Non-crimp fabrics

Abstract

A method of producing a non-crimp fabric ( 10 ) and a non-crimp fabric comprising a layup of fabric plies ( 12 ) stitched together by a thread ( 18 ), at least part of which is fusible, is provided. The method can include heating the stitched plies ( 12 ) to soften or melt the fusible thread ( 18 ). The use of fusible thread ( 18 ) can act as an in situ binder within the non-crimp fabric ( 10 ) and tension created by the unfused stitching may create channels for matrix resin infusion during manufacture.

1 . A method of draping a non crimp fabric over a forming tool, the method including the steps of: 
 providing a non crimp fabric comprising a layup of plies stitched together using a thread at least part of which is fusible;    placing the non crimp fabric on the forming tool, and    heating the non crimp fabric sufficiently at least to soften the fusible thread as the non crimp fibric drapes over the tool, whereby to reduce the restriction to drape caused by the stitching.    
     
     
         2 . A method according to  claim 1  in which the plies are heated to a temperature not greater than the fusion temperature of the thread.  
     
     
         3 . A method according to  claim 1  in which the plies are heated to a temperature above the fusion temperature of the thread.  
     
     
         4 . A method according to  claim 3  in which pressure is applied to conform the plies to the shape of the tool and the plies are cooled, while under pressure, whereby to create a preform with the fused thread acting as an in situ binder within the non-crimp fabric.  
     
     
         5 . A method according to any one of  claims 1  to  4  including creating tension in the un-fused stitching to create resin transfer channels in the non-crimp fabric.  
     
     
         6 . A method according to any preceding claim in which matrix resin is infused through the non-crimp fabric.  
     
     
         7 . A method according to claims  5  or  6  including selecting a matrix resin which is chemically compatible with the fusible thread.  
     
     
         8 . A method according to any one of  claims 5  to  7  including selecting a matrix resin and a fusible thread with a similar modulus.  
     
     
         9 . A method according to any one of  claims 5  to  8  in which the fusible thread remains as a separate phase from the matrix resin, dissolves in the matrix resin or precipitates out as the matrix resin is cured or allowed to set.  
     
     
         10 . A method according to any one of  claims 5  to  9  in which the stitching is selected so that the fused stitching acts as a toughening phase within the resin infused non-crimp fabric.  
     
     
         11 . A method according to any preceding claim in which the non crimp fabric provided comprises from 0.5% to 10% fusible thread by mass.  
     
     
         12 . A method according to  claim 11  in which the non-crimp fabric provided comprises from 1% to 3% fusible thread by mass.  
     
     
         13 . A method according to any preceding claim including melting or dissolving the fusible thread at a temperature between 40° C. and 250° C.  
     
     
         14 . A method according to any preceding claim including selecting a fusible thread with a glass transition temperature (T g ) of greater than 120° C. after curing.  
     
     
         15 . A method according to any preceding claim in which the fusible thread is constructed from two or more parts comprising different materials, each having a different fusion temperature.  
     
     
         16 . A method according to  claim 15  in which at least one of the materials from which the thread is constructed is infusible.  
     
     
         17 . A method according to  claim 16  in which the said infusible part of the thread is non-continuous.  
     
     
         18 . A method according to  claim 16  or  17  in which the said infusible part of the thread is of polyester.  
     
     
         19 . A method according to any preceding claim in which the stitching is run substantially transversely through the plies.  
     
     
         20 . A method according to  claim 19  in which the stitching is carried out in a predetermined pattern and is selected from the group: tricot closed, open pillar stitch, closed pillar stitch, open tricot-pillar stitch or closed tricot-pillar stitch.  
     
     
         21 . A method according to any preceding claim including providing a said non crimp fabric in which the plies are multi-axial.  
     
     
         22 . A method according to any preceding claim in which fibres of each ply are placed in directions of 0°, +45°, −45° and 90°.  
     
     
         23 . A method according to any preceding claim in which fibres of each ply are placed in directions of ±20° to 90°.  
     
     
         24 . A method according to any preceding claim in which a hairy yam is introduced into the plies.