Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Department of Aeronautics and Astronautics

First Advisor

Marina B. Ruggles-Wrenn, PhD.


The inelastic deformation behavior of PMR-15 neat resin, a high-temperature thermoset polymer, was investigated at temperatures in the 274-316°C range. The experimental program was developed to explore the influence of temperature on tensile loading, relaxation and creep behaviors of PMR-15. The results demonstrate that the mechanical behavior of PMR-15 exhibits a strong dependence on temperature. During strain-controlled tensile loading, the slope of the stress-strain curve in the quasi-elastic region decreases and the flow stress level decreases with increasing temperature. During relaxation, the amount of the stress drop decreases with increasing temperature. Based on experimental results the Viscoplasticity Based on Overstress for Polymers theory was augmented to account for the effects of elevated temperature. Several model parameters were developed into functions of temperature. The augmented VBOP was then employed to predict the response of the PMR-15 polymer under various test histories at temperatures in the 274-316°C range. Additionally, the effects of prior isothermal aging at various temperatures in the 260-316°C range were evaluated. At each temperature investigated, the initial slope of the stress-strain curve and the flow stress increase with prior aging duration. Experimental results reveal for aging temperatures in the 260-302°C range, mechanical behavior depends only on prior aging duration and not on prior aging temperature.

AFIT Designator


DTIC Accession Number