Damage localization on composite structures: Radial basis function application

The main purpose of Structural Health Monitoring (SHM) is to determine the integrity of a structure or component during their operational life. This is done, in order to schedule proper and effective actions to remove or mitigate any damage/defect that could affect the integrity of the system. Composite materials, widely used in aerospace applications, are characterized by low out-of-plane mechanical properties. An impulsive event such as low velocity impact (LVI) on this class of materials could cause barely visible impact damage (BVID) that is not detectable by a simple visual inspection, reducing the strength of the structure. This research work proposes an improved damage detection technique overcoming the limitations of the methods presented in literature (knowledge of the mechanical properties, the direction dependency of the wave speed, the attenuation and dispersion effects). The damage detection and localization technique is based on an active approach, using an array of sparse piezo sensors. One transducer is used as an acoustic actuator, inducing ultrasonic waves which propagate through the component, and the others are used as receiving sensors. The routine is based on the signal power of the response in the sensor's location and their interpolation by the radial basis function, from which the location of the damage is determined. The experimental campaign was performed on a simple carbon fiber reinforced plate fitted with eight piezo transducers, with multiple configurations of sending-receiving pairs. Good results were obtained with a good level of accuracy in damage localization estimation.