Decoupled temperature and strain measurements using fiber Bragg grating sensors

Abstract

Temperature and strain sensing of critical aircraft engine components is a critical health and prognostics tool for future engine programs. Real-time feedback of key temperature and strain measurements can be used to provide better estimates to ground crews of engine component life, thus minimizing engine downtime and maximizing the effectiveness of planned inspections. One method for monitoring distributed stress and temperature throughout an engine is through the use of Fiber Bragg Grating (FBG) sensors. With just a single sensor line, both temperature and strain can be monitored simultaneously and in a distributed fashion. Unfortunately, FBG sensors bonded to a host structure are susceptible to both thermal strains and mechanically-loaded strains simultaneously, and without intelligent sensor design, the two signals are indistinguishable from each other. In the present work, a sensing array design is proposed and demonstrated to provide a means for separating thermal and mechanically-loaded strain signals by using two FBG sensors in close proximity to each other. Experimental results are provided using a structural beam element to demonstrate the feasibility of the proposed approach for decoupling the temperature and strain effect from fiber Bragg grating sensors.