Enhanced mechanical performance of 3D-printed PLA and carbon-fiber reinforced PLA sandwich structures via Taguchi-based process optimization

Fused Deposition Modelling (FDM) additive manufacturing is being used more and more to create lightweight polymeric composites. However, because of the intricate dynamics of interfacial bonding, processing parameter optimization for multi-material sandwich structures continues to be a special challenge. This work systematically investigates the tensile and flexural behaviour of 3D-printed polylactic acid (PLA) and carbon fibre-reinforced PLA (PLA-CF) sandwich specimens using a Taguchi L27 orthogonal array design. Layer height (0.20, 0.25, 0.30 mm), infill pattern (Gyroid, Tri-Hexagon, Honeycomb), and printing speed (125, 175, 225 mm/s) are among the control elements assessed. Multiple linear regression, analysis of variance (ANOVA), and signal-to-noise ratio plots were used to analyse the generated dataset for Young’s modulus, ultimate tensile strength (UTS), elongation at failure, and flexural characteristics. The statistical findings show that the infill pattern, which accounts for 48–80% of the property variance, is the most important element influencing mechanical performance. Quantitatively, the Triply Periodic Minimal Surface (TPMS) Gyroid pattern optimized tensile stiffness and ductility, whereas the Honeycomb core architecture produced the highest flexural strength and maximum ultimate tensile strength (∼28.5 MPa) because of effective planar stress distribution. Maintaining an ideal intermediate printing pace revealed to be physically necessary to guarantee correct interlayer fusion and avoid heat degradation during extrusion, even though variations in printing speed showed a slight statistical impact on the total property variance. Moreover, the stiffness and pseudo-ductility of the components were mostly affected by layer height. The suggested combination of sandwich architecture and parameter optimization offers a very efficient way to modify the mechanical performance of PLA-based composites for lightweight structural applications, which is supported by fractographic observations demonstrating improved interlayer bonding and fiber-matrix interaction under ideal conditions.