ULTRASONIC NONDESTRUCTIVE TECHNIQUES AND INSTRUMENTATION FORTRANSPARENT ENCLOSURES OF HIGH PERFORM A/C

AIRCRAFT TRANSPARENCIES REPRESENT ONE OF THE MOST SIGNIFICANT LIFE CYCLE COST TO THE U.S. AIR FORCE. THE MAJOR CAUSE FOR THE OPTICAL IMPAIRMENT IS THE DEGRADATION IN PLASTICS KNOWN AS CRAZING WHICH OCCURS DUE TO SURFACE STRESSES AND IS ACCELERATED BY THE ENVIRONMENTALFACTORS. THE OBJECTIVE OF THE PROJECT IS TO DEVELOP THE NECESSARY TECHNIQUE TO MEASURE AND QUANTIFY THE CRAZING AND SHOW FEASIBILITY OF A PORTABLE INSTRUMENT TO CARRY OUT THE EVALUATION IN FIELD. SUCH A CAPABILITY AFFORDS USAF TO VALIDATE ACCELERATED CRAZING TESTS, ENABLE PURCHASE OF THE CANOPIES BASED ON LIFE CYCLE COST, OVERALL REDUCE COST AND INCREASE COMBAT READINESS. THE PRUDENT APPROACH IS WELL RESEARCHED SURFACE ACOUSTIC WAVE TECHNIQUES WHICH HAVE BEEN SUCCESSFUL IN LOCATING MINUTE CRACKS IN METALS AND CERAMICS. THE MOST IMPORTANT FACTOR IN CHOICE OF ACOUSTIC TECHNIQUE IS THEIR ABILITY TO MEASURE THE RESIDUAL STRESSES WHICH DETERMINE THE REMAINING LIFE OF OPTICAL PERFORMANCE. WE ANTICIPATE AN ELEGANT MEASUREMENT SCHEME THAT CAN CHARACTERIZE THE EXISTING CRAZES AND INDICATE THE PROBABLE TIME OF FUTURE OCCURENCE.