Continuous sensors for mode selective actuation and reception of waves for structural health monitoring of woven composite laminates

The quantitative evaluation of damage in woven composites using mode selective excitation of Lamb waves is reported in this paper. PVDF (polyvinylidene fluoride) comb sensors are used to generate and detect a single plate mode. The top electrode is a single set of equidistant fingers connected in parallel to the same potential while the bottom electrode is kept at ground. First, a pair of such sensors is used to generate and detect a single plate mode. Group velocity changes of a wave packet traveling through the damaged area are used for quantitative damage estimation. Second, a new electrode configuration is used in order to improve the receiver signal. The proposed configuration referred to as continuous sensors, is used in structural health monitoring (SHM) for detection of growing cracks. Theoretical and experimental results are presented. In addition, an analog circuitry to actuate the structure at high frequency (∼1MHz) based on energy tapped from a vibrating cantilever beam (∼20Hz) is developed, towards a high-frequency energy-harvested SHM.