@article{propst_peters_zikry_schultz_kunzler_zhu_wirthlin_selfridge_2010, title={Assessment of damage in composite laminates through dynamic, full-spectral interrogation of fiber Bragg grating sensors}, volume={19}, ISSN={["0964-1726"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-74849118513&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/19/1/015016}, abstractNote={In this study, we demonstrate the full-spectral interrogation of a fiber Bragg grating (FBG) sensor at 535 Hz. The sensor is embedded in a woven, graphite fiber–epoxy composite laminate subjected to multiple low-velocity impacts. The measurement of unique, time dependent spectral features from the FBG sensor permits classification of the laminate lifetime into five regimes. These damage regimes compare well with previous analysis of the same material system using combined global and local FBG sensor information. Observed transient spectral features include peak splitting, wide spectral broadening and a strong single peak at the end of the impact event. Such features could not be measured through peak wavelength interrogation of the FBG sensor. Cross-correlation of the measured spectra with the original embedded FBG spectrum permitted rapid visualization of average strains and the presence of transverse compressive strain on the optical fiber, but smeared out the details of the spectral profile.}, number={1}, journal={SMART MATERIALS AND STRUCTURES}, author={Propst, A. and Peters, K. and Zikry, M. A. and Schultz, S. and Kunzler, W. and Zhu, Z. and Wirthlin, M. and Selfridge, R.}, year={2010}, month={Jan} }
 @article{schultz_kunzler_zhu_wirthlin_selfridge_propst_zikry_peters_2009, title={Full-spectrum interrogation of fiber Bragg grating sensors for dynamic measurements in composite laminates}, volume={18}, ISSN={["1361-665X"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-70350668824&partnerID=MN8TOARS}, DOI={10.1088/0964-1726/18/11/115015}, abstractNote={This paper presents a new means for collecting fiber Bragg grating (FBG) data during drop-tower measurements used to assess damage to composite structures. The high repetition-rate collection process reveals transient features that cannot be resolved in quasi-static measurements. The experiments made at a repetition rate of about 500 Hz show that the detected FBG spectrum broadens for a short period of time and relaxes quickly to a narrower static state. Furthermore, this relaxation time increases dramatically as the strike count increases. The information gained by such measurements will enhance the ability to characterize and distinguish failure modes and predict the remaining lifetime in composite laminate structures.}, number={11}, journal={SMART MATERIALS AND STRUCTURES}, author={Schultz, S. and Kunzler, W. and Zhu, Z. and Wirthlin, M. and Selfridge, R. and Propst, A. and Zikry, M. and Peters, K.}, year={2009}, month={Nov} }
 @inproceedings{propst_garrett_park_peters_zikry_2009, title={Sensor networks for in-situ failure identification in woven composites}, volume={7293}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-66749128673&partnerID=MN8TOARS}, DOI={10.1117/12.815743}, abstractNote={This paper presents experimental measurements of the response of woven composite laminates to multiple low-velocity impacts. Damage initiation and progression occur at multiple physical and temporal scales in heterogeneous materials, including fiber breakage, matrix cracking, delamination and matrix relaxation. The sensor/interrogators were therefore chosen specifically to provide insight into the order and progression of different failure modes. Measurements of the contact force between the impactor and composite are measured throughout impact. Additionally, the dissipated energy per impact event is also calculated from the impactor velocity. Surface mounted and embedded fiber Bragg grating sensors are used for the measurement of the laminate response. Peak wavelength measurements are performed during impact at 1 kHz, while full-spectral scanning is performed at 5 Hz during relaxation period of the laminate immediately after impact and quasi-statically to measure post-impact residual strain states within the laminate. The results highlight the depth of information embedded within the FBG full-spectral data sensors, as well as the added insight to be gained from combined global-local measurements.}, booktitle={SMASIS 2009, vol 2}, author={Propst, A. and Garrett, R. and Park, C. and Peters, K. and Zikry, M.}, year={2009}, pages={477–485} }