Characterization of the mechanical properties of TPU fabricated by SLS in different printing orientations

Abstract

This study presents the mechanical characterization of a thermoplastic polyurethane (TPU) powder (FlexaBright^TM, Sinterit, Poland) fabricated by selective laser sintering (SLS). Despite its growing use in applications requiring elastomeric and rubber-like mechanical behavior, its characterization under finite tension and compression loads, as well as different print orientations, has not been thoroughly documented. To address this gap, we conducted uniaxial tension and compression tests on specimens printed in multiple orientations. The experiments included pre-conditioning cycles, measurement of force relaxation, and the estimation of equilibrium force using exponential decay fitting. Full-field strains were obtained using 3D digital image correlation (3D-DIC), and micro-CT scans were employed to accurately determine the specimens' cross-sectional areas. Elastic material parameters were estimated by fitting stress-strain data for the tension tests and by inverse finite element analysis of the compression data, for each print orientation. Although the Poisson's ratio remained similar across all tests, the results revealed clear anisotropy in the stiffness: horizontally printed specimens exhibited a Young's modulus that was 29% smaller in tension and 15% larger in compression compared to vertically printed specimens. These findings highlight the influence of print orientation on mechanical properties and provide essential material parameters for various engineering applications. Future research will explore the fitting of more complex anisotropic and viscoelastic models, as well as examine additional deformation regimes.