Compression and recovery micro-mechanisms in flexible graphite

Abstract

Utilization of synchrotron X-ray microtomography has enabled the virtual reconstruction of invisible microstructural units and their deformation during the compaction, compression and recovery of flexible graphite. Particles artificially affixed, in advance, to the surface of a given microstructural unit were connected by plane triangles to create a 3D mesh in the reconstruction. High density 3D mapping of strain and displacement has also been achieved, by tracing the physical displacement of the surface particles. Micro-mechanisms of compression and recovery behavior in flexible graphite have been examined involving the direct observations and measurements. The microstructural unit was found to be composed of thin expanded graphite discs with slightly misaligned basal planes of graphite. Highly localized deformation of a thin expanded graphite disc was observed during the compression and recovery processes, suggesting strong interaction with surrounding expanded graphite discs. The macroscopic compression behavior of flexible graphite is attributable to a combination of bending and thickness reduction/recovery of the discs. It has, however, been shown that only the thickness recovery of the individual discs, due to the presence of internal entrapped air, accounts for the macroscopic recovery behavior of flexible graphite.