The development and performance evaluation of new carbon/carbon (C/C) and carbon/silicon-carbide (SiC) composite structural components has been hampered by the lack of reliable strain sensors that can survive up to the exceedingly high temperatures (3000 F) up to which these materials must be tested. Existing off-the-shelf high-temperature strain sensors, including free filament electrical strain gages and optical fiber based strain sensors, currently do not have the necessary performance characteristics to tackle the next generation of C/C and SiC composite material testing programs. Free filament electrical strain gages cannot be used reliably over 1800 F (1000 C) and conventional optical fiber strain sensors with the appropriate protective metal coatings can operate reliably only up to close to the melting point of the silica (2000 F/1100 C). To meet the growing needs for strain sensors that can withstand future high temperature testing regimes, Lambda Instruments, Inc. proposes to develop sapphire optical fiber sensors. The 3600 F (1987 C) melting temperature of optical quality sapphire fibers, their low profile geometry, and the inherent immunity of optical fiber sensors to electromagnetic interference make sapphire fiber-based sensors particularly well suited for the proposed application.
Potential NASA Commercial Applications: (LIMIT 150 WORDS) The primary NASA application for the proposed high temperature sapphire optical fiber strain gages is for structural performance monitoring of emrging C/SiC and C/C composite components that must be characterized up to 3000 F. Other potential NASA applications based on the proposed sapphire optical fiber sensor technology include strain, temperature, and pressure sensors for performance monitoring of ramjet/scramjets during research and operation as well as for continuous structural health monitoring of the next generation space vehicles to maintain performance and safety standards throughout all phases of the mission.
Potential NON-NASA Commercial Applications: (LIMIT 150 WORDS) In addition to NASA applications for high temperature sapphire optical fiber sensors for C/C and SiC structural performance evaluation, Lambda foresees significant commercial market possibilities for such devices in hazardous manufacturing processes such as steel mills, chemical plants and other manufacturing facilities where high temperature materials testing and processing is necessary. In addition, the proposed sensors would easily be adaptable for commercial turbomachinery testing and operation control and monitoring systems. If the sensors can be fabricated inexpensively, a large market exists in automotive markets for internal monitoring of internal combustion engines.
