NON-DESTRUCTIVE TESTING USING A FIBER OPTIC SENSORY SYSTEM

THIS RESEARCH PROPOSAL SEEKS TO DEVELOP A FIBER OPTIC SENSOR THAT WILLCONTINUOUSLY MONITOR THE LOCAL STATE OF STRESS/STRAIN INTERNAL TO FIBER REINFORCED COMPOSITE MATERIALS. THE SENSOR WILL CONSIST OF A SINGLE OPTICAL FIBER AND WILL BE AN INTEGRAL COMPONENT OF THE COMPOSITE MATERIAL. THE PROPOSED TECHNIQUE UTILIZES TIME RESOLVED LIGHT BACKSCATTERING WITHIN THE FIBER CORE THAT RESULTS FROM A MATERIAL-INDUCED LOCAL STRAINING OF THE OPTICAL FIBER. MAJOR GOALS OF THE PROGRAM INCLUDE THE DEVELOPMENT OF SENSITIZED FIBER SEGMENTS THAT WILL RESPOND TO INTERNAL STRESSES ACTING ON THE FIBER SURFACE, A DEFINITION OF THE SENSOR SYSTEM CHARACTERISTICS, AND A DETERMINATIONOF THE SENSOR-COMPOSITE MATERIAL COMPATIBILITY. IT IS PROJECTED THAT THE SINGLE FIBER SENSOR WILL HAVE A SPATIAL RESOLUTION OF 3.0 CM, MINIMUM DETECTABLE STRESS LEVELS OF APPROXIMATELY 40 PSI, AND AN ESSENTIALLY CONTINUOUS REAL TIME INTERROGATION CAPABILITY. A FIBER OPTIC NERVOUS SYSTEM CAPABLE OF MONITORING THE INTERNAL STATE OF STRESS IN STRUCTURAL MATERIALS WILL PERMIT THE OPTIMAL UTILIZATION OF THE MATERIAL AND STRUCTURE. FOR EXAMPLE, A STRESS SENSOR INTERNAL TO AN AIRCRAFT WING COULD ALLOW THE PILOT TO HAVE CONTINUOUS KNOWLEDGE OF THE LOCAL STRESSES IN THE WING AND ALLOW HIM TO OPERATE HIS AIRCRAFT TO ITS MAXIMUM EFFICIENCY. THIS SENSOR WOULD HAVE WIDE SCALE APPLICATIONS IN ANY SYSTEM SUBJECTED TO SEVERE STRESSES WHERE THE SYSTEM PERFORMANCE IS DEPENDENT UPON THE OPTIMAL USE OF THE STRUCTURE'S MATERIAL STRENGTH.