Computation of Effective Permeability for Porous Carbon Composites

Abstract

Effective permeability of a porous carbon composite is computed using the direct simulation Monte Carlo technique. The microstructure of the carbon composite is synthetically generated using an in-house solver. Permeabilities obtained using synthetic microstructures of the precursor (carbon fibers) is compared to two independent experimental dataset and good agreement is observed. An approach to digitally infuse matrix into the precursor is proposed. Comparison of the permeability for the full composite (carbon fibers with matrix) with experimental data demonstrates good agreement indicating that representative microstructures generated digitally can be used to compute and predict effective permeability of porous carbon composites. Simulations of gases penetrating the full composite are performed, and an intrinsic material permeability (Ko) of 11.866 × 10−11 m2, and a Klinkenberg constant (b∗) of 5.655 × 10−8 that is only dependent on the temperature and the molecular weight of the gaseous species is obtained.

Microscale modeling of particle impact on TPS materials during high-speed entry

“…The FiberForm density and the full composite density (FiberForm + resin) is set to 180 and 210 / 3 , respectively, which results in a net porosity of ∼ 0.8. These values provide the best agreement with permeability measurements based on a previous study [34].…”

“…In the Fibergen code, the user can control the distribution of three-dimensional orientations, fiber diameters, bulk porosity, fiber density, and material density. Resin is infused into the sample through a stochastic approach [34]. In the manufacturing of the composite, the resin is infused into the microstructure of FiberForm which bonds to the carbon fibers in a random manner.…”

“…1b, red pixels represent the resin that is bonded to the underlying base structure of fibers, represented in black. The ability of Fibergen to reproduce material features and effective material properties (permeability and radiative coefficients) has been previously validated [7,34,36]. Additional details of the Fibergen code can be found in Refs.…”

“…The flow computations are performed using the the open-source DSMC solver, Stochastic Parallel Rarefied-gas Time-accurate Analyzer (Sparta) [48][49][50] with in-house enhancements [34]. Sparta uses a multi-level Cartesian mesh to track and collide particles.…”

“…In order to explore an aspect of the change in material properties, effective permeability is computed for the damaged microstructure and compared against the values for the virgin microstructure. This property is chosen because microscale flow computations of effective permeability has been validated against experimental data [33,34].…”