Multifunctional surfacing material with burn-through resistance
A multifunctional surfacing material capable of providing lightning strike protection (LSP) and burn-through resistance. In one embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers, at least one of which contains one or more fire retardant compounds. In another embodiment, the multifunctional surfacing material is composed of a conductive layer positioned between two resin layers one of which is a thermally-stable layer. The surfacing material is co-curable with a composite substrate, e.g. prepreg or prepreg layup, which contains fiber-reinforced matrix resin.
1. A multifunctional surfacing material capable of providing lightning strike protection (LSP) and burn-through resistance, comprising a conductive layer positioned between a first resin layer and a second resin layer,
wherein at least one of the first and second resin layers comprises:
(a) a blend of multifunctional epoxy resins;
(b) a curing agent;
(c) a polymeric toughening component;
(d) ceramic microspheres; and
(e) a fire-retardant component comprising a phosphorous-modified epoxy resin or phosphorous-modified phenolic resin;
wherein the first and second resin layers do not contain any reinforcement fibers.
2. The multifunctional surfacing material of claim 1 , wherein the fire-retardant component further comprises one or more organic phosphorous-containing compounds selected from: trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tributoxyethyl phosphate, tricresyl phosphate, cresyldiphenyl phosphate, octyldiphenyl phosphate, polyphosphonate, and polyphosphate.
3. The multifunctional surfacing material of claim 1 , wherein the fire-retardant component further comprises one or more inorganic phosphorous-containing compounds selected from: red phosphorous, melamine phosphate, melamine polyphosphate, ammonium polyphosphate, dimelamine phosphate, pyrophosphate, and inorganic phosphinates.
4. The multifunctional surfacing material of claim 1 , wherein the fire-retardant component further comprises one or more boron-containing compounds selected from: zinc borate, barium metaborate, and calcium metaborate.
5. The multifunctional surfacing material of claim 1 , wherein the phosphorous-modified epoxy resin or phosphorous-modified phenolic resin is a reaction product obtained by reacting a multifunctional epoxy or phenolic resin with an organic phosphinic acid or anhydride thereof.
6. The multifunctional surfacing material of claim 1 , further comprising a smoke-suppressant selected from metal hydroxides.
7. The multifunctional surfacing material of claim 6 , wherein the smoke-suppressant is alumina trihydrate (ATH).
8. The multifunctional surfacing material of claim 1 , further comprising an inorganic filler in particulate form.
9. The multifunctional surfacing material of claim 8 , wherein the inorganic filler is silica.
10. The multifunctional surfacing material of claim 1 , wherein the polymeric toughening component (c) 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.
11. The multifunctional surfacing material of claim 1 , wherein the blend of multifunctional epoxy resins comprises a difunctional epoxy resin and a trifunctional or tetrafunctional epoxy resin.
12. The multifunctional surfacing material of claim 1 , wherein the second resin layer is substantially the same in composition as the first resin layer.
13. The multifunctional surfacing material of claim 1 , wherein the conductive layer is a porous or nonporous metallic layer.
14. The multifunctional surfacing material of claim 1 , wherein the conductive layer is a nonporous metal foil having a thickness of less than about 76 μm.
15. 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.
16. The multifunctional surfacing material according to claim 15 , wherein the conductive layer is a metal screen or an expanded metal foil.
17. 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.
18. A composite structure comprising:
a composite substrate comprising reinforcement fibers impregnated or infused with a curable matrix resin;
the multifunctional conductive surfacing material of claim 1 laminated to a surface of the composite substrate.
19. The composite structure of claim 18 , 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.
20. A method for forming a composite structure comprising:
applying the multifunctional surfacing material of claim 1 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.