Deformation Mechanisms in Polycrystalline Graphite

The microstructure of SGBF graphite was observed under tensile and compressive stresses. Increasing stress generated extensive cracking parallel to the layering direction in the particles. Such cracking, however, was not necessarily directly attributable to the low strength of the graphite crystallites in the c direction but rather to flaws or weak regions which tended to occur between the layer planes. For tensile stress, the cracks were perpendicular to the direction of the applied stress, whereas in compression, the cracking was parallel to the applied stress. Analysis of the stress‐strain relations for SGBF graphite in tension indicates a discrepancy with the previously proposed plastic deformation model. The discrepancy is attributed to the effect of the observed cracking on the internal stress distribution. An alternative explanation is proposed on the basis of internal stresses, localized cracking, and interlayer slip.