Methods for Bonding Composite Structures Using Interpenetrating Polymer Network Adhesives

Abstract

An interpenetrating polymer network (IPN) adhesive comprises an acrylated polymer system curable by radiation, and a flexible epoxy system thermally curable after the acrylated polymer system is cured.

1 - 25 . (canceled) 
     
     
         26 . A method of bonding two parts together, the method comprising:
 placing the parts together with a layer of an interpenetrating polymer network (IPN) adhesive between the parts, the IPN adhesive contacting both parts, the parts comprising a metal part and a composite part, the composite part comprising a fiber reinforced polymer matrix;   attaching the parts to each other by curing a first polymer system of the IPN adhesive using radiation energy, wherein the first polymer system is cured to a stage that allows handling of the parts; and   thermally curing a second polymer system of the IPN adhesive after the first polymer system has been cured.   
     
     
         27 . The method of  claim 26 , wherein:
 curing the first polymer system is performed substantially at room temperature using a beam of the radiation energy, and   thermally curing the second polymer system is performed at a temperature above room temperature.   
     
     
         28 . The method of  claim 26 , wherein the first polymer system is an acrylated epoxy forming a first substantially continuous structure when cured that attaches and holds the parts together until the second polymer system is cured. 
     
     
         29 . The method of  claim 26 , wherein the second polymer system is selected from the group consisting of:
 a substantially flexible epoxy, and   a substantially flexible vinyl ester.   
     
     
         30 . The method of  claim 26 , wherein the parts have respectively different coefficients of thermal expansion. 
     
     
         31 . The method of  claim 26 , wherein the first polymer system is an acrylated epoxy curable by radiation selected from the group consisting of an electron beam, ultraviolet light and x-rays. 
     
     
         32 . The method of  claim 31 , wherein the second polymer system is a flexible epoxy. 
     
     
         33 . The method of  claim 31 , wherein the acrylated epoxy includes at least one of:
 bisphenol A diacrylate (BPADA);   a trifunctional acrylate; and   trimethylolpropane triacrylate (TMPTA).   
     
     
         34 . The method of  claim 26 , wherein the parts are components of an aircraft. 
     
     
         35 . The method of  claim 31 , wherein the IPN adhesive has a modulus that approaches that of the acrylated epoxy and an elongation that approaches that of the flexible epoxy. 
     
     
         36 . The method of  claim 31 , wherein the acrylated epoxy functions as a high strength adhesive which bonds the parts together, and wherein the flexible epoxy provides the IPN adhesive with some resistance to impact loads. 
     
     
         37 . The method of  claim 31 , wherein the IPN adhesive comprises approximately 67% acrylated epoxy and 33% flexible epoxy and curing agent. 
     
     
         38 . The method of  claim 31 , wherein the IPN adhesive comprises approximately 40% acrylated epoxy, and approximately 60% flexible epoxy and curing agent. 
     
     
         39 . The method of  claim 31 , wherein the IPN adhesive comprises acrylated epoxy in the range of approximately 40% to approximately 67% of the IPN adhesive. 
     
     
         40 . A method of bonding parts together, the parts comprising a metal part and a composite part, the composite part comprising a fiber reinforced polymer matrix, the method comprising:
 placing the parts together with a layer of an interpenetrating polymer network (IPN) adhesive between the parts;   attaching the parts to each other by curing a first polymer system of the IPN adhesive at room temperature using an electron beam of radiant energy until the parts have sufficient rigidity to be handled, wherein the first polymer system is an acrylated epoxy forming a first substantially continuous structure when cured that attaches and locks the parts together until a second polymer system is cured; and   thermally curing the second flexible polymer system of the IPN adhesive after the first polymer system has been cured using a thermal cure cycle above room temperature, wherein the second polymer system is selected from the group consisting of a substantially flexible epoxy, and a substantially flexible vinyl ester.   
     
     
         41 . The method of  claim 40 , wherein the parts have respectively different coefficients of thermal expansion. 
     
     
         42 . The method of  claim 40 , wherein the acrylated epoxy includes at least one of:
 bisphenol A diacrylate (BPADA);   a trifunctional acrylate; and   trimethylolpropane triacrylate (TMPTA).   
     
     
         43 . The method of  claim 40 , wherein the parts are components of an aircraft. 
     
     
         44 . The method of  claim 40 , wherein the IPN adhesive has a modulus that approaches that of the acrylated epoxy and an elongation that approaches that of the flexible epoxy. 
     
     
         45 . The method of  claim 40 , wherein the acrylated epoxy functions as a high strength adhesive which bonds the parts together, and wherein the flexible epoxy provides the IPN adhesive with some resistance to impact loads.