V. Giurgiutiu, C. Jenkins, A. Cuc, University of S. Carolina, Columbia, SC

Summary:

Piezoelectric wafer active sensors (PWAS) are inexpensive, non-intrusive un-obtrusive devices that can be surface-mounted on existing structures, or inserted in a new composite structure. The PWAS can be used in both active and passive modes. In active mode, the PWAS generate Lamb waves that can exist as either traveling waves or standing waves. As traveling waves, PWAS-generated Lamb waves can be used with the pitch-catch, pulse-echo, or phased-array methods that arrow far-field and some medium-field damage detection. As standing waves, PWAS-generated Lamb waves can used in conjunction with the electro-mechanical (E/M) impedance technique that allows near-field and some medium-field damage detection.

This paper presents new results obtained in the use of PWAS for the structural health monitoring of aerospace vehicles. One set of results to be presented will refer to experiments performed on detection the crack propagation in a fracture-mechanics panel with a stress-concentration hole in the center. The crack was propagated using cyclic fatigue loading in a large testing machine. Another set of results will refer to the PWAS monitoring of preexisting simulated cracks, corrosion, and disbonds in an aerospace panel. The third set of results to be presented will report on preliminary tests performed towards the understanding of how PWAS can be used to monitor damage in relatively thick structural parts with complex geometry, material interfaces, and fasteners. Details of these experiments and interpretation of the results will be presented.