Detection and Assessment of Damage to Composite Structure

Abstract

A method for monitoring structural integrity of a repaired aircraft component made of composite material. The method comprises: (a) placing a multiplicity of plies of repair composite material over a repair site on the component with a sensor disposed between two plies; (b) curing the plies of repair composite material so that the repair composite material, with the sensor embedded therein, is bonded to the repair site; (c) acquiring first sensor data from the sensor before a flight of the aircraft; (d) acquiring second sensor data from the sensor during or after the flight; (e) comparing the first sensor data to the second sensor data; (f) identifying differences between the first and second sensor data indicative of structural change; and (g) determining whether the identified differences indicate structural change in excess of a specified threshold. Steps (c) through (g) are performed by a computer system.

1 . A method for monitoring structural integrity of a laminated structure made of composite material, said method comprising:
 (a) placing a sensor between plies of composite material which are not fully cured, the sensor being capable of outputting data representing a current structural characteristic of surrounding composite material after the composite material has been cured;   (b) curing the plies of composite material while the sensor is in place to produce composite material having an embedded sensor;   (c) after the curing step, acquiring and recording baseline data from the embedded sensor which represents a structural characteristic of the surrounding composite material;   (d) after the baseline data has been acquired and recorded, subjecting the laminated structure to loads having unknown magnitudes and directions;   (e) acquiring and recording post-loading data from the embedded sensor at a time subsequent to or during step (d), said post-loading data representing a structural characteristic of the surrounding composite material;   (f) processing the baseline data and post-loading data in a manner that identifies differences between the respective baseline and post-loading data indicative of structural change in the surrounding composite material; and   (g) determining whether the identified differences indicate structural change to the surrounding composite material in excess of a specified threshold,   wherein steps (e) through (g) are performed by a computer system.   
     
     
         2 . The method as recited in  claim 1 , wherein step (f) comprises creating a baseline signature based on said baseline sensor data, creating a post-loading signature based on said post-loading sensor data, and comparing said baseline and post-loading signatures. 
     
     
         3 . The method as recited in  claim 1 , further comprising issuing an alert signal in response to a determination in step (g) that the identified differences indicate structural change to the surrounding composite material in excess of a specified threshold. 
     
     
         4 . The method as recited in  claim 1 , further comprising processing the post-loading data to compensate for effects due to differences in local conditions at or about the times when steps (c) and (e) were performed. 
     
     
         5 . The method as recited in  claim 1 , wherein curing the plies comprises:
 applying the plies to be cured as a repair patch to a portion of a parent structure to be repaired; and   curing the applied plies to bond the plies to the parent structure.   
     
     
         6 . The method as recited in  claim 5 , further comprising:
 evaluating a current repair dispatch status of the repair based on the results of steps (e) through (g); and   specifying an updated maintenance schedule that takes into account the current repair dispatch status.   
     
     
         7 . The method as recited in  claim 1 , wherein steps (a) through (g) are performed for each of a plurality of repairs, and the output from respective sensors comprises respective post-loading data for respective repairs and respective sensor identification data for respective sensors. 
     
     
         8 . The method as recited in  claim 1 , wherein the laminated structure is part of an aircraft and is subjected to loads in step (d) during flight of the aircraft, said method further comprising communicating the post-loading data from the sensor to a computer system onboard the aircraft, wherein steps (e) through (g) are performed while the aircraft is airborne. 
     
     
         9 . The method as recited in  claim 8 , further comprising communicating the post-loading data from the sensor to a computer system on the ground after the aircraft has landed, wherein steps (e) through (g) are performed on the ground. 
     
     
         10 . A system comprising:
 a parent structure made of composite material and having a repair site;   a repair patch made of composite material, said repair patch being bonded to said parent structure at said repair site; and   a sensor embedded in said repair patch.   
     
     
         11 . The system as recited in  claim 10 , further comprising non-volatile memory embedded in said repair patch and electrically connected to said sensor. 
     
     
         12 . The system as recited in  claim 10 , further comprising an interface unit embedded in said repair patch and electrically connected to said sensor. 
     
     
         13 . The system as recited in  claim 12 , wherein said interface unit comprises a transceiver. 
     
     
         14 . The system as recited in  claim 10 , further comprising a power supply supported by said parent structure and connected to provide power to said sensor. 
     
     
         15 . A method for monitoring structural integrity of a laminated structure made of composite material, comprising:
 (a) placing a sensor between layers of composite material of a repair patch, the sensor being capable of outputting data representing a current structural characteristic of surrounding composite material after the composite material has been cured;   (b) curing the composite material while the repair patch is in contact with a repair site of a parent structure made of composite material to produce a repaired parent structure having an embedded sensor;   (c) after the curing step, acquiring and recording baseline data from the embedded sensor which represents a structural characteristic of the surrounding composite material;   (d) after the baseline data has been acquired and recorded, subjecting the repaired parent structure to loads having unknown magnitudes and directions;   (e) acquiring and recording post-loading data from the embedded sensor at a time subsequent to or during step (d), said post-loading data representing a structural characteristic of the surrounding composite material;   (f) processing the baseline data and post-loading data in a manner that identifies differences between the respective baseline and post-loading data indicative of structural change in the surrounding composite material; and   (g) determining whether the identified differences indicate structural change to the surrounding composite material in excess of a specified threshold,   wherein steps (e) through (g) are performed by a computer system.   
     
     
         16 . The method as recited in  claim 15 , wherein step (f) comprises creating a baseline signature based on said baseline sensor data, creating a post-loading signature based on said post-loading sensor data, and comparing said baseline and post-loading signatures. 
     
     
         17 . The method as recited in  claim 15 , further comprising:
 evaluating a current repair dispatch status based on the results of steps (e) through (g); and   specifying an updated maintenance schedule that takes into account the current repair dispatch status.   
     
     
         18 . The method as recited in  claim 15 , wherein steps (a) through (g) are performed for each of a plurality of repairs, and the output from respective sensors comprises respective post-loading data for respective repairs and respective sensor identification data for respective sensors. 
     
     
         19 . The method as recited in  claim 15 , wherein the laminated structure is part of an aircraft and is subjected to loads during flight of the aircraft. 
     
     
         20 . The method as recited in  claim 19 , further comprising communicating the post-loading data from the sensor to a computer system onboard the aircraft, wherein steps (e) through (g) are performed while the aircraft is airborne. 
     
     
         21 . A method for monitoring structural integrity of a repaired component of an aircraft, comprising:
 (a) placing a multiplicity of plies of repair composite material over a repair site on the component with a sensor disposed between two plies;   (b) curing the plies of repair composite material so that the repair composite material, with the sensor embedded therein, is bonded to the repair site;   (c) acquiring sensor data from the sensor before and during or after a flight of the aircraft;   (d) creating a first signature based on the sensor data acquired before the flight;   (e) creating a second signature based on the sensor data acquired during or after the flight;   (f) comparing the first and second signatures;   (g) identifying differences between the first and second signatures indicative of structural change in the repaired aircraft component; and   (h) determining whether the identified differences indicate structural change to the repaired aircraft component in excess of a specified threshold,   wherein steps (d) through (h) are performed by a computer system.   
     
     
         22 . The method as recited in  claim 21 , further comprising issuing an alert signal in response to a determination in step (f) that the identified differences indicate structural change to the repaired aircraft component in excess of a specified threshold. 
     
     
         23 . The method as recited in  claim 21 , further comprising processing the sensor data acquired during or after the flight prior to steps (d) through (f) to compensate for effects due to differences in local conditions at or about the times when the sensor data is acquired in steps (c). 
     
     
         24 . A method comprising:
 applying a patch to a portion of a composite structure, the patch including plies of composite material and at least one sensor therebetween;   acquiring baseline data from the sensor which represents a structural characteristic of the patch and a portion of the composite structure proximate the patch;   periodically acquiring data from the sensor; and   analyzing the periodically acquired data and the baseline data to determine an integrity of the patch and the composite structure proximate thereto.