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Experimental Model of Impact Damage for Guided Wave-Based Inspection of Composites

The objective of this work is to assess to which extent the interaction of antisymmetric ultrasonic guided waves with impact damage can be captured with an experimental model consisting of a single artificial delamination in composite structures. The structures of interest are composed of unidirectional prepreg carbon fiber-reinforced polymer (CFRP) with a quasi-isotropic layup. The artificial delamination is introduced into the laminate using two circular Teflon tapes during manufacturing and the realistic damage is simulated by impacting the samples at two energy levels. Two colocalized rectangular piezoceramics are used to generate an antisymmetric mode and noncontact measurement is performed using a three-dimensional (3D) laser Doppler vibrometer (3D-LDV) to extract the required information for evaluation of the reflection, transmission, as well as the scattering behavior of the antisymmetric mode. The corresponding coefficients as a function of frequency, incident angle, and type of damage are extracted. It is found that the amplitude of the coefficients and directivity patterns of scattered waves are barely affected by incident angle but significantly by the impact energy. In light of the results, design guidelines are proposed for efficient guided wave inspection of composite structures submitted to impacts.