Mechanical behavior and constitutive modeling of 3D-printed PLA, TPU, and nylon: Influence of raster layup configurations

Fused Deposition Modeling (FDM) produces thermoplastic parts cost-effectively but induces mechanical anisotropy due to layer-by-layer deposition and raster orientation. This study examines uniaxial tensile behavior of FDM-printed PLA, TPU, and Nylon specimens using four layup configurations: aligned [0°] ₁₀ , transverse [90°] ₁₀ , Grid (±45°), and quasi-isotropic [0°/45°/90°/-45°] _2s , with video extensometry for precise strain measurement.

PLA shows brittle, linear-elastic response in most layups (inter-fiber debonding or fiber rupture), with quasi-isotropic introducing post-yield ductility fitted by Voce law. TPU exhibits rubber-like hyperelasticity and early failure in transverse layups. Nylon displays intermediate stiffness and ductility. The Ogden model fits TPU hyperelasticity well; an enhanced DSGZ model captures Nylon's full flow stress, including necking. Quasi-isotropic layups reduce anisotropy, improving design reliability for compliant mechanisms and prototypes.