Experimental Characterization and Three Network Model-Based Finite Element Analysis of TPU-95A Lattice-Structured Airless Tires

Thermoplastic polyurethane (TPU) filaments are increasingly used in additively manufactured structures that require large deformation and flexible mechanical response. In this study, the mechanical behavior of TPU-95A filament was experimentally characterized and implemented in finite element analyses of lattice-structured airless tire prototypes. Tensile tests were conducted at three different loading rates using a custom-made desktop testing device, and the resulting stress–strain curves were used to calibrate the PolyUMod Three Network Model (TNM) in Ansys MCalibration version 25.1. Four airless tire prototypes were then designed, comprising a conventional hexagonal lattice and three lattice configurations based on auxetic unit-cell geometries: reentrant, arrowhead, and star. The prototypes were fabricated using fused deposition modeling and subjected to compression tests to characterize their force–displacement responses. Comparison with compression experiments at a single loading rate showed geometry-dependent agreement for the four investigated lattice configurations, supporting the applicability of the filament-derived TNM parameters under the tested conditions. Numerical predictions were validated against experimental force–displacement curves using the normalized root mean square error (NRMSE). The NRMSE values were 8.23%, 11.89%, 17.61%, and 3.94% for the hexagonal, reentrant, arrowhead, and star structures, respectively. Overall, the results demonstrate the capability of the calibrated TNM-based finite element approach to predict the compression behavior of additively manufactured TPU-95A lattice structures.