SHM OF ORTHOTROPIC PLATES THROUGH AN ULTRASONIC GUIDED WAVE STMR ARRAY PATCH

The Single Transmitter Multiple Receiver (STMR) array based Structural health monitoring (SHM) technique has been introduced for evaluation of isotropic and anisotropic plate like structures. SHM is carried out by utilizing a phased addition reconstruction algorithm for imaging damage in large plate-like structures. A flexible Printed Circuit Board (PCB) based patch was developed for SHM of aluminum and composite plates. Additionally, an elastic moduli reconstruction algorithm is described here, using the PCB array patch, which can be applied in at least two cases; (a) for SHM applications, the leave-in-place compact array can provide a means for the in-situ measurement of changes in the elastic moduli during the life time monitoring of structures, thereby providing velocity data for the phased addition reconstruction algorithm, and (b) for materials characterization, where the compact array can be developed as a portable sensor for the measurement of elastic moduli of in-service and as-fabricated structures. This elastic moduli reconstruction method uses the velocity measurement of the fundamental guided Lamb wave modes (S0 and A0), generated from a central transmitter, and received by a sparse array of receivers that encircle the transmitter. Sensitivity analysis of orthotropic elastic moduli to the Lamb wave velocity of S0 and A0 modes has been carried out. Experiments were conducted on 3.15 mm graphite-epoxy composite plate using PCB based STMR array.