Structural integrity and load monitoring of a UAV V-tail using fiber optic point sensing and distributed sensing

This paper presents the design and application of fiber-optic distributed and point sensors for structural load monitoring and bond line integrity monitoring during a V-Tail ultimate loading test. The presented sensing method can be also used for monitoring the structural integrity of Unmanned Aerial Vehicles (UAV) during their life time cycle. Static ultimate load tests are a critical stage in the development and verification of newly designed aero structures. The UAV structure must be able to support l.5 times the maximum load to be expected in service (limit load). In this specific ultimate load test, a UAV control surface, V-Tail (shown in Figure 1), was gradually subjected to increasing load steps until reaching the ultimate load. After reaching that load, the structure was then loaded up to failure. This work describes the implementation of the sensor network, which was executed during the standard manufacturing process, in a relatively quick and easy integration process. The bond line integrity monitoring concept, which relies on strict linearity between the induced strain and the applied load, considerably benefits from the high spatial resolution of the distributed optical sensing. Furthermore, this system can be used to reaffirm, validate and gain higher confidence in the analytical stress model. This work demonstrates the use of such sensing concept to detect a debonding defect at an early stage of the ultimate test, before reaching failure, and determine its spatial magnitude.