Electromechanical impedance method of fiber-reinforced plastic adhesive joints in corrosive environment using a reusable piezoelectric device

Abstract

Various nondestructive evaluation techniques exist for structural health monitoring of structures such as acoustic emission, ultrasonic impedance, and impact echo testing. However, these techniques often require expensive and sophisticated hardware with expert operators, limiting their applications to a certain aspect. On the other hand, a relatively new technique known as electromechanical impedance–based structural health monitoring has shown promising results as a local nondestructive evaluation method. To date, only a few numbers of studies have been conducted to develop a reusable lead zirconate titanate sensor for the electromechanical impedance method as majority of researchers have focused on damage detection performance. In this study, a reusable method for the electromechanical impedance method was proposed by using a lead zirconate titanate patch to eliminate the trial-and-error approach to minimize the time requirement for the electromechanical impedance method while reducing the cost for multiple measurements. The proposed reusable device was used to evaluate the damage of the adhesive layer between the fiber-reinforced plastic plates subjected to a corrosive solution while investigating the reliability performance of the device.

Impedance Based Health Monitoring Technique with Probabilistic Neural Network for Possible Wall Thinning Detection of Metal Structures

“…In addition, managing such system would also be costly, as some places would be difficult for one to access (tall buildings, top of a bridge, etc.). Thus in this study, the idea of a reattachable PZT device introduced by Na et al [5] was used which allows one to attach and reattach the PZT device to a steel structure without any adhesive. Figure 2 shows the reattachable device for this study where a magnet disc of 25 mm diameter and 5 mm thickness is used with the 15 mm square PZT transducer attached to top of its surface using a commercial adhesive (Loctite quickset epoxy).…”

“…Afterwards, the PZT device is completely detached and attached again in the middle of the stack. This process is identical to the process shown in Figure 3 with the impedance signatures being measured until 10 signatures are acquired to be inserted into the first category as the training data (from nodes P (5,1) to P (5,10) ). The next set of training data is measured after removing a metal plate and then measuring the impedance signatures by attaching and detaching the PZT device until 10 signatures are obtained again (from nodes P (4,1) to P (4,10) ).…”

“…The next set of training data is measured after removing a metal plate and then measuring the impedance signatures by attaching and detaching the PZT device until 10 signatures are obtained again (from nodes P (4,1) to P (4,10) ). Training is complete once the impedance signatures are measured with the last metal plate, totaling 50 impedance signatures to be used as the training data for nodes P (5,1) to P (1,10) .…”

“…(1) Up to date, various authors have utilized the EMI method for damage detection [2][3][4][5][6][7][8][9][10][11][12][13]. Yu et al [2] introduced chemical corrosion using hydrochloric acid onto a pipe structure where it was detected by performing the EMI method in the frequency range of 200 to 2000 kHz using the HP4194A impedance analyzer.…”

“…In addition, the wiring and PZT attachment on the surfaces can make the structure visually unattractive possibly raising another problem of managing the brittle PZT patch when exposed to the environment for a long time. Thus in this study, a PZT material based device that does not need to be permanently attached to a host structure is utilized [5], allowing one to easily attach and reattach to a steel structure without leaving any trail of monitoring. Due to the high sensitivity of the impedance signature, the impedance signature completely changes when reattached.…”