Time domain reflectometry (TDR) offers the advantage of distributed sensing using a single transmission line sensor. In the present study, a parallel plate type non-invasive TDR sensor for structural health monitoring (SHM) of composite has been designed, modeled and experimentally tested. Five layer unidirectional glass fiber/epoxy composite specimens are fabricated. Specimens included a damage initiator in form of a cut in the central ply. The TDR sensor detects sub-surface damage in the composite non-invasively as the effective dielectric constant of the composite decreases due to the presence of delamination cracks. Previous work done on dielectrostriction is used to model the TDR response to strain changes. Qualitative agreement between theory and experimental results for strain sensing are found.
Erik T. Thostenson,
"Electric Time Domain Reflectometry Sensors for Non-Invasive Structural Health Monitoring of Glass Fiber Composites," Progress In Electromagnetics Research,
Vol. 137, 551-564, 2013. doi:10.2528/PIER13020611
2. Rao, Y. J., "Recent progress in applications of in-fibre Bragg grating sensors," Optics and Lasers in Engineering, Vol. 31, 297-324, 1999. doi:10.1016/S0143-8166(99)00025-1
3. Ling, H., K. Lau, L. Cheng, and W. Jin, "Viability of using an embedded FBG sensor in a composite structure for dynamic strain measurement," Measurement, Vol. 39, 328-334, 2006. doi:10.1016/j.measurement.2005.11.011
4. Barre, S. and M. L. Benzeggagh, "On the use of acoustic emission to investigate damage mechanisms in glass-fibre-reinforced polypropylene," Composites Sci. Technol., Vol. 52, 369-376, 1994. doi:10.1016/0266-3538(94)90171-6
5. Grosse, C. U. and M. Ohtsu, Acoustic Emission Testing, Springer Verlag, Berlin, 2008.
6. Cantwell, W. J. and J. Morton, "Detection of impact damage in CFRP laminates," Composite Structures,, Vol. 3, No. 241, 1985.
7. Aymerich, F. and S. Meili, "Ultrasonic evaluation of matrix damage in impacted composite laminates," Composites Part B: Engineering, Vol. 31, 1-6, 2000. doi:10.1016/S1359-8368(99)00067-0
8. Valleau, A., "Eddy-current nondestructive testing of graphite composite-materials," Mater. Eval., Vol. 48, 230-239, 1990.
9. Mook, G., R. Lange, and O. Koeser, "Non-destructive characterisation of carbon-fibre-reinforced plastics by means of eddy-currents," Composites Sci. Technol., Vol. 61, 865-873, 2001. doi:10.1016/S0266-3538(00)00164-0
10. Smolyansky, D. and S. Corey, "PCB interconnect characterization from TDR measurements," Electronic Engineering, Vol. 71, 63, 1999.
11. O'Connor, K. M. and C. M. Dowding, Geomeasurements by Pulsing TDR Cables and Probes, CRC Press, Boca Raton, 1999.
12. Lin, M. and J. Thaduri, "Structural damage detection using an embedded ETDR distributed strain sensor," Sensing and Imaging: An International Journal, Vol. 6, 315-336, 2005.
13. Chen, G., H. Mu, D. Pommerenke, and J. L. Drewniak, "Damage detection of reinforced concrete beams with novel distributed crack/strain sensors," Structural Health Monitoring, Vol. 3, 225-243, 2004. doi:10.1177/1475921704045625
14. Cataldo, A., G. Cannazza, E. De Benedetto, and N. Giaquinto, "Experimental validation of a TDR-based system for measuring leak distances in buried metal pipes," Progress In Electromagnetics Research, Vol. 132, 71-90, 2012.
15. Dominauskas, A., D. Heider, and J. W. Gillespie, Jr., "Electric time-domain reflectometry distributed flow sensor," Composites Part A: Applied Science and Manufacturing, Vol. 38, 138, 2007. doi:10.1016/j.compositesa.2006.01.019
16. Pandey, G., H. Deffor, E. T. Thostenson, and D. Heider, "Smart tooling with integrated time domain reflectometry sensing line for non-invasive flow and cure monitoring during composites manufacturing," Composites Part A: Applied Science and Manufacturing, Vol. 47, 102-108, 2013. doi:10.1016/j.compositesa.2012.11.017
17. Obaid, A. A., S. Yarlagadda, M. K. Yoon, N. E. Hager, and R. C. Domszy, "A time-domain reflectometry method for automated measurement of crack propagation in composites during mode I DCB testing," Journal of Composite Materials, Vol. 40, 2047-2466, 2006. doi:10.1177/0021998306061309
18. Pandey, G. and E. T. Thostenson, "Carbon nanotube-based multifunctional polymer nanocomposites," Polymer Reviews, Vol. 52, 355-416, 2012. doi:10.1080/15583724.2012.703747
19. Pandey, G., M. Wolters, E. T. Thostenson, and D. Heider, "Localized functionally modified glass fibers with carbon nanotube networks for crack sensing in composites using time domain reflectometry," Carbon, Vol. 50, 3816-3825, 2012. doi:10.1016/j.carbon.2012.04.008
20. Shivakumar, K. and L. Emmanwori, "Mechanics of failure of composite laminates with an embedded fiber optic sensor," Journal of Composite Materials, Vol. 38, 669-680, 2004. doi:10.1177/0021998304042393
21. Shivakumar, K. and A. Bhargava, "Failure mechanics of a composite laminate embedded with a fiber optic sensor," Journal of Composite Materials, Vol. 39, 777-798, 2005. doi:10.1177/0021998305048156
22. Lee, H. Y. and Y. M. Shkel, "Dielectric response of solids for contactless detection of stresses and strains," Sensors and Actuators A: Physical, Vol. 137, 287, 2007. doi:10.1016/j.sna.2007.03.029
23. Lee, H. Y., Y. Peng, and Y. M. Shkel, "Strain-dielectric response of dielectrics as foundation for electrostriction stresses," Journal of Applied Physics, Vol. 98, No. 7, 2005.
24. Brandao Faria, J. A. B., Electromagnetic Foundations of Electrical Engineering, Wiley, Chichester, UK, 2008.