Effect of pore architecture on quasistatic compressive deformation of freeze-cast porous alumina scaffolds

We investigated the influence of various pore architectures namely lamellar, dendritic and isotropic on uniaxial compressive response of freeze-cast porous alumina (platelets) scaffolds at quasistatic strain rate (10⁻⁴ s⁻¹). The compressive response of the highly porous (>85 %) scaffolds exhibited cellular-like, damageable failure behaviour independent of pore structure. We suggest that high pore content (vis-à-vis less solid walls fraction) restricts the propagation of long, macroscopic cracks by crack-crack interaction along the lamella walls. This results in multiple fragments of the lamella walls by gradual crushing, a fundamental characteristic of cellular-like failure behaviour. Comparison of our experimental results with honeycomb out-of-plane deformation model derived by Gibson-Ashby further revealed that buckling induced elastic instability of the lamella walls is the strength (compressive) limiting mechanism. Microscopic observation showed extensive local damage of lamella walls (while the overall scaffolds remain intact at macroscopic level), which further confirms localized elastic instability (buckling) within lamella walls.