Shear effects on expanded graphite under uniaxial pressure: An in situ small angle neutron scattering study

In a previous work [1] we elucidated the in situ evolution of the porosity of out-of-plane compressed flexible graphite under uniaxial pressure up to 1000 bar using small-angle neutron scattering (SANS) technique. In order to understand the influence of shear effect on the properties of flexible graphite we study, in the present paper, the in situ behaviour of in-plane compressed flexible graphite under a uniaxial pressure. The sample had a pleated layered structure in which anisotropic SANS patterns revealed a distribution of differently oriented ellipsoid pores. Uniaxial compression generates important shear effects in this kind of sample. e determined the evolution of the system fractal dimension, pore size distribution and apparent specific surface area with applied pressure which together allow us to describe the meso and macro pore structure evolution. Under pressure, the irreversible collapse and splitting of larger pores into smaller size ones which is characteristic of out-of-plane uniaxial compression [1], is accompanied, in the presence of shear stress components, by an in-plane slipping mechanism giving rise to cracks and consequently to interface formation.