Comparative effects of nanoalumina and nanosilica on the mechanical, morphological, and thermal performance of additively manufactured PLA composites

The effects of nano-Al₂O₃ and nano-SiO₂ at 2 and 3 wt% on the mechanical, thermal, and morphological properties of polylactic acid (PLA) fabricated by fused filament fabrication (FFF) were investigated. Neat PLA and four nanocomposite formulations were produced and characterized by tensile, flexural, and compression tests, together with Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric/differential thermogravimetric (TGA/DTG) analysis, scanning electron microscopy (SEM), and energy-dispersive X-ray analysis (EDAX). The mechanical results showed that the effect of nanoparticle addition depended on filler type and loading level. S3 (3 wt% SiO₂) showed the highest mean tensile strength (38.23 ± 1.77 MPa), an 11.75% increase relative to neat PLA; however, differences in tensile strength among formulations were not statistically significant ( p = 0.442). A2 (2 wt% Al₂O₃) exhibited the highest flexural and compressive strengths, reaching 122.76 ± 1.89 MPa and 99.10 ± 1.47 MPa, corresponding to increases of 55.77% and 10.60% relative to neat PLA, respectively. The flexural differences were statistically significant ( p < 0.001), whereas the overall compressive ANOVA was significant ( p = 0.033). DSC results showed formulation-dependent changes in crystallization and melting behavior, while TGA/DTG analysis revealed variations in thermal degradation parameters among the formulations. FTIR showed the characteristic absorption bands of PLA, while SEM provided qualitative morphological observations and EDAX indicated the presence of the corresponding elements in the analyzed regions. Overall, the results demonstrate that the effects of nano-Al₂O₃ and nano-SiO₂ are property- and formulation-dependent rather than universally beneficial.