Damage Detection Using d15 Piezoelectric Sensors in a Laminate Beam Undergoing Three-Point Bending

Hussain Altammar,Anoop Dhingra,Nathan Salowitz

doi:10.3390/act8040070

Hussain Altammar, Anoop Dhingra + Show 1 more

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https://doi.org/10.3390/act8040070

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Abstract

A major inhibition to the widespread use of laminate structures is the inability of nondestructive testing techniques to effectively evaluate the bondline integrity. This work proposes and analyzes a bondline-integrity health monitoring approach utilizing shear-mode (d15) piezoelectric transducers. The d15 transducers were embedded in the bondlines of symmetric laminate structures to monitor and evaluate the bondline integrity using ultrasonic inspection. The d15 piezoelectric transducers made of lead zirconate titanate (PZT) enabled ultrasonic inspection of bonds by actuating and sensing antisymmetric waves in laminate structures. Design considerations, fabrication process, and experimental methods for testing a laminate specimen are presented. Designs included bondline-embedded d15 PZT piezoelectric transducers with surface-mounted transverse (d31) piezoelectric transducers for signal comparison. Defects in the bondline were created by a quasi-static three-point bending test, with results showing the ability of d15 piezoelectric transducers to detect bondline damage. Two damage indices based on Pearson correlation coefficient and normalized signal energy were implemented to evaluate the presence of damage and its severity. The experimental results demonstrate the ability of bondline-embedded d15 piezoelectric transducers to be used as actuators and sensors for ultrasonic health monitoring of bondline integrity. A comparison between surface-mounted d31 PZT and bondline-embedded d15 PZT sensors was also conducted. It was seen that signals sensed by bondline-embedded d15 PZTs showed higher distortion due to bondline defects compared with the sensed signals from the surface-mounted d31 PZT.

Highlights

Ultrasonic non-destructive testing and evaluation (NDT/E) techniques are commonly used for inspection of structures including complex laminate structures
This paper presented an investigation into bondline damage detection employing d15 piezoelectric transducers that were embedded within the bondline of a laminate structure
Two methods were implemented in this experiment to assess the ability of d15 PZT transducers to monitor adhesive joint integrity: (1) ultrasonic wave propagation method to inspect the regions between the sensors and (2) electromechanical impedance (EMI) method to inspect the regions at the location of sensors using its inherent sensitivity to structural stiffness

Summary

Introduction

Ultrasonic non-destructive testing and evaluation (NDT/E) techniques are commonly used for inspection of structures including complex laminate structures. A major roadblock to the widespread use of laminate structures is the inability of NDT/E techniques to effectively discriminate between a pristine bond and a damaged bond [1]. Ultrasonic structural health monitoring (SHM) methods employ embedded sensors with the goals of automating damage detection to improve safety and reliability while reducing maintenance costs in engineering structures. The use of internally embedded sensors presents new opportunities to inspect laminate structures with the potential to expand the use of laminate structures beyond their current limit. Various researchers have experimented with internally embedded bondline damage detection using electromechanical impedance methods [2,3].

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