Résumé
In this work, we investigate cemented granular materials involving a dense particulate structure and a continuous matrix filling partially the interstitial space. The results were applied to the wheat endosperm modelled as an assembly of starch granules embedded in a protein matrix in view of better understanding of the origins of the wheat hardness (soft, hard and durum classes of wheat). The deformation and fracture of the particle and matrix phases and their interface were modelled by means of a lattice element approach. Three regimes of crack propagation were evidenced by a detailed parametric study in simple compression and tension. These regimes are characterized by particle damage as a func- tion of the matrix volume fraction and particle-matrix adhesion. The granular microstructure is shown to control the stress concentration, analyzed through the probability densities of the local stresses, and the rupture modes. The force transmission is found to compare well between the lattice element method and discrete element method. Simple compression tests were performed on samples of a cemented granular material in which the matrix volume fraction (cement) and particle-matrix adhesion (LECA beads coa- ted by silicone) were varied. The experimental results were in good agreement with numerical results. In both cases, we find that particle damage is controlled by the relative toughness of the particle-matrix interface combining the matrix volume fraction and particle-matrix adhesion. A simple theoretical model was elaborated taking into account the structural effects for the prediction of the elastic moduli in tension and compression, as well as the rupture thresholds. When compared to measured data concerning starch damage for different wheat varieties, our results suggest that the starch-protein adherence is dependent on the volume of puroindolines at the interface.