Characterization of Damping Properties in 3D Printed Structures

Current research on the effectiveness of a subordinate oscillator array (SOA) as a broadband mechanical filter relies on adequate knowledge of the SOAs material properties. Recent studies have shown a high sensitivity of these structures to disorder. A desire to produce large numbers of arrays to test this sensitivity to disorder motivated a transition from metal to 3-dimensional printed plastic SOAs. Irregularities associated with the curing process of the 3D printed polymers, as well as a general inconsistency of material properties of plastics, in turn highlighted the need for characterization of properties of 3D printed materials, especially those properties related to damping. As part of this study, several 3D printed plastic cantilevers, varying in material, printing technique, and printing orientation, are measured. Quantities of interest include the Young's modulus and density, as well as phenomenological properties, like the quality factor of specific designs. An ASTM standard test method for property determination is implemented with a laser Doppler vibrometer (LDV) to test each polymer. In addition to the ASTM protocol, tests are conducted in vacuum to distinguish internal damping mechanisms of the cantilever from external fluid mechanisms. Results are compared to both analytic and numeric predictions and published theory. (paper)