From Microtomography to Modeling of the Fiber-Scale Oxidation of Highly-Porous Carbon Materials

Speaker: Joseph Ferguson, University of Kentucky
July 31, 2014

Presentation

Abstract

Phenolic Impregnated Carbon Fiberform is used as the substrate for thermal protection materials for planetary entry systems. The surface of ablators decomposes via oxidation under hypersonic aerothermal conditions. The oxidation process is driven by two competing time-scales: the diffusion of reactants within the porous medium and the reaction rate at the surface of the fibers. A model to simulate this microscale process is developed and tailored to carbon preforms used by NASA to build lightweight carbon/phenolic ablators. The motion of oxygen reactants is simulated using a random walk technique to simulate diffusion, and sticking probability technique to simulate surface oxidation. To enable high fidelity simulations of the decomposition of the fibers, digitized computational grids are obtained from X-ray microtomography of the Fiberform, the substrate used in PICA. The model is applied to the tomographs in diffusion and reaction limited regimes to simulation the effects of surface and volume ablation.

Biography

Joseph Ferguson is an undergraduate student at the University of Kentucky, studying Mechanical Engineering and Computer Science. During his second year, he took part in university research modelling the atmospheric conditions during vehicle reentry. In 2013, he spent the spring semester working at the NASA Goddard Space Flight Center, assisting in software development for secure satellite communications. Joseph came to NASA Ames in January 2014 and is a developer for the PuMA (Porous Media Analysis) software.

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