Use of a Novel Fiber Optical Strain Sensor for Monitoring the Vertical Deflection of an Aircraft Flap

The present paper reports the use of a plastic optical fiber-based sensor for elongation measurements in an aircraft flap subjected to different types of flexural loading conditions. The sensor, bonded to the surface of the aircraft structure, relies on measuring the phase shift that occurs between two sinusoidally modulated light signals when the aircraft structure is bent. The light signals are guided through two optical fibers, one of them fixed to the top surface of the flap, and the other one to the bottom surface. The sensor offers good signal stability and repeatability and represents a cost-effective alternative to other more sophisticated health-monitoring systems currently used.

I. Introduction

In recent years, there have been efforts for developing load-bearing structures that include health-monitoring systems. These systems represent an important aspect in the maintenance of different types of structures (e.g., bridges, roofs of sport centers, blades of helicopters or of wind power plants, airplane wings, etc.) through the use of embedded or surface-bonded sensors. In the case of the aerospace industry, the continuous flutter of wings during flight reduces significantly their service life. Therefore, a real-time self-diagnostic system that has the ability to monitor the dynamic response of these structures under the influence of loading conditions is clearly interesting.