A technique for the measurement of elastic moduli in thermo-vacuum environment

This work describes the design and validation of an elastic moduli measurement method developed to characterize optical materials in cryogenic environment. The testing procedure is based on the identification of the natural frequencies of a specimen at the temperatures of interest so that from the changes in the natural frequencies the material elastic properties changes are derived. The difference with respect to other conceptually similar methods is that material samples are excited by piezoelectric actuators, and identical elements are used as sensors to detect the temperature-dependent resonance frequencies. Given the low cost, mass and size of the adopted piezoelectric elements, the proposed method allows multiple samples parallel testing even in small vacuum chambers, reducing the time and economical efforts for experimental characterization. The method has been initially validated by testing an Al 6060 alloy sample, a widely used material in space applications for which reference data in a wide temperature range are available. Compatibility of measured values and literature data in the range of temperature -120 to 60 °C was obtained. A first application of the method for the characterization of a potassium bromide sample is eventually presented.