Mechanoluminescence (ML) is a property of inorganic and organic materials that describes the emission of light due from the application of force. Inorganic crystals (mostly phosphors) and certain organic macromolecules exhibit elastico-ML and are a natural fit for structural health monitoring (SHM) of composite structures. Composites with particulate ML crystals enable the visualization of stress distribution over a plane and over contoured surfaces in a spatially continuous manner. Imaging ML composites with affordable high-resolution imaging methods further enables the creation of high-resolution validation method for computational methods. Also, with the embedding of suitable photo-detectors for signal detection, the need for additional wiring, sensor electronics and high-level electronics is eliminated. In this conference proceedings technical publication, the application of commercially available ZnS:Cu, Mn phosphors for SHM of polymer composites will be presented via experimental and structural simulation. Results demonstrate the dependence of intensity of elastico-ML (in cd/cm2) on strain rate, strain and composition (w/w of ML particulates). The experiments show methods to fabricate elastic coupons of phosphors in polydimethylsiloxane (PDMS) and subsequent methods for application in SHM. The structures are excited at 5Hz to 17.5Hz to develop empirical relationships between strain rate and EML intensity and it is shown that the intensity increases nonlinearly with the magnitude of stress/strain rate. A range of stresses transferred to the EML particles by the PDMS matrix is also numerically predicted. The numerical simulations show the importance of interfacial binding in the transfer of stress and subsequent EML emission. These results also provided a basis for validation and improvement of structural simulation models.
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Characterization of Mechanoluminescent Composites and Their Applications for SHM of Polymer Composites
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Krishnan, S, Vijayaraghavan, P, & Sundaresan, V. "Characterization of Mechanoluminescent Composites and Their Applications for SHM of Polymer Composites." Proceedings of the ASME 2015 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. Volume 2: Integrated System Design and Implementation; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting. Colorado Springs, Colorado, USA. September 21–23, 2015. V002T05A012. ASME. https://doi.org/10.1115/SMASIS2015-9078
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