Prediction of the Degradation of Composite Materials for Emerging Army Facilities

An innovative methodology, based on mechanistic models, will be developed for prediction of long-term (25+ years) durability of composites for the US Army's emerging facilities in different climatic zones. Accelerated testing simulating the Army's composites applications in various constructions and fields will validate it. Phase I developed the basic predictive tool using the Arrehenius principles adapted to the TTS (Time Temperature Superposition) and measuring degradation of carbon fiber epoxy composite under simultaneous UV (Ultra Violet) and hygrothermal exposure. The test captured the synergistic effects of field exposure and extreme temperatures, viz., hot/dry, hot/wet, cold/dry, and cold/wet. The capacity loss from changes at the molecular level, such as hydrolysis, microcracks, and UV induced polymer chain-scission, are to be incorporated in the model using a unique finite-element (FE) based multi-scale, multi-mechanism degradation model that was developed at the University of Alabama, Tuscaloosa. Phase II will refine the model to include additional chemical degradation mechanisms, relaxation and creep threshold, stress induced crack growth in fibers and fiber/matrix debond, and effects of blast and seismic events. The model will make prediction of service performance and remaining life and will be incorporated in a user-friendly Field Usable Design Tool software, to be commercialized in Phase III