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Mentor: Seetha Raghavan

Description: Reusability needs of hypersonic and advanced launch structures are accompanied by an increased use of high-temperature superalloys and ceramic matrix composites (CMCs) in combination with thermal and/or environmental coatings for their ability to operate under critical and severe thermal and mechanical environments. The durability of these coatings has been linked to the evolution of stresses within them over cyclic thermal and mechanical loads that the structures experience. Piezospectroscopy is a technique, using laser excitation, that allows the determination of stress in these materials through the monitoring of emitted peak shifts from a reference condition.

Using samples at various stages of cycling, students will use piezospectroscopy to collect and correlate spectral data to coating life. The module allows students to understand concepts in coating stress distribution, optical techniques for stress measurement and analysis of spectral peaks via optimization. They will also use a spectroscopy system coupled with an electromechanical test frame. Before this takes place, the REU student will be trained to use the devices. The student will help prepare publications.

Both non-contact methods of piezospectroscopy and digital image correlation applied to an aerospace structure sample (left) to detect the onset of damage as tensile loads are applied (right).