Nano-mechanical and chemical interrogation of vibrocreep in polymers

摘要

There is considerable evidence that the long-term response of polymers and polymer matrix composites subjected to cyclic loads, stress reversals, or variable cyclic temperatures is characterized by much higher creep rates than those observed from standard laboratory creep experiments. Historically, the understanding and modeling of the interactive mechanisms of creep and cyclic loading effects, defined as vibrocreep, have been inconclusive and present serious challenges. A study of vibrocreep has been initiated which is attempting to describe at the nanometer length scale the effect of the aforementioned factors on the chemical and nanomechanical properties of polymers. We describe the results of detailed analysis of specimens subjected to various loading and temperature histories using Raman spectroscopy and scanning electron and atomic force microscopies. The results show the level of nano-mechanical damage induced by the program loading histories. THese results will be incorporated into a finite element analysis to develop a first generation model for prediction of vibrocreep in polymers.