The Effect of the Infill Density in 3D-Printed PLA on Lamb Waves' Propagation Characteristics and their Sensitivity to the Presence of Damage

Due to its many advantages and fast development, additive manufacturing (AM) is evolving from prototyping and simple applications to the manufacturing of complex industrial components. Modern industries including those with critical applications, like aerospace and civil constructions, have recently started adopting AM parts within their structures. This imposes the need to establish reliable and robust techniques to assess and monitor the structural integrity of such components. This study focuses on understanding the propagation of ultrasonic Lamb waves (LWs) in 3D printed poly(lactic acid) (PLA) plates of various infill densities; further, on determining the sensitivity of the propagating wave to buried defects within the plates under study. Intact and damaged PLA plates, printed using fused deposition modeling (FDM) with different infill densities, were used for the investigation. LWs were excited using lead-zirconate-titanate (PZT) wafers, and their propagation was visualized through area-scans using a laser Doppler vibrometer. The fundamental LW modes were characterized and successfully used in the detection and localization of damage regions. The obtained results show a high potential of LW-based techniques for the structural health monitoring of 3D-printed structures.