Molecular, Microscopic and Macroscopic Investigation of Fracture in Polymer and Composites

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The goal of this research is to explore the macroscopic, microscopic, and molecular aspect of fracture in polymers and polymeric matrix composites. Particular emphasis will be placed on defining the synergistic effects of stress and aggressive environmental agents on mechanical properties of highly oriented, ultra high strength polymeric fibers. The bond rupture events will be monitored with Electron Spin Resonance (ESR) technique during the fiber tensile tests. These experiments will provide information on molecular changes resulting from stress/ageing, the number of chains that need to be broken to accomplish final failure, and insight into the molecular mechanisms active during sample failure. The ESR technique will also be used to study failure of fiber composites. The ESR spectra will yield information on the stress distribution and its relation to the failure of fibers in the composite.