Optimization of Lamb wave actuating and sensing materials for health monitoring of composite structures

Abstract

In a continuing effort to examine the effectiveness of Lamb wave methods for the health monitoring of composite structures, this paper presents the conclusions of an analytical and experimental study optimizing piezoelectric patches to detect damage within composite laminates. Previous research has demonstrated the ability of Lamb waves to provided useful information about the presence of damage in simple narrow coupons, and they have yielded the possibility of estimating severity and location of damage as well. During the course of this NRO funded research program, several types of piezoelectric materials in various configurations were analyzed in order to produce the highest force actuator and best resolution sensor at the lowest power level. Consideration was also placed towards directionality of wave propagation, and durability, reliability and reproducibility of the sensing patch itself. Experiments were then carried out on narrow coupon laminates to qualify and tune these actuating/sensing patches. New algorithms were used to filter and decompose the resulting signals to more efficiently detect the presence of damage for automated use, and gather information relating to the damage type, severity and location. SHM technologies will enable conditionbased maintenance for efficient structural design, will reduced overall life-cycle costs, and eliminate scheduled inspections

Structural Health Monitoring Using Guided Ultrasonic Waves

“…The ::;hape of piezoceramic transducers deterrnirws the directivity of wave propagation, as shown in [81]. Rectangular piezoc:eramics offer parallel generation/propagation of waves to transducer edges whereas circular piezocerarnics generate and propagate waves circumferentially.…”

“…The basic factors which determine damage detection based on Lamb waves are related to [77,78,79,80,81 J: properties of the structure under inspection, selection of wave propagation modes, transducer selection and location, transducer validation against possible failures, transducer coupling methods and choice of excitation signals, as briefly discussed in this section. Other elements, described in the next section, include various aspects related to signal processing techniques for damage feature extraction.…”

Capacitive Micromachined Ultrasonic Transducers: Technology and Application

“…Within a plate-like structure, Lamb waves are the most commonly encountered guided wave mode, as they can propagate over long distances in plates and pipes [48]. They have been used for inspection and structural health monitoring in many situations [49]. The presence of Lamb waves can complicate the analysis of signals by their dispersive nature.…”

Ultrasonic Lamb wave tomography using scanned EMATs and wavelet processing

“…The properties of both Rayleigh and Lamb waves for NDE and monitoring applications are well documented (Viktorov 1967). For example, Lamb waves have been used to carry out rapid inspection of various structures (Kessler and Dunn 2003), including boilers and heat exchanger piping (Zongqi et al 1999). They can also be used to determine the elastic properties of materials (Hayashi et al 1999), and to measure the anisotropic properties of cold-rolled metals (Murayama 2001).…”