Optimizing Charpy Impact Strength of Material‐Extruded PLA Through Layer Height, Raster Angle, and Infill Geometry

ABSTRACT The impact performance of material‐extruded polymer components is strongly influenced by process‐dependent internal structure, making parameter selection critical for applications requiring improved damage tolerance. In this study, the Charpy impact strength of polylactic acid (PLA) parts fabricated by material extrusion was investigated using a three‐factor, three‐level full factorial design. The effects of layer height (0.1, 0.2, and 0.3 mm), raster angle (0°, 45°, and 90°), and infill geometry (triangle, octet, and gyroid) were evaluated across 27 unique processing conditions. By evaluating all parameter combinations using PLA at a fixed infill density of 20%, the full factorial design enabled determination of both the individual and interaction effects of the three parameters, rather than considering only isolated parameter trends. ISO 179‐compliant specimens were manufactured and tested under Charpy impact loading. Analysis of variance revealed that layer height was the primary factor influencing impact strength, followed by raster angle and its interaction with layer height, while infill geometry also made a significant contribution to the response. The highest impact strength of 10.59 ± 0.02 kJ/m 2 was obtained at a layer height of 0.3 mm, a raster angle of 0°, and an octet infill geometry. In addition to inferential statistical analysis, an ordinary least squares quadratic response model was used to characterize the effect of layer height, indicating diminishing gains near the upper end of the investigated range. The results show that the impact resistance of material‐extruded PLA is governed by a coupled process–structure relationship and provide practical guidance for selecting printing conditions in applications requiring improved toughness and structural reliability.