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Research Papers

Piezoelectric Wafer Active Sensors for Structural Health Monitoring of Composite Structures Using Tuned Guided Waves

[+] Author and Article Information
Victor Giurgiutiu

 University of South Carolina,Columbia, SC 29208

J. Eng. Mater. Technol 133(4), 041012 (Oct 20, 2011) (6 pages) doi:10.1115/1.4004698 History: Received March 13, 2011; Accepted July 13, 2011; Published October 20, 2011; Online October 20, 2011

Piezoelectric wafer active sensors (PWAS) are lightweight and inexpensive transducers that enable a large class of structural health monitoring (SHM) applications such as: (a) embedded guided wave ultrasonics, i.e., pitch-catch, pulse-echo, phased arrays; (b) high-frequency modal sensing, i.e., the electro-mechanical (E/M) impedance method; and (c) passive detection (acoustic emission and impact detection). The focus of this paper is on the challenges posed by using PWAS transducers in the composite structures as different from the metallic structures on which this methodology was initially developed. After a brief introduction, the paper reviews the PWAS-based SHM principles. It follows with a discussion of guided wave propagation in composites and PWAS tuning effects. Then, it discusses damage modes in composites. Finally, the paper presents some experimental results with damage detection in composite specimens. Hole damage and impact damage were detected using pitch-catch method with tuned guided waves being sent between a transmitter PWAS and a received PWAS. Root mean square deviation (RMSD) damage index (DI) were shown to correlate well with hole size and impact intensity. The paper ends with summary and conclusion; suggestions for further work are also presented.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Modes of operation of piezoelectric wafer active sensors (PWAS) transducers: (a) propagating guided Lamb waves; (b) standing guided Lamb waves; (c) PWAS phased arrays

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Figure 2

Dispersion curves for unidirectional 65/35 graphite-epoxy plate: (a) θ=0∘; (b) θ=36∘. Note: c is the wave speed in m/s; ξd is the dimensionless wavenumber-half thickness product.

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Figure 3

Experiment setup measuring directional wave speeds in a [(0/45/90/-45)2]S plate 1240-mm x 1240-mm with 2.25-mm thickness. The plate was laminated from T300/5208 unidirectional CFRP tape

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Figure 4

Tuning of PWAS guided waves in composites: (a) quasi-A0 mode, quasi-S0 mode, quasi-SH0 mode. (b) comparison of theoretical prediction (full line) vs. experimental values for A0 mode.

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Figure 5

Experimental set-up for damage detection on quasi-isotropic composite panel: Featured on the plate are: 14 PWAS transducers (p0 through p13); one hole damage; two impact locations (1 and 2)

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Figure 6

Pitch-catch hole detection results showing DI values at different damage step values and different PWAS pairs for f=54 kHz, i.e., when only A0 mode is present

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Figure 7

Detection of impact damage at location 1: DI values as a function of the damage level for PWAS pairs p9-p10 and p11-p12 (f=54 kHz, i.e., when only A0 mode is present)

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