Guided Lamb Wave Sensing Using Polarization-maintaining Fiber Bragg Gratings

Dr. Gang Wang (UAH Mechanical & Aerospace Engineering)

Abstract

In this talk, guided Lamb wave sensing using polarization-maintaining (PM) fiber Bragg grating (PM-FBG) sensor is discussed. The goal is to apply the PM-FBG sensor system to composite structural health monitoring (SHM) applications in order to realize directivity and multi-axis strain sensing capabilities while using reduced number of sensors. Comprehensive experiments were conducted to evaluate the performance of the PM-FBG sensor in a composite panel structure under different actuation frequencies. Three Macro-Fiber-Composite (MFC) piezoelectric actuators were used to generate guided Lamb waves, which are oriented at 0, 45, and 90 degrees with respect to PM-FBG axial direction, respectively. The actuation frequency was varied from 20kHz to 200kHz. It is shown that the PM-FBG sensor system is able to detect high-speed ultrasound waves and capture the characteristics under different actuation conditions. Both longitudinal and lateral strain components in the order of nano-strain were determined based on the reflective intensity measurement data from fast and slow axis of the PM fiber. It must be emphasized that this is the first attempt to investigate acousto-ultrasonic sensing using PM-FBG sensor. This could lead to a new sensing approach in the SHM applications.