Composite materials with improved burn properties
View Patent ↗Epoxy resins and composite materials that generate reduced levels of sulfur dioxide and which unexpectedly have reduced self-extinguishing times. The epoxy resins are composed of from 50 to 70 weight percent of an epoxy resin component. The epoxy resin composition also includes from 20 to 35 weight percent of a thermoplastic blend that is composed of polyetherimide and polyamideimide. The epoxy resin composition further includes from 5 to 25 weight percent of a curative agent. The composite materials may be used for primary structures in aircraft and other load-bearing structures.
1. In an uncured composite part comprising a fiber reinforcement and an epoxy resin composition comprising one or more epoxy resins, polyetherimide and a curing agent, said epoxy resin composition being curable to form a cured resin which, when on fire, is able to self-extinguish once the source of heat and/or flame is removed from said cured resin, wherein the improvement comprises incorporating a sufficient amount of polyamideimide into said epoxy resin composition to reduce the time it takes said cured resin to self-extinguish.
2. The improved uncured composite part according to claim 1 wherein the weight ratio of polyetherimide to polyamideimide is from 3:1 to 1:3.
3. The improved uncured composite part according to claim 1 wherein the weight ratio of polyetherimide to polyamideimide is from 2:1 to 1:2.
4. The improved uncured composite part according to claim 1 wherein the weight ratio of polyetherimide to polyamideimide is from 2.5:1 to 2.9:1.
5. The improved uncured composite part according to claim 1 wherein said curative agent is selected from the group consisting of 3,3′-diaminodiphenyl sulphone, 4,4′-diaminodiphenyl sulphone and dicyandiamide.
6. The improved uncured composite part according to claim 1 wherein said curative agent consists essentially of a combination of 3,3′-diaminodiphenyl sulphone, 4,4′-diaminodiphenyl sulphone and dicyandiamide.
7. The improved uncured composite part according to claim 1 wherein said fiber reinforcement comprises unidirectional fibers.
8. A cured composite part that comprises an uncured composite part according to claim 1 wherein said epoxy resin composition has been cured to form said cured composite part.
9. A cured composite part according to claim 8 wherein said composite part forms at least part of a primary structure of an aircraft.
10. A cured composite part according to claim 8 wherein said composite part has an open hole compression value at room temperature of at least 45 kilograms per square inch.
11. In method for making an uncured composite part wherein one or more epoxy resins are mixed together with polyetherimide and a curing agent to form an epoxy resin composition that is combined with a fiber reinforcement, said epoxy resin composition being curable to form a cured resin which, when on fire, is able to self-extinguish once the source of heat and/or flame is removed from said cured resin, the improvement comprising incorporating a sufficient amount of polyamideimide into said epoxy resin composition to reduce the time it takes said cured resin to self-extinguish.
12. The improved method for making an uncured composite part according to claim 11 wherein the weight ratio of polyetherimide to polyamideimide is from 3:1 to 1:3.
13. The improved method for making an uncured composite part according to claim 11 wherein the weight ratio of polyetherimide to polyamideimide is from 2:1 to 1:2.
14. The improved method for making an uncured composite part according to claim 11 wherein the weight ratio of polyetherimide to polyamideimide is from 2.5:1 to 2.9:1.
15. The improved method for making an uncured composite part according to claim 11 wherein said curative agent is selected from the group consisting of 3,3′-diaminodiphenyl sulphone, 4,4′-diaminodiphenyl sulphone and dicyandiamide.
16. The improved method for making an uncured composite part according to claim 11 wherein said curative agent consists essentially of a combination of 3,3′-diaminodiphenyl sulphone, 4,4′-diaminodiphenyl sulphone and dicyandiamide.
17. The improved method for making an uncured composite part according to claim 11 wherein said fiber reinforcement comprises unidirectional fibers.
18. The improved method according to claim 11 which includes the additional step of curing said epoxy resin composition to form a cured composite part.
19. The improved method according to claim 18 wherein said cured composite part forms at least part of a primary structure of an aircraft.
20. The improved method according to claim 18 wherein said cured composite part has an open hole compression value at room temperature of at least 45 kilograms per square inch.