A Heterodyne interferometer for TCLE Measurements

In measuring the thermal coefficient of linear expansion (TCLE) of highly-filled polymers used in solid propellants, measurement discrepancies as high as 80% between independent laboratories on the same sample have been reported. Such large inaccuracies in TCLE value can result in very large errors in structural integrity and service life analyses of various propulsion systems. Clearly better instruments are needed to improve measurement accuracy and new standardized methods must be developed that will produce more consistent results. We propose an innovative use of ultra-high resolution interferometry in the development of an instrument that will be capable of measuring expansions of less than 1 Angstrom. Under the conditions outlined in this proposal, this will lead to the capability of measuring TCLE to within about 0.35 x 10-8 in/(in-¿F) for a 1 cm sample.