Characterization of Fiber Optic Sensors for Structural Health Monitoring

Abstract

This paper presents experimental results on thermomechanical behavior of Extrinsic Fabry-Perot Interferometric fiber optic strain sensors (EFPI-FOSS). The objective of this study was to determine the accuracy, strength characteristics, and durability properties of both bare (nonembedded) EFPI sensors, and embedded optical fiber sensors in either a neat resin or aerospace grade composite laminate. Experimental results suggest that the embedded EFPI sensors provide reliable strain measurements for values exceeding 10,000 μ∊ under static loading conditions. A major portion of this study focused on evaluating the long term tension–tension fatigue behavior of optical fiber sensors. Test data suggest the EFPI sensors provide reliable data up to 1 million cycles at fatigue strain levels below 3,000 μ∊. For fatigue strain levels above this value, failure of the fiber optic sensor was observed. While the sensor failed it did not influence the strength and fatigue life of the composite coupons. Considering the design strains used in aerospace components, these results provide evidence that the EFPI sensors will survive during the life of typical aerospace structures.

Keywords

EFPI fiber optic strain sensor fatigue composites

Get full access to this article

View all access options for this article.

References

Brown, T. et al. (1999). Fiber optic sensors for health monitoring of morphing aircraft. SPIE 6th Annual International Symposium on Smart Structures and Materials.

Carman, G.P. and Sendeckyj, G.P. (1995). Review of the mechanics of embedded optical sensors. Journal of Composites Technology and Research, 17(3): 183–193.

Foote, P.D. (1999). Structural health monitoring: tales from Europe. In: Proceedings of the 2nd International Workshop on Structural Health Monitoring. pp. 24–35.

Friebele, E.J. et al. (1999). Optical fiber sensors for spacecraft applications. Smart Material and Structure, 8: 813–838.

Hahn, H.T., Bartley-Cho, J. and Lim, S.G. (1996). The effect of loading parameters on fatigue of composite laminates: part II. DOT/FAA/AR-96/76.

Kang, H.K. et al. (2000). Development of fiber optic ingress/egress methods for smart composite structures. Smart Material and Structure, 9: 149–156.

Kim, K.S. and Paik, S.H. (1997). Optical fiber monitoring system of bridges in Korea. In: Proceedings of the International Workshop on Structural Health Monitoring. pp. 555–563.

Lee, D.C. , Lee, J.J. and Yun, S.J. (1995). The mechanical characteristics of smart composite structures with embedded optical fiber sensors. Composite Structures, 32: 39–50.

Melvin, L. et al. (1997). Integrated vehicle health monitoring (IVHM) for aerospace vehicles. In: Proceedings of the International Workshop on Structural Health Monitoring. pp. 705–713.

10.

Mita, A. (1999). Emerging needs in Japan for health monitoring technologies in civil and building structures. In: Proceedings of the 2nd International Workshop on Structural Health Monitoring. pp. 56–67.

11.

Mitrovic, M. and Carman, G.P. (1994). Monitoring the fatigue behavior of composite materials with fiber optic sensors. 39th International SAMPE Symposium. pp. 3078–3089.

12.

Poland, Steve. (2000). Luna Innovations, personal discussion.

13.

Shi, Y. et al. (1998). Ingress/egress technology development for fiber-optic smart structures. Phase I Technical Report, Department of Mechanical Engineering, University of Maryland.

14.

Shyprykevich, et al. (1993). Performance of extrinsic fabry-petrot optical fiber strain sensors in the presence of cyclic loads. SPIE Smart Sensing, Processing, and Instrumentation, 1918: 388–399.

15.

Skontorp, A. (1998). Structural integrity of quasi-isotropic composite laminates with embedded optical fibers. In: Proceedings of the 13th Annual Technical Conference on Composite Materials.

16.

Todd, M. et al. (1999). Civil infrastructure monitoring with fiber bragg grating sensor arrays. In: Proceedings of the 2nd International Workshop on Structural Health Monitoring. pp. 359–368.

17.

Wood, K. et al. (2000). Fiber optic sensors for health monitoring of morphing airframes: I. bragg grating strain and temperature sensor. Smart Material and Structures, 9: 163–169.