Hybrid veil as interlayer in composite materials

1. A hybrid veil that is flexible, self-supporting, and is permeable to liquid and gas, comprising:

(a) intermingled, randomly arranged carbon fibres in the form of a nonwoven structure;

(b) polymeric particles dispersed throughout the nonwoven structure, wherein a majority of the polymeric particles are penetrating through the thickness of the nonwoven structure; and

(c) a polymeric or resinous binder present throughout the veil,

wherein the fibres of the nonwoven structure are chopped fibres having lengths in the range of about 3 mm to about 18 mm and cross-sectional diameters in the range of about 3.0 μm to about 15 μm, and

wherein the particles are polyamide or polyimide particles consisting of polyamide or polyimide.

2. The hybrid veil according to claim 1 , wherein the hybrid veil has an areal weight of less than or equal to 12 gsm.

3. The hybrid veil according to claim 1 , wherein the weight ratio of carbon fibres to polymeric particles in the veil is within the range of 5:1 to 1:1.

4. The hybrid veil according to claim 1 , wherein the polymeric particles have a particle size distribution d50 in the range of about 10 μm to about 50 μm as measured by laser diffraction.

5. The hybrid veil according to claim 1 , wherein the polymeric or resinous binder comprises a component selected from the group consisting of: thermoplastic polymers, elastomeric polymers, thermosetting resins, copolymers thereof and combinations thereof.

6. The hybrid veil according to claim 1 , wherein the binder comprises a component selected from the group consisting of: vinyls; butadienes; silicones; polyesters; polyamides;

cross-linked polyesters; acrylics; epoxies; phenoxies; phenolics; polyurethanes; phenol-formaldehyde resin; urea-formaldehyde resin; copolymers thereof and combinations thereof.

7. A fabric that can be infused with a liquid resin, comprising:

at least one fabric ply comprising unidirectional fibers; and

a hybrid veil according to claim 1 attached to the fabric ply.

8. A fibrous preform configured for liquid resin infusion, comprising:

a plurality of fibrous layers that are permeable to liquid resin;

at least one hybrid veil according to claim 1 interleaved between two adjacent fibrous layers.

9. A method for manufacturing a composite structure, comprising:

forming a fibrous preform that is permeable to liquid resin, said fibrous preform comprising a plurality of fibrous layers and at least one hybrid veil according to claim 1 interleaved between adjacent fibrous layers;

infusing the fibrous preform with a liquid resin comprising one or more thermoset resins; and

curing the resin-infused preform,

wherein, after curing, the at least one hybrid veil forms an interlaminar region having a thickness of less than 80 μm.