Date of Award

2024

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Materials Science and Engineering (PhD)

Administrative Home Department

Department of Materials Science and Engineering

Advisor 1

Gregory M. Odegard

Committee Member 1

Ravindra Pandey

Committee Member 2

Trisha Sain

Committee Member 3

Gowtham S

Abstract

One of the most difficult challenges associated with space exploration is terrestrial atmospheric reentry due to the high thermal loads generated. Carbon carbon (C/C) composites have been used as heat shielding materials due to their high strengthto- weight ratio and thermal properties and their applications include heat shielding for various high temperature environments. C/C composites are manufactured by polymer-infiltration pyrolysis (PIP) via cycles of curing and pyrolysis of a prepreg which can be costly and take up to several days. Thus, C/C composites ideal candidates for computationally-driven optimization techniques, such as a multiscale Integrated Computational Materials Engineering (ICME) approach, by optimizing processing parameters in silico and providing feedback to experimentalists. Because damage mechanisms of C/C composites involve multiple length scale, predictive computational models must be developed and validated from the nano to the meso length scales. This work presents novel atomistic modeling methods for polymerization and pyrolysis of a phenolic resin (PR) matrix using molecular dynamics (MD). PRs have been utilized as carbon matrix precursors since early C/C manufacturing efforts because of their high mass retention after pyrolysis. The MD protocols developed were validated by comparing various predicted properties to experimental literature reported for highly crosslinked PRs and glassy carbon (GC), then utilized to track the evolution of thermomechanical properties as a function of the degree of carbonization. An exponential-like trend was revealed for mechanical properties which showed significant increase towards the end stages of pyrolysis. Thermal conductivity initially decreased due to defective rings then increase again as six-membered carbon rings increased at the expense of defects. The effect of carbon fiber (CF) fillers on the PR microstructure at resin/fiber interfaces during polymerization and pyrolysis was investigated by via a “composite model” consisting of a mimicked CF surface and a PR matrix and applying the validated MD protocols. Templating of the resin onto the CF surface was observed after polymerization and considerably so after pyrolysis. This CF affected region showed more graphite-associated chemical and structural features compared to the rest of the resin, which showed chemical and structural metrics like those of a pyrolyzed neat PR.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

Available for download on Saturday, November 01, 2025

Share

COinS