Entire Life Time Monitoring of Filament Wound Composite Cylinders Using Bragg Grating Sensors: III. In-Service External Pressure Loading
This article is the third of three papers describing a study of the monitoring of filament wound composite cylinders for underwater applications. Part I described the technological issues and the development of specimens instrumented with embedded gratings and thermocouples, with the aim of monitoring the temperature and strain changes during the cylinder manufacturing presented in Part II. Residual strains are not negligible, over 1,000 axial micro-strain at the end of the curing cycle. Part III describes the response of these cylinders to hydrostatic pressure loading. The same embedded fiber optical Bragg gratings (FBGs) used for parts I and II of the study are here used as strain gauges. Their response is compared to that of classical resistive strain gages bonded to the inner surface of the tube. Results from these initial tests demonstrate the embedded FBG sensor’s capability to monitor structural health of an underwater structure from fabrication throughout its service life. Embedded instrumentation records strains during pressure cycles up to final failure, without affecting the cylinder response.
KeywordsPolymer-matrix composites (PMCs) Smart materials Residual stress Filament winding Underwater application
H. Hernández Moreno wishes to thank the National Council of Science and Technology of Mexico (CONACYT) and the National Polytechnic Institute of Mexico (IPN) for their scholarship sponsoring. The authors thank I. Fernandez Hernandez, J. Bauw, F. Afonso, and E. Vargas Rojas for their collaboration during their internship at LGMT. Also thanks to M. Mulle at LGMT, for his collaboration during the instrumented implosion test, and to IFREMER for financial and technical support, with special thanks to P. Warnier and A. Duff.
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