FLEXIBLE COMPOSITE

Abstract

The present invention relates to a flexible composite that can be set to become rigid or semi-rigid, the composite comprising: a first layer; a second layer opposing the first layer and separated from the first layer by a space; a fill material located in the space between the first and second layers, which is capable of setting to a rigid or semi-rigid solid on the addition of a liquid, gas or radiation; a plurality of elements extending substantially into the space from the first layer and/or the second layer and which may pass through the opposing layer or join with other elements present in the space from an opposing layer, thereby forming linking elements for joining the layers together; and wherein the unset fill material is provided in the space at a pressure such that tension is applied one or more of the linking elements and to cause the first and/or second layers to bulge outwards relative to the longitudinal length of said one or more linking elements under tension.

Claims

1. A flexible composite that can be set to become rigid or semi-rigid, the composite comprising: a first layer; a second layer opposing the first layer and separated from the first layer by a space; a fill material located in the space between the first and second layers, which is capable of setting to a rigid or semi-rigid solid on the addition of a liquid, gas or radiation; a plurality of elements extending substantially into the space from and connected to the first layer and/or the second layer and which may pass through the first layer and/or the second layer, and may connect together, thereby forming linking elements for joining the layers together; and wherein the unset fill material is provided in the space at a pressure such that tension is applied to one or more of the linking elements and to cause the first and/or second layers to bulge outwards between adjacent linking elements that are under tension.

2. The flexible composite according to claim 1, wherein the first layer comprises a non-woven fabric.

3. The flexible composite according to claim 2, wherein the non-woven fabric comprises fibres which are bonded by: needle punching, adhesives, heating, hydro-entanglement, stitch bonding, or ultrasonic welding.

4. The flexible composite according to claim 2 or claim 3, wherein the non-woven fabric comprises polypropylene fibres.

5. The flexible composite according to any one of claims 2 to 4, wherein the non-woven fabric comprises fibres with an average linear density of from 0.1-100 decitex, 0.2-100 decitex, 0.5-100 decitex, 1-100 decitex, 2-50 decitex, 3-30 decitex or a blend of fibres of different weights.

6. The flexible composite according to any one of claims 2 to 5, wherein the non-woven fabric comprises staple fibres with a length of from 10-200 mm, preferably 30-150 mm, or 40-100 mm.

7. The flexible composite according to any preceding claim, wherein the first layer is permeable to gases and liquid, but substantially impermeable to the fill material.

8. The flexible composite according to any preceding claim, wherein the first layer and/or the second layer further contain a reinforcement element comprising a woven, non-woven, continuous membrane or knitted fabric configured to improve tensile strength and/or increase stiffness of the first and/or second layers.

9. The flexible composite according to claim 8, wherein the reinforcement element comprises polyester or polypropylene.

10. The flexible composite according to any preceding claim where the ultimate tensile strength of the first and/or second layer may be represented by formula:
.sub.ft.sub.f4T.sub.r, where: .sub.f is the ultimate tensile stress in (N/m.sup.2) of the fill material when set; t.sub.f is the mean thickness of the set fill material (m); T.sub.r is the ultimate tensile strength (N/m) of the layer that is loaded in tension, per metre width.

11. The flexible composite according to any one of claims 8 to 10, wherein the first and/or second layer has a tensile strength of 0.5-200 kN per metre width, preferably 1 to 150 kN/m, or 1 to 100 kN/m.

12. The flexible composite according to any preceding claim, wherein the first and/or second layer comprises a rough keying fabric element on at least part of its innermost surface, thereby abutting the powder material in the space for the powder to adhere to when set.

13. The flexible composite according to claim 12, wherein the rough keying fabric comprises polypropylene fibres.

14. The flexible composite according to claim 12 or claim 13, wherein the keying fabric element abutting the powder material is configured to provide a bond between the keying fabric and the powder material with a peel resistance of from 0.5-10 kN/m when the powder material is set.

15. The flexible composite according to any one of claims 12 to 14 when dependent on any one of claims 8 to 11, wherein the keying fabric element is bonded to the reinforcement layer, and wherein the peel resistance of the bond between the keying fabric and the reinforcement layer is from 0.5-10 kN/m.

16. The flexible composite according to any preceding claim, wherein the second layer is substantially impervious to fluids.

17. The flexible composite according to claim 16 where the hydraulic conductivity of the second layer is in the range 10.sup.310.sup.15 ms.sup.1 or 10.sup.610.sup.14 ms.sup.1 or 10.sup.710.sup.12 ms.sup.1.

18. The flexible composite according to claim 16 or claim 17, wherein the second layer comprises a separate continuous membrane configured to be substantially impervious to fluids, said continuous membrane comprising polypropylene, high and medium and low density polyethylene, PVC, rubber or polyurethane.

19. The flexible composite according to claim 18, wherein the second layer comprises a non-woven fabric element on its outermost surface facing away from the fill material to form a protection element.

20. The flexible composite according to claim 19, wherein the non-woven fabric element comprises fibres which are bonded by: needle punching, adhesives, heating and pressure, hydroentanglement, stich bonding, or ultrasonic welding.

21. The flexible composite according to claim 19 or claim 20, wherein the non-woven fabric element comprises polyester and/or polypropylene.

22. The flexible composite according to any preceding claim, wherein the second layer comprises a non-slip element on at least part of its outermost surface which faces away from the fill material to improve the grip between the flexible composite and a surface on which it is laid.

23. The flexible composite according to claim 22 where the non-slip element comprises natural rubber, synthetic rubber, polypropylene, polyester, PVC, LDPE, LLDPE, or HDPE and/or a degree of texture.

24. The flexible composite according to any preceding claim, wherein the linking elements extend between the first and second layer, thereby joining them, and are spaced apart in a regular or irregular arrangement along the longitudinal and/or transverse axis of the flexible composite.

25. The flexible composite according to any preceding claim, wherein the linking elements are arranged in one of the following patterns: regular or irregular triangles, square, rectangular, hexagonal, any other polygonal shape, tricot, substantially randomly distributed, or any combination thereof.

26. The flexible composite according to any preceding claim, wherein each linking element comprises a plurality of sub-elements which extend across the space and through one or both of the layers in a discrete column capable of supporting a tensile load.

27. The flexible composite according to any one of claims 24 to 26, wherein the linking elements are spaced apart from each other at a distance of from 0.1-100 mm, 0.1-50 mm, preferably from 0.5-30 mm, more preferably from 1-20 mm, or from most preferably 1-12 mm.

28. The flexible composite according to any one of claims 24 to 27, wherein the linking elements extend between the first layer and/or the second layer at a net angle substantially perpendicular to the mid-plane between the first and second layers.

29. The flexible composite according to any preceding claim, wherein the linking elements are positioned in the space by one or more of needle punching, stitch bonding, hydro-entanglement, and engaging with pre-formed hooks.

30. The flexible composite according to any preceding claim, wherein the linking elements extending across the space from the first layer and/or second layer extend through the opposing layer, thereby joining the layers together.

31. The flexible composite according to claim 30, wherein the linking elements extending through the first and/or second layer are adapted to be secured to an outer most side of the layer it has extended through.

32. The flexible composite according to claim 31 when dependent on claims 18 to 21, wherein the linking elements do not extend through the continuous membrane.

33. The flexible composite according to claim 31 or claim 32, wherein the linking elements are secured by one or more of mechanical entanglement, adhesive, fusing by heating or by bonding to a polymer layer by chemical or mechanical means.

34. The flexible composite according to any previous claims, wherein the peel strength between the first and second layers of the unset flexible composite is from 0.1 kN/m to 20 kN/m, and preferably 0.3 kN/m to 3 kN/m.

35. The flexible composite according to any one of claims 24 to 34, wherein once the linking elements have extended through said first layer and/or second layer they change direction to be substantially parallel to said first layer and/or second layer.

36. The flexible composite according to any preceding claim, wherein the linking elements are fibres

37. The flexible composite according to any preceding claim, wherein the linking elements originate from the first layer and/or the second layer.

38. The flexible composite according to any one of claims 29 to 37, wherein the linking elements extending substantially across the space from the first layer and/or the second layer, pass through the opposite layer and extend back into the space.

39. The flexible composite according to claim 38, wherein the linking elements extending substantially back into the space are configured to join with other elements located in the space.

40. The flexible composite according to claim 39, wherein the elements extending substantially back into the space join with the other elements by way of entanglement.

41. The flexible composite according to claim 38, wherein the elements extending substantially back into the space are configured to join with the layer from which the fibres originated.

42. The flexible composite in accordance with any preceding claim, wherein the fill material is selected from one or more of a powder, a paste, or a foamable composition.

43. The flexible composite according to any one of claims 1 to 42, wherein the fill material comprises one or more of a cement-aggregate mix, high alumina cement, lime-aggregate mix and Portland cement.

44. The flexible composite according to any preceding claim, wherein the fill material includes a filler material.

45. The flexible composite according to any preceding claim, wherein the fill material includes a reaction modifier.

46. The flexible composite according to any preceding claim, wherein the fill material has a tensile strength when set of from 0.1-20 MPa, preferably 0.1-10 MPa, more preferably 0.5-5 MPa.

47. The flexible composite according to any preceding claim, wherein the fill material has a compressive strength when set of from 1-500 MPa, preferably 5-200 MPa, more preferably 15-100 MPa.

48. The flexible composite in accordance with any preceding claim, further comprising a second fill material located in the space between the first and second layers, and wherein said second fill material is separated from the first fill material by way of a separation layer located in the space between the first and second layers.

49. The flexible composite in accordance with claim 48, wherein the second fill material is selected from one or more of a powder, a paste, or a foamable composition.

50. The flexible composite in accordance with claim 48 or claim 49, wherein the second fill material comprises bentonite clay or a super absorbent polymer.

51. The flexible composite according to any one of claims 48 to 50, wherein the separation layer is a paper or a woven, non-woven, knitted fabric or extruded layer.

52. The flexible composite according to any one of claims 48 to 51, wherein the separation layer comprises non-woven polypropylene.

53. The flexible composite according to any preceding claim, wherein the layers of the flexible composite are bonded together with an adhesive, preferably the adhesive is a hot melt adhesive.

54. The flexible composite according to claim 53, wherein the adhesive comprises a polypropylene co-polymer adhered to or as part of the reinforcement layer.

55. The flexible composite according to any one of claims 53 to 54, wherein the adhesive provides a shear strength between the layers substantially similar to the ultimate tensile strength of the first layer and/or the second layer.

56. The flexible composite according to any preceding claim, wherein one or more of the materials in the first layer and/or the second layer are water soluble, rottable, UV degradable, hydrophilic, and hydrophobic.

57. The flexible composite according to any preceding claim, wherein one or more of the materials in the first layer and/or the second layer are a biocide or a biological growth promoter.

58. The flexible composite according to any preceding claim where either the fill, the first layer or the second layer contain electrically conductive fibres, thereby enabling detection of damage or strain to the flexible composite, and the location thereof.

59. The flexible composite according to any preceding claim, further comprising a thermal insulation layer on the outer most side of the first layer or the outer most side of the second layer allowing that additional layers may be applied outside the thermal insulation layer.

60. The flexible composite according to any of the previous claims, further comprising a ductile layer that has sufficient out of plane stiffness that it can be bent (plastically deformed) to form the unset flexible composite into a three dimensional shape that can support it self-weight before the material is set.

61. A flexible composite as described herein with reference to the accompanying drawings.

Description

[0102] The present invention may be carried out in various ways and some preferred embodiments of a flexible composite in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which:

[0103] FIGS. 1 to 9show cross-sectional views through preferred embodiments of a flexible composite;

[0104] FIGS. 10 and 11shows the flexural stiffness of two flexible composites of the present invention;

[0105] FIG. 12shows the peel strength between a layer of a flexible composite of the present invention and a set powder material in the space of said flexible composite;

[0106] FIG. 13shows the peel strength between two elements which form a second layer of a flexible composite of the present invention

[0107] FIG. 14shows the peel strength between first and second layers of an unset flexible composite of the present invention; and

[0108] FIG. 15shows the forces exerted on a flexible composite during a three-point bend test.

DETAILED DESCRIPTION

[0109] A first example of a flexible composite in accordance with the present invention is shown in FIG. 1 generally at item 100 and its accompanying exploded view which shows the layers that make up composite 100. Flexible composite 100 comprises a first layer (a), a second layer (c), and a space (b) between the first and second layers. The space (b) comprises a fill material 3 and linking elements 2.

[0110] The structure of the flexible composite 100 is achieved by impregnating the fill material 3 under positive differential pressure in between the first layer (a) and second layer (c) whilst positioning the linking elements 2 in the space (b) to extend between said layers using needle punching, as previously described.

[0111] The first layer (a) is a fibre donating layer 1 made of a needle punched polypropylene non-woven fabric which is firstly capable of containing the fill material 3 in the space (b) between the first and second layers, and secondly is selectively permeable to certain fluids e.g. permeable to liquids and gases but not substantially to the fill material 3.

[0112] The fibres 2 are polypropylene fibres that have been extended out from the non-woven fabric of first layer 1, and extend through the space (b) with a net angle of approximately 90 degrees to layers (a) and (c) so as to be substantially perpendicular to the longitudinal axis of said layers. The needling technique uses barbed needles to pick up fibres from the non-woven polypropylene of layer (a) and carry/extend them through the space (b) and substantially over to the second layer (c).

[0113] The fill material 3, when unset, is provided in the space (b) at a pressure such that tension is applied to the fibres. The pressure of the fill material, and a lack of longitudinal stretch of the fibres under tension, causes the first and second layers to bulge outwards relative to the longitudinal length of the fibres under tension. In other words, the first and second layers outwardly extend beyond the fibres 2 in the direction of the net longitudinal axis of the fibres 2.

[0114] The amount/extent of which the first layer (a) and/or the second layer (c) bulge out due to the pressurised fill material depends on the material properties of the fibres and the first and second layers. For example, the stiffness of the first and/or second layers may be increased to reduce the amount of bulging, or even increased on one of the layers so that the bulging is prevented altogether. The material properties of the first layer (a) and the second layer (c) may be varied so as to obtain bulges of different sizes when the fill material is present in the space under pressure.

[0115] Therefore, flexible composite 100 shows a cross section through the three dimensional microstructures created by filling the fill material under positive differential pressure, deforming the first and second layer, with the linked fibres forming the minima of the shape thus formed.

[0116] Once the fibres 2 have passed through and exited the second layer (c) due to the needle punching, their primary direction changes from being substantially perpendicular to the longitudinal axis of the first layer (a) and the second layer (c) to being substantially parallel to said longitudinal axis of layers (a) and (c). The parts of the fibres that have changed direction are configured to substantially conform to the bulging surface of the second layer (c). After this change of direction, the fibres are bonded to the second layer (c) using the adhesive layer 5, thereby providing a mechanical join between the first layer (a) and second layer (c).

[0117] The fill material may be any material that is capable of setting to a rigid or semi-rigid solid upon the addition of a liquid, when exposed to UV radiation or a gas such as air, e.g. any suitable paste, powder or foamable composition. Cement may be used together with fillers and other additives such as reaction modifiers.

[0118] The second layer (c) consists of reinforcement element 4 made of woven polypropylene tape. The woven polypropylene tape is coated on the outer face by a film of adhesive such as hot melt polymer 5. The hot melt adhesive 5 allows the attachment of the fibres 2 once they are pushed through the second layer (c) and their direction has been changed to substantially conform to the shape of the second layer (c).

[0119] The woven polypropylene tape 4 is substantially impervious to fluids once the holes made by the barbed needles are resealed by the adhesive layer.

[0120] The fibres from the donating layer 1 protruding through the reinforcement element 4 may alternatively be shrivelled using a heat source such as a hot air or radiative source this has the effect of thickening the fibre on the outer face of the reinforcement which inhibits it from being pulled back through the reinforcement layer this can be used in addition or as an alternative to the adhesive layer 5 in this case the reinforcement layer 4 may be more permeable but will still serve to substantially contain the powder fill material 3.

[0121] Liquids such as water can penetrate into the flexible fabric 100 via the first layer (a); hydration of the fill material 3, for example cement, is aided by the fibres 2, which are capable of wicking water into the interior of the flexible fabric 100. The second layer (c) together with the fibres 2, provide reinforcement to the fill material when set, and prevent crack propagation.

[0122] The reinforcement element 4 may optionally be provided with a further protective element 7 on the outer surface, thereby protecting the underside of the flexible composite from becoming damaged during installation and use. Additionally, the inner surface of the reinforcement element 4 may be provided with a keying element 8 to provide a surface for the fill material 3 to key into. FIG. 2 shows a flexible composite in accordance with the present invention generally at item 200, which additionally comprises such keying and protective elements at items 8 and 7 respectively. The keying element is a spunlace needle punched or thermally bonded polypropylene non-woven fabric. The protective element is a needle punched non-woven polypropylene fabric. The keying and protective elements are not only limited to being made from these materials, and may alternatively be any other suitable material of the type hereinbefore described in relation to the keying and protective elements.

[0123] The protective element 7 may additionally act to have a non-slip capability. This would improve the grip of the flexible composite when it is laid on a surface. Alternatively, the non-slip element may replace the protection element 7 altogether, or may be applied on the outer face of the protection element (not shown in the diagram). The non-slip element may be made from any suitable material, for example the non-slip element may be made from any of the materials hereinbefore described in relation to the non-slip element.

[0124] The keying element 8 and protective element 7 adhere to a low-melt polymer coating on either face of the woven polypropylene of the reinforcement element 4, shown as 5 and 9 respectively.

[0125] The first layer (a) may optionally be provided with a reinforcement element 10 on the inner surface of the first layer 1 (the surface of layer (1) that is closer to the fill material) which, in contrast to element 4, must be fluid permeable. A flexible composite with a reinforcement element 10 on the inner surface of the first layer (1) is shown generally at item 300 of FIG. 3. The other layers and elements 1 to 9 are the same as those described in relation to the flexible composite 200 shown in FIG. 2. The preferred material for this reinforcement element 10 would be an open weave polypropylene tape. This additional reinforcement element may be provided with an adhesive layer 11, which may be a hot melt polymer of the type hereinbefore described. This gives the flexible composite with increased bending strength (once set) in both directions over an unreinforced version i.e. the amount of load the flexible composite can take from the first layer (a) side before failure and from the second layer (c) side before failure, is greater than if unreinforced.

[0126] FIG. 4 shows another example of a flexible composite in accordance with the present invention generally at item 400. In addition to having a single fibre donor element 1 in the first layer (a) as in FIGS. 1 to 3, flexible composite 400 additionally comprises a second fibre donor element 12 in the second layer (c). The first layer (a) and space (b) of the flexible composite 400 are substantially the same as the first layer (a) and space (b) of flexible composites 100 and 200, apart from that some of the fibres 2 within the space (b) have additionally extended from the second fibre donor element 12, as opposed to all of the fibres 2 extending from the fibre donor element 1 in accordance with flexible composites 100 and 200.

[0127] The fibres 2 of flexible composite 400 are polypropylene fibres that have extended from donor element 1 and donor element 12, and extend with a net angle of 90 degrees to layers (a) and (c) through the space (b) and towards the opposing layer. The fibres 2 are established using a needle punch technique that is similar to the technique hereinbefore described in connection with flexible composite 100 and flexible composite 200. The needle punching technique differs from the aforementioned needling technique in that barbed needles are used to pick up fibres 2 from the non-woven polypropylene of the second fibre donor element 12 (in addition to picking up fibres from donor element 1 as discussed above), and carry them through the space (b) and to the first layer (a). Thus, needles are striking both down through layer 1 and in the opposite direction through layer 12. These strikes may be sequential or simultaneous.

[0128] In some applications, it may be useful to have two distinct layers of fill material. For example, if a flexible composite as disclosed herein is to be used to form a water channel or to be laid on a river bed, it may be desirable to have a flexible composite with a layer of settable material which will protect a lower material which may or may not be settable, from being worn or eroded away.

[0129] Flexible composite 500 in FIG. 5 is provided with an additional second fill material 14 which is located in the space (b) and separated from the first fill material 3 by way of a separation layer 13, thereby defining a first fill material layer and a second fill material layer. The first fill material layer must be a settable fill, as described previously. In contrast, the second fill material 14 may be one of a variety of potential materials such as the materials hereinbefore described in relation to the second fill material. The second fill material may be a settable fill material that is similar to the first fill material, but may also be non-settable material, for example a fluid swellable substance, such as bentonite clay.

[0130] The separation element may be made from non-woven polypropylene, which is permeable to liquids such as water. As such, when a liquid (e.g. water) is applied to the composite, the separation element allows the water to seep through the first fill material layer to the second fill material layer, thereby allowing both fill materials to be hydrated but preventing substantial mixing of the two fill materials when dry or wet.

[0131] The separation element is not limited to being made from non-woven polypropylene, and made alternatively be any other suitable material fabric which can separate the two fill materials and is permeable to liquids such as water. The separation element may be any of the materials hereinbefore described in relation to the separation element. The separation element may also include a reinforcement element (not shown in diagrams) as previously described.

[0132] Any of the flexible composites described herein may be provided with one or more conductive fibres (e.g. conductive carbon fibres, metallic conductive wires such as steel, aluminium or copper or optical fibres, graphene-coated fibres or sheets). Such fibres are inserted into the space (b) alongside the fill material 3 (or fill materials 3 and 14), as shown in flexible composite 600 in FIG. 6. Providing a flexible composite comprising conductive fibres 15 in this way can enable a user to use electrical conductive resistance measurements to determine if, when and where the flexible composite is damaged or exposed to liquid or experience heavy strain, so that repairs can be more easily made or the installation monitored for other purposes. These fibres could alternatively be an integral element of any layer 1-15 shown in FIGS. 1-6.

[0133] The example embodiments of the flexible composites described above (Flexible composites 100, 200, 300, 400, 500 and 600) all comprise an element of non-woven material which acts as a fibre donor for the fibres 2, which are needled across the inner space (b) using the needle punching technique as discussed above. This needling technique enables the first layer (a) to be mechanically joined to the second layer (c). The flexible composite of the present invention is not limited to a flexible composite that has been produced by needle punching. An alternative example of a flexible composite in accordance with the present invention is shown in FIG. 7, generally at item 700. Flexible composite 700 has fibres 2 which have been inserted using a stitch bonding technique as previously described. These fibres 2 have been inserted from an external yarn (in contrast to originating from the first and/or second layer as shown in the other example embodiments) through the first layer, and stitched through the second layer thereby mechanically linking them by way of a stitch. The first layer (a) of flexible composite 700 comprises a needle-punched non-woven polypropylene 1 of the type previously mentioned. The first layer (a) of flexible composite 700 is not limited to being such a material, and may alternatively be any other material of the type hereinbefore described in relation to the first layer (a). In addition, the material of layer (a) is not limited to being capable of donating fibres, and therefore may be solely a woven or knitted material or spunlace or thermally consolidated or extruded. The second layer (c) is a woven polypropylene tape 4 of the type previously discussed. The second layer (c) may alternatively be a nonwoven material 18, and preferably a 200 g/m.sup.2 needlepunched polypropylene (PP) nonwoven. An option for this embodiment (not shown in the figures) is to add a single additional layer to act as both reinforcement and containment elements, for example a continuous LLDPE geomembrane thermally laminated to the underside of the product.

[0134] The flexible composite in accordance with the present invention may be provided with an insulation element on the outermost surface of the first layer (a) and/or the second layer (c). The insulation element may take the form of a new layer (d). An example of a flexible composite with an insulation layer (d) is shown in the form of flexible composite 800 in FIG. 8. Insulation layer (d) may be made from any suitable material which is able to provide an insulative effect to the flexible composite. The insulation layer (d) may comprise any of the aforementioned materials discussed hereinbefore in relation to the insulation element or insulation layer. The insulation layer may be composed of a solid foam cut into triangular or otherwise tessellating blocks to allow the composite to be rolled up.

[0135] The surfaces of the flexible composites (the first layer (a) and/or the second layer (c)) may be bonded to one or more further layers comprising any number of coatings which act to improve the mechanical properties of the flexible composite (not shown in the Figures). For example, the first layer (a) and/or second layer (c) may comprise a coating capable of showing areas of the wear on said layer thereby helping a user of said flexible composite to identify worn areas of the composite; providing ultraviolet (UV) radiation resistance to prevent UV damage to the composite; providing an increased friction coefficient to allow vehicles or people to travel and walk respectively on said flexible composite without slipping; providing a biological growth promoting surface to promote the growth of vegetation on the surface of the flexible composite or a biocidal component to prevent the growth of algae, mosses or other plants; improving fire resistance of the flexible composite; making the material hydrophobic or hydrophilic; and/or improving the flexible composite's chemical resistance.

[0136] The flexible composite in accordance with the present invention may be provided with a water impervious layer (a water proof layer) on the outermost surface of the second layer (c). An example of a flexible composite with a water impervious layer bonded onto the outermost surface of the second layer (c) is shown in FIG. 9, generally at item 900. The water impervious layer 17 may be made from any suitable material which is impervious to water, and is preferably a polymeric material, and most preferably polypropylene, polyester, PVC, or polyurethane. Polymeric materials may be liquified and cast onto the flexible composite using a slot extruder. The water impervious properties of layer 17 may be combined with any other outermost layer for the second layer described herein, for example the water impervious layer may be combined to additionally have inherent non-slip or insulative properties.

[0137] An example sequence of manufacture of a flexible composite as described herein is set out below.

[0138] Firstly, the first layer (consisting of a needle punched polypropylene non-woven fabric) and the second layer (consisting of a woven polypropylene tape, coated with low melt on its outer face and with a needle punched polypropylene nonwoven bonded to its inner face) are drawn into a needle loom. For example, a loom which can produce material up to 10 m in width. The loom has a series of long tubes running in the machine direction (MD) (i.e. in the production direction of the flexible composite) fixed between a loom bed and stripper plates. The tubes are positioned between the stripper plates and the loom bed so as to leave a gap either side of the tubes. The bed and stripper plates are separated by a gap of between 3 and 100 mm. The first layer is drawn through the loom between the tubes and the stripper plate. The second layer is drawn through the loom between the tubes and the bed plate, with the tubes forming a sandwich between the two layers. The tubes have an outer diameter between 3 and 25 mm and are aligned at a spacing in the cross direction (the transverse direction which is 90 degrees from the MD) of between 4 and 50 mm, the tubes may be of a non-circular cross section and/or may be stacked. The thickness of the final flexible composite is dependent on both the size of the gap between the bed and stripper plates, and on the diameter of the tubes. The thickness of the flexible composite (once filled) is between 3 and 50 mm.

[0139] Secondly, the needles of the needle loom are aligned such as to strike between the tubes. The stripper plate and loom bed comprise holes or slits, which are aligned so as to receive the needles and allow them to pass through during the strike action. Needles striking repeatedly in this manner push fibres from the first layer, across the gap between the tubes and through the second layer, with the ends of the fibres projecting from the outer face of the second layer between 0.1 and 30 mm. The spacing in the machine direction of the linking elements thus formed is between 0.5 and 20 mm. The spacing in the transverse direction is fixed as a multiple of the spacing of the tubes, which may be evenly or irregularity spaced, with even or irregular gaps between them. As the material is drawn through the needle loom, at a line speed of between 0.1 and 50 m/min it slides over the fixed tubes. The needles can be set to strike at any angle so long as the needles do not strike the tubes.

[0140] Thirdly, at a location between the needle loom and the downstream end of the tubes, a heater (hot air, conductive, radiative, high frequency etc.) and a pressure roller act upon the outer face of the second layer to activate the low melt layer and glue down the ends of the linking fibres protruding from the outer face of the second layer. Alternatively, or additionally, the above heating method may be used to shrivel or bond the protruding fibre ends to prevent pull-out.

[0141] Fourthly, a protective element (consisting of a needle punched polypropylene nonwoven) may be added to the outer face of the second layer. It is preferable to introduce this at the same position in the line as the heater so that the same low melt adhesive which glues down the linking fibre tufts also adheres to the protective layer. Other layers described herein in relation to the various exemplary flexible composites may be introduced in a similar manner to the first layer and/or second layer, such as non-slip or fluid impervious layers. If, for example, a water impervious layer 17 is being added to a flexible cloth as disclosed herein, it may be bonded onto the second layer on the outside of the reinforcement element (or protective element) after needling, in the form of a continuous membrane. Optionally, a protective layer may be pre-bonded onto the outer face of the water impervious layer (not shown on FIG. 11).

[0142] Fifthly, the tubes extend from the needle loom a distance in the machine direction from between 0.1 m and 20 m. These tubes are connected at the upstream end to a pressure vessel containing pressurised settable powder fluidized with compressed air, with a particle size small enough to pass through the tubes. This settable powder is blown down the tubes and exits into the gap between the first and second layers. The settable powder is under a positive differential pressure when it exits the pressure vessel of between 0.1 and 50 bar, and is compacted as it enters the gap between the first and second layers. One of these layers acts as a filter to allow the air to leave the material. Stacked tubes (with a separation element introduced between them) may be used to introduce a second layer of a non-settable powder as described previously.

[0143] Optionally, the edges of the flexible composite are sealed to prevent the fill material from escaping. The edges of the flexible composite may be sealed before introduction or after introduction of the fill material, but preferably before introduction of the fill material. The edges of the flexible composite may be sealed by way of elastic yarn, stitching, ultrasonic bonding, thermal bonding, needle punching, or adhesive.

[0144] Lastly and optionally, the filled flexible composite is rolled up after the end of the tubes.

[0145] Optionally, if a reinforcement mesh is to be added to the flexible composite in manufacture it may be necessary to index the spacing of the needles and the rate at which the mesh is introduced into the loom from the spacing of the mesh. This is to ensure that the needles strike the holes in the mesh rather than the mesh itself which may damage the needles and/or the mesh.

[0146] The two primary layers (the first layer (a) and the second layer (c)) of the flexible composite produced by the manufacturing method set out above are linked by fibres originating from one of the primary layers using a needle punching machine (a needle loom). However, as mentioned herein, these linking fibres could originate from elsewhere, such as a yarn introduced into a stitch bonding machine. The manufacturing sequence above would be identical in the latter scenario, with the exception that the first and second layers would be drawn into a stitch bonding machine rather than a needling machine. The width of the flexible composite cloth, thickness, line speed, linking fibre spacing, etc. would remain unchanged. The key difference is that the reciprocating needles would be carrying yarn from an external reel between the two layers thereby joining them, rather than barbed needles picking up fibres from one of the layers to create the linking fibres. Alternatively, the material may be loaded by needling through the bulk powder under hydrostatic pressure.

Examples

Flexural Stiffness

[0147] FIGS. 10 and 11 show plots of three-point bend tests carried out on two set flexible composites A and B respectively in accordance with the present invention and based upon the standard test set out in BS EN 196-1:2005. FIGS. 10 and 11 show flexural strength in MPa vs central displacement in mm. Plot 17 is of a set sample of the flexible composite 200 described above and shown in FIG. 2.

[0148] The samples tested used a needle punching process to position the linking elements which were composed of donated fibres from the top surface. The samples had a length of 140 mm in the machine direction (MD), a width of 40 mm in the transverse direction (TD). The thickness of the set fill for composites A and B were 12 and 14 mm at the minimum points respectively, and 13.5 and 15 mm at the maximum points respectively (at the point of the bulges).

[0149] Supports for the three-point bend were at 100 mm centres and the loading bar was applied centrally. The sample was tested with the long dimension being in the MD with the first crack propagating in the TD.

[0150] Composite A had the following composition: Fibre donor/wear face: 340 g/m.sup.2 PP needle punched non-woven with 17 decitex staple fibres; Keying element: 120 g/m.sup.2 PP needle punched non-woven 7 decitex staple fibres; Reinforcement element: PP woven tape, 80 g/m.sup.2, 20 kN/m UTS; Protective Element: 120 g/m.sup.2 PP needle punched non-woven with 7 decitex staple fibres; Linking fibres arranged on a regular square pattern of 1.5 mm (MD)12 mm (TD), produced by needle punching the fibre donor face with 32 gauge needles; Settable fill: High alumina cement filled at 4 bar differential pressure; Sample set in excess water and left at standard temperature and pressure (STP) for 24 hours and tested on the 24.sup.th hour after water was first added.

[0151] Composite B had the following composition: Fibre donor/wear face: 200 g/m.sup.2 PP needle punched non-woven with 6 decitex staple fibres, UTS 12 kN/m; Keying element: 200 g/m.sup.2 PP needle punched non-woven 6 decitex staple fibres; Reinforcement/impervious element: 1 mm LLDPE geomembrane, 900 g/m.sup.2, 15 kN/m UTS; Linking fibres arranged on a regular square pattern of 4.5 mm (MD)12 mm (TD), produced by needle punching the fibre donor face with 30 gauge needles; Settable fill: 100% CEM 1/52.5N ordinary Portland cement filled at 3 bar differential pressure; Sample set in excess water and left at standard temperature and pressure (STP) for 7 days and tested on the 7th day after water was first added.

[0152] The sample of Composite A produced a first central crack in the cement at approximately 0.5 mm central displacement of the loading bar. Subsequent cracks approximately 5-20 mm from the centre of the samples appeared at approximately 2.5, 4, 6, 8 and 16 mm central displacement. The woven tape reinforcement element started to fail in the centre of the sample by the snapping of component tapes at approximately 23 mm central displacement. No further cracks in the cement occurred after this point. The tape progressively failed until the sample could bear no central load, at approximately 30 mm central displacement (off the scale of FIG. 9).

[0153] The sample of Composite B produced a first central crack in the cement at approximately 0.5 mm central displacement of the loading bar at a flexural strength of 4.8 MPa. Subsequent cracks approximately 5-20 mm from the centre of the samples appeared at approximately 2, 2.8, 4.5, 6.5, 8, 9, 12.3 and 22 mm central displacement. The second layer reinforced by the 1 mm LLDPE geomembrane started to fail in the centre of the sample at approximately 25 mm central displacement. No further cracks in the cement occurred after this point. The geomembrane underwent a large extension before final failure at approximately 35 mm central displacement (off the scale of FIG. 10).

[0154] The first crack of the set fill was followed by a progressive series of cracks of the set fill at a flexural load higher than that of the first crack and finally a failure of the reinforcement element in the second layer is indicative of the failure mode of the set flexible composite described herein.

[0155] FIGS. 12, 13 and 14 show three peel strength tests of Composite B described herein.

[0156] FIG. 12 shows the peel strength between the second layer and the cement fill of Composite B in its set state. The data was obtained using the method described in BS EN 13426-2:2005.

[0157] The results shown in FIG. 12 show an initial period of loading the sample from 0 to 20 mm displacement followed by 180 mm of extension at a load of between 2.5 and 4.3 kN per m width. A peel strength of such a range is more than sufficient to produce the flexural properties detailed in FIG. 11 without delamination.

[0158] FIG. 13 shows the peel strength between the 1 mm LLDPE geomembrane (acting as both the reinforcement and the containment layer) and the 200 g/m.sup.2 keying layer, which together form the second layer. The peel strength data was obtained using the method described in BS EN 13426-2:2005. The test was performed on the unset material.

[0159] The results shown in FIG. 13 show an initial period of loading the sample from 0 to 35 mm displacement followed by 165 mm of extension at a load of between 1.9 and 2.7 kN per m width. A peel strength of such a range is more than sufficient to produce the flexural properties detailed in FIG. 11 without delamination.

[0160] FIG. 14 shows the peel strength between the first and second layers of Composite B in its unset state. The peel strength data was obtained using the method described in BS EN 13426-2:2005.

[0161] The results shown in FIG. 14 show an initial period of loading the sample from 0 to 30 mm displacement followed by 170 mm of extension at a load of between 0.42 and 0.65 kN per m width. This peel strength is indicative of the tensile strength of the linking fibres, and of how well they are attached to the first and second layers. A peel strength of such a range is more than sufficient to prevent the delamination of the first and second layers in the unset state during manipulation and installation, and it has been found that such a range is also sufficient to contain the powdered fill during pressurised delivery of said powdered fill in manufacture of the flexible composite.