Frequency-Dependent Effects of Material Extrusion Parameters on the Storage Modulus and Loss Factor of PETG

Additive manufacturing by material extrusion enables the fabrication of geometrically complex components, yet the extent to which process parameters can be used to tailor stiffness and damping in a frequency-dependent manner remains insufficiently understood. This study investigates the influence of key material-extrusion process parameters (layer height, printing speed, extrusion temperature, build plate temperature, and flow rate) on the flexural storage modulus E′ and loss factor η of PETG specimens over a frequency range of 125 to 4000 Hz. Frequency-resolved regression models were established for six reference frequencies using VIF-based term reduction and hierarchical backward elimination. The results reveal a clear contrast between stiffness- and damping-related responses. The model structure for E′ remained invariant across all frequencies, achieving consistently high coefficients of determination (R2 = 0.831–0.847). In contrast, the model structure for η varied markedly with frequency (R2 = 0.215–0.763). Extrusion temperature was identified as a consistently significant factor for η across all frequencies (p<0.05), while a robust nonlinear dependence on flow rate dominated most frequency bands. Reduced model adequacy for η was observed at specific bands, showing significant lack-of-fit at 500 Hz (pLOF=0.049) and non-normal residuals at 4000 Hz (pJB=0.003). These findings demonstrate that stiffness can be tuned reliably using frequency-invariant process relationships, whereas damping requires frequency-aware parameter selection. This approach provides a statistically rigorous basis for optimizing additively manufactured components where both stiffness and energy dissipation are performance-critical.