Experimental Characterization of the Mechanical Properties of 3D-Printed TPU Using Wave Band Gaps in a Periodic Composite Structure

Characterizing the mechanical properties of 3D-printed, highly damped polymers with various infill patterns and densities using conventional dynamic testing methods based on natural frequencies presents significant challenges. Overdamped systems often lack distinct resonance peaks in their frequency response, making curve fitting unreliable. In this study, we propose an alternative approach by leveraging wave band gap frequencies to characterize such materials. A periodic composite structure, consisting of 3D-printed thermoplastic polyurethane (TPU) and aluminum, is used to identify wave band gaps, enabling the estimation of key mechanical properties such as elastic modulus and Poisson's ratio. Specifically, 3D-printed TPU samples with a 50% gyroid infill are integrated into a four-cell periodic arrangement of TPU and aluminum cylinders, designed to ensure homogenization of the heterogeneous material's properties. The gyroid infill pattern is selected for its well-documented isotropic mechanical behavior. The results demonstrate that the characterized TPU material effectively generates band gaps at low frequencies within the audio range, making it a promising candidate for vibration isolation applications, such as vibration mounts.