Impact localization on composite plates using two developed imaging methods

This paper focuses on using two developed imaging methods to localize the impact points on a composite plate. The first developed imaging method (Method 1) was firstly investigated on a metallic plate. A network of nine piezoelectric wafer active sensors (PWAS) was instrumented on an aluminum plate to receive impact signals. Based on Method 1, we need at least three sensors, which can be used to determine two hyperbolic paths, to localize an impact point on a metalic plate with known group velocities of generated waves (known its material properties). The observed results indicate that Method 1 can be used successfully to localize the impact points on a metallic plate. These successful results motivated us to investigate Method 1 on a composite plate. A second experiment of impact localization was implemented on a composite plate. Two clusters of sensors (every cluster has three PWAS transducers) were instrumented on the composite specimen to receive the generated acoustic waves due to break pencil leads at different points. The received signals were anaylized using a wavelet transform to determine the time of flight. The group velocity profile of antisymmetric Lamb wave mode was determined analytically at certain frequency. Based on Method 1, two hyperbolic paths, which are generated by four sensors, can be used successfully to localize the impact points on a composite plate with known its material properties. The second developed imaging method (Method 2) was investigated on the same composite specimen with assumption of unknown its material properties (unknown group velocity profile of generated wave). Based on Method 2, we need six sensors distributed on two clusters to determine two straight line paths. The intersection point of these two lines represents the impact point. The results showed that Method 2 can successfully localize the impact points on a composite plate.