A non-intrusive low-profile strain monitoring system using an optical fiber time domain (OFTD) sensor has been developed. The OFTD monitoring system is used to determine the strains of specimens during static tension and fatigue tests. Quasi-isotropic E-Glass/epoxy composite specimens with and without embedded optical time domain fiber sensors were fabricated. The optical fiber (OF) sensors were placed in the mid surface of the composite laminate. Each specimen of the embedded polyimide-coated OF sensor consisted of a 100/140 micrometers core/cladding diameter fiber, which was segmented with two reflective sites. Each reflective site consisted of a physical interruption of the optical fiber achieved by cleaving and realigning the fiber. These reflective sites were spaced 30 cm from each other, defining the length over which strain was measured. The dimensions of the reflector are 1.0 cm length and 1.0 mm diameter. Stainless steel tubes 1.0 mm in diameter were fitted over the fibers at the area where they exited the laminate to connect with the optical processor. These tubes protected the fiber optic (FO) from breaking during fabrication and prevented gripping pressure during testing.

Date Published: 12 July 1993
PDF: 11 pages
Proc. SPIE 1918, Smart Structures and Materials 1993: Smart Sensing, Processing, and Instrumentation, (12 July 1993); doi: 10.1117/12.147995

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