Influence of infill architecture on the mechanical performance and fracture behavior of FDM-manufactured PLA solid and honeycomb structures

The mechanical performance of Fused Deposition Modeling (FDM) components is strongly influenced by infill architecture, which controls stress transfer, structural continuity, and energy dissipation mechanisms. This study investigated the effect of concentric, hexagonal, and triangular infill architectures on the mechanical behavior of Polylactic Acid (PLA) specimens manufactured by FDM with 90% infill density. Structural, morphological, and chemical analyses confirmed that PLA maintained its integrity after processing and exhibited a predominantly amorphous structure. Mechanical performance was evaluated through tensile, flexural, and Charpy impact tests on solid and honeycomb structures. The concentric architecture exhibited the highest tensile strength (40.75 ± 1.73 MPa) and flexural strength (81.11 ± 2.69 MPa), demonstrating superior load-transfer efficiency and structural continuity. In contrast, the hexagonal honeycomb structure showed the highest impact resistance (2.88 ± 0.07 J/m), indicating enhanced energy absorption capability. One-way ANOVA and Tukey's post hoc analyses revealed statistically significant differences among infill architectures for tensile strength, flexural strength, and honeycomb impact resistance (p < 0.05), whereas no significant effect was observed for the impact resistance of solid specimens (p > 0.05). Fractographic analyses demonstrated that filament arrangement and interfacial bonding were the primary factors governing failure behavior. The results indicate that concentric architectures are preferable for static load-bearing applications, whereas hexagonal honeycomb structures are more suitable for lightweight impact-resistant components.