Composite structure and method for barely visible impact damage detection

Abstract

A composite structure including a composite body having an outer surface and a detection layer connected to the outer surface, the detection layer being discontinuous and including glass fibers embedded in a matrix material.

What is claimed is: 
     
         1 . A method for detecting barely visible impact damage on a composite body, said composite body comprising an outer surface and a plurality of composite plies, said method comprising:
 connecting to said outer surface a detection layer comprising glass fibers embedded in a matrix material, wherein said detection layer is discontinuous.   
     
     
         2 . The method of  claim 1  wherein said connecting step comprises placing the detection layer over the composite body to form an uncured assembly. 
     
     
         3 . The method of  claim 2  wherein said connecting step comprises exposing said uncured assembly to a vacuum load. 
     
     
         4 . The method of  claim 2  wherein said connecting step comprises co-curing said detection layer with said composite body. 
     
     
         5 . The method of  claim 4  wherein said co-curing said detection layer with said composite body comprises heating said detection layer and said composite body. 
     
     
         6 . The method of  claim 1  wherein said connecting step comprises bonding said detection layer to said composite body with an adhesive. 
     
     
         7 . The method of  claim 6  wherein said adhesive comprises any one of epoxies, silicone adhesives, polyester adhesives, urethane adhesives and acrylic adhesives. 
     
     
         8 . The method of  claim 1  wherein said connecting step comprises connecting a detection layer that comprises at least two plies of glass fiber-reinforced plastic. 
     
     
         9 . The method of  claim 1  wherein said connecting step comprises connecting a detection layer that comprises a plurality of strips, and wherein each strip of said plurality of strips is spaced a distance apart from adjacent strips of said plurality of strips. 
     
     
         10 . The method of  claim 9  wherein said plurality of strips are connected by at least one extension member. 
     
     
         11 . The method of  claim 9  wherein said plurality of strips are substantially equidistantly spaced apart from each other. 
     
     
         12 . The method of  claim 1  wherein said connecting step comprises connecting a detection layer that comprises a first portion, a second portion, and a discontinuity between said first portion and said second portion. 
     
     
         13 . The method of  claim 12  wherein said discontinuity includes a slot in said detection layer. 
     
     
         14 . The method of  claim 13  wherein said composite body includes a first major surface, a second major surface, and an edge between said first major surface and said second major surface, and wherein said slot extends across the edge from said first major surface to said second major surface. 
     
     
         15 . The method of  claim 1  wherein:
 said composite body comprises a longitudinal axis, 
 said detection layer comprises a longitudinal axis, and 
 said connecting step comprises positioning said detection layer relative to said composite body such that said longitudinal axis of said composite body substantially aligns with said longitudinal axis of said detection layer. 
 
     
     
         16 . The method of  claim 1  wherein:
 said composite body comprises a web portion having a proximal end and a distal end, 
 said composite body further comprises a base portion connected to said proximal end of said web portion, and 
 said connecting step comprises connecting said detection layer to said distal end of said web portion. 
 
     
     
         17 . The method of  claim 16  wherein said connecting said detection layer to said distal end of said web portion comprises folding said detection layer over said distal end of said web portion. 
     
     
         18 . The method of  claim 1  further comprising determining the optimal thickness of said detection layer based on at least one of a weight of the detection layer and a weight of the composite body. 
     
     
         19 . The method of  claim 1  further comprising visually inspecting said detection layer and said composite body for indications of impact. 
     
     
         20 . A method for detecting barely visible impact damage on a composite body that defines a web portion having a proximal end and a distal end, said composite body further defining a base portion connected to said proximal end, said method comprising:
 positioning a discontinuous detection layer comprising a plurality of strips along said distal end of said web portion such that each strip of said plurality of strips is spaced substantially equidistant relative to one another, wherein each strip of said plurality of strips comprises glass fibers embedded in a matrix material; and   connecting each strip of said plurality of separate strips to said distal end of said web portion of said composite body.