A Comprehensive Investigation of Infill Geometry Effects on the Mechanical Performance of Polymer 3D Printed Components

Fused filament fabrication (FFF, often called FDM) is widely used in polymer additive manufacturing; however, it suffers from mechanical anisotropy and weak bonding in the Z direction. This work examines how the infill pattern influences the tensile response of PLA parts at fixed printing conditions. Dog-bone specimens (PLA, four patterns: grid, honeycomb, rectilinear, adaptive cubic) were printed and tested in tension (n = 3 per pattern). Grid yielded the highest ultimate tensile strength, whereas honeycomb produced the largest Young's modulus; rectilinear was intermediate and adaptive cubic was trailed in both metrics. X-ray diffraction of printed PLA showed a broad halo at 16-20° (2θ) with weak α-form reflections, consistent with largely amorphous microstructure after FFF. Together, the results indicate that, at constant material and nominal infill, pattern selection alone can shift the strength-stiffness balance, with grid favoring strength and honeycomb favoring stiffness.