Owing to their high strength-to-weight ratio, carbon fiber (CF) has been used as a steel replacement for improved fuel efficiency in the aeronautical and automotive industries. Experiments report appreciable concentrations of hydrogen in both sized and unsized commercial CF, indicating the presence of hydrogen in the CF matrix and not solely in the protective polymeric coating. As a consumer product, understanding the influence of hydrogen defects on the mechanical properties of CF and how the formation and evolution of these defects can be monitored noninvasively is important. Spectroscopic techniques, such as Raman spectroscopy, can be readily used for this purpose, and complementary computational studies can provide a deeper understanding of the spectral signatures and influence of defects in CF failure. In this work, we used density functional theory to investigate the stability and spectral response of a variety of hydrogen defects in CF. Using graphite as a CF surrogate, we investigated changes to the phonons induced by hydrogen substitution and intercalation at multiple defect concentrations and interdefect distances. This information contributes to a more complete understanding of the observable spectral changes induced by hydrogen defects in CF and the consequences for material strength.

Investigation of hydrogen-induced phonon changes in graphite using density functional theory

ACS Spring Meeting 2021

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