Build orientation- and strain rate-dependent compressive response of SLS-printed glass-filled polyamide

Selective laser sintering (SLS) produces functional polymer components with complex geometries, yet the compressive behavior of printed parts across build orientations and strain rates remains sparsely documented. This study examines how build orientation and strain rate affect the compression response of glass bead-filled polyamide 12 (PA12-GF) printed on a Formlabs Fuse 1 using a fixed unidirectional scan strategy. Cylindrical specimens conforming to ASTM D695 (12.7 mm diameter, 25.4 mm length) were compressed to 50% engineering strain in seven build orientations ( X , Y , Z , D _xy , D _xz , D _yz , D _xyz ) at four strain rates (0.01, 1, 3, and 5 s ⁻¹ ). Compressive modulus and 0.2% offset yield stress were obtained from the stress-strain curves using adaptive toe compensation followed by ordinary least-squares regression. Microstructure was characterized by X-ray diffraction (XRD) for the crystalline phase, scanning electron microscopy (SEM) for bead morphology and interfacial bonding, density measurements using Archimedes and geometric methods. X-ray computed tomography (XRCT) was used to estimate the volumetric glass fraction. PA12-GF shows a clear stiffness-strength trade-off under compression, with the compressive modulus reaching 1.51 to 2.18 GPa while the yield stress remains within 41.0 to 61.7 MPa across all orientations and strain rates. SEM observations suggest that early yielding is associated with stress concentrations at the bead–matrix interface, as evidenced by debonding gaps and bead pullout craters on the fracture surface. The presence of glass beads alters the orientation response by providing additional load-transfer pathways across hatch boundaries, while interlayer interfaces remain the weaker load path in the build direction. Over the tested range, the modulus of elasticity increases with strain rate in all orientations, whereas the yield stress peaks near 3 s ⁻¹ before declining at 5 s ⁻¹ in most orientations. This behavior is consistent with local thermal softening from plastic-work heating, although other rate-dependent mechanisms may also contribute to the observed softening, including bead-matrix debonding. These results provide an orientation- and strain-rate-dependent compressive dataset and a microstructure-based framework for understanding the mechanical response of SLS-printed PA12-GF components.