Toughened, crack resistant fiber reinforced composite article and method for making

Abstract

A composite article, for example a blading member of a gas turbine engine, comprising a plurality of stacked layers of reinforcing fibers bonded together with a matrix resin is provided with enhanced resistance to impact cracking, material loss and/or delamination though use of a matrix resin including properties comprising a tensile strain property of at least 5% and a K 1c toughness of at least about 850 psi·inch 1/2 . A method for making such a composite article with such resin comprises providing the layers of reinforcing fibers in a substantially dry, unimpregnated condition. The dry layers are stacked as a preform in a mold cavity and impregnated with the resin to wet and impregnate the dry layers of the preform. Then the resin is cured as a matrix about the fibers and the stacked layers.

What is claimed is:  
     
         1 . A composite article comprising a plurality of stacked layers of reinforcing fibers, the layers bonded together with a matrix resin, wherein: 
 the matrix resin includes properties comprising a tensile strain property of greater than 5% and a K 1c  toughness of at least about 850 psi·inch 1/2 .    
     
     
         2 . The article of  claim 1  in which the reinforcing fibers in a stacked layer are substantially aligned with one another.  
     
     
         3 . The article of  claim 2  in which: 
 each of the stacked layers predominantly includes substantially aligned reinforcing fibers; and,  
 the matrix resin is an injectable epoxy resin.  
 
     
     
         4 . The article of  claim 3  in which the fibers comprise at least one selected from the group consisting of carbon, graphite, glass, and boron fibers.  
     
     
         5 . The article of  claim 1  in the form of a turbine engine blading member including an airfoil in which at least the airfoil comprises a plurality of shaped, stacked layers of reinforcing fibers impregnated and bonded together with the matrix resin.  
     
     
         6 . The blading member of  claim 5  in which the reinforcing fibers in a stacked layer are substantially aligned with one another.  
     
     
         7 . The article of  claim 5  in which: 
 the fibers comprise at least one selected form the group consisting of carbon, graphite, glass, and boron fibers; and,  
 the resin is an injectable epoxy resin.  
 
     
     
         8 . A method for making a composite article comprising a plurality of stacked layers of reinforcing fibers bonded together with a matrix resin comprising the steps of: 
 providing a plurality of layers of substantially dry, unimpregnated reinforcing fibers,    stacking the layers one upon another into a preform shape; and,    impregnating the preform shape with a resin that includes properties comprising a tensile capacity of greater than 5% and a K 1c  toughness of at least about 850 psi·inch 1/2 .    
     
     
         9 . The method of  claim 8  in which the reinforcing fibers in a stacked layer substantially are aligned with one another.  
     
     
         10 . The method of  claim 8  in which: 
 the layers of the preform shape are stacked in a cavity of a mold;  
 the mold cavity is closed;  
 a vacuum is provided within the mold cavity about the layers of the preform shape;  
 the matrix resin is provided in the cavity about the fibers and the layers to wet and impregnate the layers and fibers; and,  
 the resin is cured about the fibers and layers.  
 
     
     
         11 . The method of  claim 10  in which: 
 the resin is an injectable epoxy;  
 after providing the vacuum in the mold cavity, the resin is injected into the mold cavity under a pressure in the range of about 25-100 psi; and,  
 the resin is cured at a temperature in the range of about 350-400° F.