Détermination des propriétés microstructurales et physiques d'un matériau fibreux cellulosique à partir de microtomographies aux rayons X

Cette étude concerne la détermination des propriétés microstructurales et physiques d'un matériau fibreux cellulosique à partir de microtomographies aux rayons X. Les propriétés microstructurales telles que la porosité, la surface spécifique et l'anisotropie du matériau sont mesurées à l'aide d'outils d'analyse d'image. Les propriétés physiques, telles que la perméabilité et la conductivité thermique effective, sont estimées numériquement en s'appuyant sur les résultats de l'homogénéisation périodique. Ces estimations numériques sont comparées à des mesures expérimentales. L'influence de la microstructure sur les propriétés physiques étudiées est discutée

Estimation of microstructural properties from synchrotron X-ray microtomography and determination of the REV size in paper materials

The porosity and specific surface areas of four industrial paper materials were determined from synchrotron X-ray microtomography. The porosity profile within the thickness of each paper material shows that a paper sheet consists of three layers: two boundary layers, which present a strong gradient of porosity, and a “bulk” layer in which the porosity is almost constant. The anisotropy and the heterogeneity scale of the microstructure in the “bulk” layer was then analyzed by means of covariograms. It is shown that the microstructure of the four studied papers is transverse isotropic and that the anisotropy of papers containing fillers is less pronounced. Finally, the representative elementary volume (REV) for both studied microstructural properties was evaluated using two techniques: a systematic analysis of the influence of the volume size on the property measurement, and a statistical methodology. The REVs given by both methodologies are then compared

Microstructural analysis of the bulk of a fibrous network based on synchrotron X-ray microtomography: numerical estimation of the permeability and effective thermal conductivity

International audienc

Microstructural analysis of paper using synchrotron X-ray microtomography: numerical estimation of the permeability and effective thermal conductivity

International audienceSynchrotron X-Ray microtomography has already been successfully applied to visualise the inner structure of various grades of papers at a micron scale. The image analysis tools, previously developed, can provide quantitative data characterising the microstructures of papers. We studied two widely different samples - a Eucalyptus pulp handsheet and a commercial blotting paper. Numerical calculations were carried out on the tomography data to evaluate two specific physical properties - effective thermal conductivity and permeability. The Representative Elementary Volume (REV) for each physical quantity considered, in terms of its 3 characteristic lengths in the three main directions, was defined by the respective correlation lengths (L-c). Despite the small imaged volume (1400 pm x 1400 pm x paper-thickness), for any given property, whether microstructural or physical -: The REV characteristic lengths were similar for both samples, The REV was smaller than the imaged volume, These results validate our approach and indicate that it may be extrapolated to other properties, for example, elastic properties