In-situ neutron diffraction measurement and numerical modelling of macro- and micro-strains in two porous synthetic graphites

Abstract

In-situ neutron diffraction measurements have been performed on IMI-24 grade (20% porosity) and PG25 (48% porosity) graphite subjected to external uni-axial compression loading. The ‘pore free’ matrix properties such as modulus of elasticity of about 72 GPa and 46 GPa were measured for the IMI-24 and PG25, respectively, and were higher than those measured at the macro-length-scale. The elastic modulus of each crystal plane, hkl, is reported ranging from about 48–145 GPa and Poisson ratio ranging from 0.08–0.28 for IMI-24 graphite. With the proposed method, the pore morphology factor ‘m’ was independently evaluated to be 10.8 and 4.8 for IMI-24 and PG25, respectively. It has been demonstrated from that the micro-diffraction the Young modulus is not dependent on the pore morphology factor. We consider and discuss the experimental plus modelling approach to provide a new perspective on the micro-mechanics of porous graphites.