Thermo-Oxidative Aging of Semi-crystalline Polyimide Films: Experimental Characterization and Predictive Modeling
ORAL
Abstract
This work investigates the effects of thermo-oxidative aging on the mechanical response and fracture behavior of Kapton films through a combined experimental and computational approach. Polyimide materials are recognized for their exceptional thermal stability and mechanical performance. Despite these advantages, polyimides’ exposure to prolonged thermal and oxidative environments leads to progressive material degradation that compromises their structural reliability. Understanding how these extreme environmental conditions influence polyimides’ failure behavior is essential for predicting their long-term performance. This work focuses on the development of a computational framework to capture aging-dependent degradation in polyimide films based on experimental characterization of the polymer network evolution.
Aging effects are introduced through degradation functions that reduce the bulk and shear moduli, as well as the fracture energy, in accordance with evolving physico-chemical properties. In particular, the degradation terms are formulated as functions of measurable metrics such as crystallinity ratio and chemical bond alterations, capturing key features of aging such as stiffness loss and embrittlement. The material under investigation is PMDA-ODA polyimide, commercially known as Kapton, which was aged in air at 300 °C for up to five weeks. At each weekly interval, specimens were tested to characterize the progressive effects of thermo-oxidative exposure. These tests include uniaxial tensile tests to assess mechanical degradation, single-edge notch tension tests to quantify fracture toughness, and chemical analyses using Raman spectroscopy and X-ray diffraction to monitor molecular changes such as oxygen uptake and crystallinity evolution. The resulting data informed the development and calibration of a computational model that combines viscoelastic constitutive behavior with a phase-field fracture framework. The model is validated against experimental observations and offers insights into the interplay between aging and fracture in high-performance polymers. Therefore, the proposed framework provides a predictive tool for understanding the long-term performance and failure of polyimide-based components in extreme environments.
Aging effects are introduced through degradation functions that reduce the bulk and shear moduli, as well as the fracture energy, in accordance with evolving physico-chemical properties. In particular, the degradation terms are formulated as functions of measurable metrics such as crystallinity ratio and chemical bond alterations, capturing key features of aging such as stiffness loss and embrittlement. The material under investigation is PMDA-ODA polyimide, commercially known as Kapton, which was aged in air at 300 °C for up to five weeks. At each weekly interval, specimens were tested to characterize the progressive effects of thermo-oxidative exposure. These tests include uniaxial tensile tests to assess mechanical degradation, single-edge notch tension tests to quantify fracture toughness, and chemical analyses using Raman spectroscopy and X-ray diffraction to monitor molecular changes such as oxygen uptake and crystallinity evolution. The resulting data informed the development and calibration of a computational model that combines viscoelastic constitutive behavior with a phase-field fracture framework. The model is validated against experimental observations and offers insights into the interplay between aging and fracture in high-performance polymers. Therefore, the proposed framework provides a predictive tool for understanding the long-term performance and failure of polyimide-based components in extreme environments.
*NSF CMMI-2245155
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Presenters
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Maryam Shakiba
- University of Colorado Boulder