Method of bonding a chrome steel to a fibre composite

Abstract

A method of bonding a high chrome steel to a fiber composite. An epoxy primer is applied to the high chrome steel, the primer is dried, and thereafter the high chrome steel and the fiber composite are adhered together by using an epoxy adhesive. The invention also includes bonded joints that are made by the method and bonded assemblies having the bonded joint. A joint made using this bonded method has a high torque-to-failure, even after exposure to extreme ambient conditions of high temperature and high relative humidity. The bonding method is particularly suitable for use in bonding high chrome steel and fiber composite components for use in the aerospace industry.

1 . A method of bonding a first high chrome steel adherend to a second fibre composite adherend, which method comprises the steps of applying an epoxy primer to said first adherend, causing or allowing said primer to dry and thereafter adhering the first and second two adherends together using an epoxy adhesive.  
     
     
         2 . A method as claimed in    claim 1   , wherein said high chrome steel comprises an aerospace grade steel.  
     
     
         3 . A method as claimed in    claim 1   , wherein said high chrome steel comprises 12 to 20% by weight of chromium.  
     
     
         4 . A method as claimed in    claim 1   , wherein said steel comprises 0 to 8% by weight nickel.  
     
     
         5 . A method as claimed in    claim 1   , wherein said first high chrome steel adherend comprises a 17/4 grade steel.  
     
     
         6 . A method as claimed in    claim 1   , wherein second fibre composite adherend comprises an aerospace-grade fibre-reinforced composite material comprising an epoxy resin.  
     
     
         7 . A method as claimed in    claim 1   , wherein said composite comprises a carbon fibre-reinforced composite material.  
     
     
         8 . A method as claimed in    claim 1   , wherein said second fibre composite adherend comprises the material 6378cHTA(12K-5-35) which is commercially available from Hexcel Corporation.  
     
     
         9 . A method as claimed in    claim 1   , wherein said first adherend is pre-treated by abrading or etching before the primer is applied.  
     
     
         10 . A method as claimed in    claim 9   , wherein said first high chrome steel adherend is degreased to remove contaminants before abrading or etching.  
     
     
         11 . A method as claimed in    claim 1   , wherein said second adherend is degreased before application of said adhesive.  
     
     
         12 . A method as claimed in    claim 1   , wherein said second adherend is pre-treated by abrading to remove contaminants and/or loose or weakly bound material.  
     
     
         13 . A method as claimed in any    claim 1   , wherein said epoxy primer has a rheology and chemical composition that is selected to match the morphology and surface chemistry of the first adherend.  
     
     
         14 . A method as claimed in    claim 1   , wherein said primer is water based, having a solids content of 5-15% weight.  
     
     
         15 . A method as claimed in    claim 1   , wherein said primer comprises a hardening agent.  
     
     
         16 . A method as claimed in    claim 1   , wherein said primer comprises an anti-corrosion agent.  
     
     
         17 . A method as claimed in    claim 16    wherein said anti-corrosion agent comprises a zinc salt and/or a chromate salt.  
     
     
         18 . A method as claimed in    claim 1   , wherein said primer comprises an aqueous epoxy resin dispersion which contains as a distinct phase a solid epoxy curing agent.  
     
     
         19 . A method as claimed in    claim 18   , wherein said aqueous epoxy resin dispersion comprises one or more solid epoxy resins.  
     
     
         20 . A method as claimed in    claim 19   , wherein one or more of said solid epoxy resins comprises a glycidyl ether of a phenol or a glycidyl derivative of an aromatic amine or aminophenol.  
     
     
         21 . A method as claimed in    claim 18   , wherein said curing agent is substantially water insoluble and solid at room temperature.  
     
     
         22 . A method as claimed in    claim 18   , wherein said curing agent comprises an aromatic amine or diamine curing agent.  
     
     
         23 . A method as claimed in    claim 18   , wherein said primer further comprises a chromate or non-chromate corrosion inhibitor.  
     
     
         24 . A method as claimed in    claim 1   , wherein said primer is BR®6747-1-A which is commercially available from Cytec Industries Inc.  
     
     
         25 . A method as claimed in    claim 1   , wherein said primer consists of a chromate-free equivalent to BR®6747-1-A.  
     
     
         26 . A method as claimed in    claim 12    wherein said primer is pre-cured.  
     
     
         27 . A method as claimed in    claim 1   , wherein said epoxy adhesive comprises a film adhesive or paste adhesive.  
     
     
         28 . A method as claimed in    claim 1   , wherein said adhesive comprises a carrier that is formed from a polymeric plastics material.  
     
     
         29 . A method as claimed in    claim 1   , wherein said adhesive is a modified epoxy adhesive.  
     
     
         30 . A method as claimed in    claim 1   , wherein said adhesive is FM300K.05 which is available from Cytec Engineering Materials Inc.  
     
     
         31 . A method as claimed in    claim 1   , wherein the second adherend is used uncured and, after application of said primer to the first adherend and application of the adhesive, the composite material is co-cured with the primer and adhesive.  
     
     
         32 . A bonded joint comprising a first-chrome steel adherend and a second fibre composite adherend, which first and second adherend bonded together using a method of bonding as claimed in    claim 1   .  
     
     
         33 . A bonded assembly comprising a first high chrome component and a second fibre composite component, which first and second components are bonded together using a method of bonding as claimed in    claim 1   .  
     
     
         34 . A bonded assembly as claimed in    claim 33   , which assembly comprises a rotary drive shaft comprising a fibre composite tube and high chrome steel flange, which tube and flange are bonded together using said bonding method.  
     
     
         35 . An assembly as claimed in    claim 34   , wherein said tube is formed with at least one flared end, and the or each tube is deformed to form an integrant flange portion having an annular bonding face.  
     
     
         36 . An assembly as claimed in    claim 35   , wherein the joint between the tube and the flange is reinforced by rivets, bolts or any other suitable mechanical fixings.