Abstract
Additive manufacturing (AM) using fused filament fabrication (FFF) offers a responsive solution to maritime supply chain delays through on-demand, shipboard component fabrication. However, the operational reliability of non-structural polylactic acid (PLA) assets over extended lifecycles remains critical. This paper investigates the 6-month atmospheric degradation behavior of FFF-printed PLA components across varying infill densities (33%, 66%, and 100%). Utilizing non-destructive parallel-plate dielectric spectroscopy across an alternating current spectrum (1 kHz to 20 kHz), experimental results reveal that the decay in the relative dielectric constant (εr) is most prominent at the 1 kHz window—dropping from 3.70 to 3.63 for solid structures. At higher frequencies (10–20 kHz), this aging signature is heavily attenuated due to polymer dipole immobilization, causing the dielectric response to converge toward a baseline polarization value. To map these state transitions, a multi-variable surface linear regression framework with an ordinary least squares metric was implemented. The bilinear model successfully captures the coupled density–frequency interaction, achieving a Coefficient of Determination (R2) of 0.8619 and a Root Mean Square Error (RMSE) of 0.00199 month−1, providing a quantitative screening tool for decentralized maritime digital inventories.