Composite material with thermoplastic toughened novolac-based epoxy resin matrix

1. A pre-impregnated composite material comprising:

(A) reinforcing fibers comprising carbon fibers; and

(B) an uncured resin matrix comprising an uncured resin that comprises:

(a) an epoxy resin component comprising from 9 to 18 weight percent hydrocarbon epoxy novolac resin, based on the total weight of the uncured resin, from 35 to 45 weight percent of a trifunctional epoxy resin and a tetrafunctional epoxy resin, based on the total weight of the uncured resin, wherein the weight ratio between the trifunctional epoxy resin and the tetrafunctional epoxy resin is from 1.0:1.5 to 1.5:1.0;

(b) from 9 to 15 weight percent of a thermoplastic particle component, based on the total weight of the uncured resin, said thermoplastic particle component comprising a mixture of polyimide particles and polyamide particles, said polyamide particles comprising a polyamide which is the polymeric condensation product of 1,10-decane dicarboxylic acid and an amine component having the formula

 where both R 2 are hydrogen and both R 1 are methyl and wherein the weight ratio between the polyamide particles and polyimide particles ranges from 3.5:1.0 to 1.0:1.0;

(d) from 7 to 14 weight percent of a thermoplastic toughening agent, based on the total weight of the uncured resin, said thermoplastic toughening agent comprising polyethersulfone; and

(e) from 20 to 30 weight percent of a curing agent, based on the total weight of the uncured resin, said curing agent comprising 3, 3′-diaminodiphenylsulfone and/or 4, 4′-diaminodiphenylsulfone.

2. A pre-impregnated composite material according to claim 1 wherein said trifunctional epoxy is a triglycidyl ether of para aminophenol.

3. A pre-impregnated composite material according to claim 2 wherein said tetrafunctional epoxy is a tetrafunctional para-glycidyl amine.

4. A pre-impregnated composite material according to claim 3 wherein said curing agent is 3, 3′-diaminodiphenylsulfone.

5. A pre-impregnated composite material according to claim 1 wherein the amount of said hydrocarbon epoxy novolac resin present in said uncured resin matrix is from 13 to 15 weight percent, based on the total weight of said uncured resin and the weight ratio between the polyamide particles and the polyimide particles is from 3.2:1.0 to 2.8:1.0.

6. A pre-impregnated composite material according to claim 5 wherein the minimum viscosity of said uncured resin matrix is from 25 to 75 Poise.

7. A pre-impregnated composite material according to claim 5 wherein the amount of said thermoplastic toughening agent present in said uncured resin matrix is from 10 to 13 weight percent, based on the total weight of said uncured resin, and said minimum viscosity is from 55 to 75 Poise.

8. A cured laminate comprising a plurality of layers comprising said pre-impregnated composite material according to claim 7 wherein said pre-impregnated composite material has be cured to form said cured laminate and wherein the G2c measurement of interlaminar fracture toughness of said cured laminate, as measured at room temperature according to BSS7320, is at least 10.

9. A primary aircraft structure or part comprising a cured laminate according to claim 8 .

10. A pre-impregnated composite material according to claim 5 wherein the amount of said thermoplastic toughening agent present in said uncured resin matrix is from 7 to 9 weight percent, based on the total weight of said uncured resin, and said minimum viscosity is from 25 to 45 Poise.

11. A cured laminate comprising a plurality of layers comprising said pre-impregnated composite material according to claim 1 wherein said pre-impregnated composite material has been cured to form said cured laminate and wherein the G2c measurement of interlaminar fracture toughness of said cured laminate, as measured at room temperature according to BSS7320, is at least 10.

12. A primary aircraft structure or part comprising a cured laminate according to claim 11 .

13. A method for making a pre-impregnated composite material comprising the steps of:

(A) providing reinforcing fibers comprising carbon fibers;

(B) providing an uncured resin matrix comprising an uncured resin that comprises:

(a) an epoxy resin component comprising from 9 to 18 weight percent hydrocarbon epoxy novolac resin, based on the total weight of the uncured resin, from 35 to 45 weight percent of a trifunctional epoxy resin and a tetrafunctional epoxy resin, based on the total weight of the uncured resin, wherein the weight ratio between the bifunctional epoxy resin and the tetrafunctional epoxy resin is from 1.0:1.5 to 1.5:1.0;

(b) from 9 to 15 weight percent of a thermoplastic particle component, based on the total weight of the uncured resin, said thermoplastic particle component comprising a mixture of polyimide particles and polyamide particles, said polyamide particles comprising a polyamide which is the polymeric condensation product of 1,10-decane dicarboxylic acid and an amine component having the formula

 where both R 2 are hydrogen and both R 1 are methyl and wherein the weight ratio between the polyamide particles and polyimide particles ranges from 3.5:1.0 to 1.0:1.0;

(d) from 7 to 14 weight percent of a thermoplastic toughening agent, based on the total weight of the uncured resin, said thermoplastic toughening agent comprising polyethersulfone; and

(e) from 20 to 30 weight percent of a curing agent, based on the total weight of the uncured resin, said curing agent comprising 3, 3′-diaminodiphenylsulfone and/or 4, 4′-diaminodiphenylsulfone; and

(C) combining said reinforcing fibers with said uncured resin matrix.

14. A method for making a pre-impregnated composite material according to claim 13 wherein the viscosity of said uncured resin matrix is from 55 to 75 Poise.

15. A method for making a pre-impregnated composite material according to claim 14 wherein the amount of said hydrocarbon epoxy novolac resin present in said uncured resin matrix is from 13 to 15 weight percent, based on the total weight of said uncured resin and the weight ratio between the polyamide particles and the polyimide particles is from 3.2:1.0 to 2.8:1.0.

16. A method for making a pre-impregnated composite material according to claim 15 Which includes the additional steps of forming said pre-impregnated material into an uncured laminate structure and curing said laminate structure to form a cured laminate wherein the G2c measurement of interlaminar fracture toughness of said cured laminate, as measured at room temperature according to BSS7320, is at least 10.

17. A composite part made according to the method of claim 16 .

18. A method for making a pre-impregnated composite material according to claim 13 wherein the minimum viscosity of said uncured resin matrix is from 25 to 45 Poise.