Fiber Bragg Gratings, IT Techniques and Strain Gauge Validation for Strain Calculation on Aged Metal Specimens

Ander Montero,Idurre Saez De Ocariz,Ion Lopez,Joseba Zubia,Pablo Venegas,Javier Gomez

doi:10.3390/s110101088

Abstract

This paper studies the feasibility of calculating strains in aged F114 steel specimens with Fiber Bragg Grating (FBG) sensors and infrared thermography (IT) techniques. Two specimens have been conditioned under extreme temperature and relative humidity conditions making comparative tests of stress before and after aging using different adhesives. Moreover, a comparison has been made with IT techniques and conventional methods for calculating stresses in F114 steel. Implementation of Structural Health Monitoring techniques on real aircraft during their life cycle requires a study of the behaviour of FBG sensors and their wiring under real conditions, before using them for a long time. To simulate aging, specimens were stored in a climate chamber at 70 °C and 90% RH for 60 days. This study is framed within the Structural Health Monitoring (SHM) and Non Destructuve Evaluation (NDE) research lines, integrated into the avionics area maintained by the Aeronautical Technologies Centre (CTA) and the University of the Basque Country (UPV/EHU).

Highlights

The latest trends in aircraft design are aimed at decreasing the costs associated with aircraft maintenance and operation, while ensuring their maximum safety
For this reason Structural Health Monitoring (SHM) research with reliable and light systems is becoming increasingly important in the area of avionics
The Sikaflex glue has produced misreadings of every Fiber Bragg Grating (FBG) in which it was present, not being in many cases the tension increases applied and microstrain lectures obtained from FBGs proportional

Summary

Introduction

The latest trends in aircraft design are aimed at decreasing the costs associated with aircraft maintenance and operation, while ensuring their maximum safety. For this reason SHM research with reliable and light systems is becoming increasingly important in the area of avionics. The main objectives of this study have been: Study of parameters which affect incorrect FBG sensor and strain gauge readings. Analysis of the influence of aging FBGs and strain gauges on extreme conditions of temperature and relative humidity (real conditions of use over long periods of time)

Methods

Results

Conclusion