No 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.

US guided access is a feasible and safe procedure that can aid in accessing vascular conduits in patients with CLI. Applying this technique across the board in CLI patients decreases the risk of immediate complications and facilitates accessing tibial arteries.

We investigated a thermal nondestructive evaluation (NDE) technique based on thermography that uses optical fiber thermal sensors to detect damage within a laminated graphite epoxy composite specimen. Two sets of composite samples were used for testing, one set had fiber optic sensors embedded between the layers while the other relied on thermocouple sensors attached to the exterior. A simulated impact system was used to induce damage of varying degrees into the samples. The damage was confirmed either with X-ray or C-scan imaging. The test apparatus in addition to the test data obtained from both sets of samples are presented. The data confirms that the fiber optic thermal sensors can not only detect the presence of damage, but can measure the severity of damage as well. This is the first known attempt to use in situ fiber optic point sensors with thermography to detect damage.