Bioinspired hierarchical porous ceramics via cryogenic 3D printing: superior energy absorption and strain-rate dependent failure mechanisms

The inherent brittleness of conventional ceramics limits their energy dissipation capability under dynamic loading, posing challenges for impact-resistant applications. Inspired by biological multilevel architectures, multilevel porous alumina ceramics were fabricated using a hybrid cryogenic–additive manufacturing approach. Dynamic impact tests at high strain rates (up to 2000 s⁻¹) revealed a pronounced stress plateau and significantly enhanced energy absorption behavior. Compared with freeze-cast specimens, the cryogenic 3D-printed ceramics exhibited a substantial increase in plateau stress (up to 355%), together with enhanced damage tolerance, achieving a low density of 0.526 g/cm³and an energy absorption density of 2.63 MJ/m³through a stable progressive collapse mode. Numerical simulations were employed to elucidate the associated damage evolution and energy absorption mechanisms. These results demonstrate the potential of multilevel porous alumina ceramics for lightweight, high-performance impact-resistant structural applications.