Bioinspired ceramic-polymer composites with hierarchical nacre-mimetic structure via accumulative rolling technique

Abstract

Constructing nacre-mimetic architecture in ceramic-polymer composites is an effective approach to improve fracture toughness. Here, ceramic-polymer composites with nacre-mimetic brick-and-mortar structure were fabricated using an accumulative rolling technique. Non-isometric and flaky Ti3AlC2 powders with ultrafine dimensions along with Al2O3 and h-BN powders with micron-sized dimensions were employed as constituents and the effect of their size on mechanical properties was investigated. The results showed that the flaky ceramic powders were preferentially aligned along the rolling direction under the shear force exerted by the rollers, and formed staggered stacking layers. Significant differences in the characteristic dimensions of flaky ceramic powders contributed to a hierarchical structure of the composites. Compared with the composites containing merely ultrafine-sized Ti3AlC2 flakes, the strength of composites decreased when Ti3AlC2 flakes were replaced by larger Al2O3 and h-BN flakes. However, such substitution inhibited the crack propagation, leading to a stable crack growth behavior featured by rising R-curves owing to the activation of various extrinsic toughening mechanisms, including crack deflection, uncracked-ligament bridging and pull-out of ceramic platelets. The accumulative rolling technique offers a simple but effective means for toughening ceramic materials and optimizing their functional properties along specific directions.