Acoustic based structural health monitoring for composites using optimal sensor placement: analysis and experiments

An acoustic based sensor network with optimal sensor placement is designed to characterize the existence of damage in composites. By incorporating the sensor certainty region and the sensing density, the developed optimal sensor set is able to provide an accurate description of the perturbations caused by the presence of damage. In the present study, piezoelectric sensors and actuators are used. A round-robin inspection is performed on the entire structure. Initially, the sensing region and the certainty region of a sensor-actuator pair are estimated, based on experimental data. The parameters of actuator position, excitation intensity, material properties of the host structure, the sensitivity property of the transducers, and detectable perturbations have been taken into account in the estimation. In multi-sensor applications, the placement of two neighboring sensors leads to an overlap between their certainty regions. Therefore, the overlap of the neighboring sensors is determined next and the minimum overlapping criteria is imposed in the design of sensor sets. This is further extended for each sensor member until certainty regions of the optimal number of sensors cover the entire structure, provided the minimum overlap criteria and additional geometric constraints are satisfied. Thus, the developed procedure is able to provide the optimal placement of the sensors. Parametric studies are conducted using composite laminates with seeded delaminations. Comparisons between healthy and delaminated structures are presented. The local effects of the sensors are identified. Both numerical and experimental results are presented for validation.