Date of Award
2025
Document Type
Open Access Master's Thesis
Degree Name
Master of Science in Mechanical Engineering (MS)
Administrative Home Department
Department of Mechanical and Aerospace Engineering
Advisor 1
Trisha Sain
Committee Member 1
Chang Kyoung Choi
Committee Member 2
Stephen Morse
Abstract
Polymeric materials are widely used in engineering applications due to their high strength-to-weight ratio, easy manufacturability, and cost-effectiveness. When incorporated into composites, they provide further performance enhancements, enabling use in demanding structural applications. However, long-term exposure to harsh environments including elevated temperatures, UV radiation, harsh chemicals, and radiation, can drive degradation processes that alter the material’s network structure, and in turn, degrade its mechanical performance. Exposure to thermo-oxidative conditions is one of the most common environments driving polymer degradation, leading to chain scission and crosslinking events, with the resulting oxidative products causing discoloration, reduced ductility, and changes in glass transition behavior. Much of the existing literature has focused on reaction-limited oxidation in thin films. In contrast, bulk materials typically experience diffusion-limited oxidation, which produces steep gradients in chemical and mechanical properties across the cross-section. Recognizing these differences and their impact on mechanical behavior is critical for predicting the long-term performance of load-bearing applications.
This work presents a series of preliminary studies aimed at characterizing the effects of high-temperature oxidative aging in bulk polymers and polymer composites. Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, and mechanical testing were utilized to link physical and chemical changes with alterations in thermal and mechanical response. Three systems were examined: polypropylene with and without antioxidants, unidirectional glass fiber reinforced polymers with 0° and 90° fiber orientations, and carbon fiber reinforced polymers with varying fiber volume fractions. Results highlight the interaction between polymer microstructure, composite architecture, and oxidative mechanisms, providing insight into how local chemical degradation propagates to influence macroscopic material performance. Together, these findings establish a foundation for understanding long-term durability in structural polymer systems.
Recommended Citation
Jewell, Ben T., "DEGRADATION OF POLYMERS AND POLYMER COMPOSITES IN EXTREME ENVIRONMENTS", Open Access Master's Thesis, Michigan Technological University, 2025.