Elastic properties of packing of granulated cork: Effect of particle size.

Cork is a natural raw materials used in numerous traditional and innovative applications among which the most famous are cork stoppers, insulation boards, and wall and floor covering. Cork exhibits a relatively homogeneous honeycomb structure composed of polyhedron cells filled with gas, which gives its specific properties such as elasticity or hydrophobic behavior. Mechanical properties of cork have been studied from a long time. However, in many industrial applications cork is increasingly used as granulate (>200 μm) or powder (<200 μm) obtained by milling processes. By generating failure in the raw material, the comminution of cork could damage cells and induce modifications in the mechanical behavior of cork particles but the relation between the size of the particles and the mechanical properties of the packaging is still little known. In this study, we investigate the effect of cork particles size reduction on the mechanical properties of the packing. To this end, eighteen discrete size fractions of cork from 0 to 25 μm to 2.5–3 mm, generated by impact milling were characterized in term of shape, loaded density, and elastic recovery. Experiments show that impact milling mainly affects the elastic properties of particles less than 200 μm. The mechanical behavior of cork particles was also described by model based on a mixing law taking in account the size and the shape of particles and the amount of damaged cells in the particles. The fitting of the model to the experimental data suggests that the elastic properties of the packing of cork particles have to be related to the content of damage cells more than to their size. [ABSTRACT FROM AUTHOR]