Investigation of mechanical properties of PLA-SCF additively manufactured prosthetic sockets

Abstract
This study presents an integrated experimental and finite element investigation into the structural performance of fused deposition modeled (FDM) transtibial prosthetic sockets fabricated from short carbon fiber reinforced polylactic acid (PLA–SCF). Patient-specific socket geometry was derived from 3D scanning of a clinical residual limb mold, reconstructed in CAD, and printed at 1:3 geometric scale FDM printer with 100% infill density, 0.2 mm layer height and vertical build orientation. Axial compression testing yielded a mean compressive strength of 1.072 ± 0.370 MPa and a maximum load of 15.872 kN exceeding the ISO 10,328 P6 structural requirement when scaled by dimensional similarity while a coefficient of variation of 34.5% identified filament moisture sensitivity as the primary source of inter-specimen variability. Low-cycle fatigue testing revealed progressive, non-catastrophic crack initiation within 90–100 cycles under proportionally scaled mid-stance loading of 50–150 N, with interlaminar debonding confirmed as the governing failure mechanism by SEM analysis. The mean inner surface roughness of Ra = 14.81 μm marginally satisfies the proposed Ra < 15 μm clinical criterion for FDM prosthetic sockets. Finite element analysis predicted a peak von Mises stress of 1.255 MPa at the distal region, agreeing with experimental results within 11.6%. These findings establish interlaminar fatigue resistance as the primary limitation of PLA–SCF for prosthetic applications and provide a reproducible experimental baseline to guide future design optimization and clinical translation.