Probabilistic Aging Assessment of Aerospace Bakelite Materials via Integrated Chemical, Thermal, Mechanical and Microstructural Characterization

This study investigates the aging behavior and probabilistic age assessment of phenolic resin-based Bakelite materials used in aerospace electrical insulation systems. Six Bakelite samples obtained from aircraft electrical components were analyzed using an integrated multi-parameter characterization approach combining Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Shore D hardness measurements, Gas Chromatography–Mass Spectrometry (GC-MS), and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS). The results revealed progressive thermo-oxidative degradation characterized by carbonyl formation, reduction of hydroxyl and methylene bridge structures, depletion of volatile organic compounds, thermal instability, hardness reduction, oxygen enrichment, and microstructural deterioration. The combined results revealed progressive thermo-oxidative degradation associated with oxidation-induced chemical changes, reduced thermal stability, volatile depletion, and microstructural deterioration. To quantitatively interpret the multidimensional experimental data, a Bayesian probabilistic model was developed using three age hypotheses (0–20, 20–40, and 40–60 years). The model produced posterior probabilities of 5.2%, 19.3%, and 75.5%, respectively, indicating that the investigated materials most likely belong to the 40–60 year aging range. The originality of this study lies in integrating chemical, thermal, mechanical, and microstructural characterization within a Bayesian aging assessment framework for aerospace-grade Bakelite materials.