Composite laminate with self-healing layer

Abstract

A composite structure comprising: a first stack comprising a plurality of plies of composite material and at least one ply of self-healing material, the ply of self-healing material comprising a plurality of containers each containing a curable healing liquid; and a second stack comprising a plurality of plies of composite material, the stacks being joined together at a bond line. By placing a ply of self-healing material in one of the stacks (preferably relatively close to the bond line) the ply of self-healing material can resist the propagation of cracks between the first stack and the second stack. Preferably the global strength of the first stack is greater than the global strength of the second stack.

1 . A composite structure comprising: a first stack comprising a plurality of plies of composite material and at least one ply of self-healing material, the ply of self-healing material comprising a plurality of containers each containing a curable healing liquid; and a second stack comprising a plurality of plies of composite material, the stacks being joined together at a bond line. 
     
     
         2 . The structure of  claim 1  wherein the first stack comprises N plies arranged in a stacking sequence including a first ply at one end of the stacking sequence which is adjacent to the bond line and an Nth ply at another end of the stacking sequence which is remote from the bond line, and wherein the ply of self-healing material is located relatively close to the bond line in the sense that its position in the stacking sequence is less than N/2. 
     
     
         3 . The structure of  claim 2  wherein the ply of self-healing material is the first, second, third or fourth ply in the stacking sequence. 
     
     
         4 . The structure of  claim 2  wherein the ply of self-healing material is not the first ply in the stacking sequence. 
     
     
         5 . The structure of  claim 1  wherein the bond line comprises a layer of adhesive. 
     
     
         6 . The structure of  claim 1  wherein the stacks are co-cured at the bond line. 
     
     
         7 . The structure of  claim 1  wherein the first stack has a total thickness T 2  and the plies of self-healing material have a total thickness T 1 , and wherein the ratio T 1 /T 2  is less than 0.1. 
     
     
         8 - 13 . (canceled) 
     
     
         14 . A method of forming a composite joint, the method comprising: assembling a first stack comprising a plurality of plies of composite material and at least one ply of self-healing material, the ply of self-healing material comprising a plurality of containers each containing a curable healing liquid; assembling a second stack comprising a plurality of plies of composite material; and bonding the stacks together at a bond line after they have both been assembled. 
     
     
         15 . A method of deflecting a crack in the composite structure of  claim 1 , the crack originating in the bond line or the second stack, the method comprising breaking at least some of the containers in the self-healing layer such that the curable healing liquid flows from the broken containers and cures, thereby deflecting the crack. 
     
     
         16 . A method according to  claim 14  wherein the first stack comprises N plies arranged in a stacking sequence including a first ply at one end of the stacking sequence which is adjacent to the bond line and an Nth ply at another end of the stacking sequence which is remote from the bond line, and wherein the ply of self-healing material is located relatively close to the bond line in the sense that its position in the stacking sequence is less than N/2. 
     
     
         17 . A method according to  claim 16  wherein the ply of self-healing material is a first, second, third or fourth ply in the stacking sequence. 
     
     
         18 . A method according to  claim 16  wherein the ply of self-healing material is not the first ply in the stacking sequence. 
     
     
         19 . A method according to  claim 14  wherein the bond line comprises a layer of adhesive. 
     
     
         20 . A method according to  claim 14  wherein the stacks are co-cured at the bond line. 
     
     
         21 . A method according to  claim 14  wherein the first stack forms a primary structure, the second stack forms a secondary structure, and a global strength of the secondary structure is less than a global strength of the primary structure. 
     
     
         22 . A method according to  claim 14  wherein each ply of composite material in the first stack comprises a plurality of reinforcement fibres embedded within a matrix, and each ply of composite material in the second stack comprises a plurality of reinforcement fibres embedded within a matrix.