Damage Sensitivity Study in 3D-Printed PLA of Different Infill Densities Using the Electromechanical Impedance Method

Abstract

In many industries, complicated parts have been produced using additive manufacturing (AM) technology. The values of such products can significantly increase if they have fault detection and load sensing features. Modern industries, especially those with crucial applications, like aerospace and civil construction, have recently begun incorporating AM components into their designs. This necessitates the creation of precise and trustworthy methods for assessing and tracking the structural integrity of such components. Based on the local structural reaction in the high-frequency region, the Electromechanical Impedance (EMI) approach is frequently used to assess the health condition of lightweight structures with minute damage. This study investigates the sensitivity of the EMI technique to potential damage in 3D-printed polylactic acid (PLA) plates with different infill densities. Five healthy and five damaged PLA plates were printed using fused deposition modeling (FDM) with infill densities ranging from 20% to 100% at a step of 20% for the experimental study. Piezoelectric wafers (PZTs) bonded to one side of the plates were used for the measurements. Damage was mimicked by placing two strong magnets on either side of the healthy plates, and several EMI measurements were taken for the healthy states while changing the distance of the magnets away from the PZT. The conductance (G) and resistance (R) EMI measurements were fused together before the root mean square deviation (RMSD) damage index was used for the damage-sensitivity study. It was found that damage-sensitivity distance decreases with the decrease in the infill density. Further, damage-detection thresholding was investigated when using multiple sensors from identical healthy and damaged plates with printed built-in damage. The damage was detected for all the examined infill densities by the PZT positioned at a center distance of 102.5 mm from the damage.