Multifunctional surfacing material with burn-through resistance

1. A multifunctional surfacing material capable of providing lightning strike protection (LSP) and burn-through resistance, comprising a conductive layer positioned between a curable resin layer and a silicone layer,

wherein the silicone layer comprises a blend of silicone polymers, which comprises one or more polydiorganosiloxane homopolymers of the general formula (I) and one or more silicone copolymers of the general formula (II):

wherein

for formula (I), R 1 and R 2 are the same or different and are independently selected from hydrogen, alkyl group having from 1 to 6 carbon atoms, including methyl, ethyl, phenyl group, vinyl group, and a halogenated alkyl, phenyl, or vinyl group: R 3 is the same as R 1 or R 2 or an hydroxy group; and n is an integer of from 0 to 10,000;

for formula (II), at least one of R 4 , R 5 and R 6 are different and are individually selected from hydrogen, alkyl group, alkyl phenyl group and vinyl group, where alkyl is as described above for formula (I); and m is an integer of from 1 to 10,000, and

wherein the curable resin layer and the silicone layer do not comprise any reinforcement fibers.

2. The multifunctional surfacing material of claim 1 , wherein the one or more silicone homopolymers is/are selected from silsesquioxane polymer, polydimethylsiloxane (or PDMS), polydiphenylsiloxane, polydiethylsiloxane, and silanol terminated polydimethyl siloxane.

3. The multifunctional surfacing material of claim 1 , wherein the copolymer is phenylsilsesquioxane-dimethylsiloxane copolymer.

4. The multifunctional surfacing material according to claim 1 , wherein the blend of silicone polymers further comprises an inorganic oxide filler.

5. The multifunctional surfacing material according to claim 4 , wherein the silicone layer comprises:

phenylsilsesquioxane-dimethylsiloxane copolymer;

silanol-terminated polydimethylpolysiloxane;

silsesquioxane polymer;

zinc octoate (as catalyst); and

inorganic oxide filler.

6. The multifunctional surfacing material according to claim 1 , wherein the curable resin layer comprises a blend of multifunctional epoxy resins and a curing agent.

7. The multifunctional surfacing material according to claim 6 , wherein the curable resin layer further comprises a fire-retardant compound selected from: organic phosphorous-containing compounds; inorganic phosphorous-containing compounds; Melamine Cyanurate; polyphosphazenes; a phosphorous-modified epoxy or phenolic resin; boron-containing compounds, and combinations thereof.

8. The multifunctional surfacing material according to claim 6 , wherein the curable resin layer further comprises a toughening material selected from:

(i) an elastomeric or thermoplastic polymer;

(ii) a pre-react adduct formed by the reaction of an epoxy resin, a bisphenol, and an elastomer;

(iii) a copolymer of polyether sulfone (PES) and polyetherether sulfone (PEES);

(iv) core-shell rubber (CSR) particles;

and combinations thereof.

9. The multifunctional surfacing material according to claim 6 , wherein the curable resin layer further comprises ceramic microspheres.

10. The multifunctional surfacing material of claim 1 , wherein the conductive layer is a porous or nonporous metallic layer.

11. The multifunctional surfacing material according to claim 10 , wherein the conductive layer is made of copper, aluminum, bronze, titanium, or alloys thereof.

12. The multifunctional surfacing material according to claim 1 , wherein the conductive layer is a nonporous metal foil having a thickness of less than about 76 μm.

13. The multifunctional surfacing material of claim 1 , wherein the conductive layer is a porous layer with an areal weight within the range of about 60 gsm to about 350 gsm.

14. The multifunctional surfacing material according to claim 13 , wherein the conductive layer is a metal screen or an expanded metal foil.

15. The multifunctional surfacing material of claim 1 , wherein the surfacing material is in the form of a continuous or elongated tape having a width in the range of about 0.125 in to about 12 in.

16. A composite structure comprising:

a composite substrate comprising reinforcement fibers impregnated or infused with a curable matrix resin; and

a multifunctional conductive surfacing material laminated to a surface of the composite substrate,

wherein the multifunctional conductive surfacing material comprises a conductive layer positioned between a curable resin layer and a silicone layer comprising a blend of silicone polymers.

17. The composite structure of claim 16 , wherein the composite substrate is a prepreg layup, which comprises a plurality of prepreg plies arranged in a stacking arrangement, each prepreg ply comprising reinforcing fibers impregnated with or embedded in a curable matrix resin.

18. A method for forming a composite structure comprising:

forming a multifunctional surfacing material comprising a conductive layer positioned between a curable resin layer and a silicone layer, wherein the silicone layer comprises a blend of silicone polymers,

applying the multifunctional surfacing material to a surface of a composite substrate, which comprises reinforcement fibers impregnated with or embedded in a curable matrix resin; and

co-curing the surfacing material together with the composite substrate.

19. The method of claim 18 , wherein the composite substrate is a prepreg layup comprising a plurality of prepreg plies arranged in a stacking arrangement, each prepreg ply comprising reinforcing fibers impregnated with or embedded in a curable matrix resin.