the middle woven structure 900a has been drilled through the weave.

Mechanical testing was performed on an assortment of woven samples, including those 900a-c shown in Figure 10A. Samples were prepared without holes 900b, with holes drilled from the weave's centre 900c (as by industry machining standard), and with a hole printed directly into the weave 900a with no post-processing needed.

The results, shown in Figure 10B which plots tensile strength in arbitrary units, indicate a large decrease in strength for drilled/machined samples 900c (as is experienced often in industry). Woven samples with a printed hole 900c achieved a strength 95% that of samples without a hole 900b.

Figures 1 1A, 1 1B and 1 1C illustrate two further woven composite 1 100, 1 100c, demonstrating that the selvedge 1 154 may be relatively narrow as compared to the size of the structure. The woven panel 1 100 has a finer meshed weave (increased number of Y axis passes) as compared to those shown in preceding figures, with an integrated 6mm fastener hole. Reduction of waste, evidenced by the relatively narrow selvedge region 1 154, was achieved by altering the overrun distance and the number of passes in this embodiment. Figure 1 1B illustrates a fastener 1 120 secured through the printed aperture 1 1 10 in one woven composite 1 100.

Figure 1 1C illustrates a fastener 1 120c secured through the printed aperture in the other woven composite 1 100c.

The woven composites 1 100, 1 100c are examples of multi-laminate prints, unlike various earlier embodiments which show only one or two layers. Toolpath Parameters

The program used to generate the weave structures discussed above has been developed with multiple input parameters to allow for a large number of potential woven structures. The code used is capable of producing a rectangular specimen with a single included feature (i.e. a hole) located anywhere in the structure. The skilled person will appreciate that the same principle may be used for more complex geometries.

Parameters that can be altered include: Weave spacing, Sheet size, overrun length, number of overlaps per length.

Weave spacing parameters allow for the use of many sizes of fibre filament, in that a step-over between adjacent segments can be increased to accommodate a wider filament, and vice versa. In addition, this parameter can be used to create porous composites (e.g. with matrix grid-like structures), by increasing the step-over between segments to more than that required to accommodate the fibre width.

The skilled person will appreciate that the generation of porous composites is not possible using prior art infusion-based process, and that porous composites may have potential applications in the future development of repair patches, internally structured laminates, or reinforcement laminates for integration into vacuum consolidation systems (as a joint or hole reinforcement layer).

Figure 12 illustrates a toolpath 1200 in more detail, showing different stages. The toolpath 1200 is suitable for generating a woven composite 900a as shown in Figure 9A. In stage 1202, the nozzle 310 is laying down the first segment of the third traversal of the composite structure. The intended presence of an aperture is demonstrated by the small deviation 1203 of one segment.

In stage 1204, the nozzle 310 is laying down the first segment of the fifth traversal of the composite structure. The intended presence of an aperture is demonstrated by the small deviation 1203 of five segments - the circular shape of the aperture is starting to emerge. There are large gaps between the sub-sets of segments in each set.

In stage 1206, the deviations and circular shape are becoming more apparent.

In stage 1208, the full extent of the aperture 1203 is shown.

In stage 1210, the gaps between the sub-sets of segments are smaller than the aperture 1203. In stage 1212, the gaps between the sub-sets of segments have been filled in by further segments, leaving the aperture 1203 as the only hole through the composite structure (discounting selvedge).

Figure 13 illustrates a method 1300 of an embodiment of the invention. At step 1302, a continuous filament is obtained. In the embodiment being described, the continuous filament is a fibre impregnated or coated with a binder.

In the embodiment being described, the binder is chosen to melt when heated and set when cooled, and for example may be a thermoplastic polymeric binder.

At step 1304, the filament is heated so as to melt the binder. This step may be performed within a heated nozzle of a 3D printing apparatus, elsewhere in a 3D printing apparatus, or before the filament is introduced to the 3D printing apparatus. At step 1306, the 3 D printing apparatus is used to lay the filament. The 3D printing apparatus lays 1306 the continuous filament along a path chosen so as to form a woven structure; i.e. such that two sets of segments are formed from the same continuous filament, segments of the first set crossing segments of the second set in an under-over pattern. The skilled person will appreciate that the under-over pattern may not be a simple under one-over one-under one repeat across adj acent segments, but rather that a segment may go under x segments of the other set then over y segments of the other set, and may then return to going under x segments of the other set or may instead go under a different number, z, of segments of the other set. The values of x, y, and optionally z, may vary between segments of a set, and may vary between sets. In the embodiment being described, the woven composite material is gradually built up from a forming surface on which it is printed. The first strand(s) of the first set to be laid are therefore under all strands of the second set that cross them (which may be all strands of the second set, depending on composite shape). In embodiments in which segments of the second set are arranged to cross segments of the first set in a repeating pattern, the repeating pattern may be said to have a unit cell (the smallest repeating unit that makes up the pattern, optionally without rotation of the unit cell). A unit cell of the repeating pattern comprises N segments of the first set and M segments of the second set; N and M optionally being equal. For a complete unit cell made according to the method 1300 being described, if a segment nj of the first set passes above / crosses over segment m of the second set and segment n 2 of the first set passes above more segments of the second set than segment n segment n 2 also passes above segment m, where n and n 2 represent any two segments of the first set in that unit cell and m represents any segment of the second set in that unit cell (i.e. for all n n 2 E N and all m E M). The skilled person will appreciate that, where a unit cell is incomplete (e.g. due to the presence of an aperture, to the end of the composite sheet, and/or to the composite sheet having been cut), this may no longer hold, e.g. due to segment m and/or n 2 having been cut or diverted such that they do not cross. In the embodiment being described, a single extruded filament is used to form the woven structure.

At step 1308, the binder is allowed to cool. As the binder sets when cooled in the embodiment being described, cooling sets the woven structure. In alternative or additional embodiments, cooling may not be used to set the binder - for example, a binder which is electro-setting may be used, or a binder which sets when exposed to heat or to a chemical.

Figure 14 illustrates a method 1400 of an embodiment of the invention. At step 1402, a first set of conjoined parallel (or approximately parallel) segments of a filament are printed using a 3 D printing apparatus.

At step 1404, a second set of conjoined parallel (or approximately parallel) segments of a filament are printed using the 3D printing apparatus. The parallel segments of the second set cross the parallel segments of the preceding set. At step 1406, the process is then repeated as desired to form the intended structure.

Figures 15A-C illustrate embodiments with embedded sensors, tags and fasteners.

The skilled person will appreciate that many applications of materials require sensing, communication or data capabilities. For example, with the expansion of the "internet of things", it is likely that more and more everyday objects will have incorporated electronics, be they sensors or chips or tags, such as FID tags or the likes. The incorporated electronics may be passive (e.g. a readable RFID tag) or active (e.g. a sensor arranged to record data). FID tags (and equivalents) are often provided as small disks or strips. The inclusion of a cavity within a woven 3D composite allows such a tag, or indeed a different sensor or object, to be embedded within a composite material without changing the surface appearance - the segments can be diverted away from and around the cavity instead of causing a bulge in the surface as would happen if a tag was simply inserted between two layers of a prior art composite material.

The tag may therefore be placed into the cavity during the printing process, and subsequent layers may pass over the tag, thereby sealing it inside. Figures 15A to C show a woven composite 1500 with various incorporated elements.

In the embodiment shown in Figure 15 A, an RFID tag 1502 is fully embedded within a cavity in a composite material. As the segments are diverted, the surfaces of the material 1500 do not show a bulge in the area of the RFID tag 1502, so providing an even surface. A cross-sectional side view 1520a is shown on the left; the layers of the composite material 1500 can be seen. A top view 1520b is shown on the right; the tag 1502 is shown in a lighter colour to indicate its position and that the tag would not be visible from the surface of the composite material.

In alternative or additional embodiments, sensors may be fully or partially embedded within a woven composite material by the formation of suitably sized and shaped apertures or cavities.

For example, a light sensor may be embedded in a cavity in a woven 3D material with a first aperture on one side of the material and a second aperture on another (or the same) side of the material.

Figure 15B shows one such example for a wired component 1504. As can be seen from the cross- sectional view 1530a and the top view 1530b, the component 1504 is embedded within a cavity in the material 1500. The wires 1506 extend through an aperture from the cavity. The wires 1506 and a small portion of the component 1504 are therefore visible (shown in a darker colour) in the top view 1530b.

In an alternative embodiment, a light sensor is embedded within a printed composite material. The light sensor is accommodated within a cavity in the material. The cavity is sized and shaped to hold the sensor in place, such that it cannot be dislodged.

A first aperture is provided on a first side of the material. The first aperture is arranged to allow light to reach the sensor.

A second aperture is provided on a second side of the material. The second aperture is arranged to allow a power and/or data cable to reach the sensor. In additional or alternative embodiments, one or more force sensors or accelerometers may be embedded within a material. Advantageously, the outputs of these sensors may be used to track stresses and strains on the material in use.

Figure 15C shows an embodiment with a fastener 1508, 1510. The fastener comprises a bolt 1508 and a nut 1510. As can be seen from the cross-sectional view 1540a and the top view 1540b, the bolt 1508 extends through an aperture through the material 1500. The nut 1510 can then be connected to the bolt 1508 at the far side of the material 1500 from the head 1508a of the bolt 1508

Figure 16A shows a plan view of a woven composite 1600, and two cross-sectional views (A, B) at different points. The weave 1600 comprises a repeating pattern; four unit cells of the repeating pattern are shown in Figure 16 (a unit cell being the smallest repeating part of the repeating pattern). In the embodiment being described, the parallel segments of the first set (shown in black in the plan view) are perpendicular to the second set of parallel segments (shown in white in the plan view)

In the embodiment being described, each unit cell of the repeating pattern is square. In other embodiments it may be rectangular or may take a different shape.

In the embodiment being described, each unit cell of the repeating pattern is formed by eight segments of the first set and eight segments of the second set. In other embodiments, the numbers of segments from the first and/or second set may differ, and/or may be more than or less than eight. In the embodiment being described, the first segment 1601 of the first set (counting from the top of the unit cell in the orientation pictured in Figure 16 A) passes over seven segments in the second set, then under the next segment in the second set (completing a first unit cell), then over seven segments in the second set, then under the next segment in the second set. The skilled person would appreciate that this repeating pattern may continue to the end of the composite structure 1600.

In the embodiment being described, the fourth segment 1604 of the first set (counting down from the top in the orientation shown in Figure 16 A) passes over four segments in the second set, then under the next four segments in the second set (completing a first unit cell), then over four segments in the second set, then under the next four segments in the second set. This is shown in cross-sectional view A. The skilled person would appreciate that this repeating pattern may continue to the end of the composite structure.

In the embodiment being described, the tenth segment 1602 of the first set (the second segment of the second row of two unit cells for the weave 1600 shown) passes over six segments in the second set, then under the next two segments in the second set (completing a first unit cell), then over six segments in the second set, then under the next two segments in the second set. This is shown in cross-sectional view B. The skilled person would appreciate that this repeating pattern may continue to the end of the composite structure. The skilled person will appreciate that, for a number of segments N of one set of segments in a unit cell, the «th segment may therefore go over (N-n) segments and under n segments in each unit cell. N=8 for the embodiment shown in Figure 16, for each set of segments.

The skilled person will appreciate that the repeating pattern for the second set of segments (shown in white in Figure 16) is substantially the same as that for the second set of segments (shown in black in Figure 16) but reflected across the diagonal of the unit cell (as the sets are perpendicular and the unit cell is square). In embodiments in which the sets are not perpendicular, the effective reflection or rotation angle may vary accordingly. As illustrated by cross-sections A and B, cross-sections of the composite 1600 formed show different under-over patterns at different positions. The structure 1600 is defined as woven by the filament being in two planes at once, despite being deposited from above from a single nozzle 3 10. How this is achieved is discussed below with respect to Figure 18. The skilled person will appreciate that, as shown in the cross-sectional views of Figure 16A, portions of each segment can be in a first plane or a second plane adj acent the first plane (with small transition regions at the changes of plane). The composite 1600 has a bi-planar structure. A segment portion in the first plane necessarily lies below any segment crossing it (in the orientation shown). A segment portion in the second plane necessarily lies above any segment crossing it (in the orientation shown). Once a segment has been printed, it does not change plane. Segments are printed onto a forming surface, the forming surface defining the first plane. Therefore, when a segment is printed, it lies in the first plane in any regions of its path in which the forming surface is bare, and in the second plane in any regions of its path in which another segment is already present on the forming surface.

In the embodiment shown in Figure 16A and 16B, the first set (in black) has one segment 1608 per unit cell that passes beneath all segments of the second set. Correspondingly, the second set (in white) has one segment 1618 which passes above all segments of the first set (referred to as a "flyer" or "flyer segment"). The skilled person will appreciate that this could be reversed in other embodiments.

In the embodiment being described, adj acent segments of a sub-set are sufficiently closely spaced that a segment crossing a pair of adj acent segments cannot bend or sag therebetween to reach the forming surface (the first plane). By contrast, if a segment lies at the edge of a subset, there is a gap instead of an adj acent segment and the crossing segment may bend to the first plane. The or each flyer segment is therefore only present in one plane in various embodiments, as it lies either under all segments of the other set (flat on the forming surface - the first plane), or over all segments of the other set (flat in the second plane). The flyer segments may be counted as separate from the subsets as all other segments in the subsets have portions in both the first plane and the second plane.

In embodiments in which there is a gap between sub-sets, the upper flyer segment may be present in two planes; sagging or bending into the first plane between sub-sets. However, it is still classed as a flyer segment as no segment crosses above it - it lies over all other segments.

The skilled person will appreciate that the printed weave pattern differs from standard weave patterns. For example, one row 1608, 1618 from each set in each cell is unwoven (known as flyers), i.e: the first and last layers to be laid sit below all filaments it crosses or on top of all filaments it crosses, respectively. The top-most segment of each unit cell (the last to be laid) therefore does not pass under any other segments and the bottom-most segment of each unit cell (the first to be laid) therefore does not pass over any other segments.

Figure 16B illustrates the same weave pattern 1600 as shown in Figure 16A, with the segments numbered in the order of their deposition.

The first and second segments to be laid 1608a, 1608b are deposited directly onto a surface on which the composite 1600 is to be formed. The first and second segments 1608a, 1608b lie in a single plane - the first plane. The first and second segments to be laid 1608a, 1608b form the lowermost segments of each unit cell in the orientation shown, for the weave pattern shown.

The first and second segments to be laid 1608a, 1608b are parallel and are therefore both part of the same general set of segments - the first set (shown in black in Figures 16A-C).

The first and second segments to be laid 1608a, 1608b are spaced apart in the embodiment shown, allowing space for the rest of a unit cell to be printed between them.

The third and fourth segments to be laid 161 1 a, 161 1b are deposited perpendicularly to the first and second segments. The skilled person will appreciate that the segments 1608a, 1608b, 161 1 a, 161 1b are all conjoined, forming part of a single filament, but that the joins are not shown in Figures 16A- C for clarity - Figures 8 and 12 show corresponding examples including the joining portions.

The third and fourth segments to be laid 161 1 a, 161 1b are deposited onto the same surface on which the composite 1600 is to be formed, but the already-printed first and second segments 1608a, 1608b cover an area of the surface, so causing the third and fourth segments 161 1 a, 161 1b to bend to go over the first and second segments 1608a, 1608b. The third and fourth segments therefore lie in two planes - the first plane where the segments lie on the surface, and a second plane where they cross the other segments. The first and second segments to be laid 1608a, 1608b form the left-most segments of each unit cell in the orientation shown, for the weave pattern shown. The third and fourth segments to be laid 161 1 a, 161 1b are parallel and are therefore both part of the same general set of segments - the second set (shown in white in Figures 16A-C).

The third and fourth segments to be laid 161 1 a, 161 1b are spaced apart in the embodiment shown, allowing space for the rest of a unit cell to be printed between them.

The stage of printing 1600a following the laying of the first four segments is shown in Figure 16C.

Fifth and sixth segments 1607a, 1607b are then printed adjacent and parallel to the first and second segments 1608a-b, forming part of the first set of segments.

The fifth and sixth segments to be laid 1607a, 1607b are deposited onto the same surface on which the composite 1600 is to be formed, but the already-printed third and fourth segments 161 1 a, 161 1b cover an area of the surface, so causing the fifth and sixth segments 1607a, 1607b to bend to go over the third and fourth segments 161 1 a, 161 1b. The fifth and sixth segments therefore lie in two planes - the first plane where the segments lie on the surface, and the second plane where they cross the other segments.

Seventh and eighth segments 1612a, 1612b are then printed adjacent and parallel to the third and fourth segments 161 1 a-b, forming part of the second set of segments.

The seventh and eighth segments to be laid 1612a, 1612b are deposited onto the same surface on which the composite 1600 is to be formed, but the already-printed first, second, fifth and sixth segments cover an area of the surface, so causing the seventh and eighth segments 1612a, 1612b to bend to go over the already-present segments. The seventh and eighth segments therefore lie in two planes - the first plane where the segments lie on the surface, and the second plane where they cross the other segments.

The seventh and eighth segments each cross an adjacent pair of perpendicular segments per unit cell. The pairs of adjacent segments (1608a - 1607a and 1608b - 1607b) can be thought of as sub-sets of the first set of segments - segments within a sub-set are closer together than the spacing between subsets.

The stage of printing 1600b following the laying of the first eight segments is shown in Figure 16C. Ninth and tenth segments 1606a-b are then added adjacent and parallel to the fifth and sixth segments 1607a-b. The ninth and tenth segments each cross an adjacent pair of perpendicular segments per unit cell. The pairs of adjacent segments (161 1 a-1612a and 161 1b - 1612b) can be thought of as sub-sets of the second set of segments - segments within a sub-set are closer together than the spacing between subsets.

Eleventh and twelfth segments 1613a-b are then added adjacent and parallel to the eighth and ninth segments 1612a-b. The eleventh and twelfth segments each cross an adjacent group of three perpendicular segments per unit cell. The group of adjacent segments (1608a- 1606a and 1608b - 1606b) can be thought of as sub-sets of the first set of segments - segments within a sub-set are closer together than the spacing between subsets.

The stage of printing 1600c following the laying of the first twelve segments is shown in Figure 16C.

Thirteenth and fourteenth segments 1605a-b are then added adjacent and parallel to the ninth and tenth segments 1606a-b. The thirteenth and fourteenth segments each cross an adjacent group of three perpendicular segments per unit cell. The groups of adjacent segments (161 1 a- 1613a and 1611b - 1613b) can be thought of as sub-sets of the second set of segments - segments within a sub- set are closer together than the spacing between subsets.

Fifteenth and sixteenth segments 1614a-b are then added adjacent and parallel to the eleventh and twelfth segments 1613a-b. The fifteenth and sixteenth segments each cross a group of four adjacent perpendicular segments per unit cell. The group of adjacent segments (1608a- 1605a and 1608b - 1605b) can be thought of as sub-sets of the first set of segments - segments within a sub-set are closer together than the spacing between subsets.

The stage of printing 1600c following the laying of the first sixteen segments is shown in Figure 16C.

In the embodiment being described, this pattern is repeated until all 32 segments of the weave 1600 have been laid.

The skilled person will appreciate that, as segments are added, the spaces between the subsets of segments decrease in size. In the embodiment being described, laying the final segment 1618 in each unit cell fills the gap between adjacent subsets, so resulting in an even segment spacing throughout the weave, as shown in Figure 16B. In alternative embodiments, such as that shown in Figures 2A and 2B, the subsets may remain separate on completion - for example by selecting a spacing between the first segment of one unit cell and the first segment of an adjacent unit cell to be greater than the width of the number of segments to be in that unit cell. In the embodiment being described, only two segments cross at any one point on the surface, so keeping the weave to a thickness of two layers - the first and second planes. In the embodiment being described, the resultant woven composite 1600 has a thickness of twice the filament thickness.

In the embodiment being described, each unit cell is laid by alternating a segment of the first set and a segment of the second set. In alternative embodiments, two or more segments of one set may be laid between printing segments of the other set. For example, in the embodiment shown in Figure 16D the two adjacent segments in the middle of each unit cell, which both form part of the first set, are printed consecutively, after segment 1649 of the second set is printed and before the next second set segment - segment 1651 - is printed.

In the embodiment being described, consecutive segments of one set to be printed in each unit cell are printed adjacent the most recently printed segment in the same set in that unit cell. In alternative embodiments, the next segment of a set to be printed may be spaced from the most recently previously printed segment of that set, with the gap being filled by one or more later- printed segments.

Figure 16E illustrates a further example - as for Figure 16D, the numbering is used to illustrate a printing order of the segments (1 -22). The weave of Figure 16E comprises two rectangular unit cells. In the weave of Figure 16E, the next segment of a set to be printed is spaced from the most recently printed segment of that set for that unit cell, resulting in a weave pattern different from the consecutive steps of the weaves of Figures 16A and D. In the embodiment being described, all segments of one set cross all segments of the other set. A current segment to be printed crosses over all segments of the other set already printed and under all segments of the other set not yet printed in the embodiments being described. In alternative embodiments, not all segments of one set may cross all segments of the other set, e.g. due to the shape of the composite material - in such embodiments, a current segment to be printed crosses over all segments of the other set already printed which fall along its path, and under all segments of the other set not yet printed which fall along its path, but segments of the other set outside its path are not crossed by it.

The skilled person will appreciate that Figure 16 A-E illustrates just a few examples of a possible weave pattern; the number of segments in each unit cell can be changed, and the number of segments in each set can be changed differently. Further, the number of 'unders' and 'overs' for a segment can be altered by changing the stacking sequence, and/or a much less regular, or even entirely non-repeating, pattern may be used in some embodiments. Figure 17 shows an image of a similar weave to that of Figure 16A with a different unit cell size; N=4 for the embodiment shown in Figure 17, for each set of segments.

Figure 18 illustrates deposition of a single segment 1802 by a nozzle 310 at two different times, tj and t 2 , with t 2 following tj . The single segment 1802 is being deposited onto a flat surface on which two sub-sets of perpendicular segments 1804, 1806 have already been deposited. The two sub-sets of perpendicular segments 1804, 1806 were deposited onto the flat surface. In the embodiment shown, the two sub-sets of perpendicular segments 1804, 1806 lie entirely in one plane. In the embodiment shown, the segment 1802 being deposited is deposited in two separate planes - a first plane directly on the flat surface and a second plane on top of the two sub-sets of perpendicular segments 1804, 1806. The previously-printed segments 1804, 1806 provide a surface of varying height for the deposition of the current segment 1802. The spaces, or troughs, between the sub-sets 1804, 1806 of pre -printed segments allow the next overlaying filament segments to be deposited 'from the top' whilst being deposited in two different planes.

Arrows A illustrate a direction of movement of the nozzle 310, and also, in the embodiment being described, a print level as coded in a control system for the print nozzle 310 (which may also be referred to as a print head). In the embodiment being described, the nozzle 310 is capable of very small amount of movement in the Z-axis (perpendicular to the weave surface), as indicated by Arrow B in Figure 18. In the embodiment being described, the nozzle 310 is biased towards the surface on which the composite 1802, 1804, 1806 is being deposited (downwards, in the orientation shown). The skilled person will appreciate that this allows for the nozzle 310 to be deflected upward by any previously deposited segments 1804, 1806, and then return to the original Z-height upon passing these previously deposited segments 1804, 1806 (in the "troughs" between sub-sets).

In the embodiment being described, biasing of the nozzle 310 is provided by mounting the nozzle 3 10 on a cantilevered plate, so allowing the desired deflection to occur. The skilled person would appreciate that the movement along the Z-axis could be achieved using a spring, via a spring- loading mechanism (which may provide greater control of downward forces than a non- adjustable cantilever plate or spring), and/or using a sensor and actuator or the likes in place of a biasing means such as a spring. In the embodiment being described, the nozzle 310 is arranged to apply a constant pressure to the underlying material on to which the current segment 1802 is being deposited. The nozzle 310 is arranged to be able to flex vertically by a small amount, so allowing it to deflect upward (in the orientation shown) when the nozzle meets pre-printed segments. The skilled person will appreciate that laying segments of one set in spaced subsets 1804, 1806 may facilitate laying the segments 1802 of the other set in multiple planes (the spacing between sub-sets being greater than a segment width and greater than a spacing between segments in a sub-set), as the space or trough between subsets provides space for the current segment 1802 to bend from the higher plane to the lower plane and return to the higher plane.

In the embodiments being described, a woven (under-over) structure is therefore provided simply by 3D printing a continuous filament - no parts of the filament need to be moved between depositing and curing to permit the structure to be made, and no guide wires, poles, or other loom-type apparatus is needed.

Figure 19 is an image of a cross-section of a sample comprising ten woven layers stacked atop each other to produce a thicker component. In the embodiment shown in Figure 19, the same procedure as described above is followed, and subsequent layers are placed directly on top of each other by increasing the Z position/height by the required layer height, and the layers are bound together by the matrix material.

It can be seen that the segments running across the sample are not straight, but rather weave up and down as they pass under and over other segments.

The skilled person will appreciate that, just as the method as described above can be used to create an aperture through the plane of a single woven layer, the method can be used to create an aperture and/or a completely or partially enclosed void region (a cavity) through a layered sample, for example for embedding of components within/through the structures. In the embodiment shown in Figure 19, an enclosed void could be created by creating aligned apertures of different sizes in consecutive woven layers of the stack, and including woven layers without an aperture therethrough on either side of the layers with apertures.

The skilled person will appreciate that the embodiments described are provided by way of example only, are not limiting and represent a small fraction of the options that would be apparent to the skilled person on reading this disclosure.