Fracture of nanoceramics with porous structure at shock wave loadings

Computer simulation techniques are used to investigate the deformation and damage processes taking place in brittle oxide nanostructured ceramics under intense dynamic loading. The pore structure is shown to substantially affect the size of the fragments and the strength of the ceramics. In porous nanostructured ceramics subjected to shock loading, deformation is localized in mesoscopic bands having characteristic orientations along, across, and at ~ 45° to the direction of propagation of the shock wave front. Clusters of nanopores cause the decreasing of the shear strength of nanostructured ceramics. The localized deformation bands may be transformed into mesoscopic cracks. A method is proposed for a theoretical estimation of the effective elastic moduli of ceramics with pore structure without resorting to well-known hypotheses for the relation between elastic moduli and porosity of the materials.