Stitched unidirectional or multi-axial reinforcement and a method of producing the same

1. A stitched unidirectional or multi-axial reinforcement for the manufacture of fiber reinforced composites by one of resin transfer molding process and vacuum infusion molding process, the stitched unidirectional or multi-axial reinforcement comprising:

at least one layer of continuous unidirectional rovings arranged in the reinforcement, and

a resin flow facilitator which, when wetting-out a stack of reinforcements with resin, facilitates a flow of resin in a direction transverse to a direction of the unidirectional rovings,

wherein the resin flow facilitator includes a single monofilament or a bundle of monofilaments bonded to one another having, under compression, a diameter or a thickness of 70 μm to 300 μm, the thickness is measured in a direction perpendicular to a plane of the at least one layer, the single monofilament or the bundle of monofilaments being arranged transverse to the unidirectional rovings, and the single monofilament or the bundle of monofilaments extending from one edge of the stitched unidirectional or multi-axial reinforcement to an opposite edge of the reinforcement, the at least one layer being bonded by stitching to the single monofilament or the bundle of monofilaments,

wherein the single monofilament or the bundle of monofilaments while in position with the unidirectional rovings form at least one flow passage in the reinforcement extending from the one edge to the opposite edge of the reinforcement.

2. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 , wherein the single monofilament or the bundle of monofilaments are arranged at right angles to the direction of the unidirectional rovings or their direction deviates at most 45 degrees therefrom.

3. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 , wherein the reinforcement is formed of two or more layers of roving s and the single monofilament or the bundle of monofilaments are arranged between at least two layers of rovings, or the single monofilament or the bundle of monofilaments are arranged only on a top and/or bottom surfaces of the unidirectional or multi-axial reinforcement.

4. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 , wherein the single monofilament or the bundle of monofilaments are arranged on at least one of a top surface and a bottom surface of the unidirectional or multi-axial reinforcement.

5. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 , wherein the single monofilament or the bundle of monofilaments are arranged at a spacing of 2 mm to 50 mm on the unidirectional or multi-axial reinforcement.

6. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 wherein the single monofilament or the bundle of monofilaments has a diameter of 100 μm to 200 μm.

7. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 , wherein each stitch has a length, and a distance or spacing between adjacent or neighboring single monofilament or the bundle of monofilaments is longer than the stitch length.

8. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 , wherein the single monofilament or the bundle of monofilaments have an elongation at break greater than an elongation at break of a matrix surrounding the layer and the single monofilament or the bundle of monofilaments.

9. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 wherein the rovings are fibers formed of at least one of glass, carbon, aramid, basalt, flax, hemp, jute, and linen.

10. The stitched unidirectional or multi-axial reinforcement as recited claim 1 , wherein the single monofilament or the bundle of monofilaments have, under compression, an aspect ratio of less than or equal to two.

11. The stitched unidirectional or multi-axial reinforcement as recited in claim 1 wherein the single monofilament or the bundle of monofilaments are made of at least one of polyamide (nylon), polyethylene terephthalate, polypropylene, polybutylene terephthalate, co-polyamide and copolyester (co-PET).

12. A preform comprising at least two stitched reinforcements as in claim 1 .

13. A laminate comprising one or more stitched reinforcements as in claim 1 .

14. A stitched unidirectional or multi-axial reinforcement comprising:

layers of continuous, unidirectional rovings aligned with a length direction of the reinforcement, and

a single monofilament or a bundle of monofilaments bonded together having, under compression, a diameter or a thickness of 70 μm to 300 μm, the thickness is measured in a direction perpendicular to a plane of the layers, the single monofilament or the bundle of monofilaments is transverse to the unidirectional rovings, and the single monofilament or the bundle of monofilaments extend from one edge of the reinforcement to an opposite edge of the reinforcement, wherein the layers are stitched to the single monofilament or the bundle of monofilaments, and

flow passages formed at a side of the single monofilament or the bundle of monofilaments and located between the layers of rovings, wherein the flow passages extend from the one edge to the opposite edge of the reinforcement.

15. The stitched unidirectional or multi-axial reinforcement of claim 14 wherein the reinforcement has a length greater than a width, wherein the width spans the one edge to the opposite edge.

16. The stitched unidirectional or multi-axial reinforcement of claim 14 , wherein the single monofilament or the bundle of monofilaments is at an angle in a range of 45 degrees to 135 degrees to the length direction.

17. The stitched unidirectional or multi-axial reinforcement of claim 14 wherein the single monofilament or the bundle of monofilaments is repeated at intervals along the length of the reinforcement.

18. The stitched unidirectional or multi-axial reinforcement of claim 17 wherein the intervals are in a range of 2 mm to 50 mm.

19. The stitched unidirectional or multi-axial reinforcement of claim 14 wherein the layers is a plurality of the layers and the single monofilament or the bundle of monofilaments is sandwiched between two of the layers.

20. The stitched unidirectional or multi-axial reinforcement of claim 14 wherein the layers is a plurality of the layers and the single monofilament or the bundle of monofilaments is on a top surface of a top one of the layers or on a bottom surface of a bottom one of the layers.

21. The stitched unidirectional or multi-axial reinforcement of claim 14 wherein the single monofilament or the bundle of monofilaments have a diameter of 100 μm to 200 μm.

22. The stitched unidirectional or multi-axial reinforcement of claim 14 wherein the stitching of the layer to the single monofilament or the bundle of monofilaments includes stitches, each of which has a length shorter than an interval between an adjacent one of the single monofilament or the bundle of monofilaments.

23. The stitched unidirectional or multi-axial reinforcement of claim 14 , wherein the single monofilament or the bundle of monofilaments has an elongation at break greater than an elongation at break of a matrix surrounding the layer and the single monofilament or the bundle of monofilaments.

24. The stitched unidirectional or multi-axial reinforcement of claim 14 , wherein the rovings are fibers formed of at least one of glass, carbon, aramid, basalt, flax, hemp, jute, and linen.

25. The stitched unidirectional or multi-axial reinforcement of claim 14 , wherein the single monofilament or the bundle of monofilaments has, under compression, an aspect ratio of less than or equal to two.

26. The stitched unidirectional or multi-axial reinforcement of claim 14 , wherein the single monofilament or the bundle of monofilaments is formed of at least one of polyamide (nylon), polyethylene terephthalate, polypropylene, polybutylene terephthalate, co-polyamide and copolyester (co-PET).