Bonding of composite materials

Patent metadata

Field	Value
Publication number	US-9789646-B2
Application number	US-201514923972-A
Country	US
Kind code	B2
Filing date	Oct 27, 2015
Priority date	Nov 3, 2014
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

A method for surface preparation of composite substrates prior to adhesive bonding. A curable surface treatment layer is applied onto a curable, resin-based composite substrate, followed by co-curing. After co-curing, the composite substrate is fully cured but the surface treatment layer remains partially cured. The surface treatment layer may be a resin film or a removal peel ply composed of resin-impregnated fabric. After surface preparation, the composite substrate is provided with a chemically-active, bondable surface that can be adhesively bonded to another composite substrate to form a covalently-bonded structure.

First claim

What is claimed is:

1. A method for surface preparation prior to adhesive bonding comprising:
(a) providing a composite substrate comprising reinforcing fibers impregnated with a first curable matrix resin;
(b) applying a surface treatment layer onto a surface of the composite substrate, said surface treatment layer comprising a woven fabric infused with a second curable matrix resin different from the first matrix resin, wherein the second matrix resin is formulated to cure at a slower rate than the first matrix resin;
(c) co-curing the composite substrate and the surface treatment layer until the composite substrate is fully cured but the surface treatment layer remains partially cured; and
(d) removing the surface treatment layer from the composite substrate's surface, leaving a thin film of partially cured matrix resin on the composite substrate's surface, said thin film providing a roughened, bondable surface with chemically-active functional groups.

2. The method of claim 1 , wherein the first and second curable matrix resins comprise one or more multifunctional epoxy resins.

3. The method of claim 1 , wherein the first and second matrix resins comprise different curing agents that are selected to affect curing at different rates.

4. The method of claim 3 , wherein
the first and second matrix resins comprise one or more epoxy resins,
the curing agents for the first and second matrix resins are selected from the group consisting of: melamine and substituted melamine derivatives, polymercaptan, polyamide, aliphatic polyamine, aromatic polyamine derivatives, tertiary amine boron trifluoride complex, acid anhydride, imidazoles, aromatic polyamine, cyanoguanadine, phenol novolac, and
the curing agents for the first and second curable matrix resin are selected to enable the first matrix resin to cure at a faster rate relative to that of the second matrix resin.

5. The method of claim 4 , wherein the first matrix resin comprises 1,3-bis(4-aminophenoxy)benzene, and the second matrix resin comprises 4,4′-diaminodiphenylsulfone or (3-(4-aminobenzoyl)oxyphenyl)-4-aminobenzoate, as curing agents.

6. The method of claim 4 , wherein the first matrix resin comprises 4,4′-diaminodiphenylsulfone or 3,3′-diaminodiphenylsulfone, and the second matrix resin comprises melamine, as curing agents.

7. The method of claim 4 , wherein the first matrix resin comprises the combination of 4,4′-diaminodiphenylsulfone and dicyanoguanadine, and the second matrix resin comprises 4,4′-diaminodiphenylsulfone or melamine, as curing agents.

8. The method of claim 4 , wherein the first matrix resin comprises 3,3′-diaminodiphenylsulfone, and the second matrix resin comprises 4,4′-diaminodiphenylsulfone, as curing agents.

9. The method of claim 4 , wherein the first matrix resin comprises Bis-aniline M, and the second matrix resin comprises 4,4′-diaminodiphenylsulfone, as curing agents.

10. The method of claim 4 , wherein the first matrix resin comprises 4,4′-diaminodiphenylsulfone, and the second matrix resin comprises (3-(4-aminobenzoyl) oxyphenyl)-4-aminobenzoate, as curing agents.

11. The method of claim 4 , wherein the first matrix resin comprises Bis-aniline P, and the second matrix resin comprises 3,3′-diaminodiphenylsulfone, as curing agents.

12. The method of claim 4 , wherein the first matrix resin comprises the combination of 3,3′-diaminodiphenylsulfone and isophthalic dihydrazide, and the second matrix resin comprises melamine, as curing agents.

13. The method of claim 1 , wherein the second curable matrix resin comprises one or more thermoset resins, a curing agent, and an inhibitor which can slow the rate of reaction between the one or more thermoset resins and the curing agent in the second matrix resin.

14. The method of claim 13 , wherein said inhibitor is selected from the group consisting of: boric acid; trifluoroborane; alkyl borate; alkyl borane; trimethoxyboroxine; organic acids having a pKa from 1 to 3, including maleic acid, salicyclic acid, oxalic acid; metal oxides, metal hydroxides, and alkoxides of metal, where the metal is selected from: zinc, tin, titanium, cobalt, manganese, iron, silicon, boron, or aluminum; and combinations thereof.

15. The method of claim 1 , wherein the first curable matrix resin comprises one or more thermoset resins, a curing agent, and an accelerator which can increase the rate of reaction between the one or more thermoset resins and the curing agent.

16. The method of claim 15 , wherein the first matrix resin comprises one or more epoxy resins and the accelerator is selected from compounds containing amine, phosphine, heterocyclic nitrogen, ammonium, phosphonium, arsenium or sulfonium moieties.

17. The method of claim 15 , wherein the first matrix resin comprises one or more epoxy resins and the accelerator is selected from the group consisting of: benzimidazoles, imidazoles, imidazolidines, imidazolines, oxazoles, pyrroles, thiazoles, pyridines, pyrazines, morpholines, pyridazines, pyrimidines, pyrrolidines, pyrazoles, quinoxalines, quinazolines, phthalozines, quinolines, purines, indazoles, indoles, indolazines, phenazines, phenarsazines, phenothiazines, pyrrolines, indolines, piperidines, piperazines, and combinations thereof.

18. A bonding method comprising:
(a) providing a first composite substrate comprising reinforcing fibers impregnated with a first curable matrix resin;
(b) applying a removable, resin-rich peel ply onto a surface of the first composite substrate, said peel ply comprising a woven fabric infused or impregnated with a second curable matrix resin, which is formulated to cure at a slower rate than the first curable matrix resin;
(c) co-curing the first composite substrate and the peel ply until the first composite substrate is fully cured but the second matrix resin in the peel ply remains partially cured;
(d) removing the peel ply from the first composite substrate's surface, leaving a thin film of partially cured second matrix resin on the first composite substrate's surface, said thin film providing a roughened, bondable surface with chemically-active functional groups;
(e) joining the cured, first composite substrate to a second composite substrate with a curable adhesive film in between the composite substrates,
wherein the curable adhesive film comprises chemically-active functional groups capable of reacting with the chemically-active functional groups on the bondable surface of the first composite substrate; and
(f) curing the adhesive film to form a covalently bonded structure.

19. The bonding method of claim 18 , wherein the second composite substrate is cured prior to being joined to the cured, first composite substrate.

20. The bonding method according to claim 18 , wherein the second composite substrate is uncured or partially cured prior to being joined to the first composite substrate, and during curing at (f), the adhesive film and the second composite substrate are cured simultaneously.

21. The bonding method of claim 18 , wherein the first and second curable matrix resins comprise different curing agents that are selected to affect curing at different rates.

Assignees

• Cytec Ind Inc

Inventors

• Macadams Leonard
• Kohli Dalip

Classifications

• B29C66/721

  Fibre-reinforced materials (B29C66/729 takes precedence) · CPC title

• B05D3/007

  After-treatment · CPC title

• B29C66/02245

  Abrading, e.g. grinding, sanding, sandblasting or scraping · CPC title

• C09J5/02

  involving pretreatment of the surfaces to be joined · CPC title

• B29C65/5057

  positioned between the surfaces to be joined (B29C65/5035 takes precedence) · CPC title