FIBER-MODIFIED INTERLAYER FOR A COMPOSITE STRUCTURE AND METHOD OF MANUFACTURE

1 . A fiber-modified interlayer comprising:

a nonwoven fabric layer formed of continuous fibers; and

discontinuous fibers attached to said nonwoven fabric layer.

2 . The fiber-modified interlayer of claim 1 wherein said discontinuous fibers are attached to said nonwoven fabric layer by drawing said nonwoven fabric layer through a slurry of said discontinuous fibers suspended in a dispersive liquid.

3 . The fiber-modified interlayer of claim 1 wherein said discontinuous fibers are mechanically bonded to said continuous fibers forming at least one surface of said nonwoven fabric layer.

4 . The fiber-modified interlayer of claim 1 wherein said discontinuous fibers are mechanically bonded to said continuous fibers forming opposed surfaces of said nonwoven fabric layer.

5 . The fiber-modified interlayer of claim 1 wherein said continuous fibers are made of a thermoplastic material, and wherein said discontinuous fibers are made of a carbonaceous material.

6 . The fiber-modified interlayer of claim 5 wherein said carbonaceous material comprises at least one of carbon nanotubes, graphene platelets, carbon whiskers, chopped carbon fibers, milled carbon fibers and carbon nanofibers.

7 . The fiber-modified interlayer of claim 1 wherein at least some of the discontinuous fibers are interspersed through a thickness of said nonwoven fabric layer and are entangled with at least some of said continuous fibers.

8 . The fiber-modified interlayer of claim 1 wherein said fiber-modified interlayer is disposed between reinforcing layers formed of structural tows to form an interlayer-toughened reinforcing fabric, wherein said interlayer-toughened reinforcing fabric is configured to be infused with a matrix material to form a composite structure, and wherein said fiber-modified interlayer is configured to increase impact resistance and electrical conductivity of said composite structure.

9 . An interlayer-toughened reinforcing fabric comprising:

at least one reinforcing layer formed of structural tows; and

at least one fiber-modified interlayer attached to said reinforcing layer, wherein said fiber-modified interlayer comprises:

a nonwoven fabric layer formed of continuous fibers; and

discontinuous fibers attached to said nonwoven fabric layer.

10 . The interlayer-toughened reinforcing fabric of claim 9 wherein a layup of at least one layer of said interlayer-toughened reinforcing fabric is configured to be infused with a matrix material and cured to form a composite structure, and wherein said fiber-modified interlayer is configured to increase impact resistance and electrical conductivity of said composite structure.

11 . The interlayer-toughened reinforcing fabric of claim 9 wherein said fiber-modified interlayer is melt-bonded to said reinforcing layer.

12 . The interlayer-toughened reinforcing fabric of claim 11 further comprising a matrix material infused into said interlayer-toughened reinforcing fabric and partially cured to form a pre-impregnated interlayer-toughened reinforcing fabric, wherein a layup of at least one layer of said pre-impregnated interlayer-toughened reinforcing fabric is configured to be fully cured to form a composite structure, and wherein said fiber-modified interlayer is configured to increase impact resistance and electrical conductivity of said composite structure.

13 . The interlayer-toughened reinforcing fabric of claim 9 further comprising:

a plurality of reinforcing layers formed of said structural tows; and

a plurality of fiber-modified interlayers disposed alternately between said reinforcing layers, wherein each of said fiber-modified interlayers comprises:

said nonwoven fabric layer formed of said continuous fibers; and

said discontinuous fibers attached to said nonwoven fabric layer.

14 . The interlayer-toughened reinforcing fabric of claim 13 further comprising stitching extending through said reinforcing layers and said fiber-modified interlayers to bond said reinforcing layers and said fiber-modified interlayers together.

15 . The interlayer-toughened reinforcing fabric of claim 13 wherein a layup of at least one layer of said interlayer-toughened reinforcing fabric is configured to be infused with a matrix material and cured to form a composite structure, and wherein said fiber-modified interlayer is configured to increase impact resistance and electrical conductivity of said composite structure.

16 . A composite structure comprising:

at least one layer of an interlayer-toughened reinforcing fabric, wherein said interlayer-toughened reinforcing fabric comprises at least one reinforcing layer formed of structural tows and at least one fiber-modified interlayer attached to said reinforcing layer arranged in an alternating configuration, and wherein said fiber-modified interlayer comprises a nonwoven fabric layer formed of continuous fibers and discontinuous fibers attached to said nonwoven fabric layer; and

a matrix material infused into said interlayer-toughened reinforcing fabric.

17 . A method for manufacturing a fiber-modified interlayer comprising:

drawing a nonwoven fabric formed of continuous fibers through a slurry of discontinuous fibers suspended in a dispersive liquid;

forming a network of said discontinuous fibers attached to said nonwoven fabric; and

forming said fiber-modified interlayer.

18 . The method of claim 17 wherein forming said network of said discontinuous fibers attached to said nonwoven fabric comprises:

mechanically bonding a first portion of said discontinuous fibers to at least some of said continuous fibers forming at least one surface of said nonwoven fabric; and

mechanically bonding a second portion of said discontinuous fibers to said first portion of said discontinuous fibers.

19 . The method of claim 18 wherein forming said network of said discontinuous fibers attached to said nonwoven fabric further comprises interspersing at least some of the first portion of said discontinuous fibers through a thickness of said nonwoven fabric.

20 . A method for manufacturing an interlayer-toughened reinforcing fabric comprising:

arranging a least one reinforcing layer formed of structural tows and at least one fiber-modified interlayer in an alternating configuration, wherein said fiber-modified interlayer comprises a nonwoven fabric layer formed of continuous fibers, and discontinuous fibers attached to said nonwoven fabric layer; and

attaching said reinforcing layer and said fiber-modified interlayer together.

21 . The method of claim 20 wherein attaching said reinforcing layer and said fiber-modified interlayer together comprises melt-bonding said fiber-modified interlayer to said reinforcing layer.

22 . The method of claim 21 further comprising pre-impregnating said reinforcing layer and said fiber-modified interlayer with a matrix material.

23 . The method of claim 20 further comprising:

arranging a plurality of reinforcing layers formed of said structural tows and a plurality of fiber-modified interlayers in an alternating configuration, wherein each of said fiber-modified interlayers comprises:

said nonwoven fabric layer formed of said continuous fibers; and

said discontinuous fibers attached to said nonwoven fabric layer; and

attaching said reinforcing layers and said fiber-modified interlayers together.

24 . The method of claim 23 wherein attaching said reinforcing layers and said fiber-modified interlayer together comprises stitching said reinforcing layers and said fiber-modified interlayer together with a thread.

25 . A method for manufacturing a composite structure comprising:

laying up at least one layer of an interlayer-toughened reinforcing fabric onto a mold, wherein said interlayer-toughened reinforcing fabric comprises a least one reinforcing layer formed of structural tows, and at least one fiber-modified interlayer attached to said reinforcing layer arranged in an alternating configuration, and wherein said fiber-modified interlayer comprises a nonwoven fabric layer formed of continuous fibers, and discontinuous fibers attached to said nonwoven fabric layer;

infusing said interlayer-toughened reinforcing fabric with a matrix material; and

curing said matrix material.

26 . A method for dissipating electromagnetic energy through a composite structure, said method comprising:

imparting said electromagnetic energy on a surface of said composite structure, said composite structure comprising a reinforcing material and a matrix material;

dispersing said electromagnetic energy laterally along a continuously conductive path; and

transferring said electromagnetic energy to a ground plane coupled to said composite structure.

27 . The method of claim 26 wherein:

said reinforcing material comprises at least one reinforcing layer and at least one fiber-modified interlayer attached to said reinforcing layer arranged in an alternating configuration, and

said continuously conductive path is formed by said fiber-modified interlayer.

28 . A method for dissipating impact energy through a composite structure, said method comprising:

imparting said impact energy on a surface of said composite structure, said composite structure comprising a reinforcing material and a matrix material;

deflecting said impact energy laterally along said composite structure; and

suppressing damage growth through a thickness of said composite structure.

29 . The method of claim 28 wherein:

said reinforcing material comprises at least one reinforcing layer and at least one fiber-modified interlayer attached to said reinforcing layer arranged in an alternating configuration,

said impact energy is deflected laterally along said fiber-modified interlayer, and

said damage growth through said thickness of said composite structure is suppressed by said fiber-modified interlayer.