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A phase field model for thermo‐oxidative aging in cracked polymers
Author(s) -
Voges Jannik,
Juhre Daniel
Publication year - 2019
Publication title -
pamm
Language(s) - English
Resource type - Journals
ISSN - 1617-7061
DOI - 10.1002/pamm.201900384
Subject(s) - work (physics) , diffusion , phase (matter) , materials science , field (mathematics) , polymer , process (computing) , term (time) , computer science , oxygen , surface energy , energy (signal processing) , redox , current (fluid) , phase field models , interface (matter) , mechanics , mechanical engineering , composite material , thermodynamics , chemistry , metallurgy , physics , engineering , mathematics , organic chemistry , quantum mechanics , capillary number , capillary action , pure mathematics , operating system
When dealing with polymers, the behavior of aging processes is of great interest in many applications in engineering, as the usually very complex mechanisms can result in a drastic reduction of the lifetime of machine parts. In addition, those single mechanisms are coupled, which results in even more complexity. A crack creates new surfaces deeper inside the material and thus enables oxidation processes beyond the original surface. Once being oxidized, the crack resistance might be reduced, which may result in further crack propagation, which, again, enables oxidation even deeper. In the present work, a new approach for diffusion limited oxidation is introduced. The approach is based on the phase field method, which has become an important and versatile tool to model different phase evolutions in materials. An evolution equation is underlain by a gradient energy term to capture an interface energy and by a second term, which corresponds to the phase change representing the oxidation state. A diffusion equation controls the amount of available oxygen which is able to trigger the phase change. The phase change, in turn, drains a specific amount of oxygen in the coupled system of differential equations. In this work, cracks are able to expedite the oxidation process deeper into the specimen. The model has been implemented into the FE code FEAP and investigated by means of two academic examples.