Detection and Assessment of Damage to Composite Structure

Abstract

A system comprising: a parent structure made of composite material and having a repair site; a repair patch made of composite material, the repair patch being bonded to the parent structure at the repair site; and a sensor embedded in the repair patch. The system may further comprise non-volatile memory and an interface unit embedded in the repair patch and electrically connected to the sensor. In one embodiment, the sensor is a loop-shaped sensor comprising an electrically conductive structure having an electrical conductivity that varies as a function of a pressure exerted on the repair patch. In another embodiment, the sensor comprises a sensor chip having nonvolatile memory. In a further embodiment, the sensor comprises an optical fiber that is sensitive to changes in pressure on or strain in the repair patch.

1 . A system comprising:
 a parent structure made of composite material and having a repair site;   a repair patch comprising a multiplicity of plies of repair composite material arranged in a stack, the repair patch being bonded to the parent structure at the repair site; and   a loop-shaped sensor disposed between adjacent plies of the multiplicity of plies, wherein the loop-shaped sensor comprises an electrically conductive structure having an electrical conductivity that varies as a function of a pressure exerted on the repair patch.   
     
     
         2 . The system as recited in  claim 1 , wherein the electrically conductive structure comprises a microelectromechanical system. 
     
     
         3 . The system as recited in  claim 1 , wherein the electrically conductive structure comprises a multiplicity of nanotubes. 
     
     
         4 . The system as recited in  claim 1 , wherein the electrically conductive structure comprises metal foil. 
     
     
         5 . The system as recited in  claim 1 , wherein the loop-shaped sensor further comprises a pair of output terminals electrically coupled to the electrically conductive structure and extending outside the repair patch. 
     
     
         6 . The system as recited in  claim 5 , further comprising measurement equipment electrically coupled to the electrically conductive structure by the output terminal. 
     
     
         7 . The system as recited in  claim 6 , wherein the measurement equipment comprises an ohmmeter. 
     
     
         8 . The system as recited in  claim 1 , wherein the loop-shaped sensor has a shape which is conformed to the shape of the repair patch. 
     
     
         9 . The system as recited in  claim 1 , wherein the repair patch comprises a layer of interwoven wire fabric. 
     
     
         10 . A system comprising:
 a parent structure made of composite material and having a repair site;   a repair patch comprising a multiplicity of plies of repair composite material arranged in a stack, the repair patch being bonded to the parent structure at the repair site; and   a plurality of sensor chips embedded in the repair patch.   
     
     
         11 . The system as recited in  claim 10 , wherein at least some of the multiplicity of sensor chips are positioned in areas where the repair is weakest. 
     
     
         12 . The system as recited in  claim 10 , wherein at least some of the multiplicity of sensor chips are positioned along a peripheral region in which the repair patch overlies the parent structure. 
     
     
         13 . The system as recited in  claim 10 , wherein the multiplicity of sensor chips are embedded in the repair patch with proper grounding and protection to avoid high-intensity radiated field damage effects. 
     
     
         14 . The system as recited in  claim 10 , wherein each sensor chip comprises a sensor, non-volatile memory electrically connected to the sensor for local data storage, and an interface unit electrically connected to the sensor for wireless or wired data acquisition. 
     
     
         15 . The system as recited in  claim 14 , wherein the sensor in each sensor chip comprises a microelectromechanical system. 
     
     
         16 . The system as recited in  claim 14 , wherein the sensor in each sensor chip comprises a multiplicity of nanotubes. 
     
     
         17 . The system as recited in  claim 14 , wherein the electrically conductive structure comprises metal foil. 
     
     
         18 . The system as recited in  claim 14 , further comprising a remote data concentrator configured to receive data from the interface unit. 
     
     
         19 . The system as recited in  claim 10 , wherein the repair patch comprises a layer of interwoven wire fabric. 
     
     
         20 . A system comprising:
 a parent structure made of composite material and having a repair site;   a repair patch comprising a multiplicity of plies of repair composite material arranged in a stack, the repair patch being bonded to the parent structure at the repair site; and   an optical fiber disposed between adjacent plies of the multiplicity of plies, wherein the optical fiber is sensitive to changes in pressure on or strain in the repair patch.