IN-SITU FIBER OPTIC SENSOR FOR FTIR MONITORING OF COMPOSITE CURE CYCLES

FOURIER TRANSFORM INFRARED SPECTROSCOPY (FTIR) DEMONSTRATED IN THE LABORATORY IS A VALUABLE TECHNIQUE FOR MONITORING THE CURE CYCLE IN ADVANCED THERMOSETTING COMPOSITE MATERIALS. NEW INFRARED TRANSMITTING OPTICAL FIBERS TOGETHER WITH RECENTLY DEVELOPED RUGGEDIZED FTIR INSTRUMENTS OFFER THE PROMISE THAT THIS LABORATORY TECHNOLOGY CAN BE MOVED INTO A PRODUCTION ENVIRONMENT TO PROVIDE AN IN-SITU, NON-DESTRUCTIVE EVALUATION TECHNIQUE TO DETERMINE THE STATE OF CURE IN THERMOSET COMPOSITES IN REAL TIME. THIS PROGRAM INTENDS TO DEMONSTRATE THE FEASIBILITY OF SENSING AND TRANSMITTING AN IR SPECTRUM EQUIVALENT TO THOSE OBTAINED BY YOUNG ET AL. AT NASA LANGLEY IN THE CURING CYCLE OF A TYPICAL THERMOSETTING RESIN USING AN OPTICAL FIBER SENSOR TRANSMITTING LINK AND A RUGGEDIZED FTIR ANALYZER. THE FIBERS USED WILL BE OF A CHALCOGENIDE GLASS CAPABLE OF TRANSMITTING IN THE MID-IR WAVELENGTHS THAT WILL DUPLICATE THE SPECTRAL BANDS ANALYZED BY YOUNG. BECAUSE OF THE RELATIVELY HIGHER ATTENUATION OF LIGHT IN THE CHALCOGENIDE GLASSES, AN ALTERNATIVE APPROACH WOULD BE TO USE NEAR-IR SPECTRAL INFORMATION IN THE 1 TO 5 UM REGION USING VERY LOW ATTENUATION HEAVY METAL FLUORIDE GLASS FIBERS AND FTIR-CORRELATION TECHNIQUES. THE PHASE I PROGRAM WILL CONCLUSIVELY DEMONSTRATE WHETHER IR TRANSMITTING OPTICAL FIBERS ARE TECHNICALLY AND ECONOMICALLY FEASIBLE TO PROVIDE IN-SITU MEASUREMENTS OF STATE OF CURE IN A THERMOSET COMPOSITE MATERIAL.