A Comparison of Bulk Density Measurement Techniques for Carbon-Carbon Composites (CCCs)

Author(s):

Jennifer M. Sietins, Ngon T. Tran, Faheem H. Muhammed, and Daniel B. Knorr Jr.

Abstract:

Bulk density, or the mass of a material divided by its total volume including internal voids and space, is a simple yet highly consequential characterization of carbon-carbon composites (CCCs). Because the performance of CCCs is strongly correlated to their density, and the manufacture of CCCs is relatively time-consuming and expensive, bulk density is routinely measured and its accuracy is important. Interestingly, multiple methods are used to determine bulk density, but the methods’ accuracy has not been thoroughly studied for carbon materials. This report discusses five common methods of determining bulk density on nine CCCs with the same 3-D architecture but different densities. These methods are geometric density, geopycnometry (GeoPyc), X-ray micro-computed tomography (xCT), mercury intrusion porosimetry (MIP), and Archimedes’ principle. We demonstrate that the Archimedes’ density tends to overestimate while geometric density tends to underestimate bulk density. In addition, GeoPyc and MIP yield similar density values to xCT, which may reflect the true bulk density of the materials tested.