An experimental study was conducted to determine the utility of in-line optical fiber-based extrinsic Fabry-Perot interferometers (EFPIs), in a fatigue environment typical of aircraft structures. Metallic and composite coupons with EFPIs attached to and embedded within were tested in constant amplitude cyclic fatigue at room temperature. An additional composite coupon was tested similarly at an elevated temperature. For the consideration of composite material applications the objectives were to determine the durability of the sensor and its ability to measure strains accurately, even when the EFPI sensor was embedded at an angle with respect to the principal adjacent reinforcing fibers of the composite. For metals, in addition to durability considerations, research was conducted as to how the EFPI sensor may be used to detect crack initiation and growth. The results of the test program have established the excellent durability of the EFPI sensor element for fatigue loading up to 50,000 cycles at R equals 0.1 (tension-tension fatigue) with a maximum strain level of 3,500 microinch/inch, for both attached and embedded sensors, once the optical fiber and sensor survived the composite laminate panel curing process.

Date Published: 12 July 1993
PDF: 12 pages
Proc. SPIE 1918, Smart Structures and Materials 1993: Smart Sensing, Processing, and Instrumentation, (12 July 1993); doi: 10.1117/12.147996

Published in SPIE Proceedings Vol. 1918:
Smart Structures and Materials 1993: Smart Sensing, Processing, and Instrumentation
Richard O. Claus, Editor(s)