Static and Dynamic Strain Measurement at Ambient and Elevated Temperatures Using an Extrinsic Fabry–Perot Interferometer (EFPI) Optical Strain Sensor

Abstract

Advances in the testing of high temperature materials for aerospace structures and propulsion components requires a thorough characterization of mechanical behavior under combined thermal, mechanical, and acoustic loading. The ability to stably measure static strain in such materials is a historically difficult challenge, especially in applications where an extensometer cannot be used. Recent research in the Aerospace Systems Directorate of the Air Force Research Laboratory is establishing a capability for the reliable measurement of mechanical strain at temperatures up to 650°C (1200°F) on metals and above 870°C (1600°F) on ceramic composite materials. Sensor testing on both coupons and structural components has been demonstrated. Quasi-static strain measurement was achieved without the metallurgical drift or high thermal sensitivity of commercially available resistive strain gages. In addition to static measurements, dynamic strain measurement at moderate strain rates was also achieved, as was static strain measurement in the presence of high level broadband acoustic excitation.