Accelerated Testing of Durability of Composite Materials and Structures

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The main focus of the program will be upon polymeric composite materials. The program is comprehensive, ranging from basic research to technology applications for industry. The technical foundation of the work is that of the time- temperature superposition methodology for polymers. With this methodology, elevated temperature states can be used to accelerate time flow events. When properly viewed on logarithmic scales the acceleration effect is nothing less than dramatic. The method has been available and widely used for many years to characterize nondestructive properties such as relaxation functions. In vitally important work of very recent times, the method has been proven to apply to the time based irreversible properties controlling failure in polymeric based materials. This breakthrough work and approach will be carefully exploited through evaluation and expansion in the present program. The basic research component of this program will involve developing a theory of crack kinetics. Inherent flaws in bulk polymers and at interfaces progresses through growth stages under load, ultimately becoming of critical size to cause failure. This avenue will be explored in great detail, along with full statistical aspects of the problem. The work will be posed in the temperature dependent state in order to incorporate the time-temperature shift methodology. Common empirical formulations of damage accumulation, such as Miner's `law`, will be evaluated.