No abstract

This project demonstrated the implementation of embedded optical fibers as sensors for detecting the onset of shell buckling instabilities and compressive failure in composite cylinders. In the present work, five 6-inch diameter cylinders (four filament-wound and one prepreg tape) with integrated optical fiber strain sensors were fabricated and tested in compression. The cylinders were instrumented with an axial strain gage for local strain measurements and a helically-wound 633-nm optical fiber for integrated strain measurement. The integrated strains along the optical fiber path were obtained by using a modified Mach-Zehnder interferometer with feedback electronics controlling PZT's in the reference arm. This distributed sensing technique provides a more reliable and sensitive means of detecting critical strains and the onset of pre-buckling deformations than the conventional local strain gage.