Date of Award

3-10-2010

Document Type

Thesis

Degree Name

Master of Science in Aeronautical Engineering

Department

Department of Aeronautics and Astronautics

First Advisor

Marina B. Ruggles-Wrenn, PhD

Abstract

The purpose of this research was to investigate the inelastic deformation behavior of PMR-15 neat resin, a high-temperature polymer, at 260 °C. The experimental program was designed to explore the influence of strain rate on loading and unloading behaviors. In addition, the effect of prior strain rate on creep, relaxation, and recovery responses was evaluated. The material exhibits positive, nonlinear strain rate sensitivity in monotonic loading. Early failures occur before fully establishing inelastic flow. The creep, relaxation, and recovery responses are significantly influenced by prior strain rate. The experimental results suggest the behavior of PMR-15 at 260 °C can be effectively modeled using a unified constitutive model with an overstress dependence of inelastic rate deformation. The experimental data were modeled using the Viscoplasticity Based on Overstress for Polymers (VBOP) theory. The lack of data in the inelastic region inhibited the application of the VBOP. The deformation behavior of PMR-15 at 260 °C was modeled well despite this lack of data. The effects of prior aging in argon at 260 °C on the time (rate)-dependent behavior of the PMR-15 polymer were evaluated in a series of strain controlled experiments. Several of the VBO material parameters were expanded as functions of prior aging time. The resulting model was used to predict the behavior of PMR-15 subjected to various prior aging durations.

AFIT Designator

AFIT-GAE-ENY-10-M08

DTIC Accession Number

ADA517402

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