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Title:
FIBRE ROPES AND COMPOSITE MATERIALS CONTAINING FIBRE ROPES
Document Type and Number:
WIPO Patent Application WO/2018/130857
Kind Code:
A1
Abstract:
A fibre rope (4) comprising a plurality of fibre strands (3), each strand formed by twisting a tow (2), the tow comprising a plurality of fibres (1) of a non-polymeric, non-metallic and high modulus material, e.g. carbon or glass, with the tow (2) being twisted with a first twist density to form each of the fibre strands, and the plurality of the fibre strands (3) being twisted with a second twist density to form the fibre rope (4), wherein each fibre strand (3) has a helical angle with respect to the elongate axis (A) of the fibre rope of at least about 15°. Moreover, composite materials comprising the fibre rope (4) are also described, as are methods of producing the rope (4) and composite material.

Inventors:
MEO, Michele (Chargrove HouseShurdington Road, Cheltenham GL51 4GA, GL51 4GA, GB)
PINTO, Fulvio (Chargrove HouseShurdington Road, Cheltenham GL51 4GA, GL51 4GA, GB)
IERVOLINO, Onorio (Chargrove HouseShurdington Road, Cheltenham GL51 4GA, GL51 4GA, GB)
Application Number:
GB2018/050112
Publication Date:
July 19, 2018
Filing Date:
January 16, 2018
Export Citation:
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Assignee:
THE UNIVERSITY OF BATH (Claverton Down, Bath BA2 7AY, BA2 7AY, GB)
International Classes:
B29C70/16; D07B1/02; D07B3/00
Foreign References:
EP0961050A21999-12-01
JP2008231642A2008-10-02
US3446003A1969-05-27
EP0303381A11989-02-15
US3648452A1972-03-14
US7814740B22010-10-19
Attorney, Agent or Firm:
HASELTINE LAKE LLP (Redcliff Quay, 120 Redcliff Street, Bristol BS1 6HU, BS1 6HU, GB)
Download PDF:
Claims:
CLAIMS

1. A composite material comprising a fibre rope and a matrix material, the rope comprising a a plurality of fibre strands, each strand formed by twisting a tow, the tow comprising a plurality of fibres of a non-polymeric, non-metallic and high modulus material, with the tow being twisted with a first twist density to form each of the fibre strands, and the plurality of the fibre strands being twisted together with a second twist density to form the fibre rope, wherein each fibre strand has a helical angle with respect to the elongate axis of the fibre rope of at least about 15°. 2. A composite material according to claim 1 , the composite material comprising a fabric formed from a plurality of the ropes and the matrix material.

3. A composite material according to claim 2, the composite material comprising a single layer of the fabric or a plurality of layers of the fabric.

4. A composite material according to claim 2 or claim 3, wherein the first twist density is at least 25 turns per metre.

5. A composite material according to claim 1 , wherein the composite material is in the form of a rod comprising a single rope and the matrix material.

6. A composite material according to any one of the preceding claims, wherein each fibre strand comprises the fibre tow twisted in a first helical direction, the plurality of strands being twisted together in a second helical direction, wherein the second helical direction is opposite to the first helical direction.

7. A composite material according to any one of the preceding claims, wherein the first twist density is in the range of about 25 turns per metre to about 200 turns per metre, optionally about 50 to about 160 turns per metre.

8. A composite material according to any one of the preceding claims, wherein the second twist density is at least about 25 turns per metre.

9. A composite material according to claim 8, wherein the second twist density is in the range of about 25 turns per metre to about 200 turns per metre, optionally about 50 to about

160 turns per metre.

10. A composite material according to any of the preceding claims, wherein the ratio of the first twist density to the second twist density is in the range of about 1 :2 to about 2: 1. 1 1. A composite material according to any of the preceding claims, wherein the fibre strand has a helical angle with respect to the elongate axis of the fibre rope of at least about 20°, optionally at least about 30°.

12. A composite material according to any of the preceding claims, wherein the fibres of a non-polymeric, non-metallic and high modulus material are carbon fibres.

13. A composite material according to any of the preceding claims further comprising a polymer strand, wherein the polymer strand comprises a polymeric material. 14. A composite material according to claim 13, wherein the polymeric material is selected from polyolefins, aramids and polyamides.

15. A composite material according to claim 13 or claim 14, wherein the polymer strand is twisted with the fibre strands with a second twist density.

16. A composite material according to any of the preceding claims further comprising a metallic strand, wherein the metallic strand comprises a metallic material, optionally a shape- memory-alloy, steel, copper or titanium. 17. A composite material according to claim 16, wherein the metallic strand is twisted with the fibre strands with a second twist density.

18. A composite material according to any of the preceding claims further comprising a polymer tow, wherein the polymer tow comprises a polymeric material and the polymer tow is twisted with the fibre tow with the first twist density to form a fibre strand.

19. A composite material according to any of the preceding claims further comprising a metallic tow, wherein the metallic tow comprises a metallic material and the metallic tow is twisted with the fibre tow with the first twist density to form a fibre strand.

20. A composite material according to any of the preceding claims further comprising a metallic tow, wherein the metallic tow comprises a metallic material and the fibre tow is twisted around the metallic tow with a first twist density to form a fibre strand comprising a metallic tow core.

21. A composite material according to any of the preceding claims comprising at least three of the fibre strands.

22. A composite material according to any of the preceding claims wherein each fibre strand comprises at least about 500 fibres, optionally at least about 1000 fibres, or at least about 5000 fibres.

23. A composite material according to any of the preceding claims, wherein each fibre strand is twisted with a second twist density around a core material.

24. A composite material according to any of the preceding claims, wherein the matrix material comprises a resin.

25. A composite material according to any one of the preceding claims, wherein the resin is a thermosetting resin or a thermoplastic resin.

26. A method of producing a fibre rope, the method comprising:

a) providing a plurality of fibre tows, each tow comprising a plurality of fibres of a non- polymeric, non-metallic and high modulus material;

(b) twisting each fibre tow with a first twist density to provide a plurality of fibre strands; and

(c) twisting the plurality of the fibre strands together with a second twist density to provide a fibre rope, such that each fibre strand has a helical angle with respect to the elongate axis of the fibre rope of at least about 15°.

27. A method according to claim 26, wherein steps (b) and (c) are carried out simultaneously.

28. A fibre rope comprising a plurality of fibre strands, each strand formed by twisting a tow, the tow comprising a plurality of fibres of a non-polymeric, non-metallic and high modulus material, with the tow being twisted with a first twist density to form each of the fibre strands, and the plurality of the fibre strands being twisted with a second twist density to form the fibre rope, wherein each fibre strand has a helical angle with respect to the elongate axis of the fibre rope of at least about 15°.

29. A rope according to claim 28, wherein the fibres of a non-polymeric, non-metallic and high modulus material are carbon fibres.

30. A rope according to claim 28 or claim 29, wherein the first twist density is at least 10 turns per meter. 31. A rope according to claim 28 or claim 29, wherein the first twist density is at least 25 turns per meter.

32. A rope according to any one of claims 28 to 31 , wherein the ratio of the first twist density to the second twist density is in the range of about 1 :2 to about 2:1.

33. A rope according to any one of claims 28 to 32, wherein the first twist density is more than the second twist density.

34. A fibre fabric comprising a fibre rope according to any of claims 28 to 33.

35. A fibre fabric according to claim 34 comprising a woven fibre rope according to any of claims 28 to 33.

36. A method of producing a fibre fabric comprising combining a plurality of fibre ropes according to any of claims 28 to 33.

37. A method of producing a fibre fabric comprising weaving a fibre rope of any of claims 28 to 33. 38. A method of producing a composite material comprising combining a fibre rope according to any of claims 28 to 33 and a matrix material.

39. A method of producing a composite material comprising combining a fibre fabric according to any of claims 28 to 33 and a matrix material. 40. An article comprising a composite material according to any one of claims 1 to 25.

41. An article according to claim 40, wherein the article is a component of an aircraft or a vehicle.

42. An article according to claim 41 , wherein the component is a structural component.

43. An article according to claim 41 , wherein the composite material comprises a fabric formed from a plurality of the ropes and the matrix material, and the article is a panel for use as an exterior surface on an aircraft or a vehicle.

44. An article according to claim 40, wherein the composite material is in the form of a rod comprising a single rope and the matrix material, the rod optionally being curved.

45. The article according to claim 44, wherein the article is in the form of a D-lock, the rod forming at least part of the D-lock.

Description:
Fibre Ropes and Composite Materials Containing Fibre Ropes

Technical Field

[0001] This application relates to fibre-reinforced materials. In particular, this application relates to fibre ropes, fibre fabrics made from fibre ropes, composite materials containing fibre ropes, and to methods of their production. In particular, the invention relates to fibre ropes comprising non-polymeric, non-metallic and high modulus materials, such as carbon fibres.

Background

[0002] Non-polymeric, non-metallic and high modulus materials, such as carbon fibres and glass fibres, have previously been used to provide composite materials. These materials have been found to be useful in applications where a good strength/weight ratio is desirable. However, although composite materials comprising fabrics of such materials have been found to have reasonable in-plane mechanical properties (i.e. mechanical properties in the xy plane), the strength, stiffness, toughness properties of these composite materials in the out-of-plane direction (z direction) are much weaker. Commonly, composite materials contain a plurality of fibrous (e.g. woven) layers, encapsulated in a resin. However, such materials display anisotropic structural properties and also relatively poor out-of-plane (z direction) mechanical properties. Additionally, loading or impact of these laminated composite materials in the out-of-plane direction (z direction) has been found to result in delamination of the layers and/or catastrophic failure. This is typically the most common failure mode of composite structures, which limits the application of these materials in certain industrial sectors, e.g. automotive, aerospace and construction industries. These materials have poor ductility, since they have a low strain to failure and toughness.

[0003] Other attempts at addressing the problem of poor mechanical properties in the out-of-plane direction include z-pinning and 3D weaving. However, these manufacturing processes are expensive and complex and can cause other difficulties.

[0004] Additionally, to achieve more quasi-isotropic properties in-plane (i.e. so the properties are similar in all directions in the xy plane), laminates are produced by assembling layers, with the fibres in the different layers aligned in different directions. Furthermore, the manufacturing process is lengthy and complex, thus adding to the cost of manufacture. [0005] Accordingly there is a need for fibre-reinforced composite materials that address one or more of the problems mentioned above, and can be manufactured in an economical and efficient process.

Brief Description of the Figures

[0006] Figure 1A is a schematic diagram of a twisting machine which may be used to produce fibre ropes described herein;

[0007] Figure 1 B show a schematic diagram of an example of a rope described herein and its features, including fibres, tows, strands, first twist, second twist, helical angle (termed rope angle in this Figure), rope pitch and rope diameter.

[0008] Figure 1C shows photographs of examples of ropes prepared according to the method described herein, with the helical angle being shown on each photograph.

[0009] Figure 2 is a graph showing the tensile strength of examples of fibre ropes having different first and second twist densities;

[00010] Figure 3 is a graph showing the flexural stress verses flexural strain of examples of composite materials and reference composite materials;

[00011] Figure 4 is a graph showing the flexural stress verses flexural strain of examples of composite materials and reference composite materials;

[00012] Figure 5 is a photograph of an example of a composite material and a reference composite material following three point bending testing;

[00013] Figure 6 is a photograph of an example of a composite material and a reference composite material following three point bending testing;

[00014] Figure 7 is a graph showing load versus time data collected for examples of composite materials and reference composite materials during impact testing with an impact energy of 2J;

[00015] Figure 8 is a graph showing load versus deflection data determined for examples of composite materials and reference composite materials following impact testing with an impact energy of 2J; [00016] Figure 9 is a graph showing the maximum load recorded by examples of composite materials and reference composite materials on impact for different impact energies;

[00017] Figure 10 is a graph showing the maximum deflection shown by samples of examples of composite materials and reference composite materials on impact at different impact energies;

[00018] Figure 1 1 is a graph showing the energy absorbed by samples of examples of composite materials and reference composite materials during impact at different impact energies;

[00019] Figure 12 shows CT scans showing the cross section through a sample of examples of composite materials and reference composite materials after impact at 2J, 3J, 4J, 5 J and 7J;

[00020] Figure 12f shows CT scans of samples D and T impacted at 2J

[00021] Figure 12g shows CT scans of samples D and T impacted at 3J

[00022] Figure 12h shows CT scans of samples D and T impacted at 4J

[00023] Figure 12i shows CT scans of samples D and T impacted at 5J

[00024] Figure 12j shows CT scans of samples D and T impacted at 7J

[00025] Figure 13 is a graph showing stress versus strain for samples of examples of composite materials and reference composite materials undergoing a three point loading test;

[00026] Figure 14 shows the flexural strength of a sample of an example of a composite material and a reference composite material determine in a three point loading test;

[00027] Figure 15 shows the strain at maximum stress of a sample of an example of a composite material and a reference composite material determined from a three point bending test;

[00028] Figure 16 is a graph showing the flexural extension shown by samples of examples of composite materials and reference composite materials as load on the samples is increased in a three point bending test; [00029] Figure 17 is a graph showing the modulus of elasticity in bending of samples of examples of composite materials and reference composite materials determined from a three point bending test;

[00030] Figure 18 shows the flexural strength of a sample of an example of a composite material and a reference composite material determine in a three point loading test;

[00031] Figure 19 shows the flexural strength of a sample of an example of a composite material and a reference composite material determine in a three point loading test;

[00032] Figure 20 illustrates the orientation at which samples were cut from examples of composite materials and reference composite materials in order to evaluate the elastic properties of the materials at different orientations;

[00033] Figure 21 is a graph illustrating the elastic properties in different directions of samples of reference composite materials;

[00034] Figure 22 is a graph illustrating the elastic properties in different directions of samples of examples of composite materials; and [00035] Figure 23 is a graph showing the effect of orientation of materials on the damping coefficient determined for samples of examples of composite materials and reference composite materials.

Detailed Description

[00036] Before the fibre ropes, materials, methods and related aspects of the disclosure are disclosed and described, it is to be understood that this disclosure is not restricted to the particular process features and materials disclosed herein because such process features and materials may vary somewhat. It is also to be understood that the terminology used herein is used for the purpose of describing particular examples. The terms are not intended to be limiting because the scope is intended to be limited by the appended claims and equivalents thereof.

[00037] A fibre tow may be defined as a bundle of fibres. There are no particular limits to the number of fibres of in the tow. The fibre tow may comprise a plurality of fibres of a non-polymeric, non-metallic and high modulus material. The tow may further comprise fibres of other types of material, such as metallic fibres and/or polymeric fibres. [00038] A fibre strand may be formed from the twisting of a tow, the twist density of the fibres in the strand being termed a first twist density. Twist density may be termed the number of twists per meter.

[00039] A fibre rope may be formed from the twisting of two or more strands together, the twist density of the two or more strands in the rope being termed a second twist density. Twist density may be termed the number of twists per meter.

[00040] A fabric may be defined as a coherent collection of ropes as described herein. The fabric may be a non-woven fabric, a woven fabric, braided fabric, or a knitted fabric, or any combination thereof.

[00041] A rod may be defined as composite material comprising a single rope as described herein and a matrix material.

[00042] In an embodiment, the fibre strand has a helical angle with respect to the elongate axis of the fibre rope of at least about n°. Optionally n is 15. A helical angle may be defined as the angle of the axis of the strand with respect to the axis of the rope.

[00043] Figure 1 B shows the main features of an example of a rope described herein. Reference numeral 1 indicates the fibres that form one of the tows (2); during the first twist operation (5) the tow is twisted to form the strand (3). In this diagram, at least three strands are twisted together in the second twist operation (6) to form the rope (4). The orientation of the second twist is opposite to the one used for the first twist. As it is possible to see from the schematic, a single strand is helicoidally distributed around the rope's length (see highlighted strand in Figure 1 B).

[00044] The angle theta (θ) represents the angle formed by the strand with respect to the elongate axis of the rope (A) and it is related with the number of twists per metre by the equation:

twist=1/L=tan /nd Where L represents the rope pitch (the distance between two passages of the same strand along the rope's length) and d is the diameter (or thickness) of the rope.

As it is possible to see from Figure 1 C, increasing the number of twists per metre increases the angle θ. [00045] It is noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[00046] If a standard test is mentioned herein, unless otherwise stated, the version of the test to be referred to is the most recent at the time of filing this patent application. [00047] As used herein, the term "about" is used to provide flexibility to a numerical range endpoint by providing that a given value may be a little above or a little below the endpoint. The degree of flexibility of this term can be dictated by the particular variable.

[00048] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. [00049] Numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not just the numerical values explicitly recited as the end points of the range, but also to include all the individual numerical values or subranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of "about 1 wt% to about 5 wt%" should be interpreted to include not just the explicitly recited values of about 1 wt% to about 5 wt%, but also include individual values and subranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3.5, and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This same principle applies to ranges reciting a single numerical value. Furthermore, such an interpretation should apply regardless of the breadth of the range or the characteristics being described. [00050] Unless otherwise stated, any feature described herein can be combined with any aspect or any other feature described herein.

[00051] In a first aspect there is provided a fibre rope comprising a plurality of fibre strands. Each strand is formed by twisting a tow, the tow comprising a plurality of fibres of a non-polymeric, non-metallic and high modulus material. Each tow is twisted with a first twist density to form each of the fibre strands. The plurality of the fibre strands is twisted with a second twist density to form the fibre rope. Each fibre strand may have a helical angle with respect to the elongate axis of the fibre rope of at least about 15°.

[00052] In a second aspect there is provided a method of producing a fibre rope, the method comprising:

a) providing a plurality of fibre tows, each tow comprising a plurality of fibres of a non-polymeric, non-metallic and high modulus material;

(b) twisting each fibre tow with a first twist density to provide a plurality of fibre strands; and

(c) twisting the plurality of the fibre strands together with a second twist density to provide a fibre rope, optionally such that each fibre strand has a helical angle with respect to the elongate axis of the fibre rope of at least about 15°..

[00053] In a third aspect there is provided a fibre fabric comprising a fibre rope as described herein. As described herein, a single rope may be used to form a rod with the addition of a matrix material. Alternatively, a plurality of ropes may be assembled into a fabric, and then formed into a matrix material. [00054] In a fourth aspect there is provided a method of producing a fibre fabric comprising combining a plurality of fibre ropes as described herein.

[00055] In a fifth aspect there is provided a method of producing a fibre fabric comprising weaving a fibre rope as described herein.

[00056] In a sixth aspect there is provided a composite material comprising a fibre rope as described herein and a matrix material.

[00057] In a seventh aspect there is provided a composite material comprising a fibre fabric as described herein and a matrix material.

[00058] In an eighth aspect there is provided a method of producing a composite material comprising combining a fibre rope as described herein and a matrix material. [00059] In a ninth aspect there is provided a method of producing a composite material comprising combining a fibre fabric as described herein and a matrix material.

[00060] In a tenth aspect, there is provided an article comprising a composite material as described herein. [00061] The composite materials of the present invention may be in the form of rods as described herein, or comprise fabrics assembled from the ropes, as described herein.

[00062] The present inventors have surprisingly found that composite materials produced using the fibre rope described herein have much improved out-of-plane properties and behave more isotropically (both in plane and out-of-plane) than previous composite materials. In other words, they create a composite fibrous reinforcement with similar mechanical properties in all 3 directions. For example, when in the form of a composite material comprising the fabric, the composite material is characterised by same or similar mechanical properties (e.g. strength and stiffness) in in-plane and out of plane directions. For example, when in the form of a rod, the mechanical properties in the longitudinal (rope direction) and transverse direction (through the thickness) are very similar.

[00063] Additionally, it has been found that the rods experience a quasi elasto-plastic behaviour with non-catastrophic failure with respect to comparable material configurations (untwisted, unidirectional) with same volume fraction and weight.

[00064] Furthermore, it was observed that the rods possess an increased ductility and energy absorption.

[00065] Additionally, it has been found that the fabric-containing composite materials have the following advantages:

They simplify the current manufacturing processes by reducing or eliminating the lamination process (stacking a sequence of layers) since a quasi-isotropic material configuration can be achieved using a single or fewer 3D twisted rope fabric layers.

Under impact loading, the proposed single layer fabric does not experience internal delaminations unlike an equivalent classic layered material.

[00066] The advantages described above are illustrated in the Examples below. Fibre Tow

[00067] The fibre ropes described herein comprise a fibre tow comprising a plurality of fibres of a non-polymeric, non-metallic and high modulus material twisted together with a first twist density. The fibre tow, or plurality of fibre tows is/are twisted with a first twist density to form a fibre strand. In certain examples a fibre strand of the fibre rope may comprise a plurality of fibre tows, for example at least 2, or at least 3 fibre tows.

[00068] As used herein, the term "fibre tow" is used to refer to a bundle of fibres of a non-polymeric, non-metallic and high modulus material, for example, a bundle of carbon fibres, boron fibres (e.g. boron coated carbon fibres), glass fibres and/or ceramic fibres (e.g. quartz fibres). In certain embodiments a fibre tow comprises, consists essentially of, or consists of a plurality of fibres of a non-polymeric, non- metallic and high modulus material, for example, a plurality of carbon fibres. A fibre tow may comprise at least about 10 fibres of a non-polymeric, non-metallic and high modulus material, for example, a bundle of carbon fibres and/or glass fibres, for example at least about 50 fibres, at least about 100 fibres, at least about 500 fibres, at least about 1000 fibres, at least about 2000 fibres, at least about 3000 fibres, at least about 4000 fibres, or at least about 5000 fibres of a non-polymeric, non-metallic and high modulus material. In certain embodiments, the fibre tow may comprise up to about 50 000 fibres of a non-polymeric, non-metallic and high modulus material.

[00069] In certain embodiments, individual fibres of a non-polymeric, non-metallic and high modulus material have a diameter of at least about 1 μηι, for example at least about 2 μηι, at least about 3 μηι, at least about 4 μηι, or at least about 5 μηι. In certain embodiments, individual fibres of a non-polymeric, non-metallic and high modulus material have a diameter of up to about 50 μηι, for example up to about 30 μηι, up to about 20 μηι, or up to about 10 μηι. In certain embodiments, individual fibres of a non- polymeric, non-metallic and high modulus material have a diameter in the range of about 1 μηι to about 50 μηι, for example about 5 μηι to about 10 μηι. [00070] As used herein, the term "non-polymeric material" is used to refer to materials that that are not considered to be polymeric materials. Polymeric materials are materials formed of macromolecules composed of many repeating units, e.g. repeating organic (i.e. carbon containing) units, such as polyolefins such as polyethylene (e.g. high molecular weight polyethylene or ultra-high molecular weight polyethylene, e.g. Dyneema®), polypropylene or polybutylene, aramids (e.g. Kevlar® and Nomex®), polyamides.

[00071] As used herein, the term "high modulus materials" may refer to materials having a Young's modulus of greater than about 20 GPa, for example greater than about 30

GPa, greater than about 40 GPa, greater than about 50 GPa, greater than about 60 GPa, greater than about 70 GPa, greater than about 80 GPa, greater than about 90 GPa, greater than about 100 GPa, greater than about 120 GPa, greater than about 150 GPa, greater than about 170 GPa, or greater than about 200 GPa. The Young's modulus of fibre materials may be determined according to ASTM C1557-14.

[00072] As used herein, the term "non-metallic materials" is used to refer to materials which do not contain a metal, i.e. a metal in elemental or alloy form. Metallic materials include materials such as shape-memory-alloys (e.g. nickel titanium alloys) and other metals such as steel, copper and titanium. [00073] In certain embodiments, the fibres of a non-polymeric, non-metallic and high modulus material have a tensile strength of at least about 500 MPa, for example at least about 1000 MPa, at least about 1500 MPa, or at least about 2000 MPa. In certain embodiments, the fibres of a non-polymeric, non-metallic and high modulus material have a tensile strength of up to about 6000 MPa. The tensile strength of the fibres may be determined according to ASTM C1557-14.

[00074] The fibres of a non-polymeric, non-metallic and high modulus material may be uncoated fibres, for example such that individual non-polymeric, non-metallic and high modulus material fibres of the fibre tow are contactable with other fibres of a non- polymeric, non-metallic and high modulus material contained in the fibre tow. [00075] The fibre tows may be uncoated fibre tows, for example such that fibres of a non-polymeric, non-metallic and high modulus material contained in a fibre tow are contactable with other fibres of a non-polymeric, non-metallic and high modulus material contained in another fibre tow.

[00076] In certain embodiments, the fibre tow or a plurality of fibre tows is/are twisted with a first twist density of at least about 25 turns per metre (tpm), for example at least about 30 tpm, at least about 35 tpm, at least about 40 tpm, at least about 45 tpm, at least about 50 tpm, at least about 55 tpm, at least about 60 tpm, at least about 65 tpm, at least about 70 tpm, at least about 75 tpm, or at least about 80 tpm to form a fibre strand.

[00077] In certain embodiments, the fibre tow or plurality of fibre tows is/are twisted to form a fibre strand with a first twist density of up to about 200 tpm, for example up to about 180 tpm, up to about 160 tpm, up to about 150 tpm, up to about 130 tpm, or up to about 120 tpm.

[00078] In certain embodiments, the fibre tow or plurality of fibre tows is/are twisted to form a fibre strand with a first twist density in the range of about 25 tpm to about 200 tpm, for example about 40 tpm to about 180 tpm, or about 70 tpm to about 160 tpm. [00079] In certain embodiments, a fibre tow further comprises a polymerfibre, a metallic fibre or a combination thereof, wherein a polymeric fibre comprises a polymeric material (such as ultra-high molecular weight polyethylene (e.g. Dyneema®) and/or aramids (e.g. Kevlar® and Nomex®)) and a metallic fibre comprises a metallic material (such as titanium or a shape memory alloy, such as a nickel-titanium alloy). The polymeric material may be defined as a material formed of macromolecules composed of many repeating units, e.g. repeating organic (i.e. carbon containing) units, and the polymeric material may be selected from polyolefins such as polyethylene (e.g. high molecular weight polyethylene or ultra-high molecular weight polyethylene, e.g. Dyneema®), polypropylene or polybutylene, aramids (e.g. Kevlar® and Nomex®) and polyamides.

[00080] In certain embodiments, a fibre tow lacks a polymeric material or a metallic material.

[00081] In certain embodiments, the or each fibre tow comprises at least about 30 vol.% by total volume of the tow of fibres of a non-polymeric, non-metallic and high modulus material, for examples at least about 40 vol.%, at least about 50 vol.%, at least about

60 vol.%, for example at least about 70 vol.%, at least about 80 vol.%, at least about 90 vol.%, at least about 95 vol.% or at least about 99 vol.% of fibres of a non-polymeric, non-metallic and high modulus material.

Fibre Strand [00082] The fibre ropes described herein comprise a fibre strand. In certain examples the fibre ropes comprise a plurality of fibre strands, for example at least 2, at least 3 or at least 4 fibre strands. In certain embodiments the fibre rope comprise a greater number of fibre strands than the number of fibre tows of each of the fibre strands.

[00083] The fibre strand comprises a fibre tow or a plurality of fibre tows twisted with a first twist density.

[00084] The fibre rope comprises a fibre strand or a plurality of fibre strands twisted with a second twist density.

[00085] In certain embodiments, a fibre tow of the fibre strand has a helical angle with respect to the elongate axis of the fibre strand (i.e. before twisting of the fibre strand to form the fibre rope) of at least about 15°, for example at least about 20°, at least about 30°, at least about 35°, at least about 40°, or at least about 45°. In certain embodiments, a fibre tow of the fibre strand has a helical angle with respect to the elongate axis of the fibre strand (i.e. before twisting of the fibre strand to form the fibre rope) of up to about 60°.

[00086] In certain embodiments, the second twist density is at least about 10 turns per meter, about 15 turns per meter, about 20 turns per meter, for example 25 turns per metre (tpm), at least about 30 tpm, at least about 35 tpm, at least about 40 tpm, at least about 45 tpm, at least about 50 tpm, at least about 55 tpm, at least about 60 tpm, at least about 65 tpm, at least about 70 tpm, at least about 75 tpm, at least about 80 tpm, at least about 85 tpm, at least about 90 tpm, at least about 95 tpm or at least about 100 tpm.

[00087] In certain embodiments, the second twist density is up to about 200 tpm, for example up to about 180 tpm, up to about 160 tpm, up to about 150 tpm, or up to about 130 tpm.

[00088] In certain embodiments, the second twist density in the range of about 25 tpm to about 200 tpm, for example about 40 tpm to about 180 tpm, or about 70 tpm to about 160 tpm.

[00089] The fibre strand may be an uncoated fibre strand, i.e. the fibre strand may be uncoated such that non-polymeric, non-metallic and high modulus material fibres of the fibre strand contact non-polymeric, non-metallic and high modulus material fibres of other fibre strands when a plurality of fibre strands are twisted together with a second twist density to form a fibre rope. [00090] In certain embodiments a fibre strand may further comprise a polymer tow, a metallic tow or combinations thereof, wherein a polymer tow comprises a polymeric material and a metallic tow comprises a metallic material. A polymer tow, a metallic tow or combinations thereof may be twisted with a fibre tow or a plurality of fibre tows with a first twist density to form a fibre strand.

[00091] In certain embodiments the fibre rope further comprises a polymer strand, a metallic strand or combinations thereof, wherein a polymer strand comprises a polymeric material and a metallic strand comprises a metallic material. A polymer strand, a metallic strand or combinations thereof may be twisted with a fibre strand or a plurality of fibre strands with a second twist density to form a fibre rope.

[00092] In certain embodiments, the or each fibre strand comprises at least about 30 vol.% by total volume of the tow of fibres of a non-polymeric, non-metallic and high modulus material, for examples at least about 40 vol.%, at least about 50 vol.%, at least about 60 vol.%, for example at least about 70 vol.%, at least about 80 vol.%, at least about 90 vol.%, at least about 95 vol.% or at least about 99 vol.% of fibres of a non-polymeric, non-metallic and high modulus material.

Fibre Rope

[00093] Described herein is a fibre rope comprising a plurality of (i.e. at least two) fibre strands, each strand formed by twisting one or more fibre tows, each fibre tow comprising a plurality of fibres of a non-polymeric, non-metallic and high modulus material and being twisted with a first twist density to form the fibre strand, and the plurality of fibre strands being twisted together with a second twist density to form the fibre rope.

[00094] The term "rope" used herein may be used to refer to different thickness ropes which may elsewhere also be referred to as "twines" or "cordages". In certain embodiments, the fibre rope may have a diameter in the range of about 0.01 mm to about 100 mm, for example about 0.1 mm to about 50 mm.

[00095] Fibre ropes comprise, consist of, or consist essentially of fibres of a non- polymeric, non-metallic and high modulus material, for example carbon fibres and/or glass fibres. In certain embodiments, fibre ropes comprise, consist of, or consist essentially of carbon fibres, for example carbon fibres having a modulus of greater than about 30 GPa, greater than about 100, greater than about 200 GPa, greater than about 300 GPa, greater than about 400 GPa .

[00096] In certain embodiments, the fibre rope comprises two or more fibre strands being twisted with a second twist. Each strand comprises a fibre tow, or a plurality of fibre tows, that is/are twisted with a first twist, wherein the first twist has twist direction opposite to the second twist direction.

[00097] In certain embodiments, the fibre strand (i.e. after twisting of the fibre strand with a second twist to form the fibre rope) has a helical angle with respect to the elongate axis of the fibre rope of at least about 15°, for example at least about 20°, at least about 30°, at least about 35°, at least about 40°, at least about 45°, or at least about 50°. In certain embodiments, the fibre strand (i.e. after twisting of the fibre strand with a second twist to form the fibre rope) has a helical angle with respect to the elongate axis of the fibre rope of up to about 60°, optionally up to about 55 °. In an embodiment, the helical angle may be from 15 0 to 60°, optionally from 15 0 to 55°, optionally from 15 0 to 50 °. In an embodiment, the helical angle may be from 20 0 to 60°, optionally from 20 0 to 55°, optionally from 20 0 to 50 °. In an embodiment, the helical angle may be from 25 0 to 60°, optionally from 25 0 to 55°, optionally from 25 0 to 50 °. By having a helical angle of 15 ° or more, this promotes the anisotropic and other properties of the rope when in a composite material. By having a helical angle of less than 60°, this lessens any damage to the fibres that may be caused by twisting.

[00098] In certain embodiments, the ratio of the first twist density of the fibre tow(s) to the second twist density of the fibre strand(s) is in the range of about 1 :2 to about 2: 1 , for example about 1 :1 to about 2: 1.

[00099] In certain embodiments the fibre rope comprises a core around which the fibre strand(s) may be twisted. The core may comprise a non-polymeric, non-metallic and high modulus material, e.g. fibres of a non-polymeric, non-metallic and high modulus material. In certain embodiments the core may comprise a polymeric material or a metallic material. In certain embodiments the fibre rope consists of or consists essentially of strands (e.g. fibre strands) as described herein, i.e. the fibre rope lacks a core around which the fibre strand(s) are twisted.

[000100] In certain embodiments the fibre rope is a coated fibre rope. For example, the fibre rope may be coated with a polymeric material or a precursor to a polymeric material. [000101] In certain embodiments, the fibre rope comprises at least about 30 vol.% by total volume of the tow of fibres of a non-polymeric, non-metallic and high modulus material, for examples at least about 40 vol.%, at least about 50 vol.%, at least about 60 vol.%, for example at least about 70 vol.%, at least about 80 vol.%, at least about 90 vol.%, at least about 95 vol.% or at least about 99 wt.% of fibres of a non-polymeric, non-metallic and high modulus material.

[000102] Described herein is a method of producing a fibre rope, the method comprising: a) providing a plurality of fibre tows, each tow comprising a plurality of fibres of a non- polymeric, non-metallic and high modulus material;

(b) twisting each fibre tow with a first twist density to provide a plurality of fibre strands; and

(c) twisting the plurality of the fibre strands together with a second twist density to provide a fibre rope, such that each fibre strand has a helical angle with respect to the elongate axis of the fibre rope of at least about 15°.

[000103] In certain embodiments, steps (b) and (c) are carried out simultaneously, optionally multiple times simultaneously.

[000104] In certain embodiments, the method comprises providing a plurality of fibre tows and twisting the plurality of fibre tows together with a first twist density to form a fibre strand. [000105] In certain embodiments, twisting a plurality of fibre tows with a first twist density comprises separating each of the plurality of tows from each of the other fibre tows and twisting the plurality of fibre tows such that the plurality of fibre tows meet at a point at which they are twisted together. In certain examples, the plurality of tows may be separated from each other by passing each of the plurality of tows through a different hole in a twisting machine, e.g. a different hole in a twisting top of a twisting machine (i.e. twisting the plurality of tows together in a twisting machine using a multi- hole setup).

[000106] In certain embodiments twisting the fibre tow(s) comprises tensioning the fibre tow(s). [000107] In certain embodiments twisting the fibre strand(s) comprises tensioning the fibre strand(s).

[000108] In certain embodiments, the fibre tow(s) is/are twisted at a speed of about 100 rpm or greater, for example about 500 rpm or greater, about 600 rpm or greater, about 700 rpm or greater, or about 800 rpm or greater. In certain embodiments, the fibre tow(s) is/are twisted at a speed of up to about 2500 rpm, for example up to about 2000 rpm, up to about 1800 rpm, or up to about 1700 rpm. In certain embodiments, the fibre tow(s) is/are twisted at a speed of about 800 rpm to about 1700 rpm. [000109] In certain embodiments, the fibre strand(s) is/are twisted at a speed of about 100 rpm or greater, for example about 500 rpm or greater, about 600 rpm or greater, about 700 rpm or greater, or about 800 rpm or greater. In certain embodiments, the fibre tow(s) is/are twisted at a speed of up to about 2500 rpm, for example up to about 2000 rpm, up to about 1800 rpm, or up to about 1700 rpm. In certain embodiments, the fibre tow(s) is/are twisted at a speed of about 800 rpm to about 1700 rpm.

[0001 10] An example of a fibre rope producing apparatus, e.g. a twisting apparatus, is shown in figure 1. The twisting machine 10 shown in figure 1 comprises a twisting machine body 12 comprising hooks 14 which may be activated by an electric motor such that the hooks are rotated to twist fibres attached to the hooks 14. The twisting machine 10 also comprises a sledge 16. The distance between the sledge 16 and the twisting machine body 12 can be adjusted according to the desired fibre rope length. Tows of fibre to be twisted to produce at least two fibre strands that are then twisted together to produce a rope may be attached to a hook 18, the hook 18 attached to a weight 20 through the sledge 16. The weight 20 provides tension in the fibres to be twisted to form a fibre rope. The twisting machine 10 also comprises a top 22 which keeps bundles of fibres (i.e. each bundle of fibres being a tow) between the twisting machine body 12 and the top 22 apart as they are twisted to form strands 30. The top 22 is moveable between the sledge 16 and the twisting machine body 12. As the top 22 is moved towards the twisting machine body 12 (i.e. in the direction shown by arrow A), the strands 30 are twisted together to form a fibre rope 40 between the top 22 and the sledge 16. Such a twisting machine, for example the twisting machine 10 shown in figure 1 , allows the twisting orientation of the strands to be in the opposite direction to the twisting orientation of the fibre rope.

[0001 11] The fibre rope may contain the matrix material or substantially lack or lack the matrix material. During formation of the rope, for example, no matrix material may be present on or between the fibres in the rope. The present application provides the rope after formation and without any matrix material in or on the rope. The fibres of non-polymeric, non-metallic and high modulus material in the same strand, and in adjacent strands in the same rope, may contact one another. The present application also provides the rope in the form of a composite material, i.e. after the rope has been combined, e.g. impregnated with, a matrix material.

Fibre Fabric

[0001 12] The present invention provides a fibre fabric comprising a fibre rope as described herein.

[0001 13] A fibre fabric may be formed by combining a plurality of fibre ropes.

[0001 14] In certain embodiments, a fibre fabric may comprise comprises an interlaced fibre rope, e.g. a woven fibre rope. For example, the fibre fabric may be prepared by interlacing or weaving a fibre rope. In certain embodiments the fibre fabric is produced by weaving or braiding a fibre rope. In certain embodiments the fibre fabric is a 0°/90° fabric (i.e. the fabric is formed by interlacing or weaving warp (0°) fibres and weft (90°) fibres). In certain embodiments, the fibre ropes may be plain woven, twill woven, satin woven, basket woven, leno woven or mock leno woven. In certain embodiments, the fibre fabric may be a chopped strand mat, a tissue or braids formed from fibre ropes as described herein. In certain embodiments the fibre fabric may be a multilayer fibre fabric. In certain examples the fibre fabric may be a multiaxial fibre fabric, e.g. a fibre fabric comprising +45° and -45° layers (each layer may be made, for example, by weaving a 0°/90° fabric and then skewing the fabric to 45°).

[0001 15] In certain embodiments, a fibre fabric has a mass of at least about 0.0 5 g per cm 2 , for example at least about 0.01 g/ cm 2 , for example at least about 0.025 g/ cm 2 , at least about 0.05 g/cm 2 , at least about 0.075 g/cm 2 , at least about 0.1 g/cm 2 , or at least about 0.12 g/cm 2 . In certain embodiments, the composite material has a mass of up to about 5 g per cm 2 , for example up to about 3 g/ cm 2 , up to about 2.5 g/cm 2 , up to about 2 g/cm 2 , up to about 1.5 g/cm 2 , or up to about 1 g/cm 2 . In certain embodiments, the fibre fabric has a mass in the range of about 0.01 g per cm 2 to about 5 g per cm 2 .

[0001 16] The fibre fabric may contain the matrix material or substantially lack or lack the matrix material. During formation of the fabric, for example, no matrix material may be present on or between the fibres in the rope or between the ropes. The present application provides the fibre fabric after formation and without any matrix material in or on the fibre fabric. The fibres of non-polymeric, non-metallic and high modulus material in the same strand, and in adjacent strands in the same rope or in adjacent ropes, may contact one another. The present application also provides the rope in the form of a composite material, i.e. after the fibre fabric has been combined, e.g. impregnated with, a matrix material.

Composite Materials

[0001 17] The present invention provides a composite material comprising a fibre rope as described herein. In certain embodiments the composite material comprises a fibre fabric as described herein. In certain embodiments the composite material comprises a fibre rope and a matrix material. In certain embodiments, a composite material comprising a fibre rope and a matrix material may be provided in the form of a rod.

[0001 18] The composite material may be formable by first providing the rope as described herein, which may substantially lack any matrix material, and then combining it with the matrix material. The composite material may be formable by first providing the fabric as described herein, which may substantially lack or lack any matrix material, and then combining it with the matrix material. Combining the rope or fabric with a matrix material may comprise impregnating the rope or fabric with the matrix material and, optionally, curing the matrix material to harden it.

[0001 19] In certain embodiments the matrix material may comprise a resin, for example a thermoplastic resin or a thermosetting resin. In certain embodiments the matrix material may comprise a polymer, e.g. a thermoplastic polymer (also referred to herein as a thermoplastic resin) or a thermosetting polymer (also referred to herein as a thermoplastic resin). In certain embodiments the matrix material comprises a thermosetting polymer.

[000120] In certain embodiments, the composite material comprises, consists of, or consists essentially of a fibre rope or fibres ropes and a resin matrix.

[000121] In certain embodiments, the resin matrix comprises a resin selected from an epoxy resin, a polyester resin, a vinylester resin, a phenolic resin, a cyanate ester resin, a silicone resin, a polyurethane resin, a bismaleimide resin, or a polyimide resin.

[000122] In certain embodiments, the composite material comprises a cured resin matrix.

The cured resin matrix may comprise a resin as described above which has been cured, for example heat cured, catalyst cured or radiation cured.

[000123] In certain embodiments, the composite material is formed by coating or impregnating a fibre rope or fibre fabric with a resin, optionally a resin and a catalyst. In certain embodiments, the coated or impregnated fibre rope or fibre fabric is then cured.

[000124] In certain embodiments the composite material is a prepreg composite material, i.e. a composite material comprising a fibre rope or fibre fabric impregnated with an uncured or partially cured resin material. A prepreg composite material may be stored, for example at a reduced temperatures (e.g. a temperature lower than about 0°C, for example about -20 °C, for an extended period of time before curing at a later date). In certain embodiments the prepreg composite material comprises an uncured resin material and a catalyst. In certain embodiments, the prepreg composite material is curable on exposure to a curing temperature, for example a temperature greater than about 20 °C, for example a temperature greater than about 30 °C, for example a temperature greater than about 40 °C, for example a temperature greater than about 50 °C, for example a temperature greater than about 60 °C, for example a temperature greater than about 70 °C, for example a temperature greater than about 80 °C, for example a temperature greater than about 100 °C, or greater than about 120 °C. In certain embodiments, the prepreg composite material is curable on exposure to a temperature in the range of about 80°C to about 200 °C, for example about 120 °C to about 180 °C.

[000125] In certain embodiments, the composite material comprises at least about 10 vol.% of fibres of a non-polymeric, non-metallic and high modulus material by total weight of the composite material, for example at least about 20 wt.%, at least about 30 wt.%, at least about 40 wt.%, or at least about 50 wt.%, or at least about 60 wt.%. In certain embodiments, the composite material comprises up to about 90 wt.% of fibres of a non-polymeric, non-metallic and high modulus material by total weight of the composite material, for example up to about 80 wt.%, or up to about 70 wt.%. In certain embodiments, the composite material comprises from about 10 wt.% to about 90 wt.% of fibres of a non-polymeric, non-metallic and high modulus material by total weight of the composite material, for example from about 20 wt.% to about 80 wt.%.

[000126] In certain embodiments, the composite material comprises at least about 10 wt.% of matrix material, e.g. resin matrix, by total weight of the composite material, for example at least about 20 wt.%, at least about 30 wt.%, or at least about 40 wt.%. In certain embodiments, the composite material comprises up to about 90 wt.% of matrix material by total weight of the composite material, for example up to about 80 wt.%, up to about 70 wt.%, up to about 60 wt.%, or up to about 50 wt.%. In certain embodiments, the composite material comprises from about 10 wt.% to about 90 wt.% of matrix material by total weight of the composite material, for example from about 20 wt.% to about 60 wt.%.

[000127] In certain embodiments, the composite material may be a laminate composite material. In certain embodiments, the laminate material may comprise layers of fibre fabric.

[000128] In certain embodiments, a fibre rope or a plurality of fibre ropes may be impregnated with resin to form a prepreg composite material, e.g. a prepreg rod, which may then be cured, for example in an autoclave.

[000129] In certain embodiments, a fibre fabric or multiple fibre fabrics (e.g. multiple fibre fabrics disposed on one another to form a layered structure) may be impregnated with a resin, for example to form a prepreg composite material, and cured, for example in an autoclave.

[000130] In certain embodiments, a plurality of prepreg composite fibre fabrics may be disposed on one another and then cured to form a cured composite material.

[000131] In certain embodiments, the composite material has a thickness (e.g. the dimension measured in the out-of-plane direction of a fibre fabric) of at least about 0.1 mm, for example at least about 0.25 mm, at least about 0.5 mm, at least about 0.75 mm, or at least about 1 mm. In certain embodiments, the composite material has a thickness of up to about 50 mm, for example up to about 10 mm, or up to about 5 mm. In certain embodiments, the composite material has a thickness in the range of about 0.1 mm to about 10 mm.

[000132] In certain embodiments, the composite material has a mass of at least about 0.01 g per cm 2 , for example at least about 0.025 g/ cm 2 , at least about 0.05 g/cm 2 , at least about 0.075 g/cm 2 , at least about 0.1 g/cm 2 , or at least about 0.12 g/cm 2 . In certain embodiments, the composite material has a mass of up to about 5 g per cm 2 , for example up to about 3 g/ cm 2 , up to about 2.5 g/cm 2 , up to about 2 g/cm 2 , up to about 1.5 g/cm 2 , or up to about 1 g/cm 2 . In certain embodiments, the composite material has a mass in the range of about 0.01 g per cm 2 to about 5 g per cm 2 .

Article

[000133] Also provided is an article comprising a composite material as described herein. [000134] In an embodiment, the article is a component of an aircraft or a vehicle. The component may be a structural component. In an embodiment, the composite material comprises a fabric formed from a plurality of the ropes and the matrix material, and the article is a panel for use as an exterior surface on an aircraft or a vehicle. The component of the aircraft may be a component selected from a wing, winglet, engine cowling, fuselage, nose, parts of the engine such as a rotor blade, a door, a slat, spoiler, aileron, rudder, vertical stabilizer, horizontal stabilizer and elevator. The component of a vehicle may be selected from a part such as a panel for the exterior of a car (e.g. for use on/as the roof, door, bonnet, boot, and side panels), a door or part thereof, a wheel or part thereof, roof, the chassis or part thereof, a component for the interior of the car, including, but not limited to, interior panels (for example on the interior of the doors), seats, structural components (such as struts for supporting the roof) and dashboard.

[000135] In an embodiment, the composite material is in the form of a rod comprising a single rope and the matrix material. The rod may be straight or curved. In an embodiment, the article is in the form of a D-lock, the rod forming at least part of the D-lock; for example, it may form the curved part of the D-lock and/or the straight part of a D-lock (i.e. the straight bar into which the curved part fits when locked together).

Examples

[000137] The following illustrate examples of the fibre ropes, materials, methods and related aspects described herein. Thus, these examples should not be considered to restrict the present disclosure, but are merely in place to teach how to make examples of compositions of the present disclosure.

Fibre Strands

Example 1

[000138] A fibre strand was produced by twisting four commercially available tows together, each tow was made up of a set number of carbon fibres (T800HB-12K-50B, available from Toray, each tow comprising 12000 individual carbon fibres) having a linear density of 4600 dtex. The four tows once combined can be considered to be a larger, single tow. The four carbon fibre tows were twisted together with a first twist density of 160 turns per metre (tpm), at a speed of 1600 rpm, using a ring and doubling twisting machine using a tow tension generated by a spring having a weight of 90 g, a spring diameter of 0.9 mm and using a metal 6500 mg cursor with a single hole set up to form a carbon fibre strand. The maximum load supportable by the carbon fibre strand was evaluated using a tensile machine (JBA 850 - J Bot SA instruments Tensile Machine with a load cell of 5kN)). The maximum load supported by the strand is shown in table 1 below.

Example 2

[000139] A fibre strand was produced and tested as for Example 1 , except the four tows were twisted together with a first twist density of 100 tpm. The maximum load supported by the strand is shown in table 1 below.

Example 3

[000140] A fibre strand was produced and tested as for Example 1 , except the four tows were twisted together using a multi-hole step up. The maximum load supported by the strand is shown in table 1 below.

Example 4 [000141] A fibre strand was produced and tested as for Example 1 , except the four tows were twisted together with a first twist density of 120 tpm using a multi-hole step up. The maximum load supported by the strand is shown in table 1 below.

Example 5

[000142] A fibre strand was produced and tested as for Example 2, except the four tows were twisted together using a multi-hole step up. The maximum load supported by the strand is shown in table 1 below.

Example 6

[000143] A fibre strand was produced and tested as for Example 1 , except the four tows were twisted together with a tow tension generated by a spring having a weight of 160 g. The maximum load supported by the strand is shown in table 1 below.

Example 7

[000144] A fibre strand was produced and tested as for Example 1 , except the four tows were twisted together using a multi-hole step up and the tow tension generated by a spring having a weight of 160 g. The maximum load supported by the strand is shown in table 1 below.

Example 8

[000145] A fibre strand was produced by twisting four tows, each tow was made up of carbon fibres (T800HB-12K-50B, available from Toray) having a linear density of 4600 dtex. The four carbon fibre tows were twisted together by hand with a first twist density of 40 turns per metre (tpm). The maximum load reached of the carbon fibre strand before breaking was evaluated using a tensile machine (JBA 850 - J Bot SA instruments Tensile Machine with a load cell of 5kN). The maximum load supported by the strand is shown in table 1 below.

[000146] Table 1

Carbon fibre First twist Feeding setup Tow tension* Maximum Load strand density (g) (N)

Example 1 160 Single hole 90 383

Example 2 100 Single hole 90 672.5

Example 3 160 Multi-hole 90 451.9 Example 4 120 Multi-hole 90 675.3

Example 5 100 Multi-hole 90 748.2

Example 6 160 Single hole 160 248.9

Example 7 160 Multi-hole 160 383

Example 8 40 Handmade 1463.9

* Tow tension generated by a spring having a weight shown in this column

[000147] As it is possible to see from the different values of the maximum load achieved by the samples, the disposition of the different tows during the twisting operation plays an important role in the mechanical properties of the final product. In particular, the multiple holes configuration is able to provide a lower level of friction between the different tows, reducing the angle during the twisting operation. This leads to a lower level of damaged fibres during the manufacturing process, enhancing the maximum load (tensile strength) of the final product.

[000148] The results in table 1 show that decreasing the value of the tpm, increases the maximum load supported by the final product.

[000149] The results provided in table 1 show that the tension applied to each tow during the twisting procedure affects the maximum load of the strand produced. As can been seen from table 1 , the maximum load of the resulting strand is increased as the tow tension generated by a spring having a weight of 160 g is reduced to 90 g for Examples 1 and 3 and 6 and 7. Reducing the tension on each tow, lowers the stress levels in the carbon fibres during the twisting operation (each tow comprises 12000 individual fibres), reducing the number of damaged fibres during the manufacturing process.

Fibre Ropes

[000150] Fibre ropes may be produced by twisting together fibre strands produced according to Examples 1-8 above. In order to avoid instabilities in the geometry of the fibre ropes, the fibre ropes may be manufactured with the strands twisted (second twist) in the opposite direction of the direction used to twist the tows to form the strands (first twist). For example, if the during the first twisting the tows were twisted in a clockwise direction to form a single strand, when more of these strands are twisted together in the second twist operation, the twisting direction will be anti-clockwise and vice-versa. The first and second twist being in opposite directions results in fibre ropes which are less likely to untwist or kink. This helps to give stability to the twisted structure. According to the ISO 2 (International Organization for Standardization, ISO 2:1973 Textiles— Designation of the direction of twist in yarns and related products, 1973) a left-handed twist is indicated with the upper case letter S, while the right handed twist with the letter Z. Unless otherwise stated, each rope had a helical angle of at least 15°. Example 9

[000151] A fibre rope was produced by first producing fibre strands and then twisting three strands together in a direction opposite to the direction used to twist carbon fibre tow to produce the strands. Each of the three strands was produced by twisting a tow containing 12000 individual carbon fibres (carbon fibre T700 12K from Toray) with a twist density (first twist density) of 160 tpm, at a speed of 1400 rpm and with a tow tension generated by a spring having a weight of 670 gr. The three strands were twisted together with a twist density (second twist density) of 50 tpm at a speed of 1400 rpm and a strand tension generated by a spring having a weight of 670 gr. The machine used to produce the strands and the final rope was a ring and doubling up twisting machine. The tensile strength of each of 5 samples of 4m lengths of the rope was determined using a computer controlled tensile test system (MultiTest 25-i from Mecmesin) and the mean tensile strength determined, the results are shown in table 2 below.

Example 10 [000152] A fibre rope was produced and tested as for Example 9, except that the second twist density was 75 tpm.

Example 1 1

[000153] A fibre rope was produced and tested as for Example 9, except that the second twist density was 100 tpm. Example 12

[000154] A fibre rope was produced and tested as for Example 9, except that the second twist density was 125 tpm.

Example 13

[000155] A fibre rope was produced and tested as for Example 9, except that the second twist density was 150 tpm. Example 14

[000156] A fibre rope was produced and tested as for Example 9, except that the second twist density was 175 tpm.

Example 15 [000157] A fibre rope was produced and tested as for Example 9, except that the second twist density was 200 tpm.

[000158] Table 2

[000159] The results provided in table 2 demonstrate that as the second twist increases from 50 to 100 the tensile strength increases, while the tensile strength decreases as the second twist density increases to 125 and greater.

Example 16

[000160] A fibre rope was produced and tested as for Example 9, except that the first twist density was 100 tpm. Example 17

[000161] A fibre rope was produced and tested as for Example 10, except that the first twist density was 100 tpm.

Example 18

[000162] A fibre rope was produced and tested as for Example 1 1 , except that the first twist density was 100 tpm. [000163] Table 3 below shows the mean tensile strength for each of the fibre ropes of Examples 16-18.

[000164] Table 3

[000165] Figure 2 is a graph showing the effect of first and second twist density on the tensile strength of the rope fibres of Examples 9-1 1 and 16-18. As can be seen from figure 2, the fibre ropes produced with a first twist density of 100 tpm show a tensile strength that is higher than the fibre ropes manufactured with a second twist of 160 tpm. Example 19

[000166] A fibre rope was produced by first producing fibre strands and then twisting three strands together in a direction opposite to the direction used to twist carbon fibres to produce the strands. Each of the three strands was produced by twisting four tows, each tow containing 6000 individual carbon fibres (carbon fibre T700 6K from Toray) with a twist density (first twist density) of 120 tpm, at a speed of 1700rpm and with a tow tension generated by a spring having a weight of 400 g. The three strands were twisted together with a twist density (second twist density) of 100 tpm at a speed of 1700rpm and a strand tension generated by a spring having a weight of 400 g. The machine used to produce the strands and the final rope was a ring and doubling up twisting machine. The tensile strength of each of 5 samples of 4m lengths of the rope was determined using a computer controlled tensile test system (MultiTest 25-i from Mecmesin) and the mean tensile strength determined to be 0.51 N/mm 2 .

Example 20

[000167] A fibre rope was produced and tested as for Example 19, except that the strands were produced by twisting three carbon fibre tows (each tow containing 6000 individual carbon fibres (carbon fibre T700 6K from Toray) with a first twist density of 120 tpm and four strands were twisted together with a second twist density of 100 tpm to form a fibre rope. The mean tensile strength of the fibre rope obtained was found to be 0.73 N/mm 2 .

[000168] The mean tensile strength of the fibre ropes of Examples 19 and 20 suggests that keeping the cross-section of the fibre rope constant and reducing the cross-section of a single strand allows the number of strands to be increased and the tensile strength of the fibre rope to be increased.

Composite Materials - Rods

Example 21

[000169] A rod was manufactured by first producing a carbon fibre rope and then impregnating the carbon fibre rope with epoxy resin (Araldite® LY 5052). A fibre rope was produced by first producing fibre strands and then twisting three strands together in a direction opposite to the direction used to twist carbon fibres to produce the strands. Each of the three strands was produced by twisting 56 tows, each tow containing 1200 individual carbon fibres (T800 12 K 50B from Toray). The three strands were twisted together with a twist density (second twist density) of 17-22 tpm at a strand tension generated by a weight of 2 kg. A schematic diagram of the machine used to produce the strands and the final rope is shown in figure 1 as described above. This machine allows the twisting orientation of the single strand to be in the opposite direction to the twisting orientation of the fibre rope.

[000170] The carbon fibre rope was inserted into a cylindrical mould (length of 260 mm and diameter of 12.7 mm) and impregnated with about 20 g (about the same mass as the mass of the carbon fibre rope) 50 wt.%) epoxy resin (Araldite® LY 5052). The impregnated material was held in the mould at 80°C for 1 hour and postcured at 100°C for 4 hours following the cycle indicated on the epoxy resin manufacturer's datasheet to form a rod which was then removed from the mould.

Reference Example 22

[000171] A reference rod was produced as per Example 21 except that instead of using the fibre rope a tow of carbon fibres (the same carbon fibres used to produce the fibre rope of Example 21) was provided having the same number of individual carbon fibres as the fibre rope of Example 21. The tow of fibres was not twisted and instead used as purchased, the fibres were aligned under tension and inserted into the mould to produce a reference rod in the same way the rod of Example 21 was produced. Testing of rods - three point bending test

[000172] Three point bending tests were carried out for rods produced according to Example 21 and Reference Example 22 using an Instron Universal Tester (100kN Dartec Universal MJ6813) and following the ASTM D790 (D790 (2010) Standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials) adapted to a cylindrical geometry rather than a rectangular geometry. Each sample was placed on two supporting pins at a set distance apart and a third loading support was lowered from above at a constant rate until sample failure and the applied load measured to provide values for the flexural stress-strain response of the material.

[000173] Figure 3 is a graph showing the flexural stress verses flexural strain of the rods of Example 21 and Reference Example 22 and indicating the values for average flexural stress for each of the rods. The flexural stress (σ/) was evaluated from the load-displacement curves by the following equation:

3LS where L represents the value of the load recorded by the machine during the test (kN), S is the span length between the two support (mm) and d is the diameter of the specimen (mm).

[000174] Flexural strain, e^was evaluated by following the equation below:

6(zd)

£ f =— where S is the span length between the two support (mm), d is the diameter of the specimen (mm), and z represents the vertical displacement recorded by the machine during the test.

[000175] As it is possible to see from the different trends of the curves in the graph of figure 3, the sample rod of Example 21 shows lower values for flexural stress than the sample rod of Reference Example 22. This behaviour can be explained with the presence of the twists along the axial direction which increase the total flexibility of the sample of Example 21 making this rod more susceptible to bending than the rod of Reference Example 22 containing straight fibres. [000176] Figure 4 is a graph showing the flexural stress verses flexural strain of the rods of Example 21 and Reference Example 22 and indicating the values for average flexural strain for each of the rods.

[000177] As it is possible to see from the different trends of the curves shown in figure 4, the sample rod of Example 21 allows a larger deformation of the composite when it is subjected to a load applied perpendicular to the longitudinal axis of the rod compared to the sample rod of Reference Example 22.

[000178] The higher pliability of the sample rod of Example 21 compared to the sample rod of Reference Example 22 is also reflected in the behaviour of the bending modulus Eb. Eb for the sample rod of Reference Example 22 was found to be 31 .73 GPa and

Eb for the sample rod of Example 21 was found to be 22.41 GPa (a decrease of almost 30%). The bending modulus, Eb.was calculated according to the equation:

S 3 m where S is the span length between the two support (mm), d is the diameter of the specimen (mm), and m represents the gradient (i.e. slope) of the initial straight line portion of the load deflection curve.

[000179] An important consequence of the different grade of flexibility shown by the two samples is the variation of the specific strain energy (strain energy for unit of volume) for rods formed from straight fibres (e.g. rods of Reference Example 22) and rods formed from twisted fibres (e.g. rods of Example 21). The strain energy per unit volume

(which is evaluated from the area of the stress-strain curve shown in figure 3 or figure 4) of the sample rod of Example 21 was found to be 0.0084 J/mm 3 compared to 0.0173 J/mm 3 for the sample rod of Reference Example 22 (an increase of more than 50%).

[000180] From the results discussed above for the rods of Example 21 and Reference Example 22, it is possible to conclude that the twisting procedure strongly affects the flexural behaviour of rods produced using fibre ropes according to the present invention. In particular, the rods of Reference Example 22 show fragile fracture which is typical of carbon composite structures with cracks propagating through the thickness of the specimens breaking the fibres in the area under tensile stress. At the end of the tests the samples do not survive and are formed by two straight parts separated by a breakage zone in which the fibres damage occurred (see figure 5 which shows a rod of Reference Example 22 following the three point bending test). On the other hand, rods produced using the fibre ropes of the present invention (e.g. rods of Example 21) show a pseudoplastic behaviour similar to the one observed in metals and polymers. Indeed, the sample is able to accommodate large displacements by deforming its structure due to the twisted carbon fibres that act as a sort of spring. The deformation in this case is accompanied by cracks only in the resin rich areas which are localised between the twists. At the end of the tests the samples present a plastically deformed curve in the correspondence of the closest twist from the load application point. All the sample rods of Example 21 survived the test showing no fractures or cracks in the fibrous reinforcement (see figure 5 which shows a rod of Example 21 following the three point bending test).

[000181] It is important to note that although the samples of the present invention (Example 21) showed a very large displacement in comparison with the traditional unidirectional samples (Reference Example 22), the final shape of the specimens showed a smaller bending angle coupled with undamaged fibres: this is due to the very large elastic recovery that happens in the samples of the present invention once the load is removed from the mid-section of the sample which is given by the twisted arrangement of the fibrous reinforcement. Figure 6 shows a rod sample of Example 21 and a rod sample of Reference Example 22 following the three point bending test.

Testing of rods - Charpy test

[000182] Rods of Example 21 and Reference Example 22 were also tested for impact resistance using the Charpy test to calculate the Charpy impact strength. It was found the rods of the present invention (Example 21) showed an enhancement in the absorbed impact energy by more than 200% compared to rods formed with straight carbon fibres (Reference Example 22). The samples tested were visually analysed to assess the indent area and the presence of cracks around the impact zone. It was observed that the rods of the present invention (Example 21) showed a pseudoplastic indent with very few cracks around the impact area and no visible delamination through the thickness of the samples while the rod of Reference Example 22 showed a fragile fracture with sharp edges and cracks propagating from the impact area through the entire length of the samples. The indents formed in the rods of the present invention (Example 21) were also strongly reduced in extent compared with the rods of Reference Example 22 (the rods of the present invention showed an indent area decreased in size by more than 40% compared to the indent area of the rods of Reference Example 22).

Fibre Fabrics Example 23

[000183] A fibre fabric was produced by weaving fibre ropes produced by first producing fibre strands and then twisting three strands together in a direction opposite to the direction used to twist carbon fibres to produce the strands. Each of the three strands was produced by twisting a tow containing 3000 individual carbon fibres (carbon fibre

T300 3K from Toray) with a twist density (first twist density) of 120 tpm, at a speed of 1400 rpm and with a tow tension generated by a spring having a weight of 90 gr. The three strands were twisted together with a twist density (second twist density) of 100 tpm at a speed of 1400 rpm and a strand tension generated by a spring having a weight of 90 gr. The machine used to produce the strands and the final rope was a ring and doubling up twisting machine. The fabric was manufactured using a traditional weaving machine to provide a fabric having a plain weave.

Reference Example 24

[000184] A reference fibre fabric was produced by weaving tows of carbon fibre containing 3000 individual, untwisted carbon fibres (carbon fibre T300 3K from Toray) in the same way as Example 23 to provide a fabric having a plain weave.

Composite materials - Fibre Fabrics

Example 25

[000185] The fibre fabric of Example 23 was impregnated with epoxy resin (MTC510 from SHD Composites) such using an amount of epoxy resin approximately equal to the weight of the fibre fabric and cured in an autoclave to provide a composite material.

Reference Examples 26

[000186] The reference fibre fabric of Reference Example 24 was impregnated with epoxy resin in the same way as Example 25. In order to provide a composite material having the same thickness as the composite materials of Example 25, three impregnated reference fibre fabrics were stacked together and cured to provide a reference composite material.

Example 27

[000187] Two layers of the impregnated material of Example 25 were stacked together and cured in a vacuum bag to provide a composite material. Example 28

[000188] Three layers of the impregnated material of Example 25 were stacked together and cured in a vacuum bag to provide a composite material.

Reference Examples 29 The reference fibre fabric of Reference Example 24 was impregnated with epoxy resin in the same way as Reference Example 24. In order to provide a composite material having the same thickness as the composite materials of Example 27, six impregnated reference fibre fabrics were stacked together and cured to provide a reference composite material.

Reference Examples 30 The reference fibre fabric of Reference Example 24 was impregnated with epoxy resin in the same way as Reference Example 24. In order to provide a composite material having the same thickness as the composite materials of Example 28, nine impregnated reference fibre fabrics were stacked together and cured to provide a reference composite material.

Testing of fibre fabric composite materials - Impact Characterisation [000189] Samples of composite materials produced according to Example 25 and Reference Example 26 were tested using a Drop-Weight LVI Impactor Dynatup 9250HV. The drop weight was of 4.415 kg and impactor's head was equipped with a hemispherical tip with a diameter of 20mm.

[000190] Samples were dimensioned to 100x150mm and clamped to a fixed support and tested according to the BS EN ISO 6603-2:2000. The drop height was altered compared to the standard due to the low thickness of the samples, the drop height used in the test was below 300 mm. As the weight of the impactor was kept constant (4.415 kg) during the test, in order to impact the samples at different energy levels, the velocity of the impact (vo) was tuned according to the equation:

where m is the mass of the impactor, E is the required impact energy. The impact height was further adjusted by performing velocity tests on the rig in order to balance the error given by friction and mechanical inertia.

[000191] The dimensions of the tested samples are listed in table 3 below. [000192] Table 3

[000193] Samples 3, 4, 11 and 12 were tested with an impact energy of 2J (impact velocity of 0.933 m/s). Each of the samples tested survived the impact test with impact energy of 2J with no perforation.

[000194] Samples 5, 6, 13 and 15 were tested with an impact energy of 3J. The mean impact velocity was evaluated with a velocity sensor and measured 1.146 m/s. Each of the samples survived the test with no perforation.

[000195] Samples 1 , 2, 9 and 10 were tested with an impact energy of 4J. The mean impact velocity was evaluated with a velocity sensor and measured 1.326 m/s. All samples survived the test with no perforation.

[000196] Samples 7, 8, 14 and 16 were tested with an impact energy of 5J. The mean impact velocity was evaluated with a velocity sensor and measured 1.477 m/s. All samples survived the test with no perforation. [000197] Samples 1 and 9 were tested with an impact energy of 7J. The mean impact velocity was evaluated with a velocity sensor and measured 1.743 m/s. All samples survived the test with no perforation.

[000198] For each of the tests. Data collected from the load cell during each of the impacts on the samples was used to provide load versus time curves. An example of a load versus time curve is shown in figure 7 which is a graph showing load versus time data collected for samples 3, 4, 1 1 and 12 tested with an impact energy of 2J. From this data, the deflection of the test sample was evaluated using the equation 3 of the BS EN ISO 6603-2:2000. Data can then be expressed as load versus deflection curves which can be used to determine the area under the curve which represents the energy expended up to specific times tj from the equation 4 of the BS EN ISO 6603-2:2000. An example of a load versus deflection curve is shown in figure 8 which is a graph showing load versus deflection data determined for samples 3, 4, 11 and 12 (tested with an impact energy of 2J) using the load versus time curve shown in figure 7 and equation 2.

[000199] Table 4 below summaries the results calculated from the Dynatup Instron machine for samples impacted with different energies.

[000200] Table 4

C ittilf om p ose maera o 2

1.927 0.934 0.616 1.939 0.742 1.730 7.101 5.676 4.687 R f E l 26 eerenceam p ex

3

2.891 1.144 0.623 1.924 0.708 3.492 6.997 10.184 4.555

4

3.888 1.327 0.641 2.091 0.824 4.408 7.269 13.230 4.853

5

4.767 1.470 0.652 2.01 1 0.958 4.719 7.027 14.294 5.043

7

6.694 1.742 0.675 1.921 0.950 5.022 6.646 15.786 4.799

[000201] Figure 9 illustrates the trend of the maximum load recorded (i.e. the maximum load recorded at the sample on impact) for all the impacts at different energies for both samples of Example 25 (samples 1-8) and samples of Reference Example 26 (samples 9-16). As can be seen from figure 9, the traditional laminates of Reference Example 26 show a higher value of the maximum load for all impacts.

[000202] Figure 10 shows the deflection at failure against impact energy (i.e. the maximum deflection shown by the sample on impact at each energy). As can be seen from figure 10, the deflection at failure shows an inverse behaviour compared to the maximum load behaviour for the samples. The samples of Example 25 show a greater maximum deflection for impacts of energy 3J to 7J compared to the samples of Reference Example 26, while the samples of Example 25 and Reference Example 26 show a similar value for deflection for the 2J impacts.

[000203] Analysing the trends of both Maximum Load and Deflection at Failure, it appears that while the samples of Reference Example 26 react with a high strength at low deflection, the samples of Example 25 respond in an opposite way, by absorbing the impacts with higher values of deformation. This higher values of the deformation together with a lower value of strength confirm the results obtained with the flexural tests (three point bending on both composite rods and composite fabrics) in which the same trends was observed.

[000204] Figure 1 1 illustrates the values of the energy absorbed during the impact (EN failure in Table 4) at each impact energy. Analysing these results, the different behaviour between the traditional straight fibres of the samples of Reference Example 26 and the twisted arrangement of samples of Example 25 seems to be opposite to what observed during the flexural tests, as the energy is more or less the same for the impacts at low energy levels (2 and 3J) and starts to diverge when it increases up to 7J. However, these results need to be compared with the internal damage assessment observed with the CT-Scan images shown in figure 12 in order to understand how the energy was absorbed during the impact (with or without the generation of permanent internal damage). [000205] In order to investigate the extent of the internal damaged area, each impacted sample was analysed with CT Scanner - Nikon XT H 225kV, X-ray computed tomography (X-ray CT) and computerized axial tomography scan (CAT scan). The computer-processed combinations of many X-ray images taken from different angles were used to produce cross-sectional (tomographic) images (virtual "slices") of the impacted samples, allowing precise assessment and identification of internal damaged areas. During the different analyses, the samples were analysed overlapping different specimens impacted at the same energy in order to have a direct comparison of the internal damage extension.

[000206] Figure 12 shows a CT scan showing the cross section through a sample at the area of impact of a sample of Example 25 and a sample of Reference Example 26 after impact at 2J, 3J, 4J, 5J and 7 J as indicated on each of the images.

[000207] As it is possible to see from figure 12, the intrinsic laminate structure of the samples of Reference Example 26 (lower sample in each of images a-e) leads to the generation of internal damage at the interface between adjacent laminae. The opening of these new surfaces dissipates a large amount of energies but at the same time weakens the material, reducing its residual mechanical properties. At the same time, because these damaged areas are undetectable by the naked eye due to being hidden inside the laminate structure of the material, they can lead to sudden critical failure of the part. Analysing the behaviour of the material of Example 25 (upper sample in each of images a-e), on the other side, it is possible to see that it reacts to an impact loading in a very different way by opening superficial cracks that can be easily detectable from the top surface. Increasing the impact energy these cracks can propagate following the twists of the fibrous reinforcement along the matrix rich areas. This generates a very localised damaged area in correspondence with the impact area while the zones far from the impact location stay undamaged.

[000208] As can be seem from the images in figure 12, the different geometry of the two typologies of fibrous reinforcement strongly affects the behaviour of the composite part when it is subjected to an out-of-plane impact load. [000209] From images 12f of the sample of Reference Example 26, it is possible to see the presence of internal delaminations along the interface between the different laminae of the samples even at the low 2J energy of impact (see image (a)). Although the delaminations visible in image (12f) for Reference Example 26 extend relatively far from the impact point, these delaminations are not critical per se because of the low energy of the impact (2J), however they can act as stress intensification points during the normal operation in the working environment leading to sudden catastrophic failure of the part. On the other hand, for the sample of Example 25, because of its intrinsic "bulk" geometry (i.e. the absence of interlaminar interfaces generated from the twisted arrangement of the fibres that forms the single fabric used to manufacture the sample), damage is only see in the impact area, and the damage shown is only superficial cracks with no hidden internal damaged areas.

[000210] Image 12g shows the same trend observed in the scans for the 2J impacted samples (image (12f)). Indeed, as it is possible to see from the internal damage distribution, increasing the impact energy up to 3J increases the extent of the internal delaminations for the sample of Reference Example 26. For the sample of Example 25 which cannot dissipate impact energy through the opening of new internal surfaces (because of its twisted bulk structure), the twisted sample presents superficial cracks strongly localised in the impact location with no internal damage as can be seen from figure 12g.

[000211] In figure 12h, it is possible to see the presence of a very large delaminated area far from the impact location for the sample of Reference Example 26 which was generated by the contact with the impactor's head during the 4J impact duration. The only way for the laminate of Reference Example 26 to absorb the impact energy was to open new surfaces at the interface between two subsequent laminae, generating internal delaminated areas. These delaminations extend far from the impact point along the length of the sample weakening it and reducing its residual properties. Because of the twisted structure of the fabric of the composite of Example 25, at the same position, the sample of Example 25 does not show any internal damage but only relatively large cracks which are generated on the surface because of the contact with the impactor's head. Since there is no possibility to dissipate the impact energy via the creation of delaminations, these cracks become larger in correspondence with the impact location going along almost the entire thickness, with secondary cracks propagating from the impact location along the width of the sample (visible from CT scans of the top surface of the sample). [000212] In figure 12i it is possible to see from the different fracture mechanisms, in the area of the impact the effect of a 5J impacts is far more catastrophic than the ones at lower energies. Indeed at the impact location, the sample of Example 25 presents large cracks that in some cases cross the entire thickness of the sample. The cracks tend to go around the twisted fibres bundles and propagate through the matrix rich areas following the twists of the tows, leading to matrix-fibres debonding. Moving from the impact location the presence of these damages is reduced with no visible internal damages. The sample of Reference Example 26, in the location of the impact, shows delaminations that are extended and propagate far from the impact area, shattering all the plies in correspondence with the impactor's head contact area. In addition, internal delaminations are accompanied by large cracks that starts from the surface and propagates through the entire sample. Secondary symmetrical cracks can also be seen to open from the bottom surface far from the impact area.

[000213] From the CT scans of the samples after impact at 7 J (see figure 12j) it is possible to see that the sample of Example 25 shows debonding at the fibres-matrix interface as observed following the 5J impact. Also following the 7J impact, the cracks on the surface tend to follow the twisted structure of the fibres tow, propagating through the matrix rich areas, although where the load is localised in a small area (i.e. the point in contact with the impactor's head) the twisted fibres bundle are split in two. Overall there are no internal damage or delaminations far from the impact location with only some very small cracks that propagate for a small extent along the sample's thickness from the bottom surface. The sample of Reference Example 26 presents a behaviour very similar to the one observed for the impacts at 4J and 5J. A large portion of the impact energy is absorbed by the opening of large delaminations which are extended on a large area covering almost half of the sample. In the impact area, the bottom layer is almost completely detached from the laminate and cracks both in the matrix and in the fibres bundles propagates with the classical tree pattern observed in traditional composite laminates.

Testing of fibre fabric composite materials - Three point bending test

[000214] The experimental campaign was conducted using an Instron Universal Tester (3369) and following the ASTM D790 standard (D790 (2010) Standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials) on several samples of composite materials produced according to Examples 25, 27 and 28 and Reference Examples 26, 29 and 30 in order to analyse the effect of the twisted geometry on the flexural behaviour of these composite materials. Each sample was placed on two supporting pins at a set distance apart and a third loading support was lowered from above at a constant rate until sample failure. The applied load generates tensile stress in the convex side of the specimen and compression stress in the concave side, with an area of shear stress along the midline. Shear stress was minimized by controlling the span-to-depth ratio (the length of the outer span divided by the thickness of the specimen) in order to ensure that the primary failure of the specimens occur from tensile or compression stress.

[000215] The three-point bending flexural test provides values for the modulus of elasticity in bending Eb, the flexural stress Of and the flexural strain £f. The flexural stress (o/) was evaluated from the load-displacement curves by the following equation

4 of the ASTM D790 standard.

[000216] The Flexural strain and the Bending modulus (also called tangent modulus of elasticity) were evaluated by following the equations 5 and 6 of ASTM D790 standard. The evaluation of the bending modulus requires to identify the slope of the tangent to the initial straight-line portion of the load-deflection curve. The area of interest in which the slope is evaluated is indicated by an arrow in the Load-displacement curve in Figure 16.

[000217] The modulus determination can be affected by the shear deflections during the test for small span-to-depth ratio. Indeed, in order to minimise the influence of the shear deformation, where it possible, the specimens where divided in two batches per each thickness. The specimens were tested using a large span-to-depth ratio (at least 30) and a second batch with a shorter span in comparison to the first one, in order to induce tensile failure in the outer fibres of the sample along its lower face, for the evaluation of the flexural strength. [000218] Table 5 below lists the samples used in this test including the dimensions of each of the samples.

[000219] Table 5

Composite material Sample Number of layers Width (mm) Thickness (mm)

Example 28 17 3 12.6 3.45

18 3 12.53 3.55

19 3 12.6 3.58

Example 27 20 2 12.8 2.30 21 2 12.75 2.34

22 2 12.7 2.38

23 2 12.7 2.31

Example 25 24 1 12.59 1.42

25 1 12.5 1.43

Reference 26 9 12.7 3.65

Example 30 27 9 12.78 3.70

28 9 12.88 3.65

Reference 29 6 13 2.10

Example 29 30 6 13 2.10

31 6 12.8 2.14

32 6 12.7 2.10

33 6 13.08 2.17

34 6 12.9 2.36

Reference 35 3 12.6 1.37

Example 26 36 3 12.8 1.34

[000220] For the samples having a thickness of less than 1.6 mm (samples of Example 25 and Reference Example 26), according to the standard, the support span cannot be modified and must be fixed at 25.4 mm. Due to the small span-to-depth ratio (around 18 for these samples), the modulus can be affected by the shear deflections during the test. Therefore, the results obtained for the bending modulus can be only used to point out the relative behaviour of the samples of Example 25 and Reference Example 26.

[000221] Figure 13 is a graph showing stress versus strain for the samples of Example 25 and Reference Example 26 during the three point loading test. As it is possible to see from the different trends of the curves, the samples of Example 25 show lower values of the flexural strength than the samples of Reference Example 26 (see also figure 14). However, samples of Example 25 allow a larger deformation of the composite when it is subjected to an axial load (see also figures 15 and 16) compared to the samples of Reference Example 26. This behaviour can be explained with the presence of the twists along the axial direction which increases the total flexibility of the samples of Example 25 making them more susceptible to bending than the samples of Reference Example 26. [000222] Figure 16 is a graph showing the flexural extension shown by samples of Example 25 and Reference Example 26 as load on the samples is increased.

[000223] Figure 17 is a graph showing the modulus of elasticity in bending of the samples of Example 27 and Reference Example 29. The higher pliability of the samples of Example 27 compared to the samples of Reference Example 29 is also reflected in the behaviour of the bending Modulus Eb.

[000224] Samples of Example 27 and Reference Example 29 were tested as described above in the three point bending test. The samples were first tested with a span of 130 mm (as suggested by the standard) and then further samples were tested with a span of 72 mm in order to induce tensile failure in the outer fibres of the sample along its lower face. The stress strain curve obtained for the three point bending test (span 72 mm) of the samples of Example 27 and Reference Example 29 is shown in fig. 18. As for the test performed on samples of Example 25 and Reference Example 26, the samples of Example 27 showed lower values of the flexural strength (average value of flexural strength for samples of Example 27 was 297 MPa) than the samples of

Reference Example 29 (average value of flexural strength of 715 MPa). However, the samples of Reference Example 29 present at the maximum stress a strain of 1.78% while the samples of Example 27 reach a strain of 3.73% at the maximum stress. The average elastic bending modulus of the samples of Example 27 was calculated to be 20.34 GPa, with that for the samples of Reference Example 29 being 43.80 GPa.

[000225] Samples of Example 28 and Reference Example 30 were tested as described above in the three point bending test. The samples were first tested with a span of 112 mm (as suggested by the standard). However, only samples of Reference Example 30 failed during this test, so further samples were then tested with a span of 72 mm in order to bring samples of both Example 28 and Reference Example 30 to breaking point. The stress strain curve obtained for the three point bending test (span 72 mm) of the samples of Example 28 and Reference Example 30 is shown in fig. 19. As for the previous tests, the samples of Example 28 showed lower values of the flexural strength (average value of flexural strength for samples of Example 28 was 325 MPa) than the samples of Reference Example 30 (average value of flexural strength of 629 MPa). The samples of Reference Example 30 present at the maximum stress a strain of 2.03% while the samples of Example 28 reach a strain of 2.92% at the maximum stress. The average elastic bending modulus of the samples of Example 28 was calculated to be 21.80 GPa, with that for the samples of Reference Example 30 being 38.30 GPa. [000226] It was observed that for each of the tests, although the samples of Examples 25, 27 and 28 showed a very large displacement in comparison with the samples of Reference Examples 26, 29 and 30, the final shape of the samples of the Examples of the present invention showed a smaller bending angle due to the very large elastic recovery (almost 65%) that happens once the load is removed from the mid-section of the sample. Moreover, the samples of Examples 25, 27 and 28 presented only the bottom part damaged keeping the first two layers almost intact, while the samples of Reference Examples 26, 29 and 30 presented catastrophic failures (samples split in two parts). [000227] Analysing the three point bending test results described above, it is possible to conclude that the twisting procedure adopted for the samples of Examples 25, 27 and 28, strongly affects the flexural behaviour of the composite laminates. In particular, the tested samples of Reference Examples 26, 29 and 30 show fragile fracture which is typical of carbon composite structures with cracks propagating through the thickness of the specimens breaking the fibres in the area under tensile stress, and in the worst case bringing the sample to catastrophic failure. On the other hand, the samples of Examples 25, 27 and 28 show a pseudoplastic behaviour similar to the one observed in metals and polymers. Indeed, the sample is able to accommodate large displacements by deforming its structure due to the twisted carbon fibres that act as a sort of spring. This behaviour is confirmed by the large flexural strain shown for all three thickness, and by a very large elastic recovery that happens once the load is removed from the mid-section of the samples of Examples 25, 27 and 28.

Testing of fibre fabric composite materials - Young's Modulus evaluation via vibrational behaviour of composite beams [000228] The elastic properties of the materials produced according to Example 25 and Reference Example 26 were evaluated by collecting vibration data from single cantilever samples subjected to an out-of-plane load F using a Laser displacement measuring system (MicroEpsilon). The displacement along the out-of-plane direction data were used to evaluate the natural frequency of the different samples from which it was then possible to calculate the Elastic Modulus along the sample's length knowing its geometry and density.

Since due to the twisted orientation of the fibres bundles the composite fabrics of the present invention, e.g. Example 25, is expected to show higher levels of in-plane isotropy than previous composite fabrics, several samples were cut at 50x5mm at different angles in order to evaluate the elastic properties of the fabrics at different orientations. The direction chosen were 0, 30, 45, 60 and 90° as illustrated in figure 20.

[000229] The results obtained for the Young's modulus of the samples of Reference Example 26 are shown in figure 21 and the results for the Young's modulus of the samples of Example 25 are shown in figure 22. Figure 21 shows that the elastic properties of the samples of Reference Example 26 are strongly dependent on the orientation in which the samples were cut, whereas the elastic properties of the samples of Example 25 show much less variation with respect to the orientation the samples were cut. Figure 23 shows that the composite material of the present invention shows a very high level of isotropy unlike the composite material of the reference examples (see figure 21).

[000230] It is important to underline that the twisted structure of samples of the present invention orients the fibres not only in the planar direction but also along the out-of- plane direction, having the fibres twisted in a fully 360° helix along the tow's length. This means that the isotropy of the material is not only in the planar direction such as in traditional quasi-isotropic laminates, but along all the three dimensions like in true homogeneous materials like metals, because of the plain weave pattern of the fabric, the traditional straight fibres concentrates all the strength given by the carbon material along the 0° and 90° directions, showing properties along the other planar directions which are a weaker combination of these two, while leaving the out-of-plane direction completely unreinforced (hence susceptible to cracks, delaminations and other interlaminar damage). In other words, by changing the orientation of the fibres in the tows that form the fabric from a straight aligned configuration to a three-dimensional twisted one (as the materials of the present invention) it is possible to modify how the strength of the fibrous reinforcement is distributed along all the three directions, balancing the elastic properties of the material.

Testing of fibre fabric composite materials - damping evaluation via vibrational behaviour of composite beams

[000231] In order to fully understand how the twisted material would behave when subjected to a load in the out-of-plane direction, experiments were conducted to evaluate the damping characteristics of several samples of material of Example 25 oriented at different angles (as shown in figure 20 and used to determine the elasticity as described above) and a comparison was made with a traditional straight laminate (Reference Example 26).

Damping ratio can be defined a dimensionless measure describing how oscillations in a system decay after a disturbance. The damping ratio is a parameter, denoted by ζ (zeta), which characterises the frequency response of a second order ordinary differential equation.

„ , x n-w

o = In

x n where x(n) is the amplitude of the vibration at the n th peak, and x(n-w) is the amplitude recorded for a peak w periods away.

Once the logarithmic factor δ was evaluated, it was possible to calculate the damping coefficient ζ by using the following equation:

[000232] Figure 24 shows the damping coefficient determined for samples of the material of Example 25 and Reference Example 26 at orientations of 0°, 30°, 45°, 60° and 90° (as shown in figure 21) which shows the effect given by the variation in the geometry of the fibrous reinforcement on the vibration dissipation. From figure 23 it is possible to observe that while the samples of Reference Example 26 follow a trend which is highly variable with the orientation of the sample, the samples of Example 25, due to the helical disposition of the fibres along the tow's length, presents a much more isotropic behaviour, confirming the results observed with the vibration tests for the Young's Modulus evaluation.

[000233] While the fibre ropes, fabrics, materials, methods and related aspects have been described with reference to certain examples, it will be appreciated that various modifications, changes, omissions, and substitutions can be made without departing from the spirit of the disclosure. It is intended, therefore, that the fibre ropes, fabrics, materials, methods and related aspects be limited only by the scope of the following claims. Unless otherwise stated, the features of any dependent claim can be combined with the features of any of the other dependent claims, and any other independent claim.




 
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