Analysis of Mechanical Properties of 3D-Printed Structures with Varying Infill Ratios

Additive manufacturing (AM) technologies, particularly material extrusion (MEX), have enabled the production of structurally optimized parts with minimal material usage. In this study, the effect of infill ratio and internal geometry on the mechanical performance of MEX-printed PLA components was investigated through experimental testing. Specimens with gyroid and honeycomb infill patterns were produced with infill ratios of 50% to 100% with 10% increments. Three-point bending tests were conducted to evaluate flexural strength and fracture behaviour, while selected specimens were also subjected to heat treatment at 100 °C for 20 minutes to assess post-processing effects. Results showed that honeycomb structures consistently achieved higher strength-to-weight ratios than gyroid, indicating superior material efficiency. Both patterns exhibited a nonlinear increase in mechanical strength with infill ratio, with significant performance gains between 90% and 100%. Heat treatment demonstrated a pattern-dependent impact, honeycomb structures showed slightly improved flexural strength, while gyroid specimens experienced reduced load capacity. Furthermore, ductility was reduced in both infill structures after heat treatment.