Experimental Characterisation and Finite Element Modelling of Polyamide-11 Fabricated via Multi Jet Fusion

HP Multi Jet Fusion (MJF) polyamide-11 (PA11) was characterised experimentally and used to calibrate finite element material models for the quasi-static regime. Characterisation covered tension in six build orientations and compression in three. Validation used threepoint bending at XY and YX, and a vertically aligned triply periodic minimal surface (TPMS) gyroid. The flat XY orientation was the anisotropy extreme, carrying a tension-compression yield asymmetry of 30.2% that fell to 14.3% at YX and was negligible at XZ. The modulus asymmetry ran the opposite way, 7% at XY against 20% to 27% elsewhere. Elastic-plastic and asymmetric models were calibrated at the representative YX basis, with XY as the constraining case. Single-stress-state fits deviated by up to 7.8% in the other branch, and the tabular tension-only fit failed outright in compression at YX. At YX the fits carrying both branches held both stress states, the asymmetric formulation trading compressive accuracy for tensile, and at XY it alone held both. In three-point bending the asymmetric YX model matched the experiment, while the XY coupons exceeded both XY-calibrated models, an unexplained flexure elevation. In the gyroid crush the leading YX models reproduced the three-phase response, slightly over-predicting the plateau. YX is recommended as the calibration basis, with the combined-hardening elastic-plastic fit as the general-purpose model. The asymmetric formulation should be considered where bending stiffness governs, on the strength of an empirical rather than mechanistic agreement.