Panoramic View of Interface-Related Thermo-oxidative Aging of Carbon Fiber-Reinforced Epoxy Composites

The thermo-oxidative aging mechanism of carbon fiber-reinforced epoxy (CF/EP) composites was studied by using reactive molecular dynamics (RMD) simulations with a reactive force field (ReaxFF), traditional molecular dynamics (MD) simulation, and machine learning (ML) methods. The decoupling of the tensile stress applied to the resin from the thermo-oxidative aging reactions in the resin was demonstrated. The tensile strength parallel to the fiber was much higher than that perpendicular to the fiber. The fiber–epoxy interfacial bonding interaction limits the thermal mobility of the resin near the interface, lowering the probability of aging reaction events and thereby prohibiting the material’s aging. The panoramic view of the aging reactions was obtained using a new holistic analysis approach, revealing the high breaking probability of hydroxyl groups, ether bonds, and C–N bonds in the resin skeleton. These chemical bonds were proven to affect the formation of the main products. The total number of chemical bonds in the material was linear with the ultimate tensile strength perpendicular to the fiber. By establishing the relationship between “products–chemical bonds–mechanical properties”, we built the groundwork for novel lifetime prediction model construction based on theoretical and data fusion methods.