Localization of Impact on Composite Plates Using Ultrasonic Waves

In this work an approach for detecting and locating impacts on composite plates using piezoelectric transducers is presented. Low velocity impacts are among the most common causes that trigger the advance of barely visible damages in aerospace composite structures. Deeper knowledge of the location of potentially damaged areas allows to evaluate composite structures with less effort and significantly reduces system downtime. A quasi-isotropic composite plate composed of 8 layers are investigated in finite element software ABAQUS. Wave propagation speed in a material and time delay between stress waves, opens way to estimate impact locus. However, measuring velocity in anisotropic material is not very simple due to different mechanical properties along different directions. An array of piezoelectric sensors provides the history of plate deflections. Hitting some impacts at desired places and measuring time difference between voltages measured by sensors, enable the velocity curve to be identified over any direction angle. A geometric-based technique is used for processing voltage signals of piezosensors that leads to find impact coordinates on the plate. The proposed method partitions the plate into equal elements and calculates an error function for each of these elements; which measures the difference between relative time of flight (TOF) and expected arrival time. Optimizing this error function yields to estimate of the impact location. The presented method shows capability to determine the impact location in with less than one inch accuracy.

Keywords:

impact localizaion , composite plates , piezoelectric transducers , Error Function.